JPS5910368B2 - Method for producing methacrylic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a transparent methacrylic resin composition having weather resistance and impact resistance.

Although methacrylic resin is widely used due to its excellent transparency and weather resistance, its use is limited due to unsatisfactory mechanical properties such as impact strength. Many methods have been proposed to improve this drawback, but the best way to combine good impact strength and good transparency is to use a fine elastomer with the same refractive index as a hard resin such as methacrylic resin. It is known to disperse particles. In this case, conjugated diene rubber is often used as the elastomer component, and according to Japanese Patent Publication No. 43-17806, by selecting a diene rubber composition, the elastomer component has almost no loss in transparency and durability. Improved impact properties are achieved. However, when a diene rubber is used as the elastomer component, a decrease in weather resistance cannot be avoided. In order to impart impact resistance without impairing the weather resistance of hard resins, attempts have been made to use non-diene rubbers such as acrylic acid lower alkyl ester polymers, ethylene-vinyl acetate copolymers, or EPDM. However, in this case as well, in order to ensure the transparency of the hard resin, it is necessary to copolymerize the second component during the production of the elastomer in order to match the refractive index of the elastomer component to that of the hard resin that is the matrix. Producing a rubber component with the same refractive index as the matrix hard and brittle resin by copolymerization not only complicates the process, but also increases the temperature dependence of the refractive index of the rubber and resin. An undesirable phenomenon of variation in the resulting transparency also occurs.
This is an unavoidable problem for transparent impact-resistant resins obtained by dispersing fine elastomer particles having the same refractive index in a hard resin such as methacrylic resin. The present invention uses methacrylic resin that does not impair weather resistance and has excellent impact resistance and transparency over a wide temperature range.
According to the present invention, methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate is produced by a simple method that does not require a refractive index matching method. An emulsion of a hard polymer is produced by heterogeneous polymerization in an aqueous medium without any oxidation. This can be achieved by adding polymers (hereinafter sometimes referred to as rubber monomers) and carrying out polymerization. As described above, according to the method of the present invention, a methacrylic resin composition that has both impact resistance and transparency can be produced in a simple process without considering the refractive index difference between the hard resin and the rubber phase. However, the most important thing here is to obtain a polymer emulsion by polymerizing the methyl methacrylate-containing monomer in an aqueous medium without using a so-called emulsifier.

As the polymerization catalyst, redox catalysts such as potassium persulfate, sodium thiosulfate, and copper monosulfate are preferably used. In this polymerization system, no new particles are generated during the polymerization, and so-called "seed" polymerization is completely carried out. By adjusting polymerization conditions such as catalyst amount and temperature, an emulsion of sheet polymer with a particle size of 0.1 to 0.3 μm can be stably obtained. The monomer to be polymerized may be methyl methacrylate alone, or may be a mixture of methyl methacrylate as a main component and other monomers such as methacrylic acid, acrylic acid, methyl acrylate, and ethyl acrylate. These other monomers are used to modify methacrylic resins. Another important point in the present invention is that a rubber monomer having a solubility in water of 1.5% or less is added to the second stage of sheet polymerization.

It is thought that the rubber monomer swells into the sheet particles and becomes a rubber polymer inside the particles. Contrary to the method of the present invention, when the sheet particles are made of a rubbery polymer and methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate is polymerized in the second stage, the desired transparent resin No composition is obtained. In the present invention, a monomer that has a solubility in water of 1.5% or less and that gives a rubbery polymer upon polymerization is a monomer that has a solubility in water of 1.5% or less (Jl weight) at a temperature of 20°C. It is a monoolefin monomer that gives a polymer with rubber-like elasticity when polymerized, such as lower alcohol esters such as propyl ester and butyl ester of acrylic acid.
Higher alcohol esters such as octyl esters and higher alcohol esters such as octyl esters of methacrylic acid are preferably used.

These rubber monomers can be used alone or mixed with each other or with small proportions of other monomers, and together with the rubber monomers, 0.1 Higher impact strength can be obtained by combining ~5% by weight of polyfunctional monomers. The rubber monomer is preferably used in an amount of 5 to 40% by weight of the hard polymer obtained by polymerizing the methyl methacrylate-containing monomer in the first stage. If a large amount is used, the impact resistance increases, but the softening point of the resin decreases. On the other hand, when the amount is small, the softening point approaches that of hard resin, but the degree of increase in impact resistance is small. It is desirable to start the polymerization of the rubber monomer after the first stage polymerization of the methyl methacrylate-containing monomer has progressed by 50% or more, preferably after it has been almost completed. Further, when adding the catalyst to the polymerization system, it is desirable to add a small amount of the polymerization catalyst in order to shorten the polymerization time. The dispersed polymer particles obtained in the form of an emulsion according to the present invention have a uniform particle size distribution of 0.1 to 0.4μ, and can be obtained by mixing the emulsion with a dilute aqueous calcium chloride solution or a dilute aqueous magnesium chloride solution. It can be easily salted out and recovered.

The resulting particulate resin can be subjected to molding as it is after being filtered and dried, or can be made into pellets. The methacrylic resin composition obtained in the present invention is
Since it does not contain emulsifiers or stabilizers, there is no deterioration in product quality such as coloring or water resistance due to these.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

All parts are by weight unless otherwise indicated. Example 1 5007F equipped with a reflux condenser, thermometer insertion tube, and grinding type stirring device! 300 parts of pure water and 47 parts of methyl methacrylate were placed in a three-ring flask, and while maintaining constant stirring (320 rpm) under a stream of high-purity nitrogen, a 5 parts of potassium sulfate aqueous solution (concentration in system 1.4 x 10-3 mol/l)
and 1 x 10-1 mol/l sodium thiosulfate aqueous solution 5
part (concentration in the system 1.4 x 10-3 mol/l) and 5 x 1
1 part of a 0-3 mol/11 copper sulfate aqueous solution (concentration in the system: 1.4
Immediately after adding 10-5 monomer/l), the polymerization system became cloudy and polymerization started.

The temperature of the polymerization system was maintained at 70±3° C., and the polymerization was completed in approximately 4 hours. The average particle size of the emulsion obtained was 0.1
It was 5μ. Polymerization was continued by adding 15 parts of butyl acrylate and 0.03 parts of ethylene glycol dimethacrylate to the system, followed by 2 parts of a 1.times.10@-1 mol/l aqueous solution of potassium persulfate. Polymerization was complete after about 4 hours. 0.5% calcium chloride aqueous solution 200% in the system
The resulting polymer was agglomerated by salting out, washed with water to remove the catalyst, filtered, and left to dry in a hot air dryer overnight to obtain a white powder. This powder was press-molded and its physical properties were measured. The results are shown in Table 1. JIS using a xenon weather tester (XW-60V-3 model manufactured by Shimadzu Corporation)
As a result of conducting a weather resistance test according to -Al4lO, these physical properties showed almost no deterioration even after 300 hours of irradiation with a weather tester. The results are shown in Table 2. Example 2 In Example 1, the second stage polymerization was carried out using 21 parts of butyl acrylate and 0.04 parts of ethylene glycol dimethacrylate.
It was carried out in exactly the same way, except that it was carried out using a

The physical properties of the obtained composition are shown in Tables 1 and 2. Example 3 In Example 1, the first stage polymerization was performed using 47 parts of methyl methacrylate and 3 parts of methyl acrylate, and the second stage polymerization was performed using 15 parts of butyl acrylate and 2.7 parts of styrene. The polymerization was carried out in exactly the same manner, except that

The physical properties of the obtained composition are shown in Tables 1 and 2. Comparative example
1 In Example 1, 15 parts of butyl acrylate and 0.03 parts of ethylene glycol dimethacrylate were used instead of methyl methacrylate in the first stage sheet-forming polymerization, and in the second stage, butyl acrylate and ethylene glycol dimethacrylate were used instead of methyl methacrylate. Polymerization was carried out in exactly the same manner except that 47 parts of methyl methacrylate was used.

The press plate of the resulting composition was milky white and brittle. Comparative Example 2 Polymerization was carried out in exactly the same manner as in Example 1, except that 16 parts of methyl acrylate was used instead of butyl acrylate in the second stage polymerization.

Table 1 shows the physical properties of the obtained composition. Comparative Example 3 Polymerization was carried out in exactly the same manner as in Example 1, except that 15 parts of ethyl acrylate was used instead of butyl acrylate in the second stage polymerization.

Table 1 shows the physical properties of the obtained composition. From these results, it is clear that the methacrylic resin composition according to the present invention has excellent weather resistance, impact resistance, and transparency.

Claims (1)

[Claims] 1. A hard polymer emulsion is produced by heterogeneously polymerizing methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate in an aqueous medium without using an emulsifier, and then in this emulsion 1. A method for producing a methacrylic resin composition, which comprises carrying out polymerization by adding a monomer which has a solubility in water of 1.5% or less and which gives a rubbery polymer upon polymerization.