JPH0860098A - Coating composition - Google Patents

Abstract

PURPOSE: To obtain a water-based coating composition giving a film which is excellent in water resistance, chemical resistance, weathering resistance contamination resistance, heat resistance, processability, flexing resistance, and corrosion prevention and has high hardness and satisfactory flexibility by emulsionpolymerizing a monomer in water in the presence of a water-soluble silane polymer. CONSTITUTION: The composition comprises a water-soluble polymer (A) obtained by hydrolytically condensing a silane compound represented by the formula [wherein R<1> is H, a lower alkyl, an aryl, or an unsaturated aliphatic residue; R<2> is H, a lower alkyl, or an acyl; and m is 0, 1, or 2 and n is 2, 3, or 4, provided that (m+n):4] in water and an emulsified polymer (B) obtained by emulsion-polymerizing a radical-polymerizable monomer in water in the presence of the polymer (A), the weight ratio of the polymer (A) to the polymer (B) being 0.1-5 on a solid basis. It can give a coating film which is excellent in water resistance, chemical resistance, weathering resistance, contamination resistance, and heat resistance and has high hardness and excellent flexibility properties.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating capable of forming a flexible coating having excellent water resistance, chemical resistance, weather resistance, stain resistance, heat resistance, high hardness and flexibility. It relates to a composition.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental pollution and safety and hygiene, in the field of paints, coating compositions and paints are becoming more water-based, and water-based emulsion paints are widely used in place of conventional organic solvent-based paints. Has become. However, emulsion paints produced by general emulsion polymerization are inferior in water resistance and chemical resistance.

On the other hand, the polysiloxane obtained by hydrolyzing and condensing alkoxysilanes, when applied as a coating film, has water resistance, chemical resistance, weather resistance, hardness,
Although it has excellent heat resistance, on the other hand, there is a problem that it is inferior in flexibility such as flexibility and film formability. Further, since the alkoxysilanes react with water, there is a problem that the polymerization stability and the storage stability are significantly deteriorated when the coating composition is made into an aqueous system.

[0004]

Therefore, in the present invention, in water system, water resistance, chemical resistance, weather resistance, stain resistance, heat resistance,
It is an object of the present invention to provide a coating composition which is excellent in workability, flexibility and anticorrosion property, and which can form a coating film having high hardness and good flexibility.

[0005]

The coating composition of the present invention comprises a silane compound (I) R ¹ _m Si (OR ² ) _n (I) represented by the following general formula (wherein R ¹ is the same). Or may be different, and represents a hydrogen atom, a lower alkyl group, an aryl group or an unsaturated aliphatic residue, R ² represents a hydrogen atom, a lower alkyl group or an acyl group, m represents 0, 1 or 2, n Is 2, 3 or 4
, And m + n is 4), a water-soluble polymer (A) obtained by hydrolyzing and condensing in water, and the water-soluble polymer (A)
A water-dispersible polymer (B) obtained by emulsion-polymerizing a radical-polymerizable polymerizable monomer in water in the presence of The water-dispersed polymer (B) has a solid content of (A) / (B) of 0.1 to 0.1.
The gist is that it is contained so as to be 5.

The water-soluble polymer (A) is hydrolyzed and condensed in water containing a surfactant, and the water-dispersed polymer (B) has a phosphoric acid group or a carboxyl group. 0.1 to 30.0 parts by weight of the radically polymerizable polymerizable monomer (B-1), and other radically polymerizable polymerizable monomer (B-2) 70.0 to 99.
The emulsion stability of 9 parts by weight [wherein (B-1) + (B-2) is 100 parts by weight] in water means that the composition has storage stability, film formability, and It is a preferred embodiment of the present invention in that it improves the adhesion of the coating and other physical properties of the coating.

[0007]

The present inventors focused on polysiloxane, which forms a dense and highly weather-resistant, chemical-resistant, and water-resistant coating as the main component of the coating composition. In addition to the poor flexibility and film-forming properties, the alkoxysilanes, which are the raw material monomers, react with water to cause hydrolysis and condensation in the first place, so the problem of poor polymerization stability and storage stability in aqueous systems is a problem. there were. Therefore, as a result of diligent studies on this point, it was possible to obtain an aqueous composition excellent in polymerization stability and storage stability by conducting a water-dispersed polymer synthesis reaction in an aqueous polysiloxane solution. The present invention has been accomplished by finding that a film having hardness and flexibility can be formed. Hereinafter, the present invention will be described in detail.

