JPH09165486A - Methacrylic resin composition with improved thermal decomposition resistance - Google Patents

Abstract

(57) [Abstract] [Problem] Methacrylic resin dramatically improves its thermal decomposition resistance without sacrificing its original excellent optical properties, weather resistance, and well-balanced mechanical and thermal properties. Improve to. SOLUTION: Methyl methacrylate 50 to 99.5
% By weight, a specific maleimide compound 0.5 to 10% by weight and other polymerizable monomers 0 to 49.5% by weight (however, the total amount of the polymerizable monomer components is 10,
0% by weight. ) Polymerized methacrylic polymer (A), methacrylic polymer (A) 0.001 to 2 parts by weight per 100 parts by weight of the organic phosphorus compound (B), methacrylic polymer (A) A methacrylic resin composition containing 0.001 to 1 part by weight of a thioether type organic sulfur compound (C) per 100 parts by weight.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a methacrylic resin composition having improved thermal decomposition resistance.
The present invention relates to a methacrylic resin composition which can be preferably used for molded products having a complicated shape such as electric / electronic devices and office equipment, and large-sized, thick molded products.

[0002]

2. Description of the Related Art Conventionally, methacrylic resin has excellent weather resistance and optical properties, and has a relatively well-balanced performance in mechanical properties and thermal properties. It has been put to practical use in many fields such as electrical and electronic equipment and office equipment.

However, since methacrylic resin is generally close to the moldable temperature range and the thermal decomposition temperature, it has poor thermal stability at the time of molding, and when extruded or injection molded, it depolymerizes from the molecular chain end, There is a tendency for the amount of residual material in the molded product 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, this is a major obstacle in obtaining a molded product having a narrow moldable temperature region and a complicated shape or a large-sized, thick molded product. In order to overcome these problems, the resin itself has been modified, additives have been added, and molding processes have been improved. 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.

The solution of the resin itself is to improve the thermal stability during processing by lowering the molding temperature by, for example, copolymerizing a large amount of acrylates or lowering the polymerization degree of methacrylic resin. However, on the contrary, the thermoforming temperature is lowered, and the solvent resistance and mechanical properties are sacrificed, which is not preferable. Further, as an improvement by the additive, a small amount of an antioxidant or a radical trapping agent such as an amine-based or phenol-based methacrylic resin,
A method is known in which the thermal decomposition of methacrylic resin is suppressed by adding a phosphite-based or sulfur-based 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, and they are practical. There are few things.

[0006] Further, as an improvement of the molding method, 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 runner. Since it also leads to a decrease in yield,
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.

[0007]

The object of the present invention is to provide a methacrylic resin which has excellent optical properties, weather resistance and well-balanced mechanical and thermal properties without sacrificing the properties thereof. It is to improve the thermal decomposition resistance.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a methacrylic resin composition obtained by adding a specific compound to a methacrylic polymer introduced with a maleimide compound as a reactive heat stabilizer. It was found that the thermal decomposition resistance of a product dramatically improves without sacrificing various properties such as excellent optical properties, weather resistance and well-balanced mechanical and thermal properties inherent in methacrylic resin. The present invention has been completed.

That is, the present invention comprises 50 to 99.5% by weight of methyl methacrylate, the following general formula (I):

[0010]

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(Wherein R represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aryl group or a substituted aryl group), and a maleimide compound 0.5 to 1
A polymerizable monomer component consisting of 0% by weight and another polymerizable monomer 0 to 49.5% by weight (however, the total amount of the polymerizable monomer components is 100% by weight) is polymerized. The ratio of the methacrylic polymer (A) and the organic phosphorus compound (B) thus obtained, relative to 100 parts by weight of the methacrylic polymer (A), 0.001 to 2 parts by weight of the organic phosphorus compound (B). And the thioether type organic sulfur compound (C) is added to the methacrylic polymer
(A) A methacrylic resin composition having improved thermal decomposition resistance, characterized in that it comprises 0.001 to 1 part by weight of the thioether type organic sulfur compound (C) per 100 parts by weight. .

