JP2008038115A - Acrylic aqueous emulsion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic aqueous emulsion capable of providing a coated film excellent in balance of blocking resistance and film-forming property and excellent also in flexibility. <P>SOLUTION: The acrylic aqueous emulsion is obtained by carrying out multi-stage emulsion polymerization of an ethylenic unsaturated monomer. In the aqueous emulsion, two or more kinds of polymers different in glass transition temperature (Tg) form different phase structure particles each composed of a central part (core) and an outside part (shell) and Tg of a polymer constituting the core part is higher by ≥10°C than Tg of a polymer constituting the shell part and the polymer constituting the core part are obtained from emulsion polymerization of a monomer system [I] having a specific composition and a polymer existing on outermost side of the polymer constituting the shell is obtained from emulsion polymerization of a monomer system [II] having a specific constitution. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an acrylic aqueous emulsion capable of forming a coating film having excellent performance in paints, base materials for building materials or finishing materials, and other coating materials.
The coating film formed from the acrylic aqueous emulsion of the present invention is excellent in the balance between blocking resistance and film-forming property, and is excellent in flexibility. In addition, blocking is a phenomenon in which the coating film adheres to the non-painted surface of the product or a cushioning material inserted between products when products coated with water-based paint are stacked, or the coating films adhere to each other. Refers to the phenomenon.

  Acrylic aqueous emulsion obtained by emulsion polymerization (hereinafter simply referred to as emulsion) is a raw material for water-based paints and various coating materials because the coating film formed by drying at room temperature or under heating exhibits relatively good durability. Many are used. Water-based paints are applied to various objects such as building materials, home appliances, and plastic products at the factory, but even if they are sufficiently dried after painting, many products are stacked or stacked under high temperature conditions. Therefore, when used in such a situation, the requirement for anti-blocking property is very strict. Blocking is greatly related to the glass transition temperature (Tg) of the polymer, and generally a coating film obtained by an emulsion having a low Tg and excellent film forming property (coating film forming property) remains tacky even after drying. The blocking property is inferior. On the other hand, in the case of an aqueous emulsion having a high Tg, although the coating film obtained by coating at a high temperature has excellent blocking resistance, film formation is difficult. Therefore, in order to obtain a good coating film without cracks, it is necessary to add a large amount of film forming aid. As a result, if the drying is insufficient, the film forming aid remains in the coating film. , Blocking occurs. Thus, since the blocking resistance and the film forming property are in a trade-off relationship, development of an emulsion having a high Tg and excellent blocking resistance and good film forming property is desired, and various studies have been conducted so far.

  However, there is currently no emulsion satisfying such requirements, and development of an emulsion having an excellent balance between blocking resistance and film-forming property is expected. As a technique for that purpose, Patent Document 1 and Patent Document 2 describe a technique in which the emulsion particles have a core part of a high Tg polymer and a shell part of a heterogeneous structure emulsion composed of a low Tg polymer. However, in the emulsion described in Patent Document 1, for example, MFT (minimum film forming temperature) is less than 40 ° C., and in order to obtain an emulsion having excellent film forming properties, the average Tg of the whole particles is 21 ° C. or less. For applications where the requirement for blocking resistance is very strict, Tg is low and unsuitable. Moreover, although the emulsion described in Patent Document 2 is excellent in film forming property, the ratio of the high Tg component is as small as 10 to 35% by mass, and is similarly unsuitable for applications where the requirement for blocking resistance is very severe. . Thus, in the conventional emulsion, in order to obtain an emulsion having a good film forming property, the proportion of the polymer having a Tg of 90 ° C. or higher is lowered, or the average Tg of the whole particle is lowered to sacrifice the blocking resistance. It was a thing.

