JP3475977B2 - Copolymer latex composition and water-resistant coating composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a copolymer latex composition and a water resistant coating composition containing the same.

[0002]

2. Description of the Related Art A coating composition coated on various substrates such as metals and plastics is being replaced with a conventional organic solvent-based coating composition by an aqueous coating composition from the viewpoint of protecting the living body and the environment. As a copolymer latex which is a main component of such an aqueous coating composition, one obtained by using an anionic surfactant such as sodium alkylbenzene sulfonate is known. However, the coating film obtained by applying this coating composition has low water resistance, and when left in a state of being dipped in water or the like, there is a problem that the coating film is whitened, and blisters and wrinkles occur. . As a method for improving the water resistance of a coating film, (1) a method of using a coating composition containing a latex whose amount of a surfactant is reduced as much as possible, and (2) crosslinking of a copolymer latex A method of using a coating composition obtained by adding an agent has been proposed. However, the method (1) has a problem that the improvement of water resistance is not yet satisfactory and the chemical stability and mechanical stability of the coating composition are deteriorated.
Further, the method (2) has a problem that the coating composition is inferior in storage stability and chemical stability.

On the other hand, when the coating materials coated with the water-based coating composition are stacked and stored, or when the coating material is used without being sufficiently dried in order to improve the productivity, the coating film is apt to cause blocking and the coating film. There is a problem that the other substances or the coating film and other substances adhere to each other. As a method of improving the blocking resistance, a method of raising the glass transition temperature of a coating film has been proposed (Polymer Publishing Co., Ltd., “Application of Synthetic Latex”, Chapter 8, p. 192, July 30, 1993). First edition, first print). However, there is a problem that an increase in glass transition temperature lowers impact resistance and gloss of the coating film.

On the other hand, the present inventors have found that the monomer (a) described below is used.
If a water-resistant coating composition containing, as an essential component, a copolymer latex (A) obtained by emulsion-polymerizing (b) and (b) in the presence of a specific surfactant, the composition is allowed to stand in a state of being immersed in water. It has been found that a coating film that does not whiten for a long period of time and that does not swell or wrinkle is obtained. However, this water-resistant coating composition still has room for improvement in properties such as film-forming property, blocking resistance, and impact resistance. The amount of water-resistant paints used has been increasing, and there are a wide variety of situations in which the water-resistant paints are being used, and it was necessary to improve these performances.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors in view of the above circumstances, the copolymer latex (A)
To the above, a specific copolymer latex (B) obtained by copolymerizing a monomer mixture consisting of vinyl cyanide monomer, conjugated diene monomer and ethylenically unsaturated carboxylic acid monomer is added. As a result, it was found that a water-resistant coating composition excellent in film-forming property, blocking resistance and impact resistance was obtained, and the present invention was completed based on such findings.

[0006]

Thus, according to the present invention, the copolymer latex (A) is 10% by weight or more and 90% by weight or less in terms of solid content, and the copolymer latex (B).
A copolymer latex composition comprising 10% by weight or more and 90% by weight or less, which is a copolymer latex (A).
In the presence of 2 parts by weight or more and 15 parts by weight or less of the monomer (a) in an amount of 2% by weight or more and 15% by weight or less of the surfactant of the formula (2) based on the monomer (a). After emulsion polymerization, 98 parts by weight or more and 85 parts by weight or less of the monomer (b) in the polymerization system (however, the total amount of the monomer (a) and the monomer (b) is 100 parts by weight), and a single amount It is a copolymer latex obtained by adding 0.1% by weight or more and 2% by weight or less of a surfactant of the formula (2) to the body (b) and carrying out emulsion polymerization. ) Is a hydrophobic ethylenically unsaturated monomer having a solubility in water at 20 ° C and 1 atm of 1% by weight or less, 90% by weight or more, 99.9% by weight or less, and an ethylenically unsaturated carboxylic acid is 0.1% by weight or more. 10% by weight or less and 9.9% by weight or less of other monomer copolymerizable therewith,
The monomer (b) is a hydrophobic ethylenically unsaturated monomer 3 having a solubility in water at 20 ° C. and 1 atm of 1% by weight or less.
0 wt% or more and 99.8 wt% or less, ethylenically unsaturated carboxylic acid 0.1 wt% or more and 10 wt% or less, ethylenically unsaturated carboxylic acid amide 0.1 wt% or more, 5 wt% and these Copolymerizable other monomer 69.8 wt% or less, copolymer latex (B), vinyl cyanide monomer 20 wt% or more, 50 wt% or less, conjugated diene monomer 45 wt% % Or more and 79.5% by weight or less,
0.5% by weight or more of ethylenically unsaturated carboxylic acid monomer,
5% by weight and other monomers copolymerizable therewith 34.5
A copolymer latex which is a copolymer obtained by copolymerizing monomers in an amount of not more than 10% by weight and has a glass transition temperature of 10 ° C. or less. A composition is provided. _{R-O- (CH 2 CH 2} O) n -SO 3 M (2) ( wherein, R is an alkyl group or an aryl group; M is, N
a, K or NH ₄ ; n is 5 to 40. )

Further, according to the present invention, there is provided a water resistant coating composition containing the copolymer latex composition as an essential component.

The present invention will be described below. The copolymer latex (A) of the present invention has the monomer (a) represented by the formula (2).
It is obtained by emulsion polymerization in the presence of the surfactant, and then adding the monomer (b) and the surfactant of the formula (2) to the polymerization system to carry out emulsion polymerization. In the present invention, the surfactant represented by the above formula (2) is used. In formula (2), R is an alkyl group or an aryl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and dodecyl group. Among these, an alkyl group having 6 to 12 carbon atoms is preferable, and an alkyl group having 8 to 10 carbon atoms is particularly preferable.
Further, examples of the aryl group include a phenyl group, a tolyl group, a naphthalene group, and the like. M is Na, K
Alternatively, NH _{4 and the} like are exemplified, and preferable one is Na.
n is 5 to 40, preferably 8 to 30, and more preferably 10 to 25. In addition, n is a value showing the average degree of polymerization of oxyethylene.

Specific examples of such a surfactant include polyoxyalkylene alkyls such as sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene cetyl ether sulfate, sodium polyoxyethylene stearyl ether sulfate and sodium polyoxyethylene oleyl ether sulfate. Ether sulfate salt;
Examples thereof include polyoxyalkylene aryl ether sulfate salts such as sodium polyoxyethylene nonyl phenyl ether sulfate and sodium polyoxyethylene octyl phenyl ether sulfate. Among these surfactants, sodium polyoxyethylene nonylphenyl ether sulfate is preferable, and sodium polyoxyethylene nonylphenyl ether sulfate having an average degree of polymerization of oxyethylene of 18 to 22 is particularly preferable.

In the present invention, first, the monomer (a) is represented by the formula (2)
Emulsion polymerization in the presence of the surfactant. Monomer (a)
Is composed of a hydrophobic ethylenically unsaturated monomer, an ethylenically unsaturated carboxylic acid, and another monomer copolymerizable therewith. Hydrophobic ethylenically unsaturated monomer is 2
It has a solubility in water at 0 ° C. and 1 atm of 1% by weight or less, preferably 0.5% by weight or less. Specific examples of such a hydrophobic ethylenically unsaturated monomer include:
Aromatic vinyls such as styrene and divinylbenzene; esters of alcohols having 4 or more carbon atoms such as butyl acrylate and 2-ethylhexyl acrylate with acrylic acid; and alcohols having 2 or more carbon atoms such as ethyl methacrylate and butyl methacrylate Esters with methacrylic acid; vinyl halides such as vinyl chloride; conjugated diene monomers such as 1,3-butadiene and isoprene. Of these hydrophobic ethylenically unsaturated monomers, aromatic vinyl and esters of alcohols having 4 or more carbon atoms with acrylic acid can be polymerized without generating agglomerates, and are therefore preferable.

The lower limit of the amount of the hydrophobic ethylenically unsaturated monomer in the monomer (a) is 90% by weight or more, preferably 94%.
It is at least wt% and the upper limit is at most 99.9 wt%, preferably at most 98 wt%. If it is less than 90% by weight, the polymerization stability is lowered and aggregates are generated.

As the ethylenically unsaturated carboxylic acid,
(Meth) acrylic acid, maleic acid, itaconic acid and the like can be mentioned, of which (meth) acrylic acid is preferred.

The lower limit of the amount of ethylenically unsaturated carboxylic acid in the monomer (a) is 0.1% by weight or more, and preferably 0.1.
It is 5% by weight or more, and the upper limit is 10% by weight or less, preferably 8% by weight or less. If it exceeds 10% by weight, the viscosity of the latex becomes high.

Hydrophobic ethylenically unsaturated monomers, ethylenically unsaturated carboxylic acids and other monomers copolymerizable therewith include methyl acrylate, ethyl acrylate, propyl acrylate and the like having 3 or less carbon atoms. Ester of alcohol with acrylic acid; methyl methacrylate; ethylenically unsaturated nitrile such as (meth) acrylonitrile;
Carboxylic acid vinyl esters such as vinyl acetate; (meth)
Examples thereof include ethylenically unsaturated carboxylic acid amides such as acrylamide, N-methylol (meth) acrylamide, and diacetone (meth) acrylamide. Of these, the ethylenically unsaturated carboxylic acid amide is usually used in an amount of 0.5% by weight or less of the monomer (a). When the ethylenically unsaturated carboxylic acid amide exceeds 0.5% by weight, aggregates are likely to occur.

The amount of the surfactant used when polymerizing the monomer (a) has a lower limit of 2% by weight or more, preferably 5% by weight or more, based on the monomer (a). The upper limit is 15
It is not more than 12% by weight, preferably not more than 12% by weight. If it is less than 2% by weight, the polymerization stability is lowered, and if it exceeds 15% by weight, the water resistance of the coating film is lowered.

The amount of the monomer (a) has a lower limit of 2 parts by weight or more, preferably 3 parts by weight or more based on 100 parts by weight of the total amount of the monomers (a) and (b). And the upper limit is 15
It is not more than 10 parts by weight, preferably not more than 10 parts by weight. If it is less than 2 parts by weight, the reaction time becomes long, and conversely if it exceeds 15 parts by weight, the viscosity of the copolymer latex becomes high or aggregates are apt to occur.

The monomer (b) comprises a hydrophobic ethylenically unsaturated monomer, an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated carboxylic acid amide and another monomer copolymerizable therewith. Is. As the hydrophobic ethylenically unsaturated monomer, the same ones as mentioned above can be mentioned. Among these, when aromatic vinyl and an ester of alcohol having 4 or more carbon atoms and acrylic acid are used together, no aggregate is generated. It is preferable because it can be polymerized into The lower limit of the amount of the hydrophobic ethylenically unsaturated monomer in the monomer (b) is 30% by weight or more, preferably 60% by weight or more, and the upper limit is 99.8.
It is not more than 9% by weight, preferably not more than 99.4% by weight. Three
If it is less than 0% by weight, the water resistance of the coating film is deteriorated.

As the ethylenically unsaturated carboxylic acid, the same ones as mentioned above can be mentioned, and among these, (meth) acrylic acid is preferable because it produces less aggregates. The lower limit of the amount of ethylenically unsaturated carboxylic acid in the monomer (b) is 0.1% by weight or more, preferably 0.3% by weight or more, and the upper limit is 10% by weight or less, preferably 5% by weight. It is the following. If it is less than 0.1% by weight, the chemical stability of the copolymer latex is lowered, and the water resistance of the coating film is lowered. On the contrary, if it exceeds 10% by weight, the viscosity of the copolymer latex increases and it becomes unsuitable for practical use.

Examples of the ethylenically unsaturated carboxylic acid amide include (meth) acrylamide and N-methylol (meth)
Examples thereof include acrylamide and diacetone (meth) acrylamide. Of these ethylenically unsaturated carboxylic acid amides, N-methylol (meth) acrylamide is suitable because it has high coating film properties such as water resistance and moisture resistance. The lower limit of the amount of ethylenically unsaturated carboxylic acid amide in the monomer (b) is 0.1% by weight or more, preferably 0.3% by weight or more, and the upper limit is 5% by weight or less, preferably 4% by weight. It is the following. If it is less than 0.1% by weight, the chemical stability of the copolymer latex is lowered, and the water resistance of the coating film is lowered. If it exceeds 5% by weight, the viscosity of the copolymer latex increases and it becomes unsuitable for practical use.

Other monomers copolymerizable with the hydrophobic ethylenically unsaturated monomer, ethylenically unsaturated carboxylic acid and ethylenically unsaturated carboxylic acid amide include methyl acrylate, ethyl acrylate and acrylic acid. Examples thereof include esters of alcohols having 3 or less carbon atoms such as propyl with acrylic acid; methyl methacrylate; ethylenically unsaturated nitriles such as (meth) acrylonitrile; vinyl carboxylates such as vinyl acetate.

The lower limit of the amount of the surfactant used when polymerizing the monomer (b) is 0.
It is 1% by weight or more, preferably 0.2% by weight or more, and the upper limit is 2% by weight or less, preferably 1% by weight or less.
If it is less than 0.1% by weight, the polymerization stability tends to be low, resulting in 2% by weight.
If it exceeds, the water resistance of the coating film will decrease.

The copolymer latex (A) thus obtained is 40 to 65 dy at 20 ° C. and 1 atm.
It has a static surface tension in the range of n / cm. Further, the copolymer latex of the copolymer latex (A) has a glass transition temperature in the range of -50 to + 100 ° C. Further, in the copolymer latex (A), the average particle size of the copolymer particles constituting the copolymer latex (A) is in the range of 50 to 500 nm.

