JPH0672214B2 - Method for producing back coat resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a backcoat resin. More specifically, when coating various base materials such as inorganic building materials, wood, and metal, by coating and processing the back surface of each base material in advance, various coatings can be easily formed at low temperature. The present invention relates to a method for producing a backcoat resin capable of forming a coating film capable of preventing a phenomenon in which a substrate is coated and then coated and is difficult to peel off when the coated object is stacked and stored.

(Problems to be Solved by Conventional Techniques and Inventions) Conventionally, when various base materials such as metal, wood, paper, plastic, inorganic building materials, etc. are coated in a factory (usually called line coating). Since the objects to be coated are coated and stored after being coated with a paint that uses acrylic resin, styrene-acrylic resin, vinyl acetate resin, urethane resin, etc. as the vehicle component, the objects to be coated adhere to each other and peel off. There is a problem that a so-called blocking phenomenon becomes difficult. This phenomenon becomes more noticeable when loading after heating and drying and before completely cooling.
When such a blocking phenomenon occurs, the coating film or the coating object is destroyed, and the original purpose of coating, such as protection of the coating object and improvement of aesthetics, can no longer be achieved. In order to prevent this blocking phenomenon, conventionally, a measure has been taken to coat the back surface of the base material before coating with a substance having releasability such as silicone resin or self-emulsifying polyolefin (eg, polyethylene) wax emulsion. Was there. However, the coating of these substances having releasability markedly reduces the adhesive force by the adhesive, and therefore cannot be used for applications where the releasable coating material is applied to, for example, a structure and the like. There is a drawback that the coating film surface is contaminated by the paint when the coated material is loaded.

Another method to prevent the blocking phenomenon is to put a synthetic paper such as a polyethylene sheet between the objects to be coated, but this is complicated in the process and the synthetic paper itself is unnecessary when used and is disposable. However, there is a problem in terms of cost.

(Technical Means for Solving Problems) The inventors of the present invention have conducted extensive studies in view of such a current situation, and as a result, prior to coating various base materials with a paint, By applying the emulsion resin to the back surface of each base material, it is possible to easily prevent the blocking phenomenon when a film is formed at a low temperature and the object to be coated is loaded, and moreover, when the object to be coated is adhered to the structure. The inventors have found that the adhesive strength is also excellent, and have completed the present invention.

That is, the present invention provides a polymerizable monomer (a) containing a carboxyl group in the molecule.
0.1 to 10% by weight, and (meth) acrylic acid ester, aromatic unsaturated monomer, unsaturated cyanide compound, hydroxyl group-containing unsaturated monomer,
90 to 99.9% by weight of a carboxyl group-free polymerizable monomer (b) selected from the group consisting of polyfunctional unsaturated monomers and glycidyl group-containing unsaturated monomers (provided that (( a) + (b) is 100% by weight.) When a back coat resin is produced by multi-stage emulsion polymerization of a polymerizable monomer component, the Tg of the first stage polymer component is 30 ° C. The Tg of the polymer component in the last step is 20 ℃
The present invention relates to a method for producing a backcoat resin, which is characterized below.

The polymerizable monomer (a) containing a carboxyl group in the molecule (hereinafter referred to as the monomer (a)) used in the present invention is particularly preferably a polymerizable monomer having a carboxyl group in the molecule. Without limitation, for example (meth) acrylic acid,
Unsaturated carboxylic acids such as crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl fumarate, monoethyl fumarate, monomethyl maleate and monoethyl maleate or derivatives thereof may be mentioned. Two or more kinds can be used. In the present invention, the monomer (a) is 0.1 to 10 in all polymerizable monomer components.
Used in the range of wt%. The amount of monomer (a) used is 0.1
If the amount is less than 10% by weight, the stability during multi-stage emulsion polymerization may be reduced, or the adhesion to various coated objects may be reduced. Conversely, if the amount is more than 10% by weight, the water resistance of the resulting coating film may be reduced. Both are not preferable because they decrease.

