JP2991038B2 - Manufacturing method of dyed paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing dyed paper, and more particularly, to a method of fixing dyes and pigments (both are collectively referred to as "dyes and pigments" in the present specification) to paper, which is excellent in fixing. The present invention relates to a new and improved method for producing dyed paper which can be dyed and can be easily dyed in various hues.

[0002]

2. Description of the Related Art Dyeed paper can be roughly classified into two types: one in which the entire paper is uniformly dyed with a single color, and the other in which a partially different color is applied and a dye pattern is distributed. When manufacturing the former dyed paper, the most required is to fix the dye and pigment uniformly on the paper pulp, which is the main material constituting the paper.

[0003] As dyes and pigments used for dyeing paper, acid dyes, basic dyes, direct dyes, inorganic or organic pigments and the like are typically used. In many cases, several kinds of dyes and pigments are mixed and used to obtain a desired hue.

However, the affinity for papermaking pulp differs depending on the type of dye and pigment. Further, as papermaking pulp, pulp of different types such as softwood pulp and hardwood pulp is often used in combination. Also differ in affinity with dyes and pigments. Due to these causes, a phenomenon called "selective dyeing" or "granifying" in which paper pulp is unevenly dyed is likely to occur, and this phenomenon should be avoided when uniform dyeing is applied to paper. More important than anything else.

[0005] In order to prevent such a phenomenon, the temperature of the dye / pigment added to the paper stock should be lowered as much as possible, the concentration of the dye / pigment should be lowered, the dye / pigment should be added to the paper stock promptly, Conventionally, measures such as devising the color are adopted, but since these operations require a high degree of skill, a simpler method of color matching is currently being sought.

Considering the reasons why a high level of skill and skill are required for color matching as described above, it can be said that the fixation of dyes and pigments on paper pulp slightly changes depending on the conditions. .

In the past, measures have been taken to uniformly fix the dyes and pigments on paper pulp. As one of them, the addition of dyes and pigments to paper stock and the addition of chemicals such as sizing agents and fixing agents (such as aluminum sulfate) can be carried out by using a pulper, a refiner, a beater, a mixing engine, and the like, with sufficient fixing time. Is going.
Further, there has been adopted a method in which various dyeing assistants are used in combination with the dye / pigment to improve the fixability of the dye / pigment to paper pulp. Examples of the dyeing assistant include a dyeing aid such as sodium chloride and sodium sulfate (Glauber's salt), and a fixing agent such as a quaternary ammonium salt, a pyridium salt, a dicyandiamide / formaldehyde condensate, and a polyamine-based polymer. JP-B-46-40510 discloses a method of improving the fixability of an acid dye by treating a cellulosic fiber such as pulp for papermaking with a compound having a quaternary ammonium base. In each of the above-mentioned publications, it is proposed to improve the fixability by using a compound having a quaternary ammonium base as a fixing agent for a direct dye.

[0008]

The above-mentioned methods for achieving a uniform fixation of dyes and pigments on paper pulp are not always satisfactory.

That is, in a method of sufficiently fixing a dye or pigment to papermaking pulp using a pulper, a refiner, a beater, a mixing engine, or the like, it takes a long time to perform color matching. Therefore, it is almost impossible to produce dyed papers having different hues one by one using the same paper machine one after another.

In the method of improving the fixability of dyes and pigments by chemical means in combination with a dyeing aid, if a large amount of dyeing aid is used in order to improve the fixability, pulp fibers forming paper This causes problems that the formation of the paper becomes extremely poor and the strength of the paper is significantly reduced. Further, there is a problem that the light fastness is deteriorated due to the interaction between the dye / pigment and the dyeing assistant, and the color of the paper is changed in several weeks to several months.

Furthermore, if the dyes and pigments used in the production of dyed paper are expensive and if the fixability of the dyes and pigments to the papermaking pulp is low, the dyes and pigments flow into the wastewater, so that the treatment of the wastewater becomes a problem. From the viewpoint of improving the fixability of dyes and pigments on paper pulp, it is a great technical problem.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks in the conventional method for producing dyed paper, and specifically, it is delicate and requires skill in fixing dyes and pigments to pulp for papermaking. It is an object of the present invention to provide a method capable of achieving extremely high fixing without requiring a complicated operation and producing a dyed paper without deterioration of paper formation or deterioration of light fastness by using a large amount of a dyeing assistant.

