JPH073206A - Surface treating composition for gas barrier - Google Patents

Abstract

PURPOSE:To obtain the subject surface treating composition giving a coated film excellent in gas barrier property, transparency and flexibility and containing an amino group containing silane compound or its hydrolysis condensed compound and a polymer dispersed in water obtained by emulsion polymerizing a polymerizable monomer in water. CONSTITUTION:(A) A silane compound expressed by the formula I [A<1> is alkylene; R<1> is H, low alkyl or a group expressed by the formula II (A<2> is a direct bond or alkylene; R<5> and R<6> are H or low alkyl); R<2> is H or low alkyl; R<3> is low alkyl, aryl or unsaturated aliphatic residue; R<4> is H, low alkyl or acyl; (w) is 0, 1 or 2; (z) is 1-3 integer; w+z=31 (e.g. gamma- aminopropyltriethoxysilane, etc.) and/or (B) an polymer dispersed in water obtained by emulsion polymerizing a hydrolysis condensed compound of the component A and >=1 polymerizable monomer (e.g. methyl methacrylate, etc.) in water to obtain the objective surface treating composition excellent in gas barrier property, being transparent and capable of forming a flexible coat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier surface treating composition capable of forming a film excellent in gas barrier property, transparency and flexibility.

[0002]

2. Description of the Related Art Demand for gas barrier materials having extremely low permeability to gases such as oxygen, nitrogen, carbon dioxide and water vapor is increasing in the field of packaging materials and the like. In order to impart gas barrier properties to a molded material such as a plastic film or sheet, a molded body is made of a gas impermeable material such as an ethylene-vinyl alcohol copolymer, a vinylidene chloride copolymer, or polymethaxylylene adipamide. Methods of making, laminating or coating these gas impermeable materials on other materials, laminating aluminum foil on film materials, vapor deposition of metal oxides, etc. are known.

However, among the gas-impermeable materials, ethylene-vinyl alcohol copolymer and polymetaxylylene adipamide have a large hygroscopic property, and there is a problem that the gas barrier property is significantly lowered due to the moisture absorption. Since the vinylidene chloride-based copolymer contains a chlorine atom, it may cause pollution. Also, with the aluminum foil laminated film, the packaged contents cannot be seen from the outside,
Since the metal vapor-deposited film of (3) deteriorates flexibility and the like, there is a problem that cracks are likely to occur in the vapor-deposited layer at the time of packaging and the gas barrier property is deteriorated.

In order to solve these problems, it has been researched to perform surface treatment of a plastic film using polysiloxane having a dense molecular structure and excellent in weather resistance, hardness and chemical resistance. . However, since tetraalkoxysilane used as a raw material for polysiloxane has four hydrolysis-condensation reaction points, it has a large volume contraction rate during condensation, and it has been difficult to obtain a coating film without cracks or pinholes.

Therefore, it has been proposed to suppress the generation of cracks and pinholes by subjecting an alkyltrialkoxysilane having only three hydrolysis-condensation reaction points to hydrolytic condensation alone or with tetraalkoxysilane. However, since the alkyltrialkoxysilane has low reactivity, when the alkyltrialkoxysilane is used alone, many monomers remain without condensation, and when it is used in combination with the tetraalkoxysilane, uniform co-hydrolysis condensation cannot be achieved easily. It was the current situation. Further, since these silane-based surface treatment compositions have no affinity with a plastic film material and have poor wettability, there is a problem in that they are inferior in film forming property.

Further, JP-A-2-286331 discloses that an alkoxysilane is hydrolyzed and condensed to coat a plastic film. However, in this method, only the alkoxysilane component is coated on the film. Was significantly impaired.

From the above viewpoint, for example, Japanese Patent Application Laid-Open No. 1-278574 discloses suppressing cracks in a surface-treated film by combining an alkoxysilane hydrolyzate such as tetraalkoxysilane with a reactive urethane resin. There is. However, since the reactive urethane resin reacts with the alcohols used as the solvent, the alkoxysilane hydrolyzate and the reactive urethane resin are not sufficiently complexed and phase separation occurs, which may make the coating opaque. there were.

As described above, a polar organic solvent such as alcohol is generally widely used as a solvent for hydrolysis of alkoxysilanes. However, pollution by the organic solvent, safety and hygiene during work, resource saving, etc. Therefore, there is a demand for a transition to an aqueous system that does not contain an organic solvent or that contains the least solvent.

[0009]

In consideration of the above problems, the present inventors have developed a surface-treated coating having excellent gas barrier properties, transparency, and flexibility that does not impair the physical properties of non-treated products. An object is to provide a water-based composition for surface treatment of a gas barrier that can be formed.

[0010]

The present invention provides a gas barrier surface treatment composition comprising a silane compound (A) represented by the following general formula (I):

[0011]

[Chemical 3] [Wherein A ¹ is an alkylene group, R ¹ is a hydrogen atom, a lower alkyl group, or

[0012]

[Chemical 4]

(In the formula, A ² represents a direct bond or an alkylene group, and R ⁵ and R ⁶ represent a hydrogen atom or a lower alkyl group)
A group represented by, R ² is a hydrogen atom or a lower alkyl group, R ³ are the same or different lower alkyl group, an aryl group or an unsaturated aliphatic residue, R ⁴ is a hydrogen atom, a lower alkyl group or an acyl group (However, R ¹ , R ² , R ⁵ , and R
^At least one of ⁶ is a hydrogen atom), w is 0,
1 or 2, z represents an integer of 1 to 3 (provided that w + z = 3)] and / or one or more polymerizable compounds with the hydrolysis-condensation product (B) of the silane compound (A). The gist is that it contains an aqueous dispersion polymer obtained by emulsion polymerization of a monomer in water.

[0014]

[Function] Silane compound (A) used in the present invention
Is not limited as long as it satisfies the following formula (I), and one or more of them can be used.

[0015]

[Chemical 5] (However, in the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , w, and z have the same meaning as described above.)

Specific examples of these silane compounds (A) include N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane and N-β ( Aminoethyl) γ
-Aminopropyltriisopropoxysilane, N-β
(Aminoethyl) γ-aminopropyltributoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiisopropoxysilane, N-β (aminoethyl) γ-aminopropylmethyldibutoxysilane, N-β (aminoethyl) γ-aminopropylethyldimethoxysilane, N-β (aminoethyl) γ- Aminopropylethyldiethoxysilane, N-
β (aminoethyl) γ-aminopropylethyldiisopropoxysilane, N-β (aminoethyl) γ-aminopropylethyldibutoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-amino Propyltriisopropoxysilane,
γ-aminopropyltributoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldiisopropoxysilane, γ-aminopropylmethyldibutoxysilane, γ-aminopropylethyldimethoxy Silane, γ-aminopropylethyldiethoxysilane, γ-
Aminopropylethyldiisopropoxysilane, γ-aminopropylethyldibutoxysilane, γ-aminopropyltriacetoxysilane and the like can be mentioned, and one or more of these can be used.

In the present invention, the compound (B) obtained by previously hydrolyzing one or more compounds selected from the above-exemplified silane compounds (A) to be condensed (poly) can also be used. For example, when γ-aminopropyltrimethoxysilane is used as the silane compound (A), the hydrolysis condensation reaction is represented by the following formula. H ₂ NC ₃ H ₆ -Si (OCH ₃ ) ₃ + 3H ₂ O → H ₂ NC ₃ H ₆ -Si (OH) ₃ + 3CH ₃ OH (III) H ₂ NC ₃ H ₆ -Si (OH) ₃ → H _{2 NC 3 H 6 -SiO 3/2 +3/2 H} 2 O (IV) hydrolysis condensation polymerization may be carried out in aqueous solution.

An organometallic compound (C) may be added to the gas barrier surface treatment composition of the present invention. The organometallic compound (C) is not particularly limited as long as it can be represented by the following general formula (II). R ⁷ _m M (OR ⁸ ) _n (II) (wherein M is a metal element, R ⁷ may be the same or different, and represents a hydrogen atom, a lower alkyl group, an aryl group or an unsaturated aliphatic residue. , R ⁸ represents a hydrogen atom, a lower alkyl group or an acyl group, m is 0 or a positive integer,
n is an integer of 1 or more, and m + n matches the valence of the metal element M).

As a specific example, tetramethoxysilane,
Tetraethoxysilane, tetraisopropoxysilane,
Tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltributoxysilane, dimethyldimethoxysilane, Dimethyldiethoxysilane, dimethyldiisopropoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldiisopropoxysilane, diethyldibutoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycid Xypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane,
Alkoxysilanes such as γ-chloropropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane; titanium alkoxides such as titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide; zirconium tetraethoxide, zirconium tetraisopropoxy. And zirconium alkoxides such as zirconium tetrabutoxide;
Aluminum alkoxides such as aluminum triethoxide, aluminum triisopropoxide and aluminum tributoxide; acetoxylans such as tetraacetoxysilane and methyltriacetoxysilane; silanols such as trimethylsilanol. One of these or Two or more kinds can be used.

