KR101142261B1 - Methacrylic copolymer having good chemical resistance and heat resistance - Google Patents

Abstract

The present invention relates to a heat resistant methacrylic copolymer comprising 1 to 15 parts by weight of styrene monomer and 1 to 15 parts by weight of methacrylic acid with respect to 100 parts by weight of methyl methacrylate and methyl methacrylate. The heat resistant methacrylic copolymer according to the present invention has few residual monomers and is excellent in workability as well as excellent in chemical resistance and heat resistance.

Methyl methacrylate, suspension polymerization, glass transition temperature (Tg), chemical resistance, heat resistance

Description

Methacrylic copolymer having good chemical resistance and heat resistance

The present invention relates to a heat resistant methacrylic copolymer having excellent chemical resistance and heat resistance.

Recently, polymethyl methacrylate is typically used as the transparent resin. This is because polymethyl methacrylate has excellent transparency, processability and weather resistance, and is excellent in mechanical properties and thermal properties, and thus can be used in many fields such as optical materials. However, the conventional general polymethyl methacrylate resin has a low allowable limit temperature, that is, a heat deformation temperature of 80 to 95 ° C., and when processed into a thin plate or the like, deformation due to moisture absorption is likely to occur. In addition, there is a disadvantage in that the chemical resistance to lower alcohol is bad, there is a limit to the various needs in recent years, such as display materials, lighting fixtures, optical lenses, etc. is limited.

Accordingly, US Patent No. 4,558,098 prepared a heat resistant resin using methyl methacrylate, maleic anhydride, styrene or alpha methyl styrene. The method can improve the heat distortion temperature but has the disadvantage of lowering transparency due to heat discoloration.

In Japanese Patent Application Laid-Open No. 2002-328240, cyclohexylmaleimide is used as maleimide to improve heat resistance, but this is expensive and toxic to humans.

In addition, Korean Patent Publication No. 2008-0017587 prepared a transparent heat resistant resin using methyl methacrylate, styrene, and a crosslinking agent. However, there is a limit in improving heat resistance with only styrene and a crosslinking agent, and solution polymerization has a disadvantage in that commercialization is difficult due to process difficulties such as solvent recovery.

In U.S. Patent No. 4,965,321, the heat distortion temperature was improved by using methyl methacrylate, styrene, methacrylic acid and acid anhydride with 6-membered ring structure. There is a difficulty.

An object of the present invention is to provide a heat resistant methacrylic copolymer having high light transmittance, excellent chemical resistance, high glass transition temperature (Tg), and low residual monomer.

The present invention relates to a heat-resistant methacrylic copolymer comprising 1 to 15 parts by weight of styrene monomer and 1 to 15 parts by weight of methacrylic acid based on methyl methacrylate and 100 parts by weight of the methyl methacrylate.

The heat-resistant methacryl-based copolymer according to the present invention has not only a few residual monomers in the above range, but also has excellent chemical resistance, high light transmittance, and excellent heat resistance. In addition, the methacrylic copolymer according to the present invention has an advantage of excellent chemical resistance and molding processability.

The present invention has a methyl methacrylate as a main component, it can be produced by copolymerizing a styrene monomer and methacrylic acid in order to improve the chemical resistance and heat resistance.

In the present invention, the styrene-based monomers are styrene, divinylbenzene, vinyltoluene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethyl styrene, isobutyl styrene, t-butyl styrene, o -Bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc. are mentioned, More specifically, styrene can be used. The styrene-based monomer may promote copolymerization of methyl methacrylate and methacrylic acid, and when the content of methacrylic acid is increased, copolymerization with the methyl methacrylate may be deteriorated, but as described above, When copolymerization is carried out by adding a monomer, copolymerization can be improved, and a copolymer having few unreacted monomers can be obtained.

In addition, the heat-resistant methacryl-based copolymer polymerized by adding a styrene-based monomer may be improved in chemical resistance, thermal decomposition and moldability. When the amount of the styrene-based monomer added increases, the heat resistance of the methacryl-based copolymer is lowered, so that 1 to 15 parts by weight of the styrene-based monomer may be used with respect to 100 parts by weight of the methyl methacrylate, specifically 3 to 10% by weight. Parts, more specifically 4 to 8 parts by weight can be used. If it is less than 1 part by weight, the chemical resistance may be lowered. If it is more than 15 parts by weight, the polymerization time is increased, the productivity is lowered, the flowability of the molded article is too high, mechanical properties may be lowered.