The silane compound (I) used as a starting material for the water-soluble polymer (A) in the present invention is not limited as long as it satisfies the following formula, and one or more thereof can be used. R ¹ _m Si (OR ² ) _n (I) (In the formula, R ¹ may be the same or different and represents a hydrogen atom, a lower alkyl group, an aryl group or an unsaturated aliphatic residue, and R ² is Represents a hydrogen atom, a lower alkyl group or an acyl group, m is 0, 1 or 2, n is 2, 3 or 4
, And m + n is 4.) Here, the lower alkyl group refers to a linear or branched alkyl group having 6 or less carbon atoms.

Specific examples of these silane compounds (I) include tetramethoxysilane, tetraethoxysilane,
Tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxy Silane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxy Silane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-
Mercaptotriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-
Examples thereof include epoxycyclohexylethyltriethoxysilane, and one or more of these can be used. From the viewpoint of versatility and storage stability, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane and methyltriethoxysilane are preferable.

In the present invention, one or more compounds selected from the above-exemplified silane compounds (I) are previously hydrolyzed and condensed (poly) to obtain a water-soluble polymer (A). Here, the hydrolytic condensation of the silane compound (I) is performed in water. The amount of water at this time is not particularly limited. This is because it may be adjusted in the subsequent aqueous dispersion polymer synthesizing step so that the solid content concentration is suitable for the coating composition. Therefore, the weight of the silane compound (I) is preferably 10 times or more so that the hydrolysis reaction proceeds smoothly.

The above hydrolysis condensation reaction is preferably carried out in the presence of a surfactant. This is because the surfactant has a function of suppressing a rapid reaction of the silane compound (I) during hydrolysis and condensation and preventing gelation.

As the surfactant, anionic, nonionic, a combination of anion and nonionic, cationic,
A surfactant such as amphoteric can be used. As the anionic surfactant, for example, higher alcohol sulfuric acid ester sodium salt, alkylbenzene sulfonic acid sodium salt,
Succinic acid dialkyl ester sulfonic acid sodium salt,
Examples thereof include alkyl diphenyl ether disulfonic acid, and examples of the nonionic surfactant include polyoxyethylene alkyl allyl ether. As the cationic surfactant, for example, alkylpyridinyl chloride, alkylammonium chloride and the like are used, and as the double-sided surfactant, for example, lauryl betaine and the like can be used. It is also possible to use a reactive surfactant. From the viewpoint of the stability of the hydrolyzed condensate of the silane compound, an anionic surfactant can be preferably used, and a dodecylbenzene sulfonic acid type surfactant is particularly preferable.

The amount of these surfactants used is 0.001-1 with respect to 100 parts by weight of the silane compound (I).
0 parts by weight. It is more preferably 0.01 to 5 parts by weight.
When the amount of the surfactant is less than 0.001 part by weight, the storage stability of the water-soluble polymer (A), which is a hydrolysis-condensation product, is poor,
If it exceeds 10 parts by weight, the water resistance of the coating film may deteriorate, which is not preferable. No hydrolysis condensation reaction
It can be carried out simply by stirring in water under a temperature condition of ~ 200 ° C. A small amount of an aqueous solvent such as alcohol may be added.

The hydrolysis-condensation reaction can be represented by the following formula, for example, when tetraethoxysilane is used as the silane compound (I). Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH Si (OH) ₄ → SiO ₂ + 2H ₂ O

As described above, the silane compound undergoes polycondensation to be three-dimensionalized, and the water-soluble polymer (A) having a molecular weight of about 100 to 5,000 in terms of polystyrene is a film-forming property and a coating film. It is useful in terms of performance. This water-soluble polymer (A) further causes polymerization and three-dimensional reaction by heating during the subsequent coating film formation.

The coating composition of the present invention is an aqueous dispersion polymer (B) obtained by emulsion-polymerizing a radically polymerizable polymerizable monomer in water containing the above water-soluble polymer (A). is there. The presence of the water-dispersed polymer (B) not only improves the film-forming property of the composition of the present invention, but also serves to improve the flexibility and other physical properties of the coating film. In the present invention, by performing emulsion polymerization in the presence of the water-soluble polymer (A) to obtain the water-dispersed polymer (B), the crosslinking reaction of the water-soluble polymer (A) is controlled to cause gelation. It can prevent and make the coating composition more stable. Further, since it can be produced in a single reactor, the step of mixing both after polymerization in separate reactors is not required, which is simple in terms of the production process and is industrially very advantageous.

