JP2007077319A - Method for producing aqueous resin composition and aqueous resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous resin composition which is useful as a vehicle for various coatings, inks, and the like, is excellent in coating suitability, and can form good coating films. <P>SOLUTION: This method for producing the aqueous resin composition is characterized by comprising two polymerization steps which comprise emulsion-polymerizing 90 to 30 mass% of a monomer mixture (A) containing 1 to 30 mass% of a carboxyl group-containing monomer (a) and 1 to 60 mass% of an aromatic monomer (b), neutralizing all or a part of the carboxyl groups of the obtained emulsion polymer with a basic substance, and then emulsion-polymerizing 10 to 70 mass% of at least one monomer (B) except the above-mentioned monomer (a). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an aqueous resin composition and an aqueous resin composition. More specifically, it has excellent polymerization stability, storage stability, film-forming properties, glossiness, water resistance, heat resistance, oil resistance, blocking resistance, etc., and various paper, film, metal, glass, wood, leather, etc. The present invention relates to a method for producing an aqueous resin composition, which is excellent in coating suitability and can be used as a coating material for a substrate and as an ink vehicle, and forms a good coating film (coating film), and an aqueous resin composition. In the present invention, “resin” and “polymer” are synonymous.

  As a general emulsion polymerization method, there is a method of polymerizing a monomer using a surfactant and a polymerization initiator in an aqueous medium. The aqueous resin composition produced by this method has a high molecular weight of the resin, and when used as a coating agent, a coating film having excellent physical properties can be obtained. However, there is a problem in applications where glossiness is required for the coating film. In order to improve the film-forming property of the resin composition, an emulsion polymerization method is known in which a water-soluble resin is used as a polymer emulsifier at the time of monomer polymerization. The aqueous resin composition obtained by this method has good film formability because of the presence of the water-soluble resin in the composition, and a glossy coating film can be obtained. However, since the coating film contains a water-soluble resin, there is a problem in water resistance.

  In order to solve this problem, a method of reducing the amount of the acid group-containing monomer used when obtaining the water-soluble resin can be considered. There is a tendency that the stability of the polymerization solution is deteriorated and the storage stability of the obtained aqueous resin composition is also deteriorated. Various water-soluble resins are used as the water-soluble polymer emulsifier as described above, and various methods for producing the water-soluble polymer emulsifier are also considered. For example, solution polymerization, bulk polymerization, emulsion polymerization, etc. The method by is well known.

  Patent Document 1 discloses a method for obtaining a primary polymer by solution polymerization or bulk polymerization. However, this solution polymerization requires a solvent-removing step after completion of the polymerization, and there are problems in the efficiency and economy in the production of the aqueous resin composition. In the bulk polymerization, the resin obtained by the polymerization is used. In order to use as a water-soluble polymer emulsifier, a step of dissolving the resin obtained by bulk polymerization in water is necessary, and there is a problem in productivity and efficiency in the production of an aqueous resin composition.

  On the other hand, the method for producing a water-soluble polymer emulsifier by emulsion polymerization is an efficient method because the obtained polymerization solution can be continuously used as a polymerization reaction medium in the next step. Patent Document 2 discloses a method in which a polymer emulsifier obtained by primary polymerization is subjected to secondary emulsion polymerization and then neutralized with a basic substance. In this method, since the monomer for the secondary polymer is polymerized in the primary polymerization solution, the polymerization reaction is unstable, and aggregates of polymer particles are easily generated in the obtained aqueous resin composition. Furthermore, in this method, an aqueous resin composition containing polymer particles having a high solid content and a small particle diameter cannot be obtained, and the coating suitability of the composition and the coating film comprising the resin composition are glossy. There is a problem.

