JPH0757785B2 - Paper strengthening agent and method of using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a paper strength agent containing an anionic polyacrylamide-based water-soluble copolymer and a method for using the same.

[Conventional technology]

The supply of forest resources, which are the raw material for paper, is insufficient, and the use of waste paper as an alternative raw material is increasing, and various paper strengthening agents are used to compensate for the decrease in paper strength caused by the combined use of waste paper. There is. In addition, with the diversification of purposes, the need for various paper strength enhancers is increasing. Anionic polyacrylamide is a dry strength agent that has been used for a long time and is still in widespread use, and it is used to impart excellent paper strength by using it in combination with a sulfuric acid band and a cationic or amphoteric resin. There is.

Many conventional anionic polyacrylamide copolymers have
Hydrolysis of polyacrylamide (co) polymers, or copolymers of acrylamide with α, β-unsaturated monocarboxylic acids such as acrylic acid.

[Problems to be Solved by the Invention]

However, even though such a conventional anionic polyacrylamide copolymer has a paper-strengthening effect, it is not yet sufficient, and if its quality, performance and effect can be further enhanced, its usefulness is improved. Will increase even more.

INDUSTRIAL APPLICABILITY The present invention has an excellent dry paper-strengthening effect when used in combination with a sulfuric acid band or a cationic or amphoteric resin in the step of making paper, and is superior in anionic property to conventional anionic polyacrylamide copolymers. It is intended to provide a polyacrylamide copolymer.

[Means for Solving the Invention]

As a result of intensive studies on the effect of the anionic polyacrylamide-based paper-strengthening agent, the present inventors have included two or more α, β-unsaturated carboxylic acids or salts thereof as an anionic component, and have two or more α of these. , At least one of the β-unsaturated carboxylic acids or salts thereof is an α, β-unsaturated dicarboxylic acid or salt thereof. Anionic polyacrylamide copolymer is superior to conventional anionic polyacrylamide copolymers. The inventors have found that the dry paper strengthening effect is excellent and have reached the present invention.

It is not yet clear why such an effect can be obtained, but it is not possible to use a compound containing at least one α, β-unsaturated dicarboxylic acid.
By using more than one type of vinyl carboxylic acid, the distribution of anion sites in the polyacrylamide chain is changed, and the number of types that can ionically react with various cationic substances contained in the papermaking system is increased. It is considered that, under papermaking conditions, a more effective intermolecular bond can be produced, and as a result, a superior paper-strengthening effect can be exhibited. The α, β-unsaturated dicarboxylic acid according to the present invention is a polymerizable dibasic vinyl monomer having a double bond between the α-position and the β-position of one carboxyl group, such as maleic acid, Examples include fumaric acid, itaconic acid, citraconic acid and the like, or salts thereof such as alkali metal salts and ammonium salts with caustic soda, caustic potash and the like, but from the economical point of view, maleic acid, fumaric acid, itaconic acid or salts thereof are preferable. . As the anionic monomer copolymerized with acrylamide of the present invention, it is essential to include the above α, β-unsaturated dicarboxylic acid or a salt thereof, but as another anionic monomer to be combined, α, β -Unsaturated monocarboxylic acids or their salts, or other α, β-unsaturated dicarboxylic acids or their salts are used. Examples of the α, β-unsaturated monocarboxylic acid include acrylic acid and methacrylic acid, and examples of the salts thereof include alkali metal salts and ammonium salts of these α, β-unsaturated monocarboxylic acids with caustic soda, caustic potash and the like. To be done.

Regardless of the combination of these α, β-unsaturated dicarboxylic acid and other anionic monomer, the anionic water-soluble copolymer composed of these anionic components and acrylamide is treated with one anionic monomer. Paper strength superior to an anionic water-soluble copolymer composed of acrylamide or an anionic water-soluble copolymer composed of acrylamide and two or more anionic monomers not containing α, β-unsaturated dicarboxylic acid The effect can be expressed. The amount of the α, β-unsaturated carboxylic acid or salt thereof used in the anionic water-soluble copolymer of the present invention is 0.1 to 2.0 meq / g · solid as the carboxyl group content (in the case of obtaining the anionic water-soluble copolymer, The number of milliequivalents per 1 g of solid content of the aqueous solution, the same applies hereinafter), preferably 0.5 to 1.2 meq / g.solid.