The radically polymerizable polymerizable monomer (hereinafter simply referred to as a polymerizable monomer) is a water-soluble polymer (A).
Having a functional group that can serve as a catalyst for a three-dimensional curing (hydrolysis condensation) reaction, such as a phosphoric acid group or a carboxyl group, so that the three-dimensional curing reaction can occur during subsequent film formation. It is preferable to include the polymerizable monomer (B-1), but the water-dispersed polymer (B) may be formed only with the other polymerizable monomer (B-2).

As the polymerizable monomer (B-1), 2- (meth) acryloyloxyethyl acid phosphate having a phosphoric acid group, acid phosphooxypolyoxypropylene glycol mono (meth) acrylate, acid phosphooxypolyoxy. Ethylene glycol mono (meth) acrylate, methacryloyloxyethyl acid phosphate monoethanolamine half salt, etc .;
(Meth) acrylic acid having a carboxyl group, 2- (meth) acryloxyethylsuccinic acid, 2- (meth) acryloxyethylphthalic acid, 2- (meth) acryloyloxyethylhexahydrophthalic acid, etc. Alternatively, they can be used as a mixture.

As the polymerizable monomer (B-2), methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, cyclohexyl (meth)
Acrylate, 4-t-butylcyclohexyl (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 (Meth) acrylic acid esters such as di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate; Aromatic vinyl compounds such as styrene, α-methylstyrene, divinylbenzene and their nuclear substitution derivatives; hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth A hydroxyl group-containing compound such as acrylate, 2-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 2- (meth) acryloyloxyethyl-2-hydroxyethylphthalic acid; glycidyl (meth) acrylates having a glycidyl group; Γ- (meth) acryloxypropyltrimethoxysilane having an alkoxysilyl group, γ- (meth)
Acryloxypropyltriethoxysilane; acrylonitrile, acrylamide, etc., among which 1
Use more than species.

The polymerizable monomer (B-1) is 0.1 to 30.
0 parts by weight, the polymerizable monomer (B-2) is 70.0 to 99.
It is preferable to configure the water-dispersed polymer (B) as 9 parts by weight [however, (B-1) + (B-2) is 100 parts by weight]. The phosphoric acid group or the carboxyl group introduced into the water-dispersed polymer (B) by the polymerizable monomer (B-1) serves as a catalyst for the three-dimensional reaction of the water-soluble polymer (A), and also a coating. Improves adhesion with the substrate.
However, if the polymerizable monomer (B-1) exceeds 30.0 parts by weight, the water resistance of the coating film may deteriorate. More preferably, the amount of the polymerizable monomer (B-1) used is 1.0 to 20.0 parts by weight, and more preferably 5.0 to 15.0 parts by weight, based on 100 parts by weight of all the polymerizable monomers. is there.

In the present invention, the polymerizable monomers (B-1) and (B-2) are selected so that the glass transition temperature (Tg) of the water-dispersed polymer (B) is -50 to 150 ° C. Preferably. If the Tg of the water-dispersed polymer (B) is too low, the resulting coating film may have tackiness. The preferred lower limit of Tg is -30 ° C, and more preferably 0 ° C.
Further, if Tg is too high, the flexibility of the coating film deteriorates. The preferable upper limit of Tg is 100 ° C, and more preferably 60 ° C. The Tg can be designed by calculating from the Tg when the selected polymerizable monomer is a homopolymer and the amount used.

The water-dispersed polymer (B) can be obtained by emulsion polymerization in water in which the water-soluble polymer (A) is dissolved. As described above, the silane compound (I) in an aqueous medium
After the hydrolysis and condensation reaction of, the known emulsion polymerization may be carried out by adding water if necessary. That is, the polymerizable monomers (B-1) and (B-2), a surfactant, a polymerization initiator, a chain transfer agent, a pH adjusting agent, and the like are added, and the mixture is added at 20 to 100 ° C. Polymerization is performed for about 0.5 to 30 hours. As the surfactant used here, the surfactants exemplified as being usable when the silane compound (I) is hydrolyzed and condensed can be mentioned as they are. The amount used is preferably 0.001 to 10 parts by weight based on 100 parts by weight of the total amount of polymerizable monomers. 0.00
If it is less than 1 part by weight, the stability of micelles during polymerization may be poor, and if it is more than 10 parts by weight, water resistance may be poor when it is used as a coating film.

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 with respect to 100 parts by weight of the total amount of the polymerizable monomers.
-5 parts by weight is preferred.

The coating composition of the present invention comprises
The water-soluble polymer (A) / water-dispersed polymer (B) is contained in a solid content weight ratio of 0.1 to 5. At this time, the water-soluble polymer is R ¹ _m —SiO 2 _{(4-m) / 2} and is converted to solid content in an absolutely dry state. A more preferable compounding ratio is (A) /
(B) is 0.5 to 3. When it is more than 5, the flexibility such as flexibility of the coating film is poor, and when it is less than 0.1, the chemical resistance and hardness are lowered.

It is possible to add an organic solvent 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, 2-propanol, 1-butanol, ethylene glycol, diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether; acetone, methyl ethyl ketone, etc. In addition to the above ketones, methyl acetate, tetrahydrofuran and the like can be mentioned, and one or more of these can be mixed and used. Of these, alcohols are preferably used. The amount of these organic solvents used is less than 35 parts by weight, preferably less than 30 parts by weight, and more preferably less than 10 parts by weight in the total solvent of the composition. If it exceeds 35 parts by weight, it is against the object of the present invention to provide an aqueous coating composition.

The composition of the present invention requires various inorganic or organic additives such as a curing agent, a wettability improver, a plasticizer, a defoaming agent, and a thickener, as long as the effects of the present invention are not impaired. It can also be added according to. Known water-soluble, water-insoluble or water-dispersible additives may be added as coating additives. Examples of water-soluble additives include water-soluble polymers such as polyvinyl alcohol. Examples of water-insoluble or water-dispersible additives include water-dispersible silica, alcohol-dispersible silica, talc, diatomaceous earth, calcium carbonate, clay, titanium dioxide, aluminum silicate,
Aluminum phosphate, alumina sol, magnesia sol,
Examples thereof include titania sol and zirconia sol.

The method for coating the substrate with the coating composition of the present invention is not particularly limited, and roll coating,
A dip coating method, a bar coating method, a nozzle coating method, or a combination thereof is adopted. Note that a known stainless steel plate surface treatment can be performed before the coating.

After coating, the coating film is cured and dried. It can be cured and dried at room temperature, but if it is to be cured and dried quickly, it will be at room temperature to 300 ° C, preferably 50 to 250.
It is good to heat dry at ℃. The thickness of the coating film is not particularly limited, but 0.001 to 100 μm, more preferably 0.01 to 40 μm is suitable after drying. When the thickness is less than 0.001 μm, the coating film is not uniform and pinholes are easily generated, and when the thickness is more than 100 μm, cracks are easily generated in the coating film, which is not preferable.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. The physical property evaluation methods used in the following examples are as follows.

[Physical Property Evaluation Method] Gobang Eye Test: A coating film coated on a stainless steel plate was carved with a cutter knife to form Goban stitches at 1 mm intervals of 100 × 100 mm, cellophane tape was pressure-bonded, and then peeled off. It was evaluated by the point method. 10 points (good) → 0 points (poor) Chemical resistance: A coating film coated on a stainless steel plate was subjected to a rubbing test 100 times with ethanol. ◯: No change in coating film ×: Whitening of coating film, dissolution of coating film Pencil hardness: Coating film coated on stainless steel plate,
It was performed according to JIS-K5400. Gobin eye Eriksen: A stainless steel plate coated with a cutter knife at 1 mm intervals of 100 x 100
mm scoring, extruded 5 mm Erichsen, pressed with cellophane tape and then peeled off, and the degree of peeling of the coating film was evaluated by a 10-point method. 10 points (good) → 0 points (poor) Storage stability: The coating composition was stored at 21 ° C,
Observation of state after 3 months ○: No change ×: Aggregation, gelation

Example 1 A four-necked flask equipped with a stirrer, a thermometer, a nitrogen introducing tube, and a reflux condenser was charged with 3.7 g of methyltrimethoxysilane, 3.1 g of tetraethoxysilane and 100 g of water at 50 ° C. The mixture was stirred for 2 hours to obtain a transparent solution of the water-soluble polymer A. To this water-soluble polymer solution, 55.5 g of water, 0.6 g of Hitenol N-08 (surfactant manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.),
Ammonium persulfate (0.10 g) was added, the atmosphere was replaced with nitrogen gas, the temperature was raised to 80 ° C., and butyl acrylate (12.5 g) was added.
Methyl methacrylate 11.3 g, methacrylic acid 3.2
g, 8.1 g of water, and 0.02 g of high tenol N-08
Was mixed and emulsified, and the liquid was continuously added dropwise over 3 hours to synthesize the water-dispersed polymer B. 80 after dropping
The mixture was heated at 0 ° C. for 1 hour, cooled, and filtered through a 200-mesh wire net to obtain a coating composition 1.

