JPH0149839B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved polyacrylamide-based paper strength agent, and more particularly, the present invention relates to an improved polyacrylamide-based paper strength agent, and more particularly, the present invention relates to an improved polyacrylamide-based paper strength agent, which contains a specific water-soluble copolymer mainly composed of acrylamide and/or methacrylamide, and in particular contains no or a low amount of sulfuric acid. The present invention relates to a papermaking additive for increasing paper strength that can exhibit an excellent paper strength increasing effect in a papermaking system with an additive rate. In the paper manufacturing industry, as part of energy conservation and environmental measures, it has become inevitable to close the paper manufacturing process, that is, to reduce the amount of wastewater.
The addition rate of sulfuric acid band, which has traditionally been used,
Therefore, there is a desire for a drug or a combination of such drugs that can exhibit sufficient effects even when sulfuric acid is added at a low rate or without the addition of sulfuric acid. By the way, various copolymers mainly composed of acrylamide have been known as paper strength enhancers that are stable in terms of properties and performance. Copolymers can be roughly divided into three types, but first, anionic copolymers include
The desired effect cannot be achieved unless a fixing agent such as sulfuric acid is used in combination, so it is essential to use the cationic copolymer in an acidic region. Although paper making is possible over a wide range of pH ranges, it cannot be said that the effect of increasing paper strength is generally sufficient. In addition, ampholytic copolymers can be used as paper strength enhancers that can be used in a broader pH range than cationic copolymers, regardless of whether or not a fixing agent such as sulfuric acid is used. It has been. However, even with such amphoteric copolymers,
For example, conventional ones, such as those obtained from acrylamide, an α,β-unsaturated monocarboxylic acid such as acrylic acid, and a cationic monomer such as dimethylaminoethyl methacrylate, also
For paper-making systems in which the paper strength enhancement effect is not sufficient, especially in papermaking systems with a low addition rate of sulfuric acid band, or in papermaking systems that do not use this sulfuric acid band at all, the desired and constant The reality is that it is difficult to impart paper strength. However, as a result of intensive research by the present inventors in order to improve and eliminate these drawbacks or difficulties in the prior art, the present inventors found that by using α,β-unsaturated dicarboxylic acid instead of α,β-unsaturated monocarboxylic acid, The resulting amphoteric copolymer is mainly composed of (meth)acrylamide, and further contains α,β-
Amphoteric copolymers obtained by copolymerizing unsaturated dicarboxylic acids (salts) and water-soluble cationic monomers (salts) are used to create anionic polyacrylamide, cationic polyacrylamide, We have found that compared to amphoteric polyacrylamide that uses α,β-unsaturated monocarboxylic acid as an anionic monomer, it exhibits an excellent paper strength-enhancing effect, especially in papermaking systems with no or low addition of sulfate. As a result, we have completed the present invention. That is, the present invention uses 0.1 to 20 mol% of water-soluble cationic monomers and/or their salts (a), α,β-unsaturated dicarboxylic acids and / or 0.1 to 15 mol% of their salts (b) and 99.8% of acrylamide and/or methacrylamide (c)
The present invention provides a paper strength enhancer comprising a water-soluble copolymer obtained as an essential constituent monomer in an amount of 65 mol %. Here, typical examples of the cationic monomer (a) component include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, or diethylaminopropyl (meth)acrylamide. tertiary amino group-containing vinyl monomers or their salts with inorganic or organic acids such as hydrochloric acid, sulfuric acid, or acetic acid; Examples include vinyl monomers containing quaternary ammonium salts obtained by reaction with a curing agent. Typical examples of the anionic monomer (b) component include maleic acid, fumaric acid, itaconic acid, or citraconic acid, or alkali metal salts or ammonium salts thereof such as sodium or potassium salts. Further, among acrylamide and methacrylamide as the component (c), acrylamide is preferable from an economic point of view, but it goes without saying that these may be used in combination. By the way, why does the amphoteric copolymer, which is the paper strength enhancer of the present invention obtained using the above-mentioned essential constituent monomer components, give particularly excellent paper strength, and why does the addition rate of sulfuric acid band increase? Although a clear answer regarding the mechanism has not been obtained as to whether a system with low sulfuric acid content or even a system without the addition of sulfuric acid gives excellent paper strength, the following possibilities are currently considered. . That is, since dicarboxylic acid is used as the anion moiety of the amphoteric polyacrylamide copolymer, one reason is that the carboxyl group in this dicarboxylic acid has a