  Patent Document 3 discloses an aqueous resin composition in which an aromatic unsaturated monomer such as styrene is not used as a raw material monomer for a polymer emulsifier that is a primary polymer. Since no aromatic unsaturated monomer is used as the raw material monomer, sufficient water resistance and heat resistance cannot be obtained for the coating film comprising the finally obtained aqueous resin composition. In Patent Document 4, there is a method in which it is essential to use an aromatic unsaturated monomer as a raw material monomer of a polymer emulsifier which is a primary polymer, and further to use a hydrophilic organic solvent as a polymerization medium. It is disclosed. Since a hydrophilic organic solvent is used in this method, when the obtained aqueous resin composition is used as a coating material for information-related paper such as thermal paper and inkjet paper, it adversely affects the thermal layer and ink receiving layer of the paper. There is a problem of affecting.

JP 2002-256209 A Japanese Patent Publication No. 6-81765 JP 2003-268020 A JP 2001-323034 A

  Therefore, the object of the present invention is excellent in stability during polymerization, storage stability, film formability, glossiness, water resistance, heat resistance, oil resistance, blocking resistance, and the like, and is paper, film, metal, glass, wood, leather. It is useful as a coating agent for various substrates such as, and as an ink vehicle, and is excellent in coating suitability and can provide an aqueous resin composition capable of forming a good coating film.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a two-stage polymerization method using a monomer mixture containing an aromatic monomer in the first stage of emulsion polymerization. By neutralizing the emulsion, the neutralized product functions as a polymer emulsifier, and an aqueous resin composition that can achieve the object of the present invention can be obtained without using an organic solvent or the like as a polymerization medium. As a result, the present invention was reached.

That is, the present invention has the following configuration.
1. In the presence of at least water, a chain transfer agent, a surfactant and a polymerization initiator, 1 to 30% by mass of the carboxyl group-containing monomer (a) and 1 to 60% by mass of the aromatic monomer (b) The monomer mixture (A) containing 90 to 30% by mass is subjected to emulsion polymerization (first stage polymerization), and after neutralizing part or all of the carboxyl groups of the obtained emulsion polymer with a basic substance, at least Two stages of emulsion polymerization (second stage polymerization) of 10 to 70% by mass of at least one monomer (B) other than the monomer (a) in the presence of water, a surfactant and a polymerization initiator A method for producing an aqueous resin composition comprising polymerization (in the above, the mass% of the monomer is a ratio when the total mass of all monomers is 100 mass%).

2. In the above 1, the monomer mixture (A) contains a copolymerizable monomer (c) other than the monomers (a) and (b) in a proportion of 1 to 50% by mass of the total monomers. The manufacturing method as described.
3. The weight average molecular weight of the emulsion polymer obtained by the first stage emulsion polymerization is 2,000 to 20,000, and the pH of the emulsion polymerization solution after neutralization is 5.0 to 9.0, And the manufacturing method of said 1 or 2 from which the light absorbency after neutralization becomes a ratio of 100 to 20% with respect to the light absorbency before neutralization.

4). 4. The production method according to any one of 1 to 3, wherein the surfactant is an anionic surfactant having no polymerizable unsaturated bond.
5. An aqueous resin composition obtained by the production method described in 1 above.
6). 6. The aqueous resin composition as described in 5 above, further comprising a polyvalent metal complex salt.

  According to the present invention, the coating film obtained by coating various substrates is excellent in film formability, glossiness, water resistance, heat resistance, oil resistance, blocking resistance, etc. An aqueous resin composition useful as an ink vehicle is also provided.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention.
The manufacturing method of the aqueous resin composition of the present invention is a manufacturing method in which emulsion polymerization is performed in two stages. As the first stage emulsion polymerization, 1-30 mass% carboxyl group of all monomers used in the first stage and the second stage in the presence of at least water, a chain transfer agent, a surfactant and a polymerization initiator. Monomer mixture (A) 90 to 90 comprising a monomer (a) containing and an aromatic monomer (b) of 1 to 60% by mass of the total monomers used in the first and second stages 30% by mass is emulsion polymerized. In this emulsion polymerization, it is not essential to polymerize all the monomers, and the process may proceed to the next step before all the monomers are polymerized (pre-polymerized state).

