JPH10219140A - Resin emulsion for weather-resistant coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin emulsion which can give a coating material capable of giving a coating film having excellent gloss inherent in the constituent acrylic resin binder, pigment dispersibility and weather resistance on the level near to that of e.g. a fluoro resin by incorporating a specified amount of units of a light-stable-group-containing monomer and a specified amount units of an alkoxysilyl-containing monomer in the resin of a resin emulsion. SOLUTION: 0.1-10wt.% units of a light-stable-group-containing monomer (a) and 0.1-10wt.% units of an alkoxysilyl monomer (b) are contained in 100wt.% resin of a resin emulsion. It is also possible to incorporate 0.1-10wt.% units of an ultraviolet-absorbing-group-containing monomer (c) in the resin. This can provide further improved weather resistance. The monomers which is copolymerized with monomers (a) to (c) is desirably an alkyl (meth)acrylate. Monomer (a) is desirably a compound of formula I (wherein R1 is H or CN; R2 , R3 and R4 are each H or an alkyl; and X is O or N), and monomer (b) is desirably a compound of formula II.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin emulsion for a paint used as a binder for a water-based paint having excellent weather resistance, and more particularly to an emulsion of a resin excellent in durability against deterioration by ultraviolet rays and visible rays. Is provided. The resin emulsion of the present invention can be used for paints for a wide range of uses such as home appliances, steel equipment, large structures, automobiles, buildings, building materials, and wood.

[0002]

2. Description of the Related Art Water-based paints are being used in place of solvent-based paints in consideration of environmental pollution and the effects on the human body. Water-based paints using an acrylic resin emulsion as a binder are often used because they satisfy the properties required for paint resins such as dispersion stability. However, when the conventional acrylic resin-based emulsion paint is subjected to an accelerated weather resistance test using a sunshine weather meter, its gloss retention is about 1000 hours, and it is difficult to use it in applications where long-term weather resistance is required. Has a problem. In order to improve the long-term weather resistance, an additive called a weather-resistant agent such as an ultraviolet absorber or an antioxidant which absorbs ultraviolet rays, which has a great influence on the deterioration of the resin molecular chain, is also used.

[0003] Also, Japanese Patent Application Laid-Open No. 3-128978 discloses a technique for copolymerizing a polymerizable ultraviolet-stable monomer.

In recent years, in an accelerated weathering test using a sunshine weather meter, gloss retention was 4000 to 5
Fluorine-based resins, silicone-based resins, and the like are being put into practical use as coating resins having excellent long-term weather resistance over 000 hours.

[0005]

However, in a system in which a weathering agent is added to an acrylic resin-based coating, although a certain effect is observed in improving the weathering resistance, the weathering agent is volatilized and runs off due to rain after bleed-out. There is a problem that the sustainability is poor due to such factors. In the technique disclosed in Japanese Patent Application Laid-Open No. Hei 3-12878 to prevent this, the use of a monomer containing a cycloalkyl group has been improved as an essential component, but the level of weather resistance is still insufficient. Not really.

Further, fluororesins and silicone resins are inferior to acrylic resins in terms of gloss and pigment dispersibility.

Therefore, an object of the present invention is to make use of the excellent properties of a conventional acrylic resin binder such as glossiness and pigment dispersibility as a coating resin, and to maintain glossiness of a fluororesin or silicone resin. It was close to the standard,
An object of the present invention is to provide an improved acrylic resin.

[0008]

According to the present invention, (a) 0.1 to 10% by weight of a monomer unit containing a photostable group, and (b) an alkoxysilyl group are contained in 100% by weight of a resin component of a resin emulsion. The present invention relates to a coating resin emulsion having excellent weather resistance, characterized by containing 0.1 to 10% by weight of a contained monomer unit.

The light-stable group in the light-stable group-containing monomer is called an amino group or a hydroxyl group having a bulky substituent having a steric hindrance effect, a so-called hindered amino group or a hindered alcohol group. The light-stable group is bonded to a polymerizable unsaturated group to form a light-stable group-containing monomer. By copolymerization of the monomer to the molecular chain of the coating binder resin, the weathering agent does not volatilize, or the bleed-out does not reduce the effect of being washed out by rain or the like, and the resin molecules form a crosslinked structure. By the action, a resin emulsion for paint having excellent weather resistance is obtained.

When the amount of the monomer having a photostable group as the component (a) is 0.1% by weight or less in the resin component, the effect is not sufficient, and the effect is increased even when 10% by weight or more is used. Instead, the cost is rather high. When the amount of the component (b) in the resin component is 0.1% by weight or less, the effect is not sufficient.
Even if it is used in an amount of 0% by weight or more, the effect is not increased and the cost is rather increased.

