JPH03167245A - Methacrylic resin composition with reduced coloration - Google Patents

Abstract

PURPOSE:To reduce the coloration during molding at a high temperature and improve the heat distortion resistance by compounding a specific copolymer and a specific organophosphorus compd. CONSTITUTION:100 pts.wt. copolymer obtd. by copolymerizing 35-90wt.% methyl methacrylate, 10-35wt.% N-substd. maleimide of formula I (wherein R is H, 1-18C alkyl, cyclohexyl, benzyl, or substd. aryl), and 0-30wt.% other copolymerizable monomer (e.g. styrene) is compounded with 0.005-1 pt.wt. at least one organophosphorus compd. selected from the group consisting of compds. of formulas II, III, and IV (wherein R1, R2, and R3 are each alkyl; R4 is alkyl, cycloalkyl, or phenyl optionally substd. by alkyl; R5, R6, and R7 are each H, alkyl, or alkoxy; and n is 0-3).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a methacrylic resin composition with little coloring. More specifically, the present invention relates to a methacrylic resin composition with excellent heat deformation resistance and improved thermal coloring during shaping at high temperatures. [Prior art and problems to be solved] Methacrylic resins containing N-substituted maleimide compound units in their polymer chains maintain excellent mechanical properties, transparency, etc. equivalent to conventional methacrylic resins, and In recent years, it has attracted much attention as a resin that has excellent heat resistance that conventional methacrylic resins could not have (Japanese Patent Application Laid-Open Nos. 109811-1982, 112612-1982, 1983-
141715, etc.). For example, in the case of tail lamps as automobile parts, higher heat deformation resistance is required compared to conventional ones due to the larger size of the lamp itself, increased heat generation from the illuminance amplifier, and thinner walls due to cost reduction. Also used as meter covers for automobiles and motorcycles,
High resistance to heat deformation is also required for parts that are exposed to extremely high temperatures, such as automotive pickup lenses. However, methacrylic resins containing N-monosubstituted maleimide compound units in their polymer chains have the disadvantage that they are more likely to be colored when heated at high temperatures than normal methacrylic resins, and several improvements have been proposed. For example, a method in which beads obtained by suspension polymerization are washed with alcohol to reduce residual monomer (Japanese Patent Application Laid-Open No. 61-252211), a method in which beads are polymerized using a specific initiator and pelletized under specific conditions ( JP-A No. 63-304013) or hindered phenol compounds, sulfur-containing compounds,
A method of adding a stabilizer such as metal soap is known.

However, in order to obtain a methacrylic resin with little coloring by the above-mentioned method, complicated steps are required, and although the method has a certain degree of coloring improvement effect, it is not always recognized as having a sufficient effect.

Therefore, an object of the present invention is to easily obtain a methacrylic resin that exhibits little coloration and high heat deformation resistance even during heat shaping at high temperatures without going through complicated steps.

[Means to solve the problem]

In view of the current situation, the present inventors have made extensive studies and found that it is possible to incorporate a specific organic phosphorus compound into a specific group of methacrylic copolymers containing monosubstituted maleimide compound units in the main chain ε. The present inventors have discovered that a resin composite sole with high resistance to heat deformation and which is significantly prevented from discoloration can be obtained by this method, and the present invention has been completed. That is, the gist of the present invention is that 35 to 90% by weight of methyl methacrylate and 10 to 35% of N-substituted maleimide.
11%, and other monomers copolymerizable with these 0-3
Based on the weight part of copolymer 1OO consisting of 011f%, the formula or R (wherein R. RsI R& and R each represent a hydrogen atom, an alkyl group, or an alkoxy group, and n is an integer of 0 or 1 to 3.
It is a methacrylic resin set/precept with little coloration containing 5 to 1 parts by weight.

The present invention will be explained in detail below.

