JPH0689519B2 - Paper clarification agent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a clearing agent for paper.

(Prior Art) Transparent paper has been used for various purposes, but in recent years,
With the development and spread of copying machines, the demand for transparent paper as copy paper has increased.

As the transparent paper, (a) a natural trepe produced by beating pulp fibers to a high degree, (b) an impregnated trepe obtained by impregnating a high-quality paper with a resin as a clarifying agent, and (c) a synthetic resin film as a base Synthetic paper and the like are generally known.

The required performances of these transparent papers are (1) good transparency and no unevenness of transparency, (2) good dimensional stability,
(3) Strength (particularly tear strength) is high, (4) Writability and foldability are good, and (5) Inexpensive.

The performance of these transparent papers is generally understood as follows, and each has advantages and disadvantages. That is, the natural trepe of the above (a) has low fiber strength because it promotes fibrillation of fibers by beating, and is not sufficient in terms of transparency and dimensional stability. (B)
The impregnated trepe has almost no problem in terms of strength and dimensional stability, but it is insufficient in terms of transparency and uneven transparency. The synthetic paper (c) is excellent in transparency, strength, and dimensional stability, but has problems in writability, foldability, and price.

(Problems to be Solved by the Invention) The present invention focuses on the fact that it has a higher strength and is less expensive than a high beating pulp, and the impregnation that can be easily applied to general high-quality paper having a relatively low beating degree. Focusing on the trepe, it is intended to solve the above-mentioned drawbacks of the conventional impregnated trepe. That is, it is an object of the present invention to provide a transparentizing agent for an impregnated trepe, which has good impregnability and does not cause transparency unevenness in the formed paper, and can impart various required performances such as excellent transparency and writability. And

(Means for Solving the Problems) In view of the above technical background, the present inventors have conducted intensive studies to solve the technical problems of the conventional impregnated trepe, and as a result, as a clarifying agent, a specific polymer dispersion was used. The inventors have found that the above problems can be solved by using an aqueous copolymer dispersion prepared by emulsion polymerization in the presence of a stabilizer, and have completed the present invention.

That is, the present invention is a styrene and / or (meth) in the presence of a water-soluble salt of a (meth) acrylic acid-based and / or styrene-based copolymer having a carboxyl group and having a solid dispersion value of 100 to 300. An aqueous dispersion of a copolymer obtained by emulsion-polymerizing an acrylate ester, which has a minimum film-forming temperature of 30 to 80 ° C. and a particle diameter of 0.01 to 0.2 μm as an active ingredient. Involved in paper transparency treatment agents.

The paper clarifying agent of the present invention can be easily applied to inexpensive general high-quality paper having a relatively low beating degree and has good impregnation property, so that it does not cause uneven transparency on the obtained transparent paper. In addition, there is an advantage that various required performances such as excellent transparency and writability can be imparted.

As described above, in the present invention, a water-soluble salt of a specific copolymer is used as a dispersion stabilizer and has a specific physicochemical constant obtained by emulsion-polymerizing a polymerizable vinyl monomer in the presence of such a dispersion stabilizer. It is essential to use a clarifying agent containing an aqueous copolymer dispersion as an active ingredient, and the object of the present invention can be achieved only by using the clarifying agent.

As a conventionally known transparentizing agent for paper, a copolymer dispersion using a surfactant such as alkylbenzene sulfonic acid and polyoxyethylene alkyl ether sulfate is known, and the known copolymer is known. The transparent paper obtained by applying the dispersion generally has a poor size effect due to the activator, and when the transparent paper is defibrated, there are problems such as severe foaming during the defibration process. Since it is inferior in properties, it has disadvantages such as insufficient transparency of the paper and uneven transparency. On the other hand, in the present invention, since the water-soluble salt of the copolymer is used as the polymer type dispersion stabilizer, such a drawback does not exist.

The configuration of the present invention will be described below.

In the present invention, a water-soluble salt of the following specific copolymer is used as a polymer type dispersion stabilizer. That is, it is essential to use a water-soluble salt of (meth) acrylic acid and / or a styrene copolymer having a carboxyl group and having a solid dispersion value of 100 to 300. The monomer composition of the copolymer is not particularly limited as long as it has a carboxyl group and a solid content acid value within the above range, but the minimum film forming temperature (hereinafter referred to as MFT) and particle diameter of the obtained clearing agent. It is decided in consideration of.

