JPH1135731A - Preexpanded particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain preexpanded particles which give molded articles with less unevenness in coloration and hardly contg. voids among particles by preexpanding colored expandable polystyrene resin pellets in such a manner that the ratio of the length to the breadth of the resultant preexpanded particle is in a specified range. SOLUTION: A colored expandable polystyrene resin pellet having a length L and a breadth D is preexpanded by about 10-50 times in such a manner that the length L and the breadth D change into the length (l) and the breadth (d), respectively, of the resultant preexpanded particles and that the ratio of the length (l) to the breadth (d) satisfies the relation: 1<l/d<=4. The ratio of the length L to the breadth D is pref. 5-30. Pref., the length (l) satisfies the relation: W<=3 l (wherein W is the diameter of a filling port of a mold) in terms of easiness of mold filling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pre-expanded particles of expandable polystyrene resin pellets for obtaining a good molded article having no color unevenness and no particle gap.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining pre-expanded particles of colored expandable particles, a colorant such as a pigment or a dye is uniformly coated on a surface of expandable polystyrene particles by a Henschel mixer or a ribbon blender.
The pre-expanded colored foamable particles obtained in this manner are pre-expanded to obtain pre-expanded particles. The polystyrene particles are uniformly stirred in an aqueous medium, a foaming agent is press-fitted, an oil-soluble dye or the like is charged, and a colorant is impregnated into the particles to obtain colored foamable polystyrene particles, which are pre-foamed. To obtain pre-expanded particles. In the extruder, the colored foamable polystyrene resin pellets are kneaded with a polystyrene resin, a pigment, and the like, and the colored resin is taken out in a strand shape, cut with a pelletizer, to obtain a colored foamable polystyrene pellet, and prefoamed. To obtain pre-expanded particles. And so on. Then, these pre-expanded pre-expanded particles are filled in a mold and subjected to foam molding.

[0003]

However, in the method, since only the surface of the pre-expanded particles is colored, when a molded article is obtained by using this, when this molded article is cut, the cut surface becomes There were uncolored portions, and color unevenness of the surface portion was liable to occur.
In the method of (1), the coloring agent is impregnated up to the inside of the particles, but is not uniform over the entire surface. In order to uniformly color the coloring agent, a large amount of the coloring agent is used, and the impregnation time of the coloring agent It is necessary to increase the length of time, which may cause contamination of the reaction vessel and the like and contamination of the wastewater, and further reduce the work efficiency. According to the further method, the inside of the colored expandable polystyrene resin pellet is uniformly colored, but color unevenness occurs on the surface of the molded product. This is because when the colored expandable polystyrene resin pellets are pre-expanded, the length direction of the surface of the pre-expanded particles,
The state of the cells differs from that of the cut surface, and the cells of the cut surface become finer, so that color unevenness occurs and the color of the cut surface becomes lighter than the color in the length direction. A molded article obtained by filling the pre-expanded particles into a molding die and foam-forming had uneven color and poor appearance. Further, the darker the color, such as black, the more the color unevenness became clear. In addition, the molded article had poor adhesion between the expanded particles and had many interparticle gaps. The present invention has been made in view of these problems, and an object of the present invention is to provide pre-expanded particles for obtaining a molded article having less color unevenness and almost no particle gap.

[0004]

SUMMARY OF THE INVENTION The present inventors have determined that when the colored pre-expanded particles are filled in the mold, they are oriented along the surface of the mold in the longitudinal direction of the pre-expanded particles. Either the cut surface or the cut surface will be the longer one, and this orientation will be constant, and the longer color direction will be the longer diameter,
By making the cut surface a short diameter, the pre-expanded particles on the mold surface have a high probability that the long diameter is oriented, and it is found that a molded article with less color unevenness can be obtained, and here the present invention is completed. Reached.

The present invention is a particle obtained by pre-expanding expandable polystyrene resin pellets, wherein the ratio of the major axis l to the minor axis d is 1 <l / d ≦ 4. To provide pre-expanded particles. The present invention also provides pre-expanded particles characterized in that expandable polystyrene resin pellets are colored. Further, the present invention provides a colored expandable polystyrene resin pellet, wherein the ratio L / D of the major axis L and the minor axis D of the colored expandable polystyrene resin pellet is 5 to 30.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The pre-expanded particles of the present invention are prepared by ordinary pre-expanding the expandable polystyrene resin pellets in the length direction as a major axis L and a cut surface as a minor axis D, and the pellets are reduced to about Foamed 10 to 50 times, changed long diameter L
Is the major axis 1 of the pre-expanded particles, and the changed minor axis D is the minor axis d of the pre-expanded particles. The ratio of the length of the major axis 1 to the minor axis d was set to 1 <l / d ≦ 4. This ratio is 1 / d
If it is less than 1, the occurrence of color unevenness in the molded article increases, and 1 /
When d is 4 or more, the occurrence of color unevenness is small, but clogging of the filling hole of the molding die causes poor filling, and the occurrence of particle gaps in the molded product tends to occur. Therefore, the major axis l
In consideration of the filling property of the mold, it is preferable that the length of the mold is W ≧ 31, where W is the filling hole of the mold. If W <31, the pre-expanded particles are likely to be clogged in the filling holes.

