JPH0827347A - Alkoxysilyl-containing acrylic emulsion - Google Patents

Abstract

PURPOSE:To obtain an acrylic emulsion improved in long-term storage stability, durability, weathering resistance, etc., by emulsion-polymerizing a specified core-forming monomer component with a shell-forming monomer component in the presence of a reactive surfactant. CONSTITUTION:A mixture (A) containing 50-99wt.% alkyl (meth)acrylate with a 1-18C alkyl group, 1-20wt.% organosilicon compound represented by the formula (wherein R<1> is a monovalent organic group having a polymerizable double bond; R<2> is a 1-4C alkyl; X is a 1-4C alkoxyl; and (n) is 2 or 3) and 0-30wt.% comonomers is polymerized in water at 10-90 deg.C and at a pH of 6.5-7.5 to obtain a core polymer emulsion. A mixture (B) comprising 70- -100wt.% alkyl (meth)acrylate with a 1-18C alkyl group and 0-30wt.% comonomers is added to the above emulsion in amounts to give component (A)/component (B) weight ratio of 50/50 to 90/10, and the resulting mixture is emulsion-polymerized in the presence of a reactive surfactant.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an acrylic emulsion having a hydrolyzable alkoxysilyl group,
The present invention relates to an acrylic emulsion which has good long-term storage stability, excellent durability and weather resistance of a film formed from the emulsion, and is useful as a base emulsion for paints and sealants.

[0002]

2. Description of the Related Art Water resistance for coating agents such as paints,
Durability and weather resistance including acid resistance, alkali resistance, and moisture resistance are required, and it is well known that a solution type hydrolyzable silyl group-containing room temperature curable polymer is used as one of the countermeasures. As this polymer,
Examples thereof include polymers obtained by solution polymerization having a number average molecular weight of 300 to 30,000 in which silyl groups having at least two hydrolyzable groups are introduced into one molecule. However, in recent years, from the viewpoints of low pollution, resource saving, and safety and hygiene, these coating agents are also required to be an emulsion type that is water-based, but the hydrolyzable silyl group easily hydrolyzes and condenses in water, and storage stability It was difficult to produce an emulsion type with good properties.

JP-A-5-25354 discloses that a hydrolyzable silyl group and an amine imide group are each added to improve storage stability.
A reactive resin emulsion containing a resin having at least one in the molecule has been proposed. For its production, a method in which solution polymerization is carried out in an organic solvent and then the solution is topped to emulsify the remaining resin, or a solution A method of adding water as it is, emulsifying it, and then topping is adopted, and the process is complicated and an economic disadvantage cannot be avoided. In addition, the condensation reaction of the hydrolyzable silyl group during storage was not sufficiently prevented, and gelation of the emulsion was not observed after long-term storage, but intra-particle cross-linking was caused by condensation of the hydrolyzable silyl group in the emulsion particles. However, there is a problem in that the film-forming property of the emulsion deteriorates and it becomes difficult to form a good film at room temperature.

[0004]

Under the circumstances as described above, the present invention provides a film which is excellent in long-term storage stability and film forming property and is formed by remarkably reducing intra-particle crosslinking by alkoxysilyl groups. The present invention has been made to provide an acrylic emulsion containing an alkoxysilyl group having excellent durability.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that an alkoxysilyl group is contained in a raw material monomer of a polymer forming a core part of emulsion particles. Emulsion polymerization using a reactive surfactant without adding a monomer containing an alkoxysilyl group to the raw material of the polymer forming the outer shell (shell) part. It was found that a specific core-shell type alkoxysilyl group-containing acrylic emulsion has the potential to solve problems, and further tested for the type and amount of monomer and reactive surfactant in each part of the core and shell. The present invention has been carried out.