This coating composition 1 was applied to a stainless steel plate (SUS304) using a bar coater so that the thickness after drying would be 2.0 μm, and the composition was coated at 200 ° C. for 30 minutes.
Dried for seconds. The resulting coating film was transparent. The results of the physical property test of this coating film are shown in Table 1.

Examples 2 to 6 The same operations as in Example 1 were carried out with the compositions shown in Table 1 to obtain coating compositions 2 to 6. The results of the physical property tests are also shown in Table 1. The abbreviations of the compounds used in Table 1 are as follows. BA: Butyl acrylate MMA: Methyl methacrylate HEMA: 2-Hydroxyethyl methacrylate GMA: Glycidyl methacrylate MAA: Methacrylic acid AA: Acrylic acid MTMOS: Methyltrimethoxysilane ES: Tetraethoxysilane PTMOS: n-Propyltrimethoxysilane GPTMOS: γ- Glycidoxypropyl trimethoxysilane

[0034]

[Table 1]

Comparative Example 1 In Example 1, the procedure for obtaining the water-soluble polymer (A) was not performed, and only the water-dispersed polymer (B) was synthesized from the beginning. This water-dispersed polymer was applied to a stainless steel plate and dried as in Example 1. The resulting coating film was transparent.
The coating had a burrs eye test of 10, a chemical resistance of ×, a pencil hardness of 6B, and a burrs eye Erichsen of 10. The storage stability was good.

Comparative Example 2 Only the water-soluble polymer (A) obtained in Example 1 was applied to a stainless steel plate and dried in the same manner as in Example 1. The resulting coating film was transparent. This coating film had a goggles eye test of 0, a chemical resistance of ◯, a pencil hardness of 4H, and a gougins eye Erichsen of 0. The storage stability was x.

[0037]

The coating composition of the present invention is a water-based coating composition obtained by polymerizing a water-dispersed polymer in the presence of a silane-based water-soluble polymer having excellent chemical resistance and hardness. Therefore, it has good storage stability, no concern about environmental pollution, and is excellent in water resistance, chemical resistance, weather resistance, stain resistance, heat resistance, workability, high hardness and flexibility. It forms a flexible coating. Further, since it is possible to produce a coating composition in a single reactor, it is not necessary to use a conventional process of mixing separately polymerized products in a plurality of reactors, which is industrially possible. It is advantageous.

Claims (3)

[Claims] 1. A silane compound (I) R ¹ _m Si (OR ² ) _n ... (I) represented by the following general formula (wherein R ^{1 s} may be the same or different, and is a hydrogen atom or a lower alkyl group). , An aryl group or an unsaturated aliphatic residue, R ² represents a hydrogen atom, a lower alkyl group or an acyl group, m is 0, 1 or 2, n is 2, 3 or 4
And m + n is 4), a water-soluble polymer (A) obtained by hydrolysis and condensation in water, and a polymerizable monomer capable of radical polymerization in the presence of the water-soluble polymer (A). A water-dispersed polymer (B) obtained by emulsion-polymerizing a body in water, wherein the water-soluble polymer (A) and the water-dispersed polymer (B) are
A coating composition containing (A) / (B) in a solid content of 0.1 to 5 by weight. 2. The water-soluble polymer (A) is hydrolyzed and condensed in water containing a surfactant.
The coating composition as described in 1. 3. The water-dispersed polymer (B) comprises 0.1 to 30.0 parts by weight of a radically polymerizable polymerizable monomer (B-1) having a phosphoric acid group or a carboxyl group, and other components. Radical polymerizable polymerizable monomer (B-2) 70.0 to
99.9 parts by weight [(B-1) + (B-2) is 1
00 parts by weight] is emulsion-polymerized in water to obtain the coating composition according to claim 1 or 2.