JP2611824B2 - Papermaking additives - Google Patents

Description

The present invention relates to a papermaking additive containing a polyacrylamide-based water-soluble copolymer mainly composed of acrylamide and / or methacrylamide, which is affected by pH fluctuation during papermaking. The present invention relates to a papermaking additive capable of exhibiting an excellent paper strength enhancing effect in a wide pH range.

(Prior art and its problems) Conventionally, it has been known to use an acrylamide polymer as a paper strength agent in the papermaking industry. In recent years, as a part of energy saving measures and environmental measures, the papermaking process has been closed, and accordingly, the addition rate of the conventionally used sulfate band has naturally been limited.

Therefore, it is desired to develop a drug that can exert a sufficient paper strength effect even in the case of adding or not adding a sulfate band. Examples of paper strength agents that can be used in the area include (a) acrylamide and (b) a basic monomer such as dimethylaminoethyl methacrylate;
(C) Amphoteric water-soluble copolymers comprising an α, β unsaturated monocarboxylic acid or dicarboxylic acid have been proposed (for example, JP-A-54-30913, JP-A-60-94697).

The effect of this type of polyacrylamide-based paper strength enhancer is mainly due to the hydrogen bond between the amide group in the polymer and the hydroxyl group of the cellulose fiber, but the paper strength enhancer effectively exerts the paper strength. In order to do so, it is, of course, necessary to adsorb or fix the cellulose fibers or fine fibers constituting the paper. Therefore, in order to increase the fixing rate to the cellulose fibers or fine fibers constituting the paper, both a cationic functional group and an anionic functional group are introduced. Means that the amount of amide moiety that is effective for the development of paper strength is reduced accordingly, so that the optimum range is naturally set for the amounts of these functional groups to be introduced. There is a limit to the increase in the effect of the paper strength agent.

(Problems of the Invention) Therefore, an object of the present invention is to increase the paper strength enhancing effect of the amphoteric polyacrylamide-based copolymer.

(Means for Solving the Problems) The present invention relates to (a) 99.5 to 40 mol% of acrylamide and / or methacrylamide (b) α, β-unsaturated mono- and / or dicarboxylic acid, and / or salts thereof 20 mol% (c) Water-soluble cationic monomer and / or salts thereof 0 to 20 mol% (d) General formula (Wherein, m and n are 1 to 4, R ₁ is a hydrogen atom or a methyl group. R ₂ and R ₃ are the same or different lower alkyl groups having 1 to 3 carbon atoms, and X is an anionic counter ion. , A
Represents -O- or -NH-).
An additive for papermaking, which contains a copolymer having a constituent monomer component of up to 20 mol%.

In the present invention, acrylamide or methacrylamide as the component (a) may be used alone or in combination, but acrylamide is preferred from the viewpoint of economy.

Examples of the α, β-unsaturated mono- and / or dicarboxylic acid monomer (c) component include monocarboxylic acids such as acrylic acid and methacrylic acid, dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; And alkali metal salts such as sodium salt and potassium salt or ammonium salt thereof, and one or more kinds thereof may be used.

Representative examples of the cationic monomer (c) component include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth) acrylamide. Vinyl monomers having tertiary amino groups or salts of inorganic or organic acids thereof such as hydrochloric acid, sulfuric acid or acetic acid, or tertiary amino group-containing vinyl monomers and quaternization such as methyl chloride, benzyl chloride, dimethyl sulfate or epichlorohydrin And a vinyl monomer containing a quaternary ammonium salt obtained by reaction with an agent.

The betaine-type monomer as the component (d) includes:
It is possible to introduce high ions having both charges of cation and anion, and various betaine-type monomers copolymerizable with the above-mentioned components (a) to (d) can be used. It can be obtained by reacting a monomer having a secondary amine with a halogen-substituted carboxylic acid such as monochloroacetic acid.

The present invention uses a betaine-type monomer having a cationic group and an anionic group in obtaining the above-mentioned polyacrylamide-based copolymer, so that either the component (b) having an anionic group or the component (c) having a cationic group is used. By using one of them together, a papermaking additive having a desired paper strength enhancing effect can be prepared. The addition amount is 0.5 to 20 with respect to the total molar amount of the other copolymer constituting components.
It is used in the range of mol%. However, it is preferable to use the component (c) and the component (d) in combination with the component (b), so that the pH is not affected by the fluctuation of pH during papermaking, and the pH is wide.
Within this range, an excellent paper strength enhancing effect can be exhibited. Therefore, the combined amount of the components (d) and (c) is preferably prepared as follows. That is, the sum of the components (d) and (c) is 0.5 to 20 mol%, and (d)
It is preferable that the ratio of the component to the component (c) is (d) / (c) = 1/9 to 9/1.

When the addition amount is less than the above range, a sufficient paper strength enhancing effect cannot be obtained, and when the addition amount is too large, the reduction of the component (a) causes a decrease in the paper strength enhancing effect and disadvantages in terms of economy and the like. is there.

Also, appropriate ranges are naturally set for the four components (a), (b), (c), and (d). That is, component (a) is 99.5 to 40 mol%, preferably 97 to 65 mol%, component (b) is 0 to 20 mol%, preferably 1 to 15 mol%, and component (c) is 0 to 20 mol%. , Preferably 1 to 10 mol%, and the component (d) should preferably be 1 to 10 mol%. Outside this range, a sufficient paper strength enhancing effect cannot be obtained.

