JPH039238B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing paper that improves the yield of fine fibers during paper making and printability. In printing papers such as wood-free paper, medium-quality paper, and coated paper, kaolin clay, talc, and TiO are generally used to improve optical properties such as paper whiteness and opacity, and the finish after printing. Inorganic fillers such as ₂ and organic fillers such as urea fillers are used. In the production of this type of paper, retention improvers or water-based improvers are usually used in combination to improve filler retention efficiency in the sheet, reduce the amount of filler flowing into white water, and reduce wastewater pollution loads. It's on. Particularly in recent years, the prices of papermaking raw materials, including fillers, have soared, and wastewater standards have become more stringent, making it important to improve the yield of fillers, sizing agents, etc. from both an economic and environmental standpoint. This also applies to newsprint containing mechanical pulp. In addition, in terms of production at paper mills, with the development of paper machines, high-speed, high-productivity paper machines (twin wire, etc.) have been introduced. Filler yield tends to deteriorate due to shear forces. On the other hand, looking at recent trends in paper products, there is a trend toward lighter weight for the purpose of saving resources, saving energy, and reducing costs. When the weight of paper is reduced, its strength and optical properties are reduced, and in particular, the reduction in opacity is manifested as a significant defect in the finish of printed matter. Therefore, as a method to improve this problem, increasing the amount of filler in the paper has conventionally been attempted, but it is known that as the amount of filler added increases, the yield on the wire deteriorates. In other words, in the paper and pulp industry, in the future,
It is expected that paper machines will become faster and white water will become more closed due to wastewater regulations, and as we increase the amount of filler used to reduce weight in order to save resources, it is necessary to improve the yield of filler. Improving the method is considered to be an extremely important technology in terms of economy, quality, and environmental improvement. Conventionally, a block forming method based on the agglomeration effect has been known as a method for improving filler retention and water properties. In other words, fillers and fine fibers are normally negatively charged in an aqueous suspension, and are thought to have a low yield on the wire because they electrically repel each other, disperse as fine particles, and do not form flocs. It is being As a way to increase yield,
First, an inorganic or organic low molecular weight cationic substance (such as alum) is added to the surface of the filler and fine fibers to neutralize negative charges, reduce electrostatic repulsion, and form microflocs. Thereafter, a method is generally known in which a cationic or nonionic high molecular weight retention aid is added to crosslink the microflocs to form macroflocs. For this purpose, low molecular weight cationic substances include inorganic substances such as alum (aluminum sulfate) and polyaluminum chloride, organic substances such as cationic starch, polyamide polyamines and their derivatives, and high molecular weight retention aids. As,
Nonionic, anionic, or cationic polyacrylamide derivatives are commonly used. However, in addition to pulp and filler, there are many impurities present in papermaking white water.
For example, in the case of newsprint, wood extracts derived from wood (lignin, resin acids, hemicellulose, etc.),
In printing paper, impurities such as denatured products of unfixed sizing agents, or latex and modified starch derived from waste paper in coated base paper, exist in a colloidal or dissolved state. There are also polyvalent metal salts such as iron, aluminum, calcium, and zinc. Therefore, when the retention aids are added, these aids first react with impurities, e.g., with cationic retention aids, before adsorbing to the surface of the fine fibers and fillers and creating crosslinks. , the amount of cations is wasted, and the spreading of the molecular chain of the linear polymer chain in the solution is suppressed, resulting in a decrease in crosslinking performance and failure to fully exhibit the yield improvement effect. As a method of eliminating the inhibiting effect of such impurities and improving yield, a method of using bentonite clay and nonionic polyacrylamide in combination is known. In other words, JP-A-55-
As described in Publication No. 152899, it is known that when applied to systems containing a large amount of mechanical pulp such as newsprint, the yield can be improved due to the effect of removing impurities derived from wood extracts. ing. In addition, U.S. Patent No. 3,052,595 discloses that 1 to 20 water-swellable bentonite clays are mixed in white water.
A method is disclosed for improving the yield of fillers and fine fibers such as kaolin clay, talc, and TiO ₂ by adding % and using nonionic polyacrylamide in combination. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing paper in which the yield of fine fibers and filler, when used, is further improved than in conventionally known methods. That is, to summarize the present invention, in a method for manufacturing paper from a paper stock suspension, an inorganic substance having a cation exchange ability is used in the step of preparing the paper stock suspension, and then The following general formula () was obtained: (In the formula, R ₁ represents hydrogen or a methyl group, R ₂ represents a divalent hydrocarbon group, and M represents hydrogen or another cation.) Contains acrylamide structural unit, molecular weight 100,000 to 2,000
The present invention relates to a method for producing paper, which comprises adding an anionic copolymer of 10,000 yen and then papermaking. Among the examples of inorganic substances having cation exchange ability used in the present invention, the main ones include bentonite, zeolite, activated clay (for example, Silton manufactured by Mizusawa Chemical), and diatomaceous earth (for example, Radiolite manufactured by Showa Chemical Industry). There are aluminum, calcium or magnesium salts of synthetic silicate (e.g. Zeolex manufactured by Huber), but from the state of papermaking white water,
It is necessary to have cation exchange ability. Those having a cation exchange capacity of 30 to 200 meq/100g, preferably 50 to 150 meq/100g show a yield improvement effect. The amount of these substances added is 1 to 10% per pulp.
The weight percent is preferably 1 to 5 weight percent. 2% by weight
When the above additives are added, even when they are added alone, they exhibit the effect as a filler and are effective in improving optical properties and printability. Therefore, the present invention does not necessarily require the addition of conventional fillers. On the other hand, the anionic copolymer containing the structural unit represented by the above formula and the acrylamide structural unit used in the present invention is a linear and water-soluble copolymer. In the formula, R ₁ is preferably hydrogen. _R2 is
Any of aliphatic, alicyclic and aromatic divalent hydrocarbon groups may be used. Examples include methylene, ethylene, propylene, butylene, hexylene, phenylene, tolylene, xylylene, naphthylene, cyclohexylene,

