JPH0532731A - Transparent resin having low water-absorption - Google Patents

Abstract

PURPOSE:To obtain the subject resin having excellent mechanical strength and refractive index and useful for optical card, lens, etc., by casting and polymerizing phenyl methacrylate, dicyclopentenyl acrylate, an alkyl acrylate and a crosslinking agent at specific ratios. CONSTITUTION:The objective resin can be produced by adding 1-20 pts.wt. of a polyfunctional (meth)acrylate having >=2 vinyl groups [e.g. ethylene glycol di(meth)acrylate] as a crosslinking agent to 100 pts.wt. of a monomer mixture composed of (A) 25-75wt.% of phenyl methacrylate, (B) 10-65wt.% of dicyclopentenyl acrylate and (C) 5-25wt.% of an alkyl acrylate having 1-5C alkyl group (e.g. methyl acrylate) and casting and polymerizing the obtained composition in the presence of a radical polymerization initiator (e.g. benzoyl peroxide) at 50-150 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic resin having low water absorption and excellent mechanical strength and flexibility.

[0002]

2. Description of the Related Art Conventionally, as transparent resins for optical information recording bodies, polymethylmethacrylate, polycarbonate,
Polystyrene and the like are known. Among them, polymethylmethacrylate has a well-balanced optical property and mechanical strength and is widely used in various fields, but it has a drawback that it has a higher water absorption rate than polycarbonate or polystyrene. . The degree of water absorption depends on the shape of the molded product, but if the water absorption rate exceeds 1.5%, the molded product may undergo dimensional changes, warpage, or become cloudy. Also, cracks may occur when water absorption and drying are repeated due to environmental changes.

On the other hand, polystyrene has a very low water absorption, but has a drawback that its birefringence is large and its transparency tends to change with time. Further, although polycarbonate has a very low water absorption, it has a large birefringence and is slightly inferior in transparency.

Various proposals have been made for reducing the water absorption of an acrylic resin containing methyl methacrylate as a main component.
For example, JP-A-58-5354 discloses a copolymer of methyl methacrylate and cyclohexyl methacrylate, JP-A-60-115609 discloses a copolymer of methyl methacrylate and dicyclopentenyl methacrylate, and JP-A-61-1141716 discloses. Copolymers of methyl methacrylate with phenyl methacrylate, benzyl methacrylate, isobornyl methacrylate, etc. have been reported.

[0005]

However, although these copolymers can obtain a transparent resin having low water absorption, they have the drawback that they have no mechanical flexibility such that they are not bendable against forced bending stress and they are easily cracked. .

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a transparent resin having not only low water absorption but also excellent mechanical strength.

That is, the present invention relates to phenyl methacrylate 2
5 to 75% by weight, dicyclopentenyl acrylate 10
To 65% by weight and 100% by weight of a monomer mixture consisting of 5 to 25% by weight of an alkyl acrylate having an alkyl group having 1 to 5 carbon atoms, at least 2 as a crosslinking agent.
1-functional poly (meth) acrylate having vinyl groups
It is a low water-absorbing transparent resin obtained by cast polymerization of a composition added with 20 parts by weight in the presence of a radical polymerization initiator.

In the resin of the present invention, the composition ratio of the monomer mixture for satisfying excellent low water absorption and mechanical properties is 25 to 75% by weight of phenyl methacrylate, preferably 30 to 65% by weight, The pentenyl acrylate is 10 to 65% by weight, preferably 15 to 55% by weight. If the proportion of dicyclopentenyl acrylate is less than 10% by weight, it is not preferable in terms of transparency, and if it exceeds 65% by weight, it becomes difficult to maintain the mechanical strength.

Next, examples of the alkyl acrylate having an alkyl group having 1 to 5 carbon atoms include methyl acrylate, ethyl acrylate and butyl acrylate. The use ratio is 5 to 25% by weight, preferably 15
If it is less than 5% by weight, it is difficult to maintain mechanical properties such as flexibility, and if it exceeds 30% by weight, it is difficult to maintain mechanical strength.

Next, a polyfunctional (meth) having at least two unsaturated bonds used as the crosslinking agent of the present invention.
Specific examples of the acrylate include ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate. ) Acrylate, tetramethylolpropane tri (meth) acrylate and the like.

