JPH02133695A - Paper-making process - Google Patents

Abstract

PURPOSE:To remarkably increase the yield of paper-making process, improve the freeness of paper and strength of dried sheet and improve the quality of produced paper by adding a cationic crosslinked starch having a specific substitution degree of cationic group and a specific crosslinking degree to a paper-making slurry. CONSTITUTION:(A) A paper-making slurry containing (i) cellulose fiber and optionally (ii) an inorganic filler is added with (B) 0.05-5wt.% (based on the component i or the sum of i and ii) of a cationic crosslinked starch having a crosslinking degree of 0.00001-0.1 and a cationic group substitution degree of 0.01-0.1. The obtained slurry is subjected to paper-making process, dehydrated and dried to obtain the objective paper. The slurry is preferably further added with (C) 0.01-5.0wt.% of an anionic aqueous silica sol (in terms of SiO2), bentonite, a water-soluble anionic polymer or their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention aims to improve a method for producing paper mainly composed of cellulose fibers or cellulose fibers and inorganic fillers, and in particular to significantly improve the yield of cellulose fibers and inorganic fillers in the papermaking process. The present invention relates to a paper manufacturing method capable of improving water freeness and paper strength of a dry smoke sheet. More specifically, the present invention involves adding cationic crosslinked starch having a specific amount of cationic group substitution degree and crosslinking degree to a papermaking stock solution containing cellulose fibers or cellulose fibers and an inorganic filler before papermaking. Particularly related to improvements in paper manufacturing methods.

[Conventional technology]

Paper mainly composed of cellulose fibers or cellulose fibers and inorganic fillers is generally made by dispersing cellulose bulbs in water, disintegrating them, adjusting the concentration, and adding fillers and other additives as desired. It is produced by feeding it into a machine, dehydrating it, and drying it. However, to compensate for the lack of high-quality bulbs and to reduce manufacturing costs, the amount of low-quality bulbs used as cellulose fibers has increased, and the amount of inorganic fillers added has increased. is also increasing. Furthermore, in order to improve productivity, there is a demand for improved yield during paper making, improved freeness, and improved paper quality.

In order to improve the yield during papermaking, aluminum sulfate has been added as a flocculant to the papermaking stock solution, but this method requires adjusting the papermaking stock solution to be acidic before making paper. This causes a decrease in the durability of the paper product, makes it difficult to reuse the white water, and also brings about the restriction that calcium carbonate cannot be used as an added filler.

US Pat. No. 2,876,217 discloses a papermaking method in which the yield during papermaking is improved by using cationic starch obtained by introducing a cationic group such as an ammonium group instead of using aluminum sulfate.

As a further improved method, JP-A-57-51900 discloses a method in which cationic starch and anionic aqueous silica sol are added to a papermaking stock solution before papermaking.

Japanese Patent Publication No. 45-26564 discloses a method of using so-called amphoteric starch, which has a cationic group and an anionic group such as a phosphoric acid group, but is not crosslinked, as a retention improver during papermaking.

Japanese Patent Publication No. 1159 discloses that cross-linked starch obtained by reacting starch with an aqueous solution of phosphoric anhydride in the initial hydration stage can be used as a food additive, thickening agent, etc. is disclosed.

[Problem to be solved by the invention]

The above-mentioned US Pat. No. 2,876,217 does not disclose cationic starch having a crosslinked structure. By using non-crosslinked cationic starch, neither the yield improvement effect during papermaking nor the strength improvement of the paper product can be sufficiently improved. According to the method disclosed in Japanese Patent Application Laid-open No. 57-51900,
By adding cationic starch and anionic silica sol to the papermaking stock solution, it is possible to improve freeness, product paper quality, etc., compared to when cationic starch is added alone, but depending on the papermaking conditions, a sufficient improvement in yield can still be achieved. This publication also does not disclose the use of cationic starch having a crosslinked structure.

Japanese Patent Publication No. 45-11159 does not disclose further cationization of the cross-linked starch or its addition to the papermaking stock solution. Special Publication No. 45-26564 is
Anionic phosphate base to cationic group.

