JP7378066B2 - Heat ray absorbing material and its manufacturing method, heat ray absorbing film - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Published on pages 11-12 and 119 of the Abstracts of the 26th Annual Conference of the Cellulose Society, published on July 1, 2020 July 11, 2020, Presented at the 26th Annual Conference of the Cellulose Society on the 12th Presented at the Nanocellulose Forum Open Seminar on October 16, 2021 Presented at the Technical Information Association Technical Seminar on November 14, 2021

The present invention relates to a heat ray absorbing material capable of absorbing heat rays, a method for producing the heat ray absorbing material, and a heat ray absorbing film containing the heat ray absorbing material.

Approximately 40% of sunlight is in the infrared wavelength range or higher, and is called heat ray because it has a high thermal effect. Window materials that require transparency in office buildings, automobiles, etc. transmit heat rays well, so the problem is that the temperature inside the room or office increases. Therefore, in order to save energy, it is being considered to give window materials the ability to reflect or absorb heat rays (infrared rays and above). As a means of imparting the function of reflecting or absorbing heat rays (heat ray shielding property) to the window material, for example, coating tin-doped indium oxide (ITO) fine particles, antimony-doped tin oxide (ATO) fine particles, cesium tungstic acid, etc. A method has been proposed in which an infrared absorbing film is attached to window glass.

Japanese Patent Application Publication No. 2018-116069

Antimony and cesium are substances that are unsuitable for the environment, and indium is a rare metal and therefore expensive, and alternative materials for both are desperately needed. In addition, in order to improve heat shielding properties, increasing the amount of inorganic fine particles added to lower the solar transmittance will lower the visible light transmittance, and conversely, increasing the visible light transmittance to let in outside light will reduce the solar transmittance. There is a problem that solar transmittance increases and heat ray shielding properties decrease.

The present invention has been proposed in view of the above-mentioned problems related to the conventional technology, and has been proposed to suitably solve these problems. It is an object of the present invention to provide a method for producing a heat ray absorbing material, and to provide a heat ray absorbing film using the heat ray absorbing material.

化学式１に示すＲ^１～Ｒ^６は、それぞれ独立に水素原子、スルホン酸基または炭素鎖数１～６のアルキルスルホン酸基を表し、かつ、Ｒ^１～Ｒ^６の少なくとも１つはスルホン酸基または炭素鎖数１～６のアルキルスルホン酸基である。また、化学式１のｎは、括弧内の繰り返しを示す。 In order to overcome the above problems and achieve the intended purpose, the heat ray absorbing material according to the present invention has the following features:
Sulfated cellulose nanocrystals shown in the following chemical formula 1 obtained from fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm,
The gist is that the sulfated cellulose nanocrystals include doped polythiophene.

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses.

化学式１に示すＲ^１～Ｒ^６は、それぞれ独立に水素原子、スルホン酸基または炭素鎖数１～６のアルキルスルホン酸基を表し、かつ、Ｒ^１～Ｒ^６の少なくとも１つはスルホン酸基または炭素鎖数１～６のアルキルスルホン酸基である。また、化学式１のｎは、括弧内の繰り返しを示す。 In order to overcome the above problems and achieve the intended purpose, the method for manufacturing a heat ray absorbing material according to the present invention includes:
The hydroxyl group of fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm is replaced with a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains, and the above-mentioned process is performed until the resulting sulfated cellulose becomes nanocrystalline. By introducing a sulfonic acid group or the alkyl sulfonic acid group, sulfated cellulose nanocrystals shown in the following chemical formula 1 are obtained,
The gist is that the thiophene is polymerized in the coexistence of the sulfated cellulose nanocrystals and thiophene to produce polythiophene, and the polythiophene is doped with the sulfated cellulose nanocrystals.

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses.

In order to overcome the above problems and achieve the intended purpose, the heat ray absorbing film according to the present invention has the following features:
The gist is to include the heat ray absorbing material according to the present invention.

According to the heat ray absorbing material according to the present invention, since rare materials are not used, costs can be reduced and the load on the environment can be reduced.
According to the method for manufacturing a heat ray absorbing material according to the present invention, a heat ray absorbing material with low environmental impact can be obtained at low cost without using rare materials.
According to the heat ray absorbing film according to the present invention, since rare materials are not used for the heat ray absorbing material, the cost of the heat ray absorbing material can be suppressed, and the load on the environment due to the heat ray absorbing material can be reduced.

FIG. 1 is a schematic diagram showing a PEDOT/CS composite that is an example of a heat ray absorbing material according to the present disclosure. FIG. 2 is a schematic diagram showing a manufacturing process of a PEDOT/CS composite, which is an example of a heat ray absorbing material according to the present disclosure. It is a graph diagram showing the transmittance of a heat ray absorption film. FIG. 2 is an explanatory diagram showing an apparatus for measuring the heat shielding properties of a heat ray absorbing film. FIG. 2 is a graph diagram showing the heat shielding properties of a heat ray absorbing film. 3 is a graph diagram showing the results of Test 1. FIG. FIG. 2 is a graph diagram showing the results of Test 2. 3 is a graph diagram showing the results of Test 3. FIG. FIG. 2 is a graph diagram showing the relationship between optical properties and conductivity.

(heat ray absorbing material)
The heat ray absorbing material according to the present invention includes sulfated cellulose nanocrystals and polythiophene doped with the sulfated cellulose nanocrystals. The heat ray absorbing material can also be said to be a composite of sulfated cellulose nanocrystals (CS) and polythiophene (PT) (hereinafter sometimes abbreviated as PT/CS composite). Here, the sulfated cellulose nanocrystal of the heat ray absorbing material is represented by the following chemical formula 1. The heat ray absorbing material is composed of sulfated cellulose nanocrystals as a skeleton, and polythiophene is oriented on the surface of the sulfated cellulose nanocrystals. The heat ray absorbing material according to the present disclosure has low absorption of visible light, high absorption of near infrared rays, and transparency, and has properties required as a heat ray absorbing material. The heat ray absorbing material has hydrophilicity and can be dispersed in water. Heat ray absorbing materials are easy to coat and can provide high electrical conductivity. Furthermore, the heat ray absorbing material has a function of improving the mechanical strength of the film when it is blended with a polymer to form a heat ray absorbing film. The heat ray absorbing material according to the present invention does not contain substances unsuitable for the environment such as antimony or cesium, so it has a low burden on the environment, and it does not use rare metals such as indium, so it can be obtained at low cost.

化学式１に示すＲ^１～Ｒ^６は、それぞれ独立に水素原子、スルホン酸基または炭素鎖数１～６のアルキルスルホン酸基を表し、かつ、Ｒ^１～Ｒ^６の少なくとも１つはスルホン酸基または炭素鎖数１～６のアルキルスルホン酸基である。また、化学式１のｎは、括弧内の繰り返しを示す。

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses.

As shown in FIG. 1, the heat ray absorbing material is, for example, sulfated cellulose nano in which R ¹ , R ² , R ⁴ and R ⁵ of chemical formula 1 are hydrogen atoms and R ³ and R ⁶ are sulfonic acid groups A specific example is a composite of crystal (CS) and poly(3,4-ethylenedioxythiophene), also abbreviated as PEDOT (hereinafter sometimes referred to as PEDOT/CS composite). . The heat ray absorbing material shown in FIG. 1 can be manufactured, for example, by the procedure shown in FIG. 2.

(Size of heat ray absorbing material)
The heat ray absorbing material is a nano-sized material in which the fiber length derived from sulfated cellulose nanocrystals is in the range of, for example, 50 nm to 400 nm, and the fiber width derived from the sulfated cellulose nanocrystals is in the range, for example, from 1 to 10 nm. can be formed with. As described above, since the heat ray absorbing material is nano-sized, it can be added to various materials such as polymers as an additive that imparts heat ray absorption properties. Since the heat ray absorbing material is nano-dispersed in a polymer or solvent without agglomerating, it can improve visible light transmittance.

(Light ray absorption characteristics of heat ray absorbing material)
The heat ray absorbing material according to the present invention absorbs heat rays (infrared rays) and preferably blocks the transmission of heat rays, and among heat rays (infrared rays), the absorption property is particularly large in the near-infrared region of 800 nm to 1500 nm, and in the 800 nm Absorption characteristics in the shorter visible light range are small. Therefore, heat ray absorbing materials have excellent transparency, and even when heat ray absorbing materials are added to polymers, they do not impair the transparency of the object and can ensure brightness by transmitting visible light. , heat rays can be significantly cut.

When the amount of near-infrared light with a wavelength of 800 nm is taken as 100, the heat ray absorbing material can reduce the amount of transmitted near-infrared light to 50% or less, and the amount of visible light with a wavelength of 500 nm can be reduced to 100. In this case, it is possible to maintain the transmitted visible light at 70% or more. For the heat ray absorbing material, the relationship between the transmittance of visible light and the absorbance of near-infrared light is set so that when the maximum absorbance of visible light is 0, the minimum absorbance of near-infrared light is 0.1 or more. It is preferable to do so.