The carboxyl group-free polymerizable monomer (b) (hereinafter referred to as the monomer (b)) used in the present invention includes
One or more types are selected and used from the following monomer components. At this time, in consideration of the monomer (a), Tg described later
It is necessary to select so as to satisfy the specified conditions of. Specifically, (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate; styrene, α- Aromatic unsaturated monomers such as chlorostyrene and vinyltoluene; Unsaturated cyan compounds such as (meth) acrylononitrile; Hydroxyl group-containing unsaturated such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate Monomers; polyfunctional unsaturated monomers such as divinylbenzene and ethylene glycol di (meth) acrylate; glycidyl group-containing unsaturated monomers such as glycidyl (meth) acrylate and acrylglycidyl ether Can be one of these It can be used two or more. The monomer (b) is used in the range of 90 to 99.9% by weight based on the total polymerizable monomer components. Further, in the present invention, it is desirable that 30% by weight or more of the monomer (b) is a (meth) acrylic acid ester from the viewpoint of weather resistance.

The backcoat resin obtained by the production method of the present invention is obtained by multistage emulsion polymerization of the polymerizable monomer component consisting of the monomers (a) and (b) in an aqueous medium. At this time, the Tg of the first-stage polymer component is 30 ° C. or higher, preferably
It is required to be 45 ° C or higher and Tg of the polymer component in the last stage is 20 ° C or lower, preferably 0 ° C or lower. The multi-stage emulsion polymerization referred to here is such that, from the polymerizable monomer components, some components are selected so that the Tg of the polymer is 30 ° C. or higher, and some of these components are used in the first stage. Emulsion polymerization by a known emulsion polymerization method, in the presence of the resulting polymer component,
This is a method in which the second and subsequent emulsion polymerizations are successively carried out using the remaining monomer components. At this time, after the second step, the remaining monomer components used in the first step may be used in the total amount to perform the two-step polymerization, or may be appropriately divided into the three-step polymerization or more. Then, in the last stage, the Tg of the polymer component may be set to 20 ° C. or lower. The multistage emulsion polymerization is usually 2 to
A three-stage polymerization is used. Even if the polymerization is carried out in more stages than this, no particular improvement in the performance can be expected, and it only causes complication during the production. In the present invention, it is necessary that the Tg of each of the first-stage polymer component and the last-stage polymer component be as defined above. When the Tg of the polymer component of the first stage, that is, the polymer component forming the most central part (core) of the obtained emulsion copolymer is lower than 30 ° C, it becomes difficult to prevent the blocking phenomenon and the final stage When the Tg of the polymer component of, that is, the polymer component of the outermost portion (shell) of the emulsion copolymer exceeds 20 ° C, the film forming property of the coating material using this decreases, and a film is formed during the film formation. Both are not preferable because they require an auxiliary agent and require a high temperature for drying. Further, in obtaining the resin for back coat, the amount of the polymer component in the first step is preferably 20 to 90% by weight, more preferably 35 to 70% by weight in the copolymer, and the weight of the final step is The coalescence component can be present in the copolymer in an amount of preferably 10 to 80% by weight, more preferably 30 to 65% by weight. By setting the amounts of the first-stage polymer component and the last-stage polymer component within this range, both the blocking resistance and the film forming property of the coating film can be achieved at a high level.

In the present invention, examples of the polymerization initiator used in the multistage emulsion polymerization include known water-soluble or oil-soluble initiators such as ammonium persulfate, potassium persulfate, hydrogen peroxide, and butyl hydroperoxide. At this time, a redox initiator may be used by using sodium bisulfite, L-ascorbic acid or the like as a reducing agent. As the emulsifier, an anionic activator such as sodium lauryl sulfate and a nonionic activator such as polyoxyethylene alkyl ether are used, but in some cases, the polymerization can be performed in the absence of the emulsifier. In the present invention, a chain transfer agent such as lauryl methyl mercaptan may be used for the purpose of controlling the molecular weight during the polymerization. The back coat resin obtained by the method of the present invention may be neutralized with a basic compound as necessary. May be. Examples of the basic compound that can be used include ammonia, triethylamine, morpholine, sodium hydroxide and the like.

Further, if necessary, known additives such as film-forming aids, pigments, fillers, toners, wetting agents, antistatic agents, etc. may be blended with the backcoat resin obtained by the method of the present invention.

(Effects of the Invention) The backcoat resin obtained by the method of the present invention is
Since the Tg of the polymer component in the first stage is 30 ° C or higher and the Tg of the polymer component in the last stage is 20 ° C or lower, it is easy to form a film at low temperature A coating film having blocking resistance and excellent adhesiveness of the adhesive can be obtained.