  Next, after the completion of the first stage polymerization, the produced polymerization solution is neutralized with a basic substance so that the pH is 5.0 to 9.0 with a basic substance in part or all of the carboxyl groups of the polymer. . Subsequently, in the neutralized polymerization solution as the second stage emulsion polymerization, at least one monomer (B) other than at least water, a surfactant, and the monomer (a) is 10 to 70% by mass. Is added dropwise together with a polymerization initiator to carry out emulsion polymerization. The first stage emulsion polymerization temperature is 80 to 90 ° C., and the second stage polymerization can be carried out continuously without lowering the temperature.

  Examples of the carboxyl group-containing monomer (a) used in the present invention include polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid, and anhydrides thereof. And at least one selected from these groups can be used. The amount of the monomer (a) used is an amount that occupies 1 to 30% by mass in all monomers (the total of the monomer mixture (A) and the monomer (B) is 100% by mass). It is necessary to be. When the amount of the monomer (a) used is less than 1% by mass, the stability of the polymerization liquid at the second stage of polymerization is poor, and aggregates of polymer particles are generated in the resulting aqueous resin composition. On the other hand, when the usage-amount of monomer (a) is more than 30 mass%, the water resistance of the coating film which consists of an aqueous resin composition finally obtained falls.

  Examples of the aromatic monomer (b) used in the present invention include styrene, α-methylstyrene, p-methylstyrene, t-methylstyrene, chlorostyrene, benzyl acrylate, vinyltoluene, and the like. At least one selected from the group can be used. The amount of the monomer (b) used is an amount that occupies 1 to 60% by mass in all monomers (the total of the monomer mixture (A) and the monomer (B) is 100% by mass). It is necessary to be. When the usage-amount of a monomer (b) is less than 1 mass%, the water resistance of the coating film which consists of an aqueous resin composition finally obtained falls. On the other hand, when the usage-amount of a monomer (b) exceeds 60 mass%, the film formability of the coating film which consists of an aqueous resin composition finally obtained falls.

  In the present invention, the monomer mixture (A) may further contain another copolymerizable monomer (c) as necessary. Examples of the monomer (c) include (meth) acrylic acid alkyl esters [for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc.], hydroxyl group-containing (meth) acrylic acid esters [for example, 2-hydroxyethyl ( Meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycerol (meth) monoacrylate, etc.], (meth) acrylamides [e.g. (meth) acrylamide, N-methyl (meth) acrylamide, Nn-butyl (meth) ) Acrylamide, Ni-propi (Meth) acrylamide, Nt-butyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, N-methylol (meth) acrylamide, etc.], vinyl cyanides [for example, (meta ) Acrylonitrile and the like] and vinyl esters [for example, vinyl acetate and the like], and at least one selected from these groups can be used. The amount used is an amount that occupies 1 to 50% by mass in all monomers (when the monomer mixture (A) and the monomer (B) are 100% by mass). When the usage-amount of a monomer (c) exceeds 50 mass%, the water resistance of the coating film which consists of an aqueous resin composition finally obtained falls.

  The chain transfer agent used in the present invention is necessary for adjusting the molecular weight of the emulsion polymer obtained in the first stage. The molecular weight of the emulsion polymer affects the stability of the polymerization solution, the coatability of the finally obtained aqueous resin composition, and the performance of the coating film comprising the composition. The molecular weight is preferably a weight average molecular weight of 2,000 to 20,000, and more preferably 5,000 to 15,000.

  Examples of the chain transfer agent to be used include octyl thioglycolate, methoxybutyl thioglycolate, octyl mercaptopropionate, methoxybutyl mercaptopropionate, mercaptans such as stearyl mercaptan and lauryl mercaptan, α-methylstyrene dimer, and the like. And at least one selected from these groups can be used. It is preferable that the usage-amount is 0.5-5 mass parts with respect to 100 mass parts of all the monomers. When used within this range, a polymer having the above molecular weight can be obtained.

