JPS62179504A - Production of resin binder for water-based flexographic ink - Google Patents

Abstract

PURPOSE:To produce the titled binder excellent in dryability, film gloss, pigment dispersion etc., by emulsion-polymerizing an ethylenically unsaturated monomer in the presence of a specified protective colloid. CONSTITUTION:A copolymer comprising 30-60mol% styrene, 20-60mol% maleic monoester (e.g., monoethyl maleate), or 20mol% (meth)acrylate [e.g., methyl (meth)acrylate] and 0-20mol% maleic acid and having an acid value of 50-300 is neutralized to a degree of neutralization of the carboxyl groups of the copolymer of 7-100% to obtain a protective colloid comprising a water- soluble salt of the copolymer. 10-1,000pts.wt. ethylenically unsaturated monomer comprising 10-100wt% styrene, 0-50wt% nitrogen-containing ethylenically unsaturated monomer and 0-50wt% other ethylenically unsaturated nomoner is emulsion-polymerized at 20-95 deg.C in the presence of 100pts.wt. (in terms of solid matter) above protective colloid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a resin binder for water-based flexo ink, and more specifically, a water-based flexo ink suitable for printing on cardboard box paper, especially water-repellent liner paper. The present invention relates to a method for producing a resin binder for use in a plastic binder.

Conventional Technology In recent years, the demand for cardboard boxes as packaging materials has been increasing, and the demand for packaging foods, fresh fruits, marine products, etc. is particularly significant. However, in the case of food packaging, the cardboard box used as the packaging material is required to be water repellent, so the base paper for the cardboard box is usually a so-called water-repellent liner paper whose surface has been treated to make it water-repellent. has been done. Conventionally, solvent-based flexo inks have been mainly used for printing on Kawahara paper for corrugated boxes, but during ink production and printing, there are concerns about toxicity and danger caused by organic solvents, which are essential components of the inks. There were many problems. For this reason, in recent years, there has been a strong desire in the industry for the development of water-based printing inks such as water-based flexo inks, and various binders for these water-based inks have been studied.

Examples of the resin binder for water-based inks include aqueous alkaline solutions of natural resins such as Sieck A5 maleic acid-modified rosin, aqueous alkaline solutions of synthetic resins such as styrene-maleic acid copolymers, and acrylic copolymers. Resin emulsion type binders such as acrylic resin emulsions, acrylic resin emulsions, and styrene resin emulsions are known.

Water-soluble varnishes that use the above-mentioned water-soluble binders generally have fairly good pigment dispersibility, transferability to water-repellent liner paper, and adhesion properties, but their viscosity is higher than that of solvent-based binders, so when printing If you try to adjust the viscosity to a constant level, the resin content in the ink will decrease, and as a result, the coating [! The glossiness and drying properties (printed surface) tend to be poor. On the other hand, emulsion-type binders have insufficient pigment dispersibility, transferability to water-repellent liner paper, adhesion, etc., but on the other hand, they provide ink with a high solid content that is comparable to solvent-based binders. The ink tends to have high gloss and excellent drying properties. Therefore, as a binder for water-based ink for water-repellent liner paper, the above-mentioned water-soluble varnish and emulsion are currently used in combination to satisfy the required performance as much as possible.

However, when a water-soluble varnish and an emulsion are used together in this way, they are of a two-component type, which makes mixing work complicated when making ink, and the resulting ink deteriorates over time due to insufficient compatibility between the two. There are disadvantages such as stability problems.

Problems to be Solved by the Invention In view of the above-mentioned circumstances, the present inventors have developed a liquid-type water-based flexo which eliminates the drawbacks of conventional water-soluble varnishes and emulsions, and also combines the advantages of both. We have conducted extensive research with the aim of providing a resin binder for ink. As a result, when a water-soluble salt of a specific copolymer is used as a protective colloid and a specific 1ffi form is emulsion polymerized in its presence, a dispersion of the emulsion polymer that meets the above purpose is obtained. It has been discovered that it is possible to produce a new resin binder for water-based flexographic inks that eliminates all the drawbacks of the conventional technology. The present invention was completed based on this knowledge.

The present invention is a means for solving the problem, namely, (1) a copolymer of styrenes and a maleic acid monoester, and (2) a copolymer of a styrene, a maleic acid monoester, and an acrylic ester or a methacrylic ester ( These are hereinafter referred to as "(meth)acrylic esters") and/or copolymers with an acid value of 50 to 300 selected from copolymers of maleic acid. The present invention relates to a method for producing a resin pine goo for water-based flexo ink, which comprises emulsion polymerizing 10 to 1000 parts by weight of an ethylenically unsaturated monomer based on 100 parts solids of a water-soluble copolymer salt.

