JPH07268044A - Production of thermoplastic resin - Google Patents

Abstract

PURPOSE:To provide a process for producing a thermoplastic resin excellent in transparency and flexibility and having a good moldability by mixing and polymerizing a specific linear polysiloxane and a polymerizable vinyl monomer. CONSTITUTION:A linear polysiloxane in an amount of 100 pts.wt. having an average mol.wt. of 10,000 or higher and comprising 2-20mol% mercaptosiloxane units and 98-80mol% dimethylsiloxane units and 30-2,000 pts.wt. monofunctional polymerizable vinyl monomer component are mixed and subjected to free-radical polymn. Pref. the polysiloxane is used in the form of an aq. emulsion. The monomer component pref. contains 70wt.% or higher alkyl methacrylate. The polymn, is pref. conducted in such a manner that, esp. when the amt. of the monomer component used is not lower than of the polysiloxane, the monomer component is grafted in at least two steps, one step for a vinyl monomer which forms a polymer with a Tg of 20 deg.C or lower and the other for a vinyl monomer which forms a polymer with a Tg of 50 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin, more specifically, it has excellent transparency and flexibility, and
The present invention relates to a method for producing a polysiloxane-containing thermoplastic resin elastomer having good moldability.

[0002]

2. Description of the Related Art Silicone rubber crosslinked with polydimethylsiloxane has excellent heat resistance, flexibility and chemical resistance and is used for various purposes. However, one of the biggest drawbacks of crosslinked silicone rubber is that it cannot be shaped by general injection molding,
In order to improve this point, various thermoplastic elastomers have been conventionally proposed. Most thermoplastic elastomers are block polymers having a polymer component having a glass transition point (Tg) below room temperature, a so-called soft component, and a polymer component having Tg above room temperature, a so-called hard component, in the same molecule. Or, it is a comb-type graft copolymer, but a thermoplastic resin elastomer using polydimethylsiloxane as a soft component has a high manufacturing cost, and is insufficient in moldability, transparency and flexibility. The current situation is that it has not yet been put to practical use.

[0003]

In view of the present situation, the present inventors have completed the present invention as a result of studying to obtain a polysiloxane-based thermoplastic resin elastomer capable of solving the above-mentioned problems. Is a linear polysiloxane (A) having an average molecular weight of 10,000 or more consisting of 2 to 20 mol% of mercapto group-containing siloxane units and 98 to 80 mol% of dimethylsiloxane units, and based on the weight.
This is a method for producing a thermoplastic resin, which comprises mixing 0.3 to 20 times the amount of the monofunctional vinyl polymerizable monomer (B) and performing radical polymerization.

Polysiloxane containing dimethylsiloxane as a main repeating unit used in the practice of the present invention
(A) can be synthesized by using dimethyldichlorosilane, dimethyldialkoxysilane, dimethylsiloxane cyclic oligomer and the like and mercapto group-containing dichlorosilane, mercapto group-containing dialkoxysilane or a condensate thereof as a raw material. It is preferable not to directly use a halogen-containing silane compound such as chlorosilane because it is to obtain a thermoplastic resin having excellent molding processability.

Considering the price of the raw material and the performance of the obtained resin, the most preferable raw material of the polysiloxane (A) used in the present invention is a dimethylsiloxane cyclic oligomer (dimethyl cyclics) and a mercapto group-containing dialkoxysilane or It is the condensate. Condensation of both is a well-known method, for example, water-based emulsion polymerization using dodecylbenzenesulfonic acid as a polymerization catalyst and also as a surfactant,
Alternatively, it may be carried out by bulk polymerization using a strong acid or a strong alkali as a catalyst.

The polysiloxane (A) must contain 2 to 20 mol% of mercapto group-containing siloxane units.
The polymer of vinyl monomer (B) is grafted to polysiloxane (A) via the mercapto group during radical polymerization. Polydimethylsiloxane containing less than 2 mol% of mercapto group-containing siloxane units is used, and vinyl monomer
The transparency of the graft polymer obtained by reacting (B) is poor. Vinyl monomer (B) on polysiloxane containing more than 20 mol% of mercapto group-containing siloxane units
In the graft polymer obtained by reacting with, the resin is significantly deteriorated and discolored due to the mercapto group. The polysiloxane (A) preferably has a mercapto group-containing siloxane unit content of 3 mol% or more and 10 mol% or less. A preferable example of the mercapto group-containing silane compound is γ-mercaptopropylmethyldimethoxysilane.