JP 2000-355602 A JP 2003-226793 A

Thus, with conventional emulsions, it has been difficult to achieve both blocking resistance and film-forming properties at a high level. However, the level of demand in the industry in recent years has become increasingly severe, and even more There is a need for improvements. Furthermore, the flexibility of the coating film is an important factor governing the frost damage resistance of water-based paints and the like, but the object of the present invention is to solve the above-mentioned problems and to improve the flexibility of the coating film based on acrylic water. It is to provide an emulsion.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have optimized the polymer ratio of the core part and the shell part of the emulsion particles, thereby achieving a balance between blocking resistance and film formability. The inventors have found that an emulsion having excellent coating film flexibility can be obtained, and the present invention has been achieved.
That is, the first invention is an acrylic aqueous emulsion obtained by multi-stage emulsion polymerization of an ethylenically unsaturated monomer, comprising two or more types of polymers having different glass transition temperatures (Tg), and The polymer forms heterogeneous structure particles composed of a central part (core) and an outer part (shell), and the Tg of the polymer constituting the core part is 10 ° C. or more higher than the Tg of the polymer constituting the shell part, The polymer constituting the part is 50 to 94.9% by mass of an ethylenically unsaturated monomer (component A) having a homopolymer Tg of 90 ° C. or higher, and an ethylenically unsaturated monomer having a homopolymer Tg of less than 90 ° C. It is obtained by emulsion polymerization of a monomer system [I] consisting of 5 to 40% by mass of a monomer (B component) and 0.1 to 10% by mass of a carboxyl group-containing ethylenically unsaturated monomer (C component). Polymerization constituting The outermost polymer is obtained by emulsion polymerization of a monomer system [II] composed of A component 0 to 10% by mass, B component 80 to 100% by mass, and C component 0 to 10% by mass. The present invention relates to an acrylic aqueous emulsion characterized by
The second invention is the acrylic aqueous emulsion according to the first invention in which the polymer constituting the core part has a Tg of 70 ° C. or higher and the average Tg of the whole heterophasic structure particles is 40 ° C. or higher.
A third invention is the acrylic aqueous emulsion according to the first invention or the second invention, wherein the ratio of the core portion to the whole heterophasic structure particles is 35% by mass or more and 70% by mass or less.

  The coating film obtained from the acrylic aqueous emulsion of the present invention is excellent in the balance between blocking resistance and film-forming property, and also excellent in flexibility.

The present invention will be specifically described below.
The acrylic aqueous emulsion of the present invention can be obtained by a usual emulsion polymerization method. There is no restriction | limiting in particular regarding the method of emulsion polymerization, A conventionally well-known method can be used. That is, in a dispersion system in which an ethylenically unsaturated monomer, a surfactant, a radical polymerization initiator, and other additive components used as required in an aqueous medium are basic composition components, usually 60 to 90 ° C. In this method, the monomer component is subjected to emulsion polymerization under heating, and this step is repeated at least twice. As a method for supplying the monomer composition into the polymerization system, a monomer batch charging method in which monomers are charged in a batch, a monomer dropping method in which monomers are continuously dropped, a monomer And a pre-emulsion method in which water, an emulsifier and an emulsifier are mixed and emulsified in advance, and these are added dropwise, or a combination thereof.

  First, the definition of the core part and the shell part in the emulsion of the present invention. When the heterophasic structure particles are composed of three or more phases (three or more types of polymers), the emulsion is divided into two regions on the center side and the outer side. The region including the polymer located at the center is defined as the core portion, and the outer region other than the core portion including the polymer positioned at the outermost side is defined as the shell portion. There is no restriction | limiting in particular about the method of area | region division, and Tg when a core part or a shell part is comprised by 2 or more phases shall use an average value.

In the emulsion of the present invention, the polymer constituting the core part of the heterophasic structure particles is obtained by emulsion polymerization of the monomer system [I], but the ratio of the A component in the monomer system [I] is increased to reduce the core part. The higher the Tg of the constituting polymer, the better the blocking resistance of the resulting coating film. A specific value of Tg is 50 ° C. or higher, preferably 60 ° C. or higher, and more preferably 70 ° C. or higher. The upper limit is 130 ° C. or lower, preferably 120 ° C. or lower.
The amount of the A component necessary for obtaining the high Tg polymer in the core portion varies depending on the homopolymer Tg and the amount of the B component and the C component in the monomer system [I], but specifically, 50% by mass or more. , Preferably it is 60 mass% or more, More preferably, it is 70 mass% or more.
By the way, if the amount of the component A is excessively increased, the polymerization stability is deteriorated and a large amount of aggregates may be generated. Specifically, the content is preferably 94.9% by mass or less.
The amount of the B component used for obtaining the high Tg polymer of the core portion varies depending on the homopolymer Tg and the amount of the A component and the C component in the monomer system [I]. Since Tg of coalescence can be increased, specifically, it is 5% by mass or more and 40% by mass or less, preferably 5% by mass or more and 35% by mass or less, and more preferably 5% by mass or more and 30% by mass or less.

In the present invention, it is essential that the monomer system [I] contains a carboxyl-containing ethylenically unsaturated monomer as a component C when emulsion-phase heterogeneous structure particles are subjected to emulsion polymerization. By containing C component, the softness | flexibility of the coating film obtained from the acrylic aqueous emulsion of this invention improves. The amount of component C is specifically 0.1% by mass or more and 10% by mass or less, preferably 0.3% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less. . In addition, the amount of the C component in the monomer system [II] affects the drying speed of the coating film surface. When there is no or little C component, depending on the composition of the aqueous paint to be prepared, Since drying may proceed rapidly and cracks may occur, the content is preferably 0% by mass or more and 10% by mass or less.
On the other hand, the outermost polymer among the polymers constituting the shell is obtained by emulsion polymerization of the monomer system [II]. The lower the Tg, the better the film-forming property. As a value, it is less than 40 degreeC, Preferably it is less than 30 degreeC, More preferably, it is less than 20 degreeC. The lower limit is −80 ° C. or higher, preferably −70 ° C. or higher.

