JPH0140159B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paper quality improvement method for improving wet and dry paper strength. According to the present invention, even when the amount of sulfate is reduced to 1/2 to 1/4 compared to the conventional paper strength strengthening method using an anionic paper strength agent and sulfuric acid band, an excellent dry and wet paper strength strengthening effect can still be achieved. Moreover, it is recognized that the broken paper can be easily disintegrated. Conventionally, when a partially hydrolyzed polyacrylamide derivative is used as a paper strength agent, a large amount of sulfuric acid has been used as a fixing agent. This method has been excellently adapted to the most commonly used papermaking methods to date. In other words, sulfate band is indispensable for rosin-based sizing agents, and sulfate band is also widely used for purposes such as improving aqueous properties and preventing pitch trouble. On the other hand, since the oil crisis, the idea of saving energy and resources has taken hold, and from the standpoint of environmental protection, an increasing number of paper mills are adopting systems that recirculate and reuse wastewater from the papermaking process. This system is fraught with the risk of deteriorating water quality if water is not managed adequately. One of the measures to prevent water quality deterioration is to improve the fixation of papermaking chemicals to the paper stock, or to reduce the amount of these chemicals added as much as possible to reduce the concentration of free chemicals present in the paper stock suspension. There are ways to reduce this. As mentioned above, at present, a large amount of sulfuric acid is added to the stock suspension. The aluminum aco complex in the sulfate band reacts with anionic paper strength agents, rosin-based sizing agents, etc., some is directly adsorbed to the pulp, and most stays in the paper, but the sulfate group, which is a counterion, It is difficult for the sulfuric acid group to accumulate in the paper, and if the water system for papermaking is closed, it is inevitable that the concentration of sulfate groups will gradually increase. As a result, a situation occurs in which the added paper strength enhancer becomes less effective as a sizing agent.
In order to compensate for the lack of effectiveness, sulfuric acid is added, and the vicious cycle repeats. Although cationic paper strength enhancers that can be fixed to pulp without using sulfuric acid in combination have been developed, the effects are still insufficient. In addition, amphoteric type paper strength enhancers are also commercially available, but they have problems with the storage stability of the product and their effects are similar to those of cationic ones. In order to improve these cationic or amphoteric paper strength agents, there are examples of attempts to modify the carbamoyl group in the molecule with glyoxal to make the polymer reactive and improve the paper strength strengthening effect. Among them, examples of cationic polymers modified with glyoxal are disclosed in Japanese Patent Publication No. 44-26670 and U.S. Patent No. 3,556,932, and examples of modified amphoteric polymers with glyoxal are disclosed in Japanese Patent Publication No. 1983-26670 and U.S. Patent No. 3,556,932.
There are inventions such as those described in Publication No. 44762. The product of the above-mentioned Special Publication No. 44-26670 is acrylic acid 2
- Dimethylaminoethyl and acrylamide are copolymerized, quaternized with methyl chloride, benzyl dimethyl sulfate, etc., and then modified with glyoxal. In US Pat. No. 3,556,932, acrylamide and dimethyldiallylammonium chloride are copolymerized and then modified with glyoxal. Further, in Japanese Patent Publication No. 54-44762, 2-dimethylaminoethyl methacrylate is quaternized with epichlorohydrin, and an amphoteric polymer copolymerized with acrylamide and acrylic acid is modified with glyoxal. These cationic or amphoteric type polymers before modification with glyoxal use relatively expensive 2-dimethylaminoethyl methacrylate as a monomer and dimethyldiallylammonium chloride, and quaternization of cationic groups is particularly difficult. Unless it is in a high pH range, it does not directly affect the paper strength enhancement effect, and if we look at the most common papermaking process currently, when calcium carbonate is used as a coating material, the coated base paper is made at a neutral pH of about 8. Apart from this, sulfuric acid bands are often mixed in due to pitch troubles, water-based problems, the effects of rosin sizing agents, and due to the circulation and reuse of papermaking water. There are very few examples. Furthermore, the most important point is that according to experiments conducted by the present inventors, 2-dimethylaminoethyl methacrylate or dimethyldiallylammonium chloride is a negative factor for paper strength.
