JPH09227637A - Production of methacrylic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a methacrylic resin having markedly improved water absorptivity and excellent transparency, heat resistance and solvent resistance by radical-polymerizing a mixture comprising a polymethacrylic ester and methacrylic acid in a specified ratio. SOLUTION: A polymerizable mixture comprising 1.0-50wt.% polymethacrylic ester and 99.5-50wt.% methacyclic acid is polymerized in the presence of a radical polymerization initiator. The polymethacrylic ester is particularly desirably a polymethyl methacrylate. Its molecular weight is desirably in the range of 2,000-100,000 (in terms of a number - average molecular weight Mn as determined by gel permeation chromatography(GPC). The polymerization is desirably performed in the bulk.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to transparency, heat resistance,
The present invention relates to a method for producing a methacrylic resin having excellent solvent resistance.

[0002]

BACKGROUND OF THE INVENTION Polymethacrylic acid is known to have a high glass transition point and excellent solvent resistance. In addition, methacrylic acid is
It is used as a copolymerization component with (meth) acrylic acid ester and the like. However, the homopolymer of polymethacrylic acid is water soluble, and the copolymer of methacrylic acid,
Also, the crosslinked polymer of methacrylic acid has problems such as high water absorption.

[0003]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in view of the above-mentioned situation, as a result of radical polymerization initiation of a polymerizable material having a specific composition of methacrylic acid and polymethacrylic acid ester. It has been found that a methacrylic resin having a significantly improved water absorption property and excellent transparency, heat resistance and solvent resistance can be obtained by polymerizing in the presence of an agent, and thus the present invention has been accomplished.

That is, in the present invention, a polymerizable material composed of 1.0 to 50% by weight of polymethacrylic acid ester (a) and 99.0 to 50% by weight of methacrylic acid (b) is added in the presence of a radical polymerization initiator. A method for producing a methacrylic resin is characterized by polymerizing.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the polymethacrylic acid ester (a) used in the present invention include polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polybenzyl methacrylate, polymethallyl methacrylate, and the like. To be Among these, it is preferable to use polymethylmethacrylate.

The molecular weight of the polymethacrylic acid ester (a) used in the present invention is preferably such that the number average molecular weight Mn measured by gel permeation chromatography (GPC) is in the range of 2000 to 100000, and more preferably. It is in the range of 10,000 to 70,000. If the number average molecular weight Mn is too small, the mechanical properties of the obtained methacrylic resin tend to be deteriorated. On the other hand, if the number average molecular weight Mn is too large, it tends to be difficult to uniformly dissolve in methacrylic acid. It is not preferable because it can be seen.

Further, the tacticity of the polymethacrylic acid ester (a) used in the present invention is not particularly limited, but high resolution nuclear magnetic resonance spectrum (NM
The triad ratio (mm) determined in R) is 5 to 100%, and particularly 75 to 100% is preferable because it further reduces the water absorption of the methacrylic resin from which the isotactic polymethacrylic acid ester can be obtained.

The above-mentioned polymethacrylic acid ester (a) used in the present invention can be prepared by a known method such as a solution polymerization method,
It can be produced by a suspension polymerization method, an emulsion polymerization method, a bulk polymerization method, an ionic polymerization method, or the like.

The amount of the polymethacrylic acid ester (a) used is 1.0 to 50% by weight, preferably 5.0 to 30% by weight, in the polymerizable material composed of the polymethacrylic acid ester (a) and the methacrylic acid (b). %. If the amount used is too small, the resulting resin tends to be soluble in water, and if too large, it tends to be difficult to uniformly dissolve in methacrylic acid, which is not preferable.

The amount of methacrylic acid (b) used is 99 to 50% by weight, preferably 95 to 7% by weight in the polymerizable material consisting of polymethacrylic acid ester (a) and methacrylic acid (b).
0% by weight. If the amount used is too small, the polymethacrylic acid ester is difficult to dissolve uniformly, and if the amount used is too large, the resulting resin tends to dissolve in water, which is not preferable.

The methacrylic resin of the present invention can be obtained by polymerizing the above-mentioned polymerizable material comprising polymethacrylic acid ester (a) and methacrylic acid (b) in the presence of a radical polymerization initiator. The polymerization is preferably performed by bulk polymerization. In the polymerization of the polymerizable material, in order to obtain the physical properties aimed at by the present invention, it is preferable to prepare the solution so that it becomes a uniform solution before the polymerization.

The radical polymerization initiator used for the polymerization is, for example, 2,2'-azobisisobutyronitrile,
2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis (4-methoxy-2,4) -Dimethylvaleronitrile), 1,1 '
-Azo compounds such as azobis (cyclohexane-1-carbonitrile), organic peroxides such as benzoyl peroxide and lauryl peroxide, and redox polymerization initiators such as a combination of an organic peroxide and amines Can be used. Moreover, you may use 2 or more types of these initiators.

