JP2006037026A - Copolymer latex and aqueous coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous coating composition excellent in storage stability and mechanical stability of a coating, when used for marking a road, excellent in initial drying properties and adhesion to a tire after application, and excellent in water resistance of a film obtained therefrom and alkali resistance of the film, and to provide a copolymer latex suitable for the aqueous coating composition. <P>SOLUTION: This copolymer latex contains a copolymer which is obtained by copolymerizing a monomer mixture comprising an acid group-containing monomer and another monomer copolymerizable with the acid group-containing monomer in a water phase in the presence of two kinds of ampholytic surfactants, wherein the surfactants have such pH titration inflection point maximum values that one of the values is in a range of pH 8 to 9.5, the other is in a range of pH 9 to 10.5, and a difference between two of the pH titration inflection point maximum values is 0.5 or more, and the water phase has such a pH value as to be above a pH value which is lower than a maximum of the pH titration inflection point maximum values possessed by both the ampholytic surfactants by 1. The aqueous coating composition contains the latex and is suitable as an aqueous road-marking coating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a copolymer latex and an aqueous coating composition. More specifically, when used for road marking, the present invention is excellent in storage stability and mechanical stability of a coating, initial drying property after application and tire adhesion. The present invention relates to an aqueous coating composition excellent in water resistance and excellent in water resistance and alkali resistance of an obtained coating film, and a copolymer latex suitable for the aqueous coating composition.

Road marking paints are replacing solvent paints with water-based paints in consideration of environmental pollution and danger during construction. The water-based road marking paint has excellent mechanical and storage stability of the paint after blending, excellent initial drying and tire adhesion after application, and water resistance and alkali resistance of the obtained coating film. There is also a need to be superior.
Conventionally, for example, Patent Document 1 discloses an aqueous road marking paint comprising an acrylic emulsion having an alkoxysilyl group having a glass transition temperature of 0 to 70 ° C. and an average molecular weight of 150,000 or more, a colorant and a filler. Has been. The acrylic emulsion having an alkoxysilyl group used here has an acid group obtained by polymerizing a monomer mixture in the presence of an anionic surfactant and / or a nonionic surfactant. A free emulsion is specifically disclosed. However, a paint using such an acrylic emulsion is excellent in the storage stability of the paint and the water resistance of the obtained coating film, but is inferior in the mechanical stability of the paint. Tire adhesion was insufficient.

  Further, Patent Document 2 discloses an aqueous road marking paint in which a polyfunctional amine polymer is blended with an anionically stabilized polymer latex. The anionically stabilized polymer latex used here is a polymer latex obtained by polymerizing a monomer mixture having an acid group such as methacrylic acid in the presence of an anionic surfactant. Is specifically disclosed. However, although a paint using such a polymer latex is relatively excellent in tire adhesion after application, the storage stability and mechanical stability of the paint are insufficient and the water resistance of the coating film and Alkali resistance was also insufficient.

Further, Patent Document 3 discloses an aqueous road marking paint comprising a crosslinking agent such as a binder polymer having an acid group such as a carboxyl group, a polyfunctional amine and a silane compound having an epoxy group. As the binder polymer used here, a binder polymer obtained by polymerizing a monomer mixture in the presence of an anionic surfactant is specifically disclosed. However, although the paint using such a binder polymer is excellent in the tire adhesion after application and the water resistance of the obtained coating film, the storage stability and mechanical stability of the paint are insufficient.
JP-A-9-169944 Japanese Patent Laid-Open No. 10-60308 Japanese Patent Laid-Open No. 10-102004

  In view of the above circumstances, the object of the present invention is excellent in storage stability and mechanical stability of paint, excellent in initial drying property and tire adhesion after application, and obtained when used for road marking. An object of the present invention is to provide an aqueous coating composition excellent in water resistance and alkali resistance of a coating film, and a copolymer latex suitable for the aqueous coating composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained the following knowledge and completed the present invention. That is, the present inventors have different specific pH titration inflection point maximum values, and in the presence of two types of amphoteric surfactants whose difference is not less than a specific value, A monomer latex containing an acid group-containing monomer was copolymerized in an aqueous phase at a pH exceeding the pH value one lower than the maximum pH titration inflection point to obtain a copolymer latex. And, when this copolymer latex is used, the storage stability and mechanical stability of the paint are excellent, the initial drying property after application and the tire adhesion are excellent, and the water resistance and alkali resistance of the obtained coating film are improved. It was also found that an aqueous coating composition suitable as an aqueous road marking coating can be obtained.

Thus, according to the present invention, the pH titration inflection point maximum values are in the range of pH 8 to 9.5 and pH 9 to 10.5, respectively, and the difference in pH titration inflection point maximum value is 0.5 or more. In the presence of two amphoteric surfactants characterized in that they contain acid groups in an aqueous phase at a pH that is one lower than the maximum pH titration inflection point maximum of the amphoteric surfactant. There is provided a copolymer latex obtained by copolymerizing a monomer mixture comprising a monomer and another monomer copolymerizable therewith.
Moreover, according to this invention, the copolymer latex composition formed by mix | blending an acid group containing oligomer with a weight average molecular weight of 1,000-50,000 in said copolymer latex is provided.
Furthermore, according to the present invention, there is provided an aqueous coating composition comprising the above copolymer latex, an acid group-containing oligomer having a weight average molecular weight of 1,000 to 50,000, and a filler. The water-based paint composition can be suitably used as a water-based road marking paint.

