JPS585318A - Lowly hygroscopic methacrylic resin - Google Patents

Abstract

PURPOSE:A methacrylic resin having hygroscopicity which is decreased without detriment to its inherent characteristics and being suitable for use in optical devices and instruments, audio disc, or the like, prepared by copolymerizing a methacrylate with a specified proportion of cyclohexyl methacrylate. CONSTITUTION:A copolymer consisting of 50-85wt% methyl methacrylate, 15-50wt% cyclohexyl methacrylate and 0-10wt% vinyl monomer copolymerizable with said methacrylates [e.g., alkyl (meth)acrylate or styrene]. In case of casting, the above monomers are mixed and formed into a partial polymerizate, which is then poured in a cell and bulk-polymerized therein. In case where a molding material is desired, the above monomers are suspension- or emulsion- polymerized. USE:Production of video disc or computer information disc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to low hygroscopic methacrylic resins.Methacrylic resins containing O-methyl methacrylate as a main component not only have extremely excellent properties in transparency and weather resistance, but also have excellent mechanical properties. It has well-balanced properties such as physical properties, thermal properties, and moldability, and by taking advantage of these characteristics, it can be used as a sheet material or molding material for signboards, lighting equipment parts, electrical equipment parts, automobile parts, etc. It is used in many ways, including miscellaneous goods.

On the other hand, as the range of applications expands, the performance requirements for raw material resins also increase, and there are some fields in which improvements are desired.

One of these is the problem of hygroscopicity, and methacrylic resin has relatively high hygroscopicity compared to polyolefin resins or polystyrene thread resins, resulting in dimensional changes due to humidity, warping of molded products, or long-term repeated wet and dry conditions. In some fields, the use of certain products is restricted due to cracks occurring due to cycles.

The problem of hygroscopicity of methacrylic resin is, to some extent, an inherent property caused by the chemical structure of the polymer.
Until now, there have been very few proposals on how to modify it, and of course it has not been commercialized. O Cyclohexyl methacrylate has a higher refractive index as a homopolymer than other methacrylate polymers. It also has excellent light dispersion properties, and has long been known to have excellent basic performance as a material for plastic lenses. The present inventors have overcome the above-mentioned drawbacks and developed a methacrylic resin with excellent optical properties. In order to achieve this goal, we conducted a detailed study on various copolymers of cyclohexyl methacrylate, and as a result, we found that it was copolymerized with methyl methacrylate!
/1 We have discovered a completely new effect of reducing the hygroscopicity of methyl methacrylate polymers, which is completely different from the optical properties known in the past. The present invention was achieved based on the discovery that methacrylic resins have excellent properties such as weather resistance, mechanical properties, thermal properties, and moldability. )(4)! ON
g&wt%, cyclohexylmethacrylate)CB)lt
Low moisture absorption methacrylic resin of the present invention, which is a low moisture absorption methacrylic resin obtained by copolymerizing 0 to 70% by weight of other vinyl monomers (C) copolymerizable with ~go weight rumors and (4) and ■) Methacrylic resin has excellent optical properties, and dimensional changes due to moisture absorption and warping of the product are significantly improved compared to conventional methacrylic resins.It can be used as a sheet or molding material for a large number of optical devices. For example, it can be suitably used as a substrate for information recording media such as audio discs, video discs, information discs for computers, etc., as well as plastic lenses, prisms, etc. In the present invention, the usage ratio of methyl methacrylate (CA) j0~g! Weight % I is the composition range necessary to impart optical properties, weather resistance, mechanical properties, thermal properties, or moldability to a methacrylic resin to the resulting copolymer, and more preferably S! ~go weight attack. If the amount of jO is less than 85% by weight, the above characteristics will be impaired;
This is because if it exceeds 20%, the effect of improving hygroscopicity will be reduced.

In the present invention, the amount of cyclohexyl methacrylate (6) used is 13NjO weight %Gt, which is the amount of the component necessary to improve the hygroscopicity of the resulting copolymer, and is more preferably 10 to II! If the weight is less than 13% by weight, the hygroscopic property modification effect is not sufficient, and if it exceeds 30% by weight, the mechanical properties of the copolymer will be thick (decreased, and at the same time, during molding). This is because chips, cracks, etc. may occur, resulting in problems during molding.

Other vinyl monomers (C
) include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 1-styrene, acrylonitrile, etc., and the usage ratio is θ~1
The range of 0 weight attack is good.

In particular, when the copolymer of the present invention is put to practical use as a molding material, molding in a relatively high temperature range should be considered, and in order to improve the thermal decomposition resistance of the copolymer, it is possible to copolymerize with (4) and 03). dj~1 with another vinyl compound (C) as the third component
It is preferable to use 0 weight it%.

If it is less than the weight of aS, the heat decomposition resistance is insufficient, and if it exceeds 10% by weight, there are problems such as decreased transparency or increased hygroscopicity. Particularly preferred as the third component. From the viewpoint of heat decomposition resistance and hygroscopicity, examples include butyl acrylate, coethylhexyl acrylate, styrene, etc. Polymerization methods for obtaining the methacrylic resin of the present invention include bulk polymerization, solution polymerization, suspension polymerization, Any polymerization method such as emulsion polymerization can be used, but if the material is to be obtained as a sheet material, the bulk polymerization method using the casting method is used, but if the purpose is to obtain a molding material, suspension polymerization or The emulsion polymerization method is preferable. In carrying out the process specifically, it is sufficient to use a very commonly used treatment. First, a partially polymerized product was prepared from the polymer mixture, and this was poured into a glass or stainless steel cell set with a soft vinyl chloride frame.
Polymerization may be carried out at a temperature of ~/JOC for several hours.

