JPH07109374A - Pre-expanded colored styrene resin bead - Google Patents

Abstract

PURPOSE:To obtain a pre-expanded and uniformly colored styrene resin bead providing an expansion molded article having excellent appearance by pre- expanding a colored expandable styrene resin bead produced by an extrusion granulation method and breaking the fine bubbles on the cut surface. CONSTITUTION:A styrene resin, a colorant and a foaming agent are melted and kneaded in an extruder and the produced molten resin composition is extruded with an extruder, cooled and pelletized by cutting the strand to obtain colored expandable styrene resin beads. The pre-expanded colored bead is produced by pre-expanding the expandable styrene resin bead and breaking at least a half of fine bubbles existing on the cut surface of the bead and having diameter of <200mum. The pre-expanded bead is preferably produced by coating the surface of the pelletized colored expandable styrene resin bead with a surface foam breaker and pre-expanding the bead with a heating medium such as steam using a pre-expansion apparatus. The surface foam breaker is preferably hardened soybean oil or liquid paraffin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to colored styrenic resin pre-expanded particles, and more particularly to colored styrenic resin pre-expanded particles which are substantially uniformly colored.
The colored styrenic resin pre-expanded particles are suitable for producing a colored styrenic resin foam-molded article having a good appearance.

[0002]

2. Description of the Related Art A foam molded article obtained by in-mold foam molding of pre-expanded styrenic resin particles has a heat insulating property,
Since it is excellent in cushioning property and lightweight, it is widely used as a heat insulating material, a container, a cushioning packaging material and the like. These foamed molded products are often colored in order to enhance their commercial value. In this case, if the foamed molded product is evenly colored to the inside, it is advantageous that the molded product can be sliced or partially cut before use. Styrene-based resin foam-molded body colored to the inside is obtained by pre-foaming colored expandable styrene-based resin particles with a heating medium such as steam to obtain colored pre-expanded particles. It can be manufactured by

Conventionally, the following methods have been known as a method for producing the colored expandable styrenic resin particles. A method in which a dye or a pigment is dissolved or dispersed in a styrene monomer when the styrene monomer is suspension-polymerized in an aqueous medium, and the foaming agent is impregnated during or after the polymerization. A method of impregnating a styrene resin particle with a dye at the same time when impregnating a foaming agent in an aqueous medium. A method of preparing colored pellets in which pigments, dyes, etc. are kneaded in advance using an extruder, dispersing the pellets in an aqueous medium, and impregnating a foaming agent. At the same time as kneading pigments and dyes into the resin using an extruder, add a foaming agent, extrude in a strand form from the tip of the mold, cool this to a temperature at which the resin does not foam, and cut with a pelletizer to form colored pellets. How to get.

Considering the weather resistance of the colored foamed molded article, it is extremely advantageous to use a pigment as a colorant rather than a dye. From this point of view, the method cannot use a pigment, and the method also makes it extremely difficult to uniformly contain a certain amount or more of the pigment in the resin particles. Therefore, as a method of producing colored expandable styrenic resin expanded particles using a pigment, the method of or is used.

However, the method of preparing colored styrenic resin particles by an extruder and then dispersing the colored resin particles in an aqueous medium and impregnating the foaming agent is economical because the manufacturing process is complicated. Is disadvantageous to Further, when the colored expandable styrenic resin particles after impregnated with the foaming agent are dehydrated and dried, the surface of the resin particles is rapidly densified, so-called whitening phenomenon occurs. It has a very big defect that the whiteness of the surface of the molded product is increased and the color is diluted, and the commercial value of the foamed molded product is significantly reduced.

In order to solve this drawback, the colored expandable styrenic resin particles obtained by the above method are not dehydrated and dried, and are stored until a large amount of attached water remains on the surface of the resin particles until just before foaming. There is a method proposed (Japanese Patent Publication No. 5-11133). According to this method, the above problems are almost solved, but since a large amount of water is attached to the surface of the resin particles, the fluidity of the resin particles is poor, for example, in the raw material feeding hopper of the prefoaming machine, It had the drawback of being difficult to handle during pre-foaming, such as the need to install a special vibration device.