Here, in the present invention, it is essential that the ratio of the component A in the monomer system [II] is 0% by mass or more and 30% by mass or less. By setting the ratio of the component A to 30% by mass or less, an acrylic aqueous emulsion having excellent film forming properties can be obtained.
The ratio of the B component in the monomer system [II] is 60% by mass or more and 100% by mass or less, and preferably 70% by mass or more and 99% by mass or less.
The average Tg of the entire heterophasic structure particles greatly affects the blocking resistance and film forming property. When the temperature is lower than 40 ° C., the film forming property is good, but it is not suitable when the requirement for blocking resistance is severe. is there. In order to obtain an emulsion having good blocking resistance, the average Tg of the whole heterophasic structure particles is preferably 40 ° C. or higher. The upper limit is 80 ° C. or lower, preferably 70 ° C. or lower.

  The ratio of the core part to the shell part in the heterophasic structure particles is not particularly limited as long as the Tg of the core part and the whole particle is within the above temperature range, but the blocking resistance deteriorates if the ratio of the core part is low. Specifically, it is preferably 35% by mass or more. On the other hand, if the ratio of the core part is increased too much, the blocking resistance is improved, but the shell part composed of a polymer having a low Tg is reduced and the film formability is deteriorated. As a result, the amount of the film-forming aid added is increased, leading to a decrease in blocking resistance. Therefore, the core portion ratio is preferably 70% by mass or less.

Here, the Tg of the polymer shown in the present invention is obtained experimentally or by calculation. Experimentally, it can be measured by performing dynamic viscoelasticity measurement or differential scanning calorimetry (DSC) of the polymer. In the calculation, the generally known Fox formula: 1 / Tg = W1 / Tg1 + W2
/ Tg2 + ... + Wn / Tgn (W1, W2,..., Wn Is the mass fraction of each polymerizable monomer, Tg1, Tg2, ..., Tgn Can be obtained from the homopolymer Tg (K: absolute temperature) of each polymerizable monomer. At this time, the Tg of the homopolymer used for the calculation is described in, for example, the polymer handbook (John Willy & Sons). In addition, Table 1 shows the homopolymer Tg of each monomer used in Examples and Comparative Examples.

The ethylenically unsaturated monomers of component A and component B used in the present invention are monomers that do not contain a carboxyl group. Specific examples include (meth) acrylic acid ester monomers and aromatic monomers. Body, hydroxyl group-containing monomer, amide group-containing monomer, epoxy group-containing monomer and the like.
Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and benzyl acrylate. , Phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl acrylate, butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and phenyl methacrylate. Preferred are butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate.

  Examples of the aromatic monomer include styrene, vinyl toluene, α-methyl styrene, and the like. Styrene is preferred. Examples of the hydroxyl group-containing monomer include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, polyethylene glycol acrylate, and polyethylene glycol methacrylate. Preferred are hydroxyethyl acrylate and hydroxyethyl methacrylate.

Examples of the amide group-containing monomer include acrylamide, methacrylamide, N, N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, N-methylol acrylamide, N-methylol methacrylamide, N- Mention may be made of methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide and the like. Preferred are acrylamide, methacrylamide, and diacetone acrylamide.
Examples of the epoxy group-containing monomer include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methyl glycidyl acrylate, and methyl glycidyl methacrylate. Glycidyl methacrylate is preferred.

  In addition to these monomers, monomer components other than those described above can be further used in order to improve various qualities and physical properties required for the acrylic aqueous emulsion of the present invention. As these monomers, other ethylenically unsaturated monomers copolymerizable with the above monomers can be used. For example, various monomers having functional groups such as amino group, sulfonic acid group, and phosphoric acid group, as well as vinyl acetate, vinyl propionate, vinyl versatic acid, vinyl pyrrolidone, methyl vinyl ketone, butadiene, ethylene, propylene, Vinyl chloride, vinylidene chloride and the like can be used as desired.

Specific examples of the carboxyl-containing ethylenically unsaturated monomer of component C include, for example, monocarboxylic acids such as acrylic acid, methacrylic acid, itaconic acid half ester, maleic acid half ester, and fumaric acid half ester. Examples of the dicarboxylic acid include itaconic acid, maleic acid, and fumaric acid. Acrylic acid, methacrylic acid and itaconic acid are preferred.