Usually, it is necessary to use a (meth) acrylic acid ester or styrene as a main monomer, and to use a predetermined amount of a copolymerizable carboxylic acid monomer in combination so that the solid dispersion value of the obtained polymer type dispersion stabilizer is within the above range. . The following monomer composition can be illustrated as a preferable specific example. That is, (a) at least one selected from ethyl acrylate, methyl methacrylate and styrene (hereinafter referred to as a monomer (a)), (b) a copolymerizable carboxylic acid monomer (hereinafter referred to as a monomer (b)), and ( C)
It is a monomer mixture composed of other α, β-ethylenically unsaturated monomers (hereinafter referred to as monomer (c)).
Examples of the monomer (b) include monobasic acids such as acrylic acid, methacrylic acid and crotonic acid, unsaturated dibasic acids such as maleic acid, fumaric acid and itaconic acid, and anhydrides thereof.
The half ester is mentioned. Examples of the monomer (c) include acrylic acid ester or methacrylic acid ester other than the monomer (a), acrylonitrile, acrylamide, methylol acrylamide, vinyl acetate, vinyl versatate, vinyl propionate and the like. Moreover, cationic monomers such as dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, diethylaminopropyl methacrylate, and dimethylaminoethyl acrylamide can also be exemplified.

The amount of monomer (a) used is 40 to 90 based on all monomers.
It is about wt%, preferably 50 to 85 wt%. When the amount used is out of the above range, the emulsifying ability of the obtained dispersion stabilizer during emulsion polymerization is lowered, and a stable aqueous dispersion cannot be obtained. The amount of the monomer (b) used is appropriately determined so that the obtained dispersion stabilizer solid content has an acid value of 100 to 300, but is generally about 10 to 55% by weight, preferably about 10 to 55% by weight, based on the total monomers. It is set to 15 to 45% by weight. If the acid value of the solid content of the dispersion stabilizer is less than 100, the hydrophilicity of the dispersion stabilizer decreases, so that the emulsifying ability during emulsion polymerization becomes poor and a stable copolymer aqueous dispersion cannot be obtained. On the other hand, when the acid value exceeds 300, the hydrophilicity of the dispersion stabilizer becomes excessive, and the water resistance of the resulting clearing agent and the size of transparent paper deteriorate. The amount of the monomer (C) used is about 0 to 65% by weight, preferably 0 to 40% by weight, based on all the monomers. If the amount used exceeds 65% by weight, the emulsifying ability of the dispersion stabilizer decreases, which is not preferable.

The method for producing the copolymer, which is the above-mentioned polymer type dispersion stabilizer, is not particularly limited, and can be easily produced, for example, by adopting a known solution polymerization method. Specifically, a monomer mixture consisting of the predetermined amounts of the monomers (a), (b) and (c), benzene, toluene, xylene, isopropyl alcohol, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cellosolves,
Organic solvents such as carbitols, known peroxide catalysts such as benzoyl peroxide, di-t-pentyl peroxide, dicumyl peroxide, t-butylperoxy (2-ethylhexanoate), and optionally mercaptans A chain transfer agent such as the above may be charged into the reactor, and the polymerization reaction may be carried out in the presence or absence of an inert gas by a desired monomer supply mode such as simultaneous, divided, or dropwise addition.
The amount of the organic solvent, the peroxide catalyst, the chain transfer material, etc. is not particularly limited, and any of them can be used within a general range. The polymerization reaction temperature is usually about 50 to 200 ° C, and the reaction time is 1
~ 10 hours. After the completion of the polymerization reaction, the organic solvent is distilled off under reduced pressure or steam distillation, and then water and ammonia, an organic amine, a neutralizing agent such as an alkali metal hydroxide is added to the reaction system, and the neutralization degree is usually 70- By adjusting the dilution to about 120%, the desired aqueous solution of the copolymer salt of the dispersion stabilizer can be obtained. Examples of organic amines include triethylamine, triethanolamine, dimethylaminoethanol, 2-methyl-2-aminopropanol, and the like, and examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and the like. .

