JP3421446B2 - Method for producing powder-containing paper - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a powder-containing paper which has less deterioration in paper strength as compared with the conventional method, improves the yield of powder, has no problem in drainage during papermaking, and can be produced in a stable state. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art To improve printability, smoothness, and optical properties such as opacity and whiteness, it is not possible to fill paper with powder such as kaolin, calcium carbonate, titanium dioxide, clay and talc. It is widely practiced. As one of the methods for efficiently retaining the powder in the paper, polyvalent metal ions such as sulfuric acid band (aluminum sulfate), polyacrylic amide, cationic starch, dialdehyde starch, polyamine polyamide during preparation of the stock material. Various chemicals such as organic polymer compounds such as epichlorohydrin are added.

On the other hand, recently, with the increase in the size of paper machines at high speed and the progress of neutral papermaking, the demand for improving the yield of powder has been increasing, and various dual systems have been proposed. The dual system is a papermaking method in which two or more types of flocculants are combined to form strong flocs of cellulose fibers and powders to improve the powder yield. For example, the combination of cationic starch and colloidal silicic acid, the combination of guar gum and colloidal silicic acid, the combination of cationic polyacrylamide and colloid as proposed in JP-A-57-51900 and JP-A-62-15391. Combination of crystalline silicic acid, combination of cationic polyacrylamide and modified bentonite as proposed in JP-A-62-191598, combination of amphoteric polyacrylamide and aluminum compound, combination of polyethylene oxide and special phenol resin, polyethylene oxide And a bentonite, an anionic polyacrylamide, a bentonite, a polyethyleneimine, and a polyacrylamide are known.

In addition to the method of adding a chemical, there is a method of improving the yield of powder by smashing the pulp for papermaking to make the fibers into fibrils. This is a method of increasing the specific surface area of pulp fibers, increasing the contact area with the powder, and improving the powder yield. The powder is also captured by the network formed by fibrils during papermaking. Among the methods of promoting beating, attention has recently been paid to the properties of finely fibrillated cellulose that has been extremely advanced. The fine fibrillated cellulose gives mechanical pulp shear force to the pulp for paper making, and the fiber width is 1 μm.
It is an extremely beaten fiber having a fiber length of m or less and a fiber length of several tens to several hundreds μm, and its specific surface area is several hundred times that of an unbeaten pulp fiber. Japanese Patent Application Laid-Open No. 60-81398 and Japanese Patent Application Laid-Open No. 60-81398 show examples in which the fine fibrillated cellulose is added to a pulp for papermaking in an amount of several% to exhibit an excellent effect as a yield improving agent in the case of making powder-containing paper. -8139
9 and JP-A-60-88199.

[0005]

The above-mentioned method has hitherto been carried out as a method for improving the powder yield, but there are also a number of problems. In the method of adding various chemicals, if the amount used is increased, the charge balance of the entire dispersion system is broken,
May cause excessive aggregation. Although the powder yield (one-pass retention) is improved by the strong aggregation, there is a problem that the texture is poor or the paper quality is stiff, and the original texture of the paper is impaired. Even if the yield of powder is improved by chemicals, as the filling ratio of powder increases, the added powder inhibits the formation of interfiber bonds, resulting in a significant decrease in strength, especially tensile strength. There are also points.

In addition, in the method of adding fine fibrillated cellulose, the drainage becomes worse as the amount of fine fibrillated cellulose added increases, and water drainage in the wire part of the paper machine worsens, causing problems such as paper breakage. I know that. Compared with the conventional method, the present invention has less paper strength reduction, does not disturb the texture of the paper, etc., improves the yield of powder, has good drainage at the time of papermaking, and can be stably produced. The present invention newly provides a method for producing body-containing paper.

[0007]

Means for Solving the Problems The present inventors have paid attention to the powder yield improvement effect of finely fibrillated cellulose and have made diligent studies. As a result, the mechanical shearing force was applied to a slurry in which powder and pulp are mixed. By adding a composite of powder and fine fibrillated cellulose obtained by giving (hereinafter referred to as powder complex fine fibrillated cellulose in the present invention) to a pulp pulp for papermaking, as compared with the conventional method, To improve the yield of powder without disturbing the texture such as texture, to reduce the decrease in paper strength, and to prevent deterioration of drainage, which is the biggest problem when using fine fibrillated cellulose in the papermaking process The effect was found and the present invention was completed. That is, the gist of the present invention is that a composite of powder and fine fibrillated cellulose obtained by applying a strong mechanical shearing force to a slurry in which powder and pulp are mixed (powder-composited fine fibrillated cellulose). ) To the pulp pulp for papermaking,
It is a method for producing powder-containing paper, which is characterized by making paper.