The surfactant used in the present invention refers to a compound having at least one hydrophilic group and one or more lipophilic groups in one molecule.
Examples of the surfactant include non-reactive alkyl sulfate, polyoxyethylene alkyl ether sulfate, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, and naphthalene sulfonate formalin. Anionic surfactants such as condensates, polyoxyethylene polycyclic phenyl ether sulfates, polyoxyethylene distyrenated phenyl ether sulfates, fatty acid salts, alkyl phosphates, polyoxyethylene alkylphenyl ether sulfates Non-reactive polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyethylene disty Phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, alkylalkanolamide, polyoxyethylene alkylphenyl ether, etc. Nonionic surfactants.
In addition to these, a so-called reactive surfactant in which an ethylenic double bond is introduced into the chemical structural formula of a surfactant having a hydrophilic group and a lipophilic group may be used.

  Among the reactive surfactants, the anionic surfactant is, for example, an ethylenically unsaturated monomer having a sulfonic acid group, a sulfonate group or a sulfate ester group and a salt thereof, a sulfonic acid group, or an ammonium thereof. A compound having a group (ammonium sulfonate group or alkali metal sulfonate group) which is a salt or an alkali metal salt is preferable. For example, alkylallylsulfosuccinate (for example, Sanyo Kasei Co., Ltd., Eleminol (trademark) JS-2, JS-5 etc.), for example, polyoxyethylene alkylpropenyl phenyl ether sulfate (for example, Daiichi Kogyo Seiyaku Co., Ltd.) Manufactured by Aqualon (trademark) HS-10), for example, α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-polyoxyethylene sulfate ester salt (for example, Asahi Denka Kogyo Co., Ltd.) Adeka Soap (trademark) SE-1025N, etc.), for example, ammonium-α-sulfonato-ω-1- (allyloxymethyl) alkyloxypolyoxyethylene (for example, Aqualon manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Styrene sulfonates such as KH-10).

Examples of the reactive surfactant and nonionic surfactant include α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxypolyoxyethylene (for example, Asahi Denka Kogyo ( Adekaria soap NE-20, NE-30, NE-40, etc.), for example, polyoxyethylene alkylpropenyl phenyl ether (for example, Aqualon RN-10, RN-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) RN-30, RN-50, etc.).
The amount of the surfactant is preferably 0.1 to 5% by mass with respect to 100 parts by mass of the monomer composition.

The radical polymerization initiator used in the present invention is one that initiates addition polymerization of a monomer by radical decomposition with heat or a reducing substance, and any of inorganic initiators and organic initiators can be used. As such, water-soluble and oil-soluble polymerization initiators can be used.
Examples of water-soluble polymerization initiators include peroxodisulfates, peroxides, water-soluble azobis compounds, peroxide-reducing agent redox systems, and the like. Peroxodisulfates include, for example, potassium peroxodisulfate ( KPS), sodium peroxodisulfate (NPS), ammonium peroxodisulfate (APS) and the like. Examples of peroxides include hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxymaleic acid, and succinic acid peroxide. Examples of water-soluble azobis compounds include 2,2-azobis (N-hydroxyethylisobutyramide), 2,2-azobis (2-amidinopropane) dihydrochloride, 4,4- Azobis (4-cyanopentanoic acid) and the like. Examples of the dox system include sodium sulfooxylate formaldehyde, sodium bisulfite, sodium thiosulfate, sodium hydroxymethanesulfinate, L-ascorbic acid, and salts thereof, cuprous salts and ferrous salts. A reducing agent such as can also be used in combination with the polymerization initiator.
As a usage-amount of a radical polymerization initiator, it is good to set it as 0.05-1 mass% of radical polymerization initiators with respect to 100 mass parts of monomer compositions.

In the present invention, hydrolyzable silane may be added during emulsion polymerization for the purpose of improving the gloss retention when the coating film obtained by drying the emulsion is exposed outdoors for a long time. The hydrolyzable silane is one that hydrolyzes and condenses with an acid catalyst or an alkali catalyst to form an organopolysiloxane, and has, for example, a silicone structure represented by the following formula (1).
(R1) n-Si- (R2) 4-n (1)
(In the formula, n is an integer of 0 to 3, R1 is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 16 carbon atoms, an aryl group having 5 to 10 carbon atoms, a cycloalkyl group having 5 to 6 carbon atoms, vinyl. Selected from a group, an acryloxyalkyl group having 1 to 10 carbon atoms, or a methacryloxyalkyl group having 1 to 10 carbon atoms, n R1s may be the same or different, and R2 may have 1 to 1 carbon atoms. 8 is selected from an alkoxy group, an acetoxy group, or a hydroxyl group. 4-n R2s may be the same or different.

Hydrolyzable silanes are roughly classified into those having radically polymerizable double bonds and those having no radically polymerizable double bonds.
Specific examples of the polymerizable hydrolyzable silane include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, and γ-methacryloxypropyltrimethoxysilane. , Γ-methacryloxypropyltriethoxysilane and the like. Preferred are γ-methacryloxypropyltrimethoxysilane and γ-methacryloxypropyltriethoxysilane.