  Any surfactant can be used as the surfactant used in the emulsion polymerization in the first stage in the present invention as long as it is an anionic surfactant. Specifically, for example, sodium oleate, sodium lauryl sulfate, alkyl benzene sulfonate, alkyl lauryl sulfate alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkane sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene Examples include sulfonic acid formalin condensate, polyoxyethylene alkyl phenyl ether sulfate ester salt, polyoxyethylene alkyl sulfate ester salt, and the like, and at least one selected from these groups can be used. The surfactant preferably does not contain a reactive surfactant having one or more radically polymerizable unsaturated groups in the molecule. The amount of the surfactant used at the first stage of the emulsion polymerization is preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of all monomers. When the amount used is less than 0.2 parts by mass, the stability of the polymerization solution during emulsion polymerization is poor, and aggregates of polymer particles tend to occur in the finally obtained aqueous resin composition. On the other hand, when the usage-amount is more than 5 mass parts, the water resistance of the coating film which consists of an aqueous resin composition finally obtained falls.

  The basic substance used in the present invention is a substance that neutralizes the carboxyl group of the emulsion polymer obtained in the first stage so that the emulsion polymer is dissolved or partly hydrophilic. . Since the neutralized emulsion polymer acts as one kind of polymer emulsifier having a hydrophilic part and a hydrophobic part, by using the emulsion polymerization liquid, it is possible to The polymerization solution is stabilized. Examples of the basic substance to be used include alkylamines such as ammonia, triethylamine, trimethylamine and butylamine, alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol, and morpholine. The amount used is preferably such that the pH of the first stage emulsion polymerization solution is 5.0 to 9.0. When the pH is in the range of 5.0 to 9.0, the stability of the polymerization solution during the second stage emulsion polymerization is good.

Furthermore, the absorbance of the emulsion polymerization solution neutralized with the basic substance is preferably 100 to 20% (absorbance ratio) with respect to the absorbance of the emulsion polymerization solution before neutralization. When the absorbance ratio is lower than 20%, the water resistance of the coating film composed of the finally obtained aqueous resin composition is lowered. Even if the emulsion polymerization liquid obtained in the first stage is not completely transparent due to neutralization, and the particulate polymerization remains in the emulsion polymerization liquid, the absorbance ratio is within the above range. The neutralized polymer described above has a sufficient function as a polymer emulsifier in the second stage polymerization, and has no effect on the stability of the polymerization solution during the second stage emulsion polymerization. A composition can be obtained. The absorbance ratio is determined from the following formula.
Absorbance ratio (%) = first stage emulsion polymerization liquid (after neutralization with aqueous ammonia) / first stage emulsion polymerization liquid (before neutralization with aqueous ammonia) × 100

  As the monomer (B) used in the emulsion polymerization of the second stage of the present invention, monomers used for the emulsion polymerization of the first stage other than the carboxyl group-containing monomer (a) (monomer ( b) and (c)) can be used. The mass ratio of the monomer mixture (A) used for the first stage emulsion polymerization and the monomer (B) used for the second stage emulsion polymerization is A: B = 90: 10 to 30:70. It is necessary. When the usage-amount of the monomer mixture (A) used for the emulsion polymerization of a 1st step exceeds 90 mass%, the water resistance of the coating film which consists of an aqueous resin composition finally obtained will fall. On the other hand, when the amount of the monomer mixture (A) used is less than 30% by mass, the stability of the emulsion polymerization solution in the second stage is deteriorated, and the polymer particles are aggregated in the finally obtained aqueous resin composition. It becomes easy to produce a thing, and the heat resistance of the coating film which consists of this aqueous resin composition also falls.

  As the surfactant used in the second stage emulsion polymerization of the present invention, the same surfactant as that used in the first stage emulsion polymerization can be used. The amount used is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of all monomers. This surfactant only needs to have an amount capable of stably emulsifying the monomer emulsion during the second stage of emulsion polymerization. When the amount used is less than 0.1 part by mass, the stability of the polymerization solution during the second stage polymerization is poor, and aggregates of polymer particles tend to be formed in the finally obtained aqueous resin composition. When the usage-amount is more than 5 mass parts, the water resistance of the coating film which consists of an aqueous resin composition falls.