  According to the present invention, when used for road marking, the coating has excellent storage stability and mechanical stability, excellent initial drying properties after application and tire adhesion, and water resistance of the obtained coating film. An aqueous coating composition excellent in alkali resistance and a copolymer latex suitable for the aqueous coating composition are also provided.

Hereinafter, the present invention will be described in detail.
(Copolymer latex)
The copolymer latex of the present invention has pH titration inflection point maximum values in the range of pH 8 to 9.5 and pH 9 to 10.5, respectively, and the difference in pH titration inflection point maximum value is 0.5 or more. In the presence of two amphoteric surfactants characterized in that they contain acid groups in an aqueous phase at a pH that is one lower than the maximum pH titration inflection point maximum of the amphoteric surfactant. It contains a copolymer obtained by copolymerizing a monomer mixture comprising a monomer and another monomer copolymerizable therewith.

  The acid group-containing monomer used in the present invention is not particularly limited as long as it is a monomer containing an acid group such as a sulfonic acid group, a phosphoric acid group, or a carboxyl group. A group containing a group is preferable, and a monomer containing a strong acid group such as a sulfonic acid group can be used more preferably from the viewpoint of excellent blending stability.

  Examples of the monomer containing a sulfonic acid group include styrene sulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and 4-sulfonic acid butyl. And methacrylate. These monomers can be used alone or in combination of two or more, and can also be used in the form of a salt neutralized with a base such as ammonia, triethylamine or sodium hydroxide.

  Examples of the monomer containing a phosphoric acid group include acid phosphoxyethyl (meth) acrylate, 3-chloro-2-acid phosphoxypropyl (meth) acrylate, and acid phosphoxypolyoxyethylene glycol mono (meth) acrylate. Etc. These monomers can be used alone or in combination of two or more, and can also be used in the form of a salt neutralized with a base such as ammonia, triethylamine or sodium hydroxide.

  Examples of the monomer containing a carboxyl group include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; ethylenically unsaturated polyvalent carboxylic acids such as maleic acid, fumaric acid, and itaconic acid; Examples thereof include acid anhydrides thereof; partially esterified products of ethylenically unsaturated polyvalent carboxylic acids such as methyl maleate and methyl itaconate; and the like. These monomers can be used alone or in combination of two or more, and can be used in the form of a salt neutralized with a base such as ammonia, triethylamine or sodium hydroxide.

  The amount of the acid group-containing monomer used is preferably 0.1 to 5% by weight, more preferably 0.2 to 2% by weight, based on the total amount of the monomer mixture. If the amount used is too small, the mechanical stability of the water-based coating composition tends to decrease, and conversely if too large, the tire adhesion of the coating after application tends to decrease.

Examples of other monomers copolymerizable with the acid group-containing monomer include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene and the like. Conjugated diene monomers; aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) Ethylenically unsaturated carboxylic acid alkyl ester monomers such as 2-ethylhexyl acrylate; (methacryloxymethyl) dimethylethoxysilane, methacryloxypropyldimethylethoxysilane, methacryloxypropyldimethylmethoxysilane, methacryloxypropylpentamethyldisiloxane, Reactive silicone oil monomers such as methacryloxytrimethylsilane; acrylamide, Ethylenically unsaturated carboxylic acid amide monomers such as tacrylamide, N, N-dimethylacrylamide, N-methylolacrylamide; ethylenically unsaturated carboxylic acid hydroxyalkyl esters such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate Monomer; carboxylic acid vinyl ester monomers such as vinyl acetate; and the like. These can be used alone or in combination of two or more.
Among the other copolymerizable monomers, an aromatic vinyl monomer, an ethylenically unsaturated carboxylic acid alkyl ester monomer, and a reactive silicone oil alone are used because the coating film has excellent weather resistance and water resistance. A monomer can be preferably used.

  The amount of the other copolymerizable monomer used is preferably 99.9 to 95% by weight, more preferably 98 to 99.8% by weight, based on the total amount of the monomer mixture. If the amount used is too small, the initial drying property of the paint after application, tire adhesion, and the water resistance of the resulting coating film tend to be inferior. On the other hand, if the amount is too large, the mechanical stability of the water-based paint composition is high. Tends to decrease.

  In obtaining the copolymer latex of the present invention, the pH titration inflection point maximum values are in the range of pH 8 to 9.5 and pH 9 to 10.5, respectively, and the difference in pH titration inflection point maximum value is 0. In the presence of two amphoteric surfactants characterized by being 5 or more, in an aqueous phase having a pH exceeding the maximum pH titration inflection point maximum value of the amphoteric surfactant by one, It is an essential condition to copolymerize the monomer mixture, and it is preferable to emulsion copolymerize the monomer mixture.

In the present invention, the maximum value of pH titration inflection point means the highest pH value among pH titration inflection points. The pH titration inflection point means that when a base is added to an aqueous solution in which an amphoteric surfactant is dissolved and pH titration is performed in the range of pH 3 to 12, the amphoteric surfactant is dissolved with respect to the amount of base added. The pH value corresponding to the inflection point of the pH titration curve obtained by plotting the pH of the prepared aqueous solution. The inflection point refers to the point at which the change in the slope of the tangent changes from positive to negative in the pH titration curve.
One or a plurality of the pH titration inflection points are present for one kind of amphoteric surfactant.
In the case of an amphoteric surfactant having only one pH titration inflection point, this is the maximum pH titration inflection point, and in the case of an amphoteric surfactant having a plurality of pH titration inflection points, the highest pH among them. The value is defined as the maximum pH titration inflection point.