In order to obtain the pre-expanded particles in the present invention, it is desirable that the ratio L / D of the major axis L to the minor axis D of the colored expandable polystyrene resin pellets is 5 to 30. When the length ratio is less than 5, the pre-expanded particles of the present invention are difficult to obtain when ordinary pre-expansion is performed. The length ratio L / D exceeds 30. And, in the pre-foaming stage, the pellets are too elongated,
The filling hole of the molding die is likely to be clogged, which may cause defective filling. Therefore, at the stage before pre-foaming, the ratio of the length L of the major axis L to the minor axis D of the colored expandable polystyrene resin pellet is in the range of 5 to 30.
It is desirable to sizing.

Next, a method for producing pre-expanded particles of expandable polystyrene resin pellets of the present invention will be described. For example, a polystyrene-based resin containing a volatile foaming agent and, if necessary, a blended resin and a colorant such as a dye or a pigment and other additives were previously uniformly blended with a Henschel mixer or a ribbon blender in advance. Thereafter, the resin is put into an extruder, and after being melted by heating and kneaded by a screw, the resin is extruded from the tip of the die and immediately cooled in a water tank. At this time, care must be taken to cool the resin extruded from the die tip before foaming. Then, the strand is taken up in a strand shape, and then the strand is cut into a desired length L by a rotary pelletizer or the like.
To obtain colored foamable polystyrene resin pellets of

The obtained colored expandable polystyrene resin pellets are prepared by a conventional pre-expansion method by about 10-6.
By setting the bulk ratio to 0, pre-expanded particles having a major axis l and a minor axis d ratio of 1 <l / d ≦ 4 according to the present invention can be obtained. In the production of the pre-expanded particles of the present invention, in order to produce expandable polystyrene resin pellets, as in the extrusion impregnation method, after or during melting of the resin in an extruder, a volatile foaming agent is used. After press-fitting and thoroughly mixing with the resin in the molten state, it is extruded into the form of a strand,
Cool immediately in a water bath. At this time, care must be taken to cool the resin extruded from the die tip before foaming. Thereafter, the strand is cut into L having a desired length with a rotary pelletizer or the like, and the long diameter L is cut.
To obtain an expandable polystyrene resin pellet having a short diameter D.

In the present invention, the pre-expanded particles only need to have a relation of a major axis l and a minor axis d of 1 <l / d ≦ 4, and preferably, expandable polystyrene resin pellets. The ratio L / D of the major axis L and the minor axis D may be 5 to 30 and may be obtained by any manufacturing method. Further, assuming that the diameter of the filling hole of the mold is W, it is preferable that the major diameter l of the pre-expanded particles is in a relationship of 3l ≦ W. If W <3l, the pre-expanded particles are clogged in the filling hole. This is not preferable in terms of workability.

The polystyrene resin referred to in the present invention is not limited to a homopolymer of a styrene monomer, but may be a copolymer with another monomer (a styrene monomer used in a proportion of 50% or more). Made). Accordingly, the styrene resin used in the present invention includes, in addition to polystyrene, polystyrene such as poly-α-methylstyrene and poly-p-chlorostyrene, a copolymer of styrene and a substituted styrene (for example, α-methylstyrene), or styrene and vinyl. Copolymers with a system monomer (for example, acrylonitrile) are exemplified. Further, the polystyrene resin of the present invention can also be a resin obtained by blending a polyphenyl ether resin or a polyolefin resin, a rubber component, or the like with the polystyrene resin, and improving the physical properties of the foamable resin. .

The colorants used in the present invention include inorganic materials such as carbon black, titanium oxide, zinc white, zinc sulfide, antimony oxide, graphite, red iron oxide, ultramarine blue, copper phthalocyanine blue, Hansa There are organic ones such as yellow, piazolone red and permanent bordeaux. In addition, poorly water-soluble pigments are more preferable as colorants in the present invention than water-soluble pigments.

As the volatile foaming agent used in the present invention,
Boiling point at normal pressure is in the range of −30 ° C. to 100 ° C., for example, propane, n-butane, i-butane,
Aliphatic hydrocarbons such as n-pentane, i-pentane, hexane, heptane and the like, and cycloaliphatic hydrocarbons, halogenated hydrocarbons and the like can be used. Two or more of these can be used in combination. The polystyrene-based resin containing the volatile foaming agent in advance may be charged into the extruder, or the volatile foaming agent may be press-fitted after the polystyrene resin or the like is charged into the extruder.