In the copolymer of the present invention, the methyl methacrylate unit is the main monomer unit of the copolymer and plays a role in improving transparency and mechanical strength. The content of methyl methacrylate is 35 to 90% based on the copolymer.
% by weight, preferably in the range 40-88% by weight. If the content is less than 35% by weight, mechanical strength and transparency will decrease, which is undesirable, while if it exceeds 90% by weight, the effect of improving heat deformation resistance will be small and undesirable. The other main unit used in the present invention, the N-substituted maleimide compound unit, plays a role in improving heat deformation resistance. The content of N-7 maleimide is 10 to 35% by weight, preferably 12 to 30% by weight based on the copolymer.
Weight%. If the content is less than 10% by weight, the effect of improving heat deformation resistance will be small, which is undesirable, while if it exceeds 35% by weight, transparency and mechanical strength will decrease, which is not preferred. This N-monosubstituted maleimide compound is a maleimide compound represented by R (wherein R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cyclohexyl group, a benzinole group, or a substituted aryl group). N-cyclohexylmaleimide, pJ-tert-butylmaleimide, N-penzylmaleimide, maleydo,
N-methylmaleimide, N-ethynolemaleimide, N-
(2-chlorophenyl)maleimide, N- (2.6
-dimethylphenyl> monomer units such as malei bulk. More preferably, N-cyclohexylmaleimide, N-tert-butylmaleimide, N-(2
-chlorophenyl)maleimide.

In addition, the copolymer specified in the resin composition of the present invention may be
If necessary, other monomers copolymerizable with the above monomers can be used, and the content thereof is 0 to 30% by weight,
Preferably it is 0 to 25% by weight. If this content exceeds 30% by weight, it is not preferable because it causes a decrease in mechanical strength, a decrease in heat deformation resistance, or a decrease in transparency. Examples of other copolymerizable monomers include aromatic vinyl compounds such as styrene, vinyltoluene, and α-methylstyrene; acrylic ester compounds such as methyl acrylate, ethyl acrylate, and butyl acrylate; and methacrylic acid. Examples include methacrylic acid ester compounds such as ethyl, butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, phenyl methacrylate, tripromophenyl methacrylate, dicyclopentanyl methacrylate, and methacrylic acid.

The organic phosphorus compound used in the present invention is contained in the copolymer and plays a role in preventing coloration due to heating. The organic phosphorus compound has the formula and R7 (in the formula, R. It represents an atom, an alkyl group, or an alkoxy group, and n is 0 or an integer of 1 to 3.

In the above general formula, R+, lh, Rs. Ra,
R%, R6. R. will be explained in detail. R+, Rg and R are each an alkyl group, and although there is no particular restriction on the number of carbon atoms, an alkyl group having usually 1 to 18 carbon atoms, preferably 4 to 9 carbon atoms is used. R4 is an alkyl group, a cycloalkyl group, or a phenyl group which may be substituted with alkyl, and the number of carbon atoms in the alkyl group is not particularly limited, but usually has 1 to 18 carbon atoms, preferably 4 to 18 carbon atoms.
The alkyl group of l8 is used @ RS + R6 and R are each a hydrogen atom, an alkyl group or an alkoxy group, and the number of carbon atoms in the alkyl group is not particularly limited, but usually has 1 to 8 carbon atoms, preferably 1 ~4 lower alkyl groups are used, and the alkoxy groups include methoxy group,
Ethoxy group, butoxy group, etc. are preferably used.

These organic phosphorus compounds can be used alone or in combination of two or more. The content thereof is 0.005 to liii parts of at least one of the organic phosphorus compounds, preferably 0.01 parts by weight, per 100 parts by weight of the copolymer.
~0.5 parts by weight. This amount is o. If the amount is less than 1 part by weight, the effect of preventing heat discoloration will not be sufficient, and if it exceeds 1 part by weight, the effect will not improve in proportion to the amount added, and there will be no economic benefit, and silver streaks may occur during injection molding. This is undesirable because appearance defects such as scratches are likely to occur.
In the phosphite compound represented by formula (I), tris(2,4-di-tert-butylphenyl)
Phosphite, tris(2,6-di-tert-butyl-4-methylphenyl)phosphite, tris(monononylphenyl)phosphite, monononylphenylbis(dinonylphenyl)phosphite, dinonylphenylbis(monononyl) Phenyl) phosphite, tris(dinonylphenyl) phosphite, etc. are preferably used as the organic phosphorus compound of the present invention.