Specifically, the pH titration inflection point can be measured as follows.
(1) Collect 100 ml of sample solution diluted to a predetermined concentration in a 200 ml beaker. The predetermined concentration is set in the range of pH 3 to 12 so that the total base titration amount required for pH titration is about 10 ml.
(2) Dilute hydrochloric acid (10%) in an amount such that the pH of the sample solution is less than 3 is added to the sample solution.
(3) For example, using a potentiometric automatic titrator (AT-500N: manufactured by Kyoto Electronics Industry Co., Ltd.), at 25 ° C., using a 0.1 N methanolic potassium hydroxide solution as a base, one titration Titrate to pH 12 with a volume of 0.2 ml and a titration interval of 30 seconds.
(4) Plot the change in pH of the sample solution against the amount of base added, and determine the pH value corresponding to the inflection point in the pH titration curve. (This operation can also be obtained by an automatic calculator attached to the potentiometric automatic titrator.) When there are a plurality of inflection points, the maximum pH value is set as the maximum pH titration inflection point.

Examples of the amphoteric surfactant having a pH titration inflection point maximum of pH 8 to 9.5 include lauryl dimethylaminoacetic acid betaine, lauric acid amidopropyl betaine, coconut oil fatty acid amidopropyl betaine, and alkylpolyaminoethylglycine hydrochloride. It is done. These amphoteric surfactants may be used either alone or in combination.
A preferable pH titration inflection point maximum value of the amphoteric surfactant having a pH titration inflection point maximum value of pH 8 to 9.5 is pH 8.3 to 9.4. If this pH titration inflection point maximum value is too high, the blending stability tends to be inferior, whereas if it is too low, the tire adhesion after application tends to be inferior.

Examples of the amphoteric surfactant having a pH titration inflection point maximum value of pH 9 to 10.5 include coconut oil fatty acid amidopropyl betaine, alkyl polyaminoethyl glycine hydrochloride, sodium alkyl diaminoethyl glycine and the like. These amphoteric surfactants may be used either alone or in combination.
A preferable pH titration inflection point maximum value of the amphoteric surfactant having a pH titration inflection point maximum value of pH 9 to 10.5 is pH 9.5 to 10.5, and more preferably pH 9.8 to 10.5. 5. If this pH titration inflection point maximum value is too high, a large amount of base is used to adjust the pH, so the odor deteriorates and the blending stability tends to be inferior. Conversely, if it is too low, There is a tendency for tire adhesion to decrease.

Because of the excellent balance between the storage stability of the paint, the initial drying property after application, and the tire adhesion, which is the object of the present invention, the maximum pH titration inflection point of the two amphoteric surfactants used in the present invention is The difference is 0.5 or more, and preferably 0.8 or more.
Here, when at least one of the two types of amphoteric surfactants is used in combination with a plurality of compounds, the difference between the maximum pH titration inflection point maximum values of the plurality of compounds is determined by the pH titration inflection. The difference between the point maximum values.

  The amount of the amphoteric surfactant used is preferably 0.3-5 parts by weight, more preferably 0.5-3 parts by weight with respect to 100 parts by weight of the monomer mixture. If the amount used is too small, the polymerization stability is inferior, and coarse aggregates are likely to be generated, and the adhesion to the tire after application of the paint tends to decrease. It tends to be inferior.

  The amount of amphoteric surfactant having a pH titration inflection point maximum of pH 9 to 10.5 is preferably 10 to 95% by weight, more preferably 40 to 92% by weight, based on the total amount of amphoteric surfactant used. It is. If the amount of amphoteric surfactant having a pH titration inflection point maximum value of pH 9 to 10.5 is too small, tire adhesion after application of the water-based coating composition tends to be reduced. There is a tendency for the stability of the to decrease.

  In the polymerization, a nonionic surfactant such as polyoxyethylene alkyl ester or polyoxyethylene alkyl allyl ether can be used as long as the effects of the present invention are not essentially impaired.

It is essential that the polymerization be carried out in an aqueous phase at a pH exceeding 1 pH lower than the maximum pH titration inflection point of the amphoteric surfactant used, exceeding 0.7 lower pH value. More preferably, it is carried out in an aqueous phase at pH. Copolymer which is inferior in polymerization stability when polymerized in an aqueous phase having a pH one or more lower than the maximum pH titration inflection point of the amphoteric surfactant used, and can be suitably used in an aqueous coating composition Latex is not obtained.
The upper limit of the pH of the aqueous phase is not particularly limited, but is usually pH 12, preferably 11.5.

In the polymerization, water is usually used.
Although the usage-amount of water is not specifically limited, It is 50-500 weight part normally with respect to 100 weight part of monomer mixtures, Preferably it is 70-200 weight part.

To adjust the pH of the aqueous phase to the desired range, a base is added to the aqueous phase.
The base is not particularly limited, and examples thereof include organic amines such as trimethylamine and triethanolamine; inorganic bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, and potassium carbonate: ammonia. These may be used alone or in combination of two or more. Among the above bases, ammonia can be preferably used in terms of obtaining an aqueous coating composition which is excellent in initial drying property after application and tire adhesion, and further in water resistance of the coating film.
The addition amount of the base is appropriately selected so that the pH of the aqueous phase becomes a desired value.