It has been proposed to improve the yield by adding so-called amphoteric starch, which is contained in a molar ratio of 0.01 to 4.5 but does not cause cross-linking of starch molecules, to the stock solution for papermaking. However, in paper making in the neutral pH range, a sufficiently high yield cannot be achieved.

The present invention relates to a paper manufacturing method in which cellulose fibers or a normal paper stock solution containing cellulose fibers and inorganic fillers are made into paper, dehydrated, and dried. It is an object of the present invention to provide a paper manufacturing method that can improve paper production and homogeneity.

[Means for Solving the Problems] The paper manufacturing method of the present invention is a paper manufacturing method in which a paper manufacturing solution containing cellulose fibers or cellulose fibers and an inorganic filler is made into paper, dehydrated, and then allowed to dry. O, oooo i~0 in an amount of 0.05 to 5.0% by weight based on the total amount of cellulose fiber or the inorganic filler in the stock solution
．． It is characterized by adding a cationic crosslinked starch having a degree of crosslinking of 1 and a degree of cationic group substitution of 0.01 to 0.1. A more preferred papermaking method according to the present invention includes adding a specific amount of the cationic crosslinked starch to the papermaking stock solution, and further adding anionic aqueous silica sol (as S102), bentonite, a water-soluble anionic polymer, or a water-soluble anionic polymer thereof. It is characterized in that the mixture is added in an amount of 0.01 to 5.0% by weight based on the total amount of cellulose fiber or the inorganic filler in the above-mentioned stock solution.

The cellulose fibers used in the paper manufacturing method of the present invention are obtained by beating cellulose bulbs used in ordinary paper manufacturing using a beater or the like. The cellulose valve may be a chemical valve, a mechanical valve, a thermo-mechanical valve, a ground wood valve, or the like. Waste paper is also used to replace some of these new valves.

The inorganic filler used in the present invention may be a common mineral filler for papermaking, such as kaolin (China clay), white clay,
Examples include titanium dioxide, anionic heavy calcium carbonate, light calcium carbonate, calcined ash, wollastonite, synthetic silica, talc, aluminum hydroxide, mineral fiber, glass fiber, perlite, and the like.

The papermaking stock solution used in the present invention is a liquid obtained by dispersing the above-mentioned ordinary papermaking cellulose fiber or the same and the above-mentioned inorganic filler in water. The inorganic filler is preferably added to the stock solution in an amount of 150% by weight or less based on the cellulose fibers in the paper of the product, but the content may be higher than this.

Also in the present invention, the concentration of cellulose fibers in the papermaking stock solution may be the same as the concentration of cellulose fibers in the papermaking stock solution in a normal papermaking method. As long as the purpose of the present invention is achieved, sizing agents, fixing agents, antifoaming agents, slime control agents, dyes, and other additives may be added to the papermaking stock solution. In addition, this papermaking stock solution has a pH of 4 to 1
O applies.

The anionic silica sol used in the present invention has a particle size of 2
It is a liquid in which colloidal silica of ~10 millimicrons is stably dispersed in water, and can be produced by a known method. Such silica sol can be produced either acidic or alkaline, and is usually stable at 8.
Obtained as a product of 10□30% by weight or less. In the present invention, an alkaline one with high storage stability is preferable, and S
ID2'Ir1 degree is adjusted by diluting with water as appropriate for convenience of use.

Preferred water-soluble anionic polymers used in the present invention include known anionic polyacrylamide,
Examples include sodium polyacrylate and sulfonic acid group-containing melamine formaldehyde condensate salt, but in addition, copolymers of esters of acrylic acid or methacrylic acid and acrylic acid can also be used. It is usually preferable to use these poly(7-) in the form of an aqueous solution, and the bentonite used in the present invention may also be a normal bentonite.