Methacrylic acid according to the present invention may contain 1 to 15 parts by weight based on 100 parts by weight of methyl methacrylate, specifically 4 to 8 parts by weight may be used. When used in less than 1 part by weight may lower the heat resistance, when used in excess of 15 parts by weight may reduce the polymerization stability or increase the water hygroscopicity due to the carboxyl group. When the methacrylic acid is contained in the above range, the glass transition temperature (Tg) may be increased.

The methacryl-based copolymer may include a chain transfer agent and a dispersion stabilizer to perform polymerization.

Methacrylic copolymers according to the present invention can be prepared by bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization using conventional free radical polymerization, but in order to minimize contamination by foreign matters, bulk polymerization or suspension polymerization is desirable. Suspension polymerization using a radical initiator can effectively disperse the heat of reaction and has the advantage of relatively simple temperature control. The present invention can be polymerized including a polymerization initiator, and as the polymerization initiator, a peroxide initiator or an azo-based initiator can be used. More specifically, 2,2'-azobis isobutyronitrile can be used.

The polymerization reaction is not limited, but may proceed in the second, the first polymerization may be polymerized by continuing for 30 to 90 minutes at the reaction temperature of 70 ~ 100 ℃, after the first polymerization to 100 to 130 ℃ to continue for 20 to 60 minutes , Secondary polymerization can be carried out.

The chain transfer agent may be used to control the molecular weight of the polymer, and mercapten series may be used, but normal octyl mercaptan may be used to satisfy the conditions of the present invention. The chain transfer agent may not impair the physical properties of the present invention using 0.1 to 0.5 parts by weight based on 100 parts by weight of the monomer mixture.

The present invention may include a dispersion stabilizer, and the dispersion stabilizer may include one or more polymers selected from polyvinyl alcohol or methacrylic acid and methacrylic ester monomers. Specifically, the dispersion stabilizer may be one having a sulfonic acid group that gives hydrophilicity to the side chain with at least one polymer selected from 60 to 100% saponified polyvinyl alcohol or methacrylic acid and methacrylic ester monomers. Examples of the methacryl ester monomers include methyl methacrylate, and the dispersion stabilizer may include an alkali metal salt or an ammonium salt.

The dispersion stabilizer may comprise 0.005 to 1 parts by weight based on 100 parts by weight of the monomer mixture, the polymerization stability may be lowered when the dispersion stabilizer is less than 0.005 parts by weight, the particle size is greater than 1 part by weight It may become so fine that there is a lot of loss during the cleaning and drying process and poor workability. The present invention may also polymerize further including a dispersing aid, and may use boric acid as a specific example.

The heat-resistant methacrylic copolymer according to the present invention is significantly improved in chemical resistance and heat resistance without impairing properties such as transparency and processability, and thus can be used for optical or display materials.

The methacrylic copolymer according to the present invention has a residual monomer content of 700 to 2000 ppm, a light transmittance of 90 to 99%, and a melt flow index (MFI (Melt flow index)) at 230 ^° C. and 3.8 kg of 0.5 to 4.0. It is characterized by that.

The heat-resistant methacryl-based copolymer according to the present invention has not only few residual monomers but also excellent chemical resistance, high light transmittance, and excellent heat resistance. In addition, the methacrylic copolymer according to the present invention has an advantage of excellent chemical resistance and molding processability.

More specifically, when copolymerizing by adding a styrene monomer, the copolymerizability is improved, and a copolymer having few unreacted monomers can be obtained. Moreover, heat resistance can be improved by containing a methacryl-type monomer.

As described above, the heat resistant methacrylic copolymer according to the present invention is significantly improved in chemical resistance and heat resistance without impairing properties such as transparency and processability, and thus can be used for optical or display materials.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to the following examples.

Example 1

1000 g of a monomer mixture consisting of 88% by weight of methyl methacrylate, 5% by weight of styrene and 7% by weight of methacrylic acid was prepared. 2000 g of distilled water in a 5 liter reactor, 1000 g of the above monomer mixture, 8.4 g of 5% polyvinyl alcohol solution (product of Kuraray's POVAL PVA217), 0.1 g of boric acid, 2.5 g of normal octyl mercaptan, 2,2'-azobis isobutyronitrile 1.5g was added and dispersed in the water phase while stirring at 400rpm.