In the present invention, obtained using the above specific monomer,
Furthermore, it is important to use an aqueous solution of a water-soluble salt of a copolymer having a specific acid value as a protective colloid.

Examples of the monomers constituting the copolymer used as the protective colloid in the form of water-soluble salts include the following. That is, examples of styrenes include lower alkylstyrenes such as styrene and methylstyrene. Examples of maleic acid monoesters include monomethyl maleate, monoethyl maleate, mono(n-propyl) maleate, and mono(isopropyl) maleate.
, monomaleate (n-butyl), monomaleate (isobutyl), monomaleate (n-amyl), monomaleate (n-hexyl), monomaleate (2-ethylhexyl), monomaleate (n- octyl), monomaleate (n-decyl), monomaleate (isodecyl), monomaleate (n-lauryl), monomaleate (tridecyl), monomaleate (n-stearyl),
Monomaleate (methoxyethyl), monomaleate (
ethoxyethyl), monomaleate (isopropoxyethyl), monomaleate (n-butoxyethyl), monomaleate (stearoxyethyl), monomaleate (
methoxyethoxyethyl), monomaleate (ethoxyethoxyethyl), monomaleate (isopropoxyethoxyethyl), monomaleate (butoxyethoxyethyl), monomaleate (stearoxyethoxyethyl), etc. with 1 to 18 carbon atoms. Examples include aliphatic monoalcohols, esters of ethylene glycol monoalkyl ethers having 3 to 20 carbon atoms, or diethylene glycol monoalkyl ethers having 5 to 22 carbon atoms, and maleic acid.

In addition, examples of (meth)acrylic esters include methyl acrylate, ethyl acrylate, and acrylic 119n.
-Propyl, isopropyl acrylate, acrylic 1lQ
n-butyl, isobutyl acrylate, acrylic 1ln-
Amyl, isoamyl acrylate, acrylic 1Iin-hexyl, acrylic i! FI2-ethylhexyl, n-octyl acrylate, n-decyl acrylate, acrylic l
n-lauryl, acrylic 11n-stearyl, methoxyethyl acrylate, ethoxyethyl acrylate, isopropoxyethyl acrylate, 0-butoxyethyl acrylate, stearoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxy acrylate Aliphatic monohydric alcohols with 1 to 18 carbon atoms, ethylene glycol monoalkyl ethers with 3 to 20 carbon atoms, or diethylene glycol monoalkyl ethers with 5 to 22 carbon atoms, such as butoxyethoxyethyl acrylate, stearoxyethoxyethyl acrylate, etc. Examples include esters of alkyl ethers and acrylic acid, and corresponding esters of methacrylic acid.

The amount of each of the above monomers used is such that the acid value of the resulting copolymer is 5.
It is appropriately selected within the range of 0 to 300. Usually styrene 30-60 mol%, maleic acid monoester 2
0-60 mol%, (meth)acrylic acid ester 0-20
It is preferable to set it as the range of 0-20 mol% and maleic acid. Therefore, the copolymers used in the present invention include copolymers of styrenes and maleic esters, styrenes,
Maleic acid ester and (meth)acrylic acid ester 3
Original copolymers, styrenes, maleic esters, and maleic acid ternary copolymers, and styrenes, maleic esters, (meth)acrylic esters, and maleic acid quaternary copolymers are included.

In the case of any copolymer, the acid value is 50 to 3 as mentioned above.
It is important that the number is in the range of 00, and if it is less than 50, the salt obtained by the neutralization operation described later will not become a water-soluble salt and is unsuitable for use as a protective colloid. In addition, when the acid value exceeds 300, the water-soluble salt of the copolymer has good performance as a protective colloid, but even if it is used to emulsion polymerize ethylenically unsaturated 111ffi, the resulting polymer dispersion is not preferable as a resin binder for water-based inks because it has too low water resistance.

The copolymer and its water-soluble salt can be produced by any of the conventionally well-known bulk polymerization methods, solution polymerization methods, emulsion polymerization methods, and suspension polymerization methods. It can be manufactured according to the following. For example, in the case of solution polymerization, the copolymer can be easily produced by copolymerizing a predetermined amount of the constituent compound (m) in the presence of a suitable organic solvent.

