JPH08169912A - Methacrylic resin and production thereof - Google Patents

Abstract

PURPOSE: To provide a methacrylic resin excellent in heat resistance while retaining the characteristics inherent in the resin. CONSTITUTION: This resin contains 0.005-3ppm copper ions. It is produced by a process wherein a copper salt in an amount of 0.005-3ppm in terms of copper ions is added when polymerizing methyl methacrylate alone or a monomer containing at least 80wt.% methyl methacrylate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin having excellent heat resistance and a method for producing the methacrylic resin.

[0002]

2. Description of the Related Art Conventionally, methacrylic resins have been used in various fields such as lighting parts, optical parts and vehicle parts by taking advantage of their outstanding transparency, optical characteristics, graceful appearance, easy processability and dimensional stability. Has been done.

However, since the methacrylic resin has a large thermal decomposability, it does not have a wide moldable region, which is an obstacle to obtaining molded products having a complicated structure, large molded products, molded products made of thick materials, and the like. There are cases.

In order to overcome this problem, modification of polymers and improvement with additives have been carried out. However, these methods are not preferable because they sacrifice the original characteristics of the methacrylic resin and reduce the appearance and productivity. For example, as the polymer modification, a method of copolymerizing methyl methacrylate with a large amount of acrylic acid ester or the like, or a method of reducing the molecular weight of the polymer have been performed. However, such a method is not preferable because it causes a decrease in heat distortion temperature, solvent resistance, and mechanical properties. Further, as a method for improving with additives, a method of adding a heat stabilizer such as a phosphoric acid compound is known, but the effect of heat stabilization is small and there is a problem such as coloring depending on the kind of the compound.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and provide a methacrylic resin having excellent heat resistance while maintaining the original characteristics of the methacrylic resin.

[0006]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that a remarkable heat stabilizing effect can be obtained by incorporating a trace amount of copper ions into a methacrylic resin. The inventors have found out what can be done and have completed the present invention.

That is, the gist of the present invention is as follows.
When polymerizing a methacrylic resin containing 0.005 to 3 ppm of copper ions in the resin and a monomer containing methyl methacrylate alone or at least 80% by weight of methyl methacrylate, a copper salt is used as copper ions in an amount of 0.005 to 0.005. This can be achieved by the method for producing a methacrylic resin containing 3 ppm.

The present invention will be described in detail below.

The methacrylic resin in the present invention is not particularly limited as long as it is a polymer or copolymer mainly containing methyl methacrylate, but it is a polymer or copolymer containing at least 80% by weight of methyl methacrylate. Is preferred. For methacrylic resin, methyl methacrylate alone,
Included are those obtained by polymerizing a monomer mixture of methyl methacrylate and another monomer copolymerizable therewith, and a syrup containing these polymers by a commonly used method.

Other monomers copolymerizable with methyl methacrylate used in the production of methacrylic resin include, for example, alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, and ethyl methacrylate. , Alkyl methacrylates such as stearyl methacrylate, unsaturated carboxylic acids such as acrylic acid and methacrylic acid and salts thereof, aromatic unsaturated compounds such as styrene and α-methylstyrene,
Acrylonitrile etc. are mentioned. These copolymerizable monomers may be used alone or in combination of two or more, and the amount thereof used is 20% by weight in the monomer mixture.
The following is preferred. If the amount used exceeds 20% by weight, the heat resistance temperature and mechanical properties of the obtained methacrylic resin may decrease, and it is necessary to consider the balance of the copolymer composition.

In the present invention, the methacrylic resin contains copper ions in a weight concentration of 0.
It is necessary to include it within the range of 005 to 3 ppm, preferably 0.008 to 1 ppm, and more preferably 0.01 to 0.5 ppm. When the content concentration is less than 0.005 ppm, the heat stabilizing effect is not sufficiently exhibited, and sufficient heat resistance cannot be obtained, which is not preferable. On the other hand, when it exceeds 3 ppm, there are disadvantages such as delay of polymerization and coloring of the obtained resin, which is not preferable.

The method of incorporating copper ions into the methacrylic resin is carried out by adding a copper salt to a monomer or the like when polymerizing the resin. Examples of the acid that forms a salt with copper ions include an organic acid and an inorganic acid, and an organic acid is preferably used in terms of the influence on the transparency of the resin and the like. Examples of the organic acid include acetic acid, propionic acid,
Saturated carboxylic acids such as isobutyric acid and stearic acid, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid, and polyvalent carboxylic acids such as succinic acid, itaconic acid, polymethacrylic acid and their copolymers. However, acetic acid, acrylic acid, methacrylic acid and the like are preferably used.

