JP2003277514A - Surface treatment method for expandable thermoplastic resin particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method for an expandable thermoplastic resin particle which makes the peeling quantity of coating materials small in a process of coating the surface of the particle with a powdery coating material and a liquid coating material. <P>SOLUTION: In this surface treatment method for the expandable thermoplastic resin particle which comprizes coating the surface of the expandable thermoplastic resin particle with the powdery coating material and the liquid coating material, a process in which the liquid coating material is applied after applying the powdery coating material on the surface of the expandable thermoplastic resin particle is contained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thermoplastic resin particles used in the production of foamed resin molded articles, and in particular, a coating agent for preventing blocking is difficult to peel off, and paste scale deposits such as particle transport pipes are generated. The present invention relates to a surface treatment method for expandable thermoplastic resin particles which can suppress the occurrence of blocking during pre-expansion with a small amount of an additive.

[0002]

2. Description of the Related Art In order to produce a foamed molded article from expandable thermoplastic resin particles, first, the expandable thermoplastic resin particles are put into a pre-expanding machine and heated with a heating medium such as steam to obtain a desired bulk. A general method is to prepare pre-expanded particles of a magnification, put them in a cavity of a molding die, and heat them with a heating medium such as steam to heat-bond the particles to each other to obtain a foam-molded article as in the mold. As the properties required for the expandable thermoplastic resin particles to be subjected to such a method, the pre-expanded particles do not cause blocking in the pre-expanding machine, and the pre-expanded particles are sufficiently fused to each other during molding, and the appearance It is possible to obtain a beautiful molded product having excellent mechanical strength.

Conventionally, a technique for preventing blocking during preparation of pre-expanded particles has been proposed. For example, in Japanese Patent Laid-Open No. 6-116435, the resin particles 100 are formed on the surface of expandable styrene resin particles. 0.1 to 0.5 parts by mass of a metal salt of a higher fatty acid, 0.01 to 0.5 parts by mass of a liquid fatty acid ester at room temperature, and 0.01 to 0. A foamable styrenic polymer formed by coating 2 parts by mass is disclosed. Further, in the same publication, as a method of applying a metal salt of higher fatty acid, a fatty acid ester which is liquid at room temperature and a fatty acid ester which is solid at room temperature to the surface of particles, a fatty acid ester which is liquid at room temperature is formed on the surface of expandable styrene resin particles. It is described that the order of applying a fatty acid ester and a metal salt of a higher fatty acid, which are solid at room temperature, is first applied. It is described that it is preferable to apply a material in the form of particles to prevent the particles from getting wet and to sufficiently exert the effect of preventing peeling.

[0004]

However, in the above-mentioned prior art, the liquid and powder coating agents applied to the surface of the particles are easily separated from the surface of the particles, and the mixture of the powder and the liquid separated from the particles is easily removed. Are accumulated as paste-like deposits on the particle transportation pipes, filter clogging of the pre-foaming machine, filter malfunction in the molding machine die, slit clogging, etc. occur more frequently. There was a risk of trouble. In addition, since the liquid and powder coating agent applied to the particle surface is easily separated from the particle surface, the coating amount of the coating agent must be increased, which leads to an increase in manufacturing cost and the mechanical strength of the molded product. Could be exacerbated.

The present invention solves the above-mentioned drawbacks of the prior art, and in the step of applying a powder coating agent and a liquid coating agent to the surface of the particle body, surface treatment of expandable thermoplastic resin particles with a small amount of coating agent peeling. It is intended to provide the law.

[0006]

To achieve the above object, the present invention applies a powder coating agent solid at room temperature and a liquid coating agent liquid at room temperature to the surface of the expandable thermoplastic resin particle body. A method of surface-treating expandable thermoplastic resin particles comprising: comprising a step of applying the liquid coating agent after applying the powder coating agent on the surface of the expandable thermoplastic resin particle body. The present invention provides a surface treatment method for expandable thermoplastic resin particles.

In the surface treatment method for expandable thermoplastic resin particles of the present invention, it is preferable that the powder coating agent contains a metal salt of a higher fatty acid or a solid fatty acid ester.
The liquid coating agent is preferably at least one selected from the group consisting of liquid fatty acid esters, liquid polyorganosiloxanes, and liquid hydrocarbons. Further, on the surface of the expandable thermoplastic resin particle body, after applying the powder coating agent, the step of applying a liquid coating agent, while charging the expandable thermoplastic resin particle body into a stirring device while stirring. It is preferable that after applying the powder coating agent, the liquid coating agent is put into the stirring device and stirred. Further, the expandable thermoplastic resin particles are preferably expandable styrene resin particles.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The surface treatment method for expandable thermoplastic resin particles according to the present invention comprises a powder coating agent that is solid at room temperature and a liquid coating agent that is liquid at room temperature on the surface of the expandable thermoplastic resin particle body. It is used for producing expandable thermoplastic resin particles by coating, and includes a step of applying the powder coating agent on the surface of the expandable thermoplastic resin particle body and then applying a liquid coating agent. It is characterized by that.

