JP2001181556A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition which shows an excellent shelf stability and forms a coated film which shows an excellent antifouling property and allows no crack over time. SOLUTION: The aqueous coating composition essentially comprises (A) a synthetic resin emulsion containing a reactive silyl group and (B) a polysiloxane compound having a polyoxyalkylene chain with a -OH group at its one end and a hydroxy value of from 5 to 150 KOH mg/g, and contains, against 100 pts.wt. solid content of component (A), from 0.1 to 8.0 pts.wt. component (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention can be used for surface finishing of various materials such as metal, glass, porcelain tile, concrete, siding board, extruded plate, plastic and the like, and is mainly used for buildings and civil engineering structures. And the like.

[0002]

2. Description of the Related Art In recent years, in the field of paints used for architectural and civil engineering structures, a shift from a solvent-based paint using an organic solvent as a solvent to a water-based paint using water as a solvent is being made. This is to reduce the health hazards for painters and residents,
It is carried out for the purpose of reducing atmospheric environmental pollution, and is becoming more and more aqueous every year.

[0003] However, a coating film formed by a water-based paint generally has a lower hardness than a coating film of a solvent type paint and tends to permeate contaminants. It is often difficult to remove the dirt from the surface. In particular, in urban and suburban areas, oily pollutants are floating in the air due to exhaust gas from automobiles and other sources, and paint film contamination by these pollutants greatly impairs aesthetics. It is a factor.

As a technique for improving the stain resistance of a water-based paint, there is generally a method of increasing the glass transition temperature (hereinafter referred to as "Tg") of a resin. In this method, it is necessary to introduce a monomer having a high Tg such as styrene or methyl methacrylate. However, simply increasing the ratio of such a monomer does not provide a sufficient effect of improving the stain resistance, and also decreases the weather resistance. Is sometimes not preferred.

As another method, there is a method of imparting a crosslinking property by introducing a silicon component. This method introduces a reactive silyl group-containing compound into a synthetic resin emulsion,
By reacting the functional groups, the hardness of the coating film is increased. In this method, the hardness of the coating film is increased by increasing the ratio of the silicon component,
Stain resistance can be exhibited. However, with the increase in the amount of the silicon component, the remaining reactive silyl groups react with each other after film formation, and the internal stress of the coating film rapidly increases, thereby causing a problem that the coating film is easily cracked.

On the other hand, in a paint using a synthetic resin emulsion, various organic solvents are usually mixed in order to secure a sufficient film-forming property. These organic solvents have a function of plasticizing the synthetic resin emulsion and increasing the fusion property between the emulsion particles. However, when a normal organic solvent is used for the synthetic resin emulsion having a reactive silyl group, the reactive silyl groups tend to act due to the plasticizing function thereof, so that the storage stability is reduced and the practical use is difficult. There is a problem that a paint cannot be obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is capable of forming a coating film which is excellent in stain resistance and which does not crack over time. Another object of the present invention is to obtain an aqueous coating composition having excellent storage stability.

[0008]

Means for Solving the Problems In order to solve these problems, the present inventors have conducted intensive studies. As a result, a synthetic resin emulsion having a reactive silyl group and a polysiloxane compound having a specific side chain have been developed. Were found to be effective, and the present invention was completed.

That is, the present invention provides the following aqueous coating composition. 1. (A) a synthetic resin emulsion having a reactive silyl group, and (B) a polysiloxane compound having a polyoxyalkylene chain having one terminal being an -OH group and having a hydroxyl value of 5 to 150 KOHmg / g. A water-based coating composition characterized by containing 0.1 to 8.0 parts by weight of (B) based on 100 parts by weight of the solid content of (A). 2. The aqueous coating composition according to 1., further comprising (C) 3 to 50 parts by weight of an organic solvent having a solubility in water of 20% by weight or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail along with its embodiments.

The aqueous coating composition of the present invention comprises (A) a synthetic resin emulsion having a reactive silyl group (hereinafter referred to as a synthetic resin emulsion).
"(A) component"), and (B) a polysiloxane compound having a polyoxyalkylene chain having an -OH group at one end (hereinafter, referred to as "(B) component").

