JPS58217501A - New copolymer - Google Patents

Abstract

PURPOSE:A coloress, transparent copolymer excellent in mechanical strength, heat resistance and heat stability, comprising a major proportion of methyl methacrylate, (meth)acrylic acid and a six-membered cyclic acid anhydride. CONSTITUTION:A copolymer comprising 70-96wt% methyl methacrylate unit, 1-10wt% (meth)acrylic acid unit and 3-20wt% six-membered cyclic acid anhydride unit of the formula, wherein R1 and R2 are each H or CH3, and having a viscosity of 3-20cP when measured at 25 deg.C in a methyl ethyl ketone solution of a copolymer concentration of 10wt%. This copolymer is a thermoplastic resin having a crystal-clear transparency comparable to that of polystyrene or a methyl methacrylate copolymer, mechanical strength and heat resistance comparable to those of a styrene/acrylonitrile copolymer and heat resistance superior to that of a commercially available styrene/maleic anhydride copolymer as well as having remarkably excellent heat stability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new copolymer, and more specifically, a copolymer mainly composed of methyl methacrylate units, which is colorless and transparent and has excellent mechanical strength, heat resistance, and thermal stability. It is about merging.

In recent years, there has been a particularly strong demand for resins that have excellent heat resistance, mechanical strength, and oil resistance, are colorless and transparent, and are inexpensive for various applications such as microwave tableware, light electrical parts, and industrial parts. It's coming.

By the way, among resins currently on the market, polycarbonate resin (hereinafter abbreviated as PC) is known as a colorless, transparent resin with excellent mechanical strength and heat resistance. However, this resin is an engineering plastic and is expensive, so it has not been widely used.

In addition, methyl methacrylate resin (hereinafter abbreviated as PMMA)
is commercially available at a relatively low price and has good mechanical strength, but has the disadvantage of poor heat resistance.

On the other hand, 1-polystyrene is the cheapest, has good colorless transparency, and has particularly excellent moldability, so it is widely used as a molding material for light electrical parts, daily miscellaneous goods, etc. However, this resin does not have sufficient mechanical strength, heat resistance, and oil resistance, and therefore, various copolymers mainly containing styrene have been proposed to compensate for these drawbacks.

Examples of copolymers mainly composed of styrene include styrene-acrylonitrile copolymer (hereinafter referred to as As resin), styrene-methyl methacrylate copolymer (hereinafter referred to as M
S resin), styrene-maleic anhydride copolymer (abbreviated as S resin), styrene-maleic anhydride copolymer (
The most basic copolymers are known as SMA resin), styrene-acrylic acid copolymer (hereinafter referred to as SAA resin), and styrene-methacrylic acid copolymer (hereinafter referred to as SMAA resin). However, all of these copolymers are not necessarily satisfactory overall.

For example, As resin and MS resin show good moldability,
Although it is commercially available as a copolymer that has excellent mechanical strength and oil resistance and is relatively easy to manufacture, it has poor heat resistance.

On the other hand, SMA resins, SAA resins, and SMAA resins use unsaturated acids or unsaturated acid anhydrides, so although their heat resistance is improved, other properties are still unsatisfactory. That is, although SMA resin is excellent in colorless transparency and heat resistance, its mechanical strength is insufficient, being equivalent to that of polystyrene, and it is also inferior in oil resistance. Regarding SAA resins and SMAA resins, copolymers with sufficiently high molecular weights and uniform composition distributions can be easily obtained by a simpler copolymerization method than in the case of SMA resins, but these resins When subjected to thermal history, the carboxyl groups in the polymer tend to cause dehydration reactions between molecules, producing a gel-like substance that may impair the appearance of the molded product. Furthermore, since these copolymers contain carboxylic acids, the intermolecular hydrogen bonds are strong, and therefore the residual stress of the injection molded product is large, and the mechanical strength itself is low. It has the disadvantage of generating cracks, making it unsuitable for normal injection molding applications [Polymer Chemistry,! ,
883 (1969)).