(Crystallinity of sulfated cellulose nanocrystals in heat ray absorbing material)
In the heat ray absorbing material, the cellulose I type crystallinity of the sulfated cellulose nanocrystals represented by Chemical Formula 1 is preferably in the range of 20% to 53%. When the cellulose I type crystallinity is 53% or less, the absolute amount of the sulfonic acid group or the alkyl sulfonic acid group having 1 to 6 carbon chains as a dopant can be ensured, and the heat ray absorbing material obtained can be Absorption properties can be improved. Further, when the cellulose I type crystallinity is 20% or more, it is possible to suppress disorder of cellulose molecular chains. This makes it possible to align the orientation of thiophene during polymerization to obtain polythiophene, prevent disorder of the crystal lattice of polythiophene, and improve the heat ray absorption properties of the obtained heat ray absorbing material. Therefore, when considering the amount of dopant and the crystallinity of cellulose, it is considered that a suitable range for cellulose type I crystallinity is 20% to 53%.

(Method for measuring crystallinity of sulfated cellulose nanocrystals)
In the present disclosure, using an X-ray diffraction (XRD) device, from the measurement results of I ₂₀₀ : diffraction intensity of the lattice plane (200 plane) and I _am : diffraction intensity of the amorphous part, using the following formula 1, sulfuric acid The degree of crystallinity of cellulose nanocrystals is calculated.
Cellulose type I crystallinity (%) = [(I ₂₀₀ - I _am )/I ₂₀₀ ] x 100...Formula 1
Here, I ₂₀₀ indicates the X-ray diffraction intensity at 2θ=22.6°, and I _am indicates the X-ray diffraction intensity at 2θ=18.5°.

(Ratio of sulfated cellulose nanocrystals and polythiophene in heat ray absorbing material)
In the heat ray absorbing material, the ratio of polythiophene to sulfated cellulose nanocrystals is not particularly limited. In a heat ray absorbing material, the higher the proportion of polythiophene, the higher the heat ray absorption properties, but the dispersibility tends to decrease when the heat ray absorbing material is added to a compounding target such as a solvent or polymer. Taking these into consideration, the ratio of sulfated cellulose nanocrystals to polythiophene may be appropriately set in the heat ray absorbing material depending on the type of polythiophene or sulfated cellulose. Specifically, the mass ratio of polythiophene and sulfated cellulose nanocrystals is 1:0.5 to 1:8, preferably 1:1 to 1:4, and more preferably 1:1. good. By satisfying such a mass ratio, it is possible to have better heat ray absorption characteristics and to have good dispersibility in solvents and the like.

(Sulfated cellulose nanocrystals)
Sulfated cellulose nanocrystals are made by introducing sulfonic acid groups or alkylsulfonic acid groups having 1 to 6 carbon chains into fibrous cellulose (hereinafter also referred to as cellulose nanofibers). Sulfated cellulose nanocrystals can be represented by the following chemical formula 1. In the following explanation, a sulfonic acid group and an alkylsulfonic acid group having 1 to 6 carbon chains may be abbreviated as a sulfonic acid group, etc.

化学式１に示すＲ^１～Ｒ^６は、それぞれ独立に水素原子、スルホン酸基または炭素鎖数１～６のアルキルスルホン酸基を表し、かつ、Ｒ^１～Ｒ^６の少なくとも１つはスルホン酸基または炭素鎖数１～６のアルキルスルホン酸基である。また、化学式１のｎは、括弧内の繰り返しを示す。

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses.

(Size of sulfated cellulose nanocrystals)
Cellulose nanocrystals in sulfated cellulose nanocrystals refers to a state in which hydrogen bonds occur and crystals are formed by forming nanofabrils, and in this disclosure, cellulose nanocrystals are formed by sulfating fibrous cellulose. The situation is as follows. The sulfated cellulose nanocrystals have a fiber width in the range of 1 nm to 10 nm, and a fiber length in the range of 50 nm to 400 nm. In other words, sulfated cellulose nanocrystals are obtained by controlling the sulfation of fibrous cellulose so that the fiber width and fiber length fall within the above ranges. With such sulfated cellulose nanocrystals, when polythiophene is polymerized by coexisting sulfated cellulose nanocrystals and thiophene, the orientation of thiophene on the sulfated cellulose nanocrystals can be aligned. Thereby, the polythiophene formed on the sulfated cellulose nanocrystals can be appropriately connected, and the heat ray absorption properties of the obtained heat ray absorbing material can be improved. The fiber width of the sulfated cellulose nanocrystals is preferably in the range of 2.8 nm to 8.0 nm. When the fiber width of the sulfated cellulose nanocrystals is in the range of 2.8 nm to 8.0 nm, the heat ray absorption properties of the obtained heat ray absorbing material can be further improved.

(Crystallinity of sulfated cellulose nanocrystals)
The crystallinity of the sulfated cellulose nanocrystals is preferably in the range of 20 to 53, more preferably in the range of 27 to 53. In other words, sulfated cellulose nanocrystals are obtained by controlling the sulfation of fibrous cellulose so that the degree of crystallinity falls within the above range. With such sulfated cellulose nanocrystals, when polythiophene is polymerized by coexisting sulfated cellulose nanocrystals and thiophene, the orientation of thiophene on the sulfated cellulose nanocrystals can be aligned. Thereby, the polythiophene formed on the sulfated cellulose nanocrystals can be appropriately connected, and the heat ray absorption properties of the obtained heat ray absorbing material can be improved.

Cellulose fibers having a fiber width of 3 nm to 1500 nm and a cellulose fiber length of 200 nm to 10,000 nm are generally called cellulose nanofibers. That is, the fibrous cellulose used in the present disclosure can be called cellulose nanofibers. The crystallinity of fibrous cellulose (cellulose nanofibers) is in the range of 60 to 70, which is higher than that of sulfated cellulose nanocrystals. When fibrous cellulose is more nanofabrillated than cellulose nanocrystalline, the fiber width is in the range of 1 nm to 10 nm, the fiber length is in the range of 10 nm to 300 nm, and the crystallinity is more than 20. It becomes amorphous and becomes smaller. By using cellulose nanocrystals as the heat ray absorbing material, the heat ray absorption properties are significantly improved compared to using cellulose nanofibers or amorphous cellulose.

(fibrous cellulose)
As the fibrous cellulose, for example, those derived from polysaccharides contained in natural plants such as wood fibers such as coniferous and broad-leaved trees, bamboo fibers, sugarcane fibers, seed hair fibers, and leaf fibers can be used. Further, as the fibrous cellulose, those derived from polysaccharides contained in marine organisms such as ascidians and seaweeds, or those derived from polysaccharides produced by acetic acid bacteria using sugars as raw materials, etc. can be used. The fibrous cellulose may be used alone or in combination of two or more types derived from different materials.

As the fibrous cellulose, it is preferable to use pulp having an α-cellulose content in the range of 60% by mass to 99% by mass. When the α-cellulose content of fibrous cellulose is in the range of 60% by mass or more, the properties of cellulose such as high strength, heat resistance, high rigidity, high heat shock resistance, and high oxygen barrier properties can be fully brought out. In addition, problems such as quality deterioration due to coloring and gas generation due to heat can be avoided. Further, when the α-cellulose content of the fibrous cellulose is in the range of 99% or less, it becomes easy to break down the bonds between the fibers due to hydrogen bonds and obtain nano-level fibrous cellulose.

(Size of fibrous cellulose)
The fibrous cellulose preferably has a fiber width in the range of 3 nm to 1500 nm. When the fiber width of the fibrous cellulose is in the range of 3 nm to 1500 nm, when a sulfonic acid group or an alkyl sulfonic acid group having 1 to 6 carbon chains is introduced into the fibrous cellulose (hereinafter referred to as sulfation), a moderate amount of Sulfated cellulose nanocrystals having crystallinity can be obtained. In addition, when the fiber width of the fibrous cellulose is 3 nm or more, it is possible to increase the amount of fibrous cellulose that exists as crystalline fibers without being completely dissolved into molecules. Furthermore, when the fiber width of the fibrous cellulose is within the range of 1500 nm or less, it becomes easier to uniformly introduce sulfonic acid groups and the like into the fibrous cellulose.

The fiber length of the fibrous cellulose is preferably in the range of 200 nm to 10,000 nm, more preferably in the range of 500 nm to 2,000 nm. When the fiber length of the fibrous cellulose is 200 nm or more, it is possible to suppress the crystallinity from immediately decreasing when the fibrous cellulose is sulfated, and when the fiber length of the fibrous cellulose is 10,000 nm or less, It can be made to exist as long fibers that are difficult to curl into a cocoon-like shape, and it becomes easier to uniformly introduce sulfonic acid groups or alkyl sulfonic acid groups having 1 to 6 carbon chains into the fibrous cellulose.

When fibrous cellulose is uniformly sulfated (sulfonic acid groups, etc. are uniformly introduced into sulfated cellulose nanocrystals), the orientation of polythiophene in the heat ray absorbing material is aligned, and suitable heat ray absorption properties are obtained. . Moreover, it becomes easy to prepare the heat ray absorbing material as a uniform sheet-like film.

The fiber width and fiber length of the heat ray absorbing material, sulfated cellulose nanocrystals, and fibrous cellulose are measured using an electron microscope as follows. An aqueous suspension of the measurement target such as fibrous cellulose with a concentration of 0.001% by mass to 0.01% by mass is prepared, and the suspension is cast onto a hydrophilic carbon membrane-coated grid to allow permeation. This is used as an observation sample for an electron microscope (TEM). Then, by observing the sample using an electron microscope, the fiber width and fiber length of the measurement target are measured. In addition, when wide fibers are included, the suspension is cast on glass to prepare an observation sample for a scanning electron microscope (SEM), and the sample is observed using a scanning electron microscope. Then, the fiber width and fiber length of the object to be measured may be measured.