[0014]

By using the pre-expanded particles of the present invention for foam molding, since the pre-expanded particles are uniformly oriented on the surface of the mold when filling the mold, it is possible to obtain a foam molded article having almost no color unevenness. In addition, it is possible to obtain a molded article having few gaps between the foamed particles. In addition, since the ratio of the major axis to the minor axis of the expandable polystyrene resin pellets and the ratio of the major axis to the minor axis of the pre-expanded particles are determined within a certain range, the workability such as the filling property into the molding die is improved. Can be improved.

[0015]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 100 parts by weight of an expandable polystyrene resin containing 10% by weight of n-pentane with respect to the resin, 5 parts by weight of carbon black as a coloring agent, and 0.1 part by weight of zinc stearate were uniformly mixed by a ribbon blender. This mixture was put into the single screw extruder 3 together, and the temperature of the raw material charging section was set to 100
C., the melting portion was set to 140 ° C., the mixture was melted, kneaded with a screw, extruded in a strand shape 6 from a die 4 having a base of 0.8 mm, cooled immediately with water 8, and then taken up in a strand shape 6. The strands were subjected to a rotary type pelletizer 9 to obtain colored foamable polystyrene resin pellets 2 having an average length of 4 mm and an average thickness of 0.4 mm. The obtained expandable polystyrene resin pellets were subjected to a normal pre-expansion method to obtain pre-expanded particles 1 having a major axis of 30 times and a major axis of 3.2 mm and a minor axis of 3.0 mm.

Example 2 In the same manner as in Example 1, expandable polystyrene resin pellets having a major axis of 4.0 mm and a minor axis of 0.4 mm were obtained. 3 mm of pre-expanded particles were obtained.

Comparative Example 1 In the same manner as in Example 1, expandable polystyrene resin pellets having a major axis of 2.3 mm and a minor axis of 0.55 mm were obtained. 5mm
Of pre-expanded particles were obtained.

Comparative Example 2 In the same manner as in Example 1, expandable polystyrene resin pellets having a major axis of 2.0 mm and a minor axis of 0.50 mm were obtained. 5mm
Of pre-expanded particles were obtained.

The pre-expanded particles prepared in each of Examples and Comparative Examples were aged at room temperature for 12 hours, and the diameter of the filling hole was 10 m.
m and a steam pressure (gauge pressure) of 0.
Perform foam molding by heating at 8 kg / cm ^{3 for} 30 seconds.
A foam molded product having a size of 50 mm × 300 mm × 300 mm was produced. The filling property of the pre-expanded particles into the mold, the color unevenness of the molded product, and the particle gap were evaluated. Table 1 shows the results.
Shown in

[0020] Note) 1 in Table 1: major diameter of pre-expanded particles d: minor diameter of pre-expanded particles W: diameter of filling hole of mold

In Examples 1 and 2, since l / d is 1 or more and W> 31, a molded article without color unevenness and with a small particle gap can be obtained. The filling workability was also satisfactory. In Comparative Example 1, although l / d was 1 or more, since W <31, there was no occurrence of color unevenness or the like in the molded product, but there was a problem in the filling property into the molding die. Further, in Comparative Example 2, since l / d was less than 1, color unevenness and particle gap of the molded product occurred, and there was a problem in the quality of the molded product.

[0022]

According to the present invention, since the ratio of the major axis to the minor axis of the pre-expanded particles is specified, the unevenness of the color of the pre-expanded particles is generated on the molding surface of the mold so that the pre-expanded particles have orientation. It is possible to obtain a molded product that hardly occurs and has a small particle gap. By determining the major diameter of the pre-expanded particles according to the size of the filling hole of the mold, it is possible to prevent the occurrence of defective molded products due to defective filling in an automatic molding machine or the like without filling the filled holes with the pre-expanded particles. .

[Brief description of the drawings]

FIG. 1 is a perspective view of pre-expanded particles of an example.

FIG. 2 is a perspective view of a colored expandable polystyrene resin pellet of an example.

FIG. 3 is a production process diagram of a colored expandable polystyrene resin pellet of an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Colored expandable polystyrene resin pellet 2 Pre-expanded particle 3 Extruder 5 Die discharge part 6 Strand 7 Strand take-up roller 8 Water 9 Pelletizer

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI C08L 25:04

Claims (3)

[Claims] 1. A pre-expanded particle obtained by pre-expanding expandable polystyrene resin pellets, wherein the ratio of the major axis l to the minor axis d is 1 <l / d ≦ 4. Expanded particles. 2. The pre-expanded particles according to claim 1, wherein the expandable polystyrene resin pellets are colored. 3. A colored foamable polystyrene resin pellet, wherein the ratio L / D of the major axis L and the minor axis D of the colored foamable polystyrene resin pellet is 5 to 30.