When a suspension polymerization method or an emulsion polymerization method is adopted, a monomer mixture to which a radical polymerization initiator and a chain transfer agent for controlling molecular weight are added is dispersed in water in which a suspension dispersant or emulsifier is dissolved. The methacrylic resin of the present invention may be mixed with other polymers as needed, and may be polymerized for several hours at a temperature range of 30 to tsoc. Additives such as colorants and mold release agents may be added.

The specific content of the present invention will be explained below with reference to Examples.

Example l Pure water/! in 31 separable 7 lasks equipped with stirrer and condenser! 1009 was added, and gelvinyl alcohol/liter was dissolved in pure water as a dispersant. Separately, methyl methacrylate rroti, Shitahexyl methacrylate 4I00g, butyl acrylate! Mix each monomer of θ7 and add n-octyl mercaptan to this.
jg and azobisisobutyronitrile/9 were added and dissolved with stirring, and this mixture was poured into a seven-parapul 7 flask containing pure water in which the previously prepared dispersant had been dissolved, heated to goc, and j! Polymerization was carried out while stirring at r Orpm, and the peak time gI! ? Polymerization was carried out in IC for □3 hours.

The obtained polymer was separated by f, washed with water, and 'l! The mixture was dried and shaped at c for 1 hour and pelletized. This pellet was injection molded at a cylinder temperature of 230C% and a mold temperature of 1cm.
An injection molded plate of 1 size / / Om As a result of measurements such as transmittance 1 haze value, etc., when the warpage was measured when crushed, almost no warpage was observed.In contrast, conventional methacrylic resin (shown in the comparative example section) had a similar measurement of lj■. there were.

Comparative Examples 1 to 3 Polymerization was carried out in the same manner as in Example 1 except that the monomer composition in Example I was changed as shown in Table 1, and the obtained polymer was injection molded, and a molded plate was formed. Water absorption, bending strength, total light transmittance, haze value HDT, etc. were measured, and the results are shown in Table 1 along with those of Example 1. As is clear from the results of Table 1, the results of Examples of the present invention It can be seen that the molded plate has a satisfactory balance of physical properties such as optical properties, mechanical properties - thermal properties 1@humidity.

Table 1-Example 2 A monomer mixture of methyl methacrylate Mengko Og, Schifte hexyl methacrylate J! The water absorption, bending strength, total light transmittance, haze value, HDT, and FR hygroscopic strain were measured. The results are shown in Table 3. Example 3 Methyl methacrylate 40 was prepared in exactly the same manner as in Example 1.
09, cyclohexyl methacrylate 3jOg, styrene! A monomer mixture of Qg is polymerized, and the resulting polymer has water absorption, bending strength, 1 total light transmittance, 1 So value, and HDT%F.
R@wet strain was measured. The results are shown in Table 3.Example A monomer mixture of methyl methacrylate 4jO9 and citalohexyl methacrylate szo9 was placed in a 31 separable flask equipped with a stirrer and a condenser, and azobisbaretanitrile was added as an initiator. Add and dissolve 6g of a and polymerize with TOOC for 5 minutes to obtain a partially polymerized product.0 This partially polymerized product! 00g contains ultraviolet absorber Tinuvin P (manufactured by Ciba Geigy) QO! r9, as an initiator, azobismoretetranitrile at9 was added and mixed and dissolved, then injected into a glass cell and polymerized for 1 hour at ≦IC.The water rate was i/%1 relative humidity 10
The dimensional change rate at 0% is 0/! The light transmittance, haze value, bending strength, and HDT of the bare metal were measured and the results shown in Table 1 were obtained.

Table D Example 3 Equipped with a stirrer and condenser! lPour 30009 pure water into a separable flask, add emulsifier Sarcosine) t, N (-4j, s, manufactured by Hikari Chemicals Co., Ltd.) io
n, iron sulfate, IO1ν"ψ', engineering f, t, acetin tetraacetate sodium salt (104) was added and dissolved in pure water, and then 6 g of the reducing agent Rongalit was dissolved. Separately, methyl methacrylate was added. A monomer mixture of 00g of sea star, Schiffyo hexyl methacrylate s*o9, and 10g of butyl arylate with t-butylhydroperoxide @!
Add r'Q, n-octyl mercaptan 39, mix and dissolve, and put into the separable flask prepared earlier.
Polymerization was carried out for 4 hours at kCs at 300 rpm. This latex was coagulated using sulfuric acid as a coagulant, washed, and dried to obtain a polymer. This polymer was shaped and molded to determine water absorption, total light transmittance, haze value, bending strength, and HDT.・
The PR was measured and the results shown in Table 3 were obtained.

Table S

Claims (1)

[Claims] l Methyl methacrylate (4) 30 to 53% by weight, cyclohexyl methacrylate (8) 13 to SO and other vinyl monomers copolymerizable with (A) and (8) (C) A low hygroscopic methacrylic resin copolymerized with 0-/0% by weight.
Low hygroscopic methacrylic resin 03 according to claim 1, which is an alkyl acrylate or alkyl methacrylate having an alkyl group having a straight chain or branched S. The unsaturated vinyl compound (C) to be copolymerized is styrene. Low hygroscopic methacrylic resin according to claim 1