JP2000154319A - Production of styrene-based resin molding product and its molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrene-based resin molding product having excellent antistatic properties without damaging the appearance of molding product and without reducing the productivity of molding product. SOLUTION: This method for producing a styrene-based resin molding product comprises adding 5-50 pts.wt. of an antistatic agent (i) to 95-50 pts.wt. of a thermoplastic resin having 5,000-30,000 poise melt viscosity at 60 sec-1 shear rate at 200 deg.C and mixing and diluting them without applying a kneading operation to them to give a mixture (A) and simultaneously feeding the mixture and a styrene-based resin (B) to a molding machine. This styrene-based molding product is obtained by the method. The thermoplastic resin is preferably a styrene-based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrenic resin molded article having antistatic properties, and a molded article obtained therefrom.

[0002]

2. Description of the Related Art Styrene-based resins have high electrical insulation properties and are easily charged by friction or the like. Therefore, there has been a problem that dust and dirt adhere to the resin to impair the appearance of a molded article. In recent years, along with the remarkable development of electronic products such as video, computer, OA equipment, etc., generation of noise due to static electricity or breakage of IC parts, etc., has occurred on styrene resin moldings used for these products. It was an important issue. In order to prevent such a failure of the styrene-based resin molded article due to static electricity, for example, (1) a method of internally mixing an antistatic agent, and (2) a method of externally applying an antistatic agent are known.

However, the method (1) of kneading the antistatic agent into the interior has problems such as deterioration of the hue of the molded article and insufficient antistatic effect. In addition, there are disadvantages such as mold contamination occurring, and contaminants adhering to the molded body, impairing the commercial value, and reducing the productivity due to the need to frequently clean the mold. In addition, the method (2) for externally applying the antistatic agent is disadvantageous in terms of cost because a surface application step is required.

[0004]

SUMMARY OF THE INVENTION Under such circumstances,
An object of the present invention is to provide a styrenic resin molded article having excellent antistatic performance without impairing the appearance of the molded article or reducing productivity.

The inventors of the present invention have conducted intensive studies to achieve the above object. As a result, in a method of kneading a styrene-based resin as an antistatic agent, the antistatic agent was previously prepared by using a kneader such as an extruder. In the conventional method of kneading into the system resin, the heat history causes decomposition and discoloration of the antistatic agent, which causes mold contamination and deterioration of the hue of the molded product, and causes insufficient antistatic effect. I figured it out. Then, a composition obtained by adding an antistatic agent to a thermoplastic resin having a specific melt viscosity, mixing and diluting the mixture is supplied to a molding machine at the same time as the styrene resin without kneading in advance to form a molded article. The inventor has found that the method is remarkably effective in solving the above problems, and has completed the present invention.

[0006]

That is, the present invention provides a method for charging
5 to 50 parts by weight of the inhibitor (i) was added at a shear rate of 60 seconds.
c ^-15,000 to 3 melt viscosity at a temperature of 200 ° C
Thermoplastic resin (ii) 95-5 having a poise of 0000
0 parts by weight and mixed without adding a melt-kneading operation,
Diluted mixture (A) and styrene resin (B)
Is simultaneously supplied to a molding machine and molded.
Method for producing styrene-based resin molded article and styrene obtained therefrom
The present invention relates to a len-based resin molded article.

Hereinafter, the present invention will be described in detail. First, a mixture (A) comprising an antistatic agent (i) and a thermoplastic resin (ii) in the present invention (hereinafter referred to as a processed antistatic material (A)) will be described. The processed antistatic material (A) in the present invention corresponds to a so-called masterbatch of an antistatic agent, but is a mixture which does not undergo a melt-kneading operation unlike the conventional concept of a masterbatch.

In the present invention, as the antistatic agent (i) constituting the processed antistatic material (A), a known antistatic agent mainly comprising a surfactant is used. For example, alkyl diethanolamine, polyoxyethylene alkylamine,
Amine compounds such as alkyl diethanolamide and polyoxyethylene alkyl amide; polyoxyethylene compounds such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether and polyoxyethylene fatty acid ester; glycerin monostearate, alkyl sulfonate and alkyl benzene Anionic compounds such as sulfonates and alkyl sulfates; and cationic compounds such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, and benzalkonium salts, and the like, which can be used alone or in combination of two or more.