It is presumed that this is because stronger bonding strength is achieved through ionic bonds with cationic functional groups or with aluminum ions derived from sulfate bands.Secondly, the copolymer It is possible to reduce the amount of anionic monomer to be introduced into the paper due to its polyfunctionality compared to monocarboxylic acids, and as a result, it contributes to improving and strengthening paper strength. This is presumed to be because it leads to an increase in the visible (meth)acrylamide moiety. Although it is basic, it is believed that the paper strength enhancing effect of this type of polyacrylamide paper strength enhancer is mainly attributable to hydrogen bonding between the amide groups in the polymer and the hydroxyl groups of cellulose fibers. There is. In addition, in order for the paper strength enhancer to effectively exhibit paper strength, it goes without saying that it needs to be adsorbed or fixed on the cellulose fibers or fine fibers that make up the paper. Therefore, in order to fix a paper strength agent to cellulose fibers, which are generally negatively charged, it is necessary to introduce a cationic functional group into the paper strength agent itself or to use a fixing agent such as sulfuric acid. It is necessary to introduce anionic functional groups for the purpose of fixation, and also to introduce both cationic and anionic functional groups in order to achieve a synergistic effect between both functional groups. . In this regard, in the paper strength enhancer of the present invention, both a cationic functional group and an anionic functional group are introduced in order to increase the fixation rate to the cellulose fibers or fine fibers constituting the paper. but,
The presence of these cationic moieties and cationic moieties
Since the amide moiety, which is effective in developing paper strength, is reduced accordingly, an optimum range is naturally set for the amount of both of these functional groups introduced. Thus, the paper strength enhancer of the present invention has a cationic monomer (a) component of 0.1 to 20 mol%, preferably 1 to 15% by mole.
mol%, anionic monomer (b) component is 0.1 to 15 mol%, preferably 1 to 10 mol%, and (meth)acrylamide (c) component is 99.8 to 65 mol%, preferably 98 to 75 mol%. It can be obtained by copolymerizing these essential constituent monomer components. At that time, a part of the anionic monomer (b) component, that is, the α,β-unsaturated dicarboxylic acid and/or its salts, is added to an extent that does not reduce the effects of the present invention.
α, such as (meth)acrylic acid or crotonic acid,
Of course, it can be replaced with β-unsaturated monocarboxylic acids and/or their salts such as sodium, potassium or ammonium, or in combination with each of the above components (a), (b) and (c). Polymerizable nonionic monomers such as (meth)acrylonitrile, methyl (meth)acrylate, butyl (meth)acrylate, or styrene may not be introduced to the extent that they do not impair the paper strength enhancement effect or the water solubility of the polymer. There is absolutely no problem. Thus, the paper strength enhancer of the present invention can be prepared using the following method. That is, a predetermined amount of the above (a), (b) and (c) is added to water containing a known and commonly used chain transfer agent such as isopropyl alcohol, allyl alcohol or sodium allylsulfonate.
component or, if necessary, α,β-unsaturated monocarboxylic acid and/or nonionic monomer to prevent hydrolysis during the polymerization reaction.
4 to 4.5, and a redox polymerization initiator in the form of a persulfate such as potassium persulfate or ammonium persulfate, or a combination of these persulfates and a reducing agent such as sodium bisulfite. , or 2,2′-azobis(2
-Amidinopropane) By adding a known and commonly used radical polymerization initiator such as an azo compound such as hydrochloride, stirring and heating in an inert gas, the desired water-soluble polyacrylamide copolymer is produced. A union is obtained. Next, the present invention will be specifically explained with reference to Examples, Comparative Examples, Applied Examples, and Comparative Applied Examples. In the following, all % means % by weight unless otherwise specified. The monomer abbreviations used in each table are as follows. AAm...acrylamide MAm...methacrylamide DM...dimethylaminoethyl methacrylate Q...2-hydroxy-3-methacryloxypropyltrimethylammonium chloride DP...dimethylaminopropyl methacrylamide MA...maleic acid IA...itaconic acid FA ... Fumaric acid AA ... Acrylic acid CA ... Crotonic acid MAA ... Methacrylic acid Examples 1 to 12 and Comparative Examples 1 to 5 30 in a neck flask
After weighing and adding 1.55 g of % maleic acid aqueous solution, 1.89 g of dimethylaminoethyl methacrylate, 54.59 g of 50% acrylamide aqueous solution, 4.16 g of isopropyl alcohol and 136.09 g of water, the pH was adjusted to 4.0 to 4.5 with 15% sulfuric acid aqueous solution. Then, oxygen in the reaction system was removed with nitrogen gas. Next, while stirring, 0.91 g of a 5% aqueous ammonium persulfate solution and 0.30 g of a 5% aqueous sodium acid sulfite solution were added as polymerization initiators, and the temperature was raised from room temperature to 75°C over 30 minutes, and then maintained at the same temperature. When kept for 5 hours, the non-volatile content is 15.3%, 25
A stable amphoteric copolymer aqueous solution having a Bruck-Field viscosity (hereinafter the same) at ℃ of 12,000 cps and a pH of 4.2 was obtained. Hereinafter, this will be abbreviated as paper strength agent (A-1). The above is considered as Example 1, and the remaining Examples 2 to 12 and Comparative Examples 1 to 5 are performed in the same manner as in Example 1, except that the composition of the constituent monomer components as shown in Table 1 is followed. The experiments were repeated, with the amounts of isopropyl alcohol and 15% sulfuric acid aqueous solution varying each time. The property values of the copolymers obtained in each Example and Comparative Example are summarized in the same table.