The organometallic compound (C) is a chemical resistance of the coating,
It is effective in improving heat resistance, and is 0 to 200 with respect to the silane compound (A) and / or its hydrolyzed condensate (B).
It is desired to use about mol%, preferably 0 to 100 mol%. If it is used in excess of 200%, gelation may occur suddenly, which is not preferable.

The gas barrier surface treatment composition of the present invention comprises a silane compound (A) and / or (B) having a functional group of R ¹ or R ² and / or Si (OR ⁴ ).
The organic compound (D) having two or more functional groups having reactivity with the group in the molecule may be contained. Therefore, the functional group of the organic compound (D) must be appropriately selected according to the structure of the silane compound used. For example, the functional groups of a silane compound are amino groups and Si (OR ⁴ ).
When it is a group, it is necessary that a hydroxyl group, an epoxy group, a carboxyl group or the like be present in the organic compound (D).

Specific examples of the organic compound (D) include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, tetraethylene glycol diglycidyl ether, nonaethylene glycol diglycidyl ether, propylene glycol diglycidyl. Ether, dipropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6
-Hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester,
Diglycidyl ethers and diglycidyl esters such as glycerol diglycidyl ether; triglycidyl ethers such as glycerol triglycidyl ether, diglycerol triglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanurate, trimethylolpropane triglycidyl ether Tetraglycidyl ethers such as pentaerythritol tetraglycidyl ether; Other polyglycidyl ethers or polymers having a glycidyl group as a functional group; Dicarboxylic acids such as tartaric acid and adipic acid; Carboxyl group-containing polymers such as polyacrylic acid Isocyanates such as hexamethylene diisocyanate and xylylene diisocyanate; oxazoline-containing polymers; alicyclic epoxy compounds and the like. Is, it is possible to use one or more of these, compounds having a glycidyl group 2 or more from the standpoint of reactivity is preferably used.

The amount of the organic compound (D) used is 0 to 300%, preferably 1 to 200% as a functional group equivalent to the silane compound (A) and / or (B). The compounding of the compound (D) improves the flexibility of the coating film, but if it is used in excess of 300%, the gas barrier property may decrease, which is not preferable.

Organometallic compound (C) and organic compound (D)
When added to the surface treatment composition for gas barrier,
After the reaction with the silane compound (A), hydrolysis-condensation by the method described above is preferably added.
This is because in the case of the organic metal compound (C), its own hydrolysis and condensation occur, and in the case of the organic compound (D), its own hydrolysis reaction occurs.

It is essential that the composition for surface treatment for gas barrier of the present invention contains a water-dispersed polymer together with the silane compound. By blending the water-dispersed polymer, the film-forming property and flexibility of the composition are improved, and a more uniform gas barrier film can be obtained. Examples of the polymerizable monomer used to form the water-dispersed polymer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, and 4-t-butyl. Cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate,
Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 2- (meth) acryloyloxyethyl acid phosphate, acid phosphooxypolyoxypropylene glycol mono (meth) acrylate, acid phosphooxypolyoxyethylene glycol mono (meth) acrylate, methacryloyloxyethyl acid phosphate monoethanolamine half salt and the like ( (Meth) acrylic acid esters, styrene, α-methylstyrene, divinylbenzene and their nuclear substitution derivatives Aromatic vinyl compounds and vinylidene chloride, and the like without limitation, it is possible to obtain an aqueous dispersion polymer by emulsion polymerization of one or more of these.

The emulsion polymerization can be carried out under ordinary emulsion polymerization conditions. For example, the above-mentioned polymerizable monomer and emulsifier, a polymerization initiator, a chain transfer agent if necessary, and a pH in an aqueous medium.
A preparation agent and the like may be added and polymerization may be carried out at 20 to 100 ° C. for about 0.5 to 30 hours. As the emulsifier used here, anionic, nonionic, combinations of anionic and nonionic, cationic, amphoteric and the like can be used. Examples of the anionic emulsifier include higher alcohol sulfuric acid ester sodium salt, alkylbenzene sulfonic acid sodium salt, succinic acid dialkyl ester sulfonic acid sodium salt, alkyldiphenyl ether disulfonic acid, and the like, and examples of the nonionic emulsifier include polyoxyethylene alkyl allyl. Ether, etc. can be mentioned. As a cationic emulsifier,
For example, alkylpyridinyl chloride, alkylammonium chloride and the like are used. As the amphoteric emulsifier, for example, lauryl petine can be used.
Further, a reactive emulsifier or the like may be used. The amount of the emulsifier used is 0.001 to 100 parts by weight of the polymerizable monomer.
10 parts by weight is desirable. If it is less than 0.001 part by weight, the stability of the micelle during polymerization may be poor, and if it is more than 10 parts by weight, the water resistance of the gas barrier coating may be poor.