In addition, in the pentaerythritol-based phosphite compound represented by the formula (U), ditridecylbentaerythritol diphosphite, diisodecylpentaerythritol diphosphite, distearylpentaerythritol diphosphite, bis(monononylphenyl)
Pentaerythritol diphosphite, bis(dinonylphenyl) pentaerythritol diphosphite, bis(2,4-di-ter t-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-te
r t-Butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,6-diter t
-butyl-4-ethylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methoxycarbonylphenyl) pentaerythritol diphosphite, hydrogenated bisphenol A/pentaerythritol phosphite polymer, etc. It is preferably used as an organic phosphorus compound in the present invention. Also, the above formula (1
), 9,10-dihydro-9-oxer 10-phosphaphenanthrene-io-oxide, 2-methyl-9
．． 10-dihydro9-oxer 10-phosphaphenanthrene-10-oxide, 6-methyl-9.10
-dihydro-9-oxer 10-phosphaphenanthrene-10-oxide, 2,6-dimethyl-9. 1
0-dihydro9-oxer10-phosphaphenanthrene-lO-oxide, 6,8-di-tert
-butyl-9,10-dihydro-9-oxer-10-phosphaphenanthrene-10-oxide, 6-methoxy9,10-dihydro-9-oxer-10-phosphaphenanthrene-e0-oxide 10-methyl-
9.10-dihydro-9-oxer 10-phosphaphenanthrene-10-oxide, 10 ethoxy9.
10-dihydro-9-oxer 10-phosphaphenanthrene-10-oxide and the like are preferably used as the organic phosphorus compound of the present invention.

More preferable examples of these organic phosphorus compounds include dinolylphenylbis(monononylphenyl)phosphite, diisodecylpentaerythritol diphosphite, ditridecylpentaerythritol diphosphite,
9.10-Dihydro-9-oxa 10-phosphaphenanthrene-10-oxide is mentioned, and each can be used alone or in combination of two or more. The method for producing the copolymer constituting the resin composition of the present invention is not particularly limited, and bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, etc. are possible.

Polymerization initiators used in these polymerizations include penzyl peroxide, lauroyl peroxide, ter
Peroxide initiators such as tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl peroxy hexahydroterephthalate, 2.2-azobisisobutyronitrile, 2.2 azobis-2. Examples include azo initiators and redox initiators such as 4-dimethylvaleronitrile and azobiscyclohexanone-1-carbonitrile. In addition, as a chain transfer agent to be used as necessary, n-octyl merbutane,
Examples include mercabutanes such as n-dodecylmercabutane and 1-2-ethylhexyl thioglycolate, and hydrocarbons such as α-methylstyrene dimer.

In the present invention, the organic phosphorus compound can be added to the copolymer by adding it into the monomer mixture, adding it to the polymerization reaction solution at the beginning of the polymerization reaction, or by various kneading methods after the completion of the polymerization. There are various methods of adding, and any method may be used.

Further, in the resin composite sole of the present invention, ultraviolet absorbers, antioxidants, lubricants, release agents, dyes, antistatic agents, flame retardants, etc. can be added as necessary.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In this example, the b value measured with a Hunter colorimetric colorimeter was used as a coloring scale, and the colorimetric b value reduction rate was also shown for the purpose of showing the coloring improvement effect. Total light transmittance and haze are ASTM-01003, Bickert softening point is ASTM-D1525, tensile strength is ASTM
- Each was measured in accordance with 0638. Example-1 Methyl methacrylate 80% by weight, N-cyclohexylmaleimide 15% by weight, lauroyl peroxide 0.
2 5Phr Sn-dodecylmercabutane 0.25P
20 kg of monomer solution consisting of hr and ion exchange water 9 9
．． 6 7% by weight, copolymer of sodium methacrylate and styrene-P-sodium sulfonate 0.03% by weight
and 0.3% by weight of sodium sulfate.
kg into a 100j' pressure-resistant polymerization tank with a jacket,
Stir under nitrogen atmosphere and pass warm water through the jacket for 75 minutes.
Polymerization was initiated at ℃.