The copolymer latex (A) of the present invention contains 2
The lower limit of pH at 0 ° C. is 7 or more, preferably 7.5 or more, and the upper limit is 11 or less, preferably 10 or less. If the pH is less than 7, mechanical stability tends to decrease, and if the pH exceeds 11, the water resistance of the coating film or the like or irritating odor tends to occur. As a pH adjuster, sodium hydroxide, potassium hydroxide, ammonia,
Examples include amines. Of these, ammonia is
It is preferably used because the coating film has high water resistance, salt water resistance and acid resistance.

The copolymer latex (A) of the present invention is obtained by polymerizing the monomer (a) in the presence of the above surfactant, and then adding the monomer (b) and the above surfactant to the polymerization system. It is obtained by adding and polymerizing. The polymerization conversion rate of the monomer (a) is usually 70% or more, preferably 90% or more. If it is less than 70%, generation of aggregates and increase in viscosity are likely to occur. The method for emulsion-polymerizing the monomer (a) in the presence of a surfactant includes adding the monomer (a) to an aqueous medium in which the surfactant is dissolved and polymerizing the emulsion, or And the monomer (a) are mixed to form an emulsion, and the resulting mixture is added to an aqueous medium or an aqueous medium in which the surfactant is dissolved to polymerize. Here, the aqueous medium has water as a main component. As long as the surface tension of the copolymer latex is within the above range, a hydrophilic organic solvent such as alcohol or ketone may be contained.

As the polymerization initiator used for the polymerization of the monomer (a), persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, hydrogen peroxide solution, cumene hydroperoxide, diisopropylbenzene hydroperoxide. , Methylcyclohexyl hydroperoxide, p-menthane hydroperoxide, benzoyl peroxide, di-t-butyl peroxide, 2,2-
Azobis-2,4-dimethylvaleronitrile, azoisobutyronitrile, a redox initiator in which a peroxide is combined with a reducing agent such as sodium bisulfite, and the like can be used. The amount of the polymerization initiator used for the polymerization of the monomer (a) is, with respect to the monomer (a), a lower limit of 2% by weight or more, preferably 4% by weight or more, and an upper limit of 10% by weight.
It is preferably 8% by weight or less. If it exceeds 10% by weight, the water resistance of the coating film is likely to be lowered.

After the polymerization conversion rate of the monomer (a) reaches 70% or more, the monomer (b) and the surfactant are added to the polymerization system and emulsion polymerization is carried out. Polymerization conversion of the monomer (a) is 70
%, The lower limit of the temperature of the polymerization reaction system is 40 or higher, preferably 50 ° C. or higher, and the upper limit is 90 ° C. or lower, preferably 80 or less.
It is preferable to maintain the temperature below ° C. When the temperature is lowered to less than 40 ° C, the water resistance and the like of the coating film obtained by coating the copolymer latex tends to decrease.

Regarding the method of adding the monomer (b) and the surfactant, the monomer (b) may be added as the surfactant as it is or separately from the aqueous solution of the surfactant. You may add after adding (b), a surfactant, and water to make an emulsion. When the monomer (b) is added as the surfactant as it is or separately from the aqueous solution of the surfactant, they may be added simultaneously, or one of them may be added first and the other after. Good.

As the polymerization initiator used in the polymerization of the monomer (b), the same ones as those used in the polymerization of the monomer (a) can be mentioned. The amount of the polymerization initiator used for the polymerization of the monomer (b) is 1% by weight based on the monomer (b), separately from the polymerization initiator used for the polymerization of the monomer (a). It is preferably 0.8% by weight or less. If it exceeds 1% by weight, the water resistance and the like of the coating film deteriorate. Further, the total amount of the polymerization initiator used for the polymerization of the monomer (a) and the monomer (b) is 100 parts by weight based on the total amount of the monomer (a) and the monomer (b). The lower limit is 0.1 parts by weight or more, preferably 0.2 parts by weight or more, more preferably 0.2 parts by weight or more, and the upper limit is 2 parts by weight or less, preferably 1.5 parts by weight or less, more preferably It is 1.2 parts by weight or less. If it exceeds 2 parts by weight, the water resistance and the like of the coating film will decrease. The polymerization conversion rate of the monomer (b) is usually 90% or more, preferably 95% or more. The polymerization temperature in the polymerization of the monomer (a) and the monomer (b) is usually 40 to 90 ° C, preferably 50 to 80 ° C.
Is.