The component (A) in the composition of the present invention is a synthetic resin emulsion having good weather resistance, stain resistance, yellowing resistance, water resistance, chemical resistance, etc., and (a) a reactive silyl group-containing compound. (Hereinafter referred to as “component a”) as an essential component.

In the component (A), the method of introducing the component a is not particularly limited, and various methods can be employed. For example, a method of copolymerizing a reactive silyl group-containing vinyl monomer. A method of reacting a silane compound after copolymerizing a reactive silyl group-containing vinyl monomer; a method of reacting a functional group in a resin with a coupling agent having a functional group capable of reacting with the functional group; A method of reacting a silane compound after reacting a functional group therein with a coupling agent having a functional group capable of reacting with the functional group, and the like.

As the reactive silyl group, an alkoxyl group, a phenoxy group, a mercapto group, an amino group,
Halogen and the like are bonded.

The vinyl monomer having a reactive silyl group is a compound having a reactive silyl group and a polymerizable double bond. Examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri-n. -Butoxysilane, vinyl tris (β-methoxyethoxy)
Silane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether, γ
-(Meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, vinylmethyldimethoxysilane, methyldimethoxysilylethyl vinyl ether,
Methyl dimethoxysilylpropyl vinyl ether and the like can be mentioned, and one or more of these can be used.

As the silane compound in (1), those having two or more reactive silyl groups in one molecule are used. For example, tetrafunctional alkoxysilanes such as tetraethoxysilane, tetramethoxysilane and tetrabutoxysilane; methyl Trimethoxysilane, methyltriethoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, phenyl Trifunctional alkoxysilanes such as trimethoxysilane, phenyltriethoxysilane, phenyltributoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, diethyldisilane Toxysilane, diethyldiethoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldibutoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane Bifunctional alkoxysilanes such as silane; tetrachlorosilane, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, dimethyldichlorosilane, diethyldichlorosilane, diphenyldichlorosilane, methylphenyldichlorosilane, etc. Chlorosilanes: tetraacetoxysilane, methyltriacetoxysilane, phenyltriacetoxy Orchids, dimethyldiacetoxysilane, such as acetoxy silanes such as diphenyl diacetoxy silane and the like, can be used one or two or more thereof. Further, a compound having one reactive silyl group in one molecule can be used in combination.

Examples of the combination of the functional groups include a hydroxyl group and an isocyanate group, an amino group and an isocyanate group, a carboxyl group and an epoxy group, an amino group and an epoxy group, and an alkoxysilyl group. The coupling agent is, for example, a compound having at least one or more reactive silyl groups and other substituents in one molecule. Specifically, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane Γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N- (β-aminoethyl)
-Γ-aminopropylmethyldimethoxysilane, N-
(Β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ
-Aminopropyltriethoxysilane, isocyanate-functional silane and the like, and one or more of these can be used.

The weight ratio of the component a in the component (A) is as follows:
Usually, 0.1% in terms of SiO _{2 in} the resin solid content of the component (A).
1 to 70% by weight, but in the present invention, in particular, 0.3 to 3% by weight.
It is effective when it is 0% by weight.

The term "SiO ₂ equivalent" means that a compound having a Si--O bond is completely hydrolyzed and then converted to silica (SiO ₂ ) when calcined at 900 ° C., and is expressed in terms of the remaining weight. It is. In general, alkoxysilane, silicate, and the like have a property of reacting with water to cause a hydrolysis reaction to form silanol, and to cause a condensation reaction between silanols or silanol and alkoxy. When this reaction is performed to the ultimate, silica (SiO ₂ ) is obtained. These reactions are represented by the general formula: RO (Si (OR) ₂ O) _n R +
It is represented by a reaction formula of (n + 1) H ₂ O → nSiO ₂ + (2n + 2) ROH, and the amount of the remaining silica component is converted based on this reaction formula.

The copolymerizable monomer of the component (A) is not particularly limited, but an acrylic monomer can be suitably used. Examples of the acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and 2-ethylhexyl (meth).
Alkyl-containing (meth) acrylic monomers such as acrylate and cyclohexyl (meth) acrylate; hydroxyl-containing (meth) acrylic monomers such as 2-hydroxyethyl (meth) acrylate; ethylene such as (meth) acrylic acid Unsaturated carboxylic acids; Amino group-containing (meth) acrylic monomers such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylate; and amides such as (meth) acrylamide and ethyl (meth) acrylamide ( (Meth) acrylic monomers; nitrile group-containing (meth) acrylic monomers such as acrylonitrile; and epoxy group-containing (meth) acrylic monomers such as glycidyl (meth) acrylate.