The cationic cross-linked starch used in the present invention is produced by reacting a cross-linking agent and a cationizing agent with ordinary starch such as potato starch, corn starch, wheat starch, tapioca starch, oxidized starch thereof, and hydrolyzed starch. By causing the starch molecules to have a concentration of 0.00001 to 0.1, preferably 0.
A crosslinked structure with a degree of crosslinking of 0.0001 to 0.08 and a degree of cationic group substitution of 0.01 to 0.1, preferably 0.015 to 0.0.
This is a starch derivative into which 7 cationic groups have been introduced. A typical example of the crosslinking agent used is an aqueous solution of phosphoric anhydride in the initial stage of the hydration reaction, but dichlorohydrin, epichlorohydrin, formalin, etc. can also be used. The cationizing agent used may also be a conventional one, for example, 3-chloro-2-hydroxypropyltrimethylammonium sulfamate, 3-chloro-2-hydroxypropyltriethylammonium sulfamate, 3-chloro-2-hydroxypropyl. Trimethylammonium chloride, 3-chloro-2-hydroxypropyltriethylammonium chloride, 2.3-epoxypropyltrimethylammonium sulfamate, 2.3-epoxypropyltriethylammonium sulfamate, 2.3-epoxypropyltrimethylammonium chloride , 2,3-epoxypropyltriethylammonium chloride, and the like.

Above rack t! The degree of crosslinking in starch is determined by multiplying the ratio of the number of OH groups in the starch molecule reacted with the crosslinking agent to the number of glucose units in the starch molecule by 1/2. Further, the degree of cationic group substitution is defined by the ratio of the number of OH groups in the starch molecule reacted with the cationizing agent to the number of glucose units in the starch molecule.

The reaction for introducing a crosslinked structure into the starch molecule and the reaction for introducing a cationic group may be performed either first or at the same time. The reaction for introducing these crosslinked structures and the reaction for introducing cationic groups are as follows:
In an alkaline solvent with a pH of 8 or higher, usually 100
t' or less for about 0.1 to 24 hours, preferably,
This can be easily carried out by reacting starch with a crosslinking agent or a cationizing agent at 25 to 80°C for 0.5 to 20 hours. Examples of solvents that can be used include water, inert hydrophilic organic solvents such as methanol, ethanol, isopropanol, butanol, other ethers, ketones, or mixed solvents of water and these inert hydrophilic organic solvents. Can be mentioned. A particularly preferred solvent is water or a mixed solvent of 1 part by weight of water and 0.01 to 100 parts by weight of ethanol or isopropanol. Normal 1 in starch used in reaction
0 to 20% water by weight can also be utilized as part of the solvent. Maintaining the alkalinity during the reaction can be easily carried out by adding an alkaline substance such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc. to the reaction mixture. The amount of solvent used is suitably about 0.1 to 20 times the weight of the starch. Further, the degree of crosslinking and the degree of substitution can be easily adjusted by appropriately selecting the ratio of the starch to the crosslinking agent and cationizing agent used in the reaction, reaction temperature, reaction time, etc. After the above reaction is completed, if necessary, an acid is added to the reaction mixture to make it weakly acidic to neutral, and if desired, the reaction mixture can be purified by washing with a washing medium such as water. Further, a powdery cationic crosslinked starch can be obtained by drying the reaction mixture as it is, or after the neutralization, washing, or neutralization and washing.

The cationic crosslinked starch obtained as described above is subjected to a baking treatment before being added to the papermaking stock solution. This shoeing is performed at a concentration of the cationic crosslinked starch in water of about 0.1 to 1.0% by weight, preferably 0.43 to 0.0% by weight.
At 7% by weight, the gelatinization temperature is higher than the decomposition temperature.
It will take about 10 to 20 minutes. This cooking process yields a viscous, transparent, paste-like liquid of cationic crosslinked starch.

The cationic crosslinked starch added to the stock solution for papermaking according to the present invention is added to the stock solution for papermaking as a paste-like liquid that has been subjected to wrapping as described above. If desired, other cationic substances such as cationic polyacrylamide, alumina sol, basic aluminum chloride, cationic silica sol, etc. may be added to the papermaking stock solution in combination with the cationic crosslinked starch described in F. can.

The paper of the product according to the present invention is produced by adding the above-mentioned cationic cross-linked starch to the papermaking stock solution in a proportion of 0.05 to 5.0, preferably 0.
．． It is obtained by adding 1 to 3.0% by weight and thoroughly mixing, followed by paper making, dewatering, and drying according to a conventional method. More preferably, in the paper produced by the papermaking method of the present invention, the papermaking stock solution contains 0.05 to 5.0, preferably 0.1 to 5.0, based on the total amount of cellulose fiber or the inorganic filler in the stock solution.
3.0% by weight of the above cationic cross-linked starch and 0.01% by weight of the above cationic cross-linked starch
Anionic silica sols, bentonites, water-soluble anionic polymers or mixtures thereof giving 5i02 min in an amount of ~5.0% by weight are added and, after thorough mixing, obtained via the above-mentioned conventional methods.

