JPS5910369B2 - Manufacturing method of 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 that has weather resistance and impact resistance and is moldable by extrusion molding, injection molding, etc.

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
It is known that the best way to combine good impact strength with good transparency is to disperse fine elastomer particles having the same refractive index in a hard resin such as methacrylic resin. In this case, a conjugated diene rubber is often used as the elastomer component, and among these, for example, according to Japanese Patent Publication No. 17806/1989, impact resistance can be improved by selecting a diene rubber composition with almost no loss of transparency. can be 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 polymethyl methacrylate, non-diene rubbers such as acrylic acid lower alkyl ester polymers, ethylene-vinyl acetate copolymers or EPDM are used.
However, in order to ensure the transparency of the hard resin, the refractive index of the elastomer component should match that of the hard resin that is the matrix.
It becomes necessary to copolymerize the second component during the production of the elastomer. Producing a rubber component with the same refractive index as the matrix hard brittle resin by copolymerization
Not only is the process complicated, but also an undesirable phenomenon of variations in transparency arises due to the difference in temperature dependence of the refractive index between the rubber and the resin. 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 inventors previously prepared methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate without using an emulsifier.
By heterogeneously polymerizing and polymerizing in an aqueous medium, an emulsion of a hard polymer is prepared, and then a monomer that can be polymerized to form a rubbery polymer is added to this emulsion. It has been found that a resin with excellent impact resistance and transparency can be obtained over a wide temperature range without impairing the weather resistance of the resin.

According to this method, 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, in the above method, unless the molecular weight of the seed polymer produced in the first stage polymerization is appropriately lowered, the resulting resin composition will have a high melt viscosity and therefore have poor fluidity during molding. The problem arises that it is low. One possible solution to this problem is to perform the first stage polymerization by adding a molecular weight regulator such as mercaptans to lower the molecular weight of the resulting sheet polymer, but the final resin composition obtained in this case The plate obtained by press-molding does not exhibit transparency and becomes cloudy.
Therefore, an object of the present invention is to provide a method for producing a methacrylic resin composition that does not lose transparency even if the molecular weight of the sheet polymer is increased to the point where the final resin composition can be molded in the above method. This object is achieved according to the invention by heterogeneously polymerizing methyl methacrylate or a monomer mixture based on methyl methacrylate in an aqueous medium in the presence of a molecular weight regulator and without the use of an emulsifier. An emulsion of a hard polymer with a controlled molecular weight is prepared, and then a monomer that polymerizes to give a rubbery polymer, or a monomer mixture mainly composed of this monomer (hereinafter referred to as a rubbery monomer) is added to the emulsion. unsaturation in an amount of 0.01 to 10 mol % of the rubbery monomer. 'This can be achieved by polymerizing by adding a polyfunctional monomer consisting of diol esters of hydrochloric acid or divinyl compounds. The first point of the present invention is to obtain a polymer emulsion by polymerizing a methyl methacrylate-containing monomer in an aqueous medium without using a so-called emulsifier.

As the polymerization catalyst, a redox catalyst such as a potassium persulfate-sodium thiosulfate copper monosulfate system as described in JP-A-50-61484 is preferably used. In this polymerization system 4, no new particles are generated during the polymerization, and so-called "seed" polymerization is completely carried out. By adjusting the polymerization conditions such as the amount of catalyst and the concentration of monomer charged, a sheet polymer emulsion 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, and may be mainly methyl methacrylate, acrylic acid esters such as methacrylic acid, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, α-methylstyrene. It may also be a mixture with other monomers such as styrene derivatives. These other monomers are used for modification of methacrylic resins.
The second point of the present invention is to adjust the molecular weight of the methyl methacrylate-containing sheet polymer by adding a molecular weight regulator during the sheet polymerization. The molecular weight regulator for the sheet polymer used in the present invention can be selected from those commonly used in radical polymerization. For example, it is possible to use organic sulfur compounds, ie thio acids, mercaptans such as benzyl mercaptan and aliphatic mercaptans and mixtures thereof, such as octyl mercaptan, lauryl mercaptan, dodecyl mercaptan, nitrohydrazine, amino compounds, carbon tetrachloride, etc. can. The amount of the molecular weight regulator to be used should primarily be determined depending on the desired moldability of the resulting resin composition, but it should also be determined in terms of maintaining the transparency and high impact strength of the molded product. The amount of the polyfunctional monomer used in combination with the monomer should also be taken into consideration when determining the amount. Generally, a suitable amount of molecular weight regulator to be used can be determined by simple preliminary experiments, and the amount ranges from about 0.01 to 5 mole percent of the methyl methacrylate-containing monomer. More specifically, the amount of molecular weight regulator used is 10,000 to 1
A sheet polymer with a molecular weight of ,000,000 is obtained. The third key point in the present invention is to perform polymerization by adding a rubbery monomer 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, monomers that produce rubber-like polymers when polymerized are monoolefin monomers that produce rubber-like elasticity at room temperature when polymerized, such as methyl acrylate, ethylene, etc. Preferably used are lower alcohol esters such as , i-propyl and butyl esters, higher alcohol esters of acrylic acid such as octyl ester, and higher alcohol esters of methacrylic acid such as octyl methacrylate.