In the component (A), in addition to the above monomers, aromatic hydrocarbon vinyl monomers such as styrene, methylstyrene, chlorostyrene and vinyltoluene; maleic acid, itaconic acid, crotonic acid, fumaric acid, Α, β-ethylenically unsaturated carboxylic acids such as citraconic acid; sulfonic acid-containing vinyl monomers such as styrene sulfonic acid and vinyl sulfonic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; vinyl chloride, vinylidene chloride And chlorine-containing monomers such as chloroprene; hydroxyl-containing alkyl vinyl ethers such as hydroxyethyl vinyl ether and hydroxypropyl vinyl ether; alkylene glycols such as ethylene glycol monoallyl ether, propylene glycol monoallyl ether and diethylene glycol monoallyl ether Α-olefins such as ethylene, propylene and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl pivalate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether and cyclohexyl vinyl ether; ethyl allyl Allyl ethers such as ether and butyl allyl ether can also be used. In addition, an ultraviolet absorber containing an ethylenically unsaturated double bond, a light stabilizer containing an ethylenically unsaturated double bond, and the like can also be used.

The emulsifier used for the polymerization is appropriately selected from anionic, cationic, nonionic, amphoteric, nonionic-cationic, nonionic-anionic, non-reactive, and reactive. Use alone or in combination. Of these, the use of a reactive emulsifier having a polyoxyalkylene chain and an unsaturated double bond is preferable because it can improve crack prevention, storage stability, and water resistance.

As the polymerization initiator, ordinary radical initiators can be used, such as a persulfate such as ammonium persulfate, a redox initiator comprising a combination of hydrogen peroxide and sodium hydrogen sulfite, and a first radical initiator. Examples thereof include a system in which an inorganic initiator such as iron salt and silver nitrate is mixed, a dibasic acid peroxide such as disuccinic peroxide and diglutaric peroxide, and an organic initiator such as azobisbutyronitrile. The amount of the polymerization initiator is usually 0.01 to 100 parts by weight of the monomer.
It is about 5 parts by weight.

The weight average molecular weight of the component (A) is 30,000
More preferably, it is more preferably 50,000 or more.
When the molecular weight is 30,000 or more, weather resistance, stain resistance, water resistance, and the like can be improved. Also,
It is desirable that the minimum film forming temperature of the component (A) be 0 to 80 ° C. When the minimum film forming temperature is lower than 0 ° C., the stain resistance tends to decrease, and when the minimum film forming temperature is higher than 80 ° C., the coating film is liable to crack.

The component (B) is a component that imparts stain resistance and crack resistance to the formed coating film of the composition of the present invention, and has a function of improving the storage stability of the coating.

The component (B) is a compound having, on the side chain and / or the terminal, a polyoxyalkylene chain having an —OH group at one end in the main chain composed of polysiloxane. It has one or both.

[0027]

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[0028]

Embedded image

(R ¹ and R ² are an alkyl group or a phenyl group, R ³ is an alkylene group or a phenylene group, R ⁴ is an alkylene group having 1 to ⁴ carbon atoms, and may have the same or different carbon atoms. Integer greater than or equal to 1.)

The component (B) can be produced, for example, by a hydrosilylation reaction between an allylated polyether compound and methyl hydrogen silicone oil.

The hydroxyl value of the component (B) is from 5 to 150 KO.
Hmg / g, and 10-100 KOHmg / g
g, more preferably 40 to 80 KOH mg / g.
If the hydroxyl value is less than 5 KOHmg / g, the stain resistance will decrease over time, and sufficient storage stability will not be ensured. If it is larger than 150 KOHmg / g, cracks are likely to occur and storage stability tends to decrease.

Examples of the alkylene oxide include methylene oxide, ethylene oxide, propylene oxide, butylene oxide and the like. Of these, ethylene oxide and / or propylene oxide are preferably used.

