JPS5914046B2 - 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 can be molded by extrusion molding, injection molding, etc. The present invention relates to a method for producing a methacrylic resin composition whose impact strength is further increased by subjecting it to a mechanical treatment process.

Methacrylic resin is widely used due to its excellent transparency and weather resistance, but its applications are 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 microengineered last 10-mer particles with 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. 43-17806, by selecting the diene rubber composition, conjugated diene rubber can be
5. Improved impact resistance is achieved. However, when a diene rubber is used as an elastomer component, a decrease in weather resistance cannot be avoided, and since the raw material is usually an emulsion-polymerized rubbery polymer, there are disadvantages such as coloring due to residual emulsifier. ■0 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 ethylene-vinyl acetate copolymers are used. Attempts have been made to use propylene copolymer rubber, etc.
However, in this case too, in order to ensure the transparency of the hard resin, efforts are being made to make the refractive index of the elastomer component closely match that of the hard resin that is the matrix.
The present inventors previously prepared a hard polymer emulsion by heterogeneously polymerizing methyl methacrylate or a monomer mixture containing 10 methyl methacrylate in an aqueous medium without using an emulsifier. Then, a monomer (hereinafter abbreviated as rubber monomer s) that gives a rubbery polymer by polymerization is added to this emulsion and polymerized, thereby changing the refractive index of the 1η hard resin phase and the rubber phase. He discovered that it was possible to produce a methacrylic resin composition with good impact resistance and transparency through a simple process without considering consistency too strictly, and filed a patent application (Japanese Patent Application No. 51-389).
8,31805).

At this time, it has also been confirmed that when an acrylic ester is used as a monomer to provide a rubbery polymer, the weather resistance of the methacrylic resin is not impaired. The present inventors further investigated a new manufacturing method for this weather-resistant and impact-resistant methacrylic resin, and found that by applying thermal and mechanical forces such as mastication, the impact strength can be further increased. We have found a way to obtain resin. That is, the present invention provides a hard material with a controlled molecular weight by heterogeneously polymerizing a monomer mixture mainly composed of methyl methacrylate or methyl methacrylate in an aqueous medium in the presence of a molecular weight regulator and without using an emulsifier. A polymer emulsion is prepared, and then, in this emulsion, (a) a monomer that provides a rubbery polymer by polymerization or a monomer mixture mainly composed of the monomer, (b),
(The polymerization is carried out by adding 0.01 to 2 mol% of a polyfunctional monomer and 0.05 to 10 mol% of an oil-soluble peroxide of (c) and (a).) This invention relates to a method for producing a transparent impact-resistant methacrylic resin.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. It is.

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, no new particles are generated during the polymerization, and so-called sheet polymerization is completely carried out. By adjusting the polymerization conditions such as the amount of catalyst and the monomer concentration, 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, and using methyl methacrylate as a living body, acrylic esters such as methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, and α-methylstyrene can be used. It may also be a mixture with other monomers such as styrene derivatives. These other monomers are used to modify methacrylic resins. It is important to control the molecular weight of the sheet polymer by using an appropriate amount of a molecular weight regulator during polymerization in order to make the fluidity of the final resin appropriate. The second key point of the present invention is to perform polymerization by adding a rubber monomer to the second stage of sheet polymerization.

It is believed that the rubber monomer swells into the sheet particles and polymerizes inside the particles to form a rubber polymer.
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 rubbery polymers when polymerized are monoolefin monomers that produce rubbery elasticity at room temperature when polymerized, such as methyl and ethyl acrylate. Preferably used are lower alcohol esters such as , 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 rubbery monomers can be used alone or mixed with each other or with small proportions of other 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 will increase accordingly (the softening point of the resin will be lowered. Conversely, if it is used in a small amount, the softening point will approach that of a hard resin, but
The degree of increase in impact resistance is small. In the present invention, performing the second stage polymerization by combining 0.01 to 2 mol% of a polyfunctional monomer with these rubbery monomers,
The third important point is to appropriately crosslink the resulting rubbery polymer to maintain transparency and impart impact resistance to the final methacrylic resin. The polyfunctional monomer here refers to a compound having two or more radically polymerizable double bonds, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate. Diol esters of unsaturated acids such as allyl acrylate, unsaturated alcohol esters of unsaturated acids such as allyl methacrylate, unsaturated alcohol esters of polybasic acids such as diaryl phthalate, triallyl cyanurate, or divinyl. Divinyl compounds in the narrow sense are used, such as benzene.

If a rubber monomer is polymerized without using any polyfunctional monomer, the resulting resin will not be transparent but cloudy. If the polyfunctional monomer is used in an excessively large amount, the impact resistance of the resin will decrease and the transparency will also decrease. Therefore, there is a range of suitable usage amounts for polyfunctional monomers, but
This amount also depends on the molecular weight of the sheet polymer. Within the molecular weight range of the sheet polymer that usually provides good moldability, the amount of polyfunctional monomer used is preferably in the range of 0.01 to 5 mol% relative to the rubber monomer. When the oil-soluble peroxide mentioned above is used in combination, the amount is in the range of 0.01 to 2 mol%.The fourth point in the present invention is that the oil-soluble peroxide is The oil-soluble peroxide dissolves into the polymer particles and some of it is used as a polymerization initiator.
A portion remains even after the polymerization is completed (for example, the benzoyl peroxide used in Example 1 has a half-life of about 18 hours at 70°C,
Since the polymerization time is on the order of several hours, it is thought that more than half of the polymerization has survived. ) It is thought that it decomposes during molding and acts on crosslinking of the rubber phase or grafting reaction between the resin phase and the rubber phase. In the case of the present invention, the amount of double bonds is extremely small compared to impact-resistant resins using ordinary diene-based rubbers, and it is difficult to imagine that the resin acts by the same mechanism as diene-based rubbers. Regardless, the effect is remarkable. Normally, when using acrylic acid or methacrylic acid ester with a glass transition temperature of -20 to -600C as a rubber component, the Izot impact strength achieved is 20 to 25 wt of the rubber component? In this case, it is in the range of 20 to 25 (with Ftlb/In notch), and in the case of the present invention, this value is greatly exceeded. The oil-soluble peroxides mentioned here are general organic radical initiators such as benzoyl peroxide and lauroyl peroxide. The amount of these oil-soluble peroxides used is 0.05 to 10 of the rubber monomer.
The range is mole %. If the amount used is too small than this range, the impact resistance may decrease when the resin is passed through the mastication process, and if the amount used is too large, the fluidity of the resin will decrease and heat molding will occur. becomes unsuitable for It is desirable that the rubber monomer be polymerized after the first stage polymerization of the methyl methacrylate-containing monomer has progressed by 70 to 90%.

