JPH051163A - Surface treatment of transparent acrylic rubber molded product - Google Patents

Abstract

PURPOSE:To provide the subject surface treatment method capable of sustaining the transparency of the molded products without developing no blooming despite use of a hindered amine-based light stabilizer therein. CONSTITUTION:(A) The surface of a crosslinked molded product of an ethyl acrylate-dicyclopentenyl acrylate copolymer is coated with (B) a liquid composition comprising (1) ethyl diethylene glycol acrylate, (2) tetraethylene glycol diacrylate, (3) a methacrylic group-contg. hindered amine and (4) an organic peroxide, followed by heating at 110 deg.C in a nitrogen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a transparent acrylic rubber molded article. More specifically, the present invention relates to a surface treatment method for a transparent acrylic rubber molded article for improving light resistance.

[0002]

2. Description of the Related Art It is known that organic polymer materials such as rubber and plastic are photo-deteriorated with time when used outdoors. Therefore, it is generally practiced to add various light stabilizers. It is known that a hindered amine-based light stabilizer has an excellent effect as a light stabilizer, but bloom (leaching to the surface) occurs when it is used for a long time.

In a rubber molded product colored in black or brown, light does not reach the inside of the molded product, and this bloom has an advantage that the light stabilizing effect is effectively exhibited on the surface of the molded product. Seen. However, in the case of transparent rubber or plastic, when bloom occurs, the surface of the molded product becomes cloudy and the light transmittance decreases.
It is also a hygiene problem.

Therefore, the following method has been taken as a measure for preventing the occurrence of bloom, but the problem has not been solved yet. (1) Method of adding hindered amine with high molecular weight In this method, although the generation rate of bloom is decreased,
It is not possible to eliminate the generation of bloom itself (see Comparative Example 2 below). (2) Method of reacting with a polymer using a reactive hindered amine. In this method, bloom generation can be prevented, but other light stabilizers are used. In order to obtain the same effect as in (1), a larger amount of reactive hindered amine must be used, and this reactive hindered amine itself is slightly colored yellow, so transparent rubber moldings also have a slightly yellow color. It is colored, and as a result, the light transmittance is lowered from the beginning (see Comparative Examples 3 to 4 below).

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to use a hindered amine-based light stabilizer while using a surface treatment capable of maintaining the transparency of a transparent acrylic rubber molded article over time without causing blooming. To provide a method.

[0006]

The object of the present invention is as follows.
On the surface of a transparent acrylic rubber molded article, (a) one acrylic group-containing compound whose glass transition temperature (Tg) of its homopolymer is 0 ° C. or less, (b) two or more acrylic group-containing compounds , (C) General formula (Wherein R is a hydrogen atom or a methyl group) A methacrylic group-containing hindered amine represented by (d) and (d) a liquid composition composed of an organic peroxide, and then heated in an inert atmosphere. Achieved by the method.

As a transparent acrylic rubber molded article to be surface-treated, alkyl acrylate and the general formula CH ₂ = CR ₁ COOR ₂
Or CH ₂ ═CR ₁ COO (CH ₂ ) nOR ₂ (R ₁ : H, CH ₃ , R ₂ : dicyclopentenyl group, n: 1 to 2) copolymer or fluorine-containing acrylic polymer material, for example IH, 1H-trifluoroethyl (meth) acrylate, 1H, 1H, 3H- trifluoropropyl (meth) acrylate, 1H, 1H, 5H- side chain, such as octafluoropentyl (meth) acrylate -COO (CH ₂₎ n (CF
₂ ) Homopolymer of (meth) acrylate having mX [X: H, F, n: 1 to 2, m: 1 to 8] or about 1 to 30 mol% of ethyl acrylate, butyl acrylate, 2-hydroxyethyl
(Meth) acrylate, alkoxyalkyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyl oxyethyl (meth) acrylate copolymer, etc., high light transmittance in the visible light region A vulcanization molding of the acrylic elastomer is used.

These transparent acrylic rubber molded products are as follows:
The surface is treated with a liquid composition comprising components (a) to (d).

As one acrylic group-containing compound of the component (a), for example, an alkyl acrylate having an alkyl group of C _{1 to} C ₁₂ , an alkyl methacrylate having an alkyl group of C _{4 to} C ₁₂ , butoxyethyl acrylate, ethoxydiethylene glycol. Acrylate (ethyldiethylene glycol acrylate), butoxytriethylene glycol acrylate (butyltriethylene glycol acrylate), long-chain aliphatic (meth) acrylate, etc., whose glass transition temperature (Tg) of its homopolymer is 0 ° C or less is used. Be done.

The Tg of the homopolymer of the component (a) compound is limited to 0 ° C. or lower because this component is contained in most of the liquid composition (about 8 ° C.).
0 to 96% by weight, preferably about 80 to 90% by weight), when this is crosslinked, when Tg is high, only the surface layer becomes hard, and when stress is applied due to the difference in elastic modulus from the transparent acrylic rubber matrix. This is to prevent such a situation because cracks are likely to occur.

Examples of the component (b) containing two or more acrylic groups include compounds represented by the general formula CH ₂ = CR ₁ COO (CH ₂ CHR ₂ O) nCO
CR ₁ = CH ₂ (R ₁ , R ₂ : H, CH ₃ , n: 1 to 8)
(Meth) acrylate, general formula CH ₂ = CR ₁ COO (CH ₂ ) mOCOCR ₁
= CH ₂ (R ₁ : H, CH ₃ , m: 4 to 8) represented by di (meth) acrylate, dicyclopentenyl (meth) acrylate and the like are used.