The present inventors have found that the powder-composite fine fibrillated cellulose obtained by applying mechanical shearing force to a slurry in which powder and pulp are mixed exhibits the above-mentioned effects by microscopic observation. It is assumed that the reason is as follows. By imparting a strong mechanical shearing force to the mixture of powder and pulp slurry, the cellulose fibers constituting the pulp are micronized, and fine fibrillated cellulose is produced. During this generation process, the powder is wrapped in or adsorbed in the network of fine fibrillated cellulose, and the fine fibrillated cellulose is a tuft-like aggregate that holds the powder. Form cellulose. The powder itself may be miniaturized in this process, although it depends on the type of device to be miniaturized and the composition of the powder.

The powder-composited fine fibrillated cellulose is larger than the particle size of the powder, and as described above, the powder is in the form of tuft-like aggregates encased in the fine fibrillated cellulose. Therefore, when this is added to the pulp slurry, the binding force with the pulp fiber is large and the yield in the paper is high. Further, the powder-composited finely fibrillated cellulose does not cause aggregation of the pulp even when it is added to the pulp slurry, so that there is an advantage that the paper can be made without causing deterioration of the formation. The morphology in which the powder and the fine fibrillated cellulose are aggregated prevents the deterioration of drainage that occurs when the fine fibrillated cellulose is added alone,
It prevents the inhibition of pulp fiber-fiber bonding that occurs when powder is added. Further, it is known that the refined pulp fiber has an increased specific surface area, which leads to an improvement in paper strength. Even if the content of the powder is increased, the paper strength is not lowered and the strength is increased. .

As a mechanical treatment method for obtaining powder-composited fine fibrillated cellulose, any apparatus capable of producing fine fibrillated cellulose can be used.
For example, a high-pressure homogenizer, a medium agitating mill, a media agitating wet pulverizing device, a vibration mill, a ball mill, a planetary mill, an abrasive grain plate rubbing device, and the like can be used. It was found that the method for producing pulverized fine fibrillated cellulose is efficient and has a great effect.

The refinement of the pulp by the rubbing of the abrasive grain plate and the compounding with the powder are effective because the fine abrasive grains constituting the abrasive grain plate cause microscopic protrusions on the abrading surface of the abrasive grain plate. It is greatly related that the part is formed and is very uneven. In such protrusions of the abrasive grains pulp fiber and powder undergoes a strong mechanical shearing force, so that fineness and compounding progress, but since protrusions are present everywhere in the abrasive grain plate, It is considered that the cell wall of the pulp fiber is efficiently divided into individual fibrils and further rubbed together to effectively form a composite with the powder. Also, it was confirmed that the presence of the powder promotes the fibrillation of the pulp more efficiently, and that there is a secondary effect that the processing time can be significantly shortened compared to when the powder is not mixed. I understood.

An example of the abrasive plate rubbing apparatus described above is schematically shown in FIGS. 1 and 2. The illustrated apparatus is configured by arranging an upper fixed abrasive plate 1 and a lower rotating abrasive plate 2 by rubbing each other, and the inner surfaces of the two abrasive plates facing each other are tapered toward the center thereof. A space to be the grinding chamber 3 is formed by cutting out the flat surfaces 4a in the vicinity of the outer peripheral edges of the two abrasive grain plates to contact with each other to form the rubbing portion 4. A hopper 6 is provided above the central opening 5 of the fixed abrasive plate 1.
Is installed, and the lower part of the hopper 6 communicates with the grinding chamber 3. A central hole of the rotary abrasive grain plate 2 is closed by a sealing plate 7, and the rotary abrasive grain plate 2 is rotated by a drive motor 9 via a shaft 8 extending downward from the lower surface thereof. A support rod 10 extending upward from the sealing plate 7 of the rotary abrasive grain plate 2 arranges an umbrella-shaped flow straightening plate 11 substantially at the center of the grinding chamber 3. FIG. 3 is a view of the fixed abrasive plate 1 as seen from the inner surface side, and a feed groove 12 is formed in the taper surface forming the grinding chamber 3 from the central opening 5 in a substantially radial direction to serve as a friction portion. The feed groove 12 is not formed in the flat surface 4a near the periphery. The form and number of the feed grooves are not necessarily limited to those shown in the figure.