In the present invention, in the presence of the aqueous solution of the copolymer salt, which is the dispersion stabilizer obtained as described above, the polymerizable vinyl monomer is emulsion-polymerized to identify the active ingredient of the clearing agent of the present invention. A copolymer aqueous dispersion of can be obtained.

The type of the polymerizable vinyl monomer is limited in order to obtain an intended copolymer aqueous dispersion having a specific constant number, and specifically, styrene and / or (meth) acrylic acid ester (hereinafter referred to as monomer ( D))). Here, as the (meth) acrylic acid ester, the constituent alcohol has a carbon number of about 1 to 20. In addition, up to 20% by weight of the amount of the monomer (D) used,
You may substitute and use it for (beta) -ethylenically unsaturated monomer. The unsaturated monomers include nonionic and cationic monomers. Specifically, acrylonitrile, acrylamide, methylol acrylamide, vinyl acetate, vinyl versatate, vinyl propionate, 2
Nonionic monomers such as hydroxyethylmethacrylate; cationic monomers such as dimethylaminoethylmethacrylate, diethylaminoethylmethacrylate, diethylaminopropylmethacrylate and dimethylaminoethylacrylamide.

The method for producing the desired aqueous copolymer dispersion is not particularly limited, and a known emulsion polymerization method can be used as it is. The charging ratio of the copolymer salt which is a softening stabilizer (in terms of solid content) and the polymerizable vinyl monomer is not particularly limited, but usually the former: the latter is about 1 to 50:99 to 50 in weight ratio, preferably Is 5 to 30:95 to 70. When the amount of the copolymer salt used is less than 1, the emulsifying property during emulsion polymerization is lowered. Further, there is a disadvantage that the transparency of the transparent paper impregnated with the obtained aqueous dispersion is insufficient or the transparency becomes uneven. On the other hand, when the amount of the copolymer salt used exceeds 50, the impregnating property of the obtained aqueous dispersion is lowered, and the transparency of the transparent paper is lowered, and the uneven transparency occurs.

The method of supplying the polymerizable vinyl monomer may be a simultaneous charging, dividing, or dropping, and a desired charging method may be adopted.As a polymerization catalyst, known water-soluble agents such as sodium persulfate, potassium persulfate, and a water-soluble azo polymerization initiator are used. A polymerization initiator can be used, and a redox system combined with a reducing agent can also be adopted. If necessary, a chain transfer agent may be used in combination. Polymerization temperature is usually about 40-95 ℃, reaction time is 1-
It is about 10 hours. In the emulsion polymerization, known nonionic and anionic surfactants may be used, but it is necessary to use an amount that does not cause disadvantages such as size reduction of transparent paper and foaming during disaggregation. There is. Usually, it is less than 75% by weight with respect to the monomer added during emulsion polymerization, and less than 20% by weight with respect to the dispersion stabilizer.

The copolymer aqueous dispersion thus prepared had a MET of 3
It is suitable that the temperature is 0 to 80 ° C. and the particle size is 0.01 to 0.2 μm. When the MET is less than 30 ° C., the transparency and the transparency unevenness of the obtained transparent paper are inferior, and the adhesion trouble with the roll is apt to occur during the calendering. If the temperature exceeds 80 ° C., the copolymer dispersion, which is a clarifying agent, will not be sufficiently melted by heat during calendering and the transparency will be lowered, which is not preferable. If the particle diameter is out of the above range, impregnability is deteriorated in any case, which is not preferable. In addition,
The pH of the obtained copolymer aqueous dispersion is not particularly limited, but is usually about 6 to 12.

The aqueous copolymer dispersion obtained as described above can be used as a clarifying agent as it is or by diluting it appropriately. As a diluent, in addition to water, methanol,
Although lower alcohols such as ethanol and isopropyl alcohol can be used, the amount of the lower alcohol used is usually less than about 20% by weight based on the product.
The lower alcohol is not limited to being added after the reaction and may be added before the reaction.

As a method for applying the clearing treatment agent of the present invention, the treatment agent is generally used in an amount of 5 to 150% by weight, preferably 10% by weight in terms of solid content, with respect to general fine paper having a basis weight of about 20 to 100 g / m ^2. ~ 100
It can be carried out by coating or impregnating so as to be a weight%.