【formula】

【formula】

[Formula] etc., but a lower alkylene group is preferred. The cation of M is preferably sodium or potassium. As the unit of the formula, from the viewpoint of economy, ease of polymerization, and effectiveness, 2-acrylamide-2-
Most preferred are those derived from the sodium or potassium salts of methyl-propanesulfonic acid. In the copolymer according to the present invention, the proportion of the structural unit of the formula and the acrylamide unit may be 2 to 90 mol% of the unit of the formula and 10 to 98 mol% of the acrylamide unit,
Preferably, the units of the formula are 3 to 50 mol% and the acrylamide units are 50 to 97 mol%. The minimum molecular weight of the copolymer is 100,000, but the larger the molecular weight, the higher the yield improvement effect. However, if the molecular weight is too large, the texture of the paper tends to deteriorate, so the molecular weight is preferably in the range of 100,000 to 20,000,000. In addition, the copolymer of the present invention may contain up to about 20 mol% of other water-soluble copolymerizable monomers and/or up to about 10 mol% of water-insoluble copolymerizable monomers. may have been done. Examples of water-soluble copolymerizable monomers include acrylic acid or its salt, methacrylic acid or its salt, methacrylamide,
These include N-methylolated acrylamide, N-methylolated methacrylamide, N-lower alkyl acrylamide, N-lower alkyl methacrylamide and styrene sulfonate. Examples of water-insoluble copolymerizable monomers include acrylonitrile, vinyl chloride, vinyl acetate, styrene, lower alkyl acrylate, lower alkyl methacrylate, and diacetoacrylamide. The copolymer in the present invention can be produced by bulk polymerization, aqueous solution polymerization, suspension polymerization, or emulsion polymerization. Polymerization is promoted with polymerization initiators commonly used in aqueous systems, such as peroxides, persulfates, persulfate-bisulfites, and the like. The amount of the copolymer added is 0.005% by weight or more of the dry polymer based on the pulp, and generally 0.1% by weight or less, but preferably 0.01 to 0.07% by weight. If the amount added is more than 0.1% by weight, the texture will deteriorate, which is not preferable. The method of the present invention is applicable to chemical pulps such as kraft pulp (KP) and sulfite pulp (SP), mechanical pulps such as ground pulp (GP), thermomechanical pulp (TMP), and refined ground pulp (RGP), and semi-chemical pulps. It can be applied to any pulp such as (SCP), waste ink pulp (DIP), etc. Papers obtained from these pulps include newsprint, gravure paper, medium-quality paper,
The main ones are wood-free paper and coated base paper. In the method of the present invention, any filler that is commonly used as a filler for paper can be used as the optionally added filler. Namely, cationic clay, talc, synthetic silicates including hydrous silicic acid,
Applicable materials range from inorganic fillers such as TiO ₂ , calcium carbonate, magnesium carbonate, barium sulfate, and zinc sulfide to organic fillers made from urea-formalin. The addition rate of such filler to the pulp is not particularly limited, and is generally in the range of about 1 to 80% (absolute dry weight) to the pulp. 1 to 10 for newsprint
%, preferably 1 to 3%, and no filler may be used. For medium quality paper and high quality paper, generally 1~