According to a second aspect of the present invention, there is provided a coating composition characterized in that the composition according to the first aspect further comprises (c) 0.1 to 10% by weight of a monomer unit having an ultraviolet absorbing group. The present invention relates to a resin emulsion. The ultraviolet absorber as the component (c) is a compound that absorbs ultraviolet light capable of exciting and breaking a chemical bond of a resin molecule and contributing to an improvement in weather resistance of the resin. In addition, the improvement of weather resistance can be improved.

The amount of the component (c) in the resin component is also the same as that described in the above (a).
As in the case of the component and the component (b), the effect is not sufficient at 0.1% by weight or less, and the effect does not increase even if used at 10% by weight or more, and the cost is rather high.

As the light-stable group-containing monomer, it is preferable to use a monomer represented by the chemical formula (Formula 4).

[0014]

Embedded image(In this equation, R₁Is H or CN, R_Two, R_ThreeIs each
H, CH_ThreeOr C_TwoH _FiveEven if they are the same or different
Well, R_FourIs H, an alkyl group having 1 to 18 carbon atoms or -C
OC (R_{2 '}) = CH (R_{3 '}) [R_{2 '}, R_{3 '}Is H,
CH_ThreeOr C_TwoH _FiveAnd may be the same or different
No. And X represents a nitrogen atom or an oxygen atom. )

When X is a nitrogen atom, it is an imino group, and may be -NH- or -NR- (R is a lower alkyl group). It is considered that the nitrogen atom to which R ₄ is bonded in the compound represented by Chemical Formula ₄ mainly contributes to the improvement of weather resistance.

Further, the alkoxysilyl group-containing monomer is preferably represented by a chemical formula (Formula 5).

[0017]

Embedded image (In this formula, R ₅ represents H or CH ₃ , R ₆ represents an alkyl group having a simplest number of 1 to 3, and Y represents an alkylene group having a simplest number of 1 to _6. ) They may be the same or different from each other.

It is considered that the alkoxysilyl group-containing monomer mainly contributes to the improvement of weather resistance and solvent resistance by forming a crosslinked structure between molecules of the coating binder resin.

The monomer having an ultraviolet absorbing group in the present invention is preferably represented by the following chemical formula (Formula 6).

[0020]

Embedded image (In this formula, R ₇ is H or CH ₃ , Z is a simple prime number 1
To 6 alkylene groups. )

It is considered that the conjugated double bond in the molecule represented by the chemical formula (6) absorbs ultraviolet rays, and thereby greatly improves the weather resistance of the resin emulsion of the present invention due to a synergistic effect with the light stabilizer. Can be

[0022]

DETAILED DESCRIPTION OF THE INVENTION Monomer component (a) containing a photostable group
As the compound which can be preferably used in the present invention, 4-hydroxy-2,2,6,6-tetramethylpiperidine,
-Amino-2,2,6,6-tetramethylpiperidine,
4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 4-amino-1,2,2,6,6-pentamethylpiperidi, 4-amino-4-cyano-2,2,6 ,
6-tetramethylpiperidine, 1- (meth) acryloyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-amino-4
-Cyano-2,2,6,6-tetramethylpiperidine,
1-crotonoyl-4-hydroxy-2,2,6,6-
Acrylic acid, methacrylic acid, or esters or amides such as crotonic acid formed by using a hydroxyl group or an amino group of a compound such as tetramethylpiperidine can be exemplified.These can be used alone or in combination of two or more. Can be used.

The alkoxysilyl group-containing monomer (b) used in the present invention includes vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and γ-methacryloxypropyltrimethoxy. Examples thereof include silane and the like. Particularly, in the chemical formula represented by the above formula (5), R ₅ is CH ₃ , R
It is preferable to use γ-methacryloxypropyltrimethoxysilane, which is a monomer in which ₆ is a methyl group and Y is —CH ₂ —CH ₂ —CH ₂ — (propylene group), from the viewpoint of characteristics, price, and the like.

In the present invention, the above-mentioned (a) monomer containing a photostable group, (b) monomer containing an alkoxysilyl group, and (c) a monomer having an ultraviolet absorbing group used as required The monomer copolymerized with the monomer is mainly a (meth) acrylic monomer. Here, the (meth) acrylic monomer means a monomer containing one or both of a derivative based on acrylic acid and a derivative based on methacrylic acid.