By coating the back coat resin obtained by the method of the present invention on the back surface of the substrate in advance, an acrylic resin,
Styrene-acrylic resin, vinyl acetate resin, urethane resin and the like can prevent the blocking phenomenon when loading the coating material coated on the surface of the substrate with a coating material as a vehicle component,
Moreover, the object to be coated can be easily adhered to the structure. Therefore, the back coat resin obtained by the method of the present invention is a metal,
It is extremely useful in the field of line painting such as wood, paper, plastic, and inorganic building materials.

(Example) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. The parts in the examples are by weight unless otherwise specified.

Example 1 1 equipped with a stirrer, reflux condenser, dropping funnel, thermometer
After deionized water (500 parts) and sodium lauryl sulfate (8 parts) were charged in the separable flask (1), the temperature was raised to 70 ° C. with stirring while blowing nitrogen gas. Then 80 parts of methyl methacrylate, 80 parts of styrene, 36 parts of butyl acrylate,
Polymerizable monomer mixture (A) consisting of 4 parts of methacrylic acid
(Glass transition temperature of 60 ° C.) was used as the first step and was added dropwise uniformly over 1 hour.

At the same time, add 1 part of 10% ammonium persulfate aqueous solution at the same time.
It was dripped uniformly over time. After aging for 1 hour, the polymerizable monomer mixture (B) (glass transition temperature −8 ° C.) consisting of 80 parts of methyl methacrylate, 116 parts of butyl acrylate and 4 parts of methacrylic acid was used as the final role.
It was dripped uniformly over time. At the same time, 10 parts of a 10% ammonium persulfate aqueous solution was uniformly added dropwise over 1 hour. After that, aging was carried out for 1 hour. After cooling, 6.3 parts of 25% aqueous ammonia was added to neutralize. The backcoat resin (1) thus obtained had a nonvolatile content of 43.5% and a pH of
9.0, viscosity 95cps (B type viscometer, No.1 rotor, 30rpm, 2
5 ° C) and the minimum film formation temperature of 25 ° C. To 100 parts of the obtained resin (1) for back coat, the film-forming auxiliary CS
-12 (manufactured by Chisso Co., Ltd.) was added and well stirred to homogenize. Backcoat resin (1) containing this film-forming aid is sprayed onto two flexible boards at 100 g / c
After applying m ² for 10 minutes in a hot air dryer at 50 ° C (air velocity 1 m /
S) After drying, the back surface was processed. Spray 200g of paint (1) with the following composition on the surface of this flexible board
/ cm ^{2 and} apply in a hot air dryer at 100 ° C for 5 minutes (wind speed 1m /
S) After drying, when the surface temperature reaches 70 ° C, the coating surface of the backcoat resin (1) and the coating surface of the coating material (1) are overlaid and a pressure of 5 kg / cm ² is applied with a press to 70 ° C. After adding at 30 ° C. for 30 minutes, it was peeled off and a blocking phenomenon prevention test was conducted.

The two flexible boards pressed in this way were peeled off resistancelessly after the completion of pressing, and the painted surface was not damaged at all. Further, the coating film performance test results of the test pieces coated under the same conditions as used in the above test are as shown in Table 2.