Another object of the present invention is to enable color matching to obtain a desired hue easily and in a short time, and to efficiently produce dyed paper having different hues little by little using the same paper machine. It is an object of the present invention to provide a method for producing dyed paper that can be used.

[0014]

Means for Solving the Problems As a result of intensive studies, the present inventors have dyed fine fibrillated cellulose of a specific size with a dye / pigment, thereby obtaining fine fibrillated cellulose carrying the dye / pigment, ie, A dye / pigment carrier is prepared in advance, and this dye / pigment carrier is added to papermaking pulp to make paper, and it is found that the papermaking pulp can be dyed as if it were uniformly dyed. Completed the invention.

That is, the method for producing a dyed paper according to the present invention has a number average fiber length of 0.05 to 0.3 mm and an axial ratio of 50 to 50.
As described above, a dye / pigment carrier in which a dye / pigment is supported on fine fibrillated cellulose having a water retention value of 250% or more,
The method is characterized in that papermaking pulp is added to a stock prepared as a main material and mixed, and then the stock is made.

In the present invention, the fine fibrillated cellulose pre-loaded with the dye / pigment is finely divided to the microfibril dimension by breaking the binding of the fibrils forming the cell wall of the pulp fiber by a strong mechanical shearing force or the like. In particular, in the present invention, it is necessary to use fine fibrillated cellulose having a number average fiber length of 0.05 to 0.3 mm, an axial ratio of 50 or more, and a water retention value of 250% or more. .

The number average fiber length is obtained by integrating the total length of the fibers present in a certain pulp suspension among the data measured with a fiber length measuring machine (model FS-200) manufactured by KAJAANI (Finland). Indicates the value divided by the number. The hardwood bleached kraft pulp and softwood bleached kraft pulp, which are the raw materials for ordinary paper, have a number average fiber length of about 0.5 mm and 1 mm, respectively, and even fibrillated fibers generated by beating are averaged. The minimum fiber length is about 0.35 mm.

The number average fiber length of the fine fibrillated cellulose is related to uniform dyeing without uneven dyeing. From this viewpoint, in the present invention, the number average fiber length is 0.05 to 0.3 m.
Use microfibrillated cellulose in the range of m. The present inventors prepared a dye / pigment carrier by pre-dyeing various fine fibrillated celluloses having different fiber lengths, and added the dye / pigment carrier to undyed unbeaten paper pulp for dyeing. The dyeing condition of the paper was examined. As a result, the number average fiber length is 0.05 to
In a dyed paper obtained using a dye / pigment carrier dyeing 0.3 mm fine fibrillated cellulose, the dye / pigment carrier in the dyed paper is so small as to be invisible to the eye, so that the dyed paper is uniformly dyed as a whole. I confirmed that I could see it. When a dye / pigment carrier made of fine fibrillated cellulose having a number average fiber length of more than 0.3 mm is used, the dye / pigment carrier is too large and can be visually identified in dyed paper, and the uniformity of dyeing is reduced. . 0.
In the case of a dye / pigment carrier made of fine fibrillated cellulose having a size of less than 05 mm, the dye / pigment carrier is too small, and the ratio of the dye / pigment flowing out of the paper net during the papermaking of the dyed paper increases.

The axial ratio of the fine fibrillated cellulose is a value calculated by fiber length / fiber width. The fiber width is measured from an electron micrograph, and the fiber length is defined as a number average fiber length obtained from a fiber length measuring machine. Obtained by calculation. The axial ratio in the present invention indicates an average value for all the fine fibrillated celluloses, and a larger value indicates that there are more fine and long fibers. In the case of fine fibrillated cellulose having an axis ratio of less than 50, the ratio of the obtained dye / pigment carrier flowing out of the paper net at the time of dyeing paper making becomes large. On the other hand, the upper limit of the axial ratio is not particularly limited. For example, even if the axial ratio is about 2,000, the fiber width is very narrow, so that even if the obtained dye / pigment carrier is mixed in the dyed paper, it can be visually identified. Can not.