  The polymerization initiator used in the present invention may be a generally used radical polymerization initiator. Radical polymerization initiators are those that generate radicals by heat or reducing substances to cause addition polymerization of polymerizable monomers. Water-soluble or oil-soluble persulfates, peroxides, azobis compounds, etc. Can be mentioned. Specifically, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, 2,2-azobisisobutyronitrile, 2,2-azobis ( 2-diaminopropane) hydrochloride, 2,2-azobis (2,4-dimethylvaleronyl), and the like, preferably a water-soluble polymerization initiator. When acceleration of the polymerization rate or a low temperature reaction is desired, a reducing agent such as sodium bisulfite, ferrous chloride, ascorbic acid, formaldehyde sulfooxylate salt or the like can be used in combination with the radical polymerization initiator.

  The usage-amount of a polymerization initiator is 0.02-3 mass parts normally with respect to 100 mass parts of all the monomers. Preferably it is 0.05-1 mass part.

  In the present invention, a water-soluble resin composition obtained as described above can be mixed with a polyvalent metal complex salt to further improve the water resistance and heat resistance of a coating film comprising the aqueous resin composition. The polyvalent metal complex salt is an aqueous solution or aqueous dispersion composed of a polyvalent metal compound and a volatile complexing agent, and even when blended in an aqueous resin composition, resin gelation and generation of resin particle aggregates are observed. In addition, the storage stability of the aqueous resin composition containing the polyvalent metal complex salt is good. The aqueous resin composition is mixed with an aqueous solution or aqueous dispersion of the above polyvalent metal complex salt, applied to a substrate, and dried to evaporate the volatile complexing agent. A metal in the valent metal complex salt is crosslinked to obtain a tough coating film, and a coating film having excellent water resistance and heat resistance can be obtained. Therefore, the polyvalent metal compound is preferably a divalent or higher metal compound, and examples thereof include compounds of metals such as calcium, magnesium, zinc, aluminum, zirconium, and titanium. Examples of the volatile complexing agent include amines and ammonia. Among them, ammonia is preferable. In particular, the polyvalent metal complex salt is used as an ammonium complex of a metal salt containing ammonia. Points such as the stability of an aqueous resin composition containing the polyvalent metal complex salt and the water resistance and heat resistance of a metal-crosslinked coating film are used. Therefore, an ammonium complex salt of zinc or zirconium carbonate is more effective, and can be selected from zirconium carbonate ammonium complex and zinc carbonate ammonium complex.

  For example, an aqueous zinc carbonate carbonate solution is prepared as follows. A reaction vessel equipped with a stirrer is charged with 60 parts by mass of deionized water, 35 parts by mass of zinc oxide, and 40 parts by mass of ammonium bicarbonate, and 55 parts of ammonia water having a concentration of 25% by mass is added and reacted. The obtained aqueous solution of zinc ammonium carbonate is 18.2% by mass in terms of zinc oxide (active ingredient).

  The amount of the polyvalent metal complex salt used is preferably 1 to 15 parts by mass of the active ingredient of the polyvalent metal complex salt, more preferably 5 to 100 parts by mass of the solid content of the aqueous resin composition. 15 parts by mass. If the usage-amount is in the range of 1-15 mass parts, the coating film which has higher heat resistance is obtained. The aqueous resin composition containing the polyvalent metal complex salt as described above is used in applications requiring heat resistance such as OP (overprint) varnish press coating agent, embossing OP varnish, thermal paper top protective coating agent, etc. A great effect can be obtained.

  The aqueous resin composition of the present invention can be used for applications such as OP varnish, paint varnish, and ink vehicle. The OP varnish, paint, and ink obtained using the aqueous resin composition of the present invention have good storage stability and film formability, excellent coating suitability, glossiness, water resistance, heat resistance, oil resistance, A coating film with good blocking resistance is obtained.

