JPS60115606A - Lowly moisture-absorptive methacrylate resin - Google Patents

Abstract

PURPOSE:To methacrylate resin of a decreased moisture absorptivity, prepared by copolymerizing methyl methacrylate with dicyclopentenyl methacrylate. CONSTITUTION:A lowly moisture-absorptive methacrylate resin prepared by copolymerizing 90-40pts.wt. methyl methacrylate with 10-60pts.wt. dicyclopentenyl methacrylate. By the copolymerization of monomer B, the moisture absorptivity of the copolymer can be decreased without detriment to the excellent inherent properties of a methacrylate resin, such as tranaparency, weather resistance, mechanical properties, thermal properties, and moldability. Therefore, the dimensional change and warpage of an article upon absorption of moisture are remarkably improved, so that this resin can be suitably used in the form of a sheet or as a molding material in a variety of optical devices and instruments, for example, disk bases for information recording media such as video disks and information disks for computers, plastic lenses, prisms, optical fibers, etc.

Description

[Detailed description of the invention] (The invention relates to a low hygroscopic methacrylic resin.

Methacrylic resins containing methyl methacrylate as a main component not only have excellent transparency and weather resistance, especially 1, but also have excellent mechanical properties and thermal cellulose properties. It has well-balanced properties such as moldability, and by taking advantage of these characteristics, it can be used as a sheet material or as a molding material, such as signboards, lighting equipment parts, auto parts, miscellaneous goods, etc. It is used in many ways.

As the field of application expands, the required performance of the raw material resin also increases, and there are some fields where improvements are desired.

One of these is the problem of hygroscopicity, and methacrylic resin has relatively high hygroscopicity compared to polyolefin resins or polystyrene resins. In some fields, the use of some products is restricted due to the occurrence of cracks and cracks due to long-term repeated cycles.

This problem of hygroscopicity of methacrylic resins is, to some extent, an inherent property caused by the chemical structure of the polymer, and so far there have not been many proposals on how to modify it, and of course no commercialization has been carried out. is the current situation.

The present inventors have overcome the above-mentioned drawbacks and achieved an excellent optical I.
In order to develop a methacrylic resin with high quality, as a result of detailed examination and 1.I on methacrylic resins made by copolymerizing methyl methacrylate with various middle body components, we found that by copolymerizing dicyclopentenyl methacrylate with methyl methacrylate, We discovered a completely new effect of reducing the hygroscopicity of methyl methacrylate.
They also discovered that this J(I'r+' combination has the excellent properties inherent to methacrylic resin, such as transparency, weather resistance, mechanical properties, thermal properties, and moldability, and thus arrived at the present invention. .

That is, the present invention is a low hygroscopic methacrylic resin obtained by copolymerizing 40 to 90% by weight of methyl methacrylate (A) and 10 to 60% by weight of dicyclopentenyl methacrylate (B).

In the present invention, the proportion of methyl methacrylate (A) used is 40 to 90% by weight in order to impart optical properties, weather resistance, mechanical properties, thermal properties, or moldability inherent to methacrylic resin to the resulting copolymer. The composition range is preferably 50 to 85,000 to 111%. If it is less than 40% by weight, the inherent properties of the methacrylic resin will be impaired, and if it exceeds 90% by weight, the effect of reducing hygroscopicity will be small.

The amount of synchropentenyl methacrylate (B) used is 10 to 60%, but in this year it is necessary to improve the hygroscopicity of the copolymer, and preferably 20 to 50%. 'rid%. l
If it is less than O weight μ%, the effect of reducing hygroscopicity is small;
If it exceeds 60% by weight, the mechanical properties of the copolymer will deteriorate, which is not preferable.

The reason why this copolymer into which dicyclopentenyl methacrylate is introduced greatly reduces the hygroscopicity of the methacrylic resin is thought to be due to the hydrophobicity of the dicyclopentenyl group in the structure of synclopentenyl methacrylate.

Further, if necessary, another W-in-vinyl form (C) copolymerizable with (A) and (B) can be copolymerized in an amount of up to 20 parts by weight.

Specific examples of the vinyl monomer (C) to be copolymerized include methyl acrylate, ethyl (meth)acrylate,
Examples include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, alkyl acrylate or alkyl methacrylate having a secondary linear or branched alkyl group having 1 to 8 carbon atoms, cyclohexyl (meth)acrylate, styrene, acrylonitrile, etc. I can do it.

The amount of vinyl monomer (C) to be used is 0 to 20 parts by weight, but especially considering the heat decomposition resistance and heat distortion temperature of the copolymer, it is preferable to use 1 to 15 parts by weight. In addition, in consideration of hygroscopicity, butyl acrylate, 2-ethylhexyl acrylate, styrene, cyclohexyl acrylate, etc. are preferably used as the vinyl monomer (C).If necessary, this copolymer may be oxidized. A 1F inhibitor, ultraviolet absorber, mold release agent, etc. may be added.