[Table] Examples 13 to 18 A target amphoteric copolymer aqueous solution (PH = 4.0 ± 0.5) was obtained in the same manner as in Example 1, except that the constituent monomer components were changed as shown in Table 2. Ta.
The property values of the amphoteric copolymer aqueous solutions obtained in each example are summarized in the same table.

【table】

[Table] Comparative Examples 6 to 15 A control amphoteric copolymer aqueous solution (PH=4.0±0.5) was obtained in the same manner as in Example 1, except that the constituent monomer components were changed as shown in Table 3. Ta. The property values of the amphoteric copolymer aqueous solutions obtained in each comparative example are summarized in the same table.

[Table] Application Examples 1 to 12 and Comparative Application Examples 1 to 15 Canadian Standard Freeness (hereinafter abbreviated as CSF) obtained from waste cardboard
2.5% slurry of beaten pulp with 390 ml of
0.5% sulfuric acid band to pulp (dry weight basis,
The same applies below), and then Example 1
Each paper strength enhancer obtained in Comparative Examples 1 to 12 and Comparative Examples 1 to 15 was added at a concentration of 0.4% based on the pulp. Thus, after stirring for 2 minutes, the pulp slurry was diluted to a concentration of 0.25%, stirred for another 1 minute, and then paper was made using a hand paper machine made by Noble & Wood (PH at the time of paper making was 6.0). Dry with a drum dryer at 110℃ for 1 minute,
The basis weight for each paper strength enhancer is 85±2g/ ^m2 and 172
Two types of handmade paper of ±3 g/m ² were obtained. For each paper stock with the former basis weight, the "specific bursting strength" according to JIS P-8112 and the "breaking length" according to JIS P-8113 are determined, and on the other hand, for each paper stock with the latter basis weight, JIS "Specific compressive strength" was measured according to P-8126. The results are summarized in Table 4. As is clear from the same table, it is known that the paper strength enhancing agent of the present invention has an excellent paper strength enhancing effect.

