JPH0794586B2 - Methacrylic resin composition with improved thermal decomposition resistance - Google Patents

Description

TECHNICAL FIELD The present invention relates to a methacrylic resin composition having improved thermal decomposition resistance, and more specifically, it has excellent optical properties, weather resistance, and excellent inherent properties of methacrylic resin. Without sacrificing well-balanced mechanical and thermal properties
Its thermal decomposition resistance has been significantly improved, and
The present invention relates to a methacrylic resin composition that can be preferably used for molded products having a complicated shape such as electronic devices and office equipment, and large-sized, thick molded products.

(Prior Art) Conventionally, methacrylic resins have excellent weather resistance and optical properties, and also have relatively well-balanced performance in mechanical properties and thermal properties. It is put to practical use in many fields such as electrical and electronic equipment and office equipment.

However, in general, methacrylic resin is close to the moldable temperature range and the thermal decomposition temperature, so it has poor thermal stability during molding processing, and when extruded or injection-molded, it depolymerizes from the molecular chain end, resulting in The amount of residual monomer tends to increase.
The monomer produced by this depolymerization not only significantly deteriorates the thermal and mechanical properties of the molded product due to the plasticizing effect, but also has defects such as silver streaks and splash marks on the molded product appearance. Raise.

Therefore, it has a large obstacle in obtaining a molded product having a narrow shapeable temperature region and a complicated shape or a large-sized, thick molded product.

In order to overcome these problems, modification of the resin itself, improvement with additives, improvement of molding processing method, etc. have been carried out.

However, in these methods, the original characteristics of the methacrylic resin are impaired, the working environment is unfavorable, and the effect is not sufficient, so that the fact is that the problem has not yet been sufficiently solved.

As a modification of the resin itself, for example, by copolymerizing a large amount of acrylates, or by lowering the molding temperature by a method of lowering the degree of polymerization of methacrylic resin, it is intended to improve the thermal stability during processing. On the contrary, it is not preferable because it lowers the heat distortion temperature and sacrifices solvent resistance, mechanical properties and the like.

Further, as an improvement by the additive, a small amount of an antioxidant or a radical trapping agent such as an amine-based methacrylic resin,
A method is known in which the thermal decomposition of methacrylic resin is suppressed by adding a phenol type, phosphite type, or sulfur type compound. However, even with these methods, only a small amount can be added because they are colored during the molding process or have an offensive odor remaining in the resin, and therefore a sufficient effect for suppressing thermal decomposition cannot be obtained, making them practical. There are few things.

In order to improve the molding processability, the shape, size and position of the gate of the mold are changed, and the fluidity of the molten resin is improved by attaching a hot liner, but the appearance of the molded product is poor and the yield is reduced. However, these methods have limitations.

As described above, there is still no effective means for suppressing thermal decomposition of the polymer even at the molding temperature on the high temperature side, which imparts thermal decomposition resistance without impairing the original excellent properties of methacrylic resin and shows relatively high fluidity. The current situation is that they have not been found.

(Problems to be Solved by the Invention) In view of these circumstances, the inventors of the present invention have diligently studied,
A methacrylic resin composition obtained by adding a specific compound of a methacrylic polymer introduced with a maleimide compound as a reactive heat stabilizer has excellent optical properties, weather resistance and balance of methacrylic resin. The inventors have found that the thermal decomposition resistance is dramatically improved without sacrificing various properties such as mechanical and thermal properties, and have completed the present invention.

(Means and Actions for Solving Problems) That is, the present invention comprises 50 to 99.5% by weight of methyl methacrylate and the following general formula (I): A polymerizable monomer component consisting of 0.5 to 10% by weight of a maleimide compound and 0 to 49.5% by weight of another polymerizable monomer (however, the total amount of the polymerizable monomer components is 100% by weight). Of the methacrylic polymer (A) and the organophosphorus compound (B) obtained by polymerizing the methacrylic polymer (A) with respect to 100 parts by weight of the methacrylic polymer (A).
The present invention relates to a methacrylic resin composition having an improved thermal decomposition resistance, characterized in that the methacrylic resin composition is contained in an amount of 2 to 2 parts by weight.

The methyl methacrylate used in the present invention may be used as a monomer as it is, or may be used as a polymerizable syrup which is a mixture of a methyl methacrylate polymer and methyl methacrylate obtained by prepolymerizing methyl methacrylate by an ordinary method. . The polymerizable syrup, which is methyl methacrylate or its prepolymer, is used in a proportion of 50 to 99.5% by weight, preferably 80 to 99.5% by weight, in the polymerizable monomer component. When the amount used is less than 50% by weight, the resulting resin cannot maintain the original weather resistance and optical properties of the methacrylic resin, which is not preferable.