[For production]

The improvement of the papermaking process according to the invention is due to the essentially cationic crosslinked starch, in particular its low degree of crosslinking of 0.00001 to 0.1.

The above cited Japanese Patent Publication No. 45-26564 also mentions G?
i! Powdered esters inhibit gelation in water and are prohibited products, making them unsuitable for papermaking processes. It was thought that it would have no effect due to its low swelling property, but when the crosslinked structure was
It is surprising that a cationic starch with extremely high performance can be obtained by introducing it into starch.

As a cationic crosslinked starch, its degree of crosslinking is 0.000
01 or less is almost the same as conventionally used cationic starch without introducing a crosslinked structure, and cationic starch with a degree of crosslinking exceeding 0.1 does not show the high yield improvement effect of the present invention. .

Even if the degree of crosslinking is 0.00001 to 0.1, the degree of cationic group substitution is 0.00001 to 0.1. When the degree of substitution is lower than O1, the yield improvement effect is poor, and even if the degree of cationic group substitution exceeds 0.1, the yield improvement effect is not relatively high, which is undesirable because it increases the production cost of cationic starch. The effect of the cationic cross-linked starch according to the present invention to bring about a high yield is that the cellulose fibers produced by the cationic cross-linked starch in the papermaking stock solution or the aggregates containing this, an inorganic filler, and the cationic cross-linked starch are strong. This is thought to be due to certain reasons. The particularly preferable degree of crosslinking of this cationic crosslinked starch of 0.0001 to 0.08 and degree of cationic group substitution of 0.015 to 0.07 are considered to contribute to the formation of the above-mentioned preferable aggregates.

However, the addition of this cationic cross-linked starch is 0.05% based on the total amount of cellulose fiber or this and inorganic filler.
If the amount is less than 5.0% by weight, the effect of improving the yield during paper making is poor, and even if it is added to 5.0% by weight or more, no improvement in yield will be observed, and the manufacturing cost of the product paper will increase. Therefore, particularly preferred additions ff10.1 to 3.
The above-mentioned preferred degree of crosslinking is o, oooi to 0.08 to 0% debt
It is believed that by adding a cationic crosslinked starch having a degree of cationic group substitution of 0.015 to 0.07 to the papermaking stock solution, the above-mentioned preferred aggregates are advantageously formed in the papermaking stock solution.

In a more preferred papermaking method according to the present invention, anionic aqueous silica sol, water-soluble anionic polymer, bentonite, etc. used together with the cationic crosslinked starch improve drainage during papermaking. These anionic substances act as negatively charged colloidal particles in the papermaking stock solution, forming composite aggregates consisting of the three components of cellulose fibers, cationic crosslinked starch, and the above anionic substances, or cellulose fibers, inorganic filler, and Cationic crosslinked starch - constitutes one component of the four-component composite aggregate consisting of the above-mentioned anionic substance. In the production of these composite aggregates, the cationic cross-linked starch and the ionic substance are thought to work together to form strong, homogeneous aggregates.

In order to fully exhibit the effects of this anionic substance, the solid content of the anionic substance needs to be at least 0.01% by weight based on the total amount of cellulose fiber or the inorganic filler, but 5% by weight is required. Even if it is increased above that level, it is not effective in improving the yield. Silica sol, which is particularly preferred as this anionic substance, significantly improves freeness and yield during paper making. If the size of the colloidal silica particles is smaller than 2 millimicrons, it will be difficult to produce paper of a certain quality due to the poor stability of the sol itself. It is not very advantageous for improving yield. Particularly high freeness and improvement in yield are achieved by reducing the amount of the anionic substance per 1 part by weight of cationic cross-linked starch.
．． 0.002 to 20 parts by weight.