The component (B) has a number average molecular weight of 1,000 to 5,
0000 is desirable. Of these, the number average molecular weight of the alkylene oxide chain is preferably from 40 to 30,000. When the number average molecular weight of the alkylene oxide chain is less than 40, sufficient physical properties cannot be obtained in stain resistance, crack prevention and storage stability. Conversely 300
If it is larger than 00, the water resistance, stain resistance and weather resistance will be reduced.

The content of the component (B) is 0.1 to 8.0 parts by weight based on 100 parts by weight of the solid content of the component (A).
When the content of the component (B) is less than 0.1 part by weight,
Sufficient physical properties cannot be obtained in stain resistance, crack prevention and storage stability. If the amount is more than 8.0 parts by weight, water resistance, weather resistance, crack prevention, recoatability, and storage stability will be reduced.

In the present invention, since a specific amount of the component (B) having a specific hydroxyl value is contained, the terminal (B) of the component (B)
It is presumed that the OH group moderately interacts with the reactive silyl group of the component (A) to suppress a rapid reaction between the reactive silyl groups. As a result, the occurrence of cracks in the coating film can be prevented. Further, even during the storage of the paint, the viscosity fluctuation due to the reaction between the silyl groups of the component (A) can be suppressed by the steric hindrance effect of the component (B). Furthermore, in the present invention, the surface of the coating film can be hydrophilized by the polyoxyalkylene chain of the component (B) to impart stain resistance.

In the present invention, it is desirable to contain (C) an organic solvent having a solubility in water of 20% by weight or more (hereinafter referred to as "component (C)"). By containing such a component (C), it is possible to ensure film-forming properties at low or normal temperature and to improve the storage stability of the paint.

As the component (C), for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol isopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether Ter, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, 1-3 butanediol, 1-5 pentanediol, diacetone alcohol, N-methylpyrrolidone, and the like. One or more of these may be used. Can be.

The content of the component (C) is 3 to 50 parts by weight based on 100 parts by weight of the solid content of the component (A). (C)
When the content of the component is less than 3 parts by weight, it is difficult to secure sufficient physical properties in storage stability, and cracks are likely to occur during film formation. If it is more than 50 parts by weight, storage stability tends to decrease. In addition, as the organic solvent,
As long as the effect of the present invention is not impaired, an organic solvent other than the component (C) may be used in combination.

The composition of the present invention preferably has a pH of 5 to 10, more preferably 6 to 8. By adjusting the pH within such a range, sufficient storage stability and physical properties of the coating film can be ensured. Compounds used for pH adjustment include inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid and sulfuric acid; organic acids such as formic acid and acetic acid; sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium carbonate, ammonia, sodium acetate, Inorganic bases such as ammonium acetate, sodium silicate, and sodium phosphate; organic bases such as methylamine, dimethylamine, triethylamine, and triethanolamine; and one or more of these may be used. it can.

The composition of the present invention may further contain, if necessary, inorganic coloring pigments, organic coloring pigments, extender pigments, and the like, which are commonly used in paints. In addition, plasticizers, preservatives, fungicides, defoamers, thickeners, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, matting agents, ultraviolet absorbers, which do not affect the present invention, Additives such as antioxidants may be used alone or in combination.

Examples of the inorganic color pigments include titanium oxide, carbon black, ferric oxide (red iron oxide), yellow iron oxide, ocher, ultramarine, and cobalt green. Naphthol,
Pyrazolone, anthraquinone, perylene, quinacridone, disazo, isoindolinone, benzimidazole, phthalocyanine, quinophthalone and the like can be used. Examples of the extender pigment include extender pigments such as heavy calcium carbonate, clay, kaolin, talc, precipitated barium sulfate, and barium carbonate.

The composition of the present invention can be used for metal, glass, porcelain tile, concrete, siding board, extruded board,
It can be used for surface finishing of various materials such as plastic, and is mainly used for protection of buildings such as buildings and civil engineering structures. At this time, the aqueous coating composition of the present invention comprises:
It is applied to the final surface and can be applied directly to the substrate, or some surface treatment (sealer,
It is also possible to apply the coating after applying a surface treatment such as a surfacer, a filler or the like), but the coating is not particularly limited. As a coating method, it can be applied by various methods such as brush coating, spray coating, roller coating, roll coater, flow coater and the like. Further, the surface of the building material can be pre-coated at a factory or the like.