  Specific examples of non-polymerizable hydrolyzable silanes include, for example, dimethyldimethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, methyl Examples include triethoxysilane and phenyltriethoxysilane. Preferred are dimethyldimethoxysilane, diphenyldimethoxysilane, methyltrimethoxysilane, and phenyltrimethoxysilane.

Other non-polymerizable hydrolyzable silanes include cyclic silanes, such as octamethylcyclotetrasiloxane, octaphenylcyclosiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, tetramethyltetravinylcyclotetrasiloxane. , And polysiloxane.
These hydrolyzable silanes may contain one or more kinds. By using these hydrolyzable silanes, the emulsion of the present invention can be used.

The addition method of hydrolyzable silane is not specifically limited. For example, a method of adding separately from the monomer composition, a method of adding in advance to the monomer composition, a method of adding in advance to the emulsion of the monomer composition, a monomer composition And a method of mixing and adding the above emulsion to the reactor. Since there is no problem in the stability of emulsion polymerization, it is a method of mixing and adding the emulsion of the monomer composition to the reactor. Hydrolyzable silane is present during emulsion polymerization, so that hydrolysis and subsequent condensation reaction proceed.
The hydrogen ion concentration (pH) of the emulsion polymerization system during the emulsion polymerization is not particularly limited, but it is preferably carried out at pH 4.0 or less. At pH 4.0 or less, the condensation reaction of hydrolyzable silane proceeds, and there is no problem in storage stability as a product. Particularly preferably, the pH is 1.5 to 3.0.

  In order to further promote the hydrolysis and condensation reaction of the hydrolyzable silane, for example, hydrochloric acid, methanesulfonic acid, p-toluenesulfonic acid, β-naphthalenesulfonic acid, 2-mesitylenesulfonic acid, camphor-10-sulfonic acid, three Boron fluoride or the like is used during emulsion polymerization. In particular, emulsion catalysts that use both an acid catalyst such as hexylbenzenesulfonic acid, octylbenzenesulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, and cetylbenzenesulfonic acid and a surfactant for emulsion polymerization are used. May be.

An ultraviolet absorber and / or a light stabilizer can be added to the aqueous resin dispersion of the present invention to improve durability. As UV absorbers, reactive ones that have radical polymerizable double bonds in the molecule and non-reactive ones that do not have radical polymerizable double bonds, radical stabilizers in the molecule as light stabilizers A reactive compound having a reactive double bond and a non-reactive compound having no radical polymerizable double bond can also be used.
In the present invention, as the ultraviolet absorber, it is preferable to use at least one selected from, for example, benzophenone series, benzotriazole series, triazine series, oxalic acid anilide series, cyanoacrylate series, benzoate series, and salicylate series. For example, it is preferable to use at least one selected from hindered amines having a 2,2,6,6-tetraalkylpiperidine skeleton.

  Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and 2-hydroxy as non-reactive ones. -4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 2, 2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2- Hydroxy-4-meth Shi-2'-carboxybenzophenone, 2-hydroxy-4-stearyloxy benzophenone.

  Examples of reactive benzophenone UV absorbers include 2-hydroxy-4-acryloxybenzophenone, 2-hydroxy-4-methacryloxybenzophenone, 2-hydroxy-5-acryloxybenzophenone, 2-hydroxy-5-methacryloxy. Benzophenone, 2-hydroxy-4- (acryloxy-ethoxy) benzophenone, 2-hydroxy-4- (methacryloxy-ethoxy) benzophenone, 2-hydroxy-4- (methacryloxy-diethoxy) benzophenone, 2-hydroxy-4- (acryloxy- And triethoxy) benzophenone.

Examples of the benzotriazole-based UV absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 2- (2′-hydroxy-5′-tert-butylphenyl) benzo as non-reactive. Triazole, 2- (2′-hydroxy-3 ′
, 5′-di-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-octylphenyl) benzo Triazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α′-dimethylbenzyl) phenyl] benzotriazole), methyl-3- [3-tert-butyl-5- (2H-benzotriazole) 2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (with a molecular weight of 300) (for example, product name: TINUVIN 1130, manufactured by Nippon Ciba-Geigy Co., Ltd.), isooctyl-3- [3- (2H -Benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl] Lopionate (for example, Nippon Ciba-Geigy Co., Ltd., product name: TINUVIN 384), 2- (3-dodecyl-5-methyl-2-hydroxyphenyl) benzotriazole (for example, Ciba-Geigy Co., Ltd., product name: TINUVIN 571) 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert) -Amylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6 '' -Tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetra Tilbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (eg, Japan) Ciba Geigy Co., Ltd., product name: TINUVIN900).