The water-resistant coating composition of the present invention contains a copolymer latex composition comprising a copolymer latex (A) and a copolymer latex (B) as a main component. The amount of the copolymer latex (A) in the copolymer latex composition has a lower limit of 10% by weight or more in terms of solid content,
It is preferably 30% by weight or more, and the upper limit is 90% by weight or less, preferably 70% by weight or less. The amount of the copolymer latex (B) in the copolymer latex composition has a lower limit of 10% by weight or more, preferably 30% by weight or more, and an upper limit of 90% by weight or less, preferably in terms of solid content. Is 70% by weight or less.

The copolymer latex (B) is obtained by polymerizing a vinyl cyanide monomer, a conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer, and another monomer copolymerizable therewith. Is obtained. As the vinyl cyanide monomer, for example, acrylonitrile, methacrylonitrile, etc. are used. With respect to the amount of vinyl cyanide monomer used, the lower limit is 20% by weight or more, preferably 25% by weight or more, and the upper limit is 50% by weight or less, based on the total amount of monomers for obtaining the copolymer latex (B). , Preferably 47% by weight
It is the following. If it is less than 20% by weight, the blocking resistance of the resulting coating film is lowered. On the other hand, if it exceeds 50% by weight, the film-forming property is lowered and the impact resistance is lowered.

Examples of the conjugated diene monomer include 1,
3-Butadiene, isoprene and the like are used. With respect to the amount of the conjugated diene monomer used, the lower limit is 45% by weight or more, preferably 47% by weight or more, and the upper limit is 79.5% by weight, based on all monomers for obtaining the copolymer latex (B). Less than,
It is preferably 75% by weight or less. If it is less than 45% by weight, the film formability is lowered and the impact resistance is lowered. Conversely, 7
If it exceeds 9.5% by weight, the blocking resistance of the obtained coating film is deteriorated.

As the ethylenically unsaturated carboxylic acid monomer, the same ones as described above can be used. The amount of the ethylenically unsaturated carboxylic acid monomer used is such that the lower limit is 0.5% by weight or more, preferably 0.7% by weight or more, based on all the monomers for obtaining the copolymer latex (B). , The upper limit is 5
It is not more than 4% by weight, preferably not more than 4% by weight. If it is less than 0.5% by weight, sufficient stability cannot be imparted, and agglomerates are generated, or the nozzle is clogged during spray coating. On the other hand, if it exceeds 5% by weight, the viscosity of the latex becomes high and it becomes difficult to handle.

Other copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate,
Examples thereof include (meth) acrylic acid ester monomers such as butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate; aromatic vinyl monomers such as styrene and α-methylstyrene. Among these, preferred are aromatic vinyl monomers. The amount of the other copolymerizable monomer used is 34.5% by weight or less and 27.3% by weight or less based on all the monomers for obtaining the copolymer latex (B).

The lower limit of the glass transition temperature of the copolymer latex (B) is -60 ° C or higher, and the upper limit thereof is + 10 ° C or lower,
It is preferably + 5 ° C or lower.

In obtaining the copolymer latex (B),
The polymerization initiator used is not particularly limited, and examples thereof include the same ones as described above.

The surfactant to be used is not particularly limited, and examples thereof include sulfates of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, polyoxyethylene alkylallyl sulfonates, polyphosphates and the like. Examples of the anionic surfactant include nonionic surfactants such as polyethylene glycol alkyl ester type, alkyl phenyl ether type, and alkyl ether type. These surfactants can be used alone or in combination of two or more. With respect to the amount of the surfactant used, the lower limit is 0.05 parts by weight or more, preferably 0.1 parts by weight or more, and the upper limit is 10 parts by weight or less, preferably 5 parts by weight with respect to 100 parts by weight of all the monomers. It is less than or equal to parts by weight. If the amount of surfactant used exceeds 10 parts by weight, excess emulsifier bleeds during film formation,
An unfavorable phenomenon such as a decrease in blocking property occurs. When the amount of the emulsifier used is less than 0.05 parts by weight, a large amount of aggregates are generated during emulsion polymerization, resulting in reduced productivity.

The water resistant coating composition of the present invention comprises a filler, a dispersant, a coloring pigment, an antifoaming agent, an antiseptic, a cross-linking agent, a film forming aid,
If desired, auxiliary materials for coating such as a wetting agent, a rust preventive and a pigment may be contained.

The water resistant coating composition of the present invention is an aqueous dispersion. The solid content concentration is usually 30% by weight or more and 90%.
It is less than or equal to wt. If it is less than 30% by weight, the coating film tends to be cracked, while if it exceeds 90% by weight, the viscosity of the coating composition becomes high and it becomes unsuitable for practical use.

