JP2912405B2 - Strength enhancer in paper layer - Google Patents

Description

The present invention relates to a papermaking additive. More specifically, the present invention relates to an amphoteric polyacrylamide-based paper strength agent that exhibits an effect of enhancing the paper strength inside the paper layer.

[Conventional technology]

In recent years, the use of inferior pulp wood and waste paper has tended to increase due to the effective use of pulp, a forest resource.In the papermaking process, white water has been completely closed due to issues such as wastewater regulations. Is coming. For this reason, a decrease in paper quality is inevitable, and in particular, overcoming a decrease in paper strength is an important issue. Among them, depending on the use of paper, various problems due to a decrease in strength in the paper layer (meaning strength in a direction perpendicular to the plane of the paper and also referred to as Z-axis strength) may be a great hindrance to the use of paper. Many. Specifically, in the paperboard field, for example, a post-process poor due to low interlayer strength, which occurs in coated white balls, etc., and blistering during off-wheel printing due to low internal strength of coated paper in the paper field, This leads to the occurrence of a decrease in surface strength and the like.

By the way, additives such as polyacrylamide-based polymers, modified starches, and epoxypolyamide-based polymers have been widely used as additives for paper strength in order to solve such problems. Are known. Among them, a cationic or amphoteric polyacrylamide-based polymer such as a cationic or amphoteric polyacrylamide modified by a Mannich reaction or a Hoffman reaction, or a polyacrylamide copolymerized with a cationic monomer is used alone or as a starch or an anion. When used in combination with polyacrylamide or the like, it is often used as an additive to improve the strength of each paper and the strength in the paper layer.

Conventionally known cationic or amphoteric acrylamide polymers include 1) those produced by the Mannich reaction, for example, a polymer of acrylamide alone or an anionic polyacrylamide copolymer represented by acrylic acid-acrylamide with formaldehyde. A polymer obtained by performing a Mannich reaction using an alkylamine represented by dimethylamine, 2) a polymer of acrylamide alone or a polymer obtained by subjecting an acrylamide and acrylonitrile copolymer to a Hoffman decomposition reaction, or 3) A vinyl monomer having a tertiary amino group such as dimethylaminopropylacrylamide or acrylamidopropyltrimethylammonium chloride or a quaternary ammonium base, and an unsaturated monomer such as acrylic acid. There are amphoteric acrylamide copolymers obtained by copolymerizing rubonic acid and acrylamide, etc., which are indispensable as additives to improve the strength in the paper layer, but their effects are not yet sufficient, and the further performance of these polymers It is very important to improve.

[Problems to be solved by the invention]

That is, an object of the present invention is to provide a paper layer strength agent which exhibits an unprecedented effect in order to improve the paper layer strength and solve various problems such as delamination phenomenon and blister generation in each use of paper.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to develop an additive in which the above-mentioned cationic or amphoteric acrylamide copolymer has not been achieved conventionally and has a greatly improved effect of improving the strength in the paper layer. Was achieved.

That is, (a) a vinyl monomer having a tertiary amino group and / or a salt of an organic or inorganic acid thereof, or a reaction between the vinyl monomer having a tertiary amino group and a quaternizing agent. Quaternary ammonium salts 0.5-70m
(b) 0.5 to 20 mol% of α, β-unsaturated carboxylic acid and / or a salt thereof and (c) 10 to 99 mol% of acrylamide and / or methacrylamide as essential constituent monomer components. A copolymer (A) and a cationic acrylamide-based polymer (B) (provided that a polycation containing an N atom in the polymer main chain, a polycation that is a Mannich compound of polyacrylamide having a cation equivalent of 7.5 meq / g or more, And a polyacrylamide having a cation equivalent of 8 meq / g or more (excluding polycations, which are Hoffman reactants).

[Specific conditions for carrying out the invention]

 The present invention will be described in detail.

In the present invention, the vinyl monomer having a tertiary amino group contained in (a) is a cationic vinyl monomer copolymerizable with (meth) acrylamide. For example, dimethylaminoethyl (meth) acrylate, (meth) acrylic acid ester derivatives represented by diethylaminoethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylamide or diethylaminopropyl (meth) acrylamide (meth) ) Acrylamide derivatives and the like.