In this way, in copolymers mainly composed of styrene,
Although the mechanical strength increases by introducing acrylonitrile and methyl methacrylate, the heat resistance is still insufficient. Although a significant improvement can be expected, it has drawbacks such as low mechanical strength.

Therefore, in order to eliminate these drawbacks and obtain a resin that satisfies the overall requirements, we developed a terpolymer consisting of styrene, a comonomer for improving mechanical strength, and a comonomer for improving heat resistance. Many great efforts have been made to develop this technology.

However, acrylonitrile, which is most effective in improving mechanical strength, easily chemically reacts with acids and anhydrides to produce a gel-like substance, causing significant yellowing of small products and making it impossible to obtain colorless and transparent resins. No, it cannot be used simultaneously with unsaturated acids and unsaturated acid anhydrides, which are comonomers for improving heat resistance. Therefore, methyl methacrylate is the most common comonomer for improving mechanical strength.

For example, a terpolymer of styrene, methyl methacrylate, and maleic anhydride has been proposed (Japanese Patent Application Laid-Open No.
5-102614). However, in this terpolymer, a large amount of maleic anhydride monomer remains unreacted, so when this terpolymer is used for processing such as injection molding, gas is released. There is a problem in that the appearance of the molded product is impaired.

In this way, the unreacted maleic anhydride monomer remains in the above-mentioned terpolymer because maleic anhydride is consumed extremely smoothly during copolymerization of styrene and maleic anhydride. When polymerization progresses and polymerization is finally completed, virtually all of the maleic anhydride has been consumed, but in the case of a ternary system in which methyl methacrylate has been introduced, the polymerization consumption rate of maleic anhydride is significantly reduced. This is because a considerable amount of maleic anhydride monomer remains in the final copolymer, making it difficult to separate and recover this maleic anhydride in the unreacted material and solvent recovery step.

On the other hand, in the terpolymers of styrene-methyl methacrylate-acrylic acid and styrene-methyl methacrylate-methacrylic acid, there were no problems with the terpolymers using maleic anhydride, and the polymerization reaction was completed. Unreacted monomers can be easily removed from the resulting copolymer, and the resulting resin and injection molded products using the same are completely colorless and transparent. However, even with these terpolymers, the problems associated with SAA resins and SMAA resins have not been completely resolved, and there is a problem of formation of gel-like substances due to intermolecular dehydration reactions of carboxyl groups in the polymer. .

As described above, although there is a strong demand for a resin that satisfies the overall requirements, no resin that fully satisfies these requirements has yet been found.

In view of these circumstances, the inventors of the present invention have conducted extensive research into developing a resin that can meet the above comprehensive requirements.
A copolymer mainly composed of methyl methacrylate as a monomer unit and containing a predetermined amount of acrylic acid or methacrylic acid, and an acid anhydride having a six-membered ring structure derived therefrom, or an acrylic acid ester in addition to these. Alternatively, the inventors discovered that a copolymer containing a predetermined amount of aromatic vinyl compound units could achieve the objective, and based on this knowledge, the present invention was completed.

That is, the present invention provides (A) methyl methacrylate unit 7
0 to 96% by weight, (B) 1 to 10% by weight of acrylic acid or methacrylic acid units, and (C) general formula (R1 and R in the formula
2 is a hydrogen atom or a methyl group) and the viscosity of a methyl ethyl ketone solution at a temperature of 25° C. is 3 to 20 centipoise at a concentration of 10% by weight. and (A) 70 to 96% by weight of methyl methacrylate units and at least one monomer unit selected from acrylic esters or aromatic vinyl compounds; (B) 1 to 10% by weight of acrylic acid or methacrynoic acid units, and (C) 3 to 20 six-membered cyclic acid anhydride units represented by the general formula (in which R1 and R2 are hydrogen atoms or methyl groups) % by weight, and (A) if it contains an acrylic ester as a monomer unit, its content is 10% by weight or less, and if it contains an aromatic vinyl compound, its content is 67% by weight or less, and The present invention provides a copolymer characterized in that a methyl ethyl ketone solution having a copolymer concentration of 10% by weight has a viscosity of 3 to 20 centipoise at a temperature of 25°C.