The miniaturization and composite processing by this apparatus is performed as follows. When the slurry in which the pulp and the powder are mixed is supplied to the hopper 6 (arrow A in FIG. 2), the mixed slurry flows down, is dispersed radially by the straightening vanes 11 and is uniformly supplied into the grinding chamber 3. . The pulp slurry in the grinding chamber 3 is caused by the centrifugal force of the rotary abrasive plate 2 and the grinding chamber 3
By the action of the feed groove 12 on the inner surface, it is sent to the rubbing portion 4 of the abrasive grain plates 1 and 2, where the rubbing action of the upper and lower abrasive grain plates makes the pulp fine and combines it with the powder. The slurry of the powder-composited fine fibrillated cellulose thus produced flows out from the outer peripheral edges of the abrasive grain plates 1 and 2 by a centrifugal force (arrow B in FIG. 2). The slurry of the powder-composited fine fibrillated cellulose that flows out is recycled to the hopper 6 and can be subjected to this treatment until the desired powder-composited fine fibrillated cellulose is obtained.

The abrasive grain plate of the abrasive grain plate rubbing apparatus is formed by solidifying abrasive grains, which are particles of the abrasive, with a binder, and the conventionally used material for the abrasive grains,
For example, natural products such as diamond, corundum, and emery, and artificial products such as synthetic diamond, cubic boron nitride, alumina, silicon carbide, and boron carbide can be used. When using porous ceramics as the material of the abrasive grains, the finely divided cellulose enters inside the pores of the ceramics,
Since bacteria may be generated, it is desirable to fill the pores of the ceramic with synthetic resin or the like in advance.

Particularly, as the abrasive grain plate of the abrasive grain plate rubbing apparatus used in the present invention, the grain size of the abrasive grain is JIS P 6001.
It is necessary to use the particles of No. 24 to No. 80 with the grain size specified in. The present inventors have found that the grain size is 5 to 24 for the pulp refining effect and the composite effect with the powder.
As a result of sequentially examining the particle sizes up to No. 0, when the particle size is coarser than No. 24, even if the grinding treatment is performed for a long time, desired miniaturization and compounding do not proceed, while the particle size is more than 80 It has been found that when the particle size is fine, clogging easily occurs at the rubbing part of the abrasive grain plate, and it becomes difficult to discharge the finely pulverized and composited slurry. Therefore, the grain size of the abrasive is 2
Must be numbered 4-80.

As a result of various studies by the present inventors, the fine fibrillated cellulose constituting the powder-composited fine fibrillated cellulose has a number average fiber length of 0.05 to 0.3.
It has been found that mm is preferred. If the length is longer than this length, the effect of wrapping the powder is reduced, and at the same time, the specific surface area is also reduced, so that the binder effect for reinforcing the interfiber bond is reduced and the paper strength increasing effect is reduced. On the other hand, if the length is shorter than 0.05 mm, the powder composite fine fibrillated cellulose tends to come out from the gap between the wires during dehydration on the wires during paper making, resulting in poor yield.

The number average fiber length of the present invention is a fiber length distribution measuring device (FS-20 manufactured by KAJAANI (Finland).
Of the data measured in 0), the total length of the fibers present in a given pulp suspension is integrated and then divided by the number. LBKP and NB, which are the raw materials for ordinary paper
KP is a number average fiber length of 0.5 mm and 1 m, respectively.
It has a length of about m, and the number average fiber length is 0.35m at the minimum even for fibrillated fibers generated by the beating process.
The length is about m. On the other hand, the number average fiber length of the powder-composited fine fibrillated cellulose produced in the present invention is 0.05 to 0.3 mm, which is extremely fine.