As the polymerization initiator, a water-soluble persulfate,
Hydrogen peroxide or the like can be used, and if necessary, it can be used in combination with a reducing agent. Further, an oil-soluble polymerization initiator such as 2,2′-azobisisobutyronitrile or 2,2′-azobis (4-methoxy-2,4)
It is also possible to use an azo-based polymerization initiator such as dimethylvaleronitrile) or an organic peroxide polymerization initiator such as benzoyl peroxide or butyl peroxide. The amount of the polymerization initiator used is 0.01 to 5 with respect to 100 parts by weight of the polymerizable monomer.
Parts by weight are preferred.

The compounding ratio (silane compound / water dispersion polymer) of the silane compound (A) or its hydrolyzed condensate (B) and the water dispersion polymer in the present invention is 10 to 0.1 (provided that the silane compound is used. (A) is R ¹ _m —SiO _{4 —m / 2} , and the water-dispersed polymer is converted into solid content), and more preferably 10 to 0.5. If it is more than 10, the gas barrier film may be inferior in flexibility,
If it is smaller, the gas barrier property may be deteriorated.

An organic solvent may be added to the composition of the present invention in order to improve film-forming property and wettability.
Specific examples of the organic solvent used here include alcohols such as methanol, ethanol, isopropanol, n-butanol, ethylene glycol, diethylene glycol, ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; ketones such as acetone and methyl ethyl ketone. Other than the above, methyl acetate, tetrahydrofuran and the like can be mentioned, and one or more of them can be mixed and used. Of these, alcohols are preferably used. The amount of these organic solvents used is less than 20 parts by weight, preferably less than 10 parts by weight, more preferably less than 5 parts by weight, based on the total amount of the solvent.

The composition for surface treatment for gas barrier of the present invention contains inorganic or organic compounds such as a curing catalyst, a wettability improver, a plasticizer, an antifoaming agent and a thickening agent as long as the effects of the present invention are not impaired. Various additives can be added as needed.

A resin molding is used as the substrate coated with the gas barrier surface treatment composition of the present invention. The resin forming the molded article is not particularly limited, but examples thereof include polyolefin resins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate and copolymers thereof. Polyamide resin such as polyoxymethylene; polystyrene, poly (meth) acrylic acid ester, polyacrylonitrile, polyvinyl acetate, polycarbonate, cellophane, polyimide, polyetherimide, polyphenylene sulfone, polysulfone, polyetherketone, ionomer Resin, thermoplastic resin such as fluororesin; melamine resin, polyurethane resin, epoxy resin, phenol resin, unsaturated polyester resin, alkyd resin, lily Resins, thermosetting resins such as silicone resins.

The shape of the molded article can be selected from film, sheet, bottle, etc. according to the application. A thermoplastic film is particularly preferable because it is easy to process. The method for coating the surface treatment composition for gas barrier on the above resin molding is not particularly limited, and a roll coating method, a dip coating method, a bar coating method, a nozzle coating method, or a combination thereof is adopted. Before coating, the resin molded body may be subjected to surface activation treatment such as corona treatment or known anchor treatment such as urethane resin. Further, the resin molding after the coating treatment may be subjected to lamination treatment or other known treatment.

After coating, the coating is cured and dried, but the gas barrier surface treatment composition of the present invention is cured and dried even at room temperature. For faster curing and drying,
It is advisable to heat the resin molding at a temperature not higher than the heat resistant temperature. The thickness of the coating is preferably 0.001 to 20 μm, more preferably 0.01 to 10 μm after drying. If the thickness is less than 0.001 μm, the coating is not uniform and pinholes are likely to occur, and if it is thicker than 20 μm, cracks are likely to occur in the coating, which is not preferable.

[0034]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. The evaluation method of the characteristic test was performed as follows. <Oxygen permeability> According to JIS K 7126, it was measured by a gas permeability measuring device manufactured by Toyo Seiki Seisakusho. <Flexibility> A surface treatment composition is applied to 25 μm polyethylene terephthalate (hereinafter abbreviated as PET) to a predetermined thickness by a dipping method, and then a dried coating film is applied at 180 °
Bent and bent without cracks were marked with ◯, and cracks were marked with x. <Transparency> P coated as in the flexibility evaluation test
The ET film was visually compared with the untreated film, and those having no difference in transparency were marked with ◯, and those having turbidity such as white turbidity were marked with x.