These rubber monomers can be used alone or mixed with each other or with small proportions of other monomers. As the small proportion of other monomers, radically polymerizable vinyl monomers used for rubber modification are preferred. In the present invention, a polyfunctional monomer consisting of diol esters of unsaturated acids or divinyl compounds in an amount of 0.01 to 10 mol % based on one monomer is combined with these rubber monomers to form the second stage. Performing polymerization is the fourth important point in imparting a high degree of transparency to the resulting resin composition. The polyfunctional monomer consisting of diol esters of unsaturated acids or divinyl compounds as used herein refers to compounds having two or more radically polymerizable double bonds, such as ethylene glycol diacrylate, ethylene dimethacrylate, etc. Diol esters of unsaturated acids such as glycols and polyethylene glycol diacrylates
Alternatively, divinyl compounds in a narrower sense such as divinylbenzene are used.

Diols of unsaturated acids for rubber monomers. If polymerization is carried out without using any polyfunctional monomers consisting of stills or divinyl compounds, the resulting resin becomes cloudy and loses transparency; on the other hand, if an excessively large amount of polyfunctional monomers is used, , the impact resistance l of the resin decreases and the transparency also decreases. Therefore, there is a range of suitable amounts of polyfunctional monomers to be used, but this amount also depends on the molecular weight of the sheet polymer, so it should be determined appropriately depending on the molecular weight of the sheet polymer in the first stage polymerization. Should. Within the molecular weight range of the sheet polymer that usually provides good moldability (the amount of the molecular weight modifier described above), the amount of polyfunctional monomers consisting of diol esters of unsaturated acids or divinyl compounds is The amount is in the range of 0.01 to 10 mol%, preferably 0.05 to 5 mol%, based on the monomer. The rubber monomer is
It 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. Conversely, if 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 proceeded for at least 5091), preferably 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 particles of the dispersed polymer obtained in the form of latex according to the present invention range from 0.1 to
It has a uniform particle size distribution of 0.4μ, and can be easily salted out and recovered by mixing the emulsion with a dilute aqueous calcium chloride solution or a dilute aqueous magnesium chloride solution.

The resulting particulate resin can be subjected to molding as it is after passing through and drying, and can also be subjected to extrusion molding and injection molding. Since the methacrylic resin composition obtained in the present invention 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. In a 500 m2 three-ring flask equipped with a reflux condenser, a thermometer insertion tube, and a mixing device, 300 parts of pure water, 47 parts of methyl methacrylate, and 0.2 parts of lauryl mercaptan were placed under a stream of high-purity nitrogen. , while maintaining a constant stirring state (320 rpm).
-1 mol/t potassium persulfate aqueous solution 5m2 (system concentration 1.4X10-3 mol/t) and 1 x 10-1 mol/t sodium thiosulfate aqueous solution 5m2 (system concentration 1.4X1
When 0-3 monomer and 5 x 10-3 mol/t of copper sulfate aqueous solution 1me (concentration in the system 1.4 x 10-5 mono/t) were added, the polymerization system immediately became cloudy and polymerization started. .

The temperature of the polymerization system was maintained at 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. 15 parts of butyl acrylate and 0.05 part of ethylene glycol dimethacrylate were added to this system to continue polymerization. Polymerization was complete after about 4 hours. Add 200 parts of 0.5% calcium chloride aqueous solution to the system, salt out and coagulate the resulting polymer, wash with water to remove the catalyst, and leave to dry overnight in a hot air dryer kept at 70°C. A white powder was obtained. Capillary rheometer (Instron model 3211, capillary length 0.9944i)
The melt viscosity during extrusion is 2 x 104 poise (shear rate: 110 sec-1
, temperature: 230°C). The pellets were injection molded at 230°C to obtain samples for physical property measurement. Table 1 shows the physical property measurement results. Xenon weather tester (X made by Shimadzu Corporation)
As a result of conducting a weather resistance test in accordance with JIS-Al41O using a material (Model W-60-3), 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, during the second stage polymerization, styrene 2.8
Polymerization was carried out in exactly the same manner as in Example 1, except that 50% of the polymer was added together with butyl acrylate and ethylene glycol dimethacrylate.