The expandable thermoplastic resin particle body comprises styrene resin particles, methacrylic acid ester resin particles, polyphenylene ether resin particles, polycarbonate resin particles, polyethylene resin particles, polypropylene resin particles, polyester resin particles. A thermoplastic resin particle such as is impregnated with a foaming agent. Among these, those obtained by impregnating styrenic resin particles with a foaming agent are excellent in moldability because a foam molded product can be obtained even with steam (heating medium) at a relatively low pressure. Further, the foam-molded article is suitable because it has an appropriate strength. The styrene resin particles are preferably formed into beads (spherical shape) using a styrene monomer as a raw material and a polymerization method such as a suspension polymerization method or a seed polymerization method. Alternatively, a bulk polymerization method may be used, or a pellet (cylindrical) shape may be used. As the styrene-based monomer, a styrene monomer, or a monomer mixture containing styrene as a main component, that is, styrene alone or containing styrene as a main component, and a small amount of another monomer are mixed therewith. It is a monomer mixture. Examples of the "other monomer" other than styrene include styrene-based monomers such as α-methylstyrene, p-methylstyrene, t-butylstyrene, and chlorostyrene, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, and the like. Methacrylate monomers, acrylate-based monomers such as ethyl acrylate and 2-ethylhexyl acrylate, vinyl cyanide-based monomers such as acrylonitrile and methacrylonitrile, and polyfunctional monomers such as divinylbenzene and polyethylene glycol dimethacrylate. Etc. Also,
A proper amount of a rubber-like substance may be added to obtain a reinforced resin.

The foaming agent with which the thermoplastic resin particles are impregnated has a volatile property such that the boiling point is not higher than the softening point of the thermoplastic resin particles, for example, propane, butane, pentane, cyclopentane, hexane, HCFC-141b, HCFC.
-142b, HCFC-124, HFC-134a, H
FC-152a etc. are mentioned, These foaming agents can be used individually or in combination of 2 or more types. The amount of the volatile foaming agent used is based on the obtained polymer particles.
It is 1 to 10% by mass, preferably 2 to 7% by mass. Further, particularly in the case of styrene-based resin particles, in the suspension polymerization method or the seed polymerization method, the foaming agent is usually added by press-fitting after the polymerization or after the polymerization to impregnate the resin particles.

Among the coating agents used in the present invention, the powder coating agent which is solid at room temperature preferably contains a metal salt of a higher fatty acid or a fatty acid ester which is solid at room temperature.
Further, both a metal salt of higher fatty acid and a fatty acid ester which is solid at room temperature may be contained. As the metal salt of higher fatty acid, a compound comprising a saturated fatty acid having 14 or more carbon atoms such as palmitic acid and stearic acid and a metal ion such as calcium, zinc and magnesium is used, and examples thereof include zinc stearate, calcium stearate and stearin. Magnesium acid etc. are mentioned. Examples of the fatty acid ester that is solid at room temperature include triglyceride, diglyceride, monoglyceride, esters with higher alcohols and fatty acid amides of saturated fatty acids having 14 or more carbon atoms such as palmitic acid and stearic acid.

The metal salt of higher fatty acid is added in an amount of 0.03 to 0.40% by mass, preferably 0.10 to 0.20% by mass, based on the thermoplastic resin particles. Further, the fatty acid ester is 0.01 to 0.01 with respect to the thermoplastic resin particles.
0.40% by mass, preferably 0.10 to 0.30% by mass
It is added in the range of. If the addition amount of these is less than the above range, the effect of preventing blocking at the time of preparation of pre-expanded particles cannot be sufficiently obtained, and if the addition amount of these exceeds the above range, these powder additives are added from the particle surface. The peeling is facilitated and the manufacturing cost is increased.