That is, as the copolymerization ratio of these two monomers with respect to acrylamide is increased, the paper strength increasing effect decreases, and the homopolymer of these two monomers shows no effect at all. Even in the case of an amphoteric polymer containing acrylic acid, as the cation copolymerization ratio increases, the paper strength enhancement effect decreases. Considering the above-mentioned points, the present inventor has determined that although sulfuric acid is essential, it is necessary to reduce the amount of sulfuric acid or paper strength enhancer in order to prevent the quality of water from deteriorating. Even if the amount added is reduced, an excellent paper strength enhancing effect must be exhibited. In addition, in order to add cationic groups to the paper strength enhancer used, we have been considering a new paper strength strengthening method that does not involve copolymers of 2-dimethylaminoethyl methacrylate or dimethylallylammonium chloride. (However, R ₁ is CH ₃ or C ₂ H ₅ , R ₂ is H or CH ₃ ,
X is COOH or CONHCH ₂ SO ₃ H or
CONH・C(CH ₃ ) ₂ CH ₂・SO ₃ H) When the ratios of (A), (B), and (C) above are a, b, and c, b/(a+b+c)=0.02 to 0.2, c/b=
0.2~0.7, and 10% aqueous solution viscosity (25℃,
1NNaCl) in an aqueous polymer solution with a pH of 10 cp or more.
5 to 8, by adding a water-soluble polymer obtained by reacting glyoxal at a molar ratio of 0.03 to 0.3 to a during the papermaking process, and adding sulfuric acid to the conventional anionic paper strength enhancer. Even if the amount of sulfuric acid band used is reduced to 1/2 to 1/4 compared to the reinforcing method, it still shows an excellent effect of increasing dry and wet paper strength, and it is easy to disintegrate the broken paper, and it also prevents contamination with white water, etc. The present invention was achieved by discovering that the effect is not easily affected even if the product is damaged. The water-soluble polymers used in the present invention before being modified with glyoxal are acrylamide and acrylic acid;
It can be obtained by modifying a copolymer of methacrylic acid or 2-acrylamide with 2-methylpropanesulfonic acid, a partially hydrolyzed derivative of polyacrylamide, a sulfomethylated derivative, or the like by Mannitz reaction. The Mannitz reaction modification rate is that where the total repeat unit of the polymer is lower than 0.05, that is, where the degree of cationization is low, the adsorption power to the paper stock is weak, and there is a lot of loss into the paper stock slurry, which leads to a decrease in the quality of the water used. Connection is not a good thing. In addition, where the degree of cationization is higher than 0.2, not only the paper strength enhancement effect is not good, but also
There is a risk of agglomerating the stock slurry and damaging the paper structure. Anionization degree relative to cationization degree is 0.3 to 0.6
A range of is preferred. When the degree of anionization relative to the degree of cationization is lower than 0.2, properties as an amphoteric polymer are difficult to exhibit, and the paper strength enhancement effect is not excellent. On the other hand, when this ratio is higher than 0.7, the effect is poor and the storage stability of the product is also poor. In addition, if this ratio is higher than 1.0, that is, if the degree of anionization is excessive relative to the degree of cationization, there will be little effect in formulations with reduced sulfate bands, that is, in the range from pH 6 to neutrality, and the objective of the present invention will not be achieved. Not suitable. The molar ratio of glyoxal reacted with free carbamoyl groups remaining in the molecule after the Mannitz reaction will be described. When the degree of cationization and anionization of the polymer used in the present invention is changed as described above, the carbamoyl group becomes 0.98