The viscosity of the anionic polyacrylamide copolymer obtained by the present invention is 300 to 100,000 cps (25
℃, viscosity by Brookfield viscometer)
In particular, the water-soluble copolymer having the above-mentioned viscosity of 800 to 20,000 cps is preferable as the paper strengthening agent.

As a copolymer component, vinyl monomers copolymerizable with them, such as methacrylamide, acrylonitrile, styrene, methyl methacrylate, vinyl acetate, etc. may be used to the extent that water solubility is not impaired.

The copolymerization reaction of acrylamide and anionic monomer of the anionic polyacrylamide copolymer of the present invention can be carried out by various conventionally known methods. For example, by using a water-soluble catalyst such as sodium persulfate, potassium persulfate, ammonium persulfate, or hydrogen peroxide as a radical polymerization initiator in an amount of 0.01 to 5% by weight with respect to all monomers, an aqueous solution polymerization is performed. You can Further, redox polymerization can be carried out using a reducing agent such as dimethylamine, sodium thiosulfate, sodium hydrogen sulfite, sodium formaldehyde sulfoxylate. At this time, the monomer concentration in the aqueous medium is 5 to 30% by weight, and the temperature is 35 to 95 ° C.
Obtained by stirring for ~ 10 hours. Further, an allyl compound such as allyl alcohol, sodium allyl sulfonate, and allyl amine and a known chain transfer agent such as isopropyl alcohol and sodium hypophosphite are appropriately used to synthesize an anionic polyacrylamide copolymer having a target molecular weight. You can do it. In addition, as another synthetic method of the present invention, an acrylic acid type compound is prepared by producing a copolymer of acrylamide containing α, β-unsaturated dicarboxylic acid and partially hydrolyzing the amide group of the obtained copolymer. Of course, there is no problem even if the monocarboxylic acid group is introduced. The anionic polyacrylamide copolymer of the present invention may be used according to a conventionally known method. That is, 0.05 to 4% by weight of solid content of the anionic polyacrylamide copolymer of the present invention is added to an aqueous dispersion of pulp, and a sulfuric acid band or a cationic resin or an amphoteric resin is used in combination. And perform papermaking. It should be noted that any known sizing agent, paper-strengthening agent, water-based improver, etc. may be used in combination before papermaking.

〔The invention's effect〕

According to the present invention, at least one of the two or more α, β-unsaturated carboxylic acids or salts thereof is an anionic polyacrylamide water-soluble aqueous solution obtained by using the α, β-unsaturated dicarboxylic acid or salts thereof. Since it is possible to provide a paper strength enhancer containing a sex copolymer, the dry paper strength increasing effect can be enhanced by using the paper strength enhancer when making paper.

In particular, when the paper strength enhancer containing the anionic polyacrylamide-based water-soluble copolymer is used in combination with any of the sulfuric acid band, the cationic resin and the amphoteric resin, the dry paper strength increasing effect can be further enhanced.

Further, when the paper-making agent containing the anionic polyacrylamide-based water-soluble copolymer is used for papermaking, drainage is improved.

Next, examples and application examples of the present invention will be described.

In the following,% is all% by weight unless otherwise specified.

Example 1 617.6 g of water, 253.9 g of 50% aqueous acrylamide solution, 4.84 g of itaconic acid, 3.35 g of 80% aqueous acrylic acid solution were placed in a one-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube. Charge 15.4 g of 2% sodium hypophosphite aqueous solution, add 8.17 g of 15% sodium hydroxide aqueous solution to pH 4.0.
After adjusting to, nitrogen gas was introduced to remove oxygen in the reaction system.

Then, raise the temperature to 60 ° C. and add 5% ammonium persulfate aqueous solution.
4.25 g was added to start the polymerization reaction. After that, the mixture was kept warm at 75 ° C, 1.5 hours after the start of polymerization, 2.11 g of 5% ammonium persulfate aqueous solution was added, and further kept at 75 ° C for 1.5 hours to complete the polymerization, non-volatile content 15.4%, Brookfield viscosity at 25 ° C A stable copolymer aqueous solution having a pH of 7,800 cps and a pH of 4.7 was obtained. This is designated as paper strengthening agent A.

Examples 2 to 12 The same polymerization reaction as in Example 1 was carried out by mixing the constituent monomer components shown in Table 1 to obtain aqueous copolymer solutions. These are designated as paper strengthening agents B to P. The amount of the chain transfer agent was appropriately changed so that the viscosities of the respective copolymers were about the same.