In the present invention, the emulsion polymerization method itself may be in accordance with a conventionally known method.
Examples of the polymerization initiator include inorganic persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; organic peroxides such as cumene hydroperoxide, benzoyl peroxide, and isopropylbenzene peroxide; azoisobutyronitrile An azo compound such as can be used. These can be used alone or in combination of two or more.
Among polymerization initiators, inorganic persulfates can be preferably used in terms of good polymerization stability, and a redox system in which the inorganic persulfate is combined with a reducing agent such as sodium bisulfite or ferrous sulfate. It can also be used as a polymerization initiator.
The amount of the polymerization initiator used is usually 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight per 100 parts by weight of the total monomer mixture.

In the present invention, a molecular weight modifier can also be used.
The molecular weight modifier is not particularly limited, and examples thereof include alkyl mercaptans such as hexyl mercaptan, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan; Halogenated hydrocarbons such as carbon chloride, carbon tetrabromide and ethylene bromide; mercaptocarboxylic acid alkyl esters such as mercaptoacetic acid 2-ethylhexyl ester, mercaptopropionic acid 2-ethylhexyl ester, mercaptopropionic acid tridecyl ester; mercaptoacetic acid methoxy Mercaptocarboxylic acid alkoxyalkyl esters such as butyl ester and mercaptopropionic acid methoxybutyl ester; carboxylic acid mercaptoalkyls such as octanoic acid 2-mercaptoethyl ester And α-methylstyrene dimer. These can be used alone or in combination of two or more.
What is necessary is just to select the usage-amount of a molecular weight modifier suitably as needed.

In carrying out the polymerization, any of batch addition, divided addition, and continuous addition can be employed as a method for adding the monomer mixture and the surfactant.
When adopting the divided addition method, the composition and amount of the monomer mixture or surfactant may be changed at each stage. When the continuous addition method is adopted, the composition and amount of the monomer mixture and the surfactant may be made uniform or may be changed continuously or intermittently with time.
Among them, while continuously adding a monomer mixture, a monomer emulsion obtained by mixing a part or all of the amphoteric surfactant and a part of water used for polymerization, to a reactor. A polymerization method is preferably employed.

  In addition to the above, for example, inorganic salts such as sodium tripolyphosphate and potassium chloride; polymerization auxiliary materials such as seed latex, dispersant, oxygen scavenger and chelating agent may be used as appropriate.

The polymerization temperature is usually 0 to 100 ° C, preferably 50 to 95 ° C.
The polymerization time can be appropriately selected until a desired polymerization conversion rate is reached.

As described above, the monomer mixture is copolymerized, and when the desired polymerization conversion rate is reached, the polymerization reaction is stopped by adding a polymerization terminator or cooling the polymerization system.
The polymerization conversion rate when stopping the polymerization reaction is preferably 90% by weight or more, more preferably 95% by weight or more.
After stopping the polymerization reaction, if desired, unreacted monomers are removed, and the solid content concentration and latex pH are adjusted to obtain a copolymer latex.
To the copolymer latex, compounding agents such as an anti-aging agent, a pH adjuster, a thickener, a dispersant, an antiseptic and an antibacterial agent, which are usually blended, can be appropriately added.

The glass transition temperature of the copolymer constituting the copolymer latex is not particularly limited, but is usually −50 to + 50 ° C. When the copolymer latex of the present invention is applied to an aqueous road marking paint, the glass transition temperature of the copolymer is preferably -5 to + 50 ° C, more preferably 0 to + 30 ° C. preferable. By setting the glass transition temperature within the above range, an aqueous road marking paint having an excellent balance between the film formability at low temperatures and the strength of the coating film can be obtained.
The glass transition temperature of the copolymer can be easily adjusted by appropriately selecting the composition of the monomer mixture.

  The volume average particle diameter of the copolymer latex is preferably 100 to 300 nm, more preferably 120 to 250 nm.

  The solid content concentration of the copolymer latex is preferably 48 to 65% by weight, more preferably 50 to 60% by weight. If the solid content concentration is too low, the initial drying property and the tire adhesion tend to be inferior. On the other hand, if the solid content concentration is too high, the viscosity becomes too high and handling is difficult.

  The pH of the copolymer latex is set to a value exceeding a pH value one lower than the maximum pH titration inflection point of the amphoteric surfactant used in the polymerization, and 0.7 lower than the pH titration inflection point maximum. A value exceeding the pH value is preferred. The upper limit of the pH of the copolymer latex is not particularly limited, but is usually pH 12, preferably pH 11.5.

(Water-based paint composition)
The aqueous coating composition of the present invention contains the copolymer latex and a filler.
The filler is not particularly limited as long as it is usually used in water-based paint compositions. For example, calcium carbonate, barium carbonate, magnesium silicate, calcium silicate, calcium sulfate, meteorite powder, celite, clay, talc, mica And alumina. The blending amount of the filler is preferably 100 to 400 parts by weight, more preferably 150 to 300 parts by weight, and particularly preferably 170 to 250 parts by weight per 100 parts by weight of the copolymer latex solid content. If the blending amount is too small, the solid content concentration of the aqueous coating composition tends to be low, and the initial drying property and the tire adhesion tend to be inferior. On the other hand, when the amount is too large, it becomes difficult to disperse the filler, and the viscosity of the aqueous coating composition tends to be high, which makes it difficult to handle.

  The aqueous coating composition of the present invention preferably further contains an acid group-containing oligomer having a weight average molecular weight of 1,000 to 50,000. The aqueous coating composition containing the oligomer is excellent in the storage stability and mechanical stability of the coating, and the tire adhesion after application is remarkably improved.

(Acid group-containing oligomer)
The acid group-containing oligomer is not particularly limited as long as it is an oligomer containing an acid group such as a sulfonic acid group, a phosphoric acid group, or a carboxyl group, but one containing a carboxyl group can be preferably used.

