JPS6026014A - Lowly hygroscopic methacrylic resin - Google Patents

Abstract

PURPOSE:To obtain a methacrylic resin having decreased hygroscopicity and excellent transparency, heat resistance and mechanical properties, by copolymerizing a monomer mixture of methyl methacrylate and isobutyl methacrylate at a specified ratio. CONSTITUTION:A copolymer is formed by copolymerizing 40-80wt% (A) methyl methacrylate with 20-60wt% (B) isobutyl methacrylate and 0-10wt% (C) other vinyl monomers copolymerizable with monomers A and B. Examples of the monomer (C) include acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate and aromatic vinyl compounds such as styrene and p-methylstyrene. When the amount of the monomer (C) exceeds 10wt% the transparency and heat resistance of the formed polymer is lowered, or the hygroscopicity is increased, which is not desirable.

Description

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

Traditionally, methacrylic resins have excellent properties such as transparency, surface properties, weather resistance, and mechanical properties, so they are used as sheet materials and injection molded products such as signboards, lighting, automobiles, electrical parts, and optical products. It is used in many ways.

On the other hand, the performance requirements for raw material resins in various fields are also increasing, and there is a strong demand for low hygroscopicity to be imparted to methacrylic resins, especially in optical applications and information recording media.

That is, methacrylic resins have greater hygroscopicity than polystyrene resins or polyolefin resins, and are therefore prone to problems such as dimensional changes, warping, or cracks due to moisture absorption and desorption.

The hygroscopicity of methacrylic resins is due to the molecular structure of the polymer, and was considered to be an essential drawback. Up to now, there have been a few proposals for modifying the hygroscopic properties of methacrylic resins. Examples include a polymer of cyclohexyl methacrylate (JP-A-57-186241) and a copolymer of methyl methacrylate and cyclohexyl methacrylate (JP-A-58-5318). Polymers of cyclohexyl methacrylate have low hygroscopicity and excellent transparency, but they inherently have the drawback of being brittle and easily cracked, making them difficult to put into practical use.

Although the young polymer of isobutyl methacrylate used in the present invention has excellent transparency, it has low heat resistance, so it is generally used as a coating material for paper and fibers, and as an oil lubricant, and is used as a sheet material and molding material. is being applied. Homopolymers of n-butyl methacrylate other than isobutyl methacrylate have a low glass transition point (
20°C: Polymer HandbookK), difficult to use under normal conditions. Furthermore, a homopolymer of methacrylate and tert-butyl has low hygroscopicity, but has poor thermal stability and molecular cleavage of side chains occurs when heated, making it impractical.

The inventors of the present invention have conducted intensive studies to improve the hygroscopicity drawbacks of methacrylic resins, and as a result, we have found that in the copolymerization of methyl methacrylate and isobutyl methacrylate, we have developed We discovered new performance in reducing the hygroscopicity of methacrylic resins, which have completely different properties, and the copolymer in a specific range has excellent properties such as transparency, heat resistance, and mechanical properties. This is what led to the present invention.

The low hygroscopic methacrylic resin obtained by the present invention has very few defects such as dimensional changes and warpage due to moisture absorption compared to conventional methacrylic resins, and has the characteristics of transparency, weather resistance, and mechanical properties of methacrylic resin. Because it retains these properties, it can be suitably used in the field of optical materials such as lenses, video discs, audio discs, and information recording media for computers.

The ratio of methyl methacrylate (A) in the present invention is 40
~80% by weight, preferably 50-70% by weight, the proportion of isobutyl methacrylate is 20-60% by weight, preferably 30-50% by weight, and when the proportion of methyl methacrylate is below 30% by weight, The mechanical properties, heat resistance, molding processability, etc. of the produced copolymer deteriorate, and when it exceeds 80% by weight, the effect of improving hygroscopicity is impaired. When the proportion of isobutyl methacrylate is 70% by weight or more, the heat resistance and mechanical properties decrease. Also, if it is less than 20% by weight, it has low moisture absorption performance. i-No.

A vinyl monomer (C
) are acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, or styrene.
It is an aromatic vinyl compound such as p-methylstyrene or paramethylstyrene, and the proportion used is 0 to 101 tS, preferably 2 to 7% by weight. By using these third components, moldability and thermal stability can be improved without impairing low moisture absorption.

On the other hand, if 1o111%v or more is used, transparency and heat resistance decrease, and absorption (M) property increases, which is not preferable.

The polymerization method in the present invention is a conventionally known polymerization method for methacrylic resins, such as bulk polymerization, suspension polymerization,
Any method such as emulsion polymerization can be used. In other words, in the case of bulk polymerization by cast polymerization to obtain a sheet material, a polymerization initiator is added to the bulk polymer mixture of a predetermined side, and the polymerization is carried out in a glass or plastic frame set with a flexible vinyl chloride frame. It may be injected into a stainless steel cell and polymerized at a temperature of 50 to 130°C for several hours. In order to obtain a molding material using suspension polymerization or emulsion polymerization, a monomer mixture containing a radical polymerization initiator and a chain transfer agent for controlling molecular weight is added to water in which a suspension stabilizer or emulsifier is dissolved. Disperse at 50-130℃
It is enough to polymerize for a few hours.

As a polymerization initiator, organic peroxides used in general radical polymerization, such as lauroyl peroxide, benzoyl peroxide, tert-butyl peroxide, etc.
2-ethylhexanoate, di-tert-butyl peroxide, tert-butyl peroxybivalate, or an azo polymerization initiator, such as 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobis isobutylene), 1,1'-azobiscyclohexanecarbonitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, as well as water-soluble potassium persulfate and 6-hydrogen peroxide. It will be done.