The present invention has solved the above-mentioned problems, and the present invention is a core-shell type emulsion in which the composition of the core and the outer shell of the emulsion particles are different, and the core portion thereof is (A) Alkyl ester of (meth) acrylate having an alkyl group having 1 to 18 carbon atoms 50 to 99% by weight (b) Formula R ¹ R ² _(3-n) SiX _n (wherein R ¹ Is a monovalent organic group having a polymerizable double bond, R ² is an alkyl group having 1 to 4 carbon atoms, X is an alkoxyl group having 1 to 4 carbon atoms, and n is an organic silicon compound represented by 2 or 3). ~ 20% by weight (c) 0 to 30% by weight of a monomer copolymerizable with the above (a) and (b) [however, the total of (a), (b) and (c) is 100% by weight] And (A) alkyl methacrylic acid having an alkyl group having 1 to 18 carbon atoms in the shell part 70 to 100% by weight (B) 0 to 30% by weight of a monomer copolymerizable with (A) [however, the total of (A) and (B) is 100% by weight] ( II), the ratio of which is (I) / (I
I) = 50/50 to 90/10 (weight ratio), and a core / shell type alkoxysilyl group-containing acrylic emulsion obtained by emulsion polymerization using a reactive surfactant,
It is the gist. The present invention will be described in more detail below.

The (meth) acrylic acid alkyl ester which is the component (a) and (A) in the present invention is a main component monomer for forming the skeleton of an acrylic polymer, and is a direct monomer having 1 to 18 carbon atoms. It is an ester compound of an alcohol having a chain or branched alkyl group or an alcohol having a cyclic alkyl group with acrylic acid or methacrylic acid. Examples of this monomer include methyl or ethyl of acrylic acid or methacrylic acid, propyl, isopropyl, butyl,
Isobutyl, octyl, 2-ethylhexyl, lauryl,
Examples thereof include stearyl or cyclohexyl ester, and one or a mixture of two or more selected from these groups can be used.

The formula of the component (b) R ¹ R ² _(3-n) SiX _n (wherein
The organic silicon compound represented by R ¹ , R ² , X and n is the same as described above) is a monomer for introducing an alkoxysilyl group into the acrylic polymer as a side chain. Examples of this monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ. Examples thereof include acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane and γ-methacryloxypropyltributoxysilane. One kind or a mixture of two or more kinds of these monomers is used as 1) to 20% by weight of the total amount of the monomer component (I) as the component (b) when polymerizing the core part. If it is less than 1% by weight, the cross-linking density of the formed film is low and the durability such as water resistance and the weather resistance are insufficient, and 20
When the content is more than 10% by weight, the crosslinking density is too high, the formed film becomes brittle, and the storage stability of the emulsion is impaired.

The component (c) is a polymerizable monomer copolymerizable with the components (a) and (b), and the component (B) is a polymerizable monomer copolymerizable with the component (A). . These monomers are used for the mechanical stability of the emulsion, the water resistance of the formed film, the gloss, and the addition of other functions, if necessary, but they do not impair the object of the present invention. The component is used in an amount of 30% by weight or less based on the total amount of the monomer component (I), and the component (B) is used in an amount of 30% by weight or less based on the total amount of the monomer component (II).

As the monomer of the component (c) or the component (B), a monomer containing a carboxyl group such as acrylic acid, methacrylic acid, maleic anhydride or an anhydride thereof, 2
-Hydroxyethyl (meth) acrylate, hydroxyl group-containing monomer such as 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth)
Amide group-containing monomers such as acrylamide, N-butoxymethyl (meth) acrylamide and diacetone (meth) acrylamide, amino group-containing monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, methoxy Alkoxyl group-containing monomers such as ethyl (meth) acrylate and butoxyethyl (meth) acrylate, glycidyl (meth) acrylates, glycidyl group-containing monomers such as glycidyl allyl ether, divinylbenzene, allyl (meth) acrylate, ethylene glycol Monomers such as di (meth) acrylate, diethylene glycol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate having two or more radically polymerizable unsaturated groups in one molecule, vinyl acetate, propion Vinyl ester monomers such as vinyl, aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, halogens such as vinyl chloride and vinyl bromide. Examples thereof include vinyl chloride monomers, and among these, one kind or a mixture of two or more kinds is used.