The maleimide compound in the present invention is represented by the general formula (I), and examples thereof include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide and N-isobutyl. Maleimide, N-tert-butyl maleimide, N-cyclohexyl maleimide, N-
Phenylmaleimide, N-chlorophenylmaleimide,
N-methylphenyl maleimide, N-naphthyl maleimide, N-octyl maleimide, N-lauryl maleimide, N-stearyl maleimide, 2-hydroxyethyl maleimide, N-hydroxyphenyl maleimide, N-
Methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, N-tribromophenylmaleimide and the like can be mentioned, and one or more of these can be used. Among these maleimide compounds, the optical properties of the polymer,
From the viewpoint of mechanical properties, N-butylmaleimide, N-
Maleimides having a relatively long-chain alkyl group such as octylmaleimide are more preferably used.

The maleimide compound is used as a reactive heat stabilizer when obtaining the methacrylic polymer (A), and is used in a proportion of 0.5 to 10% by weight, preferably 3 to 8% by weight in the polymerizable monomer component. . 0.5% by weight of maleimide compound
If it is less than 10% by weight, the resulting resin composition cannot be given sufficient thermal decomposition resistance, and if it exceeds 10% by weight, the moldability and impact resistance of the obtained resin composition are deteriorated. Not preferable.

In the present invention, other polymerizable monomers may be contained in addition to the methyl methacrylate and the maleimide compound represented by the general formula (I). Other polymerizable monomers that can be used are not particularly limited as long as they are copolymerizable with at least one of the methyl methacrylate and the maleimide compound, and examples thereof include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. Methacrylates; acrylates such as methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate; unsaturated carboxylic acids such as methacrylic acid, acrylic acid; acrylonitrile, methacrylonitrile, styrene, maleic acid, fumaric acid and its esters, etc. I can name it. The other polymerizable monomer is used in a range that does not impair the object of the present invention, if necessary, and is used in an amount of 49.5% by weight or less in the polymerizable monomer component. If the amount used exceeds 49.5% by weight, the original characteristics of the methacrylic resin will not be exhibited.

Furthermore, in the present invention, the organophosphorus compound (B) used to complete the improved thermal stability is a component that improves thermal stability by decomposing the peroxide generated during processing, and, for example, Tris (nonylphenyl) phosphite,
Tris (mono- and di-nonylphenyl) phosphite, tristearyl phosphite, triphenylphosphite, diphenylisodecylphosphite, phenylisodecylphosphite, tetra (tridecyl) -4,
4'-isopropylidenediphenyl phosphite and the like are mentioned, and among them, nonylphenyl phosphite compounds are preferable. The organic phosphorus compound (B) is used in the range of 0.001 to 2 parts by weight with respect to 100 parts by weight of the methacrylic polymer (A). If the amount used is less than 0.001 part by weight, the effect of improving the thermal stability is difficult to be recognized, and even if the amount used exceeds 2 parts by weight, the improvement in the thermal stability commensurate with the amount used is not obtained and it is practically meaningless. Is.

The methacrylic resin composition having improved thermal decomposition resistance of the present invention comprises the methacrylic polymer (A) and the organic phosphorus compound (B) in the above proportions, and this alone is sufficient for thermal stability. However, if the organic sulfur compound (C) is further added, the thermal decomposition resistance is dramatically improved due to a synergistic effect. Examples of the organic sulfur compound (C) that can be used include ditridecyl-3,3'-thiodipropionate, dilauryl, thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol-tetrakis- (Β-
Lauryl-thiopropionate), 2-mercaptobenzimidazole and the like, among which thioether type organic sulfur compounds are preferable.

The organic sulfur compound (C) is a methacrylic polymer (A) 10
It is used in the range of 0.001 to 1 part by weight with respect to 0 part by weight.
If the amount used is less than 0.001 part by weight, a synergistic effect for improving the thermal decomposition resistance is difficult to be exhibited, and even if the amount used exceeds 1 part by weight, the improvement in thermal decomposition resistance commensurate with the amount used is not recognized.

The organic sulfur compound (C) may be simply mixed with the composition consisting of the methacrylic polymer (A) and the organic phosphorus compound (B), but when used during the polymerization of the methacrylic polymer (A), The effect as a transfer agent is also exhibited secondarily, and it is preferable that the chain transfer agent represented by the conventional mercaptans is substituted so that the resin composition is free from odor.

The method for obtaining the methacrylic resin composition of the present invention having improved thermal decomposition resistance is not particularly limited, and various conventionally known methods can be used. For example, a known polymerization method represented by an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, a solution polymerization method, etc., using the above-mentioned monomer component, if necessary, an organic sulfur compound (C) as a chain transfer agent. The methacrylic polymer (A) obtained in the above is blended with the granular substance, powdery substance, pellets and crushed substance of the organic phosphorus compound (B) and optionally the organic sulfur compound (C), and a Henschel mixer, V After mixing by a known mixing method such as a mold blender, melt-kneading with an extruder to obtain an extruded product or forming a pellet, and a method for injection or extrusion molding material may be used.

