JPH08283359A - Graft copolymer and thermoplastic resin composition - Google Patents

Abstract

PURPOSE: To obtain a methacrylic resin having improved impact resistance and high transparency by grafting methyl methacrylate onto a specified silicone copolymer rubber. CONSTITUTION: This copolymer is prepared by grafting 10-500 pts.wt. monomer mixture containing 80wt.% or above methyl methacrylate onto 100 pts.wt. copolymer rubber comprising 0.05-25 pts.wt. polyorganosiloxane containing 0.1mol% or above siloxane units having a vinyl-polymerizable functional group, and 99.95-75 pts.wt. at least one vinyl-polymerizable monomer selected from among an aromatic vinyl compound, an unsaturated carboxylic acid ester and butadiene, and having a particle diameter of 0.05-0.5μm. In order that the resin may be transparent it is desirable that the content of the polyorgano-siloxane in the copolymer rubber is 10wt.% or below. In order that the resin may have particularly good transparency, it is desirable that this content is 2wt.% or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graft copolymer which improves the impact resistance of an acrylic resin and a resin composition having excellent impact resistance.

[0002]

2. Description of the Related Art Acrylic resin is a molding material having excellent transparency and weather resistance and a beautiful appearance, but has a drawback of low impact resistance represented by the impact strength of a notched test piece. Conventionally, it has been generally practiced to reinforce a hard resin with an elastic body to provide impact resistance.
Resins are typical of this type of resin, but since diene rubber is used as the elastic component, the weather resistance is poor,
A major drawback is limited outdoor use. For this reason, various proposals have been made to prepare an impact resistant resin having weather resistance by using a rubber other than a diene rubber as an elastic body. The use of acrylic ester type rubber is one example of this, and many studies have been made so far.

Further, as a non-diene rubber source having good weather resistance, silicone rubber typified by polydimethylsiloxane can be mentioned. However, when silicone rubber is used, the transparency of the resin and the coloring property of the pigment are deteriorated. Known to be.

[0004]

Since the effect of improving the impact resistance of acrylic acid ester rubber is smaller than that of diene rubber, the use of methyl methacrylate resin containing acrylic acid ester rubber is limited. It was

Attempts have also been made to improve the performance of acrylic rubber, in which the so-called hard core type impact resistance is improved by using fine particles of hard resin as the core, acrylic rubber as the outer layer, and acrylic resin as the outermost layer. It is known that the substance has improved impact resistance as compared with the usual acrylic rubber. However, in the hard core type modifier, there remains a problem that the transparency is slightly inferior.

Further, it is difficult to achieve both transparency and impact resistance when a silicone-containing rubber is added to a methacrylic resin. For example, in JP-A-6-25492, the pigment coloring of the silicone-containing rubber is improved. In order to achieve this, it has been proposed to use a silicone-based graft composite rubber having a particle size of 0.01 to 0.07 μm.
Although it discloses that impact strength can be improved without significantly reducing the pigment coloring of styrene copolymer or polymethylmethacrylate, it is possible to maintain high transparency of acrylic resin and high impact resistance of acrylic resin. No specific method for applying is given.

[0007]

As a result of intensive studies in view of the present situation, the present inventors have found that a graft copolymer of a copolymer rubber having a specific composition and a specific particle size improves the impact resistance of an acrylic resin. The present invention has been accomplished by finding that it is a modifier that achieves high transparency and high transparency.

That is, the gist of the present invention is 0.05 to 25% by weight of a polyorganosiloxane containing 0.1 mol% or more of a siloxane unit having a vinyl polymerizable functional group, an aromatic vinyl compound, an unsaturated carboxylic acid, 99.95 to 75% by weight of at least one vinyl polymerizable monomer selected from unsaturated carboxylic acid ester and butadiene
(Total 100% by weight) and has a particle size of 0.05 to
Graft copolymer obtained by graft-polymerizing 10 to 500 parts by weight of a monomer containing 80% by weight or more of methyl methacrylate (based on 100 parts by weight of the copolymer) onto a copolymer rubber having a thickness of 0.5 μm. And a thermoplastic resin composition comprising the graft copolymer and an acrylic resin containing 80% by weight or more of methyl methacrylate.