Examples of chain transfer agents include alkyl mercaptans such as normal octyl mercaptan, normal dodecyl mercaptan, and tertiary dodecyl mercaptan, and aromatic mercaptans such as thiophenol and barathiocresol. 2
They may be used in combination of different types.

The methacrylic resin obtained in the present invention may be mixed with other polymers as necessary, and antioxidants,
Additives such as ultraviolet absorbers, mold release agents, and colorants can also be added.

EXAMPLES The present invention will be specifically explained below using Examples.

Example】.

Pour 3000F pure water into a 5t separable flask equipped with a stirrer and a cooling condenser, add 7.5t of potassium polymethacrylate aqueous solution as a dispersant, 16v1 of disodium hydrogen phosphate and 065v of monosodium hydrogenphosphate as buffering agents. Dissolved, separately methyl methacrylate 705 F, isobutyl methacrylate 750 F,
To each monomer mixture of methyl acrylate 45F, n-dodecyl mercaptan 31 and suderyl alcohol 1.5F
After adding and dissolving 7.5 r of lauroyl peroxide, this mixture was poured into the previously prepared separable flask containing pure water, and heated at 80°C, 300 r, p.
Polymerization was carried out with stirring at , m, and after the exothermic peak reached 95°C.
Polymerization was carried out after 2 hours. The obtained beads were separated from P and washed thoroughly with water repeatedly, then dried at 70° C. for 16 hours, and pelletized using an extruder.

The pellets were molded into a 200x60x3% mold with a cylinder temperature of 220°C and a total mold temperature of 1. : Injection molding was performed at 50°C to create a flat plate molded product for measurement.

The saturated moisture content of this molded article was measured in an environment of 40° C.-90 SRH and was found to be 0.63%. The total light transmittance, haze value, tensile strength, Bi/Cart softening point, etc. were also good. The measurement results are shown in Table 1.

Example 2 Methyl methacrylate 1005F was prepared in the same manner as in Example 1.
, isobutyl methacrylate 450F.

Polymerize a ridge-like mixture of methyl acrylate 45F,
The obtained beads were pelletized and molded in the same manner as in Example 1, and the moisture absorption rate, total light transmittance, haze value, tensile strength, and Bizucart pupil point were measured, and the results are shown in Table 1.

Example 3 Methyl methacrylate 705 t was prepared in the same manner as in Example 1.
, Isobutyl methacrylate'y50F, Styrene 452
2,2'-azobisisobutyronitrile 4.5F as a polymerization initiator.

As a chain transfer agent! 1-Octylmercaptan 21 was mixed and polymerized, and the resulting polymer was measured for moisture absorption, total light transmittance, haze value, tensile strength, and Beet softening point. The measurement results are shown in Table 1.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the monomer composition in Example 1 was changed as shown in Table 1, and the obtained polymer was pelletized in the same manner as in Example 1. , injection molding was performed, and the moisture absorption rate, total light transmittance, haze value, tensile strength, and Pickert softening point of the flat plate molded product were measured. The result is the first
As shown in the table, no improvement in hygroscopicity was observed.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1, except that the monomer composition in Example II/C was changed as shown in Table 1, and the obtained beads were pelletized in the same manner as in Example 1. , injection molding is performed, and the moisture absorption rate, total light transmittance, haze value,
As a result of measuring the tensile strength and Billicart softening point, the moisture absorption performance was good, but the strength and heat resistance were significantly lowered.

Comparative Example 3 Parapet G (Kyowa Gas Chemical Industry ■iA), a commercially available methacrylic molding material, was injection molded under the same molding conditions as in Example 1, and the molded product was evaluated for moisture absorption, total light transmittance, haze value, and tensile strength. Strength and Pickert softening point were measured. As the results are shown in Table 1, the moisture absorption rate is very high.

Example 4 A 44-cell mixture of 20 Of' methyl methacrylate, 2 (1 Or) of itbutyl methacrylate, and 1.0 Ov of lauroyl peroxide was injected into a glass cell set in a soft vinyl chloride frame with Alt. Polymerization was carried out at 60°C and after 2 hours of exothermic peak, polymerization was carried out at 120°C.Each test piece was cut out from the obtained sheet and measured for moisture absorption rate, total light M transmittance, haze value, tensile strength, Bi, V cart softening point. The results are shown in Table 1.

Comparative Example 4 Each test piece was cut from a commercially available methacrylic resin plate Paraglass K (manufactured by Kyowa Gas Chemical Industry ■) in the same manner as in Example 4, and the moisture absorption rate, total light transmittance, haze value, tensile strength, and Bizukart softening point were measured. It's i-. As the measurement results are shown in Table 1, the moisture absorption rate is quite high.

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Claims (1)

[Scope of Claims] 1) Methyl methacrylate (A) 40 to 80% by weight, isobutyl methacrylate (B) 20 to 60% by weight, and (A)
) and other vinyl monomers copolymerizable with (B) (C)0
Low hygroscopic methacrylic resin copolymerized with ~10% by weight. 2) Copolymerizable cavinyl*-11 body (C) has 1 carbon number
80. The low hygroscopic methacrylic resin according to claim 1, which is an acrylic ester or methacrylic ester having a linear or branched alkyl group. 3) The low hygroscopic methacrylic resin according to claim 1, wherein the copolymerizable vinyl monomer (C) is styrene or methylstyrene.