  The acid group-containing oligomer is usually formed by polymerizing a monomer containing an acid group such as a sulfonic acid group, a phosphoric acid group, or a carboxyl group, or a monomer containing the acid group and a monomer copolymerizable therewith. It is obtained by copolymerizing a monomer.

  Examples of the monomer containing a carboxyl group include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; ethylenically unsaturated polyvalent carboxylic acids such as maleic acid, fumaric acid, and itaconic acid; Examples thereof include acid anhydrides thereof; partially esterified products of ethylenically unsaturated polyvalent carboxylic acids such as methyl maleate and methyl itaconate; and the like. Of these, maleic acid and its acid anhydride can be preferably used. These monomers containing a carboxyl group can be used alone or in combination of two or more, and can be used in the form of a salt neutralized with a base such as ammonia, triethylamine, sodium hydroxide or the like. .

  Examples of the monomer containing a sulfonic acid group include styrene sulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and 4-sulfonic acid butyl. And methacrylate. These monomers can be used alone or in combination of two or more, and can also be used in the form of a salt neutralized with a base such as ammonia, triethylamine or sodium hydroxide.

  Examples of the monomer containing a phosphoric acid group include acid phosphoxyethyl (meth) acrylate, 3-chloro-2-acid phosphoxypropyl (meth) acrylate, and acid phosphoxypolyoxyethylene glycol mono (meth) acrylate. Etc. These monomers can be used alone or in combination of two or more, and can also be used in the form of a salt neutralized with a base such as ammonia, triethylamine or sodium hydroxide.

Examples of the monomer copolymerizable with the acid group-containing monomer include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and 2-methyl-1,3-butadiene. Conjugated diene monomers such as: aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, ( Ethylenically unsaturated carboxylic acid alkyl ester monomers such as (meth) acrylic acid 2-ethylhexyl; Ethylenically unsaturated carboxylic acid amide monomers such as acrylamide, methacrylamide, N, N-dimethylacrylamide, N-methylolacrylamide; Ethylenically unsaturated carboxylic acid hydroxyalkyl ester monomers such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate; Carboxylic acid vinyl ester monomers such as vinyl acetate; These can be used alone or in combination of two or more.
Among the other monomers copolymerizable with the acid group-containing monomer, an aromatic vinyl monomer is preferable, and styrene is more preferable in terms of excellent initial drying property and adhesion to a tire. Can be used.

The acid value range of the acid group-containing oligomer is preferably 100 to 500 mgKOH / g, more preferably 180 to 350 mgKOH / g. This acid value is a value measured based on JIS K 0070. This acid value can be adjusted, for example, by appropriately selecting the proportion of the monomer containing the acid group and polymerizing.
In addition, when the acid group in the oligomer is neutralized in advance and the acid group forms a salt, the oligomer forming the salt is acid-treated to convert the salt into an acid group, and then the oligomer. The acid value of can be measured.

  The weight average molecular weight of the acid group-containing oligomer is preferably 1,000 to 50,000, more preferably 3,000 to 30,000. When the weight average molecular weight is in the above range, an aqueous coating composition that is excellent in the storage stability of the coating material, the tire adhesion after coating, and the water resistance of the coating film can be obtained. This weight average molecular weight can be adjusted by a conventional method such as using an appropriate amount of a polymerization initiator or a molecular weight modifier.

  The acid group-containing oligomer is obtained by polymerizing the monomer containing the acid group or copolymerizing the monomer containing the acid group and a monomer copolymerizable therewith by a conventional method. Can be manufactured. Moreover, if there exists a commercial item corresponding to this oligomer, it can also be used.

The acid group-containing oligomer in the present invention is preferably used after being dissolved in water, and the acid group-containing oligomer is preferably used after being neutralized with a base.
Although it does not specifically limit as a base used for neutralization, For example, organic amines, such as a trimethylamine and a triethanolamine; Inorganic bases, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate: Ammonia etc. Is mentioned. These may be used alone or in combination of two or more. Among the above bases, ammonia can be preferably used from the viewpoint that an aqueous coating composition which is excellent in initial drying property, tire adhesion and water resistance of the coating film can be obtained. The amount of the base added can be appropriately selected within a range in which the oligomer exhibits water solubility according to the acid value of the acid group-containing oligomer.

  The content of the acid group-containing oligomer is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 3 parts by weight per 100 parts by weight of the copolymer latex solid content. Part. If the blending amount is too small, the adhesion of the paint to the tire tends to decrease, and conversely if too large, the water resistance of the coating film tends to decrease.

The method for producing the aqueous paint containing the polymer latex, acid group-containing oligomer and filler of the present invention is not particularly limited,
(A) a method in which a filler is later mixed into a polymer latex and a polymer latex composition containing an acid group-containing oligomer;
(B) A method of mixing an acid group-containing oligomer later after mixing a filler with the polymer latex,
(C) The method of mixing polymer latex, an acid group containing oligomer, and a filler simultaneously is mentioned. Of these, the method (a) is preferable in that the storage stability and mechanical stability of the paint are excellent.

  The pH of the copolymer latex composition is preferably set to a value exceeding a pH value one lower than the maximum pH titration inflection point maximum value of the amphoteric surfactant used in the polymerization.

It is preferable to add a color pigment to the water-based coating composition of the present invention.
As the color pigment, those usually used in water-based coating compositions can be used, and examples thereof include titanium oxide, chrome lead, petal, cyanine blue, and cyanine green. The blending amount when blending the color pigment is preferably 20 to 200 parts by weight, more preferably 30 to 150 parts by weight, and particularly preferably 40 to 100 parts by weight per 100 parts by weight of the solid content of the copolymer latex. It is. If the blending amount is too small, the hiding power is insufficient and it is not suitable as a water-based road marking paint. Conversely, if it is too large, it is difficult to disperse the colored pigment, and the paint viscosity as the water-based road marking paint is low. It becomes expensive and difficult to handle.

A silane coupling agent may be further blended in the aqueous coating composition of the present invention.
Examples of the silane coupling agent include epoxy silane coupling agents such as γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Vinyl-based silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris (β-methoxyethoxy) silane; methacryloxy-based silane coupling agents such as γ- (methacryloyloxypropyl) trimethoxysilane; N-β -(Aminoethyl) -γ-aminopropyltrimethoxysilane, amino-based silane coupling agents such as γ-aminopropyltriethoxysilane; mercapto-based silane coupling agents such as γ-mercaptopropyltrimethoxysilane; It is below. Among these, an epoxy-based silane coupling agent can be preferably used in terms of excellent storage stability of the paint. These silane coupling agents may be used alone or in combination of two or more.

  When the silane coupling agent is blended, the blending amount is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 3 parts by weight, particularly preferably 100 parts by weight of the copolymer latex solid content. Is 0.3 to 1 part by weight.

If necessary, a dispersant, a wetting agent, a plasticizer, an antifoaming agent, a film-forming aid, an antifreezing agent, a thickening agent, and the like can be appropriately added to the aqueous coating composition of the present invention.
Examples of the film-forming aid include butyl carbitol acetate, butyl carbitol, butyl cellosolve, butyl cellosolve acetate, benzyl acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and the like.
Examples of the antifreezing agent include lower alcohols such as methyl alcohol and ethyl alcohol.

  The solid content concentration of the aqueous coating composition of the present invention is preferably 50% by weight or more, more preferably in the range of 60 to 90% by weight, and particularly preferably in the range of 70 to 85% by weight. . If the solid content concentration is too low, the initial drying property and tire adhesion of the paint tend to be inferior. On the other hand, if it is too high, it is difficult to produce the paint.

  The pH of the aqueous coating composition is preferably a value exceeding a pH value that is one lower than the maximum pH titration inflection point maximum of the amphoteric surfactant used in the polymerization, and the pH of the aqueous coating composition is It is preferable to adjust by adding the above-mentioned base, especially ammonia.

  As a method for producing the aqueous coating composition of the present invention, a usual method for producing an aqueous coating composition can be employed. For example, if desired, a dispersant or an antifoaming agent is added to the copolymer latex, and the filler and, if necessary, the colored pigment are dispersed by a dry pigment method. Thereafter, the desired film-forming aid and antifreeze agent are added. Etc. are mixed to produce an aqueous coating composition.

  As a coating method of the aqueous coating composition of the present invention, a known coating method such as spray, airless spray, roll, brush, etc. can be employed.

The water-based paint composition of the present invention includes, for example, road marking paints, building interior or exterior paints, gate paints, automobile interior or exterior paints, automobile vibration-damping paints, and automobile chipping-resistant paints. It can be used as a paint for interior and exterior parts of automobiles and a paint for housings of electrical products. Among these, it can be suitably used as a water-based road marking paint.
When used as an aqueous road marking paint, glass cullet or glass beads can be blended or sprayed onto the surface immediately after application for improving visibility. Further, in order to further improve the initial drying property and the tire adhesion, an aqueous solution of a polyvalent metal salt or a water-absorbing substance can be sprayed on the surface after coating.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, “%” and “part” are based on weight unless otherwise specified.

Evaluation was performed as follows.
(Measurement of pH)
The pH at 25 ° C. was measured using a pH meter (M-8: manufactured by Horiba, Ltd.).
(Maximum pH titration inflection point of amphoteric surfactant)
Using a potentiometric automatic titrator (AT-500N: manufactured by Kyoto Electronics Industry Co., Ltd.), the measurement was performed at 25 ° C. as described above.
(Volume average particle diameter)
The volume average particle size of the copolymer latex was measured using a light scattering type particle size measuring device (model N4: manufactured by Coulter).
(Glass transition temperature of copolymer latex)
The obtained copolymer latex was cast into a glass mold to prepare a dry film having a thickness of 0.3 mm. About this film, the temperature range of -100-150 degreeC was measured with the temperature increase rate of 20 degree-C / min using the differential scanning calorimeter (EXSTAR6000DSC: Seiko Instruments Co., Ltd. product).

(Storage stability of water-based paint composition)
The viscosity of the obtained water-based paint at 23 ° C. is measured using a B-type viscometer. This paint was stored at 50 ° C. for 30 days, then cooled again to 23 ° C., and the viscosity of the paint was measured. The ratio of the absolute value of the difference in paint viscosity before and after storage to the paint viscosity before storage was calculated by the following formula (1) and displayed according to the following criteria.
(| Viscosity after storage−viscosity before storage | / viscosity before storage) × 100 (%) (1)
○: Change rate of less than 10% Δ: Change rate of 10% or more and less than 20% ×: Change rate of 20% or more (mechanical stability of aqueous coating composition)
It was measured with a Maron mechanical stability tester. The prepared aqueous coating composition 75 g (solid content concentration 30%) was weighed and treated for 10 minutes at a load of 15 kg / cm ² and a rotation speed of 1,000 rpm. The treated paint was filtered through a 100 mesh wire mesh that had been weighed in advance, and dried at 105 ° C. for 2 hours. After drying, the residue on the wire mesh was weighed, and the ratio of the residue to the solid content of the paint used for evaluation was calculated and evaluated according to the following criteria. The smaller the amount of the residue, for example, even when mechanical shearing is applied to the aqueous coating composition by spray coating or the like, the generation of coarse aggregates is less, the spray coating property is excellent, and a coating film with less damage defects is obtained. .
○: Less than 0.2% △: 0.2% or more and less than 0.5% ×: 0.5% or more