The graft copolymer of the present invention comprises a copolymer rubber component and a graft component containing methyl methacrylate as a main component.

The copolymer rubber needs to contain polyorganosiloxane in an amount of 0.05% by weight or more, and when the content of the polyorganosiloxane is less than 0.05% by weight, a significant resistance is obtained as compared with the acrylic rubber alone. Impact improvement effect cannot be obtained. The content of polyorganosiloxane in the copolymer rubber must be 25% by weight or less.
If it exceeds, the transparency of the resin is impaired. In addition, it is not preferable to include a large amount of relatively expensive polyorganosiloxane from the economical viewpoint.

In order to achieve the effect of improving impact resistance,
The amount of polyorganosiloxane contained in the copolymer rubber is preferably 0.1% by weight or more, and more preferably 0.2% by weight or more in order to obtain a remarkable effect.

In order to maintain the transparency of the resin, the amount of polyorganosiloxane contained in the copolymer rubber is 10% by weight.
It is preferably not more than 2%, more preferably not more than 2% by weight in order to achieve particularly good transparency.
If the polyorganosiloxane content is less than 2% by weight,
Transparency comparable to conventional acrylic rubber is achieved.

The component other than the polyorganosiloxane constituting the copolymer rubber is at least one vinyl polymerizable monomer 99 selected from aromatic vinyl compounds, unsaturated carboxylic acids, unsaturated carboxylic acid esters and butadiene. ．
A polymer obtained by radical copolymerization of 9 to 75% by weight (total 100% by weight with the polyorganosiloxane component) may be used, but the content of the butadiene component is small in order to keep good weather resistance. It is more preferable, and it is most preferable that there is no butadiene component.

Examples of preferred aromatic vinyl compounds include styrene and α-methylstyrene. Preferred examples of unsaturated carboxylic acids and unsaturated carboxylic acid esters are acrylic acid, methacrylic acid and alkyl having 1 to 12 carbon atoms. Mention may be made of acrylic acid esters and methacrylic acid esters having esters. Furthermore, it is preferable to copolymerize a polyfunctional vinyl compound such as di (meth) acrylate of a diol having 2 to 6 carbon atoms in an amount of 0.1 to 5% by weight with respect to these monomer components and allyl methacrylate.

From the viewpoint of improving the impact strength, the particle diameter of the rubber layer must be 0.05 μm or more.
If it is less than μm, good impact strength cannot be obtained. The particle diameter of the rubber layer is preferably 0.08 μm or more. When the particle size of the rubber layer is 0.08 μm or more, the effect of improving the impact strength becomes remarkable. Most preferably, the particle diameter of the rubber layer is 0.12 μm or more, and at this time, the greatest effect of improving impact strength is obtained.

In order to keep the transparency of the resin good, the particle diameter of the rubber layer needs to be 0.5 μm or less. If the particle diameter of the rubber layer exceeds 0.5 μm, the resin becomes opaque.

Preferably, the rubber layer has a particle size of 0.25 μm.
Below, at this time, it becomes easy to maintain the high transparency inherent in the acrylic resin. The vinyl-polymerizable functional group contained in the polyorganosiloxane may be any as long as it can be copolymerized with the vinyl monomer at the time of polymerization, but preferred examples include methacryloyl group, vinyl group and vinylphenyl group. Is mentioned.

For example, a polyorganosiloxane containing a methacryloyl group can be obtained by emulsion copolymerization of γ-methacryloyloxypropylmethyldimethoxysilane and cyclic dimethylsiloxane.