The methyl methacrylate used in the present invention may be used as a monomer, 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 a conventional method. May be. Methyl methacrylate or a polymerizable syrup which is a prepolymer thereof is used in a proportion of 50 to 99.5% by weight in the polymerizable monomer component. If the amount used is less than 50% by weight, the resulting resin cannot retain 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 above general formula (I), for example, maleimide, N
-Methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-chlorophenyl Maleimide, N-methylphenyl maleimide, N-octyl maleimide, N-lauryl maleimide, N-stearyl maleimide, 2-hydroxyethyl maleimide, N-hydroxyphenyl maleimide, N-methoxyphenyl maleimide, N-carboxyphenyl maleimide, N-nitro Examples thereof include phenylmaleimide and N-tribromophenylmaleimide. Of these, one or two
More than one species can be used. Among these maleimide compounds, maleimides having a relatively long-chain alkyl group such as N-butylmaleimide and N-octylmaleimide are more preferably used from the viewpoint of the optical and mechanical properties of the polymer.

The maleimide compound is a methacrylic polymer
It is used as a reactive heat stabilizer when obtaining (A), and is 0.5 to 10% by weight, preferably 3 to 10% by weight in the polymerizable monomer component.
It is used at a ratio of 8% by weight. When the amount of the maleimide compound used is less than 0.5% by weight, it is not possible to impart sufficient thermal decomposition resistance to the obtained resin composition, and 10% by weight
If the amount exceeds 1, the molding processability and impact resistance of the obtained resin composition are deteriorated, which are both unfavorable.

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 4% in the polymerizable monomer component.
It is used in an amount of 9.5% by weight or less. The amount used is 49.
If it exceeds 5% by weight, the original characteristics of the methallyl resin will not be exhibited.

Furthermore, in the present invention, the organophosphorus compound (B) used to complete the improved thermal stability is a component which improves the thermal stability by decomposing the peroxide generated during processing. , For example, tris (nonylphenyl) phosphite, tris (mono- and di-nonylphenyl) phosphite, tristearylphosphite, triphenylphosphite, diphenylisodecylphosphite,
Examples thereof include phenylisodecyl phosphite and tetra (tridecyl) -4,4'-isopropylidene phenyl phosphite. Among them, nonylphenyl phosphite compounds are preferable. The organic phosphorus compound (B) is used in an amount of 0.001 to 2 parts by weight based on 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 cannot be obtained and the effect is substantially improved. It is meaningless.

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,
Although this alone has sufficient thermal stability, when an 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, dilaurylthiodipropionate, dimyristyl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate. Examples thereof include pionate, pentaerythritol-tetrakis- (β-lauryl-thiopropionate), and 2-mercaptobenzimidazole. Among them, thioether type organic sulfur compounds are preferable.

The organic sulfur compound (C) is used in an amount of 0.001 to 1 part by weight based on 100 parts by weight of the methacrylic polymer (A). If the amount used is less than 0.001 part by weight, a synergistic effect for improving the thermal decomposition resistance is difficult to develop, 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 also appears secondarily, and it is preferable to substitute a conventional chain transfer agent represented by mercaptans, so that the resin composition is free from odor.

The method for obtaining the methacrylic resin composition having improved thermal decomposition resistance of the present invention is not particularly limited, and various conventionally known methods can be used. For example, a known polymerization method typified by an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, a solution polymerization method, etc., by using the organic sulfur compound (C) as a chain transfer agent as necessary for the monomer component. Methacrylic polymer (A) obtained by the granular material, powder, pellets,
The crushed material is blended with the organophosphorus compound (B) and, if necessary, the organosulfur compound (C), and the mixture is mixed by a known mixing method such as a Henschel mixer or a V-type blender, and then melt-kneaded by an extruder and extruded. A molded product may be obtained or formed into pellets, and injection or a material for injection molding may be used.

If desired, the methacrylic resin composition of the present invention may further contain well-known additives such as colorants such as dyes and pigments, plasticizers, lubricants, and UV stabilizers. [Operation] Methyl methacrylate resin is excellent in transparency, but has a drawback that it is inferior in thermal decomposition resistance.

In order to improve the thermal decomposition resistance of the methyl methacrylate resin, a methacrylic resin composition prepared by adding a relatively small amount of maleimide compound to methyl methacrylate has been proposed. This resin composition is very excellent in thermal decomposition resistance, but has a drawback that the resin is colored. Practical value is low if the colorless and transparent characteristic of methyl methacrylate resin is impaired.