In the present invention, the thermoplastic resin (ii) constituting the processed antistatic material (A) has a shear rate of 60 seconds.
⁻¹ , melt viscosity at a temperature of 200 ° C. is 5,000 to 3
It is a thermoplastic resin in the range of 0.000 poise. Any known thermoplastic resin may be used as long as it satisfies this condition, but preferably a styrene-based thermoplastic resin of the same type or the same as the styrene-based resin (B) used for molding. If the thermoplastic resin (ii) is the same or the same styrene-based resin, not only the influence on the physical properties of the styrene-based resin (B) is reduced, but also the styrene-based resin (B) is easily and uniformly mixed. Therefore, it is preferable in that the appearance of the molded article is not impaired or the mechanical strength is less likely to be reduced.

The thermoplastic resin (ii) has a melt viscosity of 3
When it exceeds 000 poise, the antistatic agent is not uniformly kneaded in the obtained styrene resin molded product, and the antistatic effect of the molded product is reduced. On the other hand, if the melt viscosity is less than 5,000 poise, the impact strength of the molded article is undesirably reduced. Here, the melt viscosity refers to a value measured according to JIS K-7199.

A plasticizer such as liquid paraffin can be added to the thermoplastic resin (ii), if necessary, at any stage in the polymerization process, for example, during the preparation of the polymerization, during the polymerization, or after the completion of the polymerization.

As the shape of the thermoplastic resin (ii), those in the form of pellets, beads, powders, pulverized pieces such as molded products, etc. are used as appropriate.

The antistatic material for processing (A) in the present invention comprises:
The content of the antistatic agent is 5% in the processed antistatic material (A).
５０50% by weight, preferably 10-30% by weight. In the present invention, the processed antistatic material (A) plays a role of a masterbatch of the antistatic agent, and by using this, a small amount of the antistatic agent is uniformly mixed and diluted with the styrene resin (B). But the content of the antistatic agent is 5
If the amount is less than% by weight, the thermoplastic resin (i
The relatively large amount of i) makes uniform mixing difficult,
The master batch itself tends to be uneven. In addition, the handling amount is large, which is not practical, and is not advantageous in terms of cost. On the other hand, if the content exceeds 50% by weight, it is difficult to obtain a uniform styrene resin composition, which is not preferable because the antistatic effect of the molded article obtained due to uneven distribution of the antistatic agent is reduced and the appearance of the molded article is impaired.

The processed antistatic material (A) of the present invention may optionally contain a dispersant, a lubricant, an antioxidant, a weathering agent, a colorant and the like.

Next, the form and processing method of the processed antistatic material (A) in the present invention will be described below.
In the present invention, as a method of obtaining the processed antistatic material (A), a method of attaching the antistatic agent (i) to the surface of the thermoplastic resin (ii) is preferable. As a method of attaching,
When the antistatic agent (i) is a liquid, the antistatic agent (i) is added directly to the thermoplastic resin (ii). When the antistatic agent (i) is a solid, the liquefied antistatic agent (i) is heated to a temperature equal to or higher than the melting point. It is added to (ii) or diluted with a small amount of a plasticizer such as liquid paraffin as an adhesion aid and added to the thermoplastic resin (ii), and a blend such as a hand blend, a tumbler blend or a Henschel blend is applied. There is a method. Before the processing antistatic material (A) is supplied to a molding machine together with the styrene resin (B) to obtain a molded body, no melt-kneading operation is performed.

Styrene resin (B) used in the present invention
As polystyrene, AS resin, ABS resin, MS
(Methyl methacrylate-styrene copolymer) resin, M
Examples thereof include BS resin, MABS (methyl methacrylate-acrylonitrile-butadiene-styrene copolymer) resin, and HIPS (rubber-modified styrene resin). However, it is not limited thereto, but refers to a resin obtained by polymerizing a monomer having a weight ratio of styrene monomer of 40% by weight or more in the monomer at the time of polymerization preparation.

