JPH09202801A - Hydroxypropyl cellulose controlled in substitution degree distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydroxypropyl cellulose excellent in properties of its solution, not causing blocking and controlled in substitution degree distribution so that a thermoplastic temperature becomes high and provide a method for producing the hydroxypropyl cellulose. SOLUTION: This hydroxypropyl cellulose is obtained by reacting an alkali cellulose with propylene oxide. In the resultant hydroxypropyl cellulose, an average substitution mole number of hydroxypropyl groups per anhydrous glucose unit is 2-3 and a ratio of total of a substitution product having a mole substitution number of hydroxypropyl group of 2 and a substitution product having the mole substitution number of hydroxypropyl group of 3 per the hydroxypropyl cellulose is >=80mol% and a ratio of a substitution product having the mole substitution number of hydroxypropyl group of 3 is >=65mol% and a ratio of unsubstituted product is <=3mol% and a ratio of substitution product having the mole substitution number of hydroxypropyl group of 4 is <=6mol%, per the hydroxypropyl cellulose, respectively.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive, a binder,
Cosmetics, food, extrusion, paint remover, pharmaceuticals,
The present invention relates to hydroxypropyl cellulose used in a wide variety of fields such as PVC suspension polymerization aids.

[0002]

BACKGROUND OF THE INVENTION Hydroxypropyl cellulose is a nonionic polymer produced by reacting propylene oxide with alkali cellulose obtained by reacting cellulose with alkali hydroxide. Hydroxypropyl cellulose has useful physical properties such as cold water solubility, hot water insolubility, thermoplasticity, and solubility in many organic solvents, and is used in a wide range of fields of application. These properties depend on the number of hydroxypropyl group substitutions on the cellulose. As a method of expressing the number of substituents, the average number of moles of substituents "MS" per anhydroglucose unit, which is the structural unit, is the most general and widely used method. On the other hand, one of the important factors for utilizing hydroxypropyl cellulose in various fields is that the solution has excellent properties and that it is completely dissolved in the solution.

Japanese Patent Publication No. 42-10640, Japanese Patent Publication No. 45-
No. 4754 discloses a method for producing hydroxypropyl cellulose having MS of 2 or more. Although hydroxypropyl cellulose by this method exhibits cold water solubility, it does not always satisfy organic solvent solubility.

Further, Japanese Patent Publication No. 45-4754 proposes a method for producing hydroxypropyl cellulose having improved solubility in organic solvents. The MS of hydroxypropyl cellulose in this case was 3 or more. However, while hydroxypropyl cellulose having a high degree of substitution with MS exceeding 3, while exhibiting good organic solvent solubility, a powder using this hydroxypropyl cellulose,
There is a problem that what is formed in the form of granules or a film causes aggregation called blocking, which is a serious drawback in handling as a product. In addition, high-substituted hydroxypropyl cellulose having an MS of more than 3 is
Thermoplasticization temperature tends to decrease as the MS value increases, but when the plasticization temperature is low, when the product is crushed and formed into a powder, it is plasticized in the crusher and the work becomes difficult. There was a problem of doing.

Further, JP-B-51-32676, JP-B-52-14262, JP-A-54-156086,
The hydroxypropyl cellulose obtained by the production method disclosed in JP-A-56-802 had an MS of 3 or more, caused blocking, and had a low thermoplastic temperature.

[0006]

Therefore, it is considered that the MS of hydroxypropyl cellulose which is excellent in the properties of the solution and does not cause blocking is preferably 2 or more and not more than 3, but the MS is in the range of 2 to 3. However, the above-mentioned physical properties were not sufficiently satisfied. In order to secure good physical properties, management of the MS value alone is not sufficient, and the composition ratio of substitution products having different hydroxypropyl group substitution mole numbers in hydroxypropyl cellulose is important. It is desired to control the ratio of hydroxypropyl cellulose, which has excellent solution properties and does not cause blocking, but none is sufficiently satisfied.