Methyl methacrylate, which is the main monomer unit in the copolymer of the present invention, plays a role in improving mechanical strength and oil resistance, and its content is 70% in the first invention. In the second invention, the sum of the methyl methacrylate unit and at least one monomer unit selected from acrylic esters and aromatic vinyl compounds is in the range of 96% by weight. is 70-96% by weight
is within the range of If the content of methyl methacrylate units is lower than the above range, the mechanical strength of the copolymer will not be sufficiently improved.

However, in the second invention, the acrylic ester or aromatic vinyl compound contained as the monomer unit (A) plays a role in improving the fluidity and thermal stability of the copolymer, and It is sufficient to contain at least one of the following, and the content is 10% in the case of acrylic ester.
% by weight or less, and in the case of an aromatic vinyl compound, it is 67% by weight or less.

If the content of acrylic acid ester units exceeds 10% by weight, the heat exchange properties will decrease, and if the content of aromatic vinyl compound units exceeds 67% by weight, mechanical properties and oil resistance will decrease.

Examples of the acrylic ester unit include methyl acrylate and ethyl acrylate, with methyl acrylate being particularly preferred.

Examples of the flexible aromatic vinyl compound unit include styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, tert-butylstyrene, and chlorostyrene, with styrene being particularly preferred.

The (B) monomer unit acrylic acid or methacrylic acid in the copolymer of the present invention plays a role in improving the heat resistance of the copolymer, and its content is 1 to 10% by weight.
If it exceeds 10% by weight, the thermal stability will decrease and a gel-like substance will be formed.

The six-membered cyclic acid anhydride of the monomer unit (0) in the copolymer of the present invention is derived from acrylic acid or methacrylic acid,
It has a structure represented by the above general formula (1), and at the same time improves the thermal stability of the copolymer and completely eliminates the thermal instability factor of acrylic acid and methacrylic acid. This further serves to improve the thermal stability of the copolymer.

Quantification of the six-membered cyclic acid anhydride in this copolymer was based on measurement using an infrared spectrophotometer,
The absorptions at and 1760 crn' are distinct from those of other carboxylic acids and carboxylic acid esters and are unique to the copolymer of the present invention. Its content is in the range of 3 to 20% by weight, and if it is less than 3% by weight, it will not have the effect of improving heat resistance and thermal stability, while if it exceeds 20% by weight, the fluidity of the resin will decrease. As a result, moldability deteriorates.

Furthermore, in the copolymer of the present invention, the copolymer concentration is 1
It is necessary that the viscosity of a 0% by weight methyl ethyl ketone solution at a temperature of 25° C. be in the range of 3 to 20 centipoise. If the viscosity is less than 3 centimeters, the mechanical strength will decrease, and if it exceeds 20 centimeters, the fluidity will decrease and the moldability will deteriorate.

The copolymer obtained by satisfying the above requirements is
Even if the solution is allowed to stay at 70° C. for 4:1, the viscosity of the solution changes within 10%, and is characterized by excellent thermal stability.

All conventional radical copolymerization methods can be used to produce the copolymer of the present invention, but in suspension polymerization and emulsion polymerization, the copolymer monomer is dissolved in the aqueous phase, which improves the polymerization rate and system. This is disadvantageous because it may give unfavorable results to stability. Particularly preferred is a continuous bulk polymerization method, and in order to make the composition of the copolymer as uniform as possible and to have excellent appearance and mechanical properties, the polymerization reactor is preferably of a complete mixing type.

The copolymer of the present invention has colorless transparency equivalent to polystyrene or PMMA, mechanical strength and oil resistance equivalent to As resin,
It is a high-quality thermoplastic resin that also has heat resistance that exceeds that of commercially available SMA resins. Further, surprisingly, the copolymer of the present invention has extremely good thermal stability, which is even better than various conventionally known styrenic copolymers.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

The following various resins were prepared as known resins for comparison with the copolymer of the present invention.