  Examples of reactive benzotriazole-based ultraviolet absorbers include 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole (for example, Otsuka Chemical Co., Ltd., product name: RUVA-93). 2- (2′-hydroxy-5′-methacryloxyethyl-3-tert-butylphenyl) -2H-benzotriazole, 2- (2′-hydroxy-5′-methacryloxypropyl-3-tert-) Butylphenyl) -5-chloro-2H-benzotriazole, 3-methacryloyl-2-hydroxypropyl-3- [3 ′-(2 ″ -benzotriazolyl) -4-hydroxy-5-tert-butyl] phenylpropi Honate (for example, product name: CGL-104 manufactured by Nippon Ciba-Geigy Co., Ltd.) It is.

  Examples of the triazine-based ultraviolet absorber include, for example, 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2, 4-dimethylphenyl) -1,3,5-triazine and 2- [4-[(2-hydroxy-3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4- Dimethylphenyl) -1,3,5-triazine mixture (for example, product name: TINUVIN400 manufactured by Nippon Ciba-Geigy Co., Ltd.), 2,4-bis (2,4-dimethylphenyl) -6- (2- Hydroxy-4-iso-octylphenyl) -s-triazine (for example, product name: TINUVIN411L manufactured by Nippon Ciba-Geigy Co., Ltd.) .

As the hindered amine light stabilizer that can be used in the present invention, those having a low basicity are preferable, and specifically, those having a base constant (pKb) of 8 or more are preferable. For example, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis (2,2,6,6-tetramethylpiperidyl) sebacate, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, 1- [2- [3- (3,5-di- tert-butyl-4-hydroxyphenyl) propynyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propynyloxy] -2,2,6,6-tetramethyl A mixture of piperidine, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl-sebacate (eg Ciba Geigy Co., Ltd., product name: TINUVIN292), bis (1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate (for example, Ciba Geigy Japan Co., Ltd., product name: TINUVIN123).

Examples of reactive hindered amine light stabilizers include 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 1,2,2,6,6-pentamethyl-4-piperidyl acrylate, 2,2,6. , 6-tetramethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl acrylate, 1,2,2,6,6-pentamethyl-4-iminopiperidyl methacrylate, 2,2,6 , 6, -tetramethyl-4-iminopiperidyl methacrylate, 4-cyano-2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4-cyano-1,2,2,6,6-pentamethyl-4 -Piperidyl methacrylate and the like.
The ultraviolet absorber and / or the light stabilizer are not limited in the addition method such as being present at the time of emulsion polymerization, or being added after mixing with a film forming auxiliary agent. Preferably, it is present during emulsion polymerization. A preferable amount of the ultraviolet absorber and / or light stabilizer is 0.1 to 10 parts by mass of the ultraviolet absorber and / or light stabilizer with respect to 100 parts by mass of the total monomer composition.

In the emulsion of the present invention, in addition to the silicone modifier, ultraviolet absorber, and light stabilizer, components generally incorporated in water-based paints such as preservatives, film-forming aids, thickeners, antifoaming agents, freezing agents An inhibitor or the like can be optionally blended.
The emulsion of the present invention is preferably adjusted to a pH range of 5 to 10 using amines such as ammonia, sodium hydroxide, potassium hydroxide and dimethylaminoethanol in order to maintain long-term dispersion stability. The acrylic emulsion of the present invention preferably has a dispersoid average particle size of 10 to 1000 nm.
In the emulsion of the present invention, components that are usually added to and blended with water-based paints, for example, film forming aids, thickeners, antifoaming agents, pigments, dispersants, dyes, preservatives and the like may be arbitrarily blended. it can.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited at all by these examples. In addition, the part and% in an Example and a comparative example show a mass part and mass%, respectively. Moreover, about the physical-property test of the obtained acrylic aqueous emulsion, the coating material was adjusted with the compounding composition shown below, and the test was implemented according to the test method shown below.

・ Preparation of clear paint for tensile test Emulsions of Examples and Comparative Examples (solid content conversion) 50 parts Ethylene glycol monobutyl ether 5 parts Water 5 parts CS-12 (manufactured by Chisso Corporation) 10 parts

・ Preparation of clear paint for blocking resistance evaluation Example and comparative emulsion (solid content conversion) 50 parts Ethylene glycol monobutyl ether See Evaluation Method

<Evaluation method>
・ Measurement of the solid content rate About 1 g of the emulsion obtained in the examples and comparative examples was accurately weighed in an aluminum dish with a known mass in advance, dried at 105 ° C. for 3 hours with a dryer, and then silica gel was added. Weigh after cooling in a desiccator for 30 minutes. The value obtained by dividing the mass of the dried product by the mass before drying was defined as the solid content.

-Measurement of particle diameter The average particle diameter of the emulsion obtained by the Example and the comparative example was measured using the particle size distribution analyzer UPA150 made from Leeds & Northrup. Table 3 shows the volume average particle diameter as one of the measured values.