The average molecular weight of polysiloxane (A) is 10,000
The resin obtained by using the polysiloxane having a molecular weight of less than 10,000 has a reduced flexibility or strength. Preferably polysiloxane
The average molecular weight of (A) is 30,000 or more. However, since a remarkably high molecular weight polysiloxane lowers the fluidity of the obtained resin, it is more preferable to seal the end of the polysiloxane with an inert group such as a trimethylsilyl group so that the molecular weight is 300,000 or less.

The amount of the vinyl polymerizable monomer (B) to be graft-polymerized on the polysiloxane (A) must be 0.3 to 10 times the weight of the polysiloxane (A) based on the weight. Polysiloxane (A) of vinyl polymerizable monomer (B)
If the graft amount is less than 0.3 times, the mechanical strength of the obtained resin is extremely low, and its injection molding becomes impossible. Vinyl polymerizable monomer for polysiloxane (A)
If the graft amount of (B) exceeds 20 times, it will be difficult to maintain the flexibility of the obtained resin. Preferably, the grafting amount of vinyl polymerizable monomer (B) is based on polysiloxane (A).
It is 0.6 times or more and 10 times or less.

In order to carry out the graft polymerization of the polysiloxane (A) and the vinyl monomer (B) easily and efficiently, it is preferable to use the polysiloxane (A) emulsified and dispersed in water. . Graft polymerization of both of them in the state of being emulsified and dispersed in water has an advantage that they can be carried out at a low temperature, a low stirring torque, or without a solvent, as compared with their bulk polymerization or solution polymerization. The emulsified and dispersed polysiloxane can be prepared by a well-known method, but from the viewpoint of economical efficiency, a method of emulsion polymerization using a cyclic dimethylsiloxane oligomer as a raw material and an acidic emulsifier is preferable. Since the emulsion of the siloxane polymer polymerized in the presence of the acidic emulsifier exhibits strong acidity, it is necessary to neutralize the emulsion after the completion of the siloxane polymerization.

As the radical polymerization initiator used in the subsequent emulsion graft polymerization of the polysiloxane (A) and the vinyl polymerizable monomer (B), known ones used in the emulsion radical polymerization can be used. The method of charging the vinyl-polymerizable monomer (B) is not particularly limited, but in order to more efficiently proceed the graft copolymerization with the graft active site in the siloxane polymer (A), the siloxane should be previously added to the polymerization initiator. Polymer
It is preferable that the emulsion of (A) and at least a part of the vinyl polymerizable monomer (B) are well mixed to impregnate the siloxane polymer particles with the vinyl polymerizable monomer.

Examples of the vinyl polymerizable monomer (B) include alkyl methacrylate, alkyl acrylate, styrene, styrene derivative, acrylonitrile and the like. The vinyl polymerizable monomer (B) may be used as a mixture of two or more kinds, but in order to obtain a thermoplastic resin having excellent appearance and weather resistance, alkyl methacrylate is used as the vinyl polymerizable monomer (B). It is preferable to use at a ratio of 70% by weight or more based on the total amount of Among the alkyl methacrylates, particularly preferred examples include methyl methacrylate, ethyl methacrylate and cyclohexyl methacrylate.

Polysiloxane of vinyl polymerizable monomer (B)
Graft polymerization to (A) can also be carried out in two or more stages, especially when the amount of vinyl polymerizable monomer (B) used is at least 1 time that of the siloxane polymer (A). Vinyl monomers that can form polymers with Tg of 20 ° C or less
(B) and the vinyl monomer (B) capable of forming a polymer having a Tg of 50 ° C. or higher are preferably graft polymerized in at least two stages, and a vinyl polymer having a low Tg is added to the resin of the present invention. By introducing coalescence, the flexibility of the resin becomes good.

Hereinafter, the present invention will be described in more detail with reference to Examples. All "parts" in the examples are parts by weight.