The amount of the vinyl-polymerizable functional group contained in the polyorganosiloxane must be 0.1 mol% or more based on the siloxane unit. If it is less than 0.1 mol%, the resin becomes opaque. Or the effect of improving impact strength may not be sufficient. The amount of the vinyl-polymerizable functional group contained in the polyorganosiloxane is preferably 0.5 mol% or more, and at this time, the effect of improving the transparency and impact strength of the resin becomes remarkable. Furthermore, the amount of vinyl polymerizable functional group contained in the polyorganosiloxane is 5
It is preferably not more than mol%. If it is 5 mol% or more, the effect of improving impact strength may decrease. It is more preferably 3 mol% or less. The most preferred amount of vinyl polymerizable functional group contained in the polyorganosiloxane is 0.5 to 3 mol%. At this time, a high degree of transparency retention of the acrylic resin and a remarkable improvement in impact strength are simultaneously achieved.

Although the reason is not clear, it is preferable that the branched component in the polysiloxane is small, and the branched component having 3 or more siloxane bonds on one silicon atom is preferably 3 mol% or less. If it is 3 mol% or more, the impact strength tends to be slightly impaired. More preferably, it is 1 mol% or less, and at this time, a larger impact strength improving effect can be obtained.

It is necessary that the monomer used for the graft polymerization contains 80% by weight or more of methyl methacrylate, and when it contains less than 80% by weight of methyl methacrylate, the compatibility with the acrylic resin is lowered and it is favorable. The effect of improving impact strength cannot be obtained. Examples of the copolymerization component of 20% or less include acrylic acid esters such as methyl acrylate and ethyl acrylate, methacrylic acid esters such as ethyl methacrylate, and styrene.

The monomer to be grafted needs to be 10 parts by weight or more and 500 parts by weight or less when the copolymer rubber is 100 parts by weight, and when it is less than 10 parts by weight, the compatibility with the acrylic resin is low. If it exceeds 500 parts by weight, the effect of improving the impact strength cannot be obtained because it is insufficient, and if it exceeds 500 parts by weight, the effect of improving the impact strength becomes too low, which is not practical.

Preferably, the graft layer is a copolymer rubber 1
It is 30 parts by weight or more and 150 parts by weight or less with respect to 00 parts by weight, and most preferably 45 parts by weight or more and 100 parts by weight or less. In the most preferable range, it becomes easy to keep the impact strength, transparency, fluidity, etc. of the acrylic resin at good levels.

The refractive index of the rubber layer and the graft layer can be matched with the refractive index of the acrylic resin by adjusting the amount ratio of the monomer components used according to a known method.

The polymer of the present invention, when added to an acrylic resin containing methyl methacrylate as a main component, imparts a high degree of impact resistance while maintaining its transparency.

The acrylic resin used in the present invention is usually 8
It contains 0% by weight or more of methyl methacrylate, and various vinyl monomer monomers can be copolymerized in the range of less than 20% by weight. For example, an aromatic alkenyl monomer, a vinyl cyan monomer, etc. can be mentioned.

The amount of the graft copolymer added to the acrylic resin is preferably 10 to 90% by weight, but more preferably 15 to 60 in consideration of the elastic modulus and fluidity of the resin.
% By weight.

[0028]

The present invention will be described in more detail with reference to the following examples. In each description, "part" means "part by weight".

Example 1 <Production of Silicone Emulsion> (a) Cyclic dimethylsiloxane oligomer 95 parts (b) Methacryloxypropylmethyldimethoxysilane 5 parts (1.5 mol%) (c) Sodium dodecylbenzene sulfonate 0 0.7 parts (d) 310 parts of water was emulsified with a homogenizer to obtain a pre-emulsion.

Then, (e) 30 parts of dodecylbenzenesulfonic acid (f) 90 parts of water were charged into a reaction vessel equipped with a stirrer and a reflux condenser,
Heated to 90 ° C.

Then, the pre-emulsion was added dropwise to this reaction vessel over 4 hours.