(Examples) Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In each Example, parts and% are specially noted. All are by weight unless otherwise noted.

Reference Example 1 A reaction container equipped with a stirrer, a reflux condenser and a thermometer was charged with 80 parts of methyl isobutyl ketone, heated to 118 ° C., and then heated from 118 parts of ethyl acrylate, 20 parts of methyl methacrylate and 30 parts of methacrylic acid. Monomer mixture and t-
A mixture of 5 parts of butyl peroxy (2-ethylhexanoate) and 20 parts of methyl isobutyl ketone was added dropwise under a nitrogen stream over 2 hours, and the mixture was kept warm for 2 hours for polymerization. Then, the solvent and by-products are distilled off under reduced pressure by heating,
By adding 224 parts of water and 21 parts of 28% ammonia water and neutralizing and dissolving, solid dispersion value is 185, nonvolatile content is 30%, viscosity is 95c.
A dispersion stabilizer A having a ps of pH 8.5 was obtained.

Reference Example 2 Methyl isobutyl ketone was placed in the same reaction vessel as in Reference Example 1.
Charge 80 parts, raise the temperature to 118 ° C, and then use ethyl acrylate 70
Part, methyl methacrylate 10 parts, maleic anhydride, 5 parts and a mixture of monomers consisting of 15 parts methacrylic acid and t-
A mixture of 5 parts of butyl peroxy (2-ethylhexanoate) and 20 parts of methyl isobutyl ketone was added dropwise under a nitrogen stream over 2 hours, and the mixture was kept warm for 2 hours for polymerization. Then, the solvent and by-products are distilled off under reduced pressure by heating,
By adding 228 parts of water and 17 parts of 28% ammonia water and neutralizing and dissolving, solid acid value is 145, nonvolatile content is 30%, viscosity is 80c.
A dispersion stabilizer B having a ps and a pH of 8.7 was obtained.

Reference Example 3 In the same reaction vessel as in Reference Example 1, cellosolve acetate 80 was added.
Then, after heating up to 150 ° C., a monomer mixture consisting of 60 parts of styrene, 10 parts of ethyl acrylate and 30 parts of acrylic acid, and a mixture of 5 parts of di-t-butyl peroxide and 20 parts of cellosolve acetate were added with a nitrogen stream. The mixture was added dropwise under 2 hours and kept warm for 2 hours for polymerization. Then, the solvent and by-products were distilled off under heating and reduced pressure, and 208 parts of water and 37 parts of dimethylaminoethanol were added to neutralize and dissolve, so that the solid dispersion number was 221, the nonvolatile content was 30.2%, and the viscosity was 600 cp.
A dispersion stabilizer C having a pH of s and a pH of 9.3 was obtained.

Reference Example 4 The same reaction vessel as in Reference Example 1 was charged with 80 parts of toluene,
After heating to 110 ° C, 40 parts of styrene, maleic anhydride,
A mixture of 5 parts and 55 parts of maleic acid-isopropyl cellosolve half ester and a mixture of 5 parts of t-butylperoxy (2-ethylhexanoate) and 20 parts of toluene were added under a nitrogen stream for 2 hours. Drop 2
Polymerization was carried out while keeping the temperature for a while. Next, the solvent and by-products were distilled off under reduced pressure with heating, and 225 parts of water, 12 parts of 28% ammonia water and 8 parts of dimethylaminoethanol were added to neutralize and dissolve, so that the solid content acid value was 227 and the nonvolatile content was 28.5%. %, Viscosity 9
A dispersion stabilizer D of 00 cps and pH 8.9 was obtained.

Example 1 A reaction vessel similar to that of Reference Example 1 was charged with 80 parts of the dispersion stabilizer A obtained in Reference Example 1 and 152 parts of water, and after heating to 80 ° C., from 80 parts of styrene and 20 parts of 2-ethylhexyl acrylate. 3 parts of an aqueous solution containing 0.5 parts of ammonium persulfate, 0.5 parts of sodium hydrogen carbonate and 24 parts of water.
The mixture was added dropwise over a period of time, and then the mixture was kept warm for 2 hours to carry out polymerization, and the average particle diameter was 0.07 μm, nonvolatile content was 35.2%, viscosity was 7 cps, and pH was 8.
A clearing agent E having an MFT of 50 ° C. was obtained. The solid content ratio of the dispersion stabilizer and the emulsion copolymer is 19:81.