80%, preferably 5-30%. To specifically explain the operating procedure of the method of the present invention,
0.5 to 5.0% by weight (preferably 1% by weight, including raw material pulp)
A predetermined amount of slurry of an inorganic substance having cation exchange ability according to the present invention, which has been previously dispersed with water such as industrial water to a concentration of 1 to 10% by weight, is added to an aqueous suspension having a concentration of 1 to 3% by weight. After stirring for 2 minutes to sufficiently adsorb impurities, add 0.1 to 1.0
% by weight (preferably 0.5% by weight or less) of the substantially anionic copolymer according to the present invention is added, and the whole is further diluted with water to a concentration of 0.3 to 1.0% by weight to form a paper. do. The location where the copolymer is added is not particularly limited, but it is usually desirable to add the copolymer between the fan pump and the stock inlet where strong hydraulic shearing force is not applied. Further, the method of adding the inorganic substance having cation exchange ability is not limited to the above-mentioned operation. If the conventional fillers mentioned above are used in the process according to the invention, an aqueous slurry of inorganic substances according to the invention is first added to the pulp suspension and then talc, clay, calcium carbonate or TiO ₂
Add the filler slurry mentioned above, or
A filler such as clay, calcium carbonate, or TiO ₂ and the substance may be mixed in a predetermined ratio in powder form in advance, and then dispersed in water for use. Furthermore, the substance may be added subsequently after addition of the filler. The present invention will be further explained below with reference to Examples.
The present invention is not limited to these. Example 1 A pulp stock containing 20 parts BKP, 30 parts TMP, 20 parts GP and 30 parts DIP is diluted with industrial water to a concentration of 1%. Add tap water to this pulp suspension in advance.
Add 1% Na-type bentonite clay diluted and dispersed to a concentration of 10% to the pulp (absolutely dry weight basis, hereinafter abbreviated as BD), and stir thoroughly with a lab stirrer to uniformly combine. Next, a nonionic polymer or a copolymer according to the invention, previously dissolved in deionized water at a concentration of 0.5%, is added to the pulp at a concentration of 0.05%.
(BD) Add and mix uniformly in the same way. after that,
The above 1% stock suspension is diluted to 0.3% with tap water and the freeness is determined according to the Tappi standard method. The higher the freeness value, the higher the yield improvement effect. The results are shown in Table 1. Note that the data used in this example (including the comparison column)
The Na-type bentonite claim is a Kunimine industrial product (trade name: Kunibond), and the nonionic polyacrylamide (hereinafter abbreviated as nonionic PAM) has a molecular weight (measured by the intrinsic viscosity method, the same hereinafter) of 8 million. Polyethylene oxide (hereinafter abbreviated as PEO) has a molecular weight of 2 million, and the copolymer according to the present invention (hereinafter abbreviated as SO ₃ -PAM) contains 80 mol% acrylamide, 2 -A copolymer of 7 mol% sodium acrylamide-2-methylpropanesulfonate and 13 mol% sodium acrylate, with a molecular weight of approximately
7 million.