The ratio of the pulp to the powder in producing the powder-composited fine fibrillated cellulose is effective at any ratio, but the dry weight ratio is in the range of 1: 1 to 1:10. Was found to be remarkable. It has been confirmed that if the content is outside this range, either pulp fiber or powder is in an excessive state, the production efficiency is deteriorated, and the effect when added to the pulp for papermaking tends to be small. A ratio of 1: 5 is preferable in consideration of the drainage in an actual machine, the amount of powder added, the amount of fine fibrillated cellulose used, and the like.

The solid content concentration of the slurry in which the powder and the pulp are mixed at the time of producing the powder composite fine fibrillated cellulose is preferably 1 to 10%. When the solid content concentration is less than 1%, it takes a long treatment time and the distance between the powder and the fiber becomes large, so that the powder may not be held properly. Further, since the viscosity increases remarkably as the pulp is made finer, it becomes impossible to smoothly process it at a concentration exceeding 10%.

As the pulp used for producing the powder-composited fine fibrillated cellulose, any pulp can be used. For example, hardwood bleached kraft pulp (LBK
P), chemical pulp such as softwood bleached kraft pulp (NBKP), softwood bleached sulfite pulp (NBSP), groundwood pulp (GP), thermomechanical pulp (T
Wood pulp such as mechanical pulp such as MP), cotton pulp, non-wood pulp such as hemp, goose bark, and San camellia fiber pulp, and regenerated cellulose fiber are used. Fibers that are easier to fibrillate are more suitable for compounding powders,
In wood pulp, it is preferable to use NBKP containing a temporary conduit as a main component.

As the powder used in the production of the powder-composited fine fibrillated cellulose, any powder can be used. Specifically, clay, calcium carbonate, talc, titanium dioxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium aluminate,
Zeolites, sepiolite, zinc sulfide, gypsum, diatomaceous earth, precipitated barium sulfate, plastic pigments and the like can be used. Further, it is possible to use inorganic pigments such as molybdenum orange, iron oxide, and ultramarine used for coloring paper, and naphthalanol pigments, phosphomolybdic acid pigments, phthalocyanine pigments, quinacridone pigments, and organic pigments such as iron cyanide. .

The method for producing the powder-containing paper of the present invention is as follows. The powder-composite fine fibrillated cellulose is converted into a powder ratio in a papermaking pulp slurry having a normal concentration of about 4% by weight, and the paper-making pulp is used. Add 1 to 20% by weight. At this time, a colorant such as a dye or a pigment, a sizing agent, a dry paper strength enhancer, a wet paper strength enhancer, a yield improving agent and the like can be added as required. The powder composite microfibrillated cellulose is preferably added at a position closer to the head box in consideration of the yield.

As the yield improver, an inorganic compound such as a sulfuric acid band (aluminum sulfate) or polyethyleneimine,
It is possible to use organic polymer compounds such as polyacrylamide and polyamide polyamine epichlorohydrin,
The dual system method as described above, such as the combined use of cationic polyacrylamide and anionic polyacrylamide, is also possible. The powder-containing paper of the present invention is prepared by a conventional method using a cylinder paper machine, a fourdrinier paper machine, an inclined paper machine, a twin wire paper machine, or the like.

The present invention will be specifically described below with reference to examples. Both parts by weight and% by weight are dry parts by weight and dry weight%
Indicates. Example 1 NBKP and clay (white clay first grade, manufactured by Shiraishi Industry Co., Ltd.) were mixed at a dry weight ratio of 1: 5 to prepare a slurry having a solid content concentration of 6% by weight. This slurry was treated with Super Grindel (manufactured by Masuyuki Sangyo Co., Ltd.) for 15 minutes to obtain a powder-composited fine fibrillated cellulose. When the number average fiber length of fine fibrillated cellulose was measured, it was 0.28 m.
It was m. Then, 12 parts by weight of the powder-composite fine fibrillated cellulose prepared above was added to 88 parts by weight of the paper-making pulp made of NBKP prepared to have a freeness of 500 ml CSF. As a result, all papermaking raw materials (papermaking pulp +
The contents of fine fibrillated cellulose and clay with respect to fine fibrillated cellulose) are 2% by weight and 10% by weight, respectively. The powder composite fine fibrillated cellulose was stirred for 10 minutes in order to be uniformly dispersed, and then aluminum sulfate was used as a fixing agent and added so that the pH of the slurry became 4.5. Then, using a Fourdrinier paper machine, a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method.