It is an object of the present invention to provide hydroxypropyl cellulose which has excellent solution properties, does not cause blocking, and has a controlled substitution degree distribution so that the thermoplastic temperature is high, and a method for producing the same. To do.

[0008]

The present inventors have conceived the present invention as a result of extensive studies for solving the above-mentioned problems.
In order to achieve the above object, the invention described in claim 1 is a hydroxypropylcellulose obtained by reacting alkali cellulose with propylene oxide,
An average number of moles of hydroxypropyl group substitution per anhydroglucose unit is 2 to 3, and a substitution product of hydroxypropyl group substitution mol number 2 and a substitution product of hydroxypropyl group substitution mol number 3 in the hydroxypropyl cellulose. The ratio of the total of the above is 80 mol% or more, the ratio of the substitution product of the hydroxypropyl group substitution mol number 3 is 65 mol% or more, the ratio of the non-substitution product is 3 mol% or less, and the substitution product ratio of the hydroxypropyl group substitution mol number 4 is 6 mol%. The following is hydroxypropyl cellulose.

The invention described in claim 2 is the method for producing hydroxypropyl cellulose according to claim 1, wherein the raw material pulp is immersed in an alkali hydroxide aqueous solution having a concentration of 10 to 60% by weight and then squeezed to produce an excess. Obtained by removing the aqueous alkali hydroxide solution, the alkali hydroxide content is 0.01 to 0.20 and the water content is 0.1 to 2.0 in weight ratio to cellulose.
Using alkali cellulose in the range of 50 to 90
It is characterized in that propylene oxide having a weight ratio to cellulose of 2.0 to 3.5 at 0 ° C. is reacted in such a manner that it is continuously administered little by little into the reaction system.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The hydroxypropyl cellulose of the present invention has a hydroxypropyl group substitution mole number (MS) per anhydroglucose unit which is a structural unit of 2 to 3, preferably 2.5 to 2.8.
The composition ratio of the substitution products having different hydroxypropyl group substitution mole numbers in hydroxypropyl cellulose is the sum of the proportions of the substitution products having a hydroxypropyl group substitution mole number 2 and a hydroxypropyl group substitution mole number 3 Is 80 mol% or more, preferably 85 mol% or more, and the substitution ratio of hydroxypropyl group-substituted mol number 3 is 65 m.
ol% or more, preferably 75 mol% or more, and the ratio of non-substituted compound is 3 mol% or less, preferably 1.5 mol%
Hereafter, the ratio of substitution products having a hydroxypropyl group substitution mol number of 4 is 6 mol% or less, preferably 4 mol% or less.

If it is out of the above range, satisfactory physical properties cannot be obtained. If the sum of the ratios of the substitution product having 2 moles of hydroxypropyl group substitution and the substitution product having 3 moles of hydroxypropyl group substitution is 80 mol% or less, there is a problem in the properties of the solution and the solubility in water and an organic solvent is insufficient. To do. In addition, when the substitution ratio of hydroxypropyl group substitution mol number 3 is 65 mol% or less, the solubility in water and an organic solvent is insufficient, and in particular, the transparency of the solution when dissolved in water and an organic solvent is sufficiently obtained. Absent. When the ratio of the non-substituted compound exceeds 3 mol%, the properties of the solution, especially the solubility in the organic solvent are insufficient. Further, when the substitution ratio of hydroxypropyl group substitution mol number 4 is larger than 6 mol%, blocking occurs and the thermoplastic temperature becomes low.

The hydroxypropyl cellulose of the present invention can be produced, for example, according to the following procedure.
In the first step, the cellulose is treated with alkali hydroxide to prepare alkali cellulose. Alkali hydroxide in alkali cellulose plays an important role as a catalyst for the reaction of propylene oxide, and also has a role of increasing the reactivity of cellulose and activating it. On the other hand, water in alkaline cellulose is undesirable because it reacts with propylene oxide to produce impurities that must be removed from the product. Therefore, in order to effectively obtain hydroxypropyl cellulose by the reaction of alkali cellulose and propylene oxide, in the preparation of alkali cellulose, the amount of alkali hydroxide in the alkali cellulose and the amount of water to obtain a target substitution degree. Need to control.