Next, a method for producing a styrenic resin molded article according to the present invention will be described. A feature of the method for producing a styrenic resin molded article of the present invention lies in that the styrenic resin (B) and the antistatic agent are supplied to a molding machine without melt-kneading in advance and molding is performed (hereinafter, direct molding and molding). Write). Conventionally, a generally used molding method is, for example, a method in which an antistatic agent is melt-kneaded with a styrene-based resin, pelletized, and then melt-molded again at the time of molding. Heat history. Exposure to these two thermal histories causes discoloration of the antistatic agent and the styrene-based resin and decomposition of the antistatic agent, resulting in problems such as impairing the appearance of the obtained molded article and lowering the antistatic effect. Was caused. In addition, the decomposed product of the antistatic agent causes contamination on the inside of the molding machine and on the surface of the mold, and the contaminants must be cleaned frequently. In the present invention, the styrenic resin (B) and the antistatic agent are used without being melt-kneaded in advance when obtaining the molded article, so that the number of times of exposure to the heat history is only one at the time of direct molding, and The above problems can be minimized.

In the present invention, molding refers to various molding methods having a melt-kneading process, such as injection molding, extrusion molding, inflation molding, and blow molding. In the present invention, the processed antistatic material (A) and the styrene resin (B)
Various methods can be adopted as a method of directly supplying the above to the molding machine. For example, a method in which a predetermined amount of the processed antistatic material (A) and the styrene-based resin (B) is measured and mixed is supplied from a hopper such as an injection molding machine and supplied, and the measured processed antistatic material ( A) and styrenic resin (B)
Each of which is periodically charged into a hopper and supplied, a method in which a predetermined amount of a working antistatic material (A) is charged halfway from a molten portion in the course of molding the styrene resin (B),
The method is not particularly limited as long as a required molded body can be obtained from the above-mentioned processed antistatic material (A) and styrene-based resin (B) in one heat history.

In the present invention, the ratio of the processed antistatic material (A) to the styrene resin (B) depends on the concentration of the antistatic agent in the processed antistatic material (A) and the antistatic effect required for the molded article. It can be arbitrarily changed according to the requirements, and is not necessarily limited, but is preferably processed antistatic material (A) 0.
Styrene resin (B) is 99.01 to 40 parts by weight.
99-60 parts by weight, more preferably (A) 0.1-2
(B) is in the range of 99.9 to 80 parts by weight with respect to 0 parts by weight.

[0020]

The present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. First, a method for producing a styrene resin used in Examples and Comparative Examples of the present invention will be described as Reference Example 1.

Reference Example 1 [Production method of styrene resin] (Styrene resin-1) 100 kg of pure water, 3 g of sodium dodecylbenzenesulfonate, 600 g of tribasic calcium phosphate, 90 kg of styrene, 4 kg of liquid paraffin in a 250 L autoclave. Was added, and 270 g of benzoyl peroxide and 45 g of t-butylperoxybenzoate were added as polymerization initiators, and the mixture was dispersed with stirring at a rotation speed of 150 rpm using a 500 mm diameter Faudler blade. This mixture was heated and polymerized at a temperature of 90 ° C. for 6.5 hours, at 115 ° C. for 2 hours, and then at 135 ° C. for 2 hours. After completion of the reaction, the beaded styrene-based resin obtained by washing, dehydration and drying was subjected to a single screw extruder (“PMS40-28” manufactured by IKEC Co., Ltd.) at a cylinder temperature of 22.
Extruded pellets at 0 ° C. were obtained to obtain styrene resin-1.
Table 1 shows the melt viscosity of the obtained styrene resin.

(Styrene resin-2) 100 kg of pure water, 0.5 g of sodium dodecylbenzenesulfonate, 250 g of tribasic calcium phosphate, 42 kg of styrene, methyl methacrylate 5 in an autoclave having a capacity of 250 L.
8 kg, dicumyl peroxide 1 as a polymerization initiator
00g and t-dodecyl mercaptan 3 as a chain transfer agent
50 g was added, and the mixture was dispersed with stirring at a rotation speed of 150 rpm using a Faudler blade having a diameter of 500 mm. The mixture was heated and polymerized at a temperature of 100 ° C. for 2 hours, at 115 ° C. for 3.5 hours, and then at 130 ° C. for 2.5 hours. Thereafter, styrene resin-2 was obtained by the same operation as styrene resin-1. Table 1 shows the melt viscosity of the obtained styrenic resin-2.

(Styrene resin-3) 90 kg of styrene
Was changed to 100 kg, and 4 kg of liquid paraffin was changed to 0 kg to obtain styrene resin-3 by the same operation as styrene resin-1. Table 1 shows the melt viscosity of the obtained styrene resin-3.