In the present invention, it is also preferable to copolymerize another ultraviolet-absorbing monomer in order to improve the durability against ultraviolet rays.
Examples thereof include hydroxy-4- [3- (meth) acryloxy-2-hydroxypropoxy] benzophenone and 2,2′-dihydroxy-4- [3- (meth) acryloxy-2-hydroxypropoxy] benzophenone.

Typical examples of the (meth) acrylic acid monomer include acrylic acid alkyl esters and methacrylic acid alkyl esters, and specific examples thereof include the following compounds.

As the alkyl acrylate, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isobonyl acrylate and the like can be used. Examples of the methacrylate include methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, isobonyl methacrylate, and tetrahydrofurfuryl methacrylate. These may be used alone or in combination of two or more.

A monomer other than the (meth) acrylic acid-based monomer can be used as a resin material for a coating material of the present invention, if necessary. Specifically, the following monomers are exemplified. Can be shown. Aromatic monomers such as styrene, vinyltoluene and α-methylstyrene Vinyl esters such as vinyl acetate Halogen-containing monomers such as vinyl chloride and vinylidene chloride Vinyl ethers Cyano group-containing monomers such as acrylonitrile N- Dimethylaminoethyl (meth) acrylate, 4
-Nitrogen-containing monomers such as vinylpyridine, vinylimidazole and (meth) acrylamide

Further, in addition to these monofunctional monomers, divinylbenzene,
Monomers that contribute to the formation of a crosslinked structure, such as diallyl phthalate and ethylene glycol dimethacrylate, can be used together. Among these monomers, the use of aromatic monomers, particularly styrene, is inexpensive, has good compatibility with other components, and contributes to improving the water resistance of the formed coating film. It is preferable from the point of view.

Monomers other than the above-mentioned (meth) acrylic acid-based monomers and other than the above-mentioned monomers, if necessary, OH
A monomer having a functional group such as a group, a COOH group, or a sulfonic acid group is also copolymerized. Examples of the monomer having such a functional group include the following. a) Monomer having OH group: hydroxyethyl (meth)
Acrylate, hydroxypropyl (meth) acrylate, allyl alcohol, caprolactone-modified hydroxy (meth) acrylate (manufactured by Daicel Chemical Industries, Ltd.),
Mono (meth) acrylate of bishydroxyethyl phthalate and the like. b) Monomers having COOH groups: acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride and the like. c) a monomer having a sulfonic acid group: vinyl sulfonic acid,
Styrenesulfonic acid, sulfoethyl (meth) acrylate and the like. d) acidic phosphate ester-based monomers: 2- (meth) acryloxyethyl acid phosphate, 2- (meth) acryloxypropyl acid phosphate, 2- (meth) acryloxy-3-chloropropyl acid phosphate, 2- (meth) acryloxyphenylethylphenylphosphoric acid and the like. e) Monomer having glycidyl group: glycidyl (meth)
Acrylate and the like.

As the polymerization initiator component used in the synthesis of the coating resin of the present invention, those well known to those skilled in the art can be used. As a specific compound, it is preferable to use a water-soluble initiator such as potassium persulfate or ammonium persulfate. However, a water-insoluble initiator such as azobisisobutyronitrile, benzoyl peroxide, MEK peroxide, tK -Butyl hydroperoxide and the like can also be used. Further, a redox catalyst comprising a combination of a radical generator and a sulfite can also be used. Furthermore, it is also possible to use these persulfates or peroxides, metal ions and reducing agents such as L-ascorbic acid and ersorbic acid.

In the emulsion polymerization, a chain transfer agent is used,
Adjusting the molecular weight is also a preferred embodiment. As the chain transfer agent, compounds known to those skilled in the art can be used.
-Mercaptans such as dodecyl mercaptan and lauryl methyl mercaptan can be exemplified as typical ones.

An emulsifier may be used, if necessary, to emulsify the monomers constituting the resin. As such an emulsifier, a surfactant known to those skilled in the art is used. In order to form a protective colloid, a water-soluble polymer compound can also be used, and cellulose derivatives such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, water-soluble polyurethane resins, water-soluble acrylic resins, polyvinylpyrrolidone-based resins, and polyvinyl alcohol It is also preferable to use a compound that forms a protective colloid in combination.

In the resin emulsion of the present invention, a light stabilizer, an ultraviolet absorber and an antioxidant, which are addition-type weathering agents, may be added at the production stage or after the production. As described above, such an added type weathering agent gradually bleeds out and is washed away by rain or the like, and has no effect on long-term weather resistance improvement. An auxiliary effect can be expected in which the effect of the polymerized monomer unit having a weather-resistant functional group is exhibited for a long period of time.