〔Example〕

Seven types of cationic cross-linked starches (codes CLS-1 to CLS-7'') used as examples of the present invention and two types of cationic cross-linked starches (codes CLS-7'') used as comparative examples.
-8 to CLS-9), a cationic starch without a crosslinked structure (code C3-1>) and a crosslinked starch without a cationic group (code LS-1) are produced by the following method, and then the starches obtained are The degree of cationic group substitution and degree of crosslinking of the derivatives were measured, and the results shown in Table 1 were obtained.

In addition, the degree of cationic group substitution is calculated from the measured value of the total nitrogen content contained in the starch derivative using a total nitrogen analyzer,
In addition, the degree of crosslinking was determined by wet ashing the starch derivative with a sulfuric acid-nitric acid mixture, and then removing the phosphate groups with molybdenum yellow.
It was determined by a colorimetric method using the r++n wavelength, and the total amount of phosphorus excluding the phosphorus originally contained in the raw starch was determined by calculating the phosphorus content of the cross-linked bonds of the phosphoric acid diester.

(Production of [i, S-1) 50% by weight aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium sulfamate 1, prepared by dissolving phosphoric anhydride in water under water cooling.
A 0% by weight aqueous phosphoric acid anhydride solution and tapioca starch were prepared.

Next, 20 g of tapioca starch was put into an automatic mortar and kneaded with a pestle, and 1.16 g of the above phosphoric anhydride aqueous solution was added at room temperature.
was dripped. After 30 minutes of kneading, 1.98 g of the above aqueous solution of sulfamate was added dropwise. 30 more at room temperature
After kneading for 30 minutes, 0.86 g of a 44% by weight aqueous solution of IJum was added dropwise, followed by kneading for 30 minutes. Next, the obtained powdered reaction mixture was transferred to a glass container and
Cationic cross-linked starch (CLS-1) 20.8 by aging at 0-75°C for 4 hours, washing with 50 g of an equal weight mixture of water and methanol, filtering and dry-smoking.
I got g.

(Production of CLS-2) Instead of 1.98 g of the above sulfamate aqueous solution, 1.1
20.1 g of cationic crosslinked starch (CLS-2) was obtained in the same manner as in Production Example -F except that 6 g was used.

(Production of CLS-3) Cationic cross-linked starch (CLS-3) was produced in the same manner as above except that the amount of the aqueous sulfamate solution used was changed to 3.56 g
-3) 21.8 g was obtained.

(Production of CL S-4) The amount of the aqueous solution of phosphoric anhydride used was 0.58 g, the amount of the aqueous solution of sulfamate was 2.75 g, and the amount of the aqueous solution of IJium was 0.75 g. Other than that, 21.0 g of cationic crosslinked starch (C1,5-4) was obtained in the same manner as in the production example of CLS-1.

(Manufacture of CLS-5) An aqueous solution of phosphoric anhydride having a concentration of 10.0% by weight was newly prepared. The amount used of this aqueous solution of phosphoric anhydride was 2.30 g,
The amount of the aqueous solution of sulfamate used was 2.74 g, and the amount of the aqueous solution used was 1.72 g.
22.4 g of cationic crosslinked starch (CLS-5) was obtained in the same manner as in the production example of CLS-1 except for the following.

(Manufacture of CLS-6) An aqueous solution of phosphoric anhydride having a concentration of 19.4 g weight % was newly prepared. The amount of this aqueous solution of phosphoric anhydride is 2.28g.
, the amount of the aqueous solution of sulfamate used was 2.74 g and the amount of the aqueous solution of IJ was 2.91 g.
24.3 g of cationic crosslinked starch (CLS-6) was obtained in the same manner as in the production example of CLS-1, except that the amount of starch was 24.3 g.

(Manufacture of CLS-7) A 50% by weight aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was newly prepared. The amount of this aqueous solution of taloride used was 2.70 g, and the amount of the 1.0% by weight phosphoric anhydride aqueous solution used was 0.70 g.
20.9 g of cationic crosslinked starch (CLS-7) was obtained in the same manner as in the production example of LS-1, except that the amount of the IJium aqueous solution used was 75 g.

(Production of CLS-8) In the production example of CLS-6, the amount of phosphoric anhydride aqueous solution used was 5.70 g, the amount of sulfamate aqueous solution used was 2.75 g, and hydroxide) Change the usage amount to 7 JOg and add cationic cross-linked starch (
CLS-8) 24.9 g was obtained.