The above quaternary copolymer is obtained by first copolymerizing styrene, maleic anhydride, and (meth)acrylic acid ester in the same manner as above, then adding the corresponding allure to the resulting copolymer. It can also be obtained by partial esterification.

To explain the above copolymerization reaction in more detail, the reaction can be carried out using a commonly used polymerization initiator, a peroxide catalyst such as benzoyl peroxide, di-butyl peroxide, or azobisisobutyronitrile, azobisisobutyric acid. It can be carried out according to a conventional method using an azo catalyst such as nitrile. Furthermore, mercaptans and the like can be added to the reaction system as necessary, thereby making it possible to adjust the degree of polymerization to one level as appropriate.

The copolymer obtained as described above can be made into a desired water-soluble salt by neutralizing it by adding aqueous ammonia or various organic amines into the reaction system after the copolymerization reaction is completed. Here, the amount of ammonia water etc. added is preferably within a range such that the degree of neutralization of carboxyl groups in the copolymer is about 70 to 110%. If this degree of neutralization is too low, the protective colloid performance of the resulting water-soluble salt aqueous solution will deteriorate, which is not preferable.

The water-soluble copolymer salt thus obtained can be used as a protective colloid in the present invention in the form of an aqueous solution, but it can also be purified, diluted or concentrated as necessary.

In the production of the resin binder for aqueous flexible ink of the present invention using the water-soluble salt of the copolymer obtained as described above as a protective colloid, in the presence of the protective colloid, an ethylenic binder is used based on 100 parts by weight of the solid content of the protective colloid. 10 to 1000 parts by weight of saturated monomer, preferably about 100 to 100 parts by weight
This is carried out by emulsion polymerization of 0 parts by weight.

Ethylenically unsaturated t subjected to emulsion polymerization in the above
The im form was selected in consideration of the water resistance, pigment dispersibility, drying property, transferability to water-repellent liner paper, adhesion property, etc. of the resulting resin binder for water-based flexographic ink. For example, the alkyl group has 1 to 2 carbon atoms.
(meth)acrylic ester of 2, water [4, (meth)acrylic ester having an amino group etc., acrylamide, methacrylamide, acrylonitrile, methacriminitrile, styrene, methylstyrene, vinyltoluene,
Examples include acrylic acid, methacrylic acid, maleic anhydride, maleic acid monoester, itaconic acid, and itaconic acid monoester. Among them, styrene, acrylonitrile, (meth)acrylic esters in which the alkyl group has 1 to 22 carbon atoms, (meth)acrylic esters containing amino groups,
Acrylamide, methacrylamide, etc. are preferred. The above monomers can be used alone or in combination.
It is also possible to use a combination of more than one species.

As mentioned above, the ethylenically unsaturated monomer must be used in a specific amount for the protective colloid, and if it is used in a product with less than 101 hanging parts, the content of the protective colloid component is If the binder becomes too large, a large number of water-soluble resin components will be present in the resulting binder, resulting in a low solid content and high viscosity. It will be inferior. On the other hand, when used with a hanging part content of 1,000 or more, the water-based flexographic ink using the obtained binder is unsatisfactory in terms of the above-mentioned Inn 4 performance, particularly in terms of transferability, resolubility, etc., and is also not preferred.

The emulsion polymerization of the ethylenically unsaturated monomer according to the method of the present invention can be carried out by various methods such as one-stage polymerization, divided addition, and continuous dropwise addition. In this case, a water-soluble polymerization initiator and an oil-soluble polymerization initiator can be used individually or in combination, and in either case, a desired emulsion can be suitably obtained.

However, in view of the fact that the polymerization rate is high and the viscosity of the resulting emulsion is low, it is preferable to use a water-soluble polymerization initiator and an oil-soluble polymerization initiator in combination.

As a specific example of this combination, for example, a water-soluble polymerization initiator and a portion of lf1 are added during initial polymerization to form polymer particles in advance, and then the oil-soluble polymerization initiator is dissolved in the remaining monomers. A preferred method is the so-called seed polymerization method, in which the particle size of the above-mentioned polymer particles is increased by adding the polymer particles. In this case, the monomer that undergoes the initial polymerization and the monomer that undergoes the post-polymerization do not need to be the same (although different monomers among the various monomers listed above may be used, or two or more monomers may be used in combination). When used as such, the composition ratio thereof can be changed as appropriate.

Specific examples of the water-soluble polymerization initiator include persulfate catalysts such as ammonium perliQ acid and potassium persulfate, and redox catalysts in which these are combined with resistant sulfite M salts. Examples of the oil-soluble polymerization initiator include peroxide catalysts such as benzoyl peroxide and (-butyl hydroperoxide), and azo catalysts such as azobisisobutyronitrile.