Example 2 33 parts of the dispersion stabilizer B obtained in Reference Example 2, 154 parts of water and 5 parts of isopropyl alcohol were charged in the same reaction container as in Reference Example 1, and after heating to 80 ° C., 70 parts of styrene and methyl methacrylate. A monomer mixture consisting of 10 parts and 20 parts of 2-ethylhexyl acrylate and an aqueous solution consisting of 0.5 parts of ammonium persulfate, 0.5 parts of sodium hydrogen carbonate and 24 parts of water were added to 3 parts.
The mixture was added dropwise over a period of time, and then the mixture was kept warm for 2 hours for polymerization, and the average particle diameter was 0.08 μm, the nonvolatile content was 35.0%, the viscosity was 8 cps, and the pH was 8.
A clearing agent F having a MFT of 55 ° C. was obtained. The solid content ratio of the dispersion stabilizer and the emulsion copolymer is 9:91.

Example 3 A reaction container similar to that of Reference Example 1 was charged with 120 parts of the dispersion stabilizer C obtained in Reference Example 3 and 146 parts of water, and after heating to 80 ° C., 40 parts of styrene, 40 parts of methyl methacrylate and acrylic acid. Butyl
20 parts monomer mixture and ammonium persulfate
An aqueous solution consisting of 0.5 part, 0.5 part of sodium hydrogen carbonate and 24 parts of water was added dropwise over 3 hours, and then the mixture was kept warm for 2 hours for polymerization to obtain an average particle diameter of 0.06 μm, a nonvolatile content of 35.3% and a viscosity of 13
Clarification treatment agent G with cps, pH 9.0 and MFT 40 ° C. was obtained. The solid content ratio between the dispersion stabilizer and the emulsion copolymer is 26:74.

Example 4 80 parts of the dispersion stabilizer D obtained in Reference Example 4 and 146 parts of water were charged in the same reaction vessel as in Reference Example 1, and the temperature was raised to 80 ° C.
Monomer mixture consisting of 70 parts, 10 parts of methyl methacrylate and 20 parts of 2-ethylhexyl acrylate, 0.5 parts of ammonium persulfate, 0.5 parts of sodium hydrogen carbonate and 24 parts of water
Part of the aqueous solution was added dropwise over 3 hours, and then the mixture was kept warm for 2 hours for polymerization to have an average particle diameter of 0.1 μm and a nonvolatile content of 35.
A clearing agent H having a viscosity of 9%, a pH of 9.2, and an MFT of 60 ° C. was obtained. The solid content ratio of the dispersion stabilizer and the emulsion copolymer is 19:81.

Example 5 A reactor similar to that of Reference Example 1 was charged with 60 parts of the dispersion stabilizer A obtained in Reference Example 1 and 152 parts of water.
Monomer mixture consisting of 70 parts, 10 parts of 2-hydroxyethyl methacrylate and 20 parts of 2-ethylhexyl acrylate, 0.5 parts of ammonium persulfate, sodium hydrogen carbonate
An aqueous solution consisting of 0.5 parts and 24 parts of water was added dropwise over 3 hours, and then the mixture was kept warm for 2 hours for polymerization, and the average particle size was 0.08μ.
m, a non-volatile content of 35.2%, a viscosity of 10 cps, a pH of 8.0, and an MFT of 50 ° C were obtained as a clearing agent I. The solid content ratio of the dispersion stabilizer and the emulsion polymer is 15:85.

Comparative Example 1 80 parts of the dispersion stabilizer A obtained in Reference Example 1 and 152 parts of water were charged in the same reaction vessel as in Reference Example 1 and heated to 80 ° C., and then styrene was added.
Aqueous solution consisting of 100 parts, 0.5 parts of ammonium persulfate, 0.5 parts of sodium hydrogen carbonate and 24 parts of water was added dropwise over 3 hours, and then the mixture was kept warm for 2 hours for polymerization to carry out an average particle diameter.
0.1μm, non-volatile content 34.5%, viscosity 8cps, pH7.9, MFT85 ℃
To obtain a clearing agent J. The solid content ratio of the dispersion stabilizer and the emulsion copolymer is 19:81.