The water-resistant coating composition of the present invention is usually prepared by adding a mixing auxiliary material for paint to the copolymer latex by using a disperser such as a kneader or a disperser and stirring it, or by adding a mixing auxiliary material for paint. It is prepared by adding a copolymer latex and stirring. The water resistant coating composition of the present invention is used by coating it on a substrate. Examples of the base material include metal plates such as stainless steel, steel plates, tin-plated steel plates, aluminum-plated steel plates, and lead-plated steel plates, such as iron, aluminum, and zinc; glass plates; plastic plates. Among these, an iron plate is preferable. Furthermore, the water resistant coating composition of the present invention can be applied to impregnated paper, beater sheets, building materials and the like.

The coating amount of the water resistant coating composition on the substrate is usually in the range of 50 to 400 μm, preferably 100 to 250 μm, as the dry coating film thickness. If it is less than 50 μm, the water resistance of the coating film is lowered, and if it exceeds 400 μm, it takes a long time to dry, so that the coating workability is lowered.

As a coating method, air spray coating, airless spray coating, brush coating, roll coating and the like are usually adopted. Air spray or airless spray coating is preferably used. The drying method is usually 20
As described above, it is left to dry under the temperature condition of 70 ° C. or less.

The preferred embodiments of the present invention are shown below. (1) Copolymer latex (A) 30% by weight or more and 70% by weight or less in terms of solid content, copolymer latex (B)
A copolymer latex composition comprising 30% by weight or more and 70% by weight or less. (2) The hydrophobic ethylenically unsaturated monomer of the copolymer latex (A) is an ester of aromatic vinyl and an alcohol having 4 or more carbon atoms with acrylic acid. (3) The ethylenically unsaturated carboxylic acid of the copolymer latex (A) is (meth) acrylic acid. (4) The ethylenically unsaturated carboxylic acid amide of the copolymer latex (A) is N-methylol (meth) acrylamide. (5) The hydrophobic ethylenically unsaturated monomer of the copolymer latex (A) is an ester of aromatic vinyl and an alcohol having 4 or more carbon atoms and acrylic acid, and the ethylenically unsaturated carboxylic acid is (meth). ) Acrylic acid and the ethylenically unsaturated carboxylic acid amide is N-methylol (meth) acrylamide. (6) The surfactant has an average degree of polymerization of oxyethylene of 18
22 sodium polyoxyethylene nonyl phenyl ether sulfate. (7) The glass transition temperature of the copolymer constituting the copolymer latex (A) is -50 to + 100 ° C. (8) The average particle size of the copolymer constituting the copolymer latex (A) is 50 to 500 nm. (9) The hydrophobic ethylenically unsaturated monomer of the copolymer latex (A) is an ester of aromatic vinyl and an alcohol having 4 or more carbon atoms and acrylic acid, and the ethylenically unsaturated carboxylic acid is (meth). ) Acrylic acid, the ethylenically unsaturated carboxylic acid amide is N-methylol (meth) acrylamide, and the surfactant is sodium polyoxyethylene nonylphenyl ether sulfate having an average degree of polymerization of oxyethylene of 18 to 22. (10) Copolymer latex (B) is 25 to 47% by weight of vinyl cyanide monomer, 47 to 75% by weight of conjugated diene monomer, and 0.7 to 4% by weight of ethylenically unsaturated carboxylic acid monomer. , And other monomers copolymerizable therewith 0 to 27.
It is obtained by copolymerizing a monomer mixture of 3% by weight. (11) The copolymer latex (B) is obtained by copolymerizing acrylonitrile, 1,3-butadiene and (meth) acrylic acid. (12) The copolymer latex composition of the present invention, wherein the copolymer latex (B) has a glass transition temperature of -60 to + 5 ° C. (13) The copolymer latex (B) is a copolymer latex obtained by copolymerizing acrylonitrile, 1,3-butadiene and (meth) acrylic acid, and has a glass transition temperature of -60 to +5. ℃.

[0043]

EFFECTS OF THE INVENTION By using the coating composition containing the copolymer latex composition of the present invention, the blocking resistance and the blocking resistance and the salt water resistance of the copolymer latex (A) are not impaired. Impact resistance can be imparted to the coating. Further, a coating composition having a good film forming property can be obtained.

[0044]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. The parts and% in these examples are based on weight.

The evaluation method of the copolymer latex and the coating film will be described below. [Static surface tension] An auto tension meter (Type 68) was used for the copolymer latex having a solid content of 30%.
01ES: manufactured by Riaisha Co., Ltd.) at 20 ° C.

[Glass Transition Temperature] The copolymer latex was cast on a glass plate and dried at 20 ° C. for 5 days to obtain a film, which was then analyzed using a SSC5200 thermal analyzer (manufactured by Seiko Denshi Kogyo KK). The measurement was performed in the range of 50 to 200 ° C. under the condition of the temperature rising rate of 10 ° C./min.