Further, in order to remarkably improve the durability such as water resistance of the film formed from the emulsion of the present invention and obtain the performance close to that of the melt-polymerized product, the reactive surfactant is used as the surfactant (emulsifier). I found it to be good to use.
Examples of this reactive surfactant include:

[0012]

Embedded image

[0013]

Embedded image Anionic reactive surfactant such as, and

[0014]

Embedded image And the like, or a cation-type reactive surfactant containing a quaternary ammonium salt or a tertiary amine salt and a polymerizable group.

This reactive surfactant may be used alone or in combination of two or more, but if the amount is too small, a lot of agglomerates will be generated in the produced emulsion, and it will be obtained. The resulting coating also does not exhibit good physical properties.
Also, when the amount is too large, the particle size of the polymer becomes fine, the viscosity of the emulsion increases too much, and the water resistance of the film also deteriorates. Therefore, the amount of the reactive surfactant used is preferably 0.5 to 15% by weight, and more preferably 1 to 7% by weight, based on the total monomers.

Further, as long as the object of the present invention is not impaired, it is possible to use a non-reactive surfactant used in ordinary emulsion polymerization in combination with this reactive surfactant, and the total amount of the surfactant. It may be possible to use one kind or two or more kinds in a range of 30% by weight or less. These non-reactive surfactants include anionic surfactants such as alkyl or alkylallyl sulphates, alkyl or alkylallyl sulfonates and dialkyl sulfosuccinates, and cationic such as alkyl trimethyl ammonium chloride and alkyl benzyl ammonium chloride. Examples include surfactants, nonionic surfactants such as polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene carboxylic acid ester.

The radical polymerization initiator used in the present invention includes persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide solution, t-butyl hydroperoxide,
Water-soluble types such as azobisamidinopropane hydrochloride,
Benzoyl peroxide, cumene hydroperoxide, dibutyl peroxide, diisopropyl peroxydicarbonate, cumyl peroxy neodecanoate,
Examples include oil-soluble types such as cumyl peroxy octoate and azobisisobutyronitrile. Further, if necessary, a redox system in which a reducing agent such as acidic sodium sulfite, Rongalite, or ascorbic acid is used together can be used. The amount of the polymerization initiator used is usually 0.1 to 10% by weight with respect to the monomer, but preferably
It is 0.5 to 5% by weight.

In order to produce the alkoxy-silyl group-containing core-shell type acrylic emulsion of the present invention, first, the above-mentioned various monomers (a), (b) and (c) are mixed and the surface-active substance is added thereto. An emulsion forming a core part is polymerized in an aqueous system by adding an agent, a polymerization initiator and the like. In this case, various methods such as a batch polymerization method and a method of continuously supplying each component can be applied. At the time of polymerization of the core part, in order to suppress the hydrolysis and condensation of the alkoxysilyl group, it is preferable to use a pH buffer to keep the pH during the polymerization at 6.5 to 7.5. The polymerization is usually carried out at a temperature of 10 to 90 ° C. In core part polymerization, it is essential that the reactive surfactant is almost completely polymerized and does not substantially remain in the aqueous phase of the core part polymer emulsion. During the polymerization, new particles may be generated by the shell part monomer, and the effect of the present invention is diminished. Next, a polymerization initiator and the above-mentioned various monomers (A) and (B) are further added to this system and polymerized to form a shell part. At the end of emulsion polymerization, it is preferable to adjust the pH to 6-8 by adding a basic substance in order to prevent an undesirable crosslinking reaction of the polymer and to further improve the storage stability which is the object of the present invention. Examples of these substances include ammonia, amines, alkanolamines and caustic.