Comparative Examples 1 to 12 The same polymerization reaction as in Example 1 was carried out by blending the constituent monomer components shown in Table 2, and only one kind of copolymer aqueous solution or α, β-unsaturated dicarboxylic acid was used as the anion component. A combination of two types of anionic copolymer aqueous solution containing no water was obtained. These are designated as paper strengthening agents a to p. Also in this case, the amount of the chain transfer agent was appropriately changed.

The physical properties of the copolymers obtained in Examples and Comparative Examples are
Table 2 and Table 2 show.

In the table, the carboxyl group content (meq / g · solid) was calculated as follows.

Of the total amount of the obtained aqueous solution of the copolymer, the nonvolatile content is defined as the solid content, and the total number of equivalents of the acid used is multiplied by 1000 with respect to 1 g of the solid content.

For example, for Example 1, the total amount of the aqueous copolymer solution obtained was 909.62 g calculated from the raw materials used, so the amount corresponding to the nonvolatile content of 15.4% was 140.081 g, while the equivalent amount of itaconic acid was used. The number is (4.84g / 130.
1 (molecular weight)] x 2 (1 molecule is 2 equivalents) = 0.0744, and the equivalent number of the amount of acrylic acid used is 2.68 (80% acrylic acid 3.35g is 2.68g with acrylic acid only) 2.1 (molecular weight) Since x1 (1 equivalent of one molecule) = 0.0371, [(0.0744 + 0.0371) / 140.081] x 1000 ≈ 0.80.

The abbreviations of monomers in Tables 1 and 2 are as follows.

IA ... Itaconic acid MA ... Maleic acid AA ... Acrylic acid MAA ... Methacrylic acid AAm ... Acrylamide Application Example 1 Purpose of examining the effect of the anionic polyacrylamide copolymer of the present invention in a papermaking system using a small amount of sulfuric acid band and amphoteric resin Then, to the 2.5% aqueous dispersion of pulp (NUKP: CSF = 409 ml), 0.3% each of the paper strengthening agents AF obtained in the example and the paper strengthening agents af obtained in the comparative example were added. Then, 0.5% of a sulfuric acid band and 0.1% of RETEN HM-133 (manic modified amphoteric polyacrylamide resin manufactured by Dick Hercules Co., Ltd.) were sequentially added. The addition rate is the weight ratio of the solid content to the dry weight of pulp. This pulp slurry was diluted to 0.25%, paper was made with a Noble and Wood hand-made machine (pH 6.0 at paper making), then dried with a drum dryer at 110 ° C for 1.5 minutes, and weighed 82
Two types of handmade paper were obtained, ± 2 g / m ² and 168 ± 3 g / m ² , respectively. Also, using this 0.25% pulp slurry Was measured and the water content was examined. The resulting stock is 20 ℃, 65% R
After conditioning the humidity for 24 hours under the condition of H, `` Specific burst strength '' according to JIS P-8112 for the former basis weight paper material and `` Specific burst strength '' according to JIS P-8126 for the latter basis weight paper amount. Specific compression strength "was measured. The results are shown in Table 3. From the table, it can be seen that the anionic polyacrylamide copolymer of the present invention has an excellent paper-strengthening effect and is also excellent in water-based property.

Note) Using a device similar to "Dynamic Drainage Jar" described on page 46 of DDT Tappi Journal Vol. 56, No. 10 (1973), pour 800 ml of pulp slurry into a jar of about 7.5 cm in diameter, While stirring at 800 rpm, open the lower cock to 100 m
It measures the time it takes for the amount of liquid to reach a certain amount by passing through the mesh of esh, and can be used for water-based evaluation. Here, the time until the liquid volume reached 250 ml was measured.

Application Example 2 Paper strength obtained in Examples and Comparative Examples for the purpose of observing the effect of a polyacrylamide copolymer having a larger amount of anion than the anionic polyacrylamide copolymer illustrated in Application Example 1. Aqueous (DDT), specific burst strength and specific compressive strength were measured by the same operations as in Application Example 1 using the enhancers G to L and g to l. The results are shown in Table 4. Also in this table, the anionic polyacrylamide copolymer of the present invention shows an excellent paper-strengthening effect.