(CLS-9 manufactured by!J) [: In the production example of LS-1, 19.5 g of cationic crosslinked starch (CLS-9) was obtained by changing the amount of the sulfamate aqueous solution used to 0.32 g.

Production of ccs-i) Cationic starch (C3-1) was produced in the same manner as in the production example of CLS-1, except that the aqueous solution of phosphoric anhydride was not added.
5g was obtained.

(Manufacture of LS-1) C1, S- except that an aqueous solution of sulfamate was not added.
20.3 g of crosslinked starch (1,5-1) having no cationic group was obtained in the same manner as in Production Example 1.

Table 1 Code Degree of crosslinking Degree of cationic group substitution Example 1 and Comparative Example 1 After adjusting Valpusura 1J=(a) by the following method,
A papermaking stock solution (b-1) is prepared by adding additives, and the cutting solution (C) of the starch derivative produced above is added to this stock solution (b-1), and then the yield of fine components is determined by the following method (6). We carried out measurements.

(a) Pulp Slurry 90 g of softwood bleached kraft dry pulp and 270 g of hardwood bleached kraft dry pulp were added to 2.5 kg of water, and after being left for day and night, the mixture was milled using a laboratory beating machine until the standard freeness was 350 + tl. A valve slurry was prepared by beating the valve slurry.

(b-1) Papermaking stock solution To the valve slurry of (A) above, aluminum sulfate, gin sizing agent, kaolin clay, water, and sulfuric acid were added as a fixing agent, resulting in a pulp concentration of 0.35% by weight, kaolin (China clay). 0.15% by weight, aluminum sulfate (18
As an eternal thing. A papermaking stock solution (b-1>) with a pft of 4.5 and a rosin size of 110.0015% by weight and a kaolin/pulp ratio of 43% by weight was prepared.

(C) Cooking liquid Add 2°Og each of the above starch derivatives CLS-1 to CLS-9, cs-i and LS-1 to 400g of water,
After heating at 100° C. for 20 minutes while stirring, the mixture was cooled and water was added to obtain a cooking liquid having a concentration of 0.5% by weight.

(d) Proposal of yield measurement method Britt (Britt, K., W.; Ta
ppi, 56 (10) 46-50.1973).
r) Measure according to the following procedures (1) to (7) according to the test method.

(1) 500mI! Di+- medium paper making stock solution! , Jf[L
, 800 rpm. The exact dry solids (bulb+filler) concentration in this slurry is C weight %.

(2) Add starch ether derivative cooking liquid to this and start timing at j-.

(3) When adding an anionic component, add anionic silica sol, anionic polymer, or bentonite after 30 seconds. Stir for 30 seconds even when not adding anything.

(4) Start draining after another 15 seconds and collect white water for 30 seconds. The amount of white water during this time is assumed to be X ml.

(A 200-mesh wire mesh was used, and the hole diameter of the glass tube was adjusted so that the flow rate for 30 seconds was approximately 100 ml.) '
+g) is measured, filtered through quantitative filter paper (5C manufactured by Toyo Roshi), dried at 105°C, and measured for weight (filter paper - fine component). Let this weight be Wzg.

(6) The weight percent of the total fine components (ia fine pulp content) in the original papermaking stock solution is determined in advance by another method.

This value is defined as F%.

(7) The yield of fine components is calculated using the following formula.

Yield of fine components (wt%) In this Example 1 and Comparative Example 1, the above stock solution (b, -1)
5 g of the above cooking liquid was added to the mixture while stirring. No anionic components were added. When the yield of fine components was measured according to Section 2 (d), the results shown in Table 2 were obtained. Incidentally, the weight % F value of all the fine components in the stock solution was 36.

According to the results in Table 2 above, the yield of Example 1 is significantly higher than that of Comparative Example 10. C.L.
S-8 has a degree of crosslinking of 0.11, which is too large, and CLS
-9 has a cationic group substitution degree of 0.004, which is too small; cs-i is a cationic starch without a crosslinked structure; and 1. , S-1 is a starch derivative having a crosslinked structure but no cationic group, and is found to be unsuitable for achieving a high yield.