In the present invention, an organic phosphorus compound (B) and a thioether type organic sulfur compound (C) are contained in a specific ratio in a methacrylic polymer component (A) obtained by adding a specific amount of a maleimide compound to methyl methacrylate. The addition of the above makes it possible to provide a resin composition which has sufficient thermal decomposition resistance, is colorless and transparent, and can effectively exhibit various advantages of the methyl methacrylate resin.

Although the coloring problem can be solved by adding only the organophosphorus compound (B), the thermal decomposition resistance is slightly lowered. Since a specific methacrylic polymer component (A) was used to improve the thermal decomposition resistance, if the decrease in thermal decomposition resistance is large in order to solve the coloring problem, a resin composition as Product value will be low. If the thermal decomposition resistance is low, the originally colorless methyl methacrylate resin may be used as it is.

However, in the present invention, when the organic phosphorus compound (B) and the thioether type organic sulfur compound (C) are used together, the problem of coloring can be solved while having sufficient thermal decomposition resistance. Although the reason why such an effect is achieved is not clear, thioether type organic sulfur compounds
It is speculated that the addition of (C) exerts some kind of interaction or synergistic action that suppresses the phenomenon of thermal decomposition resistance deterioration due to the addition of the organophosphorus compound (B) alone.
Moreover, the interaction or synergistic action between the thioether type organic sulfur-based compound (C) and the organic phosphorus-based compound (B) does not impair the coloring prevention function of the organic phosphorus-based compound (B). , It is considered to be a specific combination.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below, but the present invention is not limited to the following examples. In the examples, "parts" represent parts 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 in a reaction vessel equipped with a reflux condenser, an inert gas introduction tube, a thermometer and a stirrer, 300 parts of deionized water, It was charged with 1.5 parts of sodium polymethacrylate and stirred at high speed to obtain a suspension. Then, the reaction solution was heated to 80 ° C. while blowing nitrogen gas from the inert gas introduction tube to start the polymerization reaction. Five hours after starting the polymerization reaction, the temperature of the reaction solution was raised to 95 ° C., and stirring was continued for another 2 hours to complete the polymerization. The obtained copolymer was cooled, filtered, washed with water, and dried to obtain methacrylic polymer beads.

Next, the methacrylic polymer (1) 100
0.5 parts by weight of tris (nonylphenyl) phosphite (made by Adeka Argus Chemical Co., Ltd., MARK 329K)
After adding 1 part by weight and thoroughly mixing with a Henschel mixer, vent pressure 30mmH using a vented 30mm extruder
g, melt-kneaded at 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 type manufactured by Nissei Plastic Industry Co., Ltd.), and the resulting methacrylic resin composition ( The appearance of the molded product of 1) 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 method for measuring the total light transmittance is JIS-
K-6717, Izod impact strength is JIS K-71
The thermal decomposition temperature was measured with a DSC-DTA apparatus at a temperature rising rate of 10 ° C./min to measure the weight reduction start temperature according to 10, respectively.
Also, the appearance was based on visual observation. Example 2 and Comparative Examples 0 to 5 Example 1 and Comparative Example 0 to 5 except that the polymerizable monomer component, the organic phosphorus compound and the organic sulfur compound used in Example 1 were as shown in Table 1. Molded articles of the methacrylic resin composition (2) and the comparative resin compositions (0) to (5) were obtained in the same manner.

The performance of these molded products was tested, and the results are shown in Tables 1 and 2. In the table, Sumilizer TL (manufactured by Sumitomo Chemical Co., Ltd.) was used as the organic sulfur compound. As the organic phosphorus compound, MARK 329K
(Adeka Argus Chemical Co., Ltd.) was used. The asterisk * indicates that it was added during the production of the methacrylic polymer.