The organic or inorganic acid salts of a vinyl monomer having a tertiary amino group means salts of inorganic acids such as sulfuric acid and hydrochloric acid, and salts of organic acids such as acetic acid and phosphoric acid.

The quaternary ammonium salts obtained by the reaction of the tertiary amino group-containing vinyl monomer with the quaternizing agent include the tertiary amino group-containing vinyl monomer, methyl chloride, dimethyl sulfate, Examples thereof include vinyl monomers having a quaternary ammonium salt obtained by a reaction with a quaternizing agent such as epichlorohydrin or benzyl chloride.

In the present invention, a tertiary amino group-containing vinyl monomer or a salt of an organic or inorganic acid thereof may be used in combination with a quaternary ammonium salt obtained by reaction with a quaternizing agent. Absent. The mixing ratio of these is not particularly limited.

The amount of these cationic monomers is usually 0.5 to 70 mol%, preferably 2 to 50 mol%.

The (b) α, β-unsaturated carboxylic acid or an alkali metal salt or ammonium salt thereof of the present invention is:
Vinyl monomers having anionic properties, such as maleic acid, fumaric acid, itaconic acid, (meth) acrylic acid,
Examples thereof include unsaturated carboxylic acids such as crotonic acid and citraconic acid, alkali metal salts such as sodium salt and potassium salt thereof, and ammonium salts.

The amount of these monomers used is 0.5-20 mol%,
Preferably it is 2 to 20 mol%.

(Meth) acrylamide used in (C) of the present invention is:
It is sufficient that they are commercially available in the form of a powder or an aqueous solution and are used industrially.

Further, as a method for obtaining the copolymer (A) of the present invention,
A commonly known method used for polymerization of this type of water-soluble vinyl monomer is used.

For example, radical polymerization is preferable as the polymerization method. The monomer concentration is 2 to 30% by weight, preferably 5 to 30% by weight. The polymerization initiator is not particularly limited as long as it is water-soluble, and is usually used after being dissolved in an aqueous monomer solution. Specifically, peroxides such as hydrogen peroxide and benzoyl peroxide, persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, bromates such as sodium bromate and potassium bromate, and perboric acid Sodium, potassium perborate, perborate such as ammonium perborate, sodium percarbonate, potassium percarbonate, percarbonate such as ammonium percarbonate, sodium perphosphate, potassium perphosphate, ammonium perphosphate Superphosphate, te
rt.-butyl peroxide and the like. In this case, it can be used alone, but can also be used as a redox polymerizer in combination with a reducing agent. As the reducing agent, for example, salts of lower ionization such as sulfites, bisulfites, iron, copper, and cobalt; organic amines such as N, N, N ', N'-tetramethylethylenediamine; and aldose and ketose And the like.

As the azo compound, 2,2'-azobis-4-
Amidinopropane hydrochloride, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleic acid and salts thereof can be used. Furthermore,
Two or more of the above-mentioned polymerization initiators can be used in combination.

The polymerization temperature is lower in the case of a single polymerization initiator and generally lower.
The temperature is 30 to 90 ° C., which is lower in the case of the redox polymerization initiator, and is generally 5 to 50 ° C. Further, it is not necessary to keep the same temperature during the polymerization, and the temperature may be changed as appropriate with the progress of the polymerization. Generally, the temperature is raised by polymerization heat generated as the polymerization proceeds. The atmosphere in the polymerization vessel at that time is not particularly limited, but it is preferable to replace the atmosphere with an inert gas such as a nitrogen gas in order to promptly carry out the polymerization. Although the polymerization time is not particularly limited, it is generally 1 to
20 hours.

In the present invention, the polymer (B) is a polyacrylamide-based polymer exhibiting cationicity (however, a polycation containing an N atom in the polymer main chain, a polycation which is a Mannich product of polyacrylamide having a cation equivalent of 7.5 meq / g or more) ,
And polycations having a cation equivalent of 8 meq / g or more (excluding polycations which are Hoffman reactants). For example, there is a polyacrylamide-based polymer in which a polymer containing (meth) acrylamide as a polymerization component is cationized by a Mannich reaction or a Hoffman decomposition reaction.