When the emulsion of the present invention is used for coatings and the like, the alkoxysilyl groups introduced into the polymer side chains in the emulsion particles are condensed by evaporation of water to form a crosslinked film. A reaction catalyst can be added to promote film formation by crosslinking. As the condensation reaction catalyst, organic titanate compounds such as isopropyl triisostearoyl titanate, isopropyl tri (dioctyl pyrophosphate) titanate, organic aluminum compounds such as acetoalkoxy aluminum diisopropylate, dibutyl tin dilaurate, dibutyl tin malate, dioctylic acid Carboxylic acid type tin compounds such as tin, dialkyltin compounds such as dibutyltin oxide, dioctyltin oxide, lead octylate, carboxylic acid metal salts such as cobalt naphthenate, acidic phosphoric acid esters, carboxylic acids and their acid anhydrides, triethylamine And amines such as dibutylamine-2-hexoate and salts thereof. These catalysts may be added as they are if they are water-soluble, but oil-soluble ones are preferably added in the form of an aqueous dispersion, and the addition amount is preferably 0.01 to 10% by weight with respect to the emulsion of the present invention. .

The alkoxysilyl group is hydrolyzed into silanol groups and alcohols with water, and then siloxane bonds are formed by dehydration condensation of silanol groups or dealcoholization condensation of silanol groups and alkoxysilyl groups to form an intraparticle polymer. Crosslinking, or interparticle polymer crosslinking, fusion bonding, and emulsion gelation occur. Although the reason for the effect of the present invention is not clear, it may be because the shell part polymer coats the surface of the alkoxysilyl group-containing core part polymer, which prevents contact between the core part alkoxysilyl group and water. Presumed.

[0021]

EXAMPLES The present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the examples. In addition, part and% in an example show a weight part and weight%, respectively. Further, the properties of each of the obtained emulsions were evaluated by the following measuring methods immediately after production and after storage for 3 months or 6 months at room temperature. a. Minimum film forming temperature The minimum film forming temperature was measured with a minimum film forming temperature measuring device manufactured by Rigaku Kogyo. b. Emulsion state The change in the viscosity of the emulsion or the presence or absence of gelation was observed, and the results are shown below. O: Little change, X: Large change c. Emulsion was applied to a water-resistant glass plate so that the dry film thickness was about 25 μm, and it was aged for 7 days under the condition of 23 ° C × 68% RH and immersed in warm water of 80 ° C for 60 minutes to observe the surface condition. And shown by: ◯: No abnormality, △: Slightly whitened, ×: Whitened, blister occurred

Example 1 A polymerization vessel equipped with a stirrer, a condenser, a thermometer, and a nitrogen gas inlet was charged with 1,240 parts of deionized water, 0.57 parts of sodium carbonate as a pH buffer, and 5.63 parts of boric acid, and stirred while stirring. After the temperature was raised to ° C, the atmosphere was replaced with nitrogen. 2.1 parts of Rongalit and 1 part of disodium ethylenediaminetetraacetate
% Aqueous solution 0.15 part, ferrous sulfate 1% aqueous solution 0.05 part at the same time, methyl methacrylate 294 parts, butyl acrylate 378 parts, styrene 84 parts, γ-methacryloxypropyltrimethoxysilane 84 parts, t-butyl Hydroperoxide (69% of pure content) 2.5 parts, reactive surfactant Aqualon RN-10 [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name] 16.8 parts and Aqualon HS-10 [Daiichi Kogyo Seiyaku Co., Ltd.] Trade name] 867.7 parts of a mixed solution of 8.4 parts was uniformly added over 2.5 hours, and the mixture was further reacted at 60 ° C for 1 hour to obtain a core emulsion. 0.9 parts of Rongalit was added to this at the same temperature, and at the same time, 151 parts of methyl methacrylate, 173 parts of butyl acrylate, 36 parts of styrene, 7.2 parts of the reactive surfactant Aqualon RN-10 (supra), Aqualon HS-10. (Above)
3.6 parts and t-butyl hydroperoxide (purity 69
%) 371.9 parts of a mixed solution of 1.1 parts was uniformly added over 1 hour, and the mixture was further reacted at 60 ° C. for 1 hour to complete the polymerization.
The solid content of the obtained core-shell type emulsion was 4
The pH was 9.7% and 7.1. The reactive surfactant used for the polymerization is Aqualon RN-10, which is one of the examples listed above 13).
In addition, Aqualon HS-10 belongs to 6). The properties of the emulsion obtained above are as shown in Table 1.