In obtaining the substitution product composition of the hydroxypropyl cellulose of the present invention, it is important to control the amount of alkali hydroxide and the amount of water in the alkali cellulose,
Alkali hydroxide amount 0.01 by weight ratio to cellulose
To 0.20, preferably 0.05 to 0.10, and a water content of 0.1 to 2.0, preferably 0.3 to 1.0. If the amount is out of this range, the desired composition ratio cannot be obtained. When the amount of alkali hydroxide is less than 0.01 by weight with respect to cellulose, the reaction does not proceed sufficiently, and when it is more than 0.20, the ratio of substitution product of hydroxypropyl group-substituted mole number 4 in hydroxypropylcellulose. Tends to be more than 6 mol%. When the weight ratio of water content to cellulose is less than 0.1, the reaction does not proceed sufficiently, and when it exceeds 2.0, water reacts with propylene oxide to increase the production of undesirable impurities. As a result, a desired amount of hydroxypropyl group substitution cannot be obtained.

As a method for preparing alkali cellulose,
A preferred method is to immerse the raw material pulp in an aqueous alkali hydroxide solution, squeeze it to remove the excess aqueous alkali hydroxide solution, and wash or dry it as necessary to obtain the above-mentioned alkali cellulose composition. Other methods for preparing alkali cellulose include a method of mixing pulp with an aqueous alkali hydroxide solution in a dispersion solvent such as an organic solvent, and a method of directly spraying an aqueous alkali hydroxide solution on pulverized pulp. The composition is more inhomogeneous than alkali cellulose obtained by immersing in an alkaline aqueous solution, the subsequent etherification reaction does not proceed uniformly, and hydroxypropyl cellulose having the intended substitution product composition cannot be obtained.

The cellulose raw material used in the present invention is not particularly limited in terms of molecular weight and the like, and any of wood pulp, cotton linter and the like can be used, and it is limited by a shape such as a sheet-like material or a pulverized and powdered material. Instead, either one can be used.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like are used, and sodium hydroxide is preferred. Alkali hydroxide is used as an aqueous solution, but its concentration is 10% by weight.
As described above, the content is preferably 20 to 60% by weight, and when it is lower than 10% by weight, the cellulose does not swell sufficiently and the reaction with the following propylene oxide is difficult to proceed.

In the second step in the production of hydroxypropyl cellulose of the present invention, alkali cellulose and propylene oxide are sufficiently mixed and reacted. Temperature 5
The reaction is carried out at 0 to 90 ° C., preferably 70 to 80 ° C., by a method in which 2.0 to 3.5 by weight ratio of propylene oxide to cellulose is continuously administered little by little into the reaction system.

If the reaction temperature is lower than 50 ° C., the progress of the reaction is extremely slow and it takes a long time, so that it cannot be said to be practical. If the reaction temperature is higher than 90 ° C., the number of moles of hydroxypropyl group substitution in hydroxypropyl cellulose is 4 It is not preferable because the ratio of the substitution product is increased and the impurities produced by the reaction of propylene oxide with water increase. Further, at a high temperature of more than 90 ° C., the reaction with propylene oxide rapidly progresses, making it difficult to control the reaction and causing an abnormal temperature rise, which is a safety problem.

If the amount of propylene oxide added is less than the above amount, the ratio of the non-substituted product in hydroxypropyl cellulose increases, and conversely, if the added amount is more than the above, the ratio of the substituted product of hydroxypropyl group-substituted mole number 4 increases. The desired ratio of substitutes cannot be obtained.