(Structure of fibrous cellulose)
Fibrous cellulose can be represented by the structural formula shown in Chemical Formula 2 below. As shown in Chemical Formula 2, fibrous cellulose has six hydroxyl groups in the cellobiose unit. The fibrous cellulose is preferably one in which the structure of cellulose molecules does not change from the original natural cellulose. Fibrous cellulose without such changes in molecular structure can be obtained, for example, by nano-refining so as to cleave only the interaction between natural cellulose fibers. Note that n in Chemical Formula 2 indicates repetition within parentheses.

(Method for producing fibrous cellulose)
As a method of defibrating natural cellulose to obtain fibrous cellulose adjusted to an appropriate size, for example, polysaccharides are defibrated in a high-pressure water stream, such as in water as described in JP-A No. 2005-270891. The opposing collision method (sometimes referred to as the ACC method) is preferred. The underwater counter-impingement method is a method in which natural cellulose fibers suspended in water are introduced into two nozzles facing each other in a chamber, and the natural cellulose fibers are injected from these nozzles toward a single point to cause the natural cellulose fibers to collide. According to the underwater facing collision method, natural microcrystalline cellulose fibers (e.g., Funacel) are subjected to facing collisions in suspended water to form nanofibrillation on the surface and peel it off, thereby improving its affinity with water as a carrier. , it is possible to finally reach a state close to dissolution.

The device used for the underwater counter-impingement method is a liquid circulation type equipped with a tank, a plunger, two opposing nozzles, and a heat exchanger if necessary. Colliding particles in opposite directions in water. It is then cooled by a heat exchanger and returned to the tank. In this way, in the underwater facing collision method, one treatment number (pass) is a circulation cycle in which the suspension goes through the tank, plunger, chamber, and heat exchanger in this order, and by changing the number of treatments, fibrous cellulose It is possible to increase or decrease the fiber width and/or fiber length as appropriate. For example, by increasing the number of treatments, the fiber width of fibrous cellulose can be reduced. Further, for example, by reducing the number of times of the treatment, the fiber width of the fibrous cellulose can be increased. The underwater facing collision method can control the average fiber width, average fiber length, permeability, viscosity, degree of polymerization, etc. of the resulting fibrous cellulose by adjusting treatment conditions such as treatment pressure, number of treatments, nozzle diameter, and treatment temperature. can be controlled. In the underwater facing collision method, the temperature of the treated material increases as the number of treatments increases, so after the collision treatment has been performed, the treated material may be cooled to, for example, 4 to 20°C or 5 to 15°C, as necessary. You may. Additionally, cooling equipment can be incorporated into the opposing collision processing device.

The underwater facing collision method uses only water in addition to natural cellulose fibers, and performs nano-fine refinement by only cleavage of interactions between fibers, so there is no structural change in cellulose molecules, and there is no structural change associated with cleavage. It has many advantages, such as being able to obtain fibrous cellulose with minimal reduction in the degree of polymerization. In addition, the underwater facing collision method can improve the average fiber width, average fiber length, permeability, viscosity, and degree of polymerization of the resulting fibrous cellulose by adjusting treatment conditions such as treatment pressure, number of treatments, nozzle diameter, and treatment temperature. etc. can be controlled.

(Method for producing sulfated nanocrystals)
In order to introduce sulfonic acid groups into fibrous cellulose, for example, chlorosulfonic acid, sulfamic acid, halogenosulfonic acid, etc. may be reacted with fibrous cellulose. Further, in order to introduce an alkylsulfonic acid group having 1 to 6 carbon atoms into fibrous cellulose, for example, a halogenated alkylsulfonic acid having 1 to 6 carbon atoms may be reacted with the fibrous cellulose. In the reaction of sulfating fibrous cellulose, the crystallinity of type I cellulose decreases with the passage of reaction time. That is, as the amount of sulfonic acid groups and the like introduced into fibrous cellulose increases, the degree of crystallinity decreases. More specifically, the crystalline state of sulfated cellulose changes from cellulose nanofiber to cellulose nanocrystal, and finally becomes amorphous. This is explained as follows. As the number of sulfonic acid groups and the like introduced into the hydroxyl groups of fibrous cellulose increases, the electrostatic repulsive force due to the sulfonic acid groups and the like increases. This is because the fibrous cellulose is gradually defibrated as the electrostatic repulsion increases, and the fiber width and fiber length are gradually shortened. Therefore, it is preferable to select the fiber width and fiber length of the fibrous cellulose in consideration of the decrease in crystallinity due to the introduction of sulfonic acid groups and the like. In this way, sulfated cellulose nanocrystals are obtained by substituting hydroxyl groups in fibrous cellulose with sulfonic acid groups, etc., and introducing sulfonic acid groups, etc. until the resulting sulfated cellulose becomes nanocrystalline.

Hereinafter, reaction conditions such as raw material pretreatment, reaction time, and reaction temperature for introducing sulfonic acid groups and the like into fibrous cellulose will be explained. As a raw material pretreatment, it is preferable to freeze-dry the fibrous cellulose. This is because the fibrous cellulose used as a raw material is an aqueous dispersion, so the amount of water removed by the solvent replacement method is insufficient, and the reaction efficiency is not improved.

Before introducing sulfonic acid groups, etc., it is preferable to irradiate the dispersion liquid in which the raw material fibrous cellulose is dispersed with ultrasonic waves at a power amount of 0.3 Wh to 100 Wh, preferably 0.6 Wh to 50 Wh. When the ultrasonic wave is 0.3Wh or less, aggregated fibrous cellulose can be dispersed, and reaction efficiency can be improved. Moreover, it is preferable to irradiate ultrasonic waves with a power amount of 100 Wh or less because it is possible to avoid destroying the structure of fibrous cellulose and maintain crystallinity.

Regarding the reaction time and reaction temperature in the production of sulfated cellulose nanocrystals, in order to prevent agglomeration of fibrous cellulose and to react uniformly with the hydroxyl groups on fibrous cellulose, the reaction time and temperature should be set at 0°C or higher and lower than 10°C for 30 seconds or more. It is preferable to react for 6 hours.

(Polythiophene)
The polythiophene used in the present disclosure has a repeating unit (monomer unit) represented by the following chemical formula 3.

化学式３において、Ｒ^７およびＲ^８は、それぞれ独立に水素原子、炭素数１～８のアルキル基、炭素数１～８のアルコキシ基を表すか、Ｒ^７およびＲ^８は連結して、炭素数１～８のジオキシアルキレン基、芳香環または３～７員環の脂環式環を表す。なお、化学式３のｎは、括弧内の繰り返しを示す。

In chemical formula 3, R ⁷ and R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, or R ⁷ and R ⁸ are connected to Represents a 1-8 dioxyalkylene group, an aromatic ring, or a 3-7 membered alicyclic ring. Note that n in Chemical Formula 3 indicates repetition within parentheses.

When R ⁷ and R ⁸ in Chemical Formula 3 are alkyl groups having 1 to 8 carbon atoms, they may be linear or branched. Note that the alkyl group preferably has 1 to 6 carbon atoms.
When R ⁷ and R ⁸ in Chemical Formula 3 are alkoxy groups having 1 to 8 carbon atoms, they may be either linear or branched. Note that the alkoxy group preferably has 1 to 6 carbon atoms.
When R ⁷ and R ⁸ are connected to form a dioxyalkylene group having 1 to 8 carbon atoms, the dioxyalkylene group preferably has 1 to 6 carbon atoms, more preferably 2 to 4 carbon atoms. It is.
When R ⁷ and R ⁸ are linked to form a 3- to 7-membered alicyclic ring, the alicyclic ring is preferably a 4- to 7-membered ring, more preferably a 5- to 6-membered ring. be.

The number of repeating units represented by Chemical Formula 3 forming polythiophene is not particularly limited, but may be, for example, about 2 to 50. As the number of repetitions increases, the properties of polythiophene such as heat shielding properties and conductivity improve.

The monomer (thiophene) constituting the repeating unit represented by Chemical Formula 3 is represented by Chemical Formula 4 below.

化学式４において、Ｒ^７およびＲ^８は、それぞれ独立に水素原子、炭素数１～８のアルキル基、炭素数１～８のアルコキシ基を表すか、Ｒ^７およびＲ^８とは連結して、炭素数１～８のジオキシアルキレン基、芳香環または３～７員環の脂環式環を表す。

In chemical formula 4, R ⁷ and R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, or R ⁷ and R ⁸ are connected to each other to form a carbon Represents a dioxyalkylene group of numbers 1 to 8, an aromatic ring, or a 3 to 7-membered alicyclic ring.

The thiophene represented by the chemical formula 4 is preferably a compound in which the 3- and 4-positions of the thiophene skeleton are each independently substituted with an alkyl group having 1 to 8 carbon atoms and/or an alkoxy group having 1 to 8 carbon atoms; thiophene Examples include 3,4-disubstituted thiophenes in which dioxyalkylene groups having 1 to 8 carbon atoms are formed at the 3rd and 4th positions of the skeleton. More specific examples include 3,4-dialkylthiophene, 3,4-dialkoxythiophene, and 3,4-alkylenedioxythiophene. Among these, 3,4-alkylenedioxythiophene is preferred.

Examples of the thiophene represented by chemical formula 4 include 3,4-dihexylthiophene, 3,4-diethylthiophene, 3,4-dipropylthiophene, 3,4-dimethoxythiophene, 3,4-diethoxythiophene, 3,4 -dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-methylenedioxythiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene and the like. Among these, 3,4-ethylenedioxythiophene (hereinafter sometimes abbreviated as EDOT) is preferred.