Application Example 3 An effect comparison between the anionic polyacrylamide copolymers of the present invention having various molecular weights and the anionic polyacrylamide copolymers exemplified in Comparative Examples is shown. NUKP (CS as pulp
The same operation as in Application Example 1 was performed using F = 376 ml), and the aqueous (DDT), specific burst strength, and specific compressive strength were measured. The results are shown in Table 5. The anionic polyacrylamide copolymers of the present invention show excellent performance over a wide range of molecular weights.

Application Example 4 The effect of using the anionic polyallylamide copolymer of the present invention and a polyamide / epichlorohydrin condensate which is a cationic resin in combination was confirmed. Pulp (NUKP: C
To the 2.5% aqueous dispersion of SF = 375 ml, 0.3% of the paper strengthening agent obtained in the examples and comparative examples was added, and then the sulfuric acid band was 1.0% and Kaymene 557H (Dick Hercules Co., Ltd. polyamide. Epichlorohydrin condensate) to 0.
1% was added sequentially. The addition rate is the weight ratio of the solid content to the dry weight of pulp. This pulp slurry was diluted to 0.25%, DDT was measured using part of it, and the other part was used to make paper with a Noble and Wood handmade machine (pH 5.0 when making paper), and a drum dryer. It was dried at 110 ° C for 1.5 minutes to obtain handmade papers having a basis weight of 85 ± 2 g / m ² and 167 ± 3 g / m ² . Using this paper material, the specific burst strength and the specific compressive strength were measured in the same manner as in Application Example 1. The results are shown in Table 6. The table also shows that the anionic polyacrylamide copolymer of the present invention has an excellent combined effect when it is used together with a polyamide / epichlorohydrin condensate as a cation resin.

Application Example 5 An example of papermaking using only a sulfuric acid band for the purpose of examining the effect of the anionic polyacrylamide copolymer of the present invention in a single system is shown. To a 2.5% aqueous dispersion of pulp (NUKP: CSF = 370 ml) was added 0.4% anionic polyarylamide copolymer followed by 2.0% sulfuric acid band. The addition rate is the weight ratio of the solid content to the dry weight of pulp. This pulp slurry was diluted to 0.25%, DDT was measured, paper was made with a Noble and Wood handmade machine (pH 4.5 at paper making), and dried with a drum dryer at 110 ° C for 1.5 minutes. , Hand paper having a basis weight of 81 ± 2 g / m ² and 164 ± 3 g / m ² was obtained. Using this paper material, the specific burst strength and the specific compression strength were measured in the same manner as in Application Example 1. The results are shown in Table 7. From this table,
The anionic polyacrylamide copolymer of the present invention exhibits excellent performance even under the conventional papermaking conditions using only the sulfuric acid band.

Application Example 6 Although the use of the anionic strength enhancer is a special example, the effect of the anionic polyacrylamide copolymer when the polyamide-epichlorohydrin condensate is used together without using the sulfuric acid band is shown. Pulp (LBKP: C
SF = 335 ml) to 2.5% aqueous dispersion, 0.25% or 0.5% of anionic polyacrylamide copolymer was added, followed by 0.5% of Kamen 557H (Dick Hercules Co., Ltd., polyamide epichlorohydrin condensate). HAKON W (manufactured by Dick Hercules Co., Ltd., alkyl ketene dimer type sizing agent) was sequentially added at 0.5%. The addition rate is the weight ratio of the solid content to the dry weight of pulp. This pulp slurry is diluted to 0.25% and noble and
Paper is made with a handmade machine made of wood (pH 7.0 at paper making), then dried with a drum dryer at 100 ° C for 1.5 minutes, and the basis weight is 9
8 ± 2 g / m ² of handmade paper was obtained. The resulting stock is 20 ℃, 65% R
After conditioning the humidity for 24 hours under the condition of H, "specific burst strength" according to JIS P-8112 and "water absorption test (cobb test)" according to JIS P-8140 were measured. The results are shown in Table 8. The anionic polyacrylamide copolymer of the present invention exhibits not only an excellent paper strength-enhancing effect but also an excellent size retention effect.