The water retention value of the fine fibrillated cellulose is an index of the degree of swelling of the pulp. The water retained in the swollen fibers and the free water existing in the fibers and between the fibers are separated by an appropriate centrifugal force. It is a value measured based on the idea that it can be distinguished. The water retention value specified in the present invention is based on the same concept and is based on JAPAN TAPPI No.
26 is a value measured by the method indicated in FIG. That is, a mat of a predetermined amount of a sample is previously formed on a prescribed filter, dehydrated with a centrifugal separator at a centrifugal force of 3000 G for 15 minutes, and the amount of retained water is divided by the amount of absolutely dried pulp. Shows the value when. Normal unbeaten pulp shows a water retention value of only about 90%, and beaten pulp shows a water retention value of only about 200%. The water retention value of the microfibrillated cellulose is significantly related to the dispersibility of the paper pulp in the stock. When fine fibrillated cellulose having a water retention value of 250% or more is added to the stock, the papermaking pulp is uniformly dispersed in the stock even with a small addition amount of about 1% by weight. The formation can provide good formation even when using unbeaten papermaking pulp which is difficult to form. Further, the water retention value of the fine fibrillated cellulose is greatly related to the adsorptivity of the dye / pigment to the fine fibrillated cellulose, and the dye / pigment is well adsorbed to the fine fibrillated cellulose having a water retention value of 250% or more. .

Examples of the finely divided cellulose include cellulose powder in addition to finely fibrillated cellulose.
Cellulose powder is produced by subjecting cellulose to a chemical treatment to take out only crystal parts in the cellulose, and further mechanically pulverizing the cellulose to make it finer. Such cellulose powder has a number-average fiber length of about 0.1 mm, but has a low water retention value of about 50%. Therefore, even if a relatively large amount is added to the stock, it can be used in the papermaking pulp stock. Does not improve, and the adsorptivity of cellulose powder itself to dyes and pigments is low.

Various methods have been known as methods for producing fine fibrillated cellulose. In the present invention, fine fibrillated cellulose produced by any method has a predetermined number average fiber length, a predetermined axial Anything having a ratio and a water retention value can be used. For example, as a method for producing fine fibrillated cellulose by applying a mechanical shearing force to cellulose fibers, Japanese Patent Publication No.
A suspension of fibrous cellulose, as proposed in US Pat. No. 0-19921, is passed through a small diameter orifice and the suspension is given a high velocity with a pressure difference of at least 3000 psi, which is then impinged to rapidly A method in which a cutting action is performed by decelerating the fiber material, a method in which an impeller is rotated by a driving shaft with a bell, and an impact is applied to a fiber material as proposed in Japanese Patent Application Laid-Open No. 63-256787;
No. 2,907, a method of performing fine grinding by a rotor and a hammer disposed in a housing, a method using a medium stirring wet pulverizing apparatus as proposed in JP-A-3-163135, 6-1028
No. 7, a method using a vibrating mill pulverizer, a method using a fine pulverizer such as a sand mill proposed in JP-A-4-194097, and the like. Further, not only a mechanical treatment but also a method using a combination of a chemical treatment such as an acid hydrolysis treatment, an alkali treatment, a liquid ammonia treatment, an enzyme treatment, and a steam treatment and a mechanical treatment has been proposed.

Examples of the raw material of the fine fibrillated cellulose include chemical pulp such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulphite pulp (LBSP), softwood bleached sulphite pulp (NBSP) And groundwood pulp (GP),
Wood pulp such as mechanical pulp such as thermomechanical pulp (TMP) can be used. In addition, non-wood pulp such as cotton pulp, hemp, bagasse, kenaf, espart, mulberry, mitsumata, ganpi, and regenerated cellulose fiber can also be used. it can. By using fine fibrillated cellulose made of different raw materials, dyed papers having different textures can be obtained. The texture of the obtained dyed paper also varies depending on the degree of fineness of the microfibrillated cellulose used.

As dyes and pigments used for dyeing fine fibrillated cellulose, dyes and pigments conventionally used in the production of dyed paper can be similarly used. As the dye, for example, a basic dye, an acid dye, a direct dye, a fluorescent dye, a disperse dye,
Reactive dyes and the like are used. The types of pigments are not limited, and inorganic pigments containing metal oxides or sulfides as main components, and organic pigments made by adding a precipitant to a dissolved dye, which is generally called a lake, to make it insoluble are widely used. it can. Specific inorganic pigments include titanium white, carbon black, ultramarine blue, cadmium yellow, cadmium red, iron oxide, metal powder, and the like, and organic pigments include phthalocyanine, dyeing, soluble azo, and insoluble An azo type, a polyazo type and the like can be mentioned.