In a preferred embodiment of the method for producing the heat-resistant methacrylic resin of the present invention, methyl methacrylate alone or at least methyl methacrylate is used at a concentration of 0.005 to 3 ppm with at least one of the above copper salts as copper ions. 80
It can be produced by adding to a monomer containing wt% and polymerizing. The polymerization method may be any method as long as it can be applied to the polymerization of methacrylic resin, and an appropriate method can be selected from suspension polymerization, bulk polymerization, solution polymerization and the like. The polymerization is usually carried out by heating the polymerizable monomer and the copper salt together with a polymerization initiator such as benzoyl peroxide or lauroyl peroxide. At this time, chain transfer agents, lubricants,
Additives such as an ultraviolet absorber can be added to the polymerization system within a range not hindering the present invention.

[0014]

EXAMPLES The present invention will be described in more detail below with reference to examples.

The measuring and testing methods were as follows. In addition, "ppm", "copolymerization ratio", "part",
"%" Represents "weight ppm", "copolymerization weight ratio", "parts by weight", and "weight%", respectively. <Measurement of Copper Ion Concentration> The copper ion concentration is determined by measuring an aqueous solution of a decomposition residue by depolymerization-wet decomposition of a sample with an atomic absorption photometer (Hitachi Z-8100 type). The disassembly operation is as follows.

Decomposition procedure: 3 to 5 g of a sample was placed in a flask and depolymerized at 400 ° C. until the resin content disappeared, and after cooling,
Water 4 ml, sulfuric acid 0.5 ml, 60% perchloric acid aqueous solution 0.5 ml
Is added and the mixture is heated at 100 ° C. again, the temperature is raised to 200 ° C. when the foaming is stopped, and further heated at 400 ° C. when the liquid becomes colorless to obtain a decomposition residue. Then, this is made up to volume with pure water to obtain an aqueous solution. <Measurement of thermal stability> Thermal stability is measured by a thermobalance (Shimadzu TGA-50
Type), the heating weight loss rate is measured under the measurement conditions of 280 ° C., nitrogen atmosphere, and heating time of 60 minutes. <Thermal stability test> Flat plate mold (Cavity size: 70m
mW x 130 mm L x 3 mm thickness) injection molding machine and methacrylic resin molding material were used, injection molding was performed under the conditions of cylinder-retention temperature of 280 ° C and retention time of 3 minutes, and air bubbles (silver) were generated in the molded product. To observe.

[Example 1] Copper ion concentration is 0.012 p
When the thermal stability of the methyl methacrylate-methyl acrylate (copolymerization ratio = 87: 13) copolymer, which is pm, was measured, the heating weight loss rate was 2.7%. When a thermal stability test was performed using this resin pellet molding material, almost no bubbles were generated in the injection molded product.

[Example 2] Copper ion concentration is 0.02 ppm
When the thermal stability of the copolymer of methyl methacrylate-ethyl acrylate (copolymerization ratio = 92: 8) was measured,
The heating weight loss rate was 4.7%.

[Embodiment 3] The copper ion concentration is 0.021 p.
When the thermal stability of the methyl methacrylate-methyl acrylate (copolymerization ratio = 97.5: 2.5) copolymer of pm was measured, the heating loss rate was 3%.

Example 4 Pure water in which a suspension stabilizer was dissolved was charged into a reaction vessel, and then methyl methacrylate 87 was added.
Parts, methyl acrylate 13 parts, copper methacrylate 0.00
A mixed solution of 001 parts and 0.6 part of lauroyl peroxide was introduced into the stirred pure water, and suspension polymerization was carried out at 80 ° C. for 6 hours. A resin was obtained. The heating loss rate of the obtained methacrylic resin was measured and found to be 3.8%.

[Comparative Example] Copper ion concentration is 0.003 ppm
The heating weight loss rate of the methyl methacrylate-methyl acrylate (copolymerization ratio = 87: 13) copolymer is 12.7%.
Met. When a thermal stability test was performed using this resin pellet molding material, a large number of bubbles were generated in the injection molded product.

[0022]

As described above, since the methacrylic resin of the present invention has a low heating loss rate, it is suitable for molding under molding conditions such as a high residence time at a high temperature, and defects such as bubbles are generated in the molded product. Since it is difficult to do so, it is suitable as a molding material and extruded plate material having excellent heat resistance, and a methacrylic resin molded article having excellent heat resistance can be provided.

Claims (2)

[Claims] 1. A resin containing 0.005 to 3 p of copper ions.
Methacrylic resin characterized by containing pm. 2. A method for producing a methacrylic resin, which comprises adding 0.005 to 3 ppm of copper salt as copper ions when polymerizing methyl methacrylate alone or a monomer containing at least 80% by weight of methyl methacrylate. Method.