[0043]

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

[Preparation of paint] Using the raw materials shown in Tables 1 and 2, paints were prepared according to the formulations shown in Table 3, and each test was conducted.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[Test Method] Storage Stability The prepared coating composition was stored in a thermostat at 50 ° C. for 30 days, and the change in viscosity was confirmed. The evaluation is as follows. ：: viscosity change of less than 10% ○: viscosity change of 10% or more to less than 30% Δ: viscosity change of 30% or more to less than 50% ×: viscosity change of 50% or more

A SK Clear Sealer (acrylic resin emulsion base coating material; manufactured by SK Chemical Co., Ltd.) was spray-coated on a flexible plate of 150 × 70 × 3 mm to a dry film thickness of 30 μm. After drying for 8 hours in the state, the prepared coating composition was spray-coated so as to have a dry film thickness of 40 μm to prepare a test body. JI
20 ± according to S K5660 4.13 (1995)
After being immersed in water at 2 ° C. for 18 hours, it was immediately cooled in a thermostat kept at −20 ± 3 ° C. for 3 hours, and then heated in another thermostat kept at 50 ± 3 ° C. for 3 hours. After repeating this operation 10 times, the film was left in a standard state for about 1 hour, and the state of the coating film surface was visually observed. At this time, those in which no crack or peeling occurred were evaluated as ○, those in which minute cracks occurred were evaluated as △, and those in which cracks and peeling occurred clearly were evaluated as ×.

Accelerated contamination test 1 SK # 100 was placed on an aluminum plate of 150 × 75 × 0.8 mm.
No. 0 primer (epoxy resin base coating material; manufactured by SK Chemicals Co., Ltd.) was spray-coated so as to have a dry film thickness of 30 μm, and dried for 8 hours under standard conditions. A test piece was prepared by spray coating to a thickness of 40 μm. The prepared test specimen was 7
After drying and curing for one day, a 15% by weight aqueous dispersion of carbon black was dropped onto the coating surface so as to have a diameter of 20 mm and a height of 5 mm, and was left in a constant temperature room at 50 ° C. for 2 hours. Thereafter, the film was washed in running water, and the degree of contamination on the coating film surface was visually evaluated. The evaluation is as follows. ◎: No trace is observed ○: Only slight trace is observed △: Trace is observed ×: Remarkable trace is observed

Accelerated Soil Test 2 Specimens were prepared in the same manner as in Accelerated Soil Test 1 and immersed in a 0.1% by weight aqueous carbon black dispersion at room temperature for 2 hours. After drying at room temperature for 2 hours, the degree of contamination on the coating film surface was evaluated based on the difference in lightness (ΔL). For measuring the lightness difference, a TC-1800 type color difference meter manufactured by Tokyo Denshoku Co., Ltd. was used.

[Test results]

[Table 4]

Table 4 shows the test results. In Examples 1 to 6, which are the compositions of the present invention, good results were obtained in all tests. In particular, Examples 2 to 4 in which the hydroxyl value of the polysiloxane compound is within the most preferable range, and which contain an organic solvent having high solubility in water, have more excellent results in storage stability and stain resistance. . On the other hand, Comparative Examples 1 and 2 in which the hydroxyl value of the polysiloxane compound is out of the range of the present invention, Comparative Examples 3 and 4 in which the content of the polysiloxane compound is out of the range of the present invention, Comparative Examples not containing the polysiloxane compound In No. 5, sufficient results could not be obtained.

[0054]

According to the present invention, it is possible to obtain an aqueous coating composition which is excellent in stain resistance, can form a coating film which does not crack over time, and has excellent storage stability. Can be. Further, since the composition of the present invention is a one-pack type, it is a material that can reduce the complexity of the coating operation.

Claims (2)

[Claims] (A) a synthetic resin emulsion having a reactive silyl group, (B) a polyoxyalkylene chain having one end having an --OH group, and a hydroxyl value of 5 to 150 KOH mg.
/ G of a polysiloxane compound,
(B) is added in an amount of 0.1 to 100 parts by weight of the solid content of (A).
An aqueous coating composition containing 8.0 parts by weight. 2. The method according to claim 1, further comprising: (C) a solubility in water of 20 wt.
The aqueous coating composition according to claim 1, wherein the composition contains 3 to 50 parts by weight of an organic solvent.