Claims (13)

[Claims] 1. An anionic polyacrylamide-based water-soluble copolymer having repeating units corresponding to at least acrylamide and an anionic monomer having a carboxyl group, respectively, the anionic monomer having the carboxyl group. Is two or more α, β-unsaturated carboxylic acids or salts thereof, and at least one of the two or more α, β-unsaturated carboxylic acids or salts thereof is α, β-
It is an unsaturated dicarboxylic acid or a salt thereof, and the carboxyl group content is 0.1 to 0.1 g per 1 g of the solid content of the aqueous solution when the anionic polyacrylamide-based water-soluble copolymer is obtained.
Anionic polyacrylamide-based water-soluble copolymer having 2.0 meq and a viscosity of a 10% aqueous solution of the anionic polyacrylamide-based water-soluble copolymer at 25 ° C. measured by Brookfield viscometer is 300 to 100,000 centipoise. A paper strength enhancer comprising: 2. The repeating unit corresponding to acrylamide is 92 mol% or more and 97 mol% or less of all repeating units of the anionic polyacrylamide water-soluble copolymer.
The paper strength enhancer described. 3. The paper-strengthening agent according to claim 1, wherein the carboxyl group content is 0.5 to 1.2 milliequivalents per 1 g of the solid content of the aqueous solution for obtaining the anionic polyacrylamide-based water-soluble copolymer. 4. The paper strength according to claim 1, wherein the viscosity of a 10% aqueous solution of an anionic polyacrylamide water-soluble copolymer at 25 ° C. measured by a Brookfield viscometer is 800 to 20,000 centipoise. Enhancer. 5. The paper strength according to claim 1, wherein the two or more α, β-unsaturated carboxylic acids are maleic acid, itaconic acid, or maleic acid or itaconic acid and acrylic acid. Enhancer. 6. A paper strength is enhanced by using any one of the group consisting of a sulfuric acid band, a cationic resin and an amphoteric resin together with a paper strength enhancer containing an anionic polyacrylamide water-soluble copolymer to enhance paper strength. A method of using a paper strengthening agent,
The anionic polyacrylamide-based water-soluble copolymer is an anionic polyacrylamide-based water-soluble copolymer having repeating units corresponding to at least acrylamide and an anionic monomer having a carboxyl group, respectively. 2 having an anionic monomer
One or more α, β-unsaturated carboxylic acids or salts thereof, and at least one of the two or more α, β-unsaturated carboxylic acids or salts thereof is an α, β-unsaturated dicarboxylic acid or The salt, and the carboxyl group content is 0.1 to 2.0 milliequivalents per 1 g of the solid content of the aqueous solution when the anionic polyacrylamide-based water-soluble copolymer is obtained, and the anionic polyacrylamide-based water-soluble copolymer is used. A method of using a paper strengthening agent, characterized in that the viscosity of a 10% aqueous solution of a polymer at 25 ° C. measured by a Brookfield viscometer is 300 to 100,000 centipoise. 7. The method of using a paper strengthening agent according to claim 6, wherein any one of the group consisting of a sulfuric acid band, a cationic resin and an amphoteric resin is a sulfuric acid band and a polyamide-epichlorohydrin condensate which is a cationic resin. 8. A sulfuric acid band, and any one of the group consisting of a cationic resin and an amphoteric resin is a sulfuric acid band and a mannic modified polyacrylamide resin which is an amphoteric resin.
A method of using the paper strengthening agent described. 9. The method of using a paper strength enhancer according to claim 6, wherein one of the group consisting of a sulfuric acid band, a cationic resin and an amphoteric resin is a polyamide-epichlorohydrin condensate which is a cationic resin. 10. The paper strength according to claim 6, wherein the repeating unit corresponding to acrylamide is 92 mol% or more and 97 mol% or less of all the repeating units of the anionic polyacrylamide-based water-soluble copolymer. How to use the enhancer. 11. The method according to claim 6, wherein the carboxyl group content is 0.5 to 1.2 milliequivalents per 1 g of the solid content of the aqueous solution when the anionic polyacrylamide water-soluble copolymer is obtained.
11. The method of using the paper strengthening agent according to any one of 10. 12. The paper strength according to claim 6, wherein the viscosity of a 10% aqueous solution of an anionic polyacrylamide water-soluble copolymer at 25 ° C. measured by a Brookfield viscometer is 800 to 20,000 centipoise. How to use the enhancer. 13. The paper strength according to claim 6, wherein the two or more α, β-unsaturated carboxylic acids are maleic acid, itaconic acid, or maleic acid or itaconic acid and acrylic acid. How to use the enhancer.