Example 2 After the same separable flask as used in Example 1 was charged with 500 parts of deionized water, the temperature was raised to 75 ° C. with stirring while blowing nitrogen gas. After that, 120 parts of styrene, 20 parts of acrylonitrile, 58 parts of ethyl acrylate, 2 parts of itaconic acid (glass transition temperature of the above polymerized monomer mixture of 53 ° C.), Rebenol WZ (manufactured by Kao Corporation) were adjusted beforehand. , 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate) 6 parts, 4 parts of 25% aqueous solution of Nonipol 200 (polyoxyethylene nonylphenyl ether manufactured by Sanyo Kasei Co., Ltd.), 1 part of ammonium persulfate,
Pre-emulsion mixture (C) consisting of 69 parts of deionized water
Was used as the first step and was uniformly added dropwise over 1 hour. During this period, 5 parts of a 10% aqueous sodium hydrogen sulfite solution was added evenly every 10 minutes. After aging for 1 hour, 64 parts of styrene, 35 parts of butyl acrylate, 1 part of acrylic acid (Tg of the above polymerizable monomer mixture: 25 ° C), Rebenol WZ
A pre-emulsion mixture (D) consisting of 3 parts, 2 parts of 25% aqueous solution Nonipol 200, 0.5 parts of ammonium persulfate and 34.5 parts of deionized water was uniformly added dropwise over 30 minutes as the second step. During this time, 10% sodium bisulfite aqueous solution 2.5
Parts were added evenly every 10 minutes. After aging for 30 minutes, 50 parts of styrene, 48 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid (glass transition temperature of the above polymerizable monomer mixture-7 ° C), 3 parts of rebenol WZ, 25% aqueous solution of nonipol. 200 2 parts, ammonium persulfate 0.5
Part, and pre-emulsion mixture (E) consisting of 34.5 parts of deionized water as the last role, were added dropwise uniformly over 30 minutes. During this period, 2.5 parts of a 10% sodium hydrogen sulfite aqueous solution was added evenly every 10 minutes. Then, it was aged for 60 minutes. After cooling, 6 parts of 25% aqueous ammonia was added for neutralization. The backcoat resin (2) thus obtained had a nonvolatile content of 42.2%, a pH of 9.0, and a viscosity of 250 cps (B-type viscometer, No.
2 rotors, 30 rpm, 25 ℃), the minimum film forming temperature of 23 ℃ is a special value.

A blocking phenomenon prevention test was conducted in the same manner as in Example 1 using the backcoat resin (2), and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
The painted surface was not damaged at all. The coating film performance test results were as shown in Table 2.

Example 3 The same separable flask as in Example 1 was charged with deionized water 400.
After charging the part, while blowing nitrogen gas,
The temperature was raised to ° C. After that, the first-stage monomer component (Tg 89 ° C) shown in Table 1, 6 parts of Rebenol WZ, 4 parts of 25% aqueous solution of Nonipol 200, and 50 parts of deionized water were prepared beforehand. 26 parts of the first stage pre-emulsion mixture consisting of was added to a separable flask.
To this, 40 parts of a 5% aqueous solution of potassium persulfate was added, polymerization was carried out for 10 minutes, and then the remaining pre-emulsion was uniformly added dropwise over 1 hour. During this period, 5 parts of a 10% aqueous sodium hydrogen sulfite solution was added evenly every 10 minutes. After aging for 1 hour, 6 parts of last-minute monomer component (Tg-24 ° C), Rebenol WZ, 4 parts of 25% aqueous nonipol 200, and 50 parts of deionized water are shown. The final role pre-emulsion mixture consisting of was added dropwise uniformly over 1 hour. During this period, 5 parts of a 10% aqueous sodium hydrogen sulfite solution was added evenly every 10 minutes. Then, it was aged for 1 hour. After cooling, 4 parts of 25% aqueous ammonia was added to neutralize. The backcoat resin (3) thus obtained had a non-volatile content of 41.5%, a pH of 9.5, a viscosity of 100 cps (B-type viscometer, No. 2 rotor, 30 rpm, 25 ° C.), and a minimum film formation temperature of 1
The special value at 9 ° C is shown.

Using this backcoat resin (3), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 4 The same separable flask as in Example 1 was charged with deionized water 400.
After charging the parts, while blowing nitrogen gas,
The temperature was raised to ° C. After that, the first-stage monomer component (Tg106 ° C) shown in Table 1 which had been adjusted in advance, 25
% Sodium dodecylbenzenesulfonate solution 8.0
Parts and 5.2 parts of the first stage pre-emulsion mixture consisting of 40 parts deionized water were added to the separable flask.
20 parts of a 5% aqueous solution of 2,2'-azobis (2-amidinopropane) dihydrochloride was added thereto, polymerization was carried out for 20 minutes, and the remaining pre-emulsion was uniformly added dropwise over 1 hour. After aging for 1 hour, the final stage monomer component (Tg-30 ° C) shown in Table 1, 12.0 parts of 25% sodium dodecylbenzenesulfonate aqueous solution, deionized water
The final stage pre-emulsion mixture consisting of 60 parts was uniformly added dropwise over 1 hour. Then, it was aged for 1 hour. After cooling, 2 parts of 25% aqueous ammonia was added to neutralize. Resin for back coat thus obtained (4)
Is non-volatile content 42.9%, pH 9.6, viscosity 50cps (B type viscometer,
No. 1 rotor, 30 rpm, 25 ° C), minimum film forming temperature 20 ° C.