Example 2 and Comparative Example 2 Aluminum sulfate, rosin sizing agent, kaolin (China clay), water, and sulfuric acid were added as a fixing agent to the valve slurry of Example 1 (a) to give a valve concentration of 0.35% by weight.
, kaolin 0.15 weight 96, aluminum sulfate (18
As a hydrate. ) 0.0035% by weight, rosin sizing agent 0.0015% by weight, kaolin/pulp ratio 43% by weight
A papermaking stock solution (b-2) with p 84.5 was prepared. The total fine components of the stock solution was 36% by weight.

Next, 500 g of the above papermaking stock solution (b-1) was added with the starch ether derivative cooking liquid 5. (C) of Example 1 while stirring. Og was added, and then an anionic silica sol diluted solution (silica sol having physical properties of 15.0 wt% silica, pf 19.8, and particle size 5.0 mμ) was diluted with silica sol with a silica concentration of 0.
．． It was used after being diluted to 5% by weight. ) After adding 1.5g,
The yield of fine components and paper strength were measured by the following method.

The starch ether derivative/(bulb+filler) ratio is 1.0% by weight, and the anionic silica/(bulb+filler) ratio is 0.3% by weight.

(Method of measuring paper strength) Tsubo i! using TAPPI standard hand paper machine! 80g/
A hand-made paper sheet for physical testing of m2 was prepared. The resulting paper sheets were dried and cured in a forced hot air drying oven at 120±1° C. for 3 minutes. The processed paper obtained in this way is
After pretreatment according to the method specified in S-P8111, JIS
- Measure the breaking length by the method specified in P8113.

The longer the tearing length, the higher the strength of the paper.

Table 3 shows the measurement results of the yield and fracture length of fine components.

The results in Table 3 again show that the inventive examples did not provide significantly better yield and paper strength than the comparative examples.

〔Effect of the invention〕

According to the papermaking method of the present invention, in which paper is made after adding cationic starch into which a crosslinked structure has been introduced to a slight degree of crosslinking to a stock solution for papermaking, the papermaking yield can be significantly increased. This cationic cross-linked starch is highly effective even when used in combination with conventional anionic components such as silica sol.
Improves product paper quality.

Improving the papermaking yield in the paper manufacturing industry, especially improving the retention of fine components in the paper stock solution, reduces the cost of white water treatment, and improving freeness increases the filtration rate to increase the paper production rate, and improves the dewatering and drying process. However, it contributes to reducing the amount of heat required or increasing speed, and the effect of improving paper quality not only directly improves the product, but also reduces the use of low-quality raw materials when it is sufficient to produce conventional items. The use of low-quality products and high-quality products in combination is permitted.

In addition, since this cationic cross-linked starch exhibits high cohesive strength, it is used not only in the paper manufacturing industry but also in other industries that utilize such cohesive properties, such as flocculants for water purification, inorganic
It is clear that it can be used as a flocculant for fiber forming. Furthermore, since this cationic crosslinked starch is a polymer electrolyte, it can also be used as an antistatic agent.

Claims (2)

[Claims] (1) In a papermaking method in which a papermaking stock solution containing cellulose fibers or cellulose fibers and an inorganic filler is made into paper, dehydrated, and then dried, the papermaking stock solution contains 0.00001-0.
A cationic crosslinked starch having a degree of crosslinking of 1 and a degree of cationic group substitution of 0.01 to 0.1 is added to the cellulose fiber in the papermaking stock solution or the total amount of the cellulose fiber and the inorganic filler by 0.05%.
A papermaking method characterized by adding ~5.0% by weight. (2) In a paper manufacturing method in which a papermaking stock solution containing cellulose fibers or cellulose fibers and an inorganic filler is made into paper, dehydrated, and then dried, the total amount of cellulose fibers or this and an inorganic filler in the stock solution is added to the papermaking stock solution. Against, 0.000
Cationic crosslinked starch having a degree of crosslinking of 0.01 to 0.1 and a degree of cationic group substitution of 0.05 to 0.5
．． 0% by weight and anionic aqueous silica sol (SiO_2
A method for making paper, characterized in that 0.01 to 5.0% by weight of bentonite, a water-soluble anionic polymer, or a mixture thereof are added.