Specific examples of polythiophene represented by chemical formula 3 include poly(3,4-dihexylthiophene), poly(3,4-diethylthiophene), poly(3,4-dipropylthiophene), poly(3,4- dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-methylenedioxythiophene), poly (3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and the like. Among these, poly(3,4-ethylenedioxythiophene), also abbreviated as PEDOT, is preferred.

(Method for manufacturing PT/CS composite)
The PT/CS composite is obtained by polymerizing thiophene to produce polythiophene in the coexistence of sulfated cellulose nanocrystals and thiophene, and doping the sulfated cellulose nanocrystals into polythiophene.

Specifically, the PT/CS composite can be produced by oxidative polymerization of thiophene represented by the chemical formula 4 in the presence of sulfated cellulose nanocrystals, a solvent, and an oxidizing agent. For example, thiophene represented by chemical formula 4 and an oxidizing agent are added to a solution prepared by dissolving sulfated cellulose nanocrystals in a solvent in advance, and the thiophene is polymerized to produce polythiophene. is obtained in a state where it is dispersed in a solution. In the obtained PT/CS composite, the bonding mode between the polythiophene and the sulfated cellulose nanocrystals is not intended to be interpreted in a limited manner, but the anion of the sulfated cellulose nanocrystals is doped with the polythiophene produced by the polymerization reaction. It is thought that it is compounded in a state where it is

In the production of the PT/CS composite, the amount of thiophene and sulfated cellulose nanocrystals represented by chemical formula 4 used as raw material compounds is determined by the ratio of polythiophene to sulfated cellulose nanocrystals in the heat ray absorbing material described above. It is preferable to set it within a range that can satisfy. Specifically, the amount of thiophene represented by chemical formula 4 is preferably in the range of 12.5 parts by mass to 400 parts by mass, more preferably 25 parts by mass to 200 parts by mass, per 100 parts by mass of the anionic polysaccharide. range.

The oxidizing agent (sometimes referred to as a polymerization initiator) used in the production of the PT/CS composite is not particularly limited as long as it can oxidatively polymerize thiophene represented by chemical formula 4, but for example, peroxodisulfuric acid , sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, inorganic ferric oxide salts, organic ferric oxide salts, hydrogen peroxide, potassium permanganate, potassium dichromate, alkali perborate salts, sulfuric acid Examples include iron (III) and iron (III) chloride. Among these, peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) chloride are preferred. These oxidizing agents may be used alone or in combination of two or more.

In the production of the PT/CS composite, the amount of the oxidizing agent used is not particularly limited, but for example, it is preferably in the range of 0.1 equivalent to 5 equivalents, more preferably The amount ranges from 0.3 equivalents to 2 equivalents.

When producing a PT/CS composite (polymerization of polythiophene (PEDOT)), sulfated cellulose nanocrystals (PEDOT) are added so that when sulfated cellulose nanocrystals (CS) is 1, thiophene is in the range of 0.5 to 9. The molar ratio of crystal (CS) and thiophene (EDOT) can be set. In particular, when polymerizing polythiophene (PEDOT), the molar ratio of sulfated cellulose nanocrystals (CS) and thiophene (EDOT) was changed from 1:1 (sulfated cellulose nanocrystals: thiophene = 1: (1<)) to thiophene. It is preferable to increase the amount of (EDOT) because the near-infrared light absorption characteristics can be further improved. When polymerizing polythiophene (PEDOT), the molar ratio of sulfated cellulose nanocrystals (CS) and thiophene (EDOT) is set to 1:4 (sulfated cellulose nanocrystals: thiophene = 1:4). This is preferable because the near-infrared light absorption characteristics can be further improved. In this way, when producing a PT/CS composite (polymerization of polythiophene (PEDOT)), when the number of sulfated cellulose nanocrystals (CS) is 1, it is preferable to increase the amount of thiophene to more than 1, more preferably thiophene. It is preferable to set the molar ratio of sulfated cellulose nanocrystals (CS) and thiophene (EDOT) so that the ratio is in the range of 2 to 8. Note that when thiophene (EDOT) is in excess of sulfated cellulose nanocrystals (CS), it becomes difficult to generate polythiophene (PEDOT) on sulfated cellulose nanocrystals (CS), and the degree of polymerization between thiophenes (EDOT) decreases. Since many of the materials have a low value, it is thought that the near-infrared light absorption characteristics (electroconductivity) of the obtained heat ray absorbing material become low.

During the production of the PT/CS composite (polymerization of polythiophene (PEDOT)), the concentration of the polymerization initiator relative to thiophene (EDOT) is set, for example, in the range of 5 mol% to 92.5 mol%, or 5.7 mol% to 92.5 mol%. can be in the range of When producing a PT/CS composite (polymerization of polythiophene (PEDOT)), it is important to set the concentration of the polymerization initiator to thiophene (EDOT) in the range of 11.6 mol% to 46.2 mol% to improve near-infrared light absorption. This is preferable because the characteristics can be further improved. Note that if the polymerization initiator is insufficient, the polymerization of polythiophene (PEDOT) will be difficult to proceed, and if the polymerization initiator is too large, the degree of polymerization of polythiophene (PEDOT) will tend to decrease. It is thought that a polymer of sulfated cellulose nanocrystals (CS) produced outside the system has a very low degree of polymerization.

The solvent used for producing the PT/CS composite may be any solvent as long as it can dissolve the sulfated cellulose nanocrystals and carry out the polymerization reaction of thiophene. Specifically, water-based solvents may be used, and water is preferably used. Further, as the solvent, an aqueous solvent obtained by mixing water with a lower alcohol such as methanol or ethanol, or a polar organic solvent such as acetone or acetonitrile may be used. These solvents may be used alone or in combination of two or more.

In the production of the PT/CS composite, the amount of the solvent used is not particularly limited, but for example, it is preferably in the range of 1,000 ml to 50,000 ml, more preferably 3,000 ml to 30,000 ml per mole of thiophene represented by chemical formula 4. range.

The reaction time and reaction temperature in the production of the PT/CS composite may be appropriately set depending on the type of thiophene or sulfated cellulose nanocrystals used as the raw material compound, the type of oxidizing agent, etc. The reaction temperature in producing the PT/CS composite is, for example, preferably in the range of 5°C to 90°C, more preferably in the range of 10°C to 80°C. The reaction time in producing the PT/CS composite is, for example, preferably in the range of 1 hour to 96 hours, more preferably in the range of 5 hours to 48 hours.

As described above, by polymerizing thiophene represented by Chemical Formula 4 in the presence of sulfated cellulose nanocrystals, a dispersion solution of the PT/CS composite can be obtained. The PT/CS composite can be produced in the form of a dispersion obtained after the reaction, or after separating and purifying the PT/CS composite as necessary, as an additive to a heat-absorbing film or the like.

(Heat ray absorption film using PT/CS composite)
By adding a PT/CS composite to a polymer (synthetic resin), a heat ray absorbing film having excellent heat ray absorption properties derived from the PT/CS composite can be obtained. Polymers that are the matrix of the heat ray absorbing film include vinyl acetate-polyvinyl alcohol copolymer, polyol, polypropylene glycol, polyethylene glycol, polyvinyl alcohol, polyvinyl alcohol-ethylene copolymer, polyvinyl alcohol-butene diol copolymer, polyethylene- Vinyl acetate copolymer, cellulose monoalkylate (alkyl group with 1 to 18 carbon chains), cellulose dialkylate (alkyl group with 1 to 18 carbon chains), cellulose trialkylate (alkyl group with 1 to 18 carbon chains) ), polyethylene, polypropylene, polystyrene, polyalkyl (alkyl group having 1 to 18 carbon chains) a(meth)acrylate, sodium carboxymetal cellulose, cellulose alkyl ether (alkyl group having 1 to 18 carbon chains), polyethylene terephthalate, Polyethylene naphthalate, polyacrylamide and its derivatives, poly(meth)acrylic acid, polyvinyl chloride, cellulose, starch, gelatin, pullulan, polyethylene-vinyl alcohol copolymer, polyurethane, nylon-6,6, nylon-6, nylon -6,10, polyvinylalkyral (alkyl group having 1 to 18 carbon chains), polyimide, syndiotactic 1,2-polybutadiene, 1,4-polybutadiene, polyisoprene, polystyrene-butadiene copolymer, ABS resin, Examples include phenolic resin, silosaquine polymer, and silsesquioxane.

The amount of the PT/CS composite in the heat-absorbing film is preferably in the range of 0.5% to 6%, more preferably in the range of 1% to 4%. When the amount of the PT/CS composite is 0.5% or more, near-infrared rays can be absorbed well, and when it is 6% or less, visible light can be appropriately transmitted, and heat ray absorption properties are improved. and visible light transparency. In the heat ray absorbing film, the PT/CS composite can be nano-dispersed due to the charge repulsion between the sulfonic acid groups, etc. of the sulfated cellulose nanocrystals of the PT/CS composite. Thereby, the heat ray absorbing film can have uniform heat ray absorption characteristics and visible light transmittance as a whole due to the dispersed PT/CS composite. In addition, the heat ray absorbing film can exhibit the overall mechanical strength improvement effect derived from the sulfated cellulose nanocrystals due to the dispersed PT/CS composite.

(Heat ray absorption membrane using PT/CS composite)
Since the PT/CS composite has excellent film forming properties, it can be used as a heat ray absorbing film by forming the film on a substrate such as a glass plate.

