JPH07173320A - Primarily expanded polystyrene particle excellent in moldability and its production - Google Patents

Abstract

PURPOSE:To obtain an expanded particle, containing a specific foam regulator and a readily volatile foaming agent in respective small proportions in polystyrene, primarily expanded to a specific bulk ratio and a specified average cell diameter without using an organic solvent, etc., and causing mutual coalescence thereof. CONSTITUTION:This particle is obtained by comprising 0.001-0.01 pt.wt. foam regulator expressed by the formula [(n) is 10-20] and 0.056-0.16mol% readily volatile foaming agent (preferably having -30 to +50 deg.C boiling point, e.g. butane, pentane, monochlorodifluoroethane or tetrafluoroethane) in 100 pts.wt. polystyrene and then expanding the resultant mixture under 0.4-1.5kg/cm<2> gauge vapor pressure. The resultant particle has 100-300 times bulk ratio and 0.05-0.3mm average cell diameter.

Description

Detailed Description of the Invention

[0001]

The present invention has a bulk ratio of 100 to 30.
The present invention relates to a polystyrene primary expanded particle which is highly expanded to 0 times and has excellent moldability, and a method for producing the same.

[0002]

2. Description of the Related Art Polystyrene foam molded articles are made of expandable polystyrene particles containing a foaming agent as raw materials, heated to obtain primary expanded particles, and then filled in a mold and heated with steam or the like. By doing so, a foamed molded product having a desired shape can be obtained. Conventionally, such foamed molded articles having an expansion ratio of several times to about 80 times have been appropriately used according to the application, but recently, cushioning packaging materials, heat insulating materials, float materials, cut products of blocks, etc. In the field of (1), higher expansion ratio has been demanded. In order to obtain a highly foamed molded product, even if the foamed molding is performed by simply using the primary expanded particles having an increased primary expansion ratio, the resulting molded product has a large shrinkage, and the fusion strength between the particles is high. You can only get a low price.

In response to the demand for these highly foamed molded products, there is a technique of using a styrene-acrylonitrile resin which is one of the styrene resins and which is easily foamed.
However, as resource saving and recycling are promoted, these styrene-acrylonitrile resin products are almost indistinguishable from polystyrene products in appearance, and workers are easily confused with each other. There was a problem that the acrylonitrile resin was mixed. Thus, the recovered raw material in which polystyrene and styrene-acrylonitrile-based resin are mixed has almost no utility value, and thus there is still a strong demand for a polystyrene high-foam molded article.

As a method for obtaining highly expanded polystyrene resin particles, for example, in JP-A-61-195135, a specific amount of a specific foaming agent is used, and the expanded particles are highly foamed once and then expanded. A method for obtaining highly expanded styrene resin particles by spontaneous recovery is disclosed. According to this method, styrene-based resin foam particles highly expanded 100 to 300 times can be obtained. Further, the foam particles obtained by this method can be used as a cushioning material and a heat insulating material by directly filling the gaps and the like, but on the other hand, for polystyrene, that is, a homopolymer of polystyrene, a conventionally known cell adjustment is performed. When an agent, for example, talc is used, the bubbles become too fine and the expansion ratio does not rise easily, and even if foam molding is performed, the obtained molded product has large shrinkage and low fusion strength between particles. I could only get things.

Further, as a method for obtaining a highly foamed molded article of polystyrene, in JP-A-63-182353, a specific foaming agent and an organic solvent are used in combination to perform primary foaming at a high ratio and then shrink. There is disclosed a method of recovering a material and then subjecting it to foam molding to obtain a polystyrene high-foam molded article. However, in this method, it is possible to easily expand polystyrene by using an organic solvent, on the other hand, it is easy to cause a phenomenon in which foamed particles are coalesced during primary foaming, especially by increasing the vapor pressure. This phenomenon is likely to occur in the case of primary foaming. Primary expanded particles containing these coalesced particles do not sufficiently shrink and recover after primary expansion,
Therefore, good foam molding cannot be performed. In addition, when used as a cushioning material, there is a risk that this organic solvent may migrate to the packaged object.

In view of such a current situation, the present inventors have
As a result of diligent investigations, polystyrene foamed particles that have been primary expanded to a size of 0 to 300 times can be efficiently obtained without causing coalescence, and the obtained expanded particles have excellent moldability. When the primary foaming is performed 100 to 300 times, a specific amount of a foaming agent and a specific foam regulator are used in combination within a specific range so that the foam diameter of the foam is in a specific range. By the primary foaming with the vapor pressure of, it is possible to highly foam without using an additive such as an organic solvent, primary foamed particles exhibiting excellent moldability are obtained, and the resulting primary foamed particles are left to stand naturally. As a result, it was found that the bulk ratio before shrinkage was almost recovered, and the present invention was completed.

[0007]

That is, according to the present invention, the following general formula (1) is used with respect to 100 parts by weight of polystyrene.
Compound shown by

[Chemical 3] 0.001 to 0.01 part by weight, and a volatile foaming agent 0.
It contains 056 to 0.16 mol% and has a bulk ratio of 1
0.00 to 300 times, the average cell diameter is from 0.05 to 0.3 mm, and the easily volatile foaming agent is added to 100 parts by weight of polystyrene primary expanded particles having excellent moldability, which are characterized by having an average cell diameter of 0.05 to 0.3 mm. Compounds represented by the following general formula (1)

[Chemical 4] Of 0.001 to 0.01 part by weight, and then the expandable polystyrene particles obtained were 0.4 kg / g at a gauge pressure.
0.001 of the above compound, characterized in that foaming is carried out using pressurized steam of not less than cm2 and less than 1.5 kg / cm2.
-0.01 parts by weight and easily volatile foaming agent 0.056-0.1
A gist of the present invention is a method for producing polystyrene primary expanded beads which contains 6 mol%, has a bulk ratio of 100 to 300 times, and an average cell diameter of 0.05 to 0.3 mm and is excellent in moldability.

The polystyrene used in the present invention is a homopolymer of styrene monomer, and the polymerization method may be either suspension polymerization from styrene monomer or nuclear polymerization. Further, by adding a required amount of a cell regulator during the polymerization, polystyrene particles uniformly containing the cell regulator can be obtained.

The easily volatile foaming agent contained in the polystyrene in the present invention is an aliphatic hydrocarbon, a halogenated hydrocarbon or the like, alone or in a mixture of two or more kinds.
Specific examples of the aliphatic hydrocarbon include propane and n
-Butane, isobutane, n-pentane, isopentane,
Cyclopentane, etc. are mentioned. In addition, as specific examples of the halogenated hydrocarbon, for example, trichloromonofluoromethane, dichlorodifluoromethane, monochlorotrifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, dichlorotrifluoroethane, Examples thereof include monochloropentafluoroethane, monochlorotetrafluoroethane, monochlorotrifluoroethane, monochlorodifluoroethane, tetrafluoroethane, difluoroethane and the like. Above all,
Foaming agents having a boiling point of -30 to 50 ° C., such as butane, pentane, monochlorodifluoroethane, tetrafluoroethane, etc., are particularly preferable because a foam having a high magnification can be easily obtained.

The expandable polystyrene particles used in the present invention are prepared by a suspension impregnation method in which an easily volatile foaming agent is impregnated in an aqueous suspension, or by melting polystyrene by using an extruder. It can be obtained by using a known method such as extrusion impregnation method in which the compound is pressed and kneaded, discharged from a nozzle having a desired shape, rapidly cooled with water and cut in an unfoamed state. