JP2752461B2 - Manufacturing method of thermoplastic resin with high haze - Google Patents

Description

BACKGROUND OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a thermoplastic resin having a high haze and exhibiting a so-called ground glass-like appearance. The thermoplastic resin having a ground glass appearance can be widely used for cosmetic containers, beverage containers, lighting equipment and the like.

In this specification, the term "ground glass" refers to a property of scattering and transmitting incident linear light, such as ground glass and opal glass.

<Conventional technology> Conventionally, as a method for producing a thermoplastic resin having a ground glass-like appearance or a molded product thereof, a mold is subjected to satin finish,
A method of forming a ground glass surface on a molded article, a method of using a resin composition mixed with a filler, and the like are known.

However, in the method in which the mold is subjected to satin finish, the mold is expensive, and the gloss of the surface of the molded product is low, so that the applicable range is limited. Furthermore, if the same mold is used for a long period of time, the matte pattern on the mold surface is gradually worn, and the molded article loses its ground glass-like appearance. Further, in the method using a resin composition mixed with a filler, it has been difficult to obtain a resin composition having a good balance of physical properties.

Thus, the present inventors have already proposed one proposal as a method for producing a thermoplastic resin having a ground glass-like appearance having an excellent surface gloss and a good balance of physical properties by solving the above-mentioned problems of the prior art. did. That is, in a method for producing a styrene resin by polymerizing a monomer mixture of styrene or a styrene monomer and a vinyl cyanide monomer, the other styrene resin having a low compatibility with the styrene resin. Is dissolved in the above monomer or monomer mixture and then polymerized (JP-A-58-98310).

[Summary of the Invention]

<Problems to be Solved by the Invention> However, the above-mentioned production method (Japanese Patent Application Laid-Open No. 58-9813) has a uniform ground glass-like appearance and physical properties such as rigidity, moldability and colorability. Quality) Although effective as a method for producing a thermoplastic resin with a good balance,
In a separate polymerization step, it was necessary to prepare a styrene resin having low compatibility with the matrix resin in advance and dissolve it in a specific monomer.

<Means for Solving the Problems> In order to solve the above problems, the present inventors have conducted intensive studies and found that a polymer syrup obtained by bulk polymerization of an aromatic vinyl monomer and having a weight average molecular weight of more than 350,000 was obtained. A vinyl cyanide monomer is added to the first step of the production (polymerization step (1)) and the syrup obtained in this step, and a copolymer having low compatibility with the polymer in the syrup is formed by bulk polymerization. The second step (polymerization step (2)) of dispersing the polymer produced in the polymerization step (1) in the form of fine particles in an unpolymerized monomer solution of the copolymer, and further continuing the polymerization to complete the reaction According to the production method comprising the third step (polymerization step (3)), a thermoplastic resin exhibiting a uniform ground glass-like appearance and having a good balance of physical properties (quality) such as rigidity, moldability and colorability can be obtained. I found that I got it.

That is, the method for producing a thermoplastic resin having a high haze according to the present invention comprises subjecting an aromatic vinyl monomer and a vinyl cyanide monomer to the following polymerization steps (1), (2) and (3). It is characterized by the following.

Polymerization Step (1) A step of subjecting an aromatic vinyl monomer to bulk polymerization to obtain a syrup composed of an unpolymerized monomer solution of a produced polymer having a weight average molecular weight of more than 350,000.

Polymerization step (2) A vinyl cyanide monomer is added to the syrup and polymerization is continued to form an unpolymerized monomer solution of the produced polymer, and the polymer produced in the polymerization step (1) is added to the solution. A step of obtaining a syrup dispersed in fine particles therein.

Polymerization Step (3) A step of continuing the polymerization of the syrup in the polymerization step (2) to obtain a thermoplastic resin.

<Effects of the present invention> According to the present invention, a thermoplastic resin having a uniform ground glass-like appearance by a series of manufacturing steps and having a good balance of physical properties (quality) such as rigidity, moldability and coloring property is obtained. Obtainable.