Example 2 A polymerization vessel equipped with a stirrer, a condenser, a thermometer, and a nitrogen gas inlet was charged with 640 parts of deionized water, 0.57 parts of sodium carbonate as a pH buffer, and 5.63 parts of boric acid, and stirred while stirring. After the temperature was raised to ° C, the atmosphere was replaced with nitrogen. To this was added 2.4 parts of L-ascorbic acid, 0.15 part of a 1% aqueous solution of disodium ethylenediaminetetraacetate and 0.5 part of a 1% aqueous solution of ferrous sulfate, and at the same time 326 parts of methyl methacrylate, 442 parts of butyl acrylate and 96 parts of styrene. Part, γ-methacryloxypropyltrimethoxysilane 48 parts, γ-methacryloxypropylmethyldimethoxysilane 48 parts, t-butyl hydroperoxide (pure content 69%) 2.9 parts, reactive surfactant Eleminol JS-2 [Sanyo] Chemical Industry Co., Ltd., trade name] 24.6 parts, Aqualon RN-20 [Daiichi Kogyo Seiyaku Co., Ltd.]
Made, trade name] 19.2 parts and deionized water 480 parts mixture 1,4
Of the 86.7 parts emulsified with a homomixer, 44.6 parts were added and seed polymerization was carried out, and the remaining 1,442.1 parts were added uniformly over 2.5 hours, and the mixture was further reacted at 30 ° C for 1 hour to form a core emulsion. Obtained. To this, 0.6 part of L-ascorbic acid was added at the same temperature, and at the same time, 91.2 parts of methyl methacrylate, 120 parts of butyl acrylate, 24 parts of styrene, 4.8 parts of acrylic acid, t-butyl hydroperoxide (69% pure) 0.7 parts, reactive surfactant Eleminol JS-
2 (above) 6.2 parts, Aqualon RN-20 (above) 4.8 parts and deionized water 120 parts A mixture of 371.7 parts emulsified with a homomixer was added uniformly over 1 hour, and further 30
The reaction was carried out at 0 ° C for 1 hour to terminate the polymerization, and the mixture was neutralized with 10% aqueous ammonia. The obtained core-shell type emulsion had a solid content concentration of 49.4% and a pH of 7.0. The reactive surfactants used for the polymerization belong to 4) of which Eleminol JS-2 is exemplified above, and 13) of Aqualon RN-20. The properties of the emulsion obtained above are as shown in Table 1.

Comparative Example 1 A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged with 640 parts of deionized water, the temperature was raised to 30 ° C. with stirring, and then the atmosphere was replaced with nitrogen. To this, 3 parts of L-ascorbic acid and 0.5 part of a 1% ferrous sulfate aqueous solution were added, and at the same time, 417.2 parts of methyl methacrylate, 562 parts of butyl acrylate, 120 parts of styrene, 4.8 parts of acrylic acid,
γ-methacryloxypropyltrimethoxysilane 48 parts,
γ-methacryloxypropyl methyldimethoxysilane 48
Part, t-butyl hydroperoxide (pure content 69%) 3.6
Part, Reactive Surfactant Eleminol JS-2 (supra) 3
A mixture of 0.8 parts, 24 parts of Aqualon RN-20 (previously mentioned) and 600 parts of deionized water was emulsified with a homomixer to prepare 1,858.4 parts of the mixture, 44.2 parts of which were added to carry out seed polymerization, and the remaining 1,795.4 parts were continuously used for 3.5 hours. And evenly add
Polymerization was terminated by reacting at 30 ° C. for 1 hour and neutralized with 10% aqueous ammonia. The solid content concentration of the obtained emulsion is
It was 49.0% and pH 7.1. The properties of the emulsion obtained above are as shown in Table 1.