In addition, if desired, in addition to the above-mentioned constituent monomers, it is also possible to introduce an arbitrary monomer copolymerizable therewith. Typical examples thereof include anionic monomers such as vinyl sulfonic acid and styrene sulfonic acid, or esters of alcohols having 1 to 8 carbon atoms with acrylic acid or methacrylic acid, methacrylamide, acrylonitrile, styrene, vinyl acetate, methyl acetate, and the like. Nonionic monomers such as vinyl ether are exemplified.

The synthesis of the copolymer used in the present invention can be performed by various conventionally known methods. For example, the above-mentioned monomer and water are charged into a predetermined reaction vessel, and a persulfate such as potassium persulfate or ammonium persulfate, or a redox-type polymerization initiator in the form of a combination thereof with a reducing agent such as sodium hydrogen sulfite is usually used. The desired copolymer can be obtained by adding a radical polymerization initiator of the formula (1) and, if necessary, appropriately using a chain transfer agent such as isopropyl alcohol and allyl alcohol and heating under stirring.

(Action) In the present invention, by using an amphoteric copolymer containing the component (d) as a monomer component as a papermaking additive,
Although the reason why the excellent effect can be obtained is not the present condition, the high ion introduction can be achieved without significantly reducing the amide group which exerts the paper strength enhancing effect even if the copolymerization ratio is small by copolymerization of the component (d). It is thought to be possible. Further, it is presumed that the ionic interaction is formed as a stronger bond by having a cation and an anion charge in one group.

Further, it is considered that the combination of the component (d) and the component (c) exhibits more excellent performance due to the synergistic effect of the component (d) and the component (c). Although the cause of the synergistic effect is not clear, the combined use of the component (c) improves the copolymerizability of the components (a), (b), (c) and (d) and disperses the charge appropriately. By
It is believed that it will exhibit better performance.

In addition, the introduction of the tertiary amine as the component (c) acts as a regulator of the ion dissociation state with respect to a change in pH, so that a polymer having a charge state suitable for each pH can be obtained, exhibiting an excellent effect over a wide pH range. It is presumed to do.

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 8 and Comparative Examples 1 to 4 (Example 1) A 40% aqueous acrylamide solution was placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube.
5 g, 80% aqueous solution of acrylic acid 2.9 g, dimethylaminoethyl methacrylate 5.0 g, dimethylaminoethyl methacrylate / monochloroacetic acid reactant 8.1 g, and ion-exchanged water 28
4 g was charged, the pH was adjusted to 4.1 with a 15% aqueous sulfuric acid solution, and oxygen in the reaction system was removed through nitrogen gas. Then, while stirring, 0.24 g of ammonium persulfate and 0.10 g of sodium hydrogen sulfite were added as a polymerization initiator, the temperature was raised to 85 ° C, and the temperature was kept at 85 ° C for 2 hours. After cooling, a copolymer aqueous solution having a pH of 4.6, a concentration of 15.3%, and a viscosity (25 ° C.) of 11,000 centipoise was obtained. This is designated as Paper Strengthener A.

The above was taken as Example 1, and the remaining Examples 2 to 8 and Comparative Examples 1 to 4 were also changed in the monomer composition, and the amounts of the 15% sulfuric acid aqueous solution and the polymerization initiator were changed accordingly. The same operation as described above was performed to obtain a copolymer aqueous solution. These were designated as paper strength agents BH and ad. The property values of each of the examples and comparative examples are shown in Table 1 below.

(Test Example) Sulfuric acid band was added to 420 ml of Canadian Standard Freeness (CSF) obtained from waste corrugated paper so that the concentration becomes 0% at pH 6.8 and 1.6% at pH 5.5, and then the above Examples and Comparative Examples 0.6% with respect to pulp was added to each aqueous solution of the copolymer obtained as a paper strengthening agent, and after stirring, the pulp slurry was diluted to a concentration of 0.1%. It was pressed, then dried with a drum dryer at 105 ° C. for 3 minutes, conditioned at 20 ° C. and 65% RH for 24 hours, and the specific burst strength was measured according to JIS P-8112. The results are shown in Table 2 below.

Claims (2)

(57) [Claims] 1. (a) 99.5 to 40 mol% of acrylamide and / or methacrylamide (b) 0 to 20 mol% of α, β-unsaturated mono- and / or dicarboxylic acids and / or salts thereof (c) water solubility Cationic monomers and / or salts thereof 0 to 20 mol% (d) General formula (Wherein, m and n are 1 to 4, R ₁ is a hydrogen atom or a methyl group. R ₂ and R ₃ are the same or different lower alkyl groups having 1 to 3 carbon atoms, and X is an anionic counter ion. , A
Represents -O- or -NH-).
An additive for papermaking, comprising a copolymer containing up to 20 mol% of a constituent monomer component. 2. The sum of component (d) and component (c) is 0.5 to 2
2. The papermaking additive according to claim 1, wherein the molar ratio is 0 mol%, and the ratio of the component (d) to the component (c) is (d) / (c) = 1/9 to 9/1. .