The thermoplastic resin obtained by the present invention has a ground glass appearance and a total light transmittance (ASTM D-1003).
) Is hardly reduced. Further, during the forming process, it did not peel off in a layer form, and no deterioration in physical properties such as impact strength was observed.

[Specific description of the invention]

The thermoplastic resin composition according to the present invention consists essentially of a vinyl monomer and a vinyl cyanide monomer,
In addition, this composition should be a polymerization step (1) of forming a polymer of an aromatic vinyl monomer to be a “reflecting material” as a solution in an unpolymerized monomer, and should be a matrix of the thermoplastic resin. The polymerization step (2) for forming a copolymer of the aromatic vinyl monomer and the vinyl cyanide monomer and precipitating the dissolved polymer of the polymerization step (1), and the polymerization are further continued. And complete polymerization step (3).

<Monomer> As the aromatic vinyl monomer, side chain (and / or) nucleus-substituted or unsubstituted styrene or vinylnaphthalene can be generally used. In this case, the substituent includes a lower alkyl (for example, a C ₁ -C ₄ alkyl group or a methyl group), a halogen atom (for example, a chlorine atom), a trifluoromethyl group, and the like. Specific examples include styrene, o-methylstyrene, m-methylstyrene, p
-Methylstyrene, α-methylstyrene, t-butylstyrene, p-ethylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and the like. Styrene is particularly preferred.

On the other hand, specific examples of the vinyl cyanide monomer include acrylonitrile and methacrylonitrile. Acrylonitrile is particularly preferred.

The thermoplastic resin composition according to the present invention contains these two types of monomers as essential components. In addition to the body, these copolymerizable further comonomers (which may be diene or triene in small amounts) can be used in combination (the invention is intended to include , So understand).
A specific example of such an "optional" monomer is a lower alkyl ester of acrylic or methacrylic acid, such as methyl methacrylate.

<Polymerization Step (1)> In this step, the aromatic vinyl monomer is subjected to bulk polymerization,
This is a step of obtaining a syrup composed of an unpolymerized monomer solution of the produced polymer.

The bulk polymerization here is preferably thermal polymerization, but may be polymerization using a commonly used radical initiator.

The weight average molecular weight of the produced polymer obtained in this polymerization step is 350,000 or more, preferably in the range of 400,000 to 2,000,000 in terms of polystyrene equivalent weight average molecular weight measured by GPC method (gel permeation chromatography). It is. When the weight-average molecular weight is less than 350,000, the final thermoplastic resin obtained does not have a ground glass-like appearance, or even if it has a ground glass-like appearance, it becomes uneven and unsuitable.

It falls within the range of 0.05 to 20% by weight, preferably 0.1 to 15% by weight, particularly preferably 0.2 to 10% by weight based on the total weight of the aromatic vinyl monomer and vinyl cyanide monomer obtained in this polymerization step. It is desirable to be controlled as follows. If it is less than the above range, the effect of sintering the final thermoplastic resin obtained is insufficient, and if it exceeds the above range,
It is not preferable because a phenomenon occurs in which the thermoplastic resin peels off in a layered form during molding.

<Polymerization Step (2)> In this step, a vinyl cyanide monomer is added to the syrup obtained in the polymerization step (1), and polymerization is continued with stirring to form a matrix of the resin composition of the present invention. This is a step of obtaining an aromatic vinyl monomer-vinyl cyanide monomer copolymer as a solution in an unpolymerized monomer, that is, a syrup. This step is, in addition, a polymerization step (1).
The purpose of the present invention is to precipitate the dissolved polymer in the syrup into fine particles in the second syrup.

The amount of the vinyl cyanide monomer added in this polymerization step is 1: 9 to 9: 1 by weight based on the unpolymerized aromatic vinyl monomer of the syrup obtained in the previous polymerization step (1). , Especially
It is preferably 2: 8 to 8: 2. If the amount of the aromatic vinyl monomer is less than 1: 9, the thermal stability of the final thermoplastic resin obtained is deteriorated, which is not suitable. On the other hand, if the amount of the aromatic vinyl monomer is more than 9: 1, the compatibility between the polymer produced in the polymerization step (1) and the copolymer produced in this step becomes large, and the final heat The appearance of the plastic resin does not become ground glass.