In this case, an anionic vinyl monomer may be used as a polymerization component of the polymer before modification, and specifically, an α, β-unsaturated carboxylic acid or an alkali metal salt or an ammonium salt thereof, for example, Maleic acid, fumaric acid,
Unsaturated carboxylic acids such as itaconic acid, (meth) acrylic acid, crotonic acid or citraconic acid, or alkali metal salts such as sodium or potassium salts or ammonium salts thereof.

The content ratio of these anionic vinyl monomers to the acrylamide polymer (B) is determined at the pH when the paper layer strength agent of the present invention is used.
Is not particularly limited as long as the cationicity of the compound is not impaired.

The mixing ratio of (A) and (B) is arbitrary, but considering the mixing effect, it is 95: 5 to 5:95, preferably 80:20 to 20:
80.

The method of mixing (A) and (B) may be any method such as a mixer or a mixer, and the mixing may be performed immediately after the completion of polymerization of each of (A) and (B), or immediately before or during use. Is optional.

The concentration of the mixture of (A) and (B) is basically (A)
It is determined depending on the concentration of each of the polymers (A) and (B), but may be diluted as necessary before mixing, or may be further diluted with water after mixing.

The pH of the mixture of (A) and (B) is not particularly limited, but when (B) is a Mannich-reacted polyacrylamide-based polymer, the pH is preferably in the acidic region of 4 or less or in the alkaline region of 8 or more. preferable. (B)
Is a Hoffman decomposition reaction, it is preferable that the acidic region having a pH of 5 or lower be an alkaline region having a pH of 8 or higher. At this time, when mixing in an alkaline region having a pH of 8 or more, it is more desirable to add immediately after mixing.

The in-paper layer strength improver produced by the method of the present invention is used in a pulp papermaking process, and its addition brings a great effect. At this time, the paper layer strength improver of the present invention can be used alone, but when combined with a sulfate band, an anionic resin or the like, the effect may be further increased. The water-soluble anionic resin used at this time is
It is a water-soluble resin containing an anionic substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group or a salt thereof, for example, an anionic acrylamide resin, an anionic polyvinyl alcohol resin, carboxymethyl cellulose, carboxymethyl Modified starch, sodium alginate and the like.

The combination ratio and addition amount of these agents can be arbitrarily selected.

The place of addition can be anywhere before the wet sheet is formed, the drug is sufficiently diluted and mixed with the pulp slurry,
And it is better to add at a place close to the papermaking wire part.

Paper manufactured by the above method has excellent Z-axis strength. Therefore, by applying the present invention to paper requiring paper strength within the paper layer, it becomes possible to manufacture paper having excellent Z-axis strength. The reason for this is not clear, but by mixing two types of copolymers, each having a different cationized form, the polymer is fixed to the pulp in an ideal form in the papermaking slurry, so that the It is considered that the stock is equalized, and as a result, the Z-axis strength is improved.

[Examples] Next, the present invention will be specifically described by way of examples with reference to production examples and application examples, but the present invention is not necessarily limited to the following examples. All percentages are by weight unless otherwise specified.

The in-paper layer strength improver of the present invention can be obtained by mixing and adjusting two kinds of polymers. First, a method for adjusting each polymer before mixing will be described.

Production Example 1 of Polymer (A) 106.5 g of 40% acrylamide, 4.71 g of dimethylaminoethyl methacrylate, and 5.04 of acrylic acid were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube.
g, acrylonitrile 15.9 g and water 257.9 g, 10
The pH was adjusted to 4.5 with an aqueous solution of sulfuric acid. Thereafter, the internal temperature was raised to 45 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. After that, the temperature was kept at 85 ° C, and water was added 3 hours after the start of polymerization,
Adjustment was performed to complete the polymerization reaction. Non-volatile content 15.2%, Brookfield viscosity at 25 ° C 5250 cps, pH
A stable amphoteric copolymer aqueous solution A-1 of 4.3 was obtained.