As a method of adding propylene oxide, small doses are continuously administered. The rate of addition of propylene oxide is set according to the etherification reaction rate so that the amount of propylene oxide in the reaction system is as constant as possible. Generally, the reaction rate varies depending on the reaction temperature, and is higher when the reaction temperature is higher and slower when the reaction temperature is lower, so that there is an addition rate corresponding to the reaction temperature. If this is too fast, the concentration of propylene oxide in the reaction system becomes high, which may cause abnormal temperature rise. Also, if it is slow, the reaction time becomes unnecessarily long. By carrying out the method of continuously adding the amount corresponding to the amount of propylene oxide consumed by the reaction, good physical properties are secured, and the reaction can be completed safely and in a short time. For example, the preferable temperature condition is 70 to 80.
In the case of carrying out the reaction at a temperature of ℃, 2.0 to 3.5 by weight ratio of propylene oxide to cellulose is added to the reaction system within 4 to 4.
Administration is performed continuously for 6 hours and at a constant addition rate. On the other hand, the method of adding a predetermined amount of propylene oxide at one time is not preferable because the ratio of the substitution product of hydroxypropyl group-substituted mole number 4 in hydroxypropyl cellulose increases, and a large amount of propylene oxide is reacted at a time. Addition to the system has a risk of causing a runaway reaction, which is not preferable in terms of safety.

This reaction can also be carried out using an organic solvent having a low reactivity with propylene oxide as a dispersion medium.

The reaction product in the present invention contains impurities and the like produced by the reaction of propylene oxide and water, but it is easily purified by treating in hot water at 50 ° C. or higher, and the impurities are removed after drying. It is obtained as high-purity hydroxypropyl cellulose that does not contain.

The substitution composition of hydroxypropylcellulose obtained according to the present invention can be prepared by known methods, for example Carb.
hydro.Res., vol. 170, p.207 (1987). As an example of the method for measuring the composition of the substitution product, hydroxypropylcellulose in which a free hydroxyl group is methylated by reacting with a methylating agent such as iodomethane in the presence of alkali is acid-decomposed with trifluoroacetic acid or the like and then reduced to give sorbitol Use as a derivative. By subjecting the product acetylated with acetic anhydride or the like to gas chromatography, those having different substitution numbers and substitution positions of hydroxypropyl groups are separated, and the respective ratios can be determined.

According to the above-mentioned method, the hydroxypropyl cellulose of the present invention is MS2 to MS3, and the substitution product composition is a ratio of the substitution product having a hydroxypropyl group substitution mol number of 2 and the substitution product having a hydroxypropyl group substitution mol number of three. Is 80 mol% or more and the number of moles of hydroxypropyl group substitution is 3
The substitution product ratio is 65 mol% or more, the non-substitution product ratio is 3 mol% or less, and the hydroxypropyl group-substituted mole number is 4
Has a substitution ratio of 6 mol% or less, is completely dissolved in water, and has methanol, ethanol, isopropanol,
Methyl cellosolve, ethyl cellosolve, chloroform,
It also dissolved in many organic solvents such as dichloromethane, dioxane, tetrahydrofuran, dimethylsulfoxide, and showed high transparency. In addition, a product obtained by crushing the present invention into a powder form or a product formed into a film using the product of the present invention does not cause blocking even under high humidity, so that a stable product form can be maintained. Met.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the description of these examples or comparative examples.

Example 1 (1) Production of Hydroxypropyl Cellulose 100 parts by weight of powdered pulp was immersed in a 20% by weight aqueous sodium hydroxide solution at room temperature for 1 hour. Excess sodium hydroxide aqueous solution was removed by pressure filtration, and the weight ratio to cellulose was 0.1% alkali hydroxide and 0.
5 of alkali cellulose was obtained. In an autoclave equipped with an internal stirrer, 160 parts by weight of the above-mentioned alkali cellulose was charged, and 240 parts by weight of propylene oxide was added over 5 hours while stirring at a temperature of 70 to 80 ° C. Further, the same temperature was maintained for 2 hours to complete the reaction.
The reaction product was neutralized with acetic acid and washed with warm water of 50 to 60 ° C. Blow drying at 80 ° C. gave 195 parts by weight of colorless solid hydroxypropyl cellulose. MS determined by Zeisel method was 2.7.