Specifically, a heat ray absorbing film using a PT/CS composite is produced by applying a dispersion containing the PT/CS composite to the entire surface of a substrate or in a predetermined shape, and then drying to remove the solvent. It can be manufactured by Before drying, add hydroxy groups, halogen groups, sulfone groups, carbonyl groups, amino groups, imino groups, carboxyl groups, sulfide groups, disulfide groups, sulfonyl groups, amide groups, etc. to ethanol, methanol, ethylene glycol, etc. as additives. When a compound having at least one polar group selected from the group consisting of nitrile groups is added to the solvent, the heat ray absorption characteristics of the heat ray absorption film can be improved. Note that the amount of the compound having a polar group to be added as an additive is not particularly limited as long as it does not affect the dispersion of the PT/CS composite.

The method of applying the polymer or dispersion containing the PT/CS composite to the substrate is not particularly limited, but examples include spray coating, spin coating, air knife coating, curtain coating, blade coating, and dip coating. , coating methods such as cast method, two-roll coating method, gate roll press method, roll coating method, bar coating method, die coating method, gravure method, and mist method; Wet processes such as printing and patterning methods such as inkjet It will be done. Among these, spin coating and casting are preferred.

The drying method is not particularly limited, and examples thereof include natural drying, heat drying, freeze drying, reduced pressure drying, hot air drying, heat pressure drying, infrared drying, supercritical drying, and the like. The drying temperature is appropriately set depending on the drying method, and is preferably in the range of 50°C to 250°C, more preferably in the range of 60°C to 150°C. The drying temperature is more preferably in the range of 80°C to 120°C. By setting the drying temperature to 250° C. or lower, it is possible to effectively prevent the heat ray absorption properties of the PT/CS composite from deteriorating during drying. In particular, from the viewpoint of heat resistance of CS, 150°C is preferable, and 120°C or less is more preferable. Furthermore, by setting the drying temperature high, the drying time and the quality of the coating film during drying can be improved.

Examples of the substrate used for forming the PT/CS composite film include a glass plate, a plastic sheet, and a plastic film. Plastics include polyester, polyethylene, polypropylene, polystyrene, polyimide, poly(meth)acrylate, polyamide, polyethylene terephthalate, polyethylene naphthalate, epoxy resin, chlorine resin, silicone resin, phenol resin, and blends of these. can be mentioned.

The absorbance value per unit thickness obtained by dividing the absorbance at 500 nm of the heat ray absorbing material by the thickness (nm) of the heat ray absorbing film made of the heat ray absorbing material is referred to as the "visible light absorption characteristic ratio." In addition, the value of the absorbance per unit thickness, which is obtained by dividing the absorbance at 800 nm of the heat ray absorbing material by the thickness (nm) of the heat ray absorbing film formed from the heat ray absorbing material, is calculated as "Near-infrared light absorption characteristics. It is called “ratio.”
・Visible light absorption characteristic ratio = absorbance at 500 nm/thickness of heat ray absorption film (nm)
・Absorption characteristic ratio of near-infrared light = Absorbance at 800 nm / Thickness of heat ray absorption film (nm)
The absorption characteristic ratio at a wavelength of 500 nm in the heat ray absorbing material is preferably in the range from a value as close to 0 as possible to 10 because the heat ray absorbing material (heat ray absorbing film) has good transparency. Further, the absorption characteristic ratio at a wavelength of 800 nm is preferably 6 or more since a good heat ray absorption effect can be obtained.

The heat ray absorbing material of the present invention is generally applicable to fields where a heat ray absorption effect is required, such as food, beverages, cosmetics, medicine, various chemical supplies, paper manufacturing, civil engineering, paints, inks, agricultural chemicals, architecture, epidemic prevention drugs, and electronics. It can be used in materials, flame retardants, household goods, cleaning agents, etc. Specifically, it can be used as food packaging agents, beverage bottles, sun protection agents, heat ray protection agents, compounding materials for rubber and plastics, additives for paints, additives for adhesives, additives for paper manufacturing, etc. It can be applied to rubber and plastic materials, paints, adhesives, exterior wall coatings, heat-shielding sheets for windows, heat-shielding sheets for roofs, cosmetics, sunshade covers for tea cultivation, etc. that contain them as constituent components. Also, when using it, the effect can be sustained by using a UV shielding agent or a shielding sheet.

Next, the heat ray absorbing material, the method for producing the heat ray absorbing material, and the heat ray absorbing film containing the heat ray absorbing material according to the present invention will be described below with reference to Examples.

For Examples and Comparative Examples, the fiber width and degree of polymerization of fibrous cellulose were measured. In addition, for Examples and Comparative Examples, the degree of crystallinity of sulfated cellulose obtained by sulfating fibrous cellulose and the degree of substitution of sulfonic acid groups, etc. in sulfated cellulose were measured. Then, the absorbance of light was measured for Examples and Comparative Examples. In the comparative examples, the sulfated cellulose obtained by introducing sulfonic acid groups into fibrous cellulose is not nanocrystalline and cannot be strictly called sulfated cellulose nanocrystals (CS). A complex of polythiophene (PEDOT) and polythiophene (PEDOT) is conveniently referred to as a PEDOT/CS complex.

(Method for measuring cellulose fiber width and fiber length)
The fiber width of fibrous cellulose, the fiber width and fiber length of sulfated cellulose can be determined using a field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number SU8000) or a transmission electron microscope (manufactured by JEOL Ltd., model number SU8000). Calculated from electron micrographs taken using a model number JEM-2000X).

(Method for measuring crystallinity and degree of substitution of sulfonic acid groups, etc.)
The degree of crystallinity of sulfated cellulose is measured using an X-ray diffraction (XRD) device (Rigaku Corporation: SmartLab-9KW), where I ₂₀₀ is the diffraction intensity of the lattice plane (200 planes) and I _am is the diffraction intensity of the amorphous part. It is calculated from the measurement results using Equation 1 below.
Cellulose type I crystallinity (%) = [(I ₂₀₀ - I _am )/I ₂₀₀ ] x 100...Formula 1
Here, I ₂₀₀ indicates the X-ray diffraction intensity at 2θ=22.6°, and I _am indicates the X-ray diffraction intensity at 2θ=18.5°.
The degree of substitution of sulfonic acid groups, etc. in sulfated cellulose is calculated from the results of elemental analysis of sulfated cellulose.

(Method of measuring absorbance)
The heat ray absorbing materials (PEDOT/CS composites) of Examples and Comparative Examples were formed into films by spin coating, and the absorbance was measured for each of the obtained heat ray absorbing films. The absorbance of light at the optical path length of the heat ray absorbing film prepared on a flat plate with a thickness of 2 mm was measured every 1 nm in the wavelength range of 300 nm to 2000 nm using a near-infrared spectrophotometer manufactured by JASCO Corporation. . The obtained absorbance at 500 nm is defined as "absorbance of visible light", and the absorbance at 800 nm is defined as "absorbance of near-infrared light". The value of absorbance per unit thickness obtained by dividing the absorbance at 500 nm by the thickness (nm) of the heat ray absorbing film is defined as the "visible light absorption characteristic ratio", and the absorbance at 800 nm is the thickness (nm) of the heat ray absorbing film. The value of absorbance per unit thickness divided by is defined as the " absorption characteristic ratio of near-infrared light."
・Visible light absorption characteristic ratio = absorbance at 500 nm/thickness of heat ray absorption film (nm)
・Absorption characteristic ratio of near-infrared light = Absorbance at 800 nm / Thickness of heat ray absorption film (nm)

(Production of fibrous cellulose by ACC method)
Using softwood pulp and bamboo pulp as raw materials, the number of treatments was varied to obtain 1 wt% fibrous cellulose aqueous dispersions with different degrees of fibrillation. Next, the degree of polymerization of the fibrous cellulose was measured. Dissolve 0.15 g of fibrous cellulose sample solid content to make 30 ml of 0.5 M copper ethylene diamine solution, and measure the viscosity by measuring the flow time after incubating at 25°C using a Cannon-Fenske kinematic viscosity tube. Measurements were made. The degree of polymerization was calculated using the following formula, where the viscosity of this fibrous cellulose copper ethylene diamine solution was set as η, and the viscosity of the 0.5M copper ethylene diamine solution was set as η0.
Intrinsic viscosity [η] = (η/η0)/{c(1+A×η/η0)}
(However, c is the fibrous cellulose concentration (g/dL) at the time of viscosity measurement, and A is a unique value depending on the type of solution. In the case of a 0.5M copper ethylenediamine solution, A = 0.28.)
Degree of polymerization DP=[η]/aK
(K and a are values determined by the type of polymer and solvent used; in the case of cellulose dissolved in copper ethylenediamine, K = 5.7 × 10 ^-3 and a = 1.)
As a result, those whose degree of polymerization was in the range of greater than 710 and less than or equal to 900 were defined as "low" defibration degree, and those with a degree of polymerization in the range of greater than or equal to 570 and less than or equal to 710 were defined as "high". Here, it means that the fiber width increases as the degree of polymerization of cellulose increases.

(Example 1)
Using softwood pulp as a raw material, a 1 wt % dispersion of fibrous cellulose (cellulose nanofibers) was obtained by the ACC method. Next, the degree of polymerization was measured three times, and the average value was 760, which confirms that the degree of fibrillation of the fibrous cellulose (cellulose nanofiber) according to Example 1 is "low". The fiber width of the fibrous cellulose measured using an electron microscope was 4 nm to 1180 nm. The fibrous cellulose of Example 1 has a molecular weight of about 123,000 (Chuetsu Pulp Kogyo Co., Ltd., NB-B), although its value varies because it is a natural material.