exists in the range of 0.66. Glyoxal can be reacted with this carbamoyl group in a molar ratio of 0.03 to 0.3, preferably 0.05.
~0.2 range. Further, in the range below 0.3, the effect of glyoxal modification is difficult to appear, and the paper strength enhancement effect is also low. If it is higher than 0.3, the reaction is too fast, causing problems in production, and the storage stability of the product is also poor. Furthermore, regarding the pH during modification with glyoxal, the unmodified aqueous polymer solution must first be adjusted to an appropriate pH range. The unmodified polymer is
Reacts with glyoxal in the PH range of 1 to 12, but the PH
In the range lower than 5, the reaction is very slow and it takes a long time to reach the desired viscosity, which is impractical and the PH
When the temperature is higher than 8, the reaction is too rapid and the polymer tends to gel, making it virtually impossible to obtain the desired water-soluble polymer. Therefore, a pH range of 5 to 8 is preferable. The viscosity of the polymer for this glyoxal modification is 10 cp (25° C., 1N NaCl) in a 10% aqueous solution, but is preferably in the range of 20 cp or more and 500 cp or less.
When it is higher than 500cp, when glyoxal denatures,
The viscosity increases sharply and the polymer may gel, which is undesirable, and if it is lower than 10 cp, the effect will be small. Furthermore, the water-soluble polymer used in the present invention can improve not only the strength of paper but also other properties of paper. For example, when a rosin-based sizing agent or other anionic or cationic sizing agent is used in combination, the sizing degree can be improved, and when a filler is used, the yield rate can be improved, and at the same time, the surface strength can also be improved. Also, the water resistance during paper making is improved. The water-soluble polymer used in the present invention can also be used by quaternizing its Mannich base with dimethyl sulfate, diethyl sulfate, ethylene oxide, propylene oxide, or the like. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples. Production example of water-soluble polymer: 5 mol% acrylic acid, 95 mol% acrylamide
copolymer (10% aqueous solution viscosity 95 cp, 1N
Place 130 g of a 20% aqueous solution of (in NaCl) in a 500 ml separable flask and attach it to a stirrer. While stirring, add 0.72 g of sodium hydroxide dissolved in 10 g of water, and then add 50% dimethylamine aqueous solution.
Add 4.07 g (13 mol % based on the carbamoyl group in the polymer) and 2.82 g of 37% formalin solution (10 mol % based on the carbamoyl group in the polymer) in this order, and react at 40 to 45°C for 3 hours. . Then 47g of water
Remove the separable flask from the stirrer, transfer to a 300 ml beaker, add concentrated sulfuric acid dropwise while stirring with a magnetic stirrer, and adjust the pH of the solution to 7.0 using a PH meter. 40% glyoxal aqueous solution adjusted to PH7.0 separately
4.5g (10 mol% based on remaining carbamoyl group)
Add this, transfer to the separable flask again, and attach it to the stirrer. At this time, the concentration before the Mannitz modification of the polymer is 13%. Continue the reaction at 40-45℃ 2
After 15 minutes, the viscosity of the 10% aqueous solution of the polymer (assuming the concentration before Mannitzchi modification) reached 520 cp, so the solution was lowered to pH 2 with concentrated sulfuric acid to stop the reaction. This is used as sample No. 1 and water is added to make it 10% and stored. At the same time, the degree of cationization of the water-soluble polymer was changed, the ratio of the degree of cationization to the degree of anionization was changed, the ratio of glyoxal reacted with the carbamoyl group was changed, and the viscosity of the polymer before Mannitz reaction modification was changed. those that are amphoteric but not modified with glyoxal, those that are modified with Mannitz only and modified with cationic glyoxal, and those that are modified with acrylic acid and methacrylic acid 2-
Various types of polymers, such as glyoxal-modified water-soluble polymers of dimethylaminoethyl and acrylamide, were produced by similar methods. The results are shown in Table 1.