In the case of the colored expandable resin particles obtained by the extruding granulation method, the whitening phenomenon on the surface of the resin particles due to the drying, which is seen in, does not occur. Therefore, it is possible to provide the expandable styrenic resin particles colored in a dry state that are easy to handle. Moreover, since a pressure resistant container for impregnating the foaming agent as described above is not required and the resin can be imparted with foaming performance only by the extruder, it is an advantageous method in industrial production. However, when the colored expandable styrenic resin particles produced by this method are pre-expanded and the in-mold expansion molding is performed using the pre-expanded particles, the surface of the obtained colored expanded molded article has mottled color unevenness. There was a serious problem that it occurred and damaged the commercial value.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention are responsible for the cause of color unevenness occurring on the surface of a styrenic resin foam molded article produced using the colored expandable resin particles obtained by the above extrusion granulation method. As a result of earnest research, this color unevenness
It was found that the resin extruded from the extruder was cut by a pelletizer and granulated.

That is, in the extrusion granulation method, a foaming agent is pressed into the resin in the extruder, extruded in a strand form from the tip of the mold, cooled before the resin containing the foaming agent foams, and cut with a pelletizer. Then, the colored expandable resin particles are obtained by pelletizing. In this cutting step, the cut surface of the extruded strand resin is subjected to shear stress by the cutting blade of the pelletizer, so that only the foaming agent encapsulated in the cut surface portion of the pellet-shaped resin particles is finely dispersed by this stress. Will end up.

Therefore, in the colored pre-expanded particles obtained by pre-expanding the colored expandable resin particles with a heating medium such as steam, the bubble size of the cut surface in which the foaming agent is finely dispersed is the peripheral side surface portion. It will be fine compared to. For example, the average cell diameter of the pre-expanded particles expanded to have a bulk ratio of 40 times is 300 μm or more in the peripheral side surface portion, whereas it is as fine as 10 to 100 μm in the cut surface portion surface layer. When the appearance of the colored pre-expanded particles is observed, the cut surface portion having fine bubbles has a lighter color than the peripheral side surface portion having large bubbles, and the bubbles are fine, so that the cut surface portion has a luster gloss.

During the in-mold foam molding, the pre-expanded particles are filled in the molding die in a state where the peripheral side surface portion and the cut surface portion are in random contact with the inner wall surface of the die. Therefore, the surface of the obtained colored foamed molded article is in a state in which the peripheral side surface portion and the cut surface portion of the colored pre-expanded particles are randomly mixed, and the portion where the peripheral side surface portion is exposed has large and coarse bubbles. The color is deep and vivid, and the part where the cut surface part is visible has a light color due to the fine air bubbles. As a result, on the surface of the colored foamed molded product, "mottled pattern" color unevenness appears as a whole, and the commercial value of the foamed molded product is significantly reduced.

In view of the above, the present invention solves the problems of the prior art and uses the extrusion-granulating colored expandable styrenic resin particles, which are advantageous in industrial production, to achieve uniform coloring without substantial color unevenness. It is an object of the present invention to provide colored styrenic resin pre-expanded particles suitable for producing a colored styrenic resin foamed molded product having a good appearance.

[0013]

That is, the colored styrenic resin pre-expanded particles of the present invention are obtained by melt-kneading a styrenic resin, a colorant and a foaming agent in an extruder and extruding a molten resin composition from the extruder. , Colored pre-expanded styrenic resin particles obtained by cooling and cutting into pellets and pre-expanding with a heating medium, wherein the bubbles are present on the surface of the cut surface of the colored pre-expanded particles. Diameter 200μ
It is characterized in that at least half or more of fine bubbles smaller than m are broken.

The styrene resin used in the present invention includes polystyrene, a mixed resin of polystyrene containing 50% by weight or more of polystyrene and another resin such as polyphenylene oxide, styrene component of 50% by weight or more, and the like. And copolymers of these with polymerizable unsaturated compounds, mixed resins thereof, and modified resins obtained by adding an appropriate amount of a rubber-like substance to these resins. As the copolymerizable unsaturated compound, α-methylstyrene, acrylonitrile, acrylic acid or methacrylic acid and 1
An ester with an alcohol having 1 to 8 carbon atoms, an ester of maleic acid or fumaric acid with an alcohol having 1 to 8 carbon atoms, maleic anhydride and the like are used. Furthermore, a small amount of divinylbenzene, butadiene, polyethylene glycol dimethacrylate or the like may be used as a crosslinking agent.