Example 1 A four-necked flask was equipped with a stirrer and a thermometer, and water 200
g, sodium dodecylbenzene sulfonate 0.6
g, ammonium persulfate 0.68 g, charged with nitrogen gas, heated to 80 ° C., and then butyl acrylate 47.9
g, methyl methacrylate 49.6 g, methacrylic acid 2.
A mixture of 5 g, 30 g of water and 0.7 g of sodium dodecylbenzene sulfonate was continuously added dropwise over 3 hours. After completion of the dropping, the mixture was heated at 80 ° C. for 1 hour, cooled, and then filtered through a 200-mesh wire net to obtain an emulsion polymer 1. The average particle size of the obtained emulsion polymer was 103.7 nm. Next, γ-aminopropyltriethoxysilane 2
0 g was added to 80 g of water and stirred at 23 ° C. for 3 hours to obtain a transparent liquid. 20 g of emulsion polymer 1 was added dropwise to this liquid over 30 minutes to obtain a gas barrier surface treatment composition 1.
The composition for surface treatment 1 was applied to a PET film having a thickness of 25 μm by a dipping method so as to have a thickness of 1.0 μm and dried at 80 ° C. for 1 minute. The surface-treated film obtained was transparent and had a good flexibility, and had an oxygen permeability of 4.01 cc.
/ M ² · 24 hrs · atm.

Example 2 A four-necked flask was equipped with a stirrer and a thermometer, charged with 20 g of γ-aminopropyltriethoxysilane and 4 g of ethylene glycol diglycidyl ether, and reacted at 70 ° C. for 3 hours while stirring. After cooling to 23 ° C, water 80
g was added, the mixture was stirred for 3 hours, and 20 g of emulsion polymer 1 was added dropwise over 30 minutes to obtain a surface treating composition 2. The composition 2 for surface treatment was applied to a PET film having a thickness of 25 μm by a dipping method so as to have a thickness of 1.2 μm, and dried at 80 ° C. for 1 minute. The surface-treated film obtained was transparent and had a good flexibility, and had an oxygen permeability of 4.01 cc / m.
^{It was 2} · 24 hrs · atm.

Example 3 The same operation as in Example 2 was carried out except that m-xylylene diisocyanate was used instead of ethylene glycol diglycidyl ether to obtain a surface-treated film having a thickness of 1.2 μm. This film was transparent and flexible, and had an oxygen permeability of 4.20 cc / m ² · 24 hrs · atm.

Comparative Example 1 Emulsion Polymer 1 was applied to a PET film having a thickness of 25 μm by a dipping method so as to have a thickness of 1.0 μm after drying,
It was dried at 80 ° C. for 1 minute. The surface-treated film obtained was transparent and had a good flexibility, but had an oxygen permeability of 69.03c.
It was c / m ² · 24 hrs · atm.

Comparative Example 2 20 g of γ-aminopropyltriethoxysilane was added to 80 parts of water.
In addition to g, the mixture was stirred at 23 ° C. for 3 hours, and the obtained transparent liquid was applied to a PET film having a thickness of 25 μm by a dipping method so as to have a thickness of 1.0 μm after drying, and dried at 80 ° C. for 1 minute. The obtained surface-treated film was transparent and had an oxygen permeability of 8.11 cc / m ² · 24 hrs · atm, but had a poor flexibility.

[0040]

EFFECT OF THE INVENTION The gas barrier surface treatment composition of the present invention is water-based and has no fear of environmental pollution, and can form a transparent film excellent in gas barrier property and flexibility. Therefore, it can be widely applied for gas barriers in the field of packaging materials and the like.

Front page continuation (72) Inventor Tadahiro Yoneda 5-8 Nishiomitabicho Suita City Osaka Prefecture Inside the Central Research Laboratory of Nippon Shokubai Co., Ltd.

Claims (1)

[Claims] 1. A silane compound (A) represented by the following general formula (I): [Wherein A ¹ is an alkylene group, R ¹ is a hydrogen atom, a lower alkyl group, or (In the formula, A ² is a direct bond or an alkylene group, and R ⁵ and R ^{6 are}
Is a hydrogen atom or a lower alkyl group), R ² is a hydrogen atom or a lower alkyl group, R ³ is the same or different lower alkyl group, an aryl group or an unsaturated aliphatic residue, and R ⁴ is a hydrogen atom. , A lower alkyl group or an acyl group (provided that at least one of R ¹ , R ² , R ⁵ , and R ⁶ is a hydrogen atom), w is 0, 1, or 2, and z is 1 to 3. And (or w + z = 3)] and / or the hydrolysis-condensation product (B) of the silane compound (A) and one or more polymerizable monomers are emulsion-polymerized in water. A surface-treating composition for a gas barrier, which comprises the above water-dispersed polymer.