The methacrylic resin composition of the present invention, if desired, further known additives, for example, dyes, colorants such as pigments, plasticizers,
Lubricants, UV stabilizers and the like may be appropriately contained.

(Effects of the Invention) Since the methacrylic resin composition of the present invention having improved thermal decomposition resistance is obtained by blending a specific compound with the methacrylic polymer (A) obtained by using a maleimide compound, the methacrylic resin is Its thermal decomposition resistance has been dramatically improved without sacrificing its original excellent optical properties, weather resistance, and well-balanced mechanical and thermal properties.

Therefore, the methacrylic resin composition having improved thermal decomposition resistance of the present invention can be suitably used as a member for vehicles, electric / electronic devices, office equipment and the like.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. still,
In the examples, parts are by weight unless otherwise specified.

Example 1 Methyl methacrylate 95 parts, N-butyl maleimide 5 parts, tert-butyl peroxy 2-ethylhexanoate (polymerization initiator) 0.5 part, ditridecyl-3,
3'-thiodipropionate (Sumitomo Chemical Co., Ltd.,
Sumilizer TL) 0.5 parts of a polymerizable monomer component was charged into a reaction vessel equipped with a reflux condenser, an inert gas inlet tube, a thermometer and a stirrer together with 300 parts of deionized water and 1.5 parts of sodium polymethacrylate, The suspension was stirred at high speed to give a suspension.
Then, the reaction liquid was heated to 80 ° C. by blowing nitrogen gas through the inert gas introduction tube to start the polymerization reaction. Five hours after the initiation of the polymerization reaction, the temperature of the reaction solution was raised to 95 ° C., and stirring was continued for another two hours to complete the polymerization. The obtained copolymer was cooled, filtered, washed with water, and dried to obtain beads of a methacrylic polymer.

Next, to 100 parts by weight of this methacrylic polymer (1), 0.5 parts by weight of tris (nonylphenyl) phosphite (MARK 329K, manufactured by ADEKA ARGUS CHEMICALS CO., LTD.) Was added and thoroughly mixed with a Henschel mixer, and then vented. Using an attached 30 mm extruder, the mixture was melted and kneaded under the conditions of a vent pressure of 30 mmHg and a cylinder temperature of 250 ° C., and pelletized.

The obtained methacrylic resin pellets were subjected to high-pressure / high-speed injection molding at a molding temperature of 250 ° C. using an injection molding machine (PS60E9A manufactured by Nissei Plastic Industry Co., Ltd.), and the resulting methacrylic resin composition (1) was obtained. The appearance of the molded product was colorless and transparent, and no silver was generated. Further, the performance of this molded product was tested, and the results are shown in Table 1.

The total light transmittance is measured according to JIS-K-6717 and Izod impact strength according to JIS K-7110, and the thermal decomposition temperature is a DSC-DTA device at a temperature increase rate of 10 ° C / min. Was measured. Also, the appearance was based on visual observation.

Examples 2 to 3 and Comparative Examples 1 to 5 As Example 1 except that the polymerizable monomer component, the organic phosphorus compound and the organic sulfur compound used in Example 1 are as shown in Table 1. Molded articles of methacrylic resin compositions (2) to (3) and comparative resin compositions (1) to (5) were obtained in the same manner.

The performance of these molded articles was tested and the results are shown in Table 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 59-49254 (JP, A) JP 60-147414 (JP, A) JP 43-9753 (JP, B1)

Claims (3)

[Claims] 1. Methyl methacrylate 50 to 99.5% by weight, the following general formula (I): A polymerizable monomer component consisting of 0.5 to 10% by weight of a maleimide compound represented by and 0 to 49.5% by weight of another polymerizable monomer (however, the total amount of the polymerizable monomer components is 100% by weight). Of the methacrylic polymer (A) and the organic phosphorus compound (B) obtained by polymerizing the organic phosphorus compound (B) with respect to 100 parts by weight of the methacrylic polymer (A). A methacrylic resin composition having improved thermal decomposition resistance, characterized in that it is contained in a proportion of 1 part. 2. The methacrylic resin composition according to claim 1, which further comprises the organic sulfur compound (C) in a proportion of 0.001 to 1 part by weight with respect to 100 parts by weight of the methacrylic polymer (A). . 3. The methacrylic resin composition according to claim 2, wherein the organic sulfur compound (C) is used during the polymerization of the methacrylic polymer (A).