Furthermore, various molecular ff1W moderating agents similar to those used in the production of the protective colloid can also be added to the emulsion polymerization reaction system of the present invention, if necessary. The conditions for the emulsion polymerization reaction and the monomer concentration to be polymerized are not particularly limited, but the monomer concentration is usually about 10 to 65%, preferably about 20 to 55%, and the reaction temperature is usually The temperature is preferably about 20-95°C, preferably about 30-90°C.

In the method of the present invention, a desired stable dispersion can be obtained without using any surfactant in the emulsion polymerization reaction, but such a surfactant can be added if necessary.

The thus obtained resin binder for water-based flexographic ink of the present invention can be prepared in the same manner as general water-based resin binders,
For example, using a kneading machine such as a ball mill, attritor, or sand mill, a general inorganic pigment or aerobic pigment is mixed as a coloring agent, water, alcohol, etc. are used as a solvent, and if necessary, other various additives are added. By blending and kneading, water-based flexographic ink can be obtained.

ADVANTAGES OF THE INVENTION According to the present invention, it is possible to easily obtain a resin binder for water-based flexographic ink that has the advantages of both water-soluble varnishes and emulsions and has the advantages of both. The emulsion polymer dispersion obtained by the method of the present invention has a high solid content and low viscosity, so it has excellent drying properties and gloss of the dry coating film, as well as pigment dispersibility, transferability to water-repellent liner paper, and adhesion. In terms of properties, it is also much superior to conventional resin binders for water-based flexo inks of this type. Accordingly, by utilizing the present invention, it is possible to provide a water-based flexographic ink suitable for printing on corrugated board base paper, particularly liner paper base paper that has been subjected to water-repellent treatment.

EXAMPLES Hereinafter, the method of the present invention will be explained in more detail by giving an example of producing a protective colloid used in the present invention as a reference example, and then giving an example of producing a resin binder for a water-based flexographic ink of the present invention. Of course, it is not limited to these. In each case, parts indicate parts by weight.

Reference Example 1 1,894 parts of xylene was charged into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, and the internal temperature was 125-125.
The temperature was raised until it reached 130°C.

Next, a mixed solution consisting of 624 parts of styrene, 1097 parts of monobutyl cellosolve maleate, 173 parts of ethyl carpitol acrylate ester, and 84 parts of di-tert-butyl peroxide was added dropwise from the dropping funnel over a period of 4 hours, and then the mixture was heated to the same temperature. The mixture was kept warm for 3 hours to complete the polymerization reaction. The temperature was further increased to 180°C, and xylene was completely removed under reduced pressure.

The thus obtained 1q copolymer had an acid value of 130.3 and a softening point of 102°C.

Ammonia water and deionized water were added to the above copolymer to obtain a copolymer salt aqueous solution with a degree of neutralization of 100 and a solid content concentration of 30%. Hereinafter, this will be referred to as protective colloid (1).

Reference Example 2 1920 parts of xylene, 624 parts of styrene, 1291 parts of monobutyl cellosolve maleate, and ZTE
A polymerization reaction was carried out in the same manner as in Reference Example 1 using 84 parts of rt-butyl peroxide to obtain a copolymer.

The obtained copolymer had an acid value of 173.7 and a softening point of 122°C.

Next, the same operation as in Reference Example 1 was performed to obtain a degree of neutralization of 100,
A copolymer salt aqueous solution having a solid content concentration of 30% was obtained. The obtained aqueous solution is referred to as a protective colloid (2).

Example 1 Protective colloid (1) 19 was placed in a reaction vessel similar to Reference Example 1.
7 g, styrene 37 g, acrylonitrile 5 g, stearyl methacrylate 4 g and 120.80 g of a potassium persulfate aqueous solution with a concentration of 1.24% were charged, and the mixture was heated under a nitrogen stream for 10 g.
The mixture was stirred for a minute to emulsify, then heated to 80°C, reacted for 2 hours, and then cooled to room temperature. Furthermore, styrene 101 (1, 12 g of acrylonitrile,
Stearyl methacrylate 11 (+, 5.3 g of 75% benzoyl peroxide and 66 a of deionized water were added and emulsified by stirring for 10 minutes under a nitrogen stream.
The temperature was raised to .degree. C. and kept at the same temperature for 3 hours to complete the reaction and obtain an emulsion.