2.00 g of the obtained fibrous cellulose was added to 200 ml of N,N-dimethylformamide (DMF) and stirred at room temperature for over 14 hours. Next, the temperature of the water bath was set to 10° C., and after internal ultrasonic waves were irradiated for 2 minutes, 3.6 ml of chlorosulfonic acid was gradually added dropwise under nitrogen aeration and mixed. The reaction was started when the chlorosulfonic acid was added dropwise, and the chlorosulfonic acid was added dropwise over 50 minutes and mixed. Next, 15 ml of the reaction solution was poured into 150 ml of a saturated ethanol solution of sodium acetate to cause reprecipitation, and the precipitate was washed once with a saturated ethanol solution of sodium acetate, and then washed with ethanol until the supernatant liquid became neutral. After dissolving the precipitate in water and performing dialysis, it was recovered in the form of an aqueous solution, and the degree of substitution of sulfonic acid groups and the like and the degree of crystallinity of the obtained sulfated cellulose were measured. Note that the sulfated cellulose obtained by sulfation in Example 1 is in the form of nanocrystals, and it can be said that Example 1 uses sulfated cellulose nanocrystals.

The aqueous dispersion of sulfated cellulose of Example 1 was prepared to 50 ml at 0.2 wt%, and concentrated hydrochloric acid was added to make it acidic. Next, 0.10 g of 3,4-ethylenedioxythiophene (referred to as EDOT) as a thiophene monomer was added, and internal ultrasound was applied for 5 minutes to disperse EDOT. Next, 0.19 g of potassium peroxodisulfate as a polymerization initiator and 0.5 ml of a 1.4 mg/ml iron (III) sulfate n-hydrate aqueous solution were added. The mixture was stirred at room temperature for 24 hours and dialyzed using a dialysis membrane for over 72 hours. Water was used as the solvent, and after drying with an evaporator, the solid content was adjusted to 0.60 wt% by redispersing it in water. A dispersion was obtained.

The PEDOT/CS composite (heat ray absorbing material) of Example 1 dispersed in water as a solvent was formed into a film on a glass substrate by a spin coating method, and the solvent was removed by drying. A heat ray absorbing film made of an absorbing material was obtained.

(Examples 2 to 7)
Example 2 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 60 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Example 3 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 120 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Example 4 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 180 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Example 5 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 270 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Example 6 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 300 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Example 7 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 360 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Note that the sulfated cellulose obtained by sulfation in Examples 2 to 7 is in the form of nanocrystals, and it can be said that Examples 2 to 7 use sulfated cellulose nanocrystals.

(Comparative Examples 1-2)
Comparative Example 1 was the same as Example 1, except that the reaction was started at the start of dropping chlorosulfonic acid, and the sulfation time was 10 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
Comparative Example 2 was the same as Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 20 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is.
The sulfated cellulose obtained by sulfation in Comparative Examples 1 and 2 is in the form of nanofibers, and unlike Examples 1 to 7, it cannot be said to be sulfated cellulose nanocrystals.

The measurement results in Examples 1 to 7 are shown in Table 1 below. Further, the measurement results for Comparative Examples 1 and 2 are shown in Table 2 below. The quality of the heat ray absorbing material is determined as "〇" when the 500 nm absorption characteristic ratio is smaller than the 800 nm absorption characteristic ratio, and the 500 nm absorption characteristic ratio is 10 or less, and the 800 nm absorption characteristic ratio is 6 or more. do. In addition, if either or both of the 500 nm absorption characteristic ratio is larger than 10 or the 800 nm absorption characteristic ratio is smaller than 6 is satisfied, it is determined as "×". The absorption characteristic ratio at a wavelength of 500 nm is preferably in the range from a value extremely close to 0 to 10 because the heat ray absorbing film has good transparency. Further, the absorption characteristic ratio at a wavelength of 800 nm is preferably 6 or more since a good heat ray absorption effect can be obtained.

From the results in Table 1, Examples 1 to 7 using nanocrystalline sulfated cellulose with a crystallinity of 53% or less showed excellent absorption of near-infrared light while suppressing absorption of visible light. It was confirmed that both near-infrared light absorption characteristics and visible light transparency were achieved. On the other hand, as shown in Table 2, Comparative Examples 1 and 2, which are nanofiber sulfated cellulose with a crystallinity of more than 53%, have a visible light absorption characteristic ratio of 14 or more. Furthermore, absorption in the visible light region becomes extremely large, making it undesirable for use as a heat ray absorbing film that is required to be transparent. In this way, a heat ray absorbing material using nanocrystalline sulfated cellulose as a dopant has a high effect of reducing transmittance of near-infrared light, improves coating properties, and produces a stable film with excellent transparency. It is possible to create

(Examples 8 to 10)
In Example 8, a 1 wt % dispersion of fibrous cellulose (cellulose nanofiber) with a high degree of defibration was obtained using softwood pulp as a raw material by the ACC method. Next, the degree of polymerization was measured three times, and the average value was 580, which confirms that the degree of defibration of the obtained fibrous cellulose is "high." The fibrous cellulose of Example 8 has a molecular weight of about 95,000 (NB-C, Chuetsu Pulp Kogyo Co., Ltd.), although its value varies because it is a natural material. Next, using this as a raw material, sulfated cellulose, a PEDOT/CS composite, and a heat ray absorbing membrane were produced in the same manner as in Example 1, except that the reaction was started at the start of dropping chlorosulfonic acid for 30 minutes.
Example 9 was the same as Example 2 (sulfation time 60 minutes) except that the fibrous cellulose dispersion obtained in Example 8 was used as a raw material.
Example 10 was the same as Example 4 (sulfation time 180 minutes) except that the fibrous cellulose dispersion obtained in Example 8 was used as a raw material.

The measurement results in Examples 8 to 10 are shown in Table 3 below.

From the results in Table 3, even in Examples 8 to 10 where the fibrous cellulose has a high degree of fibrillation (NB-C), Examples 1 to 10 where the fibrous cellulose has a high degree of fibrillation (NB-B) Similarly to No. 7, it can be confirmed that both excellent near-infrared light absorption characteristics and visible light transmittance are achieved.

(PEDOT/CS composite made from bamboo pulp)
(Examples 11 to 13)
Using bamboo pulp as a raw material, a 1 wt % dispersion of fibrous cellulose (cellulose nanofibers) was obtained by the ACC method. Next, the degree of polymerization was measured three times, and the average value was 580, which indicates that the degree of fibrillation of the fibrous cellulose (cellulose nanofiber) according to Examples 11 to 13 is "high". confirmed. The fiber width of the fibrous cellulose measured using an electron microscope was 4 nm to 1180 nm, and the fiber length was 100000 nm or more. The fibrous cellulose used in Examples 11 to 13 has a molecular weight of about 95,000 (BB-C, Chuetsu Pulp Kogyo Co., Ltd.), although its value varies because it is a natural material.

2.00 g of the obtained fibrous cellulose was added to 200 ml of N,N-dimethylformamide (DMF) and stirred at room temperature for over 14 hours. Next, the temperature of the water bath was set to 10° C., and after internal ultrasonic waves were irradiated for 2 minutes, 3.6 ml of chlorosulfonic acid was gradually added dropwise under nitrogen aeration and mixed. The reaction was started when the chlorosulfonic acid was added dropwise, and the chlorosulfonic acid was added dropwise and mixed over a period of 120 minutes in Example 11, 360 minutes in Example 12, and 480 minutes in Example 13. Next, 15 ml of the reaction solution was poured into 150 ml of a saturated ethanol solution of sodium acetate to cause reprecipitation, and the precipitate was washed once with a saturated ethanol solution of sodium acetate, and then washed with ethanol until the supernatant liquid became neutral. After dissolving the precipitate in water and performing dialysis, it was recovered in the form of an aqueous solution, and the degree of substitution of sulfonic acid groups and the like and the degree of crystallinity of the obtained sulfated cellulose were measured. Note that the sulfated cellulose obtained by sulfation in Examples 11 to 13 was in the form of nanocrystals, and it can be said that Examples 11 to 13 used sulfated cellulose nanocrystals.

Next, the aqueous dispersions of sulfated cellulose of Examples 11 to 13 were prepared at 0.2 wt% to 50 ml, and concentrated hydrochloric acid was added to make them acidic. Next, 0.10 g of 3,4-ethylenedioxythiophene (referred to as EDOT) as a thiophene monomer was added, and internal ultrasound was applied for 5 minutes to disperse EDOT. Next, 0.19 g of potassium peroxodisulfate as a polymerization initiator and 0.5 ml of a 1.4 mg/ml iron (III) sulfate n-hydrate aqueous solution were added. The mixture was stirred at room temperature for 24 hours and dialyzed using a dialysis membrane for over 72 hours. Water was used as the solvent, and after drying with an evaporator, the solid content was adjusted to 0.60 wt% by redispersing it in water. An aqueous dispersion of material) was obtained.

The PEDOT/CS composites (heat ray absorbing material) of Examples 11 to 13 dispersed in water as a solvent were formed into a film on a glass substrate by spin coating, and the solvent was removed by drying. A heat ray absorbing film made of the heat ray absorbing material according to No. 13 was obtained. The measurement results in Examples 11 to 13 are shown in Table 3 above.