Comparative Example 2 1,240 parts of deionized water was charged into a polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet, the temperature was raised to 60 ° C. with stirring, and then the atmosphere was replaced with nitrogen. Add 3 parts of Rongalit and 1% of disodium ethylenediaminetetraacetate.
0.15 parts of an aqueous solution and 0.05 part of a 1% ferrous sulfate aqueous solution are added, and at the same time, 445 parts of methyl methacrylate, 551 parts of butyl acrylate, 120 parts of styrene, 84 parts of γ-methacryloxypropyltrimethoxysilane, 84 parts of t-butylhydro. 1,239.6 parts of a mixed solution of 3.6 parts of peroxide (69% of pure content), 24 parts of the reactive surfactant Aqualon RN-10 (previously mentioned) and 12 parts of Aqualon HS-10 (previously mentioned) were uniformly added over 3.5 hours. Then, the mixture was further reacted at 60 ° C. for 1 hour to complete the polymerization. The solid content of the obtained emulsion is 49.5%, pH
6.1. The properties of the emulsion obtained above are as shown in Table 1.

Comparative Example 3 A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged with 1,240 parts of deionized water, 0.57 parts of sodium carbonate as a pH buffer and 5.63 parts of boric acid, and stirred at 60 ° C. After the temperature was raised to 1, the atmosphere was replaced with nitrogen. Add 2.1 parts of Rongalit and 1% of disodium ethylenediaminetetraacetate.
0.15 parts of an aqueous solution and 0.05 part of a 1% ferrous sulfate aqueous solution are added, and at the same time, 294 parts of methyl methacrylate, 378 parts of butyl acrylate, 84 parts of styrene, 84 parts of γ-methacryloxypropyltrimethoxysilane, 84 parts of t-butylhydro. Peroxide (purity 69%) 2.5 parts, non-reactive surfactant Neugen EA-170 [Daiichi Kogyo Seiyaku Co., Ltd., trade name] 16.8 parts and Emar O [Kao Co., Ltd., trade name] 8.4 Mixed liquid
867.7 parts were uniformly added over 2.5 hours and further reacted at 60 ° C. for 1 hour to obtain a core emulsion. 0.9 parts of Rongalit was added to this at the same temperature, and at the same time 151 parts of methyl methacrylate, 173 parts of butyl acrylate and styrene were added.
36 parts, non-reactive surfactant Neugen EA-170 (supra)
A mixture of 37 parts of 7.2 parts, 3.6 parts of Emal O (described above) and 1.1 parts of t-butyl hydroperoxide (69% of pure content) was uniformly added over 1 hour, and the mixture was further reacted at 60 ° C for 1 hour. And the polymerization was completed. The obtained core-shell type emulsion had a solid content concentration of 49.8% and a pH of 7.0. The properties of the emulsion obtained above are as shown in Table 1.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION The alkoxysilyl group-containing acrylic emulsion of the present invention has good long-term storage stability because hydrolysis and condensation of the alkoxysilyl group are greatly suppressed, and is practically used as a base for paints, sealants and the like. It is useful as an emulsion.

Claims (1)

[Claims] 1. A core-shell type emulsion having different compositions for a core and an outer shell of an emulsion particle, the core part of which comprises (a) an alkyl group having 1 to 18 carbon atoms. Alkyl ester of (meth) acrylate having 50 to 99% by weight (b) Formula R ¹ R ² _(3-n) SiX _n (wherein R ¹ is a monovalent organic group having a polymerizable double bond, R ² Is an alkyl group having 1 to 4 carbon atoms, X is an alkoxyl group having 1 to 4 carbon atoms, n is an organic silicon compound represented by 2 or 3) 1 to 20% by weight (c) The above (a) and (b) 0 to 30% by weight of a monomer copolymerizable with [however, the total amount of (a), (b) and (c) is 100% by weight]. A) Alkyl ester of (meth) acrylate having an alkyl group having 1 to 18 carbon atoms 70 to 100% by weight (B) Monomer copolymerizable with (A) above Body 0-30 wt% [However, (A) and total 100% by weight of (B)] monomer component consisting of a (II), is the ratio (I) / (I
I) = 50/50 to 90/10 (weight ratio), a core-shell type alkoxysilyl group-containing acrylic emulsion obtained by emulsion polymerization using a reactive surfactant.