  Furthermore, the water-based resin composition of the present invention may contain a colorant such as a pigment or dye, a filler, a water-soluble resin such as fine powder silica, colloidal silica, alumina sol, polypyrrolidone or polyvinyl alcohol, water-soluble or water as necessary. Dispersible polyester resin, urethane resin, antifoaming agent, leveling agent, lubricant, resins (for example, petroleum resin, rosin-based natural resin, etc.), preservative, film-forming agent, etc., within the range not impairing the effects of the present invention Can be blended.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified.

[Example 1]
In a reaction vessel equipped with a thermometer, a dropping funnel and a reflux condenser, and replaced with nitrogen gas, 75.3 parts of ion-exchanged water and 1 part of a surfactant (alkylbenzene sulfonate, Newlex R, manufactured by NOF Corporation) (Solid content 0.5 part) and the temperature is raised. When the internal temperature was raised to 80 ° C., 3 parts of 10% ammonium persulfate was added, and 2 parts of α-methylstyrene, 26 parts of methyl methacrylate, 3 parts of methacrylic acid and 1.5 parts of lauryl mercaptan were immediately prepared. The mixture consisting of is added dropwise over 1.5 hours. After further polymerization for 1 hour, 2 parts of 25% aqueous ammonia was added to obtain a first stage emulsion polymerization liquid.

  Subsequently, 33.3 parts of ion-exchanged water prepared in advance, 11 parts of styrene, 11 parts of methyl methacrylate, 47 parts of butyl acrylate and a surfactant (polyoxyethylene alkylphenyl ether sulfate ester, Latemul E-118B, Kao Corporation) (Manufactured) A monomer emulsion consisting of 1.2 parts (solid content: 0.3 part) was used as the second stage monomer (mixture), and the monomer (mixture) and 6 parts of 5% ammonium persulfate. Are simultaneously dropped into the first stage polymerization solution over 1.5 hours. The polymerization is further carried out at a reaction temperature of 80 ° C. for 2 hours. After cooling to room temperature, the concentration was adjusted with water and 25% aqueous ammonia to obtain an aqueous resin composition having a solid content of 45%, a viscosity of 1,000 mPa · s / 30 ° C., and a pH of 8.3.

  The weight average molecular weight of the first stage emulsion polymer of the obtained aqueous resin composition is 15,000, the pH is 8.5, and the absorbance of the first stage emulsion polymer solution (before neutralization with ammonia water) is The absorbance after neutralization with aqueous ammonia was 0.47, and the absorbance ratio was 42%. Furthermore, the stability of the polymerization solution during polymerization, the storage stability of the aqueous resin composition, and the film formability are good, the coating property of the water-soluble resin composition is good, and the gloss of the formed coating film The water resistance, water resistance, heat resistance, oil resistance, and blocking resistance were also good.

[Examples 2 to 5 and Examples 7 to 9]
Polymerization was carried out in the same manner as in Example 1 except that the monomer compositions in the first stage and the second stage shown in Table 1-1 and Table 1-2 were changed to obtain aqueous resin compositions, respectively. The results are shown in Tables 1-4 and 1-5. All the test items were good.

[Example 6]
In Example 6, 8 parts of the polyvalent metal complex salt as an active ingredient is blended with 100 parts of the solid content of the aqueous resin composition obtained in Example 5. The heat resistance of the coating film made of the obtained composition was greatly improved. All other test items were good. The results are shown in Table 1-5.

[Comparative Example 1]
Comparative Example 1 is an example in which no aromatic monomer is used in the first stage of emulsion polymerization. By neutralizing the polymerization solution after the first stage of emulsion polymerization, the polymerization solution is improved in transparency and the absorbance ratio is 1%, which is outside the scope of the present invention. In the performance of the obtained aqueous resin composition, glossiness, water resistance and blocking resistance were lowered. The results are shown in Table 1-6.