In order to prepare a dye / pigment carrier by carrying a dye / pigment on finely fibrillated cellulose, it is usually required to use 0.5
An aqueous solution or suspension of the dye / pigment may be added to an aqueous suspension containing about 6% by weight of fine fibrillated cellulose and stirred uniformly. In the case of a dye / pigment having a high affinity for the fine fibrillated cellulose, a relatively large amount of the dye / pigment can be supported per unit weight of the fine fibrillated cellulose without using a dyeing aid or the like. In the case of dyes and pigments having low affinity for fine fibrillated cellulose, fixing agents such as aluminum sulfate, accelerated dyes such as sodium chloride and sodium sulfate (Glauber's salt), quaternary ammonium salts, pyridium salts, dicyandiamide / formaldehyde condensation The amount of the dye / pigment carried on the fine fibrillated cellulose can be increased by appropriately using a dyeing aid such as a fixing agent such as a dye or a polyamine-based polymer. When the dyeing aid is used in combination, the amount of the dyeing aid may be small compared to the amount of the dyeing aid conventionally used for fixing the dye / pigment to the papermaking pulp.

Conventionally used pulp can also be used for the papermaking pulp which is the base of the dyed paper. For example, bleached hardwood kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulphite pulp (LBSP), softwood bleached sulphite pulp (NBS)
Wood pulp such as chemical pulp such as P) and mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP) can be used. Furthermore, cotton pulp, hemp, bagasse, kenaf, esparto, kozo, mitsumata, and ganpi Non-wood pulp can also be used. These pulp may be used alone or in combination of two or more kinds.
00 to 600 ml C.I. S. F. Beat it to use.

In order to dye a papermaking pulp in making a dyed paper according to the present invention, a dye / pigment carrier having fine fibrillated cellulose carrying a dye / pigment is simply added to the papermaking pulp stock and mixed. The dyeing and coloring carrier will be dyed by adsorption to the papermaking pulp. Therefore, it is not necessary to add a dyeing aid such as a fixing agent which has been conventionally used to improve the fixability of the dye / pigment to the pulp. Deterioration of light resistance can be eliminated.

In the dye / pigment carrier, the dye / pigment is well adsorbed by the finely fibrillated cellulose, and the yield of the dye / pigment carrier into the paper is very high. Become.

According to the present invention, in the step of adding the dye / pigment carrier to the papermaking pulp stock and fixing the dye / pigment carrier to the papermaking pulp, no special adjustment of the fixing time and fixing temperature is required. In particular, since the fixing time does not need to be considered, the color of the dye can be changed very easily and quickly. That is, in order to extend the fixing time as much as possible in conventional dyeing, pulpers, refiners, beaters, mixing engines and the like were used to add dyes and pigments to the stock, but in the present invention,
It is also possible to add a dye / pigment carrier to the stock at a location close to the wire part of the paper machine, for example at the headbox. As a result, it is possible to easily perform cleaning of the apparatus at the time of color change and change of paper stock conditions, thereby making it possible to cope with small lots and to easily perform color matching work such as complementary colors.

The amount of the dye / pigment carrier to be added to the paper stock is not particularly limited, and may be appropriately adjusted depending on the density of dyeing required for the obtained dyed paper. If the addition amount is too small, the effect of dyeing will not be observed. On the other hand, as the addition amount increases, the drainage during papermaking deteriorates. Therefore, when performing high-speed papermaking, it is not desirable to add too much. From such a viewpoint, it is generally preferable to add a dye / pigment carrier in the range of 0.01 to 10% by weight based on the solid content of all papermaking raw materials. In addition, the papermaking pulp in the stock to which the dye / pigment carrier is to be added is usually not dyed. By using pulp, the dyeing can be deepened.

As the paper machine for making the dyed paper according to the present invention, there can be used a conventionally used round paper machine, fourdrinier paper machine, inclined type paper machine, twin wire paper machine and the like. .

It is well known that the development of hue by dyes and pigments is governed by the principle of subtractive color mixing. According to the conventional method, for example, when it is desired to produce a green dyed paper, the paper pulp is dyed green using a combination of yellow and blue dyes and then made into a paper. On the other hand, in the present invention, the dyes and pigments of the three primary colors are prepared in advance by independently carrying the dyes and pigments of the three primary colors of yellow, red and blue on the fine fibrillated cellulose, and the dye and pigments of the three primary colors are prepared in advance. An arbitrary hue can be developed by mixing the carriers in an appropriate ratio. This closely resembles the principle of halftone dots in color printing, and when observed under a microscope, the size is so small that it is indistinguishable, despite the fact that there are actually dye-pigment carriers of independent hues. Therefore, it looks like a mixed color as a whole.