The amount of radical polymerization initiator used is in the range of 0.01 to 1% by weight based on 100 parts by weight of the polymerizable material. The polymerization temperature is 180 ° C. or lower, preferably 30 to
It is in the range of 140 ° C.

In the present invention, if necessary, an acrylic ester or a polyfunctional (meth) acrylate such as ethylene glycol di (meth) acrylate may be used in combination with the above components (a) and (b). You can

[0015]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto.

[Example 1] 7.5 parts by weight of polymethylmethacrylate having a number average molecular weight Mn of 63000 obtained by radical polymerization and 30 parts by weight of methacrylic acid were placed in a container and stirred, and then 2,2 0.019 parts by weight of'-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 0.038 parts by weight of 1,1'-azobis (cyclohexane-1-carbonitrile) were added and dissolved. This solution was decompressed under reduced pressure, and then poured into a cell that was composed of a gasket and two stainless steel plates and had a thickness of 3 mm, which was set in advance. Then, at 45 ° C for 24 hours (first stage polymerization), then at 120 ° C for 2 hours (second stage polymerization)
Was polymerized to obtain a plate-shaped molded product having a thickness of 3 mm. Table 1 shows the evaluation results of the physical properties of the obtained plate-shaped molded product.

[Embodiment 2] Toluene 106 was dried after the inside of a glass flask equipped with a stirrer was replaced with argon.
After adding 4 ml and cooling to -78 ° C, t-butyl magnesium bromide 0.02 mol, methyl methacrylate 1
The reaction was started by adding 0 mol. And it was made to polymerize at the temperature of -78 degreeC for 197 hours. Then, a methanol solution containing a small amount of hydrochloric acid was added to terminate the polymerization, and the temperature was returned to room temperature. Then, in order to remove the salt of the initiator, the solution was filtered through 5C filter paper and reprecipitated with a large amount of methanol. Then, the polymer was recovered and dried in vacuum at 60 ° C. to obtain a number average molecular weight Mn of 590.
00, polymethyl methacrylate having an isotacticity mm of 91.9% was obtained.

Next, 7.5 parts by weight of this isotactic polymethyl methacrylate and 30 parts by weight of methacrylic acid were placed in a container and stirred, and then 2,2'-azobis (4-methoxy-2,4-) was added thereto. Dimethylvaleronitrile)
0.019 parts by weight and 0.038 parts by weight of 1,1'-azobis (cyclohexane-1-carbonitrile) were added and dissolved. This solution was depressurized under reduced pressure and then polymerized in the same manner as in Example 1 to obtain a plate-shaped molded product having a thickness of 3 mm. Table 1 shows the evaluation results of the physical properties of the obtained plate-shaped molded product.

Comparative Example 1 2,2'-azobis (4-methoxy-2,4) was added to a mixture of 80 parts by weight of methacrylic acid and 0.16 parts by weight of ethylene glycol dimethacrylate.
-Dimethylvaleronitrile) 0.04 parts by weight and 1,1 '
-Azobis (cyclohexane-1-carbonitrile)
0.08 parts by weight was added and dissolved. Next, this solution was depressurized under reduced pressure and then polymerized in the same manner as in Example 1 to obtain a plate-shaped molded product having a thickness of 3 mm. Table 1 shows the evaluation results of the physical properties of the obtained plate-shaped molded product.

COMPARATIVE EXAMPLE 2 A mixture of 7.5 parts by weight of methyl methacrylate and 30 parts by weight of methacrylic acid was added to 2,2 '.
0.019 parts by weight of -azobis (4-methoxy-2,4-dimethylvaleronitrile) and 0.038 parts by weight of 1,1'-azobis (cyclohexane-1-carbonitrile) were added and dissolved. Then, this solution was degassed under reduced pressure, and then polymerized in the same manner as in Example 1 to give a thickness of 3
A plate-shaped molded product of mm was obtained. Table 1 shows the evaluation results of the physical properties of the obtained plate-shaped molded product.

[0021]

[Table 1]

[0022]

The methacrylic resin obtained by the method of the present invention is excellent in transparency, heat resistance and solvent resistance and can be usefully used in various applications, especially in light guide plates.

Claims (1)

[Claims] 1. Polymethacrylic acid ester (a) 1.0
˜50 wt% and methacrylic acid (b) 99.0-50
A method for producing a methacrylic resin, which comprises polymerizing a polymerizable material composed of wt% in the presence of a radical polymerization initiator.