[Chemical stability] 100 parts of the copolymer latex having a solid content of 50% was added to each of the concentrations of 5, 10, 15, and 2.
100 parts of 0, 25, 30 or 35% aqueous calcium chloride solution was added, stirred and left overnight at 20 ° C., then 10
It was filtered through a 0-mesh wire net, and it was observed whether or not there were solids in the wire net, and the highest concentration of calcium chloride aqueous solution among the calcium chloride concentrations where solids could not be observed was shown as an index.

[Average Particle Size] Laser scattering type particle size measuring device (NICOMP MODEL 370: PACIFI)
C SCIENTIFIC) to determine the volume average particle size.

[B Type Viscosity] A copolymer latex having a solid content concentration of 50% was measured using a BM type viscometer. The measurement was performed with a 3 rotor under the conditions of 20 ° C. and 60 rpm.

[Water resistance] A coating composition was applied to a degreased SPCC-SB steel sheet using an air spray to give a dry film thickness of 150 μm.
After coating so as to have a thickness of m, a coating film was obtained by drying at 80 ° C. for 1 hour, the coated steel sheet was immersed in tap water for one month, and then the state of the coating surface was observed. ◎ ・ No change ○ ・ ・ Swelling or wrinkling area is 0.5% or less of the whole △ ・ ・ Swelling or wrinkling area is more than 0.5 and 5% or less of the whole × ・ ・ Swelling or wrinkling The wrinkle area is over 5% of the total

[Salt water resistance] The same procedure as in the water resistance evaluation was conducted except that 5% concentration of saline was used instead of tap water.

[Film forming property] The degreased SPCC-SB steel sheet was coated with the coating composition using an air spray to give a dry film thickness of 150 μm.
After coating so as to have a thickness of m, the coating film was obtained by drying at 120 ° C. for 1 hour, and the state of the coating film surface was evaluated according to the same criteria as the water resistance evaluation method.

[Blocking resistance] Two SPCC-SB steel plates (0.8 × 70 × 150 mm) that had been degreased were coated with the water resistant coating composition to a thickness of 0.2 mm, and the temperature was 120 ° C. After drying for 1 hour, apply a load of 500 g / cm ² to the coated surfaces together, heat in an oven at 80 ° C for 2 hours, then remove and cool to room temperature.
The test plates were peeled off. Peeling off with almost no resistance ----- ○ There is resistance but the coating does not break --- △ The coating adheres and breaks ---

[Impact resistance] Degreased SPCC-SB
The aqueous coating composition was coated on a steel plate (0.8 × 70 × 150 mm) to a thickness of 0.2 mm, dried at 120 ° C. for 1 hour, and then DuPont-type impact tester (1/2 inch firing pin). , 500 g × 50 cm).

Reference Example 1 Copolymer Latex A1 to A5
In 29 parts of soft water, 95 parts of the monomer (b) having the composition shown in Table 1 and a predetermined amount of a surfactant were added and mixed to obtain an emulsion of the monomer (b). On the other hand, after adding 58 parts of soft water and the surfactant shown in Table 1 to the reactor and further adding 5 parts of the monomer (a) to emulsify and disperse the mixture, the temperature was raised to 80 ° C. and 80 ° C. While maintaining the above condition, 10% aqueous solution of ammonium persulfate was added in an amount shown in Table 1 (column * 2 in Table 1) to initiate polymerization. 1 hour after the initiation of polymerization, ammonium persulfate 1 was added.
A 0% aqueous solution was added in the amount shown in Table 1 (column * 3 in Table 1), and then the monomer (b) emulsion was added over 3 hours. After the addition of the emulsion of the monomer (b), the polymerization is continued for 2 hours, then the residual monomer is removed, and the solid content concentration is 50%.
Then, the temperature was cooled to 20 ° C. to obtain copolymer latexes A1 to A5 of the present invention. The polymerization conversion rate of the monomer (a) and the polymerization conversion rate of the monomer (b) when the monomer (b) was added were both 98% or more.

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[Table 1]

(2) Production of Copolymer Latex B1 to B4 In an autoclave, 90 parts of soft water was mixed with 100 parts of a monomer having the composition shown in Table 2 and 2.0 parts of sodium dodecylbenzenesulfonate (DBS). To obtain a monomer emulsion. The temperature was raised to 60 ° C and 1.0 part of a 10% aqueous solution of ammonium persulfate was added while maintaining the temperature at 60 ° C.
The reaction was completed by reacting for 0 hours. The obtained copolymer latex had a polymerization conversion rate of 99%, a solid content concentration of 52% and a viscosity of 300 centipoise, and had good polymerization stability. The copolymer latex BM viscosity was 500 centipoise when water and ammonia water were added to the copolymer latex to adjust the solid content concentration to 50% and the pH to 8.
The glass transition temperature of the copolymer latex was measured and is shown in Table 2.