【table】

[Table] No Mannitz reaction modification was performed, but glyoxal modification was performed after the copolymerization reaction.
Example 1 Using the water-soluble polymer synthesized in Production Example, the following paper making and paper strength tests were conducted. A mixture of cardboard and core base paper at a ratio of 1:1 by weight was disintegrated and beaten with CSF to 400 ml to form a 0.6% slurry. Next, pour this slurry into beaker 1.
Take 400ml and add sulfuric acid band (stirring for 60 seconds) and water-soluble polymer (stirring for 60 seconds) in this order while stirring with a magnetic stirrer until the basis weight is 120.
g/m ² paper was made, the dry and wet tensile strengths were measured, and the tearing length was calculated. At the same time, an anionic paper strength enhancer and a sulfuric acid band were added to the paper, and a paper strength test was also carried out and compared with the method according to the present invention. The results are shown in Table 2.

[Table] As is clear from Table 2, according to the method of the present invention, the effect remains almost unchanged even when the concentration is reduced to 1% sulfate (i.e., PH6.5), whereas with the anionic paper strength agent, sulfate 1% % has no effect at all. Example 2 A test similar to Example 1 was conducted. acrylic acid,
Samples No. 16, 17, and 18 in which the ratio of anionization degree to cationization degree was changed in a copolymer of 2-dimethylaminoethyl methacrylate and acrylamide
A comparative test was conducted using Sample No. 1 used in the present invention. The results are shown in Table 3.

Table 3 shows that all of the polymers using 2-dimethylaminoethyl methacrylate as the cationic group are inferior in effect to the polymers used in the present invention. Example 3 The same test as in Example 1 was conducted on copolymers of acrylic acid, 2-dimethylaminoethyl methacrylate, and acrylamide, with samples Nos. 17, 18, and 19 having varying degrees of cationization used in the present invention. A comparative test was conducted using No. 1. The results are shown in Table 4.

[Table] Polymers using 2-dimethylaminoethyl methacrylate as the cationic group are polymer sample No. used in the present invention even if the degree of cationization is changed.
It can be seen that all of them are less effective than 1. Example 4 A test similar to Example 1 was carried out on sample Nos. 1, 2,
3 and 4, and the effects were observed by changing the ratio between the degree of anionization and the degree of cationization. At the same time, Sample No. 5, which was a cationically modified polymer modified with glyoxal, and a commercially available polyamide amine type wet paper strength enhancer were also tested and compared. The results are shown in Table 5.

【table】

[Table] As is clear from Table 5, cationically modified polymers are less effective than amphoteric polymers, and the ratio of anionization degree to cationization degree is outside the scope of the present invention.
Sample No. 4, which is 1.5, is shown to be significantly less effective. Example 5 Tests similar to those in Example 1 were conducted on Samples No. 1, No. 6, No. 7, and No. 8 to determine the effect of changing the viscosity of the polymer before Mannitz reaction modification. Observed. The results are shown in Table 6.

【table】

[Table] As is clear from Table 6, sample No. 6 has too high a viscosity and is therefore less effective. Example 6 Samples No. 1, 9, 10, and 11 were tested in the same manner as in Example 1 to examine the effects of varying the degree of cationization. Table 7 shows the results.
Shown below.

[Table] As is clear from Table 7, No. 10 having a degree of cationization of 30 mol %, which is outside the range of the present invention, is inferior in its effect. Example 7 Example 1 for samples 1, 12, 13, 14, and 15
A similar test was conducted to examine the effects of varying the molar ratio of glyoxal to carbamoyl groups. At the same time, sample No. 12 which had not been modified with glyoxal was also tested.
The results are shown in Table 8.

[Table] As is clear from Table 8, sample No. 12, which is not modified with glyoxal, is less effective, and sample 15, which is outside the scope of the present invention, is not as effective even if the molar ratio of glyoxal to carbamoyl groups is increased. The storage stability was also poor.

Claims (1)

[Claims] 1 (However, R ₁ and R ₂ are CH ₃ or C ₂ H ₅ , R ₃ is H or CH ₃ , and X is COOH or -CONHCH ₂ SO ₃ H or -CONHC(CH ₃ ) ₂ CH ₂ SO ₃ H) When the above (A), (B), and (C) are repeated and their respective ratios are a:b:c, b/(a+b+c)=
0.02 to 0.2, c/b = 0.2 to 0.7, and a 10% aqueous solution viscosity (25°C, 1N NaCl) of 10 cp or more, pH 5 to 8, glyoxal at a molar ratio of 0.03 to 0.3 to a. After reacting, the pH is
A method for improving paper quality for improving wet and dry paper strength, characterized by adding a water-soluble polymer obtained by adjusting it to 2.5 or less during a papermaking process.