These component (b) compounds are used to effectively three-dimensionally reticulate a liquid composition. For this purpose, it is used in the liquid composition in a proportion of about 3 to 20% by weight, preferably about 5 to 18% by weight. If it is used below this range, crosslinking will be insufficient and the tackiness will increase. On the other hand, if it is used above this range, the crosslinked layer will become harder and the elasticity as rubber will be lost.

The methacrylic group-containing hindered amine represented by the general formula (c) is about 0.5 to 1 in the liquid composition.
It is used in a proportion of 0% by weight, preferably about 2-5% by weight.
When it is used in an amount less than this, the effect of improving the light resistance is not substantially seen, while when it is used in an amount higher than this, the transparency decreases.

As the organic peroxide which is the component (d), the generally used one is about 0.1 to 2% by weight in the liquid composition.
%, Preferably about 0.1 to 1% by weight.

The liquid composition is prepared by mixing each of these components, and the liquid composition is applied to the entire surface of the transparent acrylic rubber molded article or the light-irradiated surface by a dipping method, a spraying method, or the like, with a coating thickness of about 5 to 500 μm. Preferably, the surface treatment is performed by coating so as to be about 10 to 100 μm, and heating at about 90 to 130 ° C. for about 5 to 60 minutes in an inert gas atmosphere, in an inert atmosphere such as vacuum. ..

[0016]

In the method of the present invention, the above-mentioned characteristic that the reactive hindered amine does not generate bloom and the characteristic that the hindered amine bloomed on the surface effectively exhibits the light stabilizing effect are effectively used. is doing.

That is, when a reactive hindered amine-containing liquid composition is applied to the surface of a transparent acrylic rubber molded article and heat-crosslinked, the hindered amine is taken into the acrylic polymer molecule, so that it is simply bloomed. Unlike, it maintains photostability for a long time and at the same time solves hygiene problems. Also, since the hindered amine concentration on the surface of the molded product is high, it is effectively stabilized on the surface of the molded product with respect to irradiated light, especially ultraviolet rays, so that the irradiation light may adversely affect the inside of the molded product. There is no such thing.

[0018]

Industrial Applicability According to the method of the present invention, a transparent acrylic rubber molded article is provided which is capable of maintaining transparency over time without using bloom while using a hindered amine light stabilizer.

[0019]

EXAMPLES The present invention will now be described with reference to examples.

Example 1 Ethyl acrylate-dicyclopentenyl acrylate
(Molar ratio 94: 6) 100 parts by weight of a copolymer (number average molecular weight 1.2 × 10 ⁵ ), 10 parts by weight of tetraethylene glycol diacrylate and 1 part by weight of an organic peroxide (Nippon Oil & Fat Products Perhexa 3M) The acrylic rubber composition was thermally crosslinked at 120 ° C. for 30 minutes to obtain a 50 × 50 × 10 mm square plate-shaped body.

On one side of this transparent square plate, ethyl diethylene glycol acrylate C ₂ H ₅ O (CH ₂ CH ₂ O) ₂ C
OCH = CH ₂ 90% by weight, tetraethylene glycol diacrylate 5% by weight, methacrylic group-containing hindered amine
(Asahi Denka LA-82, 4% by weight of R = CH ₃ in the above general formula) and 1% by weight of organic peroxide (Perhexa 3M) are applied by a casting method to a coating thickness of 30 μm. And heated in a nitrogen gas atmosphere at 110 ° C. for 60 minutes.

Example 2 In Example 1, a long-chain aliphatic acrylate (Sartomer product C-9013) was used in place of ethyldiethylene glycol acrylate, and another compound was used as a methacrylic group-containing hindered amine (Asahi Denka LA-87, In the above general formula, R
= H) were used in equal proportions.

Example 3 In Example 1, 2-ethylhexyl acrylate was used instead of ethyldiethylene glycol acrylate, and dicyclopentenyl acrylate was used instead of tetraethylene glycol in the same proportions.

Comparative Example 1 Hindered amine was added to the transparent rubber composition of Example 1.
(Asahi Denka LA-62) was added in an amount of 1 part by weight and heat-crosslinked in the same manner to obtain a square plate-shaped body.

Comparative Example 2 Into the transparent acrylic rubber composition of Example 1, 1 part by weight of a high molecular weight hindered amine (LA-63 from Asahi Denka Co., Ltd.) was added. Got the body

Comparative Example 3 1 part by weight of methacrylic group-containing hindered amine (Asahi Denka LA-82) was added to the transparent acrylic rubber composition of Example 1, and heat-crosslinked in the same manner to form a square plate. Got the body

Comparative Example 4 In Comparative Example 3, the amount of methacrylic group-containing hindered amine was changed to 10 parts by weight.

With respect to the square plate-shaped bodies of the above respective Examples and Comparative Examples, a weather resistance test with a carbon arc lamp was carried out for 150 hours at a black panel temperature of 63 ° C. using a sunshine weather meter (manufactured by Suga Test Machine). The light transmittance (wavelength 400 nm) was measured and the presence or absence of bloom was visually observed. The results obtained are shown in the following table.

[0029]

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Claims (1)

Claims: 1. The surface of the transparent acrylic rubber molded article is provided with (a)
A homopolymer having a glass transition temperature (Tg) of 0 ° C. or lower, one acrylic group-containing compound, (b) two or more acrylic group-containing compounds, (c) a general formula (Wherein R is a hydrogen atom or a methyl group), after applying a liquid composition consisting of a methacrylic group-containing hindered amine and (d) an organic peroxide, heating in an inert atmosphere. A method for surface treatment of a characteristic transparent acrylic rubber molded product.