Suitable blowing agents are organic compounds which have a boiling point not higher than the softening point of the styrenic resin and are in a gaseous or liquid state under normal pressure. Propane, butane, pentane, cyclopentane, cyclopentadiene. , Hydrocarbons such as petroleum ether, halogenated hydrocarbons such as methyl chloride, ethyl chloride, chlorodifluoroethane, 1-fluoro-2-trifluoroethane and difluoroethane, low boiling point ether compounds such as dimethyl ether and dipropyl ether, etc. Used. These foaming agents may be used alone,
You may use 2 or more types together. Although the amount of the foaming agent used varies depending on the desired expansion ratio of the pre-expanded particles, it is usually 2 per 100 parts by weight of the styrene resin.
It is used in an amount of 0 parts by weight or less and about 3 to 10 parts by weight.

[0016] As the colorant in the present invention, carbon black, rouge, copper phthalocyanine pigment, azo pigment and the like are preferably used, but there is no problem such as discoloration and they are well kneaded with the resin in an extruder. If it can be extruded, it is not particularly limited thereto. The amount of the colorant used varies depending on the type of the colorant used, the desired color density of the foamed molded product, and the like.
It is used in the range of 0.1 to 10 parts by weight with respect to 00 parts by weight.

In the present invention, in order to break at least half of the fine bubbles having a cell diameter of less than 200 μm existing on the surface of the cut surface of the colored pre-expanded particles, the resin is added to the surface of the colored expandable styrene resin particles. A particle having a property of slightly eroding the surface of the particle (hereinafter referred to as a surface defoaming agent) is coated and pre-expanded. Such a surface defoaming agent includes fine bubbles formed on the cut surface of the pre-expanded particles when the surface of the colored expandable styrene resin particles is slightly eroded to pre-expand the expandable resin particles. There is no particular limitation as long as it exerts the action of defoaming and eliminating bubbles, but for example, di or triglyceride, sorbitan tri or tetraester, pentaerythritol tetraester, glycool diester, mono. Examples thereof include higher fatty acid esters such as alcohol esters, paraffins such as glycerin dialkyl ethers, polyethers and liquid paraffin. Among these, soybean oil, beef tallow oil, rapeseed oil, and triglycerides such as hydrogenated oils thereof and liquid paraffin are preferably used. These surface defoaming agents may be used alone or in combination of two or more kinds. In particular, hydrogenated soybean oil and liquid paraffin are preferably used.

This surface defoaming agent is a cut surface of colored pre-expanded particles which causes color unevenness in view of maintaining the foam moldability of the pre-expanded particles in the mold and the appearance and strength of the resulting foam-molded article. It is desirable that only the fine bubbles formed on the surface are broken and the bubbles inside the cut surface and the bubbles on the peripheral side surface are not affected as much as possible, and it is 0 with respect to 100 parts by weight of the expandable resin particles. It is used in the range of 0.01 to 1.0 part by weight, more preferably in the range of 0.03 to 0.5 part by weight. If the amount of the surface defoaming agent used is less than 0.01 part by weight, a sufficient defoaming effect cannot be exhibited, while 1.0
When it exceeds the weight part, the obtained foamed molded article shrinks, the appearance is deteriorated and the strength is also reduced.

Whether or not the surface-foaming agent has the effect of eliminating the color unevenness on the colored foamed molded article is determined by applying the surface-foaming agent to the surface of the colored expandable resin particles and then prefoaming with steam.
It can be easily confirmed by observing the appearance state of the obtained pre-expanded particles. It can be judged that there is an effect of eliminating color unevenness if the “luster” luster of the cut surface of the colored pre-expanded particles disappears and the color tone is equivalent to that of the peripheral side surface. If "teteteka" luster remains on the cut surface of the colored pre-expanded particles, the effect of eliminating color unevenness cannot be expected.

When at least half of the fine air bubbles having a diameter of less than 200 μm existing on the cut surface of the colored pre-expanded particles are broken, the “luster” luster of the cut surface disappears and the color tone of the cut surface is reduced. Has substantially the same color tone as the peripheral side surface having relatively large bubbles. The colored styrenic resin pre-expanded particles of the present invention can be produced, for example, by the method described below.