Polystyrene molecular weight: 285,000, MFR (230°C, 3
．． A load of 9.4y/1o was used.

MMA MFR containing 98.5% by weight of methyl methacrylate units and 1.5% by weight of methyl acrylate units (230°C, 3.8% by weight)
Kg load): ], 9 r/l 0 minutes was used.

AS resin styrene unit 70%, acrylonitrile unit 3.
MFR containing 0% by weight (230℃, 3.8Kg load)
: 3.8g/10 minutes was used.

SMA resin Dilarc 332 manufactured by Arco (styrene unit 85% by weight)
, maleic anhydride unit 15% by weight, MFR: 2.9y/
1o min) was used.

MS resin MS-660 manufactured by Richardson (40% by weight of styrene units, 60% by weight of methacrylic methyl units, MFR:
9.6 r/1o min) was used.

SMAA resin It was manufactured according to the following method.

Styrene 75.2% by weight, methacrylic acid 4.8% by weight,
20% by weight of ethylbenzene was used as a preparation liquid, and 1. ν<'ert-butylperoxy-3.3.5-trimethyl/chlorohexane was used.

This mixture was continuously applied at a rate of IA/hr, with an internal volume of 2 tons.
Polymerization was carried out by supplying the mixture to a jacketed complete mixing reactor.

The polymerization temperature was 136°C. The polymerization reaction solution was continuously taken out and supplied to an unreacted substance degassing device. The resulting polymer was colorless and transparent, and composition analysis by neutralization titration revealed that it contained 92% by weight of styrene units and 8% by weight of methacrylic acid units. When I measured the MFR, it was 5.2y/
It was 10 minutes (230°C, 3.8 to 9 loads).

The methods for measuring each physical property are as follows.

(1) Vicat softening temperature: ASTM D-1525
(2) Tensile strength: J engineering 5K67'81 (3)
Bending strength: ASTMI)-790(4)
MFR7230°C, 3.8Kg load (5) Solution viscosity: Solution viscosity at 25°C of 10% by weight concentration of copolymer in methyl ethyl ketone. A Cannon-Fenske type viscosity tube (≠200) was used.

(6) Colorless transparency: Three thickness test pieces were prepared by injection molding and observed with the naked eye.

, Example I 41% by weight of styrene, 8% by weight of methacrylic acid, 41% by weight of methyl methacrylate, 0% by weight of methyl ethyl ketone
A mixed solution containing 0.1 wt.

1,1-di-tert-butylperoxy7-3.3.5-trimethylcyclohexane was used as a polymerization initiator, and the polymerization temperature was 126°C. A polymerization reaction solution having a solid content of 41% by weight was continuously supplied to a high-temperature vacuum chamber to remove unreacted substances and produce a six-membered cyclic acid anhydride. The results of neutralization titration and composition analysis using an infrared spectrophotometer of this copolymer were as follows: 45% by weight of styrene units, 45% by weight of methyl methacrylate units, 3% by weight of methacrylic acid units, and 6-membered cyclic acid anhydride units. °7% by weight. The viscosity of a methyl ethyl ketone solution containing this copolymer at a concentration of 10% by weight at 25° C. was 9.4 centipoise (Cannon Fenske viscometer No. 200). Next, this copolymer was finely pulverized and left in a nitrogen stream for 4 hours in a heating chamber whose internal temperature was controlled to 270°C, then cooled in a nitrogen stream, and a 10% concentration by weight was prepared in the same manner as above. The viscosity of the methyl ethyl ketone solution at 25°C was measured and found to be 9.4.
It was centiboise.

The composition and physical properties of the monomer units of this copolymer are shown in Table 1 along with the physical properties of other resins.

Comparative Example 1 In Example 1, the polymerization reaction solution having a solid content of 41% by weight that came out of the reaction solution was taken out to the outside without being led to the high temperature vacuum chamber.
It was dissolved in methyl ethyl ketone to give a solution with a solid content of 5% by weight. This solution was poured into a large amount of methanol with vigorous stirring, and the precipitated solids were filtered out and thoroughly washed with methanol.