[Comparative Example 2]
Comparative Example 2 is an example in which 70% of the aromatic monomer used in the first stage emulsion polymerization is out of the scope of the present invention. Since the stability of the polymerization solution during the second stage polymerization is poor, and the performance of the obtained aqueous resin composition is poor in film formability, the glossiness, water resistance and oil resistance of the coating film are reduced, and coating is not possible. The workability is also poor because of its low viscosity. The results are shown in Table 1-6.

[Comparative Example 3]
Comparative Example 3 is an example in which the carboxyl group-containing monomer used in the first stage of emulsion polymerization is 35%, which is out of the scope of the present invention. Since there is much content of the carboxyl group in a copolymer, the viscosity of the obtained aqueous resin composition becomes quite high, and coating suitability is bad. In addition, the gloss and water resistance of the coating film decreased. The results are shown in Table 1-6.

[Comparative Example 4]
Comparative Example 4 is an example in which the amount of the monomer mixture that undergoes emulsion polymerization in the first stage is 24%, which is out of the scope of the present invention. Since the polymer obtained by emulsion polymerization in the first stage does not have a function as a polymer emulsifier, the reaction in the second stage did not proceed.

The meanings of abbreviations etc. written in the table are as follows.
[Monomer]
St: styrene α-MSt: α-methylstyrene MMA: methyl methacrylate BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate AAc: acrylic acid MAAc: methacrylic acid [surfactant]
Latemul E-118B: Polyoxyethylene alkylphenyl ether sulfate ester salt system, anion system, manufactured by Kao Corporation, active ingredient 25%
Newlex R: Alkylbenzenesulfonate, anion, manufactured by NOF Corporation, 50% active ingredient
[Polymerization initiator]
APS: ammonium persulfate [polyvalent metal complex salt]
Aqueous zinc carbonate solution, 18.2% as zinc oxide equivalent (active ingredient)

Test method 1. Weight average molecular weight A coating film obtained by drying each aqueous resin composition at room temperature was dissolved in tetrahydrofuran, and a high performance liquid chromatograph (manufactured by Shimadzu Corporation, LC-10ADvp, column; KF-G + KF-806 × 2). The weight average molecular weight is calculated in terms of St.

2. Absorbance ratio Absorbance was measured from the evaporation residue of each aqueous resin composition, diluted with distilled water so that the evaporation residue was 10,000 ppm, and a spectrophotometer manufactured by Hitachi, Ltd. (100 Using a 10 mm square quartz cell at −40 type, the absorbance (−log T) is measured at a wavelength of 550 nm using distilled water as a blank. The absorbance ratio can be obtained from the following equation.
Absorbance ratio = first stage emulsion polymerization liquid (after neutralization with aqueous ammonia) / first stage emulsion polymerization liquid (before neutralization with aqueous ammonia) × 100

3. Stability at the time of polymerization The amount of resin adhering to the reaction vessel after the completion of polymerization and the amount of aggregates are visually evaluated by filtering with a 125 mesh filter cloth.
◎: No aggregate ○: Slightly aggregate △: Slightly aggregate *: Very large aggregate

4). Storage Stability Each aqueous resin composition is placed in a sealed glass container (500 ml) and stored at 40 ° C. for 1 month, and the rate of change in viscosity is measured.
○: Viscosity change rate is within 10% Δ: Viscosity change rate is within 10-30% ×: Viscosity change rate exceeds 30%

5. Film-forming properties Each aqueous resin composition was diluted to 40% concentration with ion-exchanged water, applied to a glass plate (60 × 150 × 2 mm) to a thickness of 50 μm, and one day in 23 ° C. and 50% RH. Leave it to observe the film formation state.
◎: A clear transparent film ○: No cracks, some whitening is seen Δ: Quite (about 30%) cracks are seen ×: Whitening is seen throughout and there are many cracks

6). Glossiness Each aqueous resin composition was diluted with ion-exchanged water to a concentration of 40%, and the paper coating (trade name: OK L Card, Oji Paper Co., Ltd.) was used to adjust the dry coating thickness to 7 g / m ^2. The sample was coated with a coater and dried for 1 minute in a hot air circulator at 80 ° C. to obtain a glossy sample. The gloss of the specular reflection at 60 ° is measured on the sample with a gloss meter (BYK Gardner Co., Ltd.).
A: Over 80 B: 80-70
Δ: 70-50
X: less than 50