The liquid coating agent is preferably at least one selected from the group consisting of fatty acid esters which are liquid at room temperature, liquid polyorganosiloxanes and liquid hydrocarbons. Examples of fatty acid esters that are liquid at room temperature include triglycerides of unsaturated fatty acids, examples of liquid polyorganosiloxanes include polydimethylsiloxane, and examples of liquid hydrocarbons include liquid paraffin. You can This liquid coating agent is used for thermoplastic resin particles in an amount of 0.
01 to 0.10% by mass, preferably 0.03 to 0.08
It is added in the range of mass%. If the added amount is lower than the above range, the function of adhering the powder coating liquid to the particle surface may be weakened. On the other hand, if the amount added exceeds the above range, the additive is likely to peel off and the manufacturing cost increases.

In the step of applying the powder coating agent on the surface of the expandable thermoplastic resin particle body and then applying the liquid coating agent, the expandable thermoplastic resin particle body is put into an appropriate stirring device (mixer). It is preferable that the powder coating material is applied while being stirred, and then the liquid coating material is put into the stirring device and stirred. The timing of adding the liquid coating agent is 10% to 80% of the total stirring time after the powder coating agent is charged.
It is preferably in the range of%. If the timing of introducing the liquid coating agent is too early or too late, the peeling amount of the coating agent increases, which is not preferable.

The expandable thermoplastic resin particles obtained by applying the powder coating agent and the liquid coating agent are put into a pre-expanding machine and heated with a heating medium such as steam. As a result, pre-expanded particles having a predetermined bulk ratio are put into a cavity of a molding die and heated with a heating medium such as steam to heat-bond the particles to each other to obtain a foam-molded article as the mold.

[0016]

Example (Method of measuring the amount of coating agent peeled off) The expandable styrenic resin particles (measurement sample) produced in Examples 1 to 7 and Comparative Examples 1 to 4 described later were coated with a coating agent by the test apparatus shown in FIG. The amount of peeling was measured. The test device of FIG.
A funnel 1 made of transparent polyvinyl chloride, and an acrylic plate 2 provided below the tube of the funnel 1 with a slight distance between them and being inclined.
And a fixed base 3 for holding the acrylic plate 2. The dimensions a to d of each part of the test apparatus are funnel diameter a = 2.
50 mm, funnel height b = 120 mm, funnel tube length c
= 1040 mm, the distance between the tube and the acrylic plate 2 d = 30 m
m. Moreover, the diameter of the funnel tube is 20 mm, and the acrylic plate 2
Has a length of 130 mm, a width of 50 mm, and a thickness of 2 mm, and the acrylic plate 2 has an inclination of 30 °.

After measuring the weight of the acrylic plate 2, the acrylic plate 2 is fixed to the fixing base 3. From the upper opening of the funnel 1, 2000 g of a measurement sample is put and dropped. This 5
After repeating the cycle, the acrylic plate 2 is removed and the weight is measured. The difference between the weights of the acrylic plate before the test and that after the test was taken as the amount of peeling of the coating agent.

[First Embodiment] As shown in FIG.
5, a shaft 13 with a plurality of stirring blades 14 driven to rotate is inserted, and a Roedige mixer (made by Matsuzaka Giken Co., Ltd.) having a stirring bowl 10 (capacity 18.8 L) provided with an inlet 11 and an outlet 12. From the charging port 11 of M-20), the expandable styrene resin particle body (manufactured by Sekisui Plastics Co., Ltd., trade name HDL, average particle size 0.6 to 1.1 mm) 20
After adding 00 g and stirring for 0.5 minutes at a rotation speed of 160 rpm, zinc stearate (trade name: zinc stearate, manufactured by NOF CORPORATION) was used as a powder coating agent. 0.15% by mass, fatty acid triglyceride (manufactured by Riken Vitamin Co., Ltd., trade name Rikemar VT-50) is 0.17% by mass, based on the mass of the expandable styrene resin particles, fatty acid monoglyceride (RIKEN Vitamin Co., Ltd. (Trade name: RIKEMAR S-100P) manufactured by K.K. Next, a liquid coating agent, polydimethylsiloxane (trade name S, manufactured by Toray Dow Corning Silicone Co., Ltd.)
HH200-100CS) was added in an amount of 0.05% by mass with respect to the mass of the expandable styrene resin particles, and the stirring was continued for 4.0 minutes. At the end of this stirring time, the outlet 12
Then, the expandable styrene resin particles (measurement sample) having the surface coated with the solid-liquid coating agent were taken out. The obtained measurement sample was applied to the test apparatus shown in FIG. 1 as described above to measure the amount of coating agent peeling, and the results are shown in Table 1.