Production Example 2 of Polymer (A) 166.9 g of 40% acrylamide, 14.2 g of 80% methacryloyloxyethyldimethylbenzylammonium chloride, 2.6 g of itaconic acid were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube. g and 277.6 g of water were charged and adjusted to pH 4.5 with a 20% aqueous NaOH solution. Thereafter, the internal temperature was raised to 45 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., and water was added 3 hours after the start of the polymerization, pH was adjusted, and the polymerization reaction was completed. When the nonvolatile content was 15.3%, Brookfield viscosity at 25 ° C.
A stable amphoteric copolymer aqueous solution A-2 of 5900 cps and pH 4.4 was obtained.

Polymer (A) Production Example 3 In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube, 150.9 g of 40% acrylamide, 15.6 g of dimethylaminopropylacrylamide, and 3.6 parts of acrylic acid
g and 284.5 g of water, and adjusted to pH 4.5 with a 10% aqueous sulfuric acid solution. After that, while blowing nitrogen gas,
The temperature was raised to ° C. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., 3 hours after the start of the polymerization, water was added, the pH was adjusted, and the polymerization reaction was completed. When the nonvolatile content was 15.1%, the Brookfield viscosity at 25 ° C. was 6230 cps, and the pH was 4.4. An amphoteric copolymer aqueous solution A-3 was obtained.

Polymer (B) Production Example 1 A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was charged with 165.1 g of 40% acrylamide, 5.04 g of acrylic acid, and 236.0 g of water, and a 20% aqueous NaOH solution was added. Was adjusted to pH 4.0. Thereafter, the internal temperature was raised to 45 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., and water was added three hours after the initiation of the polymerization to complete the polymerization reaction.

After cooling the aqueous polymer solution to 40 ° C., 39.6 g of a 50% aqueous dimethylamine solution and 32.4 g of a 37% aqueous formaldehyde solution were added thereto while stirring, and the mixture was maintained at 40 ° C. for 3 hours. Was completed, nonvolatile content 15.3%, Brookfield viscosity at 25 ° C 4500cps, pH1
A Mannich modified cationic polyacrylamide polymer aqueous solution B-1 was obtained.

Production Example 2 of Polymer (B) 165.1 g of 40% acrylamide, 5.04 g of acrylic acid and 236.0 g of water were charged into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube, and a 20% aqueous NaOH solution was added. Was adjusted to pH 4.0. Thereafter, the internal temperature was raised to 45 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., and water was added three hours after the start of the polymerization to complete the polymerization reaction. Then, after cooling the polymer aqueous solution to 20 ° C., while stirring, a 12.5% sodium hypochlorite solution 125.8%
g, 53.3 g of a 30% NaOH aqueous solution was added, and the mixture was maintained at 30 ° C. for 30 minutes. Water and sodium sulfite were added to complete the reaction. The active ingredient was 10.0%, Brookfield viscosity at 25 ° C. 550 cps, pH 11 Thus, an aqueous solution B-2 of a cationic polyacrylamide polymer subjected to a Hoffman decomposition reaction was obtained.

Production Example 1 (Strength improver in paper layer) Polymer (A) Polymer (A) obtained from Production Examples 1 to 3
And the polymer (B) obtained from Production Examples 1 and 2 were mixed at a weight ratio of 5: 5 to obtain a polymer mixture (C). The pH of the polymer mixture (C) was adjusted, and the obtained paper layer strength improvers C-1 to C-6 are shown in Table 1.

Comparative Production Example 1 (Strength improver in paper layer) Hoplon 3150B (hereinafter abbreviated as H-3150B) which is an anionic acrylamide polymer instead of polymer (A)
And H-3150B and polymers B-1 and B-2 in a weight ratio of 5: 5.
Thus, a polymer mixture (B) was obtained. The pH of the polymer mixture (D) was adjusted, and the obtained comparative products D-1 and D-2 were shown in Table 1 together with the strength improver in the paper layer.