Example 2 NBKP (same as above) and clay (same as above) in a dry weight ratio of 1: 1.
0 to prepare a slurry having a solid content concentration of 6% by weight. 1 this slurry with Super Grindell (same as above)
The mixture was treated for 5 minutes to obtain a powder-composited fine fibrillated cellulose. The number average fiber length of the fine fibrillated cellulose was measured and found to be 0.18 mm. Next, 55 parts by weight of the powder composite fine fibrillated cellulose prepared above was added to 45 parts by weight of the papermaking pulp made of NBKP prepared to have a freeness of 500 ml CSF. As a result, the contents of fine fibrillated cellulose and clay with respect to the total amount of the papermaking raw materials are 5% by weight and 50% by weight, respectively. The powder composite fine fibrillated cellulose was stirred for 10 minutes in order to be uniformly dispersed, and then aluminum sulfate was used as a fixing agent and added so that the pH of the slurry became 4.5. Then, using a Fourdrinier paper machine, a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method.

Comparative Example 1 10 parts by weight of clay (same as above) was added to 90 parts by weight of NBKP (same as above) prepared to have a freeness of 500 ml CSF. Clay content is 10% by weight with respect to all papermaking raw materials
become. After stirring for 10 minutes to uniformly disperse the clay, aluminum sulfate was used as a fixing agent and added so that the pH of the slurry became 4.5. Then polyethyleneimine (trade name "Polymin SN", BASF Corporation)
(Manufacturing) was added in an amount of 1 part by weight, and a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method using a Fourdrinier paper machine.

Comparative Example 2 Freeness 500 ml CSF NBKP (same as above) 88 parts by weight, Super Grindell (same as above)
2 parts by weight of fine fibrillated cellulose prepared by the method to have a number average fiber length of 0.28 mm was added and uniformly dispersed. 10 parts by weight of clay (same as above) was added to this slurry. As a result, the content of fine fibrillated cellulose and clay with respect to the total amount of papermaking raw materials was 2% by weight,
It becomes 10% by weight. After stirring for 10 minutes to uniformly disperse the clay, aluminum sulfate was used as a fixing agent and added so that the pH of the slurry became 4.5. Using a Fourdrinier paper machine, a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method.

Comparative Example 3 50 parts by weight of clay (same as above) was added to 90 parts by weight of NBKP (same as above) prepared to have a freeness of 500 ml CSF. As a result, the content of clay relative to all papermaking raw materials is
50% by weight. After stirring for 10 minutes to uniformly disperse the clay, aluminum sulfate was used as a fixing agent and added so that the pH of the slurry was 4.5, and then 1 part by weight of polyethyleneimine (same as above) was added to Using a net paper machine, a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method.

Comparative Example 4 Freeness: NBKP prepared in 500 ml CSF (same as above) to 45 parts by weight, SuperGrindel (same as above)
5 parts by weight of fine fibrillated cellulose adjusted to have a number average fiber length of 0.18 mm was added and uniformly dispersed. To this slurry, 45 parts by weight of clay (same as above) was added. As a result, the content of fine fibrillated cellulose and clay relative to the total amount of papermaking raw materials was 5% by weight,
50% by weight. After stirring for 10 minutes to evenly disperse the clay, use aluminum sulfate as a fixing agent
It was added so that it might be 4.5. Using a Fourdrinier paper machine, a powder-containing paper having a basis weight of 80 g / m ^{2 was} produced by a conventional method.

The physical properties of the powder-containing papers obtained in the examples and comparative examples were evaluated. Each physical property measuring method and evaluation were as follows. 1) Drainage: The degree of drainage was visually observed on a paper making net. O indicates that the drainage is good, Δ indicates that there is no problem in practical use, and X indicates that the drainage is poor and there is a problem in practice. 2) Ash content: Measured by the method specified in JIS P8128. 3) Powder yield: determined from (ash content / theoretical ash value) × 100. 4) Breaking length: measured by the method specified in JIS P8113. For papers of the same basis weight, the larger the breaking length, the greater the tensile strength. 5) Formation: The sheet formation of the paper observed with transmitted light is indicated by ◯, the state where a little floc is formed is indicated by Δ, and the large floc is indicated by x. The evaluation results are shown in Table 1.

