JPH0218329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for producing colored expandable particles. More specifically, the present invention relates to a method for producing colored expandable particles that has a high dye impregnation efficiency, is uniform in color, has a good coloring state, and is easy to obtain, and is advantageous in terms of manufacturing operations.

BACKGROUND ART Expandable particles, which are thermoplastic resin particles impregnated with a blowing agent, have been widely used in the field of foam production. In order to obtain colored foam molded articles, a method has been carried out in which colored expandable particles are used as a raw material.

Methods for coloring such expandable particles include (a) adding a pigment or dye to the expandable particles and stirring them in a container, and (b) suspending the expandable particles in water and adding dye and dye to the liquid. A method in which a coloring aid (solvent) is added (see Japanese Patent Publication No. 52-41303), and (c) a dye is added to the suspension during the production of expandable particles to simultaneously impregnate the foaming agent and color the particles. There are known methods for doing this.
Among these methods, method (a) is often carried out at the site of use, but since the obtained colored expandable particles basically only have dyes or pigments attached to the surface of the expandable particles, pre-expanded The foam is easily washed away by the water vapor used during molding and in-mold molding, and in particular, the water vapor is jetted vigorously from the slits in the mold, making the color around the slits lighter, resulting in a uniformly colored foam. It was difficult. Furthermore, the amount of dye or pigment deposited on the surface of the foamable particles was not uniform, resulting in uneven coloring, and when the foamed molded product was cut, there was uneven coloring on the surface and inner surface. In addition, since such coloring methods are usually carried out by stirring for 20 to 30 minutes in open drums, etc., the foaming agent in the foamed particles evaporates and the expansion ratio during molding decreases. There were times when it decreased.

On the other hand, methods (b) and (c) are both carried out in an aqueous system, so the dispersed dye is not completely absorbed into the expandable particles and remains in the aqueous system, requiring the use of extra dye. Moreover, it is difficult to treat the colored water separated after coloring, and it is necessary to provide treatment facilities (for example, an evaporator and an activated carbon adsorption tower). In addition, since water is used as a medium, a container larger than the volume occupied by the suspended foam particles is required.Furthermore, although there is no particular problem when using the same color dye continuously, it is necessary to replace the dye with a different color. In some cases, it is necessary to clean the inside of the container, but this takes a considerable amount of time and is disadvantageous in terms of workability.

This invention has been made to solve these conventional problems. Thus, according to the present invention, expandable particles obtained by impregnating polystyrene resin particles with a volatile blowing agent in advance are placed in a closed container, and then a predetermined amount of dye and a small amount of the volatile blowing agent are added to the expandable particles. A method for producing colored expandable particles, characterized in that the expandable particles are sufficiently stirred and mixed with the expandable particles at a temperature at which the expandable particles do not foam and in a substantially anhydrous atmosphere to impregnate the expandable particles with a dye. is provided.

According to the method of the present invention, there is no need to use extra dye as in the conventional method carried out in an aqueous medium, and the dye can be impregnated efficiently. In addition, it is possible to obtain products that are sufficiently and uniformly colored not only on the surface but also on the interior, as required, and molded products using this material as a raw material have little color unevenness, and the surfaces and inner surfaces of the foamed beads in the cross section. The coloring state is good with little color unevenness. In addition, since the coloring is carried out in a ``substantially anhydrous atmosphere'' without using water as a medium, there is no drainage and is industrially advantageous.
The container also does not require extra space, and a smaller container can be used, which is advantageous in terms of manufacturing operations. Furthermore, since the dye itself is added in a dry manner, it does not contaminate manufacturing equipment, unlike when it is added in a wet manner. Furthermore, the colored expandable particles obtained by the present invention also have the effect that the expandability thereof is higher than that before coloring.

The volatile blowing agent used in the coloring of this invention includes blowing agents known in the art as described below, and saturated hydrocarbons such as propane, butane, hexane, pentane, neopentane, and octane are preferred. Hydrocarbons that are liquid at room temperature and pressure are preferred for handling. Moreover, these may be in the form of a mixture. Note that it is preferable to use a blowing agent that is the same as or similar to the blowing agent in the normally expandable particles from the viewpoint of impregnating properties.

On the other hand, various dyes known in the art can be used as the dyes used in this invention, and specifically, azo dyes, anthraquinone dyes, azine dyes, quinoline dyes, etc. are preferably used. These can be either water-soluble or oil-soluble.

Note that various types of expandable particles known in the art can be used as the expandable particles obtained by impregnating polystyrene resin particles with a volatile blowing agent, such as hydrocarbons such as propane, butane, pentane, and methyl chloride. , methylene chloride, dichlorodifluoromethane, dichlorotetrafluoroethane,
Monochlorodifluoromethane, trichlorotrifluoroethane, trichlorotrifluoromethane,
Halogenated hydrocarbon solvents such as dichloromonofluoromethane and octafluorodichlorobutane are mixed with polystyrene resin particles (e.g. polystyrene, styrene-ethylene copolymer resin, styrene-
Typically, particles obtained by impregnating particles with a base resin such as maleic anhydride copolymer resin are used. Note that these volatile foaming agents, including those used for coloring, may contain some swelling solvents (toluene, benzene, xylene, etc.).

In this invention, first, a predetermined amount of the expandable particles is added into a closed container. Next, a predetermined amount of dye and a small amount of volatile foaming agent are added to the container and mixed with the foamable particles by stirring. The dye and the blowing agent may be added and mixed separately or at the same time. Usually, the dye is added to the expandable particles in a closed container in advance and mixed with stirring to coat or adhere the dye to the particle surface, and then a small amount of volatile foaming agent is gradually added by dropwise etc. and mixed thoroughly with stirring. It is preferable to let The amount of dye is 0.005 to 1.0 parts by weight, preferably 0.03 to 0.6 parts by weight per 100 parts by weight of expandable particles.
Added in parts by weight. The amount to be added may be appropriately determined within such a range depending on the desired degree of coloring.

If the amount of dye added is too large, excess dye will remain, which is undesirable. Further, the amount of the volatile foaming agent to be added may be a small amount relative to the expandable particles, and usually, it is appropriate to use 0.5 to 10 parts by weight per 100 parts by weight of the expandable particles, and preferably 2 to 4 parts by weight. . If the amount of the solvent is too large, it is unsuitable because it causes particles to coalesce and bubbles become rough, and when it is too small, it is unsuitable because it takes a long time to impregnate the dye and causes uneven color.

These dyes and foaming agents are added by thorough stirring and mixing at a temperature at which the expandable particles do not foam (usually between room temperature and 60°C, preferably between 20 and 50°C) and in a substantially anhydrous atmosphere. It will be done. Note that in order to speed up the processing time, it is appropriate to make the temperature as high as possible. By the above operations, the dye is efficiently impregnated into the expandable particles using the blowing agent as a medium, and uniformly colored expandable particles are obtained. The stirring and mixing time for adding the foaming agent at this time is usually about 0.5 to 3 hours. In this way, the expandable particles are impregnated with the dye, and by removing them from the container, colored expandable particles are obtained.

The colored expandable particles obtained in this way are uniformly colored inside as described above, but because a blowing agent is used during the coloring process, the expandability itself (during molding) is lower than before coloring. The foaming ratio (expansion ratio) has also increased, and the foamability does not deteriorate as a result of coloring as in the past.

Examples of this invention will be shown below.

Example 1 An experiment was conducted using polystyrene resin expandable particles ("Eslen Beads"; trade name of Sekisui Plastics Co., Ltd.) containing 5% by weight of butane as a blowing agent. These expandable particles expanded approximately 50 times in size when heated with steam for 3 minutes. Coloring was performed using these expandable particles and a green dye (Diaresin Fast Brill.Green5G; trade name of Mitsubishi Chemical Industries, Ltd.).

First, 1000 g of expandable particles were added to a rotating container with an internal volume of about 5 ml, and a green dye (Diaresin Fast Brill
Green 5G) 0.2g was added and mixed by stirring for 10 minutes, and then 30g of pentane was poured dropwise into the container. During dropping, the rotating container and expandable particles were maintained at about 35°C, and the flow rate was adjusted so that the entire amount of pentane could be injected and dropped in 30 minutes. After the dropping was completed, the mixture was kept at 35° C. and rotated for 1 hour, and then cooled and the expandable particles were taken out from the rotating container to obtain colored expandable particles. The colored expandable particles were uniformly colored without uneven coloring, had no change in fluidity or transparency from those before coloring, and were easy to handle.
Furthermore, when the particles were pressed against white paper with a finger,
No coloring was observed on the white paper, and the dye was not coated on the surface of the particles, but was uniformly impregnated into the particles.

When such colored expandable particles were subjected to in-mold molding using water vapor, a uniformly colored foam approximately 60 times larger than that before coloring (approximately 50 times larger) was obtained after heating for 3 minutes.
It was found that the foamability was also improved compared to the above.

In addition, blue dye (Diaresin Blue) is used as dyeing.
P# 120), red dye (Diaresin Red5), and yellow dye (Diaresin Yellow FC) were used to produce colored expandable particles in the same manner as above, but beautiful expandable particles with good colorability were also produced. It was obtained, and the foamability was also improved.

In addition, when coloring is done simply by mixing without adding pentane, the particles obtained are mainly dye coated on the particle surface and have reduced fluidity, and when pressed against white paper. It was colored and difficult to handle.

Example 2 Example 1 except that a mixed blowing agent containing 40 g of butane and 1 g of toluene was used as a blowing agent for coloring treatment.
Similar colored expandable particles which were uniformly colored were obtained in the same manner as above. The foaming ratio of these particles was approximately 65 times, which was excellent.

Example 3 Similar colored expandable particles were obtained by carrying out the same process as in Example 1, except that the dye and the blowing agent were added to the foam at the same time using a mixed solution of the dye in 30 g of pentane.

Claims (1)

[Claims] 1. In a closed container, expandable particles obtained by impregnating polystyrene resin particles with a volatile foaming agent in advance are placed,
Next, a predetermined amount of dye and a small amount of a volatile blowing agent are thoroughly stirred and mixed with the expandable particles under a temperature at which the expandable particles do not foam and in a substantially anhydrous atmosphere to form a dye. A method for producing colored expandable particles, characterized by impregnating expandable particles with. 2. The manufacturing method according to claim 1, which comprises adding the dye to the expandable particles and stirring and mixing, and then gradually adding a small amount of a volatile blowing agent and thoroughly stirring and mixing. 3 For 100 parts by weight of expandable particles, approximately
Claim 1 in which 0.005 to 1.0 parts by weight are added
The manufacturing method described in paragraph 2 or paragraph 2. 4 A small amount of volatile blowing agent mixed into foamable particles
The manufacturing method according to any one of claims 1 to 3, wherein the amount is 0.5 to 10 parts by weight per 100 parts by weight.