Primary polymerization was carried out at a reaction temperature of 80 ℃. After 1 hour and 10 minutes, the mixed solution became 80 ° C., and the polymerization peak was generated. At the same time, the temperature was raised to 115 ° C. and the second polymerization was performed for 40 minutes, followed by cooling to 30 ° C. The beads obtained by polymerization were washed and dehydrated three times with distilled water, and the beads were dried in an oven. The composition and content of Example 1 are shown in Table 1 below.

Using the obtained beads, the injection specimen was prepared by pressing and injecting, and the physical properties thereof were evaluated.

Example 2 and Comparative Examples 1 and 2

In the same manner as in Example 1, but was changed in the composition and content as shown in Table 1, was carried out in the same manner as in Example 1.

Using the beads obtained above, by pressing and injecting to prepare an injection specimen, physical properties were evaluated and shown as shown in Table 2 below.

Property evaluation

1) Measurement of weight average molecular weight

Water Permeation Chromatography (GPC) was used to measure 0.03 g of beads prepared in Examples 1 and 2 and Comparative Examples 1 and 2 in 0.8 ml of tetrahydrofuran (THF), respectively, and was filtered.

2) Glass transition temperature (℃) measurement

The beads prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were respectively measured at 10 ° C. per minute using DSC (Differential scanning calorimetry).

3) Residual monomer measurement

Measured using GC2010 (column; DB-WAX) manufactured by Shimadzu Corporation, 3 g of beads prepared in Examples 1 to 2 and Comparative Examples 1 to 2 were dissolved in 20 g of acetone, and 25 g of hexane was added thereto. The precipitate was added and precipitated, and only the supernatant was collected and measured.

4) pyrolysis temperature measurement

The pyrolysis temperatures of Examples 1 and 2 and Comparative Examples 1 and 2 prepared above were measured using a thermogravimetric analyzer (TGA), and were evaluated as the temperature when the initial weight decreased by 2%.

5) Light transmittance measurement

Examples 1 to 2 and Comparative Examples 1 to 2 prepared above were injection molded to a thickness of 3.2 mm, respectively, and light transmittance was measured according to ASTM D-1003.

6) Chemical resistance measurement

After the beads prepared in Examples 1 to 2 and Comparative Examples 1 to 2 were prepared to prepare a chemical resistance measurement specimen of 40 mm x 80 mm x 3.0 mm, they were immersed in ethanol and taken out after 3 minutes and washed with pure water. The change of the surface was observed. The observed results were evaluated as good, fine cracks and cracks according to the surface condition.

Table 1

Table 2

Examples 1 to 2 of the present invention from the above examples, the light transmittance is generally excellent compared to the comparative example, the glass transition temperature (Tg) is higher than 120 ℃, good chemical resistance and residual monomer of 2,000ppm or less It can be seen that it can be prepared. In addition, it was confirmed that the glass transition temperature (Tg) was increased as the amount of methacrylic acid used increased, and the addition of styrene improved the chemical resistance.

On the other hand, in Comparative Example 1, although the glass transition temperature (Tg) of the prepared beads was somewhat high at 122 ° C., the light transmittance was inferior, and a large amount of cracks and haze occurred in the chemical resistance measurement. In addition, the residual monomers also increased compared to the examples and the decomposition temperature was also inferior. Comparative Example 2 had a low glass transition temperature (Tg), fine cracks were also found in chemical resistance measurements, and residual monomers were also higher than in Examples. The light transmittance was also slightly lower and the first polymerization time, which is the time from the first polymerization to the peak of the reaction peak, was increased.

Claims (8)

To a methyl methacrylate and 100 parts by weight of the methyl methacrylate, a composition comprising a monomer mixture comprising 4 to 8 parts by weight of styrene monomer, 4 to 8 parts by weight of methacrylic acid, and a chain transfer agent and a dispersion stabilizer. After the first polymerization for 30 ~ 90 minutes at ~ 100 ℃, the temperature is increased to 100 ~ 130 ℃ is produced by secondary polymerization for 20 to 60 minutes, the residual monomer content is 700 ~ 2000ppm, the light transmittance is 90 ~ 99% , Methacrylic copolymer having a melt flow index (MFI (Melt flow index)) of 0.5 ~ 4.0 at 230 ℃, 3.8kg. delete The method of claim 1, The dispersion stabilizer is a methacrylic copolymer comprising a polymer obtained by polymerizing at least one monomer selected from polyvinyl alcohol or methacrylic acid and a methacrylic ester monomer. The method of claim 3, The said dispersion stabilizer is a methacryl-type copolymer containing 0.005-1 weight part with respect to 100 weight part of monomer mixtures. delete delete delete delete