(2) Substituted composition 3 parts by weight of the hydroxypropyl cellulose obtained in (1) was dissolved in 250 parts by weight of dimethyl sulfoxide.
To this solution, 30 parts by weight of powdered sodium hydroxide was added, and then 100 parts by weight of methyl iodide was added with stirring to obtain 6 parts.
The reaction was performed at 0 ° C. for 4 hours. The reaction product was poured into 1000 parts by weight of hot water to crystallize methylated hydroxypropyl cellulose. The crystallized product was collected and dried at 70 ° C. for 6 hours. Methylated hydroxypropyl cellulose obtained 5
After adding 300 parts by weight of a 2 mol% trifluoroacetic acid aqueous solution to the parts by weight and treating at 120 ° C. for 3 hours, the pH was adjusted to 7 using barium carbonate. To this, 1.5 parts by weight of sodium borohydride was added and stirred at room temperature for 1 hour, then 10
Evaporated to dryness at 0 ° C. 100 ml of acetic anhydride was added to the remaining contents.
Parts by weight and 200 parts by weight of pyridine were added, and the mixture was treated at 120 ° C. for 3 hours. After cooling, what was added with 500 parts by weight of water was extracted twice with 50 parts by weight of carbon tetrachloride. Carbon tetrachloride was evaporated and the residue was subjected to GC (gas chromatograph) analysis. Table 1 shows the results of determining the composition ratio of each substitution product from the peak area on the GC analysis.

(3) Physical Properties of Solution and Solid Properties The hydroxypropylcellulose obtained in (1) was dissolved in water and ethanol to prepare 2% by weight solutions, and blanks were prepared using a photoelectric colorimeter (5E type). The transmittance of visible light to (each of water and ethanol) was measured.

This hydroxypropyl cellulose was pulverized and allowed to stand in a powder having an average particle size of 100 μm at 25 ° C. in an atmosphere of relative humidity of 75% RH, and the equilibrium moisture absorption was measured and the aggregated state was visually observed.

The hydroxypropyl cellulose was dissolved in dimethylformamide, cast on a glass plate and dried at 100 ° C. for 2 hours and then at 120 ° C. for 2 hours to prepare a film having a thickness of about 50 μm. The film was cut into a 3 mm x 10 mm strip to make a test piece,
The softening temperature was measured using a thermomechanical analyzer (TMA; manufactured by Seiko Denshi KK). Table 1 shows the above measurement results.

Example 2 Sheet-shaped pulp 10 was used in place of 100 parts by weight of powder pulp.
It was prepared by immersing in 0% by weight of a 20% by weight aqueous sodium hydroxide solution at room temperature for 1 hour, squeezing to remove excess aqueous sodium hydroxide solution, further immersing in hot water at 40 ° C., squeezing and crushing. In the same manner as in (1) of Example 1 except that powdered alkali cellulose having a weight ratio to cellulose of 0.1 and a water content of 0.5 was used, 191 weight of hydroxypropyl cellulose was obtained. I got a part. MS value was 2.7. The substituent composition, solution physical properties, solid physical properties, etc. of this product were determined in Example 1.
The results obtained by the same method as in Table 1 are shown in Table 1.

Example 3 201 parts by weight of hydroxypropyl cellulose was obtained by the same procedure as in (1) of Example 1 except that an autoclave equipped with an internal stirrer was charged with 500 parts by weight of alkali cellulose and hexane. MS value was 2.8. Table 1 shows the results of the substituent composition, solution physical properties, solid physical properties, etc. of this product determined in the same manner as in Example 1.

Comparative Example 1 100 parts by weight of powder pulp was stirred at room temperature for 17 hours.
Example 1 was repeated except that 60 parts by weight of an aqueous solution of sodium hydroxide having a concentration by weight of 50% by weight was used, and powdery alkaline cellulose having a weight ratio to cellulose of 0.1 alkali hydroxide and 0.5 water was used. Manufacture was performed in the same manner as in (1) to obtain 196 parts by weight of hydroxypropyl cellulose. MS value was 2.6. Table 1 shows the results of the substituent composition, solution physical properties, solid physical properties, etc. of this product determined in the same manner as in Example 1.