First, the above-mentioned styrene resin, colorant, foaming agent and, if necessary, additives such as inorganic or organic fillers, antioxidants, ultraviolet absorbers and flame retardants are heated in an extruder. After melt-kneading, the resin composition is extruded in a strand form from the tip of the mold and simultaneously cooled to a temperature at which the resin composition extruded with a cooling medium such as water does not foam. Next, this strand is cut with a pelletizer to obtain pelletized colored expandable styrenic resin particles having a desired size.

Next, the surface of the colored expandable styrenic resin particles is coated with the above surface-breaking agent. The expandable styrenic resin particles coated with the surface defoaming agent are pre-expanded with a heating medium such as steam using a pre-expanding device. In the surface coating treatment, other surface treatment agents added for the purpose of preventing bonding during pre-foaming, promoting fusion during foam molding, and preventing static electricity may be used in combination. It is preferable that the surface-foaming agent is coated on the expandable resin particles before the pre-foaming from the viewpoint of workability, but the surface-foaming agent is coated in the pre-foaming device during the pre-foaming. You can also

Thus, the colored styrenic resin pre-expanded particles of the present invention are obtained in which at least half of the fine bubbles having a cell diameter of less than 200 μm existing in the cut surface of the pre-expanded particles are broken. The colored styrenic resin pre-expanded particles of the present invention are substantially filled by filling the same in a mold of a foam molding machine, heating them with steam to expand the expanded particles, and fusing the particles to each other to perform foam molding in the mold. It is possible to produce a colored styrene-based resin foam-molded article that is uniformly colored with no color unevenness, has a good appearance, and has excellent commercial value.

[0024]

EXAMPLES Next, the present invention will be described more specifically by way of examples. However, the technical scope of the present invention is not limited to these examples. Molded bodies molded using the pre-expanded particles obtained in each example are shown as reference examples.

In the following examples, the surface breakage rate was calculated as follows. D (%) = (B−C) / B × 100 D: Surface foam breaking ratio B: Number of fine bubbles existing on the surface of the cut surface of the non-foaming treated colored pre-expanded particles C: After foam breaking treatment The number of fine bubbles present on the cut surface of the colored pre-expanded particles * For B and C, the cut surface of the pre-expanded particles expanded with a kaki magnification of 40 times was magnified 75 times with a scanning electron microscope. Then, the diameter of bubbles existing within 1 mm ² is 200
The number of bubbles less than μm was measured. [Example 1] 95 parts by weight of styrene resin particles (MI value 4.1), 5 parts by weight of carbon black, and 0.1 parts by weight of talc were heated and melted and kneaded by using a uniaxial extruder (caliber 90 mm), and at the same time. While pressing 10 parts by weight of pentane into the extruder as a foaming agent, it is extruded in the form of a strand from a nozzle at the tip of the mold, and the strand is introduced into a water tank and immediately quenched, cut into pellets by a rotary pelletizer and formed into a columnar shape. Expandable styrene resin particles colored in black (particle length L = 3 to 4 mm, particle diameter D = 0.5 to 0.7 m)
m) was obtained.

Using a tumbler, 0.2 parts by weight of hardened soybean oil fine powder as a surface defoaming agent and 0.1 part by weight of zinc stearate as a binding inhibitor at the time of pre-expansion were added to the above black expandable styrene resin particles. And coated. Then, the surface-treated black expandable resin particles were pre-expanded by heating with steam in a small batch type pre-expansion device equipped with a stirrer to obtain black pre-expanded particles having a kaki magnification of 40 times. When the appearance of the obtained black pre-expanded particles was observed, the glossy luster on the surface of the cut surface of the pre-expanded particles had disappeared, and the color tone was almost the same as the peripheral side surface of the pre-expanded particles. The surface breakage rate of the cut surface of the black pre-foamed particles was 92%, and most of the fine bubbles existing on the surface of the cut surface were broken and disappeared. The bubbles (bubble diameter of about 250 to 400 μm) were hardly broken.

Reference Example 1 The pre-expanded black styrene resin particles of Example 1 were aged for 24 hours, and then in-mold foaming was performed using an ACE-3 type bead foam molding machine manufactured by Sekisui Koki Mfg. Co., Ltd. Molded. The mold cavity size is 400 ×
300 × 100 mm, heated steam 0.8 kg / cm
^The pressure was adjusted to ² . The black foamed molded product obtained was colored in black substantially uniformly without uneven color, and had a good molded appearance without shrinkage.