(Initial drying property of aqueous coating composition)
The obtained aqueous coating composition was applied to a glass plate with a thickness of 250 μm using an applicator. After applying the paint under windless conditions of 23 ° C. and 50% humidity, the surface of the coating film was lightly rubbed with a finger every minute, and the time until the paint did not adhere to the finger was measured. The shorter the time until the paint does not adhere to the finger, the higher the initial drying property of the aqueous paint.

(Tire adhesion of water-based paint composition)
The obtained water-based coating composition was applied to a glass plate with a thickness of 250 μm using an applicator, and the tire adhesion was tested according to JIS K 5665 under no wind conditions at 23 ° C. and 50% humidity. After applying the paint, the tire adhesion was tested every minute, and the time until the peeled surface of the coating film did not adhere to the tire was measured. The shorter the time until the coating film does not adhere to the tire, the better the tire adhesion of the water-based paint.

(Water resistance of coating film)
The obtained paint was applied on a glass plate with an applicator having a thickness of 250 μm, dried at 23 ° C. and 50% humidity for 72 hours, and then immersed in water for 24 hours. The sample was taken out of water, the state of the coating film surface was observed, and judged according to the following criteria.
○: There is no change in the state of the coating film surface compared with that before water immersion.
(Triangle | delta): The location which the coating film swells with water and has peeled from the glass plate exists partially.
X: The coating film peeled from the glass plate over almost the entire surface.

(Alkali resistance of coating film)
The obtained paint was applied onto a glass plate with an applicator having a thickness of 250 μm, dried at 23 ° C. and 50% humidity for 72 hours, and then immersed in a saturated aqueous solution of sodium hydroxide for 18 hours. The sample was taken out from the saturated aqueous solution of sodium hydroxide, the state of the coating film surface was observed, and judged according to the following criteria.
○: There is no change in the state of the coating film surface compared with that before water immersion.
(Triangle | delta): The location which the coating film swells with water and has peeled from the glass plate exists partially.
X: The coating film peeled from the glass plate over almost the entire surface.

Example 1
<Manufacture of copolymer latex>
In a pressure vessel, 28 parts of deionized water, 1.4 parts of sodium alkyldiaminoglycine (Levon S: Sanyo Chemical Industries, Ltd .: pH titration inflection point maximum value = pH 10.2) as an amphoteric surfactant, lauryl dimethyl 0.6 parts of aminoacetic acid betaine (Levon LD-36: manufactured by Sanyo Chemical Industries, Ltd .: pH titration inflection point maximum value = pH 8.45) and 0.25 parts of 28% aqueous ammonia solution were added. The pH of this aqueous solution was 10.2. To this aqueous solution, 50 parts of butyl acrylate, 50 parts of methyl methacrylate and 0.4 part of sodium styrenesulfonate were added and mixed to obtain a monomer emulsion.
To a pressure-resistant reaction vessel, 40 parts of deionized water, 0.1 part of sodium tripolyphosphate, 0.05 part of sodium alkyldiaminoglycine and 0.1 part of 28% aqueous ammonia solution were added. The pH of this aqueous solution was 10.5. After raising the temperature of the aqueous solution in the reaction vessel to 80 ° C., the monomer emulsion was continuously added to the reaction vessel over 5 hours while maintaining the temperature. At the same time as the continuous addition of the monomer emulsion was started, an aqueous solution in which 0.12 part of potassium persulfate was dissolved was added to the reaction vessel to start the polymerization reaction.

After completing the continuous addition of the monomer emulsion, an aqueous solution in which 0.12 part of potassium persulfate was dissolved was added to the reaction vessel, and the reaction was further continued at 80 ° C. for 2 hours. Thereafter, the polymerization system was cooled to stop the polymerization reaction. The polymerization conversion rate at this time was 97%, and the pH of the reaction solution was 9.8.
After removing unreacted monomers from the obtained reaction solution, the pH was adjusted to 10.5 with ammonia water and the solid content concentration was adjusted to 52% to obtain a copolymer latex A. The volume average particle diameter and glass transition temperature of copolymer latex A were measured, and the results are shown in Table 1.

(Examples 2 to 4)
Except having changed polymerization prescription as shown in Table 1, it polymerized like Example 1 and obtained copolymer latex BD. These volume average particle diameters and glass transition temperatures were measured, and the results are shown in Table 1.

(Comparative Example 1)
A copolymer latex E was obtained by polymerizing in the same manner as in Example 1 except that sodium lauryl sulfate was used instead of the amphoteric surfactant and the polymerization formulation shown in Table 1 was used. The volume average particle diameter and glass transition temperature of copolymer latex E were measured, and the results are shown in Table 1.

(Comparative Example 2)
A copolymer latex F was obtained by polymerizing in the same manner as in Example 1 except that sodium styrenesulfonate, which is an acid group-containing monomer, was not used and the polymerization prescription shown in Table 1 was used. The volume average particle diameter and glass transition temperature of the copolymer latex F were measured, and the results are shown in Table 1.