Comparative Example 2 Hydroxypropyl cellulose was prepared in the same manner as in (1) of Example 1 except that 300 parts by weight of propylene oxide and the whole amount of propylene oxide were added simultaneously with the alkali cellulose and the reaction was carried out at 70 to 80 ° C. for 7 hours. 202 parts by weight were obtained. MS value was 2.8. Table 1 shows the results of the substituent composition, solution physical properties, solid physical properties, etc. of this product determined in the same manner as in Example 1.

Comparative Example 3 Reaction of alkali cellulose with propylene oxide
An attempt was made to produce hydroxypropylcellulose by the same method as in (1) of Example 1 except that the temperature was set to 00 ° C. Since the reaction temperature rose to 140 to 160 ° C on the way, the supply of propylene oxide was temporarily stopped, but it was difficult to control the reaction temperature to 100 ° C.
The MS value of the obtained 195 parts by weight of hydroxypropyl cellulose was 2.6. Table 1 shows the results of the substituent composition, solution physical properties, solid physical properties, etc. of this product determined in the same manner as in Example 1.

Comparative Example 4 Reaction of alkali cellulose with propylene oxide
(1) of Example 1 except that it was carried out under the temperature condition of 0 ° C.
An attempt was made to produce hydroxypropyl cellulose by a method similar to. The MS value of the obtained 195 parts by weight of hydroxypropyl cellulose was 1.5. Table 1 shows the results of the substituent composition, solution physical properties, solid physical properties, etc. of this product determined in the same manner as in Example 1.

[0037]

[Table 1] 1) Zeisel method 2) GC measurement conditions Equipment: Hewlett Packard
5980SERIES II Gas Chromatograph Column: 5% Phenylmethylsilicone 0.2mmφ × 25m Sample: 1μ1 Temperature of injector and detector: 250 ℃ Oven temperature: Raise from 170 ℃ to 300 ℃ (Raising rate: 2.5
℃ / min) 3) Viscosity: Ubbelohde viscometer (20 ℃) Translucency: Photoelectric colorimeter 5E type, 20mm cell, visible light (20
℃) 4) 75% RH, 25 ℃ Visually graded in 5 levels 1: Powder, 2: Partially blocked, 3: Half blocked, 4: Largely blocked, 5: Completely blocked (aggregation) heat Mechanical analyzer: TMA (manufactured by Seiko Denshi), heating rate
10 ° C / min

[0038]

EFFECTS OF THE INVENTION According to the present invention, the hydroxypropyl cellulose of the present invention has a controlled compositional ratio of substitution products having a different number of moles of hydroxypropyl group substitution compared to conventional hydroxypropyl cellulose. By lowering the ratio of the substitution product and the highly substitution product having a hydroxypropyl group substitution mol number of 4 or more, it is possible to provide a stable product having excellent solution properties and no blocking.

Claims (2)

[Claims] 1. A hydroxypropyl cellulose obtained by reacting alkali cellulose with propylene oxide, wherein the average substitution mole number of hydroxypropyl groups per anhydroglucose unit is 2-3, and The total ratio of the substitution product having 2 moles of hydroxypropyl group substitution and the substitution product having 3 moles of hydroxypropyl group substitution is 80 mol% or more, and the substitution product ratio of 3 substitution moles of hydroxypropyl group is 65 mol.
% Or more and the ratio of the non-substitution product is 3 mol% or less, and the substitution product ratio of hydroxypropyl group substitution mol number 4 is 6 mol%
The following is hydroxypropyl cellulose. 2. A raw material pulp is dipped in an alkali hydroxide aqueous solution having a concentration of 10 to 60% by weight and then pressed to remove an excess alkali hydroxide aqueous solution. Using alkali cellulose having a range of 01 to 0.20 and a water content of 0.1 to 2.0, a reaction system was used to prepare propylene oxide at a weight ratio to cellulose of 2.0 to 3.5 at a temperature of 50 to 90 ° C. The method for producing hydroxypropyl cellulose according to claim 1, wherein the reaction is carried out by a method in which a small amount is continuously administered.