[Example 2] Black styrene resin prefoaming was carried out in the same manner as in Example 1 except that the amount of the hardened soybean oil fine powder added was changed from 0.2 parts by weight to 0.1 parts by weight. Particles were prepared and evaluated. The black pre-expanded particles obtained had almost no "luster" luster on the surface of the cut surface, a surface breakage rate of 84%, and relatively large major bubbles on the peripheral side surface. It wasn't broken.

Reference Example 2 Using the black pre-expanded particles of Example 2, in-mold foam molding was carried out in the same manner as in Reference Example 1 to obtain a black foam molded article. The black foamed molded product obtained was colored in black substantially uniformly without uneven color, and had a good molded appearance without shrinkage. [Example 3] Black styrene resin pre-expanded particles were produced in the same manner as in Example 1 except that the amount of hardened soybean oil fine powder added was changed from 0.2 parts by weight to 0.05 parts by weight. And evaluated. The black pre-expanded particles obtained had almost no "luster" luster on the surface of the cut surface, a surface breakage rate of 61%, and relatively large major bubbles on the peripheral side surface. It wasn't broken.

Reference Example 3 Using the black pre-expanded particles of Example 3, a black foam molded article obtained by in-mold foam molding in the same manner as in Reference Example 1 was obtained in Reference Example 1 and Reference Example 2. Compared with the black foamed molded product, although slight color unevenness was observed, it was colored almost uniformly in black and had a good molding appearance without shrinkage.

[Example 4] In Example 1, hardened soybean oil fine powder as a surface defoamer was mixed with liquid paraffin (specific gravity 0.875 <15 ° C>, viscosity 42.9 cSt <42).
C.) was used, and black styrene resin pre-expanded particles were produced and evaluated in the same manner as in Example 1. In the same manner as in Example 1, the black pre-expanded particles obtained had the "lustered" luster on the surface of the cut surface disappeared, and the surface foaming ratio was 96%.
However, the relatively large main bubbles on the peripheral side surface were hardly broken.

Reference Example 4 Using the black pre-expanded particles of Example 4, a black foam molded article obtained by in-mold foam molding in the same manner as in Reference Example 1 was the black foam obtained in Reference Example 1. Similar to the molded product, it was colored uniformly in black with no color unevenness and had a good molded appearance without shrinkage.

Example 5 Example 1 was repeated except that the amount of liquid paraffin used was changed to 0.1 part by weight.
Produce black styrene resin pre-expanded particles in the same manner as
evaluated. As in Example 1, the black pre-expanded particles thus obtained lost the "glazed" luster on the surface of the cut surface, and the surface rupture rate was 86%, indicating that the peripheral side surface had a relatively large main component. Most of the bubbles were not broken.

[Reference Example 5] The black pre-expanded particles of Example 5 were used to carry out in-mold foam molding in the same manner as in Reference Example 1 to obtain the black foam molded article obtained in Reference Example 1. Similar to the molded product, it was colored uniformly in black with no color unevenness and had a good molded appearance without shrinkage.

[Example 6] Black styrene resin pre-expanded particles were produced in the same manner as in Example 1 except that the hardened soybean oil fine powder was changed to rapeseed oil and the addition amount was changed to 0.1 part by weight. And evaluated. The obtained black pre-expanded particles had almost no "luster" luster on the surface of the cut surface, had a surface breakage rate of 80%, and had relatively large major bubbles on the peripheral side surface. It wasn't broken.

Reference Example 6 Using the black pre-expanded particles of Example 6, in-mold foam molding was carried out in the same manner as in Reference Example 1 to obtain a black foam molded body. The black foamed molded product obtained was colored in black substantially uniformly without uneven color, and had a good molded appearance without shrinkage. [Example 7] Blue styrene resin pre-expanded particles were produced and evaluated in the same manner as in Example 1 except that the pigment added was changed from carbon black to copper phthalocyanine. The obtained blue pre-expanded particles have almost disappeared the luster of the surface of the cut surface,
The surface bubble breaking rate was 87%, and the relatively large main bubbles on the peripheral side surface were hardly broken.