(Comparative Example 3)
Polymerization was conducted in the same manner as in Example 1 except that the pH in the aqueous phase at the start of polymerization was not adjusted. However, since the polymerization stability was poor and a large amount of coarse aggregates were generated, the subsequent evaluation was stopped.

(Example 5)
28 parts of 1.5 parts of styrene-maleic anhydride oligomer (acid value = 285 KOH mg / g, weight average molecular weight = 9,500; SMA 3000: manufactured by Sartomer) per 100 parts of copolymer latex A (solid content) An aqueous solution having a solid content concentration of 50% obtained by complete neutralization with an aqueous ammonia solution was added to obtain a copolymer latex composition A1.
While stirring the latex composition with respect to 100 parts of the copolymer latex composition A1 (solid content), 2 parts of an antifoaming agent (SM5515: manufactured by Toray Dow Corning Silicone Co., Ltd.), 240 parts of calcium carbonate And 60 parts of titanium oxide were added to prepare a blend. Subsequently, 10 parts of methanol and 17 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (CS-12: manufactured by Chisso Corporation) were added to the blend, and an aqueous coating composition was added. Got. The pH of the coating composition was adjusted to 10.5 using a 28% aqueous ammonia solution.
The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of the aqueous coating composition were measured, and the results are shown in Table 2.

(Example 6)
Instead of copolymer latex A, copolymer latex B was used, except that SMA 2625 (acid value = 220 KOH mg / g, weight average molecular weight = 9000, manufactured by Sartomer) 1.5 parts was used instead of SMA 3000. Were mixed in the same manner as in Example 5 to obtain an aqueous coating composition. The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of this aqueous coating composition were measured, and the results are shown in Table 2.

(Example 7)
An aqueous coating composition was obtained by blending in the same manner as in Example 6 except that the copolymer latex C was used instead of the copolymer latex B. The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of this aqueous coating composition were measured, and the results are shown in Table 2.

(Example 8)
An aqueous coating composition was obtained by blending in the same manner as in Example 6 except that the copolymer latex D was used in place of the copolymer latex B and the number of parts used of SMA2625 was changed to 1.6 parts. The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of this aqueous coating composition were measured, and the results are shown in Table 2.

(Comparative Example 4)
An aqueous coating composition was obtained by blending in the same manner as in Example 1 except that the copolymer latex E was used instead of the copolymer latex A. The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of this aqueous coating composition were measured, and the results are shown in Table 2.

(Comparative Example 5)
An aqueous coating composition was obtained by blending in the same manner as in Example 8 except that the copolymer latex F was used instead of the copolymer latex D. The storage stability, mechanical stability, initial drying property, tire adhesion, water resistance and alkali resistance of the coating film of this aqueous coating composition were measured, and the results are shown in Table 2.

Table 2 shows the following.
When copolymer latex E obtained by copolymerizing a monomer mixture in the presence of an anionic surfactant usually used in emulsion polymerization is used, initial drying properties of the paint, tire adhesion, and coating film Inferior in water resistance and alkali resistance of the coating film (Comparative Example 4).
When the copolymer latex F not containing an acid group-containing monomer is used, the blending stability with the pigment is low, and a paint that is stable enough to be evaluated cannot be obtained (Comparative Example 5).
For this comparative example, an aqueous paint obtained by using copolymer latexes A to D within the scope of the present invention obtained by copolymerizing a specific amount of an acid group-containing monomer using the amphoteric emulsifier defined in the present invention. The composition is excellent in storage stability, mechanical stability, initial drying property and tire adhesion, and the coating film is also excellent in water resistance and alkali resistance (Examples 5 to 8).

Claims (10)

Two types characterized in that the maximum value of pH titration inflection point is in the range of pH 8 to 9.5 and pH 9 to 10.5, respectively, and the difference in maximum value of pH titration inflection point is 0.5 or more In the presence of an amphoteric surfactant, an acid group-containing monomer and a copolymer thereof can be copolymerized in an aqueous phase having a pH value that is one lower than the maximum pH titration inflection point maximum value of the amphoteric surfactant. A copolymer latex containing a copolymer obtained by copolymerizing a monomer mixture comprising other monomers. The copolymer latex according to claim 1, wherein the ratio of the amphoteric surfactant having a maximum pH titration inflection point of pH 9 to 10.5 to 10 to 95 wt% relative to the total amphoteric surfactant. The copolymer latex according to claim 1 or 2, wherein the amount of the amphoteric surfactant used is 0.3 to 5 parts by weight per 100 parts by weight of the monomer mixture. The copolymer latex according to claim 1, wherein the amount of the acid group-containing monomer used is 0.1 to 5% by weight of the total amount of the monomer mixture. The copolymer latex according to any one of claims 1 to 4, wherein a glass transition temperature of the copolymer constituting the copolymer latex is -5 to + 50 ° C. The copolymer latex according to claim 1, wherein the copolymer has a volume average particle diameter of 100 to 300 nm. A copolymer latex composition obtained by blending the copolymer latex according to any one of claims 1 to 6 with an acid group-containing oligomer having a weight average molecular weight of 1,000 to 50,000. An aqueous coating composition comprising the copolymer latex according to any one of claims 1 to 6 and a filler. An aqueous coating composition comprising the copolymer latex according to any one of claims 1 to 6, an acid group-containing oligomer having a weight average molecular weight of 1,000 to 50,000, and a filler. The water-based paint composition according to claim 8 or 9, which is a water-based road marking paint.