7). Water resistance At room temperature, a drop of water is spotted with a dropper on the coated surface of a sample obtained in the same manner as the glossiness, and the time until the coating film turns white is determined.
◎: More than 60 minutes ○: 60-45 minutes △: 45-30 minutes ×: Less than 30 minutes

8). Heat resistance A sample obtained in the same way as glossiness at room temperature. Place aluminum foil (thickness 12 μm) on the coated surface with a heat seal tester (manufactured by Rigaku Industry Co., Ltd.). .5Kg / cm ² , heat seal at each temperature for 2 seconds, and judge by the temperature at which the material breaks.
A: Over 200 ° C ○: 120-200 ° C
Δ: 120-80 ° C.
×: Less than 80 ° C

9. Oil resistance At room temperature, a drop of salad oil is spotted on the coated surface of the sample obtained in the same manner as the glossiness, and the degree of oil bleeding after wiping with a kitchen towel after 30 minutes is determined.
◎: No change ○: Slight bleeding is observed △: Spot-like bleeding is observed in several places ×: More than half of bleeding is observed

10. 50 ° C. superposed coated surface with each other of the obtained sample in the same manner as in the blocking resistance gloss, 24 hours after standing under a load of 500 g / cm ² in a thermo-hygrostat of RH 90%, allowed to return to room temperature To determine the degree of blocking.
◎: Easily peeled off without blocking ○: Peeled off but slightly sounded △: Partially blocked ×: Blocked over the entire surface

11. Coating suitability Each aqueous resin composition is diluted with ion-exchanged water to a concentration of 40% to obtain a coating solution. The coating solution is coated on a paperboard (trade name: OK El Card, manufactured by Oji Paper Co., Ltd.) with K Rocks Roll (RK Print-Coat INSTRUMENTS, using Anilox Roll 165 line) and the state is observed. To do.
◎: No coating streaks ○: Some coating streaks occur but is not noticeable △: Coating streaks are quite conspicuous ×: Coating streaks are seen on the entire surface

  According to the present invention, the coating film obtained by coating various substrates is excellent in film formability, glossiness, water resistance, heat resistance, oil resistance, blocking resistance, etc. An aqueous resin composition useful as an ink vehicle is also provided.

Claims (6)

  In the presence of at least water, a chain transfer agent, a surfactant and a polymerization initiator, 1 to 30% by mass of the carboxyl group-containing monomer (a) and 1 to 60% by mass of the aromatic monomer (b) The monomer mixture (A) containing 90 to 30% by mass is subjected to emulsion polymerization (first stage polymerization), and after neutralizing part or all of the carboxyl groups of the obtained emulsion polymer with a basic substance, at least Two stages of emulsion polymerization (second stage polymerization) of 10 to 70% by mass of at least one monomer (B) other than the monomer (a) in the presence of water, a surfactant and a polymerization initiator A method for producing an aqueous resin composition comprising polymerization (in the above, the mass% of the monomer is a ratio when the total mass of all monomers is 100 mass%).   The monomer mixture (A) contains a copolymerizable monomer (c) other than the monomers (a) and (b) in a proportion of 1 to 50% by mass of the total monomers. The manufacturing method as described in.   The weight average molecular weight of the emulsion polymer obtained by the first stage emulsion polymerization is 2,000 to 20,000, the pH of the emulsion polymerization solution after neutralization is 5.0 to 9.0, and The production method according to claim 1 or 2, wherein the absorbance after summation is 100 to 20% of the absorbance before neutralization.   The manufacturing method according to any one of claims 1 to 3, wherein the surfactant is an anionic surfactant having no polymerizable unsaturated bond.   An aqueous resin composition obtained by the production method according to claim 1.   Furthermore, the aqueous resin composition of Claim 5 containing a polyvalent metal complex salt.