This will be further described with reference to an example of a triangle shown in the attached drawings. When the three primary colors of yellow, red, and blue are arranged at each point of the triangle, the mixed color of yellow and red becomes an orange hue existing on a straight line connecting yellow and red, and the mixed color of yellow and blue is yellow. And a blue-based hue existing on a straight line connecting blue and blue, and a mixed color of red and blue becomes a purple-based hue existing on a straight line connecting red and blue. Thus, by mixing the three types of dye / pigment carriers of the three primary colors in an appropriate ratio, all the hues shown in the triangle can be expressed. The center of the triangle turns gray or brown depending on the balance of yellow, red and blue hues.

[0034]

The present invention will be described below in detail with reference to Examples and Comparative Examples. All parts by weight and% by weight are based on the absolute dry weight.

Example 1 NB by mechanical shearing force using a high-pressure homogenizer
KP is refined, number average fiber length 0.07mm, axial ratio 20
0, a fine fibrillated cellulose having a water retention value of 400% was prepared. A red direct dye (C.I.D.) is added to the aqueous suspension of fine fibrillated cellulose (solid concentration: 1% by weight).
Direct Red 23) was added and mixed at 2% by weight based on the absolute dry weight of the finely fibrillated cellulose to prepare a dye carrier carrying a dye. Solid content of stock prepared using unbeaten NBKP as pulp for papermaking 9
2 parts by weight of the dye carrier obtained above was added to 8 parts by weight in the head box of a fourdrinier paper machine, and a dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

Example 2 Number average fiber length 0.18 mm, axial ratio 400, water retention value 360
% Dyed paper was prepared in the same manner as in Example 1 except that the fine fibrillated cellulose was used.

Example 3 A red pigment (CI Pigment R) was used as a dye.
A dyed paper was produced in the same manner as in Example 1 except that ed 48) was used.

Example 4 NB by mechanical shearing force using a high-pressure homogenizer
KP is refined, number average fiber length 0.07mm, axial ratio 20
0, a fine fibrillated cellulose having a water retention value of 400% was prepared. A red direct dye (C.I.D.) is added to the aqueous suspension of fine fibrillated cellulose (solid concentration: 1% by weight).
Direct Red 23) was added and mixed at 2% by weight based on the absolute dry weight of the finely fibrillated cellulose to prepare a dye carrier carrying a dye. To the stock prepared using unbeaten NBKP as the papermaking pulp, the same red direct dye as described above was added in an amount of 0.5% based on the absolute dry weight of NBKP.
% By weight and 4% by weight of aluminum sulfate as a fixing agent for the dye were added, and NBKP was dyed using a mixing engine. 2 parts by weight of the dye carrier obtained above was added to 98 parts by weight of the solid content of the stock containing the dyed NBKP obtained above in a head box of a fourdrinier paper machine, and then dried under normal press drying conditions. A dyed paper with an amount of 100 g / m ² was obtained.

Example 5 NB by mechanical shearing force using a high-pressure homogenizer
KP is refined, number average fiber length 0.07mm, axial ratio 20
0, a fine fibrillated cellulose having a water retention value of 400% was prepared. A red direct dye (C.I.D.) is added to the aqueous suspension of fine fibrillated cellulose (solid concentration: 1% by weight).
direct Red 23) was added and mixed in an amount of 2% by weight based on the absolute dry weight of the fine fibrillated cellulose to prepare a red dye carrier carrying a dye. Separately, a yellow direct dye (CI Direct Ye) is used.
A yellow dye carrier carrying a dye was prepared in the same manner except that llow 50) was used. As for the papermaking pulp, 2 parts by weight of the red dye carrier obtained above and 2 parts by weight of the yellow dye carrier obtained above were used for 96 parts by weight of the solid content of the stock prepared using a 1: 1 mixture of unbeaten NBKP and LBKP. And 2 parts by weight of the dye carrier are added in a head box of a fourdrinier paper machine.
A dyed paper of 0 g / m ² was made.

Example 6 Direct Yellow Dye (CI Direct Yellow)
50) and a blue dye (CI Direct B)
lu 236), respectively, except that a yellow dye carrier and a blue dye carrier each carrying
A dyed paper was produced in the same manner as in Example 5.