The obtained emulsion had a solid content concentration of 41.6% and a pH of
7.5, and had a viscosity of 130 cp. below,
This emulsion is referred to as the binder (1) of the present invention.

Example 2 Protective colloid (2) 20
3a, 35 g of styrene, 12 g of acrylonitrile, 1.35% concentration of potassium persulfate aqueous solution 111.2111
and 4.3 g of polyethylene glycol-polypropylene glycol block copolymer (polypropylene glycol molecular weight 2000, ethylene oxide chain content 20%) as an emulsifier, stirred for 10 minutes under a nitrogen stream to emulsify, and then emulsified at 80°C. After reacting for 2 hours, the mixture was cooled to room temperature. Furthermore, in the obtained dispersion,
95 g of styrene, 32 g of acrylonitrile, 5.3 g of 75% benzoyl peroxide, and 104 g of deionized water were added and emulsified by stirring for 10 minutes under a nitrogen stream. This was heated to 80° C. again and kept at the same temperature for 3 hours to complete the reaction and obtain an emulsion.

The obtained emulsion had a solid content concentration of 39.7% and a pH of
6,6, and had a viscosity of '+1 ocp. Hereinafter, this emulsion will be referred to as the binder (2) of the present invention.

Example 3 The reaction was carried out in the same manner as in Example 2, except that among the monomers used in the first and second stage emulsion polymerization, acrylonitrile was replaced with 2-ethylhexyl acrylate-1. , an emulsion was obtained.

The 1q emulsion has a solid content of 11 degrees and 40.5%,
It had a pH of 7.0 and a viscosity of 380 cp. Hereinafter, this emulsion will be referred to as the binder (3) of the present invention.

Example 4 An emulsion was obtained by carrying out the reaction in the same manner as in Example 2, except that acrylonitrile was replaced with ethyl acrylate among the monomers used in the first and second emulsion polymerizations.

The obtained emulsion had a solid content concentration of 39.0%, pl
-16.6 and a viscosity of 280 co. Hereinafter, this emulsion will be referred to as the binder (4) of the present invention.

Example 5 Protective colloid (1) 19 was placed in the same reaction vessel as in Reference Example 1.
1 (+), 26 g of styrene, 5 g of acrylonitrile, 16 g of butyl acrylate, and 126.8 g (+) of a 1.18% potassium persulfate aqueous solution (+) were charged, stirred for 10 minutes under a nitrogen stream to emulsify, and then heated to 80°C. After reacting for 2 hours, it was cooled to room temperature.Furthermore, 112 g of styrene and 1 g of acrylonitrile were added to the resulting dispersion.
2 (+, 5.3 g of 75% benzoyl peroxide and 66 g of deionized water were added and emulsified by stirring for 10 minutes under a nitrogen stream. The temperature was raised to 80°C again and 3 g of deionized water was added. The reaction was completed by keeping the temperature for an hour to obtain an emulsion.

The obtained emulsion had a solid content concentration of 41.0%, pl
-17.3, and had a viscosity of 70 cp. Hereinafter, this emulsion will be referred to as the binder (5) of the present invention.

Example 6 Protective colloid (2) 19 was placed in the same reaction vessel as in Reference Example 1.
2 (1, 38 g of styrene, 5 g of acrylonitrile, 3 g of stearyl methacrylate, N.

N-dimethylaminoethyl methacrylate 1g and 11
116.4 (l) of a 1.29% potassium persulfate aqueous solution was charged, stirred for 10 minutes under a nitrogen stream to emulsify, heated to 80°C, reacted for 2 hours, and then cooled to room temperature. Furthermore, styrene 102 (1
, acrylonitrile 14 g, stearyl methacrylate 8 g, N.

3 g of N-dimethylaminoethyl methacrylate, 2.4 g of azobisisobutyronitrile and 5 g of deionized water were added and emulsified by stirring for 10 minutes under a nitrogen stream. This was heated to 80° C. again and kept at the same temperature for 3 hours to complete the reaction and obtain an emulsion.

The obtained emulsion had a solid content IHI of 48.0%, p
It had H8.5 and a viscosity of 580 cp. Hereinafter, this emulsion will be referred to as the binder (6) of the present invention.

Example 7 Protective colloid <2>19 was placed in the same reaction vessel as in Reference Example 1.
2g, styrene 38g, acrylonitrile 5g, stearyl methacrylate 3o, N.