Application Example 1 A commercially available rosin emulsion sizing agent is added to a pulp slurry having a beating degree (Canadian Standard Freeness, hereinafter referred to as CSF) of 350% and a pulp slurry having a concentration of 1.0%, and 0.15% based on dry weight of pulp. And stir for 2 minutes. Next, 1.0% of aluminum sulfate was added on a dry weight basis, and the mixture was further stirred for 1 minute.
Addition and stirring continued for an additional minute. Thereafter, the pulp slurry was used to make paper with a TAPPI square sheet machine.

In addition, paper made without adding the strength improver in the paper layer was used as blank paper.

The wet sheet is made with a drum dryer.
Drying was performed at 0 ° C. for 3 minutes to obtain a handmade paper having a basis weight of 100 g / m ² .

"Z-axis strength" was measured using an internal bond tester manufactured by Kumagai Riki Kogyo.

Table 2 shows the results obtained when the paper layer strength improvers C-1 to C-6 were used.

Comparative application example 1 Comparative product D in place of paper layer strength improvers C-1 to C-6
The same operation as in Application Example 1 was performed except that -1 and -2 were used. The results are shown in Table 3.

Comparative Application Example 2 In place of the paper layer strength improvers C-1 to C-6, the polymers A and B used to adjust the respective paper layer strength improvers are used in combination (addition interval: 2 minutes) or alone. In the case of adding and using together, the same operation as in Application Example 1 was performed, except that the added amount was 0.2%. The results are shown in Tables 4 and 5.

Application Example 2 Commercially available rosin emulsion sizing agent is added to a pulp slurry having a beating degree (Canadian Standard Freeness, hereinafter referred to as CSF) of 350% and a pulp slurry having a concentration of 1.0%, and 0.15% based on dry weight of pulp. And stir for 2 minutes. Next, 1.0% of aluminum sulfate was added on a dry weight basis, and the mixture was further stirred for 1 minute.
Addition and stirring continued for an additional minute. Thereafter, a half of the obtained pulp slurry was used to make paper with a TAPPI square sheet machine to obtain a wet sheet (1). Next, when the remaining pulp slurry was used to make paper, the wet sheet (1) was combined.

The wet sheet is made with a drum dryer.
Drying was performed at 0 ° C. for 3 minutes to obtain a hand-made laminated paper having a basis weight of 100 g / m ² .

In addition, paper made in the same manner without adding the strength improving agent in the paper layer was used as blank paper.

"Interlayer strength" was measured using an internal bond tester manufactured by Kumagai Riki Kogyo.

Table 6 shows the results obtained when the in-paper strength improvers C-1 to C-6 were used.

Comparative application example 3 Comparative product D in place of the paper layer strength improvers C-1 to C-6
The same operation as in Application Example 1 was performed except that -1 and -2 were used. The results are shown in Table 7.

Comparative Application Example 4 Instead of the paper layer strength improvers C-1 to C-6, the polymers A and B used to adjust the respective paper layer strength improvers were used in combination (addition interval: 2 minutes) or alone. And add
When used together, the same operation as in Application Example 1 was performed, except that the amount of each additive was 0.2%. The results are shown in Tables 8 and 9.

[Effects of the Invention] As shown in Tables 2 to 9, in papermaking, the amphoteric copolymer produced under the conditions within the scope of the present invention has a Z-axis strength,
It is clear that the strength of the paper layer, which is indicated by the interlayer strength, is excellent. Therefore, it can be said that this patent is significant as a method for producing a paper layer strength improver.

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Claims (1)

(57) [Claims] (A) vinyl monomers having a tertiary amino group and / or salts of organic or inorganic acids thereof,
Alternatively, quaternary ammonium salts obtained by reacting the vinyl monomer having a tertiary amino group with a quaternizing agent.
5 to 70 mol%, (b) 0.5 to 20 mol% of α, β-unsaturated carboxylic acid and / or salts thereof, and (c) 10 to 99 mol% of acrylamide and / or methacrylamide as essential constituent monomer components. A water-soluble copolymer (A) and a cationic acrylamide-based polymer (B) (provided that a polycation containing an N atom in the polymer main chain and a Mannich compound of polyacrylamide having a cation equivalent of 7.5 meq / g or more) A cation and a polyacrylamide having a cation equivalent of at least 8 meq / g, excluding polycation, which is a Hoffman reaction product thereof).