・ Evaluation of film formability: Measurement of MFT (minimum film formation temperature) The emulsions of Examples and Comparative Examples were applied with a thickness of 0.1 mm on the temperature gradient plate of the MFT measuring apparatus, and the measured MFT values were as follows: Evaluation based on the criteria. Table 3 shows the evaluation results of the MFT value and film formability. Δ or more is a pass line.
A: MFT is less than 25 ° C. ○: MFT is 25 ° C. or more and less than 40 ° C. Δ: 40 ° C. or more and less than 50 ° C. ×: 50 ° C. or more

Evaluation of blocking resistance The emulsions of Examples and Comparative Examples were blended with ethylene glycol monobutyl ether as a film forming aid so that the MFT was in the range of 10 to 15 ° C., and a clear paint for evaluation was prepared. This was coated on a glass plate with a thickness of 0.1 mm and naturally dried for 1 hour in a thermostatic chamber (room temperature 23 ° C., humidity 50%). Next, after drying for 5 minutes with a drier at a set temperature of 100 ° C., 4 sheets of gauze cut into 5 cm squares were placed on the coated surface, and a load of 0.1 MPa was applied in a drier at 40 ° C. for 16 hours. After removing from the dryer and returning to room temperature, the load was removed, the gauze was slowly peeled off, and the state of the coating film surface was visually observed. The evaluation criteria are as follows, and the evaluation results are shown in Table 3. Δ or more is a pass line.
A: There is almost no trace of gauze.
○: A trace of gauze is seen.
Δ: Reticulated traces.
×: Difficult to peel off gauze

-Flexibility evaluation: Clear coating tensile test Apply the above clear coating for tensile test to a glass plate with a thickness of 0.25 mm and let it naturally dry for 3 hours under conditions of room temperature 23 ° C and humidity 50%. It was. The obtained coating film was cut into a 10 mm × 80 mm strip, dried for 7 days in a dryer at 50 ° C., cured for 1 day in the temperature-controlled room, and then installed in the temperature-controlled room. Using a Tensilon tensile tester RTC-1250A, the distance between chucks was set to 50 mm, the elongation of the coating film was measured, and the results were evaluated according to the following criteria. Table 3 shows the measurement results and the evaluation results of the flexibility. Δ or more is a pass line.
◎: Elongation 100% or more ○: Elongation 50% or more and less than 100% △: Elongation 20% or more and less than 50% ×: Elongation 20% or less

[Example 1]
Two-stage emulsion polymerization was performed in which the core part of the heterophasic structure particles was formed by the first stage emulsion polymerization and the shell part was formed by the second stage emulsion polymerization. First, as a first stage, 449 parts of water and 3.2 parts of Aqualon KH-1025 (Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier and Adekaria are installed in a reaction vessel equipped with a stirrer, reflux condenser, dropping tank and thermometer. 3.2 parts of Soap SR-1025 (Asahi Denka Kogyo Co., Ltd.) was added and the reaction vessel was heated. When the liquid temperature in the reaction vessel reached 80 ° C., 12 parts of 2% aqueous ammonium persulfate solution was added. After 5 minutes, the monomer system [I] emulsion (average calculation Tg 101 ° C.) having the composition shown in Table 2 was dropped from the dropping tank over 105 minutes. During the dropping, the liquid temperature in the reaction vessel was kept at 80 ° C. After completion of the dropping, 17.5 parts of water was put into the container containing the emulsified liquid, and the bottom surface of the container was simply rinsed, and the rinse liquid was put into the reaction container and kept at 80 ° C. for 30 minutes.

  As a 2nd step, the monomer system [II] emulsion (average calculation Tg 0 degreeC) of the composition shown in Table 2 was dripped over 90 minutes from the dripping tank. During the dropping, the temperature of the reaction vessel is kept at 80 ° C. After the dropping is completed, 17.5 parts of the container rinsing liquid is put into the reaction vessel in the same manner as in the first stage, and the liquid temperature is kept at 80 ° C. for 60 minutes. 72 parts of water was added and cooled to room temperature. About the obtained emulsion, 25% ammonia water was added to adjust the pH to 8.5, and then the above evaluation was performed. The results are shown in Table 3. Further, Table 3 also shows values representing the ratio of each monomer in the monomer systems [I] and [II] in percentage.

[Example 2]
In the composition of the monomer system [II] in Example 1, cyclohexyl methacrylate was changed to butyl methacrylate, and everything was the same as in Example 1 except that the composition ratio was changed so that the average calculated Tg was 0 ° C. The emulsion was subjected to emulsion polymerization, and the obtained emulsion was evaluated in the same manner. The results are shown in Table 3.