[0035]

Embodiments of the present invention will be described below. (Synthesis Example) A method for synthesizing a resin emulsion is as follows. The parts by weight are simply indicated as "parts". 60 parts of water and 2.0 parts of reactive surfactant New Frontier A-229E (Daiichi Kogyo Seiyaku Co., Ltd.) are added to a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. Then, the mixture was heated with stirring while blowing in nitrogen gas, and the liquid temperature was adjusted to 75 ° C. In this state, 5% of the emulsion containing the monomers shown in the following (Table 1) and 10% of the aqueous solution of the initiator were used.
Was added. After stirring, the remaining emulsion and aqueous initiator solution were further added dropwise over 3 hours to react, and then a complete reaction was carried out at the same temperature for 1 hour. After cooling the obtained emulsion, 0.25 part of aqueous ammonia was added to obtain an emulsion resin emulsion having a two-layer structure. The component (a) of the present invention includes (a-1) 4-methacryloxy-2,2,6,6-tetramethylpiperidinyl methacrylate and (a-2) N-methyl-2,2,6, 6
-Tetramethylpiperidinyl methacrylate, (b)
As the component, (b-1) γ-methacryloxypropyltrimethoxysilane, and as the component (c),
(C-1) 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole,
Each was used.

[0036]

[Table 1]

(Evaluation Method for Weather Resistance) Using the emulsion obtained in the above synthesis example, a paint was prepared according to the composition shown in the following (Table 2).

[0038]

[Table 2]

The obtained paint was applied on a slate plate so as to have a dry film thickness of about 100 μm, and dried at 50 ° C. for 7 days to prepare a test piece. This test piece was subjected to an exposure test using a sunshine weather meter, and the state of the coating film after 3000 hours was measured for gloss retention (%) using a gloss meter, and the discoloration resistance ΔE was measured using a color difference meter. The evaluation was carried out.

(Water whitening resistance test) 10 parts of butyl cellosolve was added to 100 parts of the emulsion obtained in the above synthesis example to prepare a test solution, and this solution was dried on a glass plate to a dry film thickness of about 20 µm. And then dried at 80 ° C. for 10 minutes to prepare a test piece. This test piece was immersed in water at 20 ° C., and the degree of whitening of the coating film after 7 days was visually observed.
The evaluation results were displayed as follows. ◎: no change ：: slight whitening Δ: whitening was observed in the whole ×: completely whitened

The results of the above evaluation are shown in (Table 2).

[0042]

[Table 3]

[0043]

As described above, according to the present invention, in an exposure test using a sunshine weather meter, not only excellent gloss retention and discoloration resistance, but also excellent water whitening resistance and solvent resistance are exhibited. Thus, a resin emulsion for a paint is obtained which gives a coating film which is satisfactory in crack resistance and blister resistance. Also,
The paint using the resin emulsion of the present invention is also excellent in workability such as pigment dispersibility, paintability and stickiness.

Claims (5)

[Claims] 1. The resin content of a resin emulsion is 100% by weight.
(A) 0.1 to 10% by weight of a light-stable group-containing monomer unit and (b) 0.1 of an alkoxysilyl group-containing monomer unit.
A resin emulsion for coatings having excellent weather resistance containing from 10 to 10% by weight. 2. The resin emulsion for paints according to claim 1, further comprising (c) 0.1 to 10% by weight of a monomer unit having an ultraviolet absorbing group. 3. The photo-stable group-containing monomer has a chemical formula
The method according to claim 1, wherein the compound is represented by the following formula (1).
Resin emulsion for paints. Embedded image(In this equation, R₁Is H or CN, R_Two, R_ThreeIs each
H, CH_ThreeOr C_TwoH _FiveEven if they are the same or different
Well, R_FourIs H, an alkyl group having 1 to 18 carbon atoms or -C
OC (R_{2 '}) = CH (R_{3 '}) [R_{2 '}, R_{3 '}Is H,
CH_ThreeOr C_TwoH _FiveAnd may be the same or different
No. And X represents a nitrogen atom or an oxygen atom. ) 4. The alkoxysilyl group-containing monomer,
3. The composition according to claim 1, which is represented by a chemical formula (Formula 2).
The resin emulsion for paints according to 1. Embedded image (In this formula, R ₅ represents H or CH ₃ , R ₆ represents an alkyl group having 1 to 3 carbon atoms, and Y represents an alkylene group having 1 to 6 carbon atoms.) 5. The monomer having an ultraviolet absorbing group,
The resin emulsion for paint according to claim 2, which is represented by a chemical formula (Formula 3). Embedded image (In this formula, R ₇ is H or CH ₃ , Z is carbon number 1
To 6 alkylene groups. )