[0031]

[Table 1]

Examples 1 and 2 are examples in which powder-composited fine fibrillated cellulose was added to the slurry, and Comparative Examples 1 and 3
Is an example using a dual polymer system, Comparative Example 2
And 4 are examples in which the fine fibrillated cellulose and the powder were separately added to the slurry and used. The following can be seen from Table 1. 1) Comparison between Example 1 and Comparative Example 1 using the powder-combined fine fibrillated cellulose, even though the amount of powder added to the fiber (pulp + fine fibrillated cellulose) was the same. It can be seen that Example 1 is superior to the dual polymer system of Comparative Example 1 in powder yield, tensile strength and formation. 2) Comparing Example 1 and Comparative Example 2, although the ratios of pulp, fine fibrillated cellulose and clay were the same, Example 1 using powder-composited fine fibrillated cellulose was more draining. It can be seen that the powder yield, the tensile strength and the formation are all superior to those of Comparative Example 2. 3) Comparing Example 2 in which the amount of powder added is large with Comparative Example 3, the dual polymer system (Comparative Example 3) has good drainage but weak tensile strength, resulting in flock formation. It turns out that it will end up. On the other hand, in Example 2, the drainage is also good, and it is understood that the tensile strength, the powder retention, and the formation are all better than those of Comparative Example 3. 4) Comparing Example 2 and Comparative Example 4 in which the amount of powder added was large, powder-composited fine fibrillated cellulose was obtained even though the ratios of pulp, fine fibrillated cellulose and clay were the same. It can be seen that the used Example 2 has better drainage, powder retention, tensile strength and formation than Example 4 in which the fine fibrillated cellulose and the powder were added separately.

In the above Examples and Comparative Examples, an example of clay was given as the powder, but the present inventors have confirmed that similar results can be obtained with other powders as described above.

[0034]

The method for producing powder-containing paper according to the present invention has the following remarkable effects. 1) Although it is possible to realize a powder yield surpassing the dual polymer system, which has been said to have the best powder yield, it is possible to make paper without breaking the texture of the paper. 2) The deterioration of drainage, which was a problem of the conventional method of separately adding powder and fine fibrillated cellulose, can be improved in the present invention, and papermaking becomes easy. 3) In papermaking of powder-containing paper, it has been conventionally said that the strength of the paper decreases with an increase in the fixing amount of the powder. However, in the present invention, even if the fixing amount of the powder increases, the paper strength is increased. You can prevent the decline. 4) Utilizing the above characteristics, the present invention provides clay, talc,
Printing paper such as high-quality paper containing powders such as kaolin, calcium carbonate, titanium dioxide, etc. and powder containing aluminum hydroxide, magnesium hydroxide, calcium aluminate, calcium hydroxide, calcium aluminate, etc. It can be suitably used for the production of combustible paper, non-combustible paper, silica gel, aluminosilicate, zeolite, activated carbon, gas-adsorbed paper internally added with powder such as activated alumina, and the like.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an abrasive grain plate rubbing apparatus used in the present invention.

2 is a cross-sectional view of the device of FIG.

FIG. 3 is a plan view showing an example of an abrasive grain plate used in the apparatus of FIG.

[Explanation of symbols]

1: Fixed abrasive plate 2: Rotating abrasive plate 3: Grinding room 4: Rubbed part 6: Hopper 9: Drive motor 12: Feed groove

Claims (4)

(57) [Claims] 1. A pulp for papermaking comprising a composite of powder and fine fibrillated cellulose (powder-combined fine fibrillated cellulose) obtained by applying a strong mechanical shearing force to a slurry obtained by mixing powder and pulp. A method for producing a powder-containing paper, which comprises adding paper to a slurry and then making a paper. 2. The method for producing powder-containing paper according to claim 1, wherein the number average fiber length of the fine fibrillated cellulose is 0.05 to 0.3 mm. 3. The method according to claim 1, wherein the ratio of the pulp to the powder in producing the powder-composited fine fibrillated cellulose is 1: 1 to 1:10 in dry weight ratio. A method for producing the powder-containing paper described. 4. The solid content concentration of the slurry for producing the powder composite fine fibrillated cellulose is 1 to 10% by weight.
The method for producing powder-containing paper according to claim 1, 2 or 3, wherein