【table】

[Table] Application Examples 13 to 40 and Comparative Application Examples 16 to 35 Addition of 0.5%, 1.0%, and 2.5% of sulfuric acid based on the pulp to a 2.5% slurry of beaten pulp containing 95 ml of CSF obtained from used cardboard. Examples 8, 13 to 18 and Comparative Examples 7, 9,
Each of the paper strength enhancers obtained in steps 12 to 14 was added at 0.4% based on the pulp. Hereafter, Application Examples 1 to 12 and Comparative Application Examples 1 to 15
Similarly, the basis weight is 83±2g/m ² and 167±
A handmade paper weighing 3 g/m ² was obtained. In addition, the pH at the time of paper making is 7.5 without the addition of sulfate band, 6.0 with 0.5% sulfate band addition rate, 5.0 with 1.0% addition rate, and
The one with 2.5% addition was 4.5. After that, for the paper stock with a basis weight of 83±2g/ ^m2, the "specific burst strength" and "rupture length" were calculated as 167±2g/m2.
"Specific compressive strength" for paper stock with a basis weight of 3g/ ^m2
were measured in the same manner as Application Examples 1 to 12 and Comparative Application Examples 1 to 15. The results are summarized in Table 5. As is clear from the same table, it is known that the paper strength enhancing agent of the present invention has an excellent paper strength enhancing effect even when no sulfuric acid is added or when sulfuric acid is added at a low rate. Moreover, it is known that the paper strength enhancer of the present invention has a particularly remarkable effect compared to the comparative product.

【table】

[Table] Application examples 41 to 47 and comparative application examples 36 to 40 BKP L/N = 1/1 CSF is added to 382 ml of a 2.5% slurry of beaten pulp, and the pulp is 12%.
After adding talc, sulfuric acid band,
“New FO 100” [Deitsku Hercules Co., Ltd.]
rosin emulsion], as well as Example 8,
Each of the paper strength enhancers obtained in Comparative Examples 7, 9, and 12 to 14 was added to the pulp at 1.0%, 0.1%, and
0.4%, and then in the same manner as Application Examples 1 to 12 and Comparative Application Examples 1 to 15, the basis weight was 69 ± 2 g/
I obtained a handmade paper called ^m2 . “Specific bursting strength” (JIS
P-8112), "Stekicht size degree" (JIS P-
8112), "wax pick" (JIS P-8129) and "ash content" (JIS P-8128) were measured.
They are summarized in Table 6.

[Table] As is clear from the table above, although the paper strength enhancer of the present invention has a relatively high ash content in paper, it does not reduce paper strength and in addition improves surface strength. It also shows that.
Application examples 48 to 54 and comparative application examples 41 to 45 2.5 of beaten pulp (N-UKP, CSF = 417 ml)
% concentration slurry, 1.0% of sulfuric acid band and 0.1% of "Newfor 100" were added, and then Examples 8, 13 to 18 and Comparative Examples 7, 9, 12 to 14 were added separately.
After adding 0.4% of each paper strength enhancer obtained in , the same procedure as Application Examples 1 to 12 and Comparative Application Examples 1 to 15 was carried out, except that the pH at the time of paper making was changed to 5.8. The amount is 71±2g/ ^m2 and 143±3
Two types of handmade paper of g/m ² were obtained. "Specific bursting strength" for each paper stock based on the former weight
(JIS P-8112) and Steckigt sizing (JIS P-8122), and the measurement of "specific compressive strength" (JIS P-8126) for each paper stock of the latter weighing is summarized in Table 7. show.

【table】

[Table] As is clear from the results in the above table, it is known that the paper strength enhancer of the present invention has an excellent paper strength enhancing effect.
As is clear from the results in the above table, the paper strength enhancing agent of the present invention is known to have an excellent paper strength enhancing effect.

Claims (1)

[Scope of Claims] 1 (a) 0.1 to 20 mol% of water-soluble cationic monomers and/or salts thereof, (b) 0.1 to 15 mol% of α,β-unsaturated dicarboxylic acids and/or salts thereof, and ( c) A paper strength agent comprising a water-soluble copolymer obtained as an essential monomer component containing 99.8 to 65 mol% of acrylamide and/or methacrylamide.