As the radical polymerization initiator used in the present invention, a radical polymerization initiator generally used for the polymerization of methyl methacrylate can be used. Specifically, as an organic peroxide-based initiator, lauroyl peroxide, benzoyl peroxide, t-butyl peroxypivalate, t-butyl peroxy neodecanoate, t-butyl peroxy-2-ethyl hexanoate, t-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and the like, and azobis initiators include 2,2'-azobisisobutyronitrile, 2,
2'-Dimethyl-azobisisobutyrate, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4 -Methoxy-2,4-dimethylvaleronitrile) and the like.

The polymerization conditions of the transparent resin of the present invention are not particularly limited, but the polymerization temperature is usually 50 to 150 ° C.
Therefore, it is possible to carry out the polymerization in multiple stages by changing the polymerization temperature.

In the case of production by cast polymerization, the mold used is not particularly limited, and for example, a mold composed of a plate-like body such as tempered glass, a chrome-plated plate, a stainless plate and a gasket made of soft vinyl chloride, An example is a mold composed of opposing surfaces of a pair of endless belts that travel in the same direction at the same speed, and gaskets that run at the same speed as both endless belts on both sides of the surfaces.

[0014]

The present invention will be described in more detail with reference to the following examples. The physical properties in the examples were evaluated as follows. Total Light Transmittance and Haze Value It was performed according to ASTM D1003. Tensile Strength It was performed according to ASTM D638. Bending strength was measured according to ASTM D790. Water absorption The test piece was dried at 80 ° C / 0.1 mmHg or less for 48 hours or more to measure the initial weight, and then the test piece was allowed to stand in water at 40 ° C for 30 days, and the weight was measured. The test formula of JIS-K7209 It was obtained from the A method (when it is obtained from the ratio of the original weight of the test piece and the increase in weight after absorbing water).

Example 1 50 parts by weight of phenyl methacrylate, 35 parts by weight of dicyclopentenyl acrylate and 15 parts by weight of butyl acrylate were mixed, and 10 parts by weight of ethylene glycol dimethacrylate were added thereto and stirred. Further, 0.02 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) and 0.01 parts by weight of 2,2'-azobisisobutyronitrile were added as a polymerization initiator, and a release agent was added. After 0.1 part by weight of sodium dioctylsulfosuccinate was added and dissolved, the mixture was degassed in vacuum to remove volatile components. Next, it is cast into a casting cell made of an inorganic reinforced glass plate with a size of 30 mm x 30 mm, a steel clip, and a polyvinyl chloride gasket, and it is put in a water bath at 60 ° C for 4 hours and then for 120 hours.
Polymerization was carried out in an air bath at ℃ for 2 hours to obtain a plate having a thickness of 3 mm.
The results are shown in Table 1.

Examples 2 to 11 Experiments were carried out in the same manner as in Example 1 except that the composition of the monomers used was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that 100 parts by weight of phenyl methacrylate was used as a monomer. The results are shown in Table 1.

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that 60 parts by weight of phenyl methacrylate, 40 parts by weight of butyl acrylate and 10 parts by weight of ethylene glycol dimethacrylate were used as the monomers. The results are shown in Table 1.

Comparative Examples 3 to 8 Experiments were carried out in the same manner as in Example 1 except that the composition of the monomers used was changed as shown in Table 1. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

INDUSTRIAL APPLICABILITY The resin of the present invention has low water absorption, excellent mechanical strength and flexibility, and is used for optical information recording media such as optical cards and optical disks, and optical parts such as lenses and prisms. It has a high industrial utility value.

Claims (1)

Claims: 1. 25 to 75% by weight of phenyl methacrylate, 10 to 65% by weight of dicyclopentenyl acrylate.
And 100 parts by weight of a monomer mixture consisting of 5 to 25% by weight of an alkyl acrylate having an alkyl group having 1 to 5 carbon atoms, a polyfunctional (meth) acrylate having 1 to 2 vinyl groups as a crosslinking agent. A low water-absorbing transparent resin obtained by cast polymerization of a composition containing 20 parts by weight in the presence of a radical polymerization initiator.