[0014]

Example 1 90 parts of dimethyl cyclics (mixture of cyclic dimethyl siloxane oligomer 3 to 7 mer), 10 parts of graft crossing agent (γ-mercaptopropylmethyldimethoxysilane), end capping agent (hexamethyldisiloxane) 0.
After preliminarily mixing 05 parts, 300 parts of water, and 0.5 part of sodium dodecylbenzenesulfonate with a homomixer,
It was sheared with a homogenizer at a pressure of 200 kg / cm ² and forcedly emulsified to prepare a silicon raw material emulsion. Water 100
Parts and 10 parts of dodecylbenzenesulfonic acid are charged into a flask equipped with a stirrer, a condenser, a heating jacket, and a dropping pump, and the above silicon raw material emulsion is further injected to maintain the temperature in the flask at 80 to 90 ° C. Polymerization was carried out for a time.

Cooling the resulting emulsion to room temperature,
Neutralization with sodium hydroxide gave a silicone polymer emulsion. The obtained silicone polymer emulsion was placed in a flask equipped with a stirrer, a condenser, a heating jacket, and an inert gas inlet, and 78 parts of methyl methacrylate (MMA) as a vinyl-polymerizable monomer (B) under a nitrogen atmosphere and acryl. Methyl acid (MA) 2 parts and t-butyl hydroperoxide (T
BH) 0.4% (relative to monomer) was added and stirred for 10 minutes. Then, the temperature was raised to 60 ° C., 30 ppm of EDTA, 6,000 ppm of Rongalit and 10 ppm of ferrous oxide were added to initiate radical polymerization. After 1 hour, the temperature was raised to 75 ° C, and after 1 hour, the temperature was raised to 90 ° C, and the polymerization was terminated when a total of 3 hours had elapsed. Methanol was poured into the obtained emulsion to collect and collect the polymer, which was dried, pelletized, and then injection-molded to obtain a dumbbell test piece for a tensile test. The test piece was transparent and had a tensile elongation of 80%.

[0016]

Example 2 In Example 1, graft polymerization of vinyl monomer (B) with respect to polysiloxane (A) was carried out by radical polymerization of 80 parts of butyl acrylate at 60 ° C. for 1 hour.
Then, a thermoplastic resin was obtained in the same manner as in Example 1 except that 120 parts of MMA was radically polymerized at 60 ° C. to 90 ° C. for 3 hours, and a test piece was obtained from this resin. The test piece was transparent and had a tensile elongation of 100% or more.

[0017]

Comparative Example 1 A thermoplastic resin was obtained in the same manner as in Example 1 except that the amount of the graft crossing agent (γ-mercaptopropylmethyldimethoxysilane) used was 2 parts, and a test piece was obtained from this resin. . The test piece was opaque.

[0018]

[Comparative Example 2] MMA 19.5 as vinyl polymerizable monomer (B)
Parts and MA 0.5 parts were used, and a thermoplastic resin was obtained in the same manner as in Example 1. The obtained resin was a viscous liquid at room temperature and could not be molded.

[0019]

INDUSTRIAL APPLICABILITY The thermoplastic resin obtained by the production method of the present invention can be used as a thermoplastic elastomer having a high degree of flexibility and has a transparent appearance, so that it can be used for various purposes. Further, the production method of the present invention is extremely useful as a method for producing a polysiloxane-containing transparent thermoplastic elastomer at low cost.

Claims (4)

[Claims] 1. A mercapto group-containing siloxane unit 2 to 20
Linear polysiloxane (A) having an average molecular weight of 10,000 or more consisting of mol% and dimethylsiloxane unit of 98 to 80 mol%
And a monofunctional vinyl-polymerizable monomer (B) in an amount of 0.3 to 20 times based on the weight, and radical polymerization is carried out to carry out radical polymerization. 2. The method for producing a thermoplastic resin according to claim 1, wherein the polysiloxane (A) is emulsified and dispersed in water. 3. The method for producing a thermoplastic resin according to claim 1, wherein at least 70% by weight of a vinyl monomer composed of alkyl methacrylate is used as the vinyl polymerizable monomer (B). 4. A method in which radical polymerization is carried out in two steps, one of which is mainly composed of a vinyl monomer (B) having a Tg of 20 ° C. or less of the resulting vinyl polymer. The method for producing a thermoplastic resin according to claim 1, wherein the other polymer is obtained by using the vinyl monomer (B) having a Tg of 50 ° C. or higher.