The polymerization method is preferably bulk polymerization or suspension polymerization, particularly preferably bulk polymerization, and may be thermal polymerization or bulk polymerization using a commonly used radical initiator. In the polymerization, the mixture is sufficiently stirred so that the polymer of the aromatic vinyl monomer dissolved in the monomer or the monomer mixture is averaged in the unpolymerized monomer solution of the copolymer formed in this step. Particle size 0.5 ~ 20
μm, preferably 1 to 10 μm. In order for the final thermoplastic resin to have a good ground glass appearance, it is preferable that the polymer produced in the polymerization step (1) is dispersed as particles having the above-mentioned particle size range.

<Polymerization Step (3)> In this step, polymerization of the syrup obtained in the previous polymerization step (2) is continued to obtain a final thermoplastic resin.

In this step, the polymerization step (1) is performed in the previous polymerization step (2).
The syrup composed of a copolymerized monomer solution of a copolymer in which the produced polymer is dispersed in the form of fine particles is substantially completely polymerized by a bulk polymerization method or a suspension polymerization method to obtain a final thermoplastic resin. . In this step, unreacted monomers can be removed from the polymer by a devolatilizer or a stripping operation, and recovered.

(Experimental example)

The following experimental examples further illustrate the present invention. The present invention is not limited at all by these experimental examples.

Example 1 1200 g of styrene was charged into a pressure-resistant reactor having a content of 5 liters equipped with a stirring blade, and stirred at 95 ° C. under a nitrogen atmosphere.
The temperature was raised to 95 ° C., and bulk polymerization was performed at 95 ° C. for 4 hours (polymerization step (1)). At this point, the syrup was sampled and analyzed and found to contain 6% by weight polystyrene.

Subsequently, 600 g of acrylonitrile, 0.9 g of ditertiary butyl peroxide and 0.3 g of tertiary butyl peracetate were added to the syrup, and bulk polymerization was carried out at 100 ° C. for 4 hours (polymerization step (2)). At this time, 100 ℃ /
After reaction for 2 hours, 13 g of terpene oil as a chain transfer agent
Was added. After 4 hours of reaction, the syrup had a solids content of 2
As a result of observation with a phase contrast microscope, it was found that the polystyrene phase was dispersed as spherical particles of about 6 μm.

Then, 1.5 g of a polyvinyl alcohol suspension and a polyacrylate suspension were added as suspensions to the syrup.
After adding 1.5 g and 15 g of sodium sulfate to suspend the system, suspension polymerization was performed at 120 ° C. for 1 hour and further at 130 ° C. for 3 hours (polymerization step (3)). The temperature was further raised to 150 ° C., and after stopping for 1 hour, the resultant was cooled to separate the produced polymer.

After the obtained bead-like polymer was dehydrated and dried, it was pelletized by an extruder, and a test piece was prepared by injection molding. Using this test piece, total light transmittance and haze (Haze) were measured by ASTM D-1003. The results were as shown in Table 1. Flexural modulus and Izod (Iz
od) Each of the impact strengths showed the same value as that of a commercially available AS resin (“Sanrex SAN-C” manufactured by Mitsubishi Monsanto Kasei Co., Ltd.).

In the test of the molded product, no delamination was observed.

Example 2 A ground glassy styrene resin was produced in the same manner as in Example 1 except that the polymerization of polystyrene in the polymerization step (1) was changed to 95 ° C for 2 hours. The polystyrene content in the syrup at the end of the polymerization step (1) was 3.1% by weight.
Met.

The flexural modulus and Izod impact strength of the finally obtained resin were the same as those of a commercially available AS resin (Mitsubishi Monsanto Kasei Co., Ltd. "Sunlex SAN-C"). No delamination was observed in the test of the molded product. The measurement results of the total light transmittance and the haze were as shown in Table 1.

Example 3 Polymerization of polystyrene in the polymerization step (1) was performed at 105 ° C.
A ground glass-like adsorption resin was produced in the same manner as in Example 1 except that the time was changed to 1 hour. The polystyrene content in the syrup at the end of the polymerization step (1) was 4.8% by weight.