[Table] Example 2 Using the same pulp suspension as in Example 1, the solid content in the liquid after freeness measurement was measured,
The yield improvement effect was determined. A lower solid content in the liquid indicates a better yield of raw material on the paper machine wire. The types and addition rates of the polymers and inorganic substances used in the evaluation were the same as in Example 1. The results are shown in Table 2.

[Table] Example 3 NBKP and LBKP were beaten to respective freenesses of 600 ml and 450 ml using a lab-scale Holland beater, and blended at a ratio of 20% NBKP and 80% (by weight) LBKP to obtain raw material pulp. This raw material pulp was diluted with tap water to a concentration of 1%, and inorganic substances were previously dispersed in tap water to a concentration of 5%.
Na-type bentonite clay (same as in Example 1) was added at 1% (BD) to the pulp and mixed using a lab stirrer. Then, as an internal filler, heavy calcium carbonate (hereinafter abbreviated as charcoal) previously dispersed in tap water to a concentration of 10% (BD) and 60% talc to pulp (BD) were added and stirred in the same manner. and mixed uniformly. In this stock suspension, the nonionic polymer described in Example 1 or SO ₃
Add 0.05% (BD) of PAM to the pulp and stir gently to mix uniformly. Then, after diluting this stock suspension with tap water to a concentration of 0.8%,
2 samples were taken and dropped onto a tray covered with 60 mesh wire while being rapidly stirred, and the liquid that flowed out through the wire was collected and the filler concentration therein was measured. The lower the weight of the filler contained in the white water, the better the yield on the paper machine wire. For comparison, cationic polyacrylamide (abbreviated as cationic PAM) (molecular weight
2 million, degree of cationization 20 mol%) is also shown. These results are shown in Table 3.

[Table] Example 4 In a 1% suspension of the same pulp as in Example 1, Na-type bentonite clay (same as in Example 1) and zeolite (Huber Co., Ltd.) were diluted and dispersed in advance with tap water at a concentration of 10%. 1% of the pulp
(BD) was added and mixed uniformly in the same manner, and then 0.05% (BD) of nonionic PAM or SO ₃ -PAM described in Example 1 was added and mixed relative to the pulp. After diluting this stock suspension to 0.3% with tap water, freeness was measured by the Tappi standard method, and the solid content concentration in the liquid was measured. The results are shown in Table 4.

[Table] Example 5 Example 4 was prepared by dispersing tap water to a 10% concentration in a 1% suspension of the same pulp as in Example 3.
After adding 1% (BD) of Na-type bentonite clay, zeolite or activated clay to the pulp and mixing it uniformly, as an internal filler,
Charcoal dispersed at a concentration of 10% is mixed with 60% of the pulp (B.
D) Added and uniformly dispersed. In this stock suspension, the nonionic PAM or SO ₃ -PAM described in Example 1 dissolved in ion-exchanged water was added at a rate of 0.05% per pulp.
% (BD) after adding and uniformly dispersing, 0.8%
The filler was diluted to a certain concentration and passed through a 60-mesh wire in the same manner as in Example 3, and the weight of the filler in the liquid that flowed out was measured. The results are shown in Table 5.

[Table] Example 6 The same treatment as in Example 1 was performed except that SO ₃ -PAM was replaced with a copolymer of 95 mol% acrylamide and 5 mol% sodium 2-acrylamido-2-methylpropanesulfonate. Freeness was measured. The freeness value was 170ml. As is clear from the descriptions of the above Examples and Comparative Examples, according to the method of the present invention, fine fibers derived from mechanical pulp and fine fibers that are added to the stock suspension as necessary for the purpose of improving printability are used. In addition to improving the retention of the filler on the wire, it also improves water drainage and improves the printability of the paper.

Claims (1)

[Claims] 1. A method for producing paper from a stock suspension,
In the process of preparing a paper stock suspension, an inorganic substance having cation exchange ability is used, and then the following general formula () is added to the obtained paper stock suspension: (wherein, R ₁ represents hydrogen or a methyl group, R ₂ represents a divalent hydrocarbon group, and M represents hydrogen or another cation), and 50 to 97 mol% of A method for producing paper, which comprises adding an anionic copolymer containing an acrylamide structural unit and having a molecular weight of 100,000 to 20 million, followed by papermaking.