Using this backcoat resin (4), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 5 The same operation as in Example 3 was repeated except that the type and amount of the polymerizable monomer in Example 3 were changed as shown in Table 1, and after cooling, 7 parts of 25% aqueous ammonia was added. And neutralized. The backcoat resin (5) thus obtained is
Nonvolatile content 41.4%, pH 9.6, viscosity 150cps (B type viscometer, No.
2 rotors, 30 rpm, 25 ℃), the minimum film formation temperature was 18 ℃.

Using this backcoat resin (5), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressurization was completed, the flexible boards peeled off without resistance, and the painted surface was not damaged at all. The results of the coating property test were as shown in Table 2.

Example 6 A separable flask similar to that in Example 1 was charged with 400 deionized water.
After charging the part, while blowing nitrogen gas,
The temperature was raised to ° C. After that, the first-stage monomer component (Tg85 ° C) shown in Table 1, which was adjusted in advance, 3.6 parts of Rebenol WZ, 2.4 parts of 25% aqueous solution of Nonipol 200, and 30 parts of deionized water 26 parts of the first stage pre-emulsion mixture consisting of was added to a separable flask. To this, 40 parts of a 5% aqueous solution of potassium persulfate was added, polymerization was carried out for 10 minutes, and then the remaining pre-emulsion was uniformly added dropwise over 1 hour. During this period, 3 parts of a 10% aqueous sodium hydrogen sulfite solution was added evenly every 10 minutes. Then, after aging for 1 hour, the final stage monomer component (Tg3 ° C) shown in Table 1, 8.4 parts of Rebenol WZ, 5.6 parts of 25% aqueous solution of Nonipol 200, and 70 parts of deionized water were used. The final-stage pre-emulsion mixture was uniformly added dropwise over 1 hour. During this period, 7 parts of a 10% sodium hydrogen sulfite aqueous solution was added evenly every 10 minutes. Then, it was aged for 1 hour. After cooling, 7 parts of 25% aqueous ammonia was added for neutralization. The backcoat resin (6) thus obtained had a non-volatile content of 41.3%, a pH of 9.5, a viscosity of 100 cps (B-type viscometer, No. 2 rotor, 30 rpm, 25 ° C.), and a minimum film formation temperature of 3
The special value at 2 ° C is shown.

Using this backcoat resin (6), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 7 The same separable flask as in Example 1 was charged with deionized water 400.
After charging the parts, while blowing nitrogen gas,
The temperature was raised to ° C. After that, the first-stage monomer component (Tg106 ° C) shown in Table 1 which had been adjusted in advance, 25
% Sodium dodecylbenzenesulfonate solution 10.0
Parts and 5.2 parts of the first stage pre-emulsion mixture consisting of 50 parts deionized water were added to the separable flask.
20 parts of a 5% aqueous solution of 2,2'-azobis (2-amidinopropane) dihydrochloride was added thereto, polymerization was carried out for 20 minutes, and the remaining pre-emulsion was uniformly added dropwise over 1 hour. Then, after aging for 1 hour, the final stage monomer component (Tg-30 ° C) shown in Table 1, 10.0 parts of 25% sodium dodecylbenzenesulfonate aqueous solution, deionized water
The final stage pre-emulsion mixture consisting of 50 parts was uniformly added dropwise over 1 hour. Then, it was aged for 1 hour. After cooling, 3 parts of 25% aqueous ammonia was added to neutralize. Resin for back coat thus obtained (7)
Is non-volatile content 42.7%, pH 9.5, viscosity 50cps (B type viscometer,
No.1 rotor, 30 rpm, 25 ° C), and the minimum film forming temperature of 30 ° C are the special values.

Using this back coat resin (7), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 8 The same operation as in Example 7 was repeated except that the type and amount of the polymerizable monomer in Example 7 were changed as shown in Table 1. The backcoat resin (8) thus obtained has a non-volatile content of 42.6%, a pH of 9.4, a viscosity of 50 cps (B-type viscometer, No. 1 rotor, 30 rpm, 25 ° C), and a minimum film-forming temperature of 28 ° C. showed that.