Example 7 In the same manner as in Example 5, a red direct dye (CI Di
Rect red 23), yellow direct dye (CI.
Red, yellow and blue dye carriers carrying Direct Yellow 50) and a blue direct dye (CI Direct Blue 236), respectively, were prepared. Unbeaten NBKP as pulp for papermaking
2 parts by weight of the above-obtained red dye carrier, 2 parts by weight of the yellow dye carrier, and blue based on 94 parts by weight of the solid content of the stock prepared by using a pulp obtained by mixing pulp containing 1: 1 and LBKP. Was added in a head box of a fourdrinier paper machine, and dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

COMPARATIVE EXAMPLE 1 0.04% by weight of a red direct dye (CI Direct Red 23) and 4 based on the solid content of a stock prepared using unbeaten NBKP as a paper pulp. By weight of aluminum sulfate (a fixing agent for dye) was added in a head box of a fourdrinier paper machine, and dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

Comparative Example 2 Water suspension of cellulose powder having a number average fiber length of 0.15 mm, an axial ratio of 20, and a water retention value of 80% (solid content concentration: 1% by weight)
In addition, a red direct dye (CI DirectRed 2)
3) 2% by weight based on the absolute dry weight of the cellulose powder
The mixture was added and mixed to prepare a cellulose powder carrying the dye. To 98 parts by weight of the solid content of the stock prepared by using unbeaten NBKP as the pulp for papermaking, 2 parts by weight of the dye-carrying cellulose powder obtained above was added in a head box of a fourdrinier paper machine. Then, a dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

Comparative Example 3 NBKP was beaten using a PFI mill to give a beaten NB having a number average fiber length of 0.35 mm, an axial ratio of 100, and a water retention value of 180%.
KP was prepared. A red pigment (CI Pig) was added to this beaten NBKP pulp slurry (solid content concentration 1% by weight).
(Ment Red 48) was added and mixed in an amount of 2% by weight based on the absolute dry weight of the beaten NBKP to prepare a pulp slurry carrying a pigment. Unbeaten NBKP as pulp for papermaking
For 98 parts by weight of the solid content of the stock prepared using
2 parts by weight of the pulp slurry supporting the pigment obtained above was added in a head box of a fourdrinier paper machine, and dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

Comparative Example 4 Unbeaten NBKP and LBKP were used as pulp for papermaking:
0.04% by weight based on the solid content of the stock prepared using the pulp mixed with CI
ect Red 23), 0.04% by weight of yellow direct dye (CI Direct Yellow 50),
0.04% by weight of a blue direct dye (CI Direc
t Blue 236) and 4% by weight of aluminum sulfate (fixing agent for dye) were added in a head box of a fourdrinier paper machine, and dyed paper having a basis weight of 100 g / m ² was formed under ordinary press drying conditions.

The dyed papers obtained in each of the above Examples and Comparative Examples were evaluated for dyeability, dye / pigment yield during papermaking, level dyeing, light fastness and formation. Each evaluation was performed by the method described below. 1) Dyeability: L * a specified in JIS Z 8729
The evaluation was performed according to the method of displaying the object color using the * b * color system. L * is a lightness index, and a * and b * are chromaticness indices. 2) Dye / pigment yield: The absorbance of the dewatered waste liquid during papermaking was measured, and converted to a concentration from a calibration curve prepared in advance to obtain 1%.
00- (Dye / pigment concentration of dewatered waste liquid / added dye / pigment concentration)
× 100. 3) Leveling property: は indicates a level at which the dye is uniformly dyed by visual inspection, Δ indicates a level at which uneven dyeing can be confirmed, and X indicates a level at which marked uneven dyeing is observed. 4) Light fastness: The evaluation criteria of discoloration and fading were indicated by grades based on JIS L0801. The higher the grade, the lower the degree of discoloration. 5) Formation: ○ indicates a level at which flocs are not conspicuous when the sheet is visually judged by transmitted light, Δ indicates a level at which flocs are slightly conspicuous, and X indicates a level at which flocs are very conspicuous. Table 1 shows the results of the evaluation.