(Comparative example 3)
Comparative Example 3 was the same as Example 11 except that the reaction was started at the start of dropping chlorosulfonic acid and the sulfation time was 1440 minutes to introduce sulfonic acid groups into fibrous cellulose to obtain sulfated cellulose. It is. The sulfated cellulose obtained by sulfation in Comparative Example 3 is amorphous, and unlike Examples 11 to 13, it cannot be said to be sulfated cellulose nanocrystals.

(Comparative example 4)
Poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (hereinafter referred to as PEDOT/PSS) was prepared in the same manner as in Example 1. The measurement results in Comparative Example 3 and Comparative Example 4 are shown in Table 2 above.

From the results in Table 3, even in Examples 11 to 13 in which the fibrous cellulose derived from bamboo pulp has a high degree of fibrillation (BB-C), Examples 1 to 13 in which the fibrous cellulose derived from softwood pulp was used As in Example 10, it can be confirmed that both excellent near-infrared light absorption characteristics and visible light transmittance are achieved. Furthermore, it can be seen that the example has excellent near-infrared light absorption characteristics compared to Comparative Example 4 using PEDOT/PSS. As described above, it can be said that the PEDOT/CS composite according to the example has excellent near-infrared light absorption characteristics and excellent visible light transmittance at a level that cannot be achieved with PEDOT/PSS. In addition, examples using nanocrystalline sulfated cellulose with a crystallinity of 20% or more have excellent near-infrared light absorption properties, with high absorption of near-infrared light while suppressing absorption of visible light. It was confirmed that both visible light transmittance and transparency were achieved. On the other hand, as shown in Table 2, Comparative Example 3, which is an amorphous sulfated cellulose with a crystallinity of less than 20%, has a visible light absorption characteristic ratio of 6 or less, which shows that the The absorption in the infrared light region is small, and it does not exhibit favorable heat ray absorption characteristics as a heat ray absorbing material. Thus, it can be confirmed that the cellulose I type crystallinity of the sulfated cellulose nanocrystals is preferably in the range of 20% to 53%.

The transmittance of the PEDOT/CS composite according to Example 12 and the PEDOT/PSS of Comparative Example 4 was measured, and the results are shown in FIG. 3. As shown in FIG. 3, Example 12 and Comparative Example 3 have the same transmittance of about 70% for visible light at a wavelength of 500 nm. However, regarding the transmittance in the near infrared wavelength range of 700 to 950 nm, it can be seen that Example 12 absorbs more near infrared light than Comparative Example 3. Preferred near-infrared absorption characteristics in Examples are 730 nm, 830 nm, 909 to 915 nm, 960 nm, and 965 nm of CH and OH groups (see chemical formula 1) specific to cellulose sugar chains in cellulose sulfate nanocrystals (CS). This is thought to be due to the absorption of

(Preparation of heat ray absorbing film)
Next, 30 g of a solution of butenediol/vinyl alcohol polymer (Nichigo G-Polymer, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) prepared to 10 wt% and 0 octylphenol ethoxylate (TritonX, manufactured by Dow Chemical Co., Ltd.) as a surfactant were added. .06 g was added thereto, and 5 g of the PEDOT/CS composite aqueous solution according to Example 12 prepared to 1.2 wt % was mixed. The obtained mixed solution was applied to a hydrophilized glass substrate by a squeegee method and air-dried to form a heat ray absorbing film according to Example 12 with a thickness of 40 μm on the glass substrate.

(Heat-shielding properties of heat-absorbing film)
Next, the heat shielding properties of the heat ray absorbing film in which the PEDOT/CS composite according to Example 12 was blended with a polymer were measured. Further, using PEDOT/PSS of Comparative Example 4, a film was produced in the same manner as in Example 12. Note that Comparative Example 5 uses only a glass substrate without a film, and Comparative Example 6 uses only the same polymer as Example 12 (does not contain heat ray absorbing material or PEDOT/PSS) to produce a film.

The heat shielding properties of the films of Example 12, Comparative Examples 4 and 6, and Comparative Example 5 were measured as follows. As shown in FIG. 4, a temperature recording device was installed inside the insulation box, and a glass substrate was placed so as to cover the opening made in the ceiling of the insulation box. A heat ray absorbing film was placed on a glass substrate, and a visible light cut filter was further placed on the heat ray absorbing film. Note that Comparative Example 5 was not covered with a visible light cut filter. A simulated sunlight irradiation device (light source) installed above the insulation box irradiated light toward the opening of the insulation box, and the temperature was recorded every second using a temperature recording device. The results are shown in Table 4 and FIG. 5.

From the results in Table 4 and FIG. 5, it can be seen that the heat ray absorbing film according to Example 12 using PEDOT/CS has a higher heat shielding effect than the film using PEDOT/PSS.

(Tensile strength of heat ray absorbing film)
30 g of a solution of butenediol/vinyl alcohol polymer (Nichigo G-Polymer, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) prepared to 10 wt% and 0.06 g of octylphenol ethoxylate (TritonX, manufactured by Dow Chemical) as a surfactant. In addition, 5 g of the PEDOT/CS composite aqueous solution according to Example 12 prepared at 1.2 wt% was added to the PEDOT/CS composite at a content of 4.0 wt%, 2.0 wt%, 0.5 wt%, and 0.4 wt%. %. The obtained mixed solution was applied to a hydrophilized glass substrate by a squeegee method and air-dried, thereby forming examples 12-1 to 12-1 with different contents of the heat ray absorbing material on the glass substrate as shown in Table 4. A heat ray absorbing film according to No. 12-4 was formed. Further, using PEDOT/PSS of Comparative Example 4, a film was produced in the same manner as in Example 12. In addition, in Comparative Example 6, a film was produced using only the same polymer as in Example 12 (no heat ray absorbing material or PEDOT/PSS was included). The tensile strength of each film was then measured. Tensile strength is measured based on JIS K 7127. The results are shown in Table 5.

From the results shown in Table 5, it can be seen that the heat ray absorbing films of Examples 12-1 to 12-4 containing the PEDOT/CS composite of Example 12 have improved tensile strength. This is thought to be due to the PEDOT/CS composite forming a network in the film, which improves the mechanical strength. In particular, it is preferable that 0.5% or more of the PEDOT/CS composite is blended from the viewpoint of improving mechanical strength.

(Test 1 to Test 3)
Regarding the PEDOT/CS composite, we will investigate the relationship between its conductivity and optical properties, taking into account the polymerization conditions of polythiophene, and evaluate its light absorption properties in the near-infrared region. In Tests 1 to 3 below, sulfated cellulose nanocrystals (CS) of Example 12 derived from bamboo pulp were used. Concentrated hydrochloric acid was added to the aqueous dispersion of sulfated cellulose of Example 12, which had been adjusted to a predetermined concentration, to make it acidic, and the pH was set as shown in Tables 6 to 8. Next, the sulfated cellulose nanocrystal aqueous dispersion was added to 3,4-ethylenedioxythiophene (EDOT) as a thiophene monomer at a molar ratio shown in Tables 6 to 8, and then internal ultrasound was applied. It was irradiated for 5 minutes to disperse the EDOT. Next, potassium peroxodisulfate as a polymerization initiator (oxidizing agent) and a 1.4 mg/ml aqueous solution of iron(III) sulfate/n-hydrate were added in the proportions shown in Tables 6 to 8. The mixture was stirred at room temperature for 24 hours and dialyzed using a dialysis membrane for over 72 hours. Water was used as the solvent, and after drying with an evaporator, the solid content was adjusted to 0.60 wt% by redispersing it in water, and the PEDOT/CS composite (heat ray absorbing material) according to Tests 1 to 3 was prepared. An aqueous dispersion of was obtained.

The PEDOT/CS composites (heat ray absorbing material) of Tests 1 to 3 dispersed in water as a solvent were formed into a film on a glass substrate by spin coating, and the solvent was removed by drying. A heat ray absorbing film made of the heat ray absorbing material according to No. 3 was obtained.

(Method for measuring electrical conductivity of PEDOT/CS composite (heat ray absorbing material))
The surface resistance values of the heat ray absorbing films made of the heat ray absorbing materials according to Tests 1 to 3 described above were measured. Specifically, the surface resistance value is measured by connecting a 4-point probe to a resistivity meter (loresta-GP MCP-T610) and pressing the heat ray absorption film against the 4-point probe, and measuring the conductivity ( S/cm) was calculated.

(Test 1: Relationship between sulfated cellulose nanocrystals and thiophene)
In Test 1, the relationship between the charge ratio (molar ratio) of thiophene (EDOT) to sulfated cellulose nanocrystals (CS) and conductivity during polymerization of polythiophene (PEDOT) was investigated. The results are shown in Table 6 and FIG. In FIG. 6, sulfated cellulose nanocrystals (CS) are expressed as SCNF, the horizontal axis shows the molar ratio of sulfated cellulose nanocrystals (CS) to thiophene (EDOT), and the vertical axis shows the conductivity ( S/cm).

As shown in Figure 6 and Table 6, the molar ratio of sulfated cellulose nanocrystals (CS) to thiophene (EDOT) was changed from 1:0.125 to 1:8, and the concentration of thiophene (EDOT) was increased. . When the molar ratio of thiophene (EDOT) to sulfated cellulose nanocrystals (CS) becomes larger than 1, the degree of increase in conductivity of the heat ray absorbing film tends to increase. When the molar ratio of EDOT) is 4, the conductivity is highest. Even when the molar ratio of thiophene (EDOT) to sulfated cellulose nanocrystals (CS) is increased to greater than 4, there is a tendency for the conductivity to decrease.