Using this back coat resin (8), a blocking prevention test was conducted in the same manner as in Example 1, and as a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 9 The same operation as in Example 3 was repeated except that the type and amount of the polymerizable monomer in Example 3 were changed as shown in Table 1, and after cooling, 5 parts of 25% ammonia water was added. Then, neutralization was performed. Resin for back coat thus obtained (9)
Is non-volatile content 41.1%, pH 9.0, viscosity 100cps (B type viscometer, No.2 rotor, 30rpm, 25 ℃), minimum film formation temperature 24 ℃
The special value of was shown.

Using this back coat resin (9), a blocking prevention test was conducted in the same manner as in Example 1. As a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Example 10 The same operation as in Example 3 was repeated except that the type and amount of the polymerizable monomer in Example 3 were changed as shown in Table 1, and after cooling, 4.5 parts of 25% ammonia water was added. Then, neutralization was performed. Backcoat-like resin thus obtained (10)
Is non-volatile content 41.3%, pH 8.9, viscosity 150cps (B type viscometer, No.2 rotor, 30rpm, 25 ℃), minimum film formation temperature 22 ℃
The special value of was shown.

Using this back coat resin (10), a blocking prevention test was conducted in the same manner as in Example 1. As a result, 2
After the pressure is applied, the flexible boards are peeled off without resistance,
There was no damage on the painted surface. The results of the coating film performance test were as shown in Table 2.

Comparative Example 1 In Example 1, the polymerizable monomer mixture (B) was used in the first stage and the polymerizable monomer mixture (A) was used in the last stage.
The same operation as in Example 1 was repeated except that was used to obtain a comparative resin (1). The characteristic values of the obtained comparative resin (1) were a non-volatile content of 43.3%, a pH of 9.0, a viscosity of 110 cps, and a minimum film formation temperature of 55 ° C. C for 100 parts of this comparative resin (1)
8 parts of S-12 was added, and well stirred to homogenize. Using a test piece coated with this in the same manner as in Example 1, a blocking prevention test and a coating film performance test were conducted. As a result of the blocking prevention test, a blocking phenomenon occurred and the two flexible boards could not be separated. Also,
The coating film performance test results were as shown in Table 2.

Comparative Example 2 In Example 2, only the pre-emulsion mixture (C) used in the first stage without performing the second-stage and last-stage polymerization of the pre-emulsion mixture with (D) and (E) (this At that time, the same operation as in Example 2 was repeated except that the pre-emulsion mixture (C) used in Example 2 was polymerized.) To obtain a comparative resin (2). This comparative resin (2) has a nonvolatile content of 42.3%, a pH of 9.0, and a viscosity of 180 cp.
c, the characteristic value of the minimum film formation temperature of 83 ° C was shown. When this flexible resin (2) was used to perform the back surface treatment of the flexible board in the same manner as in Example 1, no film was formed.

Comparative Example 3 The same operation as in Example 1 was repeated except that a commercially available self-emulsifying polyethylene wax emulsion was used to treat the back surface of the flexible board in Example 1, and a blocking phenomenon prevention test was conducted. Although the flexible board of No. 1 peeled off without resistance after the pressurization, the coating surface of the paint (1) was significantly contaminated. The results of the coating film performance test are as shown in Table 2, which shows that the adhesiveness is poor.

Claims (2)

[Claims] 1. A polymerizable monomer (a) having a carboxyl group in the molecule (0.1 to 10% by weight), a (meth) acrylic acid ester, an aromatic unsaturated monomer, an unsaturated cyanide compound and a hydroxyl group. Group-containing unsaturated monomer,
90 to 99.9% by weight of a carboxyl group-free polymerizable monomer (b) selected from the group consisting of polyfunctional unsaturated monomers and glycidyl group-containing unsaturated monomers (provided that (( a) + (b) is 100% by weight.) When a back coat resin is produced by multi-stage emulsion polymerization of a polymerizable monomer component, the Tg of the first stage polymer component is 30 ° C. The Tg of the polymer component in the last step is 20 ℃
A method for producing a resin for a back coat, comprising the following: 2. A multi-stage emulsion polymerization wherein the polymer component in the first stage is in the range of 20 to 90% by weight and the polymer component in the last stage is in the range of 10 to 80% by weight. The method for producing a backcoat resin according to item 1.