(Styrene resin-4) 90 kg of styrene
To 96 kg, and 500 g of t-dodecyl mercaptan as a chain transfer agent, to obtain a styrene resin-4 in the same manner as the styrene resin-1.
Table 1 shows the melt viscosity of the obtained styrenic resin-4.

(Styrene resin-5) In a 150 L autoclave, 92 kg of styrene and 8.0 kg of butadiene rubber were dissolved in 4 kg of liquid paraffin, and 40 g of benzoyl peroxide was added as a polymerization initiator. After heating at a temperature of 90 ° C. for 8 hours with stirring at a rotation speed of 250 rpm using a paddle blade, the block polymerization was stopped by cooling. Then, 50 kg of the reaction mixture was placed in a 250 L autoclave, and 100 g of dicumyl peroxide was newly added as a polymerization initiator. Next, 0.5 g of sodium dodecylbenzenesulfonate and 250 g of tribasic calcium phosphate were added to 100 kg of pure water as a suspension stabilizer, and the mixture was dispersed with a 500 mm diameter Faudler blade at 150 rpm while stirring.
The mixture was heated and polymerized at a temperature of 100 ° C. for 2 hours, at 115 ° C. for 3.5 hours, and at 130 ° C. for 2.5 hours. Thereafter, styrene resin-5 was obtained by the same operation as styrene resin-1. Table 1 shows the melt viscosity of the obtained styrene resin-5.

(Styrene resin-6) 92 kg of styrene
With 58.5 kg of styrene and methyl methacrylate 3
To a monomer mixture of 6.0 kg and 5.5 kg of n-butyl acrylate, 4 kg of liquid paraffin was added to 0 kg,
8.0 kg of butadiene rubber was used as a styrene-butadiene block copolymer (styrene monomer unit content 40%).
6.0 kg and the same operation as styrene resin-5 except that 200 g of t-dodecylmercaptan was added as a chain transfer agent.
I got Table 1 shows the melt viscosity of styrene resin-6.

(Styrene-based resin-7) Rubber-modified styrene-based resin-7 was obtained in the same manner as in styrene-based resin-6 except that t-dodecylmercaptan was not added as a chain transfer agent. Table 1 shows the melt viscosity of the obtained styrene resin-7.

(Styrene resin-8) Styrene resin-8 was obtained by the same operation as styrene resin-6 except that 1,000 g of t-dodecylmercaptan was added as a chain transfer agent. Table 1 shows the melt viscosity of the obtained styrene resin-8.

Next, the formulation of the processed antistatic material (A) used in the examples and the blended formulation of the processed antistatic material (B) used in the comparative example will be described as Reference Example 2.

REFERENCE EXAMPLE 2 [Blending formulation of processed antistatic material (A) and processed antistatic material (B)] Each of the above-mentioned styrene-based resins as a thermoplastic resin,
Processed antistatic material 1 by hand blending a polyoxyethylene alkylamine-based antistatic agent (manufactured by Miyoshi Yushi Co., Ltd., Duspar 125B) as an antistatic agent in the blending amounts shown in Table
To 10 were obtained. However, processed antistatic materials 1, 4, 6 to 10
As for, a liquid obtained by heating and melting an antistatic agent at a temperature of 80 ° C. was used. In addition, processing antistatic material 2,
As for Nos. 3 and 5, liquid paraffin, DIBA (di-isobutyl adipate) and DOA (di-2-ethylhexyl adipate), which are plasticizers, were used in combination with the styrene resin in the amounts shown in Table 2, respectively.

The processed antistatic materials 11 to 13 were prepared by mixing each of the styrene resins described above as thermoplastic resins and a polyoxyethylene alkylamine based antistatic agent (Dasupar 125B, manufactured by Miyoshi Oil & Fat Co., Ltd.) as an antistatic agent as shown in Table 2. After hand blending with the amount, the extruder (PM
S40-28 ") Melt-kneading at a cylinder temperature of 220 ° C, extrusion and pelletization of processed antistatic material (B)
It is.