As the polymerization method for obtaining the methacrylic resin of the present invention, conventionally known polymerization methods 1 for methacrylic resins, such as suspension polymerization method, emulsion polymerization method, bulk polymerization method, solution polymerization method, etc., can be applied. A methacrylic resin with controlled molecular weight can be obtained by improving moldability.

For example, in the Kake & 1,000 method, a monomer mixture containing a radical polymerization initiator and a chain transfer agent for controlling the molecular weight is dispersed in water in which a suspension dispersant is dissolved.
The polymerization may be carried out over several directions in a temperature range of 0°C. Bulk polymerization by casting method J: In J:, a radical polymerization initiator is added to a monomer mixture blended in a predetermined ratio, and then poured into a reinforced glass or stainless steel cell equipped with a vinyl chloride frame. Polymerization may be carried out at a temperature range of 130° C. for several hours.

Examples of the radical polymerization initiator used in the present invention include diacyl peroxide, peroxy ester, dialkyl peroxide, ketone peroxide, and azobis-based compounds, and as a chain transfer agent for controlling the degree of polymerization. For example, aromatic mercaptans such as alkyl mercaptans, thioglycolic acid and its esters, β-mercaptopropionic acid and its esters, thiophenol, and thiofretool are used.

The low hygroscopic methacrylic resin of the present invention has excellent optical properties and is significantly improved in dimensional changes due to moisture absorption and product warpage compared to conventional methacrylic resins, so it can be used in various applications as a sheet or molding material. It can be suitably used for optical equipment such as substrates for information recording media such as audio discs, video discs, and information discs for computers, plastic lenses, prisms, optical fibers, and the like. In particular, the copolymer of the present invention is suitable for use in optical disk substrates in which information is embedded at high density, since it is essential to suppress dimensional changes in the substrate as much as possible.

The present invention will be explained in more detail below based on Examples.

Example 1 2,250 g of ion exchange water was placed in a 5-liter separable flask equipped with a stirrer and a reflux condenser, and 0.3 g of a copolymer of sodium salts of methyl methacrylate and 2-sulfoethyl methacrylate was added as a dispersant. Sodium sulfate7.
5g was dissolved. On the other hand, methyl methacrylate) 825
g, 600 g of dicyclopentenyl methacrylate, and 75 g of butyl acrylate, 1.5 g of azobisisobutyronitrile as a polymerization initiator, and 3.0 g of n-year-old ctyl mercaptan as a chain transfer agent.
g, dissolved and put into a separable flask, replaced with nitrogen, and stirred at 35 Qrpm for 800 min.
The mixture was allowed to masticate at 88°C for 2 hours and then at 88°C for 2 hours. The obtained bead-shaped polymer was washed with water, filtered, and incubated at 75°C for 24 hours.
After drying for an hour, it was extruded into pellets using a pen) 49t 30+uw extruder. The obtained pellets were heated to a cylinder temperature of 230°C and an injection pressure of 00 kg/c rn'.
, the thickness obtained by injection molding at a mold temperature of 60°C 2II
11. The water absorption rate of an injection molded plate having a length and width of 110 mm at 50° C. and 90% relative humidity was measured according to ASTM D-570. In addition, bending strength, total light transmittance, haze value, heat distortion temperature, etc. were measured. The measurement method and measurement results are shown in Table 2.

Comparative Examples 1 to 3 Polymerization was carried out in the same manner as in Example 1, except that the composition of the monomer mixture in Example 1 was changed as shown in Table 2, and the obtained polymer was injection molded. The water absorption rate and other properties of the molded plate were measured, and the results are shown in Table 1 together with those of Example 1.

As is clear from the results in Table 1, it can be seen that the molded plates of the examples of the present invention have a satisfactory balance in each piece property such as optical properties, mechanical properties, thermal properties, and water absorption rate. .

Table 1: Equilibrium water absorption rate + at 50°C and 190$ relative humidity
2: Thickness 2II11, size 110mm x 110an
One side of the injection molded plate was coated with aluminum ZN, immersed in water at 23°C for 24 hours, and warpage at the center was measured.

Table 2 Example 2 Methyl methacrylate-1-9 was prepared in exactly the same manner as in Example 1.
30g, dicyclopentenyl methacrylate 525g,
45 g of the monomer mixture (2-ethylhexyl acrylate) was polymerized, and the physical properties of the obtained polymer were measured. The results are shown in Table 3.

Example 3 Methyl methacrylate 95 was prepared in exactly the same manner as in Example 1.
A monomer mixture of 0 g, dicyclopentenyl methacrylate 525 g, and styrene 75 g was polymerized, and the physical properties of the obtained polymer were measured. The results are shown in Table 3.

Table 3*3. &4: Molded by the same method as in Table 1. 5: Molded using Acrypella (manufactured by Mitsubishi Rayon Co., Ltd.) MD.

Claims (1)

[Claims] 1. Methyl methacrylate (A) 40-90 weight jl:%
, dicyclopentenyl methacrylate (B) 10-(3
Low hygroscopic methacrylic resin made by copolymerizing Q% and 1i1%