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[Table 2]

Examples and Comparative Examples Copolymer latex 1 having the composition shown in Table 3 (calculated as solid content)
Mix 00 parts and 15 parts titanium dioxide (made by Ishihara Sangyo),
A water resistant coating composition was obtained, and its film forming property, blocking resistance, impact resistance, water resistance and salt water resistance were evaluated. The results are shown in Table 3.

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[Table 3]

Control Example 100 parts of copolymer latex A1 and 15 parts of titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd.) were mixed to obtain a water resistant coating composition, which was evaluated in the same manner as in Examples. The results are shown in Table 3.

From Table 3, it can be seen that the water resistant coating composition of the present invention (Experiment Nos. 1 to 6) is excellent in film-forming property, blocking resistance and impact resistance without impairing performances such as water resistance and salt water resistance. You can see that On the other hand, it can be seen that the water-resistant coating composition containing a large amount of the copolymer latex A1 has poor blocking resistance (Experiment No. 7). On the contrary, it can be seen that the water resistant coating composition containing a small amount of the copolymer latex A1 is inferior in blocking resistance, water resistance and salt water resistance (Experiment No. 8). In the water resistant coating composition composition using the copolymer latex B4 having a high glass transition temperature,
It is found that the water resistance, salt water resistance, film-forming property, blocking resistance and impact resistance are poor (Experiment Nos. 9 and 10). It can be seen that the water resistant coating composition composition using the copolymer latex A4 or A5 containing no ethylenically unsaturated carboxylic acid as a constituent monomer is inferior in water resistance and salt water resistance (Experiment Nos. 11 and 12). . Copolymer latex B1
It can be seen that the water-resistant coating composition composition using only the composition is inferior in water resistance, salt water resistance and blocking resistance (Experiment No. 13). It can be seen that the water resistant coating composition composition using only the copolymer latex A1 is inferior in blocking resistance (Experiment No. 14).

Claims (2)

(57) [Claims] 1. A copolymer comprising 10% by weight or more and 90% by weight or less of the copolymer latex (A) and 10% by weight or more and 90% by weight or less of the copolymer latex (B) in terms of solid content. A latex composition, wherein the copolymer latex (A) contains 2 parts by weight or more and 15 parts by weight or less of the monomer (a) in an amount of 2% by weight or more and 15% by weight with respect to the monomer (a). After emulsion polymerization in the presence of the surfactant of the following formula (1), 98 parts by weight or more and 85 parts by weight or less of the monomer (b) (however, the monomer (a) and the monomer (b) are added to the polymerization system. b) is 100 parts by weight) and 0.1% by weight based on the monomer (b).
As described above, the copolymer latex is obtained by adding 2% by weight or less of the surfactant of the formula (1) and emulsion-polymerizing, and the monomer (a) has a solubility in water at 20 ° C. and 1 atm. 90% by weight or more and 99.9% by weight or less of hydrophobic ethylenically unsaturated monomer of 1% by weight or less, 0.1% by weight or more and 10% by weight or less of ethylenically unsaturated carboxylic acid, and copolymerizable with these 30% by weight or more of the hydrophobic monomeric ethylenically unsaturated monomer whose other monomer is 9.9% by weight or less and whose solubility in water at 20 ° C. and 1 atmosphere is 1% by weight or less. , 99.8 wt% or less, ethylenically unsaturated carboxylic acid 0.1 wt% or more, 10 wt% or less, ethylenically unsaturated carboxylic acid amide 0.1 wt% or more, 5 wt% and copolymerizable with these Other monomers 69.8% by weight or less From it, a copolymer latex (B) is a vinyl cyanide monomer 20 wt% or more, 50
% By weight, 45% by weight or more of conjugated diene monomer, 79.
5% by weight or less, ethylenically unsaturated carboxylic acid monomer
A copolymer obtained by copolymerizing a monomer comprising 5% by weight or more and 5% by weight and 34.5% by weight or less of another monomer copolymerizable therewith, and having a glass transition thereof. A copolymer latex composition, which is a latex of a copolymer having a temperature of 10 ° C. or lower. _{R-O- (CH 2 CH 2} O) n -SO 3 M (1) ( wherein, R is an alkyl group or an aryl group; M is, N
a, K or NH ₄ ; n is 5 to 40. ) 2. A water resistant coating composition comprising the copolymer latex composition according to claim 1 as an essential component.