[0030]

[Table 1] ────────────────────────────────── Example 1 Example 2 Comparative Example 0 Comparative Example 1 ────────────────────────────────── Polymerizable monomer components (parts) Methyl methacrylate 95 92 97 100 N -Butyl maleimid 5 ---- N-octyl maleimid-3--N-cyclohexyl maleimid-8 --- Organosulfur-based compounds (part) 0.5 * 0.5 --- Organophosphorus-based compounds (part) 0.5 0.5 0.5 --- ─── ─────────────────────────────── <Performance of molded products> Total light transmittance (%) 93.0 92.9 93.0 93.0 Iso impact strength (kg-cm / cm) 2.3 2.2 2.4 2.2 Thermal decomposition temperature (℃) 273 281 270 262 Appearance (discoloration) Colorless Colorless Colorless Colorless 〃 (Silver strikes) Good Good Good Good Generation ─ ────────────────────────────────

[0031]

[Table 2] ────────────────────────────────── Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 ────────────────────────────────── Polymerizable monomer component (parts) Methyl methacrylate 100 80 99.8 90 N -Butyl maleimid --- 0.2-N-octyl maleimid ------ N-cyclohexyl maleimid-20-10 Organic sulfur compounds (part) 0.5 * 0.5 * 0.5 * -Organophosphorus compounds (part) 0.5 0.5 0.5 --- ──────────────────────────────── <Molded product performance> Total light transmittance (%) 92.9 92.4 93.0 92.8 Isot Impact strength (kg-cm / cm) 2.2 1.1 2.2 2.2 Thermal decomposition temperature (℃) 263 310 264 286 Appearance (discoloration) Colorless yellow coloration Colorless pale yellow coloration 〃 (Silver strikes) Good occurrence Good occurrence Good ────────────────────────────────── Comparison of the characteristics of the above examples and comparative examples Example 1
The methyl methacrylate resin is excellent in transparency but inferior in thermal decomposition resistance. The methacrylic resin composition of Comparative Example 5, in which a relatively small amount of a maleimide compound was added to methyl methacrylate, is very excellent in thermal decomposition resistance, but has a drawback that the resin is colored. In Comparative Example 0 in which the organophosphorus compound (B) was added to the methacrylic polymer component (A), the coloring problem could be solved, but the thermal decomposition resistance was slightly lowered. In Examples 1 and 2, by using the organic phosphorus compound (B) and the thioether type organic sulfur compound (C) together, the problem of coloring was solved while having sufficient thermal decomposition resistance. Even if the organic phosphorus compound (B) and the thioether type organic sulfur compound (C) are blended,
Comparative Example 2 containing little or no maleimide compound,
4 or Comparative Example 3 in which the maleimide compound content is large, either the coloring or the thermal decomposition temperature is inferior.

[0032]

EFFECTS OF THE INVENTION The methacrylic resin composition having improved thermal decomposition resistance of the present invention comprises a methacrylic polymer (A) obtained by using a maleimide compound, an organic phosphorus compound (B) and a thioether type organic sulfur. Since it contains the compound (C), its thermal decomposition resistance is not sacrificed without sacrificing its original properties such as excellent optical properties, weather resistance, and well-balanced mechanical and thermal properties. The sex has improved dramatically.

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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akiaki Fujiwara 1 992 Nishi-oki, Okihama, Aboshi-ku, Himeji-shi, Hyogo 1 Himeji Laboratory, Nippon Catalysis Chemical Co., Ltd.

Claims (2)

[Claims] 1. Methyl methacrylate 50 to 99.5% by weight, represented by the following general formula (I): (In the formula, R represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aryl group or a substituted aryl group.) 0.5 to 10% by weight of a maleimide compound represented by
And a polymerizable monomer component consisting of 0 to 49.5% by weight of another polymerizable monomer (however, the total amount of the polymerizable monomer component is 1
00% by weight. The methacrylic polymer (A) and the organic phosphorus compound (B) obtained by polymerizing the above) are added to 100 parts by weight of the methacrylic polymer (A).
(B) 0.001 to 2 parts by weight of the thioether type organic sulfur compound (C) is added to the methacrylic polymer (A) 100 parts by weight of the thioether type organic sulfur compound (C). A methacrylic resin composition having improved thermal decomposition resistance, characterized in that it is contained in an amount of 001 to 1 part by weight. 2. A thioether type organic sulfur compound (C)
The methacrylic resin composition according to claim 1, which is added during the polymerization of the methacrylic polymer (A).