Reference Example 7 Using the blue pre-expanded particles of Example 7, in-mold foam molding was carried out in the same manner as in Reference Example 1 to obtain a blue foam molded body. The blue foamed molded product thus obtained had a substantially uniform coloring in blue with no color unevenness and had a good molding appearance without shrinkage. [Example 8] Example 1 except that the amount of carbon black added was changed from 5 parts by weight to 3 parts by weight.
Produce black styrene resin pre-expanded particles in the same manner as
evaluated. The black pre-expanded particles obtained had almost no "glossy" luster on the surface of the cut surface, and had a surface breakage rate of 89%, with relatively large major air bubbles on the peripheral side surface. It wasn't broken.

Reference Example 8 Using the black pre-expanded particles of Example 8, in-mold foam molding was carried out in the same manner as in Reference Example 1 to obtain a black foam molded article. The black foamed molded product obtained was colored in black substantially uniformly without uneven color, and had a good molded appearance without shrinkage. Comparative Example 1 Black styrene resin pre-expanded particles were produced and evaluated in the same manner as in Example 1 except that the hardened soybean oil fine powder was not added. The obtained black pre-expanded particles had a cut surface portion covered with fine bubbles having a bubble diameter of about 10 to 100 μm, and had a “glossy” luster. The surface defoaming rate was 0%.

Using the black pre-expanded particles, Reference Example 1
In the same manner as in, the surface of the black foam molded article obtained by in-mold foam molding had a marked mottled pattern of color unevenness. Comparative Example 2 Black styrene resin pre-expanded particles were produced in the same manner as in Example 1 except that the amount of hardened soybean oil fine powder added was changed from 0.2 parts by weight to 2.0 parts by weight. And evaluated. The obtained black pre-expanded particles had lost the “luster” luster on the surface of the cut surface, had a surface breakage rate of 100%, and did not have fine bubbles on the cut surface. However, relatively large main cells (cell diameter of about 250 to 400) on the peripheral side surface of the pre-expanded particles are used.
μm), the foam breaking effect of the foam breaking agent excessively acted, and a large number of foam breakings were observed.

Using this black pre-expanded particles, Reference Example 1
A black foam molded article obtained by in-mold foam molding in the same manner as
It was uniformly colored black. However, the surface condition of the foamed molded product was poor, so-called "elongation" was poor, and the shrinkage immediately after foaming was large, and even when the foamed molded product was aged, the shrinkage of the molded product was not completely recovered. . [Comparative Example 3] Black styrene resin pre-expanded particles were produced in the same manner as in Example 1 except that the amount of hardened soybean oil fine powder added was changed from 0.2 parts by weight to 0.005 parts by weight. And evaluated. The obtained black pre-expanded particles had a "lustered" luster on the surface of the cut surface, and the surface rupture rate was 10%.

Using the black pre-expanded particles, Reference Example 1
In the same manner as in, the surface of the black foam molded article obtained by in-mold foam molding had a marked mottled pattern of color unevenness. Table 1 shows the evaluation results of the above Examples 1 to 8, Reference Examples 1 to 8 and Comparative Examples 1 to 3.

[0042]

[Table 1]

[0043]

EFFECT OF THE INVENTION In the colored styrenic resin pre-expanded particles of the present invention, more than half of the fine bubbles existing on the surface of the cut surface are broken and disappeared. The "glossy" luster disappears, and the color of the cut surface becomes the same as that of the peripheral side surface.

The colored styrenic resin pre-expanded particles of the present invention can be formed into a foam-molded article by a usual in-mold foam-molding method.
It is possible to obtain a colored styrene-based resin foam-molded article which is substantially uniformly colored and has a good appearance and which is excellent in commercial value with substantially no color unevenness.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 25:06

Claims (1)

[Claims] 1. Colored expandable styrenic resin particles obtained by melt-kneading a styrene resin, a colorant and a foaming agent in an extruder, extruding a molten resin composition from the extruder, cooling and cutting into pellets. Colored pre-expanded particles obtained by pre-expanding with a heating medium, wherein at least half or more of fine bubbles having a diameter of less than 200 μm existing on the surface of the cut surface of the colored pre-expanded particles are broken. Pre-expanded particles of colored styrenic resin, characterized in that