[0047]

As can be seen from the results shown in Table 1, fine fibrillated cellulose supporting the dye / pigment is prepared in advance, and this is added to the stock of the paper pulp used as the base material to thereby improve the yield of the dye / pigment. Highly uniform dyed paper can be obtained. Furthermore, since it is not necessary to use a dyeing aid for improving the fixability of the dye / pigment, the light resistance of the dyed paper is increased, and the formation of the dyed paper is improved by the water retention and dispersion effects of the fine fibrillated cellulose.

As can be seen from the comparison between the results of Examples 1 and 2 and Comparative Example 1, when only the dye was added to the stock in the head box, the dye yield was very low, whereas The dye yield can be increased by adding the supported fine fibrillated cellulose. Also, in the case of the dyed paper thus produced, in Examples 1 and 2, L *, which is an index of lightness, is smaller, and a, which is an index of redness, is a.
It can be seen that the color is very deep from the fact that * is large.

Further, as in Examples 1 and 2, the number average fiber length is 0.03 mm or less, the axial ratio is 50 or more, and the water retention value is 2 or more.
When the fine fibrillated cellulose having a content of 50% or more is used, the above-described excellent effects are exhibited, whereas the axial ratio is small, the water retention value is low, or the fiber length is high as in Comparative Examples 2 and 3. When cellulose powder or beaten pulp having a long particle size is used, the dye yield is low, and uneven dyeing and formation tend to be observed.

Even when a pigment is used as in Example 3, the same effect as that of the dye can be obtained, and a dyed paper having high light fastness can be obtained, especially reflecting the properties of the pigment. By pre-dyeing the base paper pulp as in Example 4, since L * is smaller and a * is larger than in Example 1, the dyed paper that has been dyed deeper and more vividly can be obtained. It can be confirmed that it can be obtained.

As is apparent from Examples 5 to 7,
It can be seen that any color can be expressed by mixing finely fibrillated cellulose, such as yellow or blue, which has been separately dyed. On the other hand, when dyes of various colors were directly added to paper pulp and dyed as in Comparative Example 4,
Defects such as the occurrence of a granulating phenomenon on the dyed paper, a tendency to slightly uneven dyeing, and a very low dye yield are observed.

[0053]

According to the present invention, a dye / pigment carrier in which a dye / pigment is carried on fine fibrillated cellulose of a specific size is prepared in advance, and this is added to a base paper pulp stock and mixed. Since this is a method for producing dyed paper, the following effects can be obtained.

1) Since the fine fibrillated cellulose carrying the dye and pigment adsorbs on the pulp fibers for papermaking, a color is developed. Therefore, a complicated device for dyeing the paper as in the conventional method, for example, the order of addition and addition of chemicals. Location, fixing time,
It is not necessary to consider the fixing temperature, the selection of the dyeing aid, and the like. 2) The yield of the dye / pigment into the paper is extremely high, and the amount of the dye / pigment flowing out into the drainage can be suppressed. 3) For example, a dye paper of any various hues can be easily manufactured by preparing dye / pigment carriers individually dyed, for example, red, blue and yellow, respectively, and appropriately mixing them. 4) Since the dye / pigment carrier can be added near a wire part such as a head box of a paper machine, the color can be easily changed, and a small amount of dyed paper having a different hue can be produced one after another. 5) It is not necessary to use a dyeing aid, and even when it is used, a very small amount is required, so that a dyed paper having high light resistance can be obtained. 6) Due to the water retention effect and dispersing effect of the fine fibrillated cellulose, a dyed paper with good formation can be obtained.

[Brief description of the drawings]

FIG. 1 is a triangular explanatory diagram for explaining the principle of subtractive color mixing of three primary colors of yellow, red and blue of a dye / pigment.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mariko Hirose 501, Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Inside Special Paper Manufacturing Co., Ltd. (58) Investigated field (Int.Cl. ⁶ , DB name) D21H 21/28 D21H 15/02

Claims (3)

(57) [Claims] Claims: 1. A number average fiber length of 0.05 to 0.3 mm,
A dye / pigment carrier obtained by supporting a dye / pigment on fine fibrillated cellulose having an axial ratio of 50 or more and a water retention value of 250% or more is added to a stock prepared from papermaking pulp as a main material and mixed. A method for producing dyed paper, which comprises making the stock. 2. The method for producing dyed paper according to claim 1, wherein two or more different color / pigment carriers are mixed and added to the stock. 3. The method for producing dyed paper according to claim 1, wherein the papermaking pulp is a papermaking pulp previously dyed with a dye or pigment.