Three hours after the start of polymerization, the temperature of the system was raised to 120°C by passing steam through the jacket, and the temperature was maintained for an additional 2 hours to complete polymerization. Uniform beads were obtained in good yield, which were washed with water and dried. 0.0% diisodecylpentaerythritol diphosphite per 100 parts by weight of the beads obtained. After adding 1 part by weight and mixing with a Henshil mixer, the mixture was melt-kneaded using a 40φ extruder at a cylinder temperature of 250°C to obtain pellets. Using this pellet, the cylinder temperature is 250
The product was injection-molded at ℃ to obtain a flat plate shaped product. The resulting molded product was evaluated and had a Bickert softening point of 130°C, a total light transmittance of 92%, and a haze of 0.6N thick plate. 4%, colorimetric b value 1
．． 1. A tensile strength of 700 kg/1 was obtained. Comparison N-1 A shaped product was obtained in the same manner as in Example 1 except that diisodecylpentaerythritol diphosphite was not used, and when measured, the Bickert softening point was 130°C, and the total light transmittance of the 6u thick plate was 90%, haze 0.6%, color measurement b
The value was 2.3, and the tensile strength was 700 kg/c+4.

Examples 2 to 4, Comparative Examples 2 to 5 Prestige products were obtained in the same manner as in Example 1 except for changing the organic phosphorus compound to be added as shown in Table 1 or using additives other than organic phosphorus compounds. The evaluation results are shown in Table I. Examples 5 to 6, Comparative Examples 6 to 7 Shaped products were obtained in the same manner as in Example 1, except that the amount of diisodecylpentaerythritol diphosphite added was changed, and the evaluation results are shown in Table 2.

In addition, the obtained blanks were injection molded using an injection molding machine under the conditions of a cylinder temperature of 270°C and a cooling time of 200 seconds, and the surface appearance of the obtained 10 flat plate-shaped products was visually observed. The state of defect occurrence was evaluated. The evaluation was performed based on the following criteria, and the results are shown in Table 2.

Good: No defects such as silver streaks occur. Poor: Silver streaks occur. Examples 7 to 12, Comparative Examples 8 to 10 The composition of the copolymer was changed and 9.10-dihydro- was used as a phosphaphenanthrene-based compound. 9-oxer 10-
A molded product was obtained in the same manner as in Example 1 except that phosphaphenanthrene-10-oxide was used, and the evaluation results are shown in Table 3.

Example 13 Azobisisobutyronitrile was used as a polymerization initiator. I
A molded product was obtained in the same manner as in Example 1 except that diisodecylbentaerythritol diphosphite was charged into a pressure-resistant polymerization tank together with the monomer using Phr, and as a result of evaluation, the Vincat softening point was 129°C, 6n thick plate total light transmittance 92%, haze 0.4%, colorimetric b value 1.1,
The tensile strength was 690 kg/cd.

Margins below [Effects of the Invention] As described above, the methacrylic resin compound of the present invention can suppress heat discoloration by containing the above-mentioned specific organic phosphorus compound, and can suppress the coloration due to heat discoloration. Since it hardly loses its other excellent physical properties, it is useful as a resin material for lamps, lenses, etc. that require heat deformation resistance and transparency.

Claims (1)

[Scope of Claims] 1. 100% by weight of a copolymer consisting of 35 to 90% by weight of methyl methacrylate, 10 to 35% by weight of N-substituted maleimide, and 0 to 30% by weight of other monomers copolymerizable with these. For each part, ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) Or ▲There are mathematical formulas, chemical formulas, tables, etc.▼...・(III) (In the formula, R_1, R_2, and R_3 are each an alkyl group, R_4 is an alkyl group, a cycloalkyl group, or a phenyl group that may be substituted with alkyl, and R_5, R_6, and R_7 are each a hydrogen atom, an alkyl group, or represents an alkoxy group, and n is 0 or an integer of 1 to 3.) At least one organic phosphorus compound represented by 0.00
A methacrylic resin composition with little coloring, characterized in that it contains 5 to 1 parts by weight.