[Example 2] The stirring time after charging the powder coating agent was 1.5 minutes, and the stirring time after charging the liquid coating agent was 3.5.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Example 3] The stirring time after charging the powder coating agent was 2.0 minutes, and the stirring time after charging the liquid coating agent was 3.0.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Embodiment 4] The stirring time after charging the powder coating agent was 2.5 minutes, and the stirring time after charging the liquid coating agent was 2.5.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Embodiment 5] The stirring time after charging the powder coating agent was 3.0 minutes, and the stirring time after charging the liquid coating agent was 2.0.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Embodiment 6] The stirring time after charging the powder coating agent was 4.0 minutes, and the stirring time after charging the liquid coating agent was 1.0.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Embodiment 7] The stirring time after charging the powder coating agent was 4.5 minutes, and the stirring time after charging the liquid coating agent was 0.5.
A measurement sample was prepared in the same manner as in Example 1 except that the amount was separated, and the amount of peeling of the coating agent was measured. The results are shown in Table 1.

[Comparative Example 1] A measurement sample was prepared in the same manner as in Example 1 except that the powder coating agent and the liquid coating agent were simultaneously charged and stirred for 5.0 minutes, and the amount of the coating agent peeled off was measured. The results are shown in Table 1.

[Comparative Example 2] A measurement sample was prepared in the same manner as in Example 1 except that only the powder coating agent was charged and the stirring time after charging was 5.0 minutes, and the amount of coating agent peeling was measured. The results are shown in Table 1.

[Comparative Example 3] The order of feeding the powder coating agent and the liquid coating amount was changed, the liquid coating agent was first charged and stirred for 2.5 minutes, and then the powder coating agent was charged for 2.5 minutes. A measurement sample was prepared in the same manner as in Example 1 except that stirring was performed,
The amount of coating agent peeled off was measured, and the results are shown in Table 1.

[Comparative Example 4] The order of feeding the powder coating agent and the liquid coating amount was changed, the liquid coating agent was first charged and stirred for 4.5 minutes, and then the powder coating agent was charged for 0.5 minutes. A measurement sample was prepared in the same manner as in Example 1 except that stirring was performed,
The amount of coating agent peeled off was measured, and the results are shown in Table 1.

[0029]

[Table 1]

FIG. 3 is a graph showing the peeled amount (mg) for each sample shown in Table 1. From the graph of FIG. 3 and the data of Table 1, the powder coating agent was applied to the surface of the expandable styrenic resin particle body according to the present invention, and then the liquid coating agent was applied to simultaneously apply these coating agents. Alternatively, as compared with the case where the liquid coating agent is applied first and the powder coating agent is applied later, the amount of these coating agents separated from the surface of the expandable styrenic resin particle main body can be reduced.

[0031]

As described above, according to the present invention, the surface treatment of the expandable thermoplastic resin particles having a small amount of coating agent peeling in the step of applying the powder coating agent and the liquid coating agent to the surface of the particle body. Can provide the law.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a test apparatus for measuring the amount of coating agent peeling in an example according to the present invention.

FIG. 2 is a schematic configuration diagram for explaining the stirring device used for the surface treatment of the expandable thermoplastic resin particles in the same example.

FIG. 3 is a graph showing the amount of coating agent peeling of each sample of the example.

Claims (5)

[Claims] 1. A surface treatment method for expandable thermoplastic resin particles, which comprises applying a powder coating agent solid at room temperature and a liquid coating agent liquid at room temperature to the surface of the expandable thermoplastic resin particle body. A surface treatment method for expandable thermoplastic resin particles, which comprises the step of applying the powder coating agent on the surface of the expandable thermoplastic resin particle body and then applying a liquid coating agent. 2. The surface treatment method for expandable thermoplastic resin particles according to claim 1, wherein the powder coating agent contains a metal salt of a higher fatty acid or a solid fatty acid ester. 3. The expandable thermoplastic resin particles according to claim 1, wherein the liquid coating agent is at least one selected from the group consisting of liquid fatty acid esters, liquid polyorganosiloxanes, and liquid hydrocarbons. Surface treatment method. 4. The step of applying the powder coating agent on the surface of the expandable thermoplastic resin particle body and then applying the liquid coating agent is performed by introducing the expandable thermoplastic resin particle body into an agitator. The surface treatment method for expandable thermoplastic resin particles according to any one of claims 1 to 3, which is carried out by applying a powder coating agent while stirring and then introducing the liquid coating agent into the stirring apparatus and stirring. 5. The surface treatment method for expandable thermoplastic resin particles according to claim 1, wherein the expandable thermoplastic resin particles are expandable styrene resin particles.