After completion of dropping, heating and stirring are continued for another hour,
Then, the reaction solution was cooled and neutralized to obtain Silicone emulsion A-1.

<Production of Silicone-Acrylic Composite Rubber> (g) 5 parts of silicone emulsion (A-1) (including 1 part of silicone polymer component) and (h) 311 parts of water are introduced into a nitrogen gas introducing tube, a stirrer and a reflux cooling tube. Into a reaction vessel equipped with, 0.0004 parts of ferrous sulfate, EDTA
0.012 parts and Rongalit 0.48 parts were added, and after nitrogen gas purging, the mixture was heated to 60 ° C.

(I) 0.05 part of sodium ether phosphate (LO-529 manufactured by Toho Kagaku) was added thereto, and then butyl acrylate 79.7 parts styrene 19.3 parts allyl methacrylate 0.9 parts polyoxyethylene alkyl Sodium phenyl ether phosphate (LO-529 manufactured by Toho Kagaku Co., Ltd.) 1 part A mixture of 0.3 part of t-butyl hydroperoxide was added dropwise over 3 hours, and the mixture was further heated and stirred for 1 hour to obtain a silicone-acrylic composite rubber emulsion. It was

The average particle size of the obtained emulsion was 0.
It was 12 μm.

<PMM for silicone-acrylic composite rubber
A-graft> 400 parts of the above silicone-acryl composite rubber emulsion was placed in the above reaction vessel, and was continuously methyl methacrylate 57 parts Methyl acrylate 3 parts Octyl mercaptan 0.25 parts LO-529 0.4 parts t-butyl hydroperoxide. 0.15 parts of the mixture was added dropwise over 1.5 hours, and the mixture was further heated and stirred for 1 hour. Then, the obtained multistage polymer was coagulated, collected and dried.

<Blend with Acrylic Resin> 40 parts of the obtained polymer powder and 60 parts of methacrylic resin (Acrypet VH) were melt-kneaded by an extruder, pelletized and then injection-molded to obtain a bending test and impact resistance. A test piece for a sex test and a total light transmittance measurement was obtained.

The evaluation results are shown in Table 1.

[0039]

[Table 1]

(Examples 2 to 4) With the composition as shown in Table 2,
Polymerization and molding evaluation were performed in the same manner as in Example 1 except that the content of the silicone component and the particle size of the composite rubber were changed as shown in Table 1. The results are shown in Table 1.

[0041]

[Table 2]

(Comparative Example 1) Polymerization and molding evaluation were carried out in the same manner as in Example 1 except that the amount of siloxane polymer used was 0 part and the charging composition shown in Table 2 was used. The results are shown in Table 1. (Comparative Example 2) With the composition of Table 2, the particle size of the composite rubber was 0.
Polymerization and molding evaluation were performed in the same manner as in Example 1 except that the thickness was 04 μm. The results are shown in Table 1.

[0043]

EFFECT OF THE INVENTION According to the present invention, an impact resistance modifier capable of significantly improving impact resistance while maintaining excellent transparency of acrylic resin can be obtained.

Claims (2)

[Claims] 1. 0.05 to 25 parts by weight of a polyorganosiloxane containing 0.1 mol% or more of a siloxane unit having a vinyl polymerizable functional group, and an aromatic vinyl compound,
At least one vinyl polymerizable monomer selected from unsaturated carboxylic acid, unsaturated carboxylic acid ester and butadiene is composed of 99.95 to 75 parts by weight (total 100 parts by weight) and has a particle diameter of 0.05 to 0. A graft copolymer obtained by graft-polymerizing 10 to 500 parts by weight of a monomer containing 80% by weight or more of methyl methacrylate (based on 100 parts by weight of the copolymer) to a copolymer rubber having a size of 0.5 μm. 2. The graft copolymer according to claim 1 and 80.
A thermoplastic resin composition comprising an acrylic resin containing methyl methacrylate in an amount of at least% by weight.