Next, examples and comparative examples of the present invention will be described below. Examples (Comparative Examples) [Examples 1 to 7, Comparative Examples 1 to 11] Quantitative feeders of a styrene resin and a processed antistatic material so that the blending ratio (based on parts by weight) shown in Tables 3 and 4 was used. And measured and supplied to a hopper of an injection molding machine to obtain a styrene resin molded product. In addition, the melt-kneaded product was injection-molded independently to obtain a styrene resin molded product. Examples 1 to 3 and Comparative Examples 1 to 6 are examples of a molded article of a styrene-based resin in which the styrene-based resin does not contain a rubber component, while Examples 4 to 7 are examples.
And Comparative Examples 7 to 11 are examples of a molded article of a styrene resin in which the styrene resin contains a rubber component. Comparative Example 6 is an example in which an antistatic agent was directly added to the styrene-based resin (B) without using a processed antistatic material and molded directly.

The injection molding was performed under the following conditions. Injection molding machine: K-125 (manufactured by Kawaguchi Iron Works), screw: full flight type, nozzle: TMW-16-06
(Toray Engineering Co., Ltd., static mixer),
Cylinder temperature: 220 ° C., mold temperature: 40 ° C., injection pressure: minimum filling pressure + 5 Kg / cm ² , injection speed: 50% molded product: plate-shaped molded product (127 mm × 127 mm × 2 mm)
Thickness) Various physical properties were evaluated using the molded body thus obtained, and the results are shown in Tables 3 and 4. In the examples, the antistatic property, the falling weight strength, the YI value,
It shows good values in any of the stain resistances, and is superior to the comparative examples. However, the measuring method and evaluation method of each characteristic value are as follows.

Method for measuring characteristic values (1) Surface resistivity: JI is used as an index of the antistatic effect.
In accordance with SK-6911, the molded body was conditioned at a temperature of 23 ° C. and a humidity of 50% RH for 24 hours to measure the surface resistivity. Those having a surface specific resistance value in the order of 10 ¹⁰ Ω were judged as acceptable levels. (2) Drop weight strength: As an index of impact strength, a weight was dropped on a molded body, a 50% breaking height was obtained, and the average value of the energy (weight × height) of the sample number n = 20 was obtained. Indicated. (3) YI (yellowness): JIS K as an index of hue
It measured according to -7103. The relationship between YI and hue is as follows. Y5 = colorless, Y10 = very light yellow, Y
40 = light yellow, Y60 = yellow, Y80 = dark yellow, Y10
0 = tan. YI of 5 or less was judged as a pass level. (4) Degree of contamination of a molded article: the number of shots until a decomposition product of an antistatic agent or the like adheres to the surface of the molded article when the molded article is produced by an injection molding machine and contamination starts. At least 300 times or more were judged as the pass level. (5) Degree of mold contamination: When a molded body is created by an injection molding machine,
The number of shots until the decomposition product of the antistatic agent adheres to the mold surface and contamination starts. At least 300 times or more were judged as the pass level. (6) Melt viscosity: 200 ° C., shear rate 60 sec ⁻¹ , capillary length 4 according to JIS K-7199
It was measured under the conditions of 0 mm and a diameter of 1 mm.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

The styrenic resin molded article obtained by the direct molding method according to the present invention is one in which the reduction of the antistatic effect and the deterioration of the hue due to the heat history are minimized. further,
In the styrenic resin molded product by direct molding of the present invention, the pre-melt kneading step of the antistatic agent and the styrenic resin can be omitted, and as a result, it is advantageous in terms of cost, and the industrial utility value of the present invention Is extremely large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C08L 25/00 C08L 25/00 F term (reference) 4F070 AA11 AA18 AC43 AC46 AC57 AE05 FA09 FA10 FB05 FB06 FC02 FC03 4F206 AA13C AB09 AC01 AH33 JA07 JF02 JF21 4F207 AA13C AB09 AC01 AH33 KA01 KF02 4J002 AA011 BB072 BB151 BB152 BB162 BC031 BC032 BC041 BC042 BN141 BN142 CH023 CH053 EH056 EN106 EN136 EP016 EV186 EV246

Claims (3)

[Claims] 1. A thermoplastic resin (ii) having a melt viscosity of 5,000 to 30,000 poise at a shear rate of 60 sec.sup.- ¹ and a temperature of 200.degree. A styrene-based resin which is supplied to a molding machine at the same time as a mixture (A) obtained by mixing and diluting without adding a melt-kneading operation to a part by weight and a styrene-based resin (B) to be molded. A method for producing a molded article. 2. The method for producing a styrenic resin molded product according to claim 1, wherein the thermoplastic resin (ii) is a styrenic resin. 3. A styrenic resin molded product produced by the method for producing a styrenic resin molded product according to claim 1 or 2.