[Example 3]
Emulsion polymerization was performed in the same manner as in Example 1 using the monomer system [I] and [II] emulsions having the compositions shown in Table 2, and the obtained emulsions were evaluated in the same manner. The results are shown in Table 3.
[Examples 4 and 5]
In the composition of the monomer system [I] in Example 3, all the emulsion polymerization was carried out in the same manner as in Example 3 except that the composition ratio of methyl methacrylate and cyclohexyl methacrylate was changed. Went. The results are shown in Table 3.

[Comparative Examples 1 and 2]
In the composition of the monomer system [I] in Example 1, emulsion polymerization was performed in the same manner as in Example 1 except that the composition ratio of methyl methacrylate and cyclohexyl methacrylate was changed. Went. Although the result is shown in Table 3, although the flexibility of the coating film is excellent, the film formability is very inferior, and the MFT cannot be measured at a normal temperature setting (high temperature side 80 ° C. setting). Since the amount of film-forming auxiliary (ethylene glycol monobutyl ether) to be added increases, the blocking resistance is not good.

[Comparative Example 3]
In the composition of the monomer system [II] in Example 1, cyclohexyl methacrylate was changed to methyl methacrylate and the composition ratio was changed so that the average calculation Tg was the same 0 ° C. The emulsion was subjected to emulsion polymerization, and the obtained emulsion was evaluated in the same manner. The results are shown in Table 3. As the MMA ratio in the monomer system [II] is as high as 38.9%, the film formability is inferior.

[Comparative Example 4]
In the composition of the monomer system [I] in Example 3, emulsion polymerization was performed in the same manner as in Example 3 except that the amount of acrylic acid was 0, and the obtained emulsion was evaluated in the same manner. . The results are shown in Table 3. Since the monomer system [I] does not contain a carboxyl group-containing monomer, the flexibility of the coating film is poor.

[Comparative Example 5]
In the composition of the monomer system [I] in Example 4, emulsion polymerization was performed in the same manner as in Example 4 except that the amount of acrylic acid was 0, and the obtained emulsion was evaluated in the same manner. . The results are shown in Table 3. Since the monomer system [I] does not contain a carboxyl group-containing monomer, the coating film has poor flexibility.

[Comparative Example 6]
In the composition of the monomer system [I] in Example 5, emulsion polymerization was performed in the same manner as in Example 5 except that the amount of acrylic acid was 0, and the obtained emulsion was evaluated in the same manner. . The results are shown in Table 3. Since the monomer system [I] does not contain a carboxyl group-containing monomer, the coating film has poor flexibility.

  The acrylic emulsion of the present invention is useful as a coating material, a base treatment material or finishing material for building materials, an adhesive, a paper processing agent, or a finishing material for woven or non-woven fabrics. In particular, as a finishing material for paints and building materials, concrete materials such as concrete, cement mortar, slate plates, calcium plates, gypsum boards, extruded plates, foamed concrete, and building materials based on woven or non-woven fabrics. As a paint or building finishing material for various bases such as metal building materials, composite materials such as main materials and top coats for multi-layer finishing coating materials, thin finish coating materials, thick finish coating materials, stone finish materials, gloss paints, etc. It is useful as a resin emulsion paint, metal paint, wood paint, and tile paint.

Claims (3)

An aqueous emulsion obtained by multistage emulsion polymerization of an ethylenically unsaturated monomer, comprising two or more types of polymers having different glass transition temperatures (Tg), and the polymer comprises a central portion (core) The Tg of the polymer constituting the core part is 10 ° C. higher than the Tg of the polymer constituting the shell part, and the polymer constituting the core part is shown below. It is obtained by emulsion polymerization of the monomer system [I] shown, and the outermost polymer among the polymers constituting the shell part is obtained by emulsion polymerization of the monomer system [II] shown below Acrylic aqueous emulsion.
[I]: A monomer system in which the A component is 50 to 94.9% by mass, the B component is 5 to 40% by mass, and the C component is 0.1 to 10% by mass.
[II]: A monomer system in which the A component is 0 to 30% by mass, the B component is 60 to 100% by mass, and the C component is 0 to 10% by mass.
However, the A to C components are as shown below.
Component A; an ethylenically unsaturated monomer having a homopolymer Tg of 90 ° C. or higher.
Component B: an ethylenically unsaturated monomer having a homopolymer Tg of less than 90 ° C.
Component C: a carboxyl group-containing ethylenically unsaturated monomer.   2. The acrylic aqueous emulsion according to claim 1, wherein the polymer constituting the core part has a Tg of 70 ° C. or higher and the average Tg of the whole heterophasic structure particles is 40 ° C. or higher.   The acrylic aqueous emulsion according to claim 1 or 2, wherein the ratio of the core portion to the whole of the heterophasic structure particles is 35% by mass or more and 70% by mass or less.