Comparative Example 2 80 parts of the dispersion stabilizer B obtained in Reference Example 2 and 152 parts of water were charged in the same reaction vessel as in Reference Example 1 and heated to 80 ° C., and then styrene was added.
A monomer mixture consisting of 50 parts and 50 parts of 2-ethylhexyl acrylate and an aqueous solution consisting of 0.5 parts of ammonium persulfate, 0.5 parts of sodium hydrogen carbonate and 24 parts of water were added dropwise over 3 hours, and then the mixture was kept warm for 2 hours to carry out polymerization, Average particle size 0.09μm, non-volatile content 35.0%, viscosity 8cps, pH8.1, M
A clearing agent K having an FT of 5 ° C. was obtained. The solid content ratio of the dispersion stabilizer and the emulsion copolymer is 19:81.

Comparative Example 3 In a reaction vessel similar to that of Reference Example 1, 150 g of water and 2 g of sodium dodecylbenzenesulfonate were charged and dissolved, and the temperature was raised to 80 ° C., and then 80 parts of styrene, 2 parts of methacrylic acid and 2 parts of acrylic acid.
A monomer mixture consisting of 18 parts of ethylhexyl and an aqueous solution consisting of 0.5 part of ammonium persulfate, 0.5 part of sodium hydrogen carbonate and 24 parts of water were added dropwise over 3 hours, and then the mixture was kept warm for 2 hours for polymerization. Then 28% ammonia water 1.
By adding 4 parts, a clearing agent L having an average particle size of 0.08 μm, a non-volatile content of 35.3%, a viscosity of 15 cps, a pH of 8.1, and an MFT of 50 ° C. was obtained.

Preparation of transparent paper A high-quality paper having a basis weight of 50.0 g / cm ² and a transparency of 32.0% was used in Examples 1 to 1.
The transparentizing agents E to L obtained in Example 5 and Comparative Examples 1 to 3 were respectively impregnated and dried, and then calendered under conditions of 100 ° C. and 10 kg / cm ² to obtain transparent papers.
The transparent paper impregnated with the clarifying agent K obtained in Comparative Example 2 had a problem of sticking to the roll during calendaring.

Evaluation method Transparency: Measured at 450 nm using a photocell type transparency meter. Transparency unevenness: Three-level evaluation of excellent, good, and poor by visual inspection. Impregnation: Floating high-quality paper before impregnation on a clearing agent, making the entire paper uniform. Evaluation by time required for impregnation The above evaluation results are shown in Table 1.

(Effects of the Invention) Since the clarifying agent of the present invention has excellent impregnating properties, it is possible to obtain transparent paper (impregnated trepe) having excellent transparency without transparency unevenness. The transparent paper has not only general properties such as strength, writability and dimensional stability, but also good sizeability.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08F 220/10 MMB 7242-4J D21H 19/20

Claims (3)

[Claims] 1. A solid group having a carboxyl group and an acid value of 100.
A copolymer aqueous dispersion obtained by emulsion-polymerizing styrene and / or a (meth) acrylic acid ester in the presence of a water-soluble salt of a (meth) acrylic acid-based and / or styrene-based copolymer of 300 to 300. An agent for clarifying paper, characterized in that it has a minimum film forming temperature of 30 to 80 ° C. and a particle diameter of 0.01 to 0.2 μm as an active ingredient. 2. The monomer composition of the water-soluble salt of the (meth) acrylic acid-based or styrene-based copolymer is (a) at least one of ethyl acrylate, methyl methacrylate and styrene, which is 40 to 90% by weight, (B) Copolymerizable carboxylic acid monomer 10 to 55% by weight, and (c) other α, β-ethylenically unsaturated monomer 0 to
65% by weight of the clarifying agent according to claim 1. 3. The clarifying agent according to claim 1, wherein the solid content of the aqueous solution of the copolymer salt and the charged weight ratio of the polymerizable vinyl monomer are 1 to 50:99 to 50.