It is also desirable to add a small amount of polymerization initiator when adding it to the polymerization system in order to shorten the polymerization time. A suitable polymerization temperature is 65 to 85°C. If the polymerization temperature is high, the effect of the oil-soluble peroxide is already expressed during the polymerization, but the effect of subsequent heat treatments such as mastication becomes smaller. From the standpoint of stability of the emulsion, a temperature around 70'C is appropriate, and greater impact strength can be obtained by developing the effect of the oil-soluble peroxide in the subsequent mastication process. The particles of the dispersed polymer obtained in the form of a latex according to the present invention have a uniform particle size distribution of about 0.2μ, and can be easily obtained by mixing the emulsion with a dilute aqueous calcium chloride solution, a dilute aqueous magnesium chloride solution, etc. It can be salted out and recovered.

The resulting particulate resin can be subjected to molding after drying. In particular, impact resistance is significantly improved by mechanical and thermal forces applied during 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. Put 1800 parts of pure water, 282 parts of methyl methacrylate, and 1.5 parts of methyl acrylate N lauryl mercaptan into a 3000 m 3-L flask equipped with a reflux condenser, a thermometer insertion tube, and a mixing device. , 36 parts of a 1 x 10-1 mol/t potassium persulfate aqueous solution (concentration in the system: 1.7 x 10-3 mol/t) under a stream of high-purity nitrogen while maintaining a constant stirring state (320 revolutions/min).
) and 36 parts of 1×10−1 mol/t sodium thiosulfate aqueous solution (system concentration 1.7×10−3 mol/t and 5×
6 parts of a 10-3 mol/t copper sulfate aqueous solution (concentration in the system: 1.4
Immediately after adding 10-5 mol/t), the polymerization system became cloudy and polymerization started.

The temperature of the polymerization system was maintained at 70±3°C, and after about 3 hours, when the polymerization rate reached approximately 85%, 90 parts of butyl acrylate,
15 parts styrene, 0 ethylene glycol dimethacrylate
．． 45 parts (0.0 parts of the total of butyl acrylate and styrene)
27 mol%), 1.5 parts of benzoyl peroxide (0.73 mol% of the total of butyl acrylate and styrene) and 1×1
Polymerization was continued by adding 9.0 parts of a 0-1 mol/1 potassium persulfate aqueous solution. Polymerization was complete after about 2 hours. Add 600 parts of a 1.5% calcium chloride aqueous solution to the system to
The resulting polymer was salted out, coagulated, washed with water to remove the catalyst, filtered, and left to dry overnight in a hot air dryer maintained at 70°C to obtain a white powder. The obtained powder was either used as it was or masticated at 180° C. for 5 minutes (Plastograph PL-3000 model manufactured by Brabender) and then press-molded at 230° C. to obtain a sheet and a sample for physical property measurement.
The physical property measurement 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 in accordance with -A-1410, these physical properties showed almost no deterioration even after 300 hours of irradiation with a weather tester. The results are also shown in Table 1. Example 2 Polymerization was carried out in exactly the same manner as in Example 1 except that the polymerization temperature was 82±3°C.

The physical property measurement results are shown in Table 1. Example 3 Polymerization was carried out in exactly the same manner as in Example 1, except that 1.5 parts of lauroyl peroxide (0.44 mol% of the total of butyl acrylate and styrene) was used instead of benzoyl peroxide. Ivy.

The physical property measurement results are shown in Table 1. Example 4 Polymerization was carried out in exactly the same manner as in Example 1, except that 1.5 parts of divinylbenzene was used instead of ethylene glycol dimethacrylate.

The physical property measurement results are shown in Table 1. Comparative Example 1 Polymerization was carried out in exactly the same manner as in Example 1, except that benzoyl peroxide was not used in the example.

The physical property measurement results are shown in Table 1. From the results in Table 1, it is clear that the impact resistance of the methacrylic resin composition according to the present invention is further improved by adding a mastication step, and it is also understood that the composition has sufficient weather resistance.

Claims (1)

[Claims] 1. Production of a hard polymer with controlled molecular weight by heterogeneously polymerizing methyl methacrylate or a monomer mixture containing methyl methacrylate in an aqueous medium in the presence of a molecular weight regulator and without using an emulsifier. An emulsion is prepared, and then, in this emulsion, (a) a monomer which gives a rubbery polymer by polymerization or a monomer mixture mainly composed of the monomer, (b) 0.01 to 0.01 of (a) polyfunctional monomer in an amount of 2 mol% and (c), 0.0 of (a)
A method for producing a methacrylic resin composition, characterized in that polymerization is carried out by adding 5 to 10 mol% of an oil-soluble peroxide.