The bending elastic modulus and Izod impact strength of the finally obtained resin were hardly reduced, and no delamination was observed in the test of the molded product.

Comparative Example 1 5 wt% of polystyrene was added to a commercially available AS resin (Mitsubishi Sunmont Chemical Co., Ltd. "Sunrex SAN-C") and kneaded. The obtained composition was exfoliated in layers. The total light transmittance and other physical properties were not measured.

Comparative Example 2 The reactor used in Example 1 was charged with 1200 g of styrene,
Further, after adding 1.2 g of ditertiary butyl peroxide and 0.6 g of tertiary decyl mercaptan as a chain transfer agent, the temperature was raised to 115 ° C. while stirring under an atmosphere, and bulk polymerization was performed at 115 ° C. for 30 minutes (polymerization). Step (1)). At this point, the syrup was sampled and analyzed to contain 7.1% by weight polystyrene.

Subsequently, 600 g of acrylonitrile and 0.2 g of tert-butyl peracetate were added to the syrup, and the mixture was heated to 100 ° C.
For 4 hours (polymerization step (2)). At this time, 10 g of terpene oil was added as a chain transfer agent at a point after the reaction at 100 ° C. for 2 hours. After the reaction for 4 hours, the solid content of the syrup was 30.5% by weight, and the polystyrene phase was observed by a phase-contrast microscope, and as a result, was found to be dispersed as spherical particles of about 5 μm.

Then, 1.5 g of a polyvinyl alcohol suspension and a polyacrylate suspension were added as suspensions to the syrup.
After adding 1.5 g and 15 g of sodium sulfate to suspend the system, suspension polymerization was performed at 120 ° C. for 1 hour and then at 130 ° C. for 3 hours (polymerization step (3)). Thereafter, the temperature is raised to 150 ° C,
After stripping for 1 hour, the mixture was cooled to separate the produced polymer. The obtained bead-like polymer was pelletized in the same manner as in Example 1 and molded and evaluated. The total light transmittance and haze were as shown in Table 1. Both the flexural modulus and the Izod impact strength showed the same values as those of a commercially available AS resin (“Sanrex SAN-C” manufactured by Mitsubishi Monsanto Kasei Co., Ltd.). In the test of the molded product, no delamination was observed.

As is evident from the above results, the molded article of the resin composition according to the present invention has almost no decrease in the total light transmittance despite having a ground glass appearance. Also, no delamination was observed in the molded product, and the physical properties such as impact strength
The value was equivalent to that of the resin.

Therefore, the thermoplastic resin composition having a high haze according to the present invention is useful as a molded article used in a field where a ground glass surface is required.

Claims (4)

(57) [Claims] 1. A thermoplastic resin having a high haze, wherein an aromatic vinyl monomer and a vinyl cyanide monomer are subjected to the following polymerization steps (1), (2) and (3). Manufacturing method. Polymerization Step (1) A step of subjecting an aromatic vinyl monomer to bulk polymerization to obtain a syrup composed of an unpolymerized monomer solution of a produced polymer having a weight average molecular weight of more than 350,000. Polymerization step (2) A vinyl cyanide monomer is added to the syrup and polymerization is continued to form an unpolymerized monomer solution of the produced polymer, and the polymer produced in the polymerization step (1) is added to the solution. A step of obtaining a syrup dispersed in fine particles therein. Polymerization Step (3) A step of continuing the polymerization of the syrup in the polymerization step (2) to obtain a thermoplastic resin. 2. The weight of the polymer produced in the polymerization step (1) is the total weight of the aromatic vinyl monomer and vinyl cyanide monomer added in the polymerization steps (1) to (3). The method according to claim 1, wherein the amount is 0.1 to 15% by weight. 3. The method according to claim 1, wherein the amount of the vinyl cyanide monomer is 1: 9 to 9: 1 by weight based on the unpolymerized monomer of the syrup obtained in the polymerization step (1). Item 1. The production method according to Item 1. 4. The production method according to claim 1, wherein the polymerization in the polymerization step (3) is bulk polymerization or suspension polymerization.