(Test 2: Relationship between thiophene and polymerization initiator (oxidizing agent))
In Test 2, the relationship between the concentration (mol %) of a polymerization initiator (potassium peroxodisulfate (KPS)) and conductivity for thiophene (EDOT) during polymerization of polythiophene (PEDOT) was investigated. The results are shown in Table 7 and FIG. In FIG. 7, potassium peroxodisulfate, which is a polymerization initiator, is expressed as KPS, the horizontal axis shows the concentration (mol%) of KPS with respect to thiophene (EDOT), and the vertical axis shows the conductivity (S/cm). ) is shown.

As shown in FIG. 7 and Table 7, the concentration of the polymerization initiator (potassium peroxodisulfate (KPS)) relative to thiophene (EDOT) was increased from 5.7 mol% to 92.5 mol%. When the concentration of the polymerization initiator relative to thiophene (EDOT) is greater than 5.7 mol%, the degree of increase in conductivity of the heat ray absorbing film tends to increase; The conductivity is the highest when it becomes. Even if the concentration of the polymerization initiator relative to thiophene (EDOT) is increased to more than 23 mol %, there is a tendency for the conductivity to decrease.

(Test 3: pH during polymerization of polythiophene)
In Test 3, the pH conditions during polymerization of polythiophene (PEDOT) were varied and the relationship between conductivity was investigated. The results are shown in Table 8 and FIG. In addition, in FIG. 8, the horizontal axis shows the pH conditions during polymerization, and the vertical axis shows the conductivity (S/cm).

As shown in FIG. 8 and Table 8, it was found that during polymerization of polythiophene (PEDOT), as the pH decreased, the conductivity increased. From Test 3, when polymerizing polythiophene (PEDOT), the pH condition is preferably lower than 1.86, and more preferably lower than 1.0.

(Relationship between conductivity and optical properties)
FIG. 9 shows the relationship between electrical conductivity and optical properties of the heat ray absorbing film created in Test 3. In FIG. 9, the horizontal axis shows wavelength (nm), and the vertical axis shows transmittance (%). As mentioned above, there is a relationship in which the conductivity improves from Test 3-6 to Test 3-1 (see Figure 8), but as shown in Figure 9, as the conductivity increases, it increases from 700 nm to 2000 nm. It can be confirmed that the light absorption in the near-infrared and infrared wavelength regions increases. As described above, as the conductivity of the heat ray absorbing film increases, it exhibits suitable absorption characteristics for near-infrared light, and it can be said that improvement in conductivity leads to improvement in near-infrared light absorption characteristics.

(summary)
As mentioned above, improvement in conductivity leads to improvement in near-infrared light absorption properties, so from the results of Test 1, when polymerizing polythiophene (PEDOT), sulfated cellulose nanocrystals (CS) and thiophene (EDOT) It is thought that by increasing the molar ratio of thiophene (EDOT) to 1:1 (sulfated cellulose nanocrystals: thiophene = 1: (1 <)), the degree of increase in near-infrared light absorption properties will increase. . When polymerizing polythiophene (PEDOT), the molar ratio of sulfated cellulose nanocrystals (CS) and thiophene (EDOT) is set to 1:4 (sulfated cellulose nanocrystals: thiophene = 1:4). It is considered that the near-infrared light absorption characteristics can be further improved.

As mentioned above, since improvement in conductivity leads to improvement in near-infrared light absorption characteristics, from the results of Test 2, when polymerizing polythiophene (PEDOT), the concentration of the polymerization initiator with respect to thiophene (EDOT) was increased by 5. It is considered that by increasing the content to more than .7 mol %, the degree of increase in near-infrared light absorption characteristics increases. Further, it is considered that in the polymerization of polythiophene (PEDOT), by setting the concentration of the polymerization initiator to thiophene (EDOT) to 23 mol %, it is possible to further improve the near-infrared light absorption characteristics.

As mentioned above, improvement in conductivity leads to improvement in near-infrared light absorption characteristics, so from the results of Test 3, setting the pH condition lower than 1.86 when polymerizing polythiophene (PEDOT) , it is thought that the degree of increase in near-infrared light absorption properties increases. Further, it is considered that by setting the pH condition to 1 or less during polymerization of polythiophene (PEDOT), it is possible to further improve near-infrared light absorption characteristics. Even when the pH is lowered in this manner, it has been confirmed that the performance of the obtained heat ray absorbing material does not deteriorate in accelerated weathering tests.

Claims (10)

Sulfated cellulose nanocrystals shown in the following chemical formula 1 obtained from fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm,
the sulfated cellulose nanocrystals doped with polythiophene;
The polythiophene is contained in a larger amount on a molar basis than the sulfated cellulose nanocrystals.
A heat ray absorbing material characterized by:

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. Sulfated cellulose nanocrystals shown in the following chemical formula 1 obtained from fibrous cellulose derived from pulp,
the sulfated cellulose nanocrystals doped with polythiophene;
The polythiophene is contained in a larger amount on a molar basis than the sulfated cellulose nanocrystals.
A heat ray absorbing material characterized by :

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. Sulfated cellulose nanocrystals shown in the following chemical formula 1 obtained from fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm,
the sulfated cellulose nanocrystals doped with polythiophene;
The cellulose type I crystallinity of the sulfated cellulose nanocrystals is in the range of 20% to 53%,
The absorption characteristic ratio per unit thickness in absorbance at a wavelength of 500 nm is 10 or less, and the absorption characteristic ratio per unit thickness in absorbance at a wavelength of 800 nm is 6 or more,
The absorption characteristic ratio per unit thickness at absorbance at a wavelength of 800 nm is greater than the absorption characteristic ratio per unit thickness at absorbance at a wavelength of 500 nm.
A heat ray absorbing material characterized by :

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. The heat ray absorbing material according to any one of claims 1 to 3 , wherein the fiber width of the sulfated cellulose nanocrystals is in the range of 2.8 nm to 8.0 nm . The hydroxyl group of fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm is replaced with a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains, and the above-mentioned process is performed until the resulting sulfated cellulose becomes nanocrystalline. By introducing a sulfonic acid group or the alkyl sulfonic acid group, sulfated cellulose nanocrystals shown in the following chemical formula 1 are obtained,
A method for producing a heat ray absorbing material obtained by polymerizing the thiophene to produce polythiophene in the coexistence of the sulfated cellulose nanocrystals and thiophene, and doping the polythiophene with the sulfated cellulose nanocrystals,
During polymerization of the polythiophene, more of the thiophene is added on a molar basis than the sulfated cellulose nanocrystals.
A method for producing a heat ray absorbing material, characterized in that:

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. The hydroxyl groups of fibrous cellulose derived from pulp are replaced with sulfonic acid groups or alkylsulfonic acid groups having 1 to 6 carbon chains, and the sulfonic acid groups or the By introducing an alkyl sulfonic acid group, sulfated cellulose nanocrystals shown in the following chemical formula 1 are obtained,
A method for producing a heat ray absorbing material obtained by polymerizing the thiophene to produce polythiophene in the coexistence of the sulfated cellulose nanocrystals and thiophene, and doping the polythiophene with the sulfated cellulose nanocrystals,
During polymerization of the polythiophene, more of the thiophene is added on a molar basis than the sulfated cellulose nanocrystals.
A method for producing a heat ray absorbing material , characterized in that :

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. The hydroxyl group of fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm is replaced with a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains, and the above-mentioned process is performed until the resulting sulfated cellulose becomes nanocrystalline. By introducing a sulfonic acid group or the alkyl sulfonic acid group, sulfated cellulose nanocrystals shown in the following chemical formula 1 are obtained,
A method for producing a heat ray absorbing material obtained by polymerizing the thiophene to produce polythiophene in the coexistence of the sulfated cellulose nanocrystals and thiophene, and doping the polythiophene with the sulfated cellulose nanocrystals,
Introducing the sulfonic acid group or the alkyl sulfonic acid group having 1 to 6 carbon chains into the fibrous cellulose so that the cellulose type I crystallinity of the sulfated cellulose nanocrystals is in the range of 20% to 53%. death,
The obtained heat ray absorbing material has an absorption characteristic ratio per unit thickness in absorbance at a wavelength of 500 nm of 10 or less, and an absorption characteristic ratio per unit thickness in absorbance at a wavelength of 800 nm of 6 or more,
The obtained heat ray absorbing material has a larger absorption characteristic ratio per unit thickness at absorbance at a wavelength of 800 nm than the absorption characteristic ratio per unit thickness at absorbance at a wavelength of 500 nm.
A method for producing a heat ray absorbing material , characterized in that :

R ¹ to R ⁶ shown in Chemical Formula 1 each independently represent a hydrogen atom, a sulfonic acid group, or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one of R ¹ to R ⁶ is a sulfonic acid group. Or an alkylsulfonic acid group having 1 to 6 carbon chains. Further, n in Chemical Formula 1 indicates repetition within parentheses. The method for producing a heat ray absorbing material according to any one of claims 5 to 7, wherein during polymerization of the polythiophene, a concentration of a polymerization initiator with respect to the thiophene is set to be greater than 5 mol%. The method for producing a heat ray absorbing material according to any one of claims 5 to 8, wherein pH conditions are set lower than 1.86 during polymerization of the polythiophene. A heat ray absorbing film comprising the heat ray absorbing material according to any one of claims 1 to 4.

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