This solid powder was once again dissolved in methyl ethyl ketone to make a 5% by weight solution, and the above operation was repeated again. This powder was carefully dried under reduced pressure at room temperature.

As a result of neutralization titration and compositional analysis using an infrared spectrophotometer of the obtained copolymer, styrene units were 45% by weight, methyl methacrylate units were 45% by weight, and methacrylic acid units were 10% by weight.
Met. The viscosity of a methyl ethyl ketone solution containing this copolymer at a concentration of 10% by weight at 25° C. was 10.3 centivoise. Further, this copolymer was subjected to a heating test at 270° C. in the same manner as in Example 1.

After the heating test, the copolymer was a gel-like insoluble substance with respect to methyl ethyl ketone. The composition and physical properties of the monomer units of the power-supplying composite are shown in Table 1. 40 parts by weight of methyl ethyl ketone, 0.25 parts by weight of tert-dodecyl mercaptan, ■, 1-bis(
tert-butylperoxy)/chlorohexane 0.04
Parts by weight were added and polymerization was carried out in the same manner as in Example 1.

The obtained copolymer was clear and colorless, and composition analysis by neutralization titration, infrared spectrophotometer, and elemental analysis revealed that 82% by weight of methyl methacrylate units, 3% by weight of methyl acrylate units, and methacrylic acid units. 3% by weight and 12% by weight of six-membered cyclic acid anhydride units. The viscosity at 25° C. of a 10% by weight solution of this copolymer in methyl ethyl ketone was 4.3 centipoise before the heating test and 4.1 centipoise after the heating test.

Table 1 shows the composition and physical properties of the monomer units of the copolymer.

Examples 3-5. Comparative Example 2 A feed solution composition shown in Table 2 was prepared, and polymerization and post-treatment were performed in the same manner as in Example 1.

Table 2 Table 3 shows the composition and physical properties of the monomer units of the obtained copolymer.

Examples 6-8. Comparative Examples 3 to 5 The feed liquid compositions shown in Table 4 were prepared, and polymerization and post-treatment were performed in the same manner as in Example 1.

The composition and physical properties of the monomer units of the obtained copolymer are shown in Table 5 together with those of the copolymer obtained in Example 1.

Examples 9-12. Comparative Examples 6 to 8 The feed liquid compositions shown in Table 6 were prepared, and polymerization and post-treatment were performed in the same manner as in Example 1.

The composition and physical properties of the monomer units of the copolymer obtained are shown in Table 7 together with those of the copolymer obtained in Example 7.

The resins listed in Tables 1, 3, 5, and 7 are all colorless and transparent, but only the copolymer of the present invention has good heat resistance, mechanical strength, and oil resistance. and thermal stability.

Patent applicant Asahi Dow Co., Ltd. Agent Akira Agata

Claims (1)

[Scope of Claims] 1(A) 70 to 96% by weight of methyl methacrylate units, (
B) 1 to 10% by weight of acrylic acid or methacrylic acid units and (C) 3 to 20% by weight of six-membered cyclic acid anhydride units represented by the general formula (in which R1 and R2 are hydrogen atoms or methyl groups) A copolymer comprising: 2 (A) methyl meccrylate unit and at least one monomer unit selected from acrylic esters or aromatic vinyl compounds 7.0 to 96% by weight (B) acrylic acid or methacrylic acid unit 1 -10% by weight, and (0) 3-20% by weight of six-membered cyclic acid anhydride units represented by the general formula (in which R1 and R2 are hydrogen atoms or methyl groups), and (A) When an acrylic ester is contained as an 8-unit unit, the content is 10% by weight or less, and when an aromatic vinyl compound is contained, the content is 67% by weight or less, and the copolymer concentration is 10% by weight. A copolymer characterized in that a methyl ethyl ketone solution has a viscosity of 3 to 20 centipoise at a temperature of 25°C.