N-dimethylaminoethyl methacrylate 1g and 1m
1li1.29% potassium persulfate aqueous solution 116.4 (
1 and stirred for 10 minutes under a nitrogen stream to emulsify.
Next, the temperature was raised to 80° C. and the mixture was reacted for 2 hours, and then cooled to room temperature. Furthermore, styrene 1020 was added to the obtained dispersion.
．． Acrylonitrile 14g, stearyl methacrylate 8g, N.

3g N-dimethylaminoethyl methacrylate, 1i
T! 4 g of potassium acid and 35 g of deionized water were added, and the mixture was stirred for 10 minutes under a nitrogen stream to emulsify.

This was heated to 80° C. again and kept at the same temperature for 3 hours to complete the reaction and obtain an emulsion.

The emulsion prepared by 1 u had a solid content concentration of 45.9% and I
)) (8,4) and had a viscosity of 4900 cp.Hereinafter, this emulsion will be referred to as the binder (7) of the present invention.

A water-based ink was prepared as follows using the resin binder for water-based flexo ink of the present invention obtained in each of the above Examples, and its performance was tested.

Preparation of ink> The binder obtained in each of the above examples, cyanine blue, and desiccant were added so that the face F111 degree in the finished ink was 20% and the viscosity measured by Semen Cup N004 at 25°C was 14 to 16 seconds. A finished ink was prepared by blending with ionized water and kneading for 2 hours in a paint shaker.

For comparison, a commercially available water-soluble styrene-maleic acid resin varnish (manufactured by Arakawa Chemical Industry Co., Ltd., "Alastair 70")
0SJ) and deionized water, and after kneading cyanine blue in advance in a paint shaker for 2 hours,
By adding a commercially available styrenated shellac emulsion (manufactured by 11ki Shellac Co., Ltd., "Laccoat 5S6J"), the pigment concentration was 20%, and Semen Katsubu N.
Comparative finished ink No. 11 was prepared, which had a viscosity (25° C.) of 14 to 16 seconds as measured by O.O.4 and a solid molecular filfi ratio of water-soluble varnish to emulsion in the ink of 1:4.

<Ink property test> Each of the finished inks created above was applied to water-repellent liner paper (Honshu Paper Co., Ltd., "Super KJ") using a hand printer, and the gloss of the printed area of the resulting printed matter was measured. And the transferability to water-repellent liner paper was evaluated by visual judgment.

In addition, for each of the above finished inks, the viscosity (25°C) measured with Semen Cup N084 is 10~
Each sample was diluted with deionized water to give a drying time of 11 seconds, and the color was spread using a bar coater No. 6, and the drying properties were evaluated by touching the printed area with a finger. Those that dried in 10 to 15 seconds after the color development were evaluated as good, those that dried in 25 to 30 seconds as fair, and those that required 30 seconds or more to dry as poor.

The results of each of the above tests are shown in Table 1.

Table 1 From Table 1, all inks prepared using the resin binder for water-based flexographic inks of the present invention have very good gloss, transferability, and drying properties in the printed area, and these effects are as follows.
It can be seen that this is even better than the conventional two-component binder that uses a combination of water-soluble varnish and emulsion.

(that's all)

Claims (1)

[Scope of Claims] [1] (1) Copolymers of styrenes and maleic acid monoesters, and (2) copolymers of styrenes, maleic acid monoesters, and acrylic esters or methacrylic esters and/or maleic acid. Acid value 50-30 selected from polymers
0 as a protective colloid, and emulsion polymerization of 10 to 1000 parts by weight of an ethylenically unsaturated monomer based on 100 parts by weight of the solid content of the water-soluble salt of the copolymer. A method for producing a resin binder for water-based flexo ink, characterized by: [2] The maleic acid monoester is an ester of maleic acid with an aliphatic monoalcohol having 1 to 18 carbon atoms, an ethylene glycol monoalkyl ether having 3 to 20 carbon atoms, or a diethylene glycol monoalkyl ether having 5 to 22 carbon atoms. A method according to claim 1. [3] Acrylic ester or methacrylic ester is an aliphatic monohydric alcohol having 1 to 18 carbon atoms, ethylene glycol monoalkyl ether having 3 to 20 carbon atoms, or diethylene glycol monoalkyl ether having 5 to 22 carbon atoms, and acrylic acid or The method according to claim 1, which is an ester with methacrylic acid. [4] Ethylenically unsaturated monomer is styrene 10-10
The method according to claim 1, comprising 0% by weight of the nitrogen-containing ethylenically unsaturated monomer, 0 to 50% by weight of the nitrogen-containing ethylenically unsaturated monomer, and 0 to 50% by weight of the other ethylenically unsaturated monomer.