The melt viscosity of the obtained composite particles when extruded using a capillary rheometer (same as in Example 1) was 2×10
4 poise (shear rate: 110 sec-1, temperature: 23
0°C). The pellets were injection molded at 230°C and the physical properties of the sheet were measured. The results are shown in Tables 1 and 2. Example 3 The same method as in Example 1 was used except that the amount of lauryl mercaptan was changed to 0.08 parts during sheet polymer production and the amount of ethylene glycol dimethacrylate during the second stage polymerization was changed to 0.03 parts. Polymerization was carried out.

The melt viscosity of the obtained composite particles when extruded using a capillary rheometer (same as in Example 1) was 3×10
4 poise (shear rate: 110 sec - temperature: 230°C
). - The pellets were injection molded at 230°C and the physical properties of the sheet were measured. The results are shown in Tables 1 and 2. Example 4 In Example 1, the amount of lauryl 5 mercaptan in the sheet forming step was changed to 0.08 parts, the amount of butyl acrylate in the second stage polymerization was changed to 18 parts, and ethylene glycol dimethacrylate was replaced with Polymerization was carried out in exactly the same manner as in Example 1, except that 0.05 part of divinylbenzene was used.

The melt viscosity of the obtained composite particles when extruded using a 4-pillar rheometer (same as in Example 1) was 1.
The temperature was 5×10 (shear rate: 110 sec−1, temperature: 230° C.). The pellets were injection molded at 230°C and the physical properties of the sheet were measured. The results are shown in Tables 1 and 2. Example 5 In Example 1, 47 parts of methyl methacrylate and 4.5 parts of butyl acrylate were used instead of 47 parts of methyl methacrylate, and 0.2 parts of dodecyl mercaptan was used instead of lauryl mercaptan. Polymerization was carried out in exactly the same manner as in Example 1, except that 11 parts of butyl acid was used.

The melt viscosity of the obtained composite particles when extruded using a capillary rheometer (same as in Example 1) was 2×10
4 poise (shear rate: 110 sec-1, temperature: 23
0°C). Injection mold the pellets at 230°C,
The physical properties of the sheet were measured. The results are shown in Tables 1 and 2.
Example 6 Polymerization was carried out in exactly the same manner as in Example 1 except that 15.7 parts of ethyl acrylate was used instead of butyl acrylate in the second stage polymerization.

The extrusion melt viscosity and injection moldability using a capillary rheometer (same as in Example 1) were almost the same as in the case of butyl acrylate. The physical properties of the sheet are shown in Tables 1 and 2. Comparative Example 1 In Example 1, 15 parts of butyl acrylate and 0.05 parts of ethylene glycol dimethacrylate were used instead of methyl methacrylate and lauryl mercaptan in the first stage sheet-forming polymerization, and butyl acrylate and 0.05 parts of ethylene glycol dimethacrylate were used in the second stage. Polymerization was carried out in exactly the same manner except that 47 parts of methyl methacrylate and 0.2 parts of lauryl mercaptan were used in place of ethylene glycol dimethacrylate.

A sheet obtained by press-molding the obtained composition was milky white and brittle. Comparative Example 2 When the composite particles obtained in Example 1 without using lauryl mercaptan were press-molded, a transparent and impact-resistant sheet was obtained.

However, this resin composition had a high melt viscosity when extruded by the Kyurast manufacturer, and it was impossible to form it into pellets.
Comparative Example 3 In Example 1, when ethylene glycol dimethacrylate was not used during the second stage polymerization, the sheet obtained by press-molding the obtained composite particles became opaque.

Comparative Example 4 Polymerization was carried out in exactly the same manner as in Example 1, except that 2 parts of ethylene glycol dimethacrylate was used during the second stage polymerization.

Claims (1)

[Claims] 1 A rigid polymer with a controlled molecular weight by heterogeneously polymerizing methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate in an aqueous medium in the presence of a molecular weight regulator and without using an emulsifier. Then, in this emulsion, a monomer that gives a rubbery polymer by polymerization or a monomer mixture mainly composed of the monomer, and 0.0% of the monomer or the monomer mixture are prepared.
1. A method for producing a transparent impact-resistant methacrylic resin composition, which comprises adding a polyfunctional monomer consisting of a diol ester of an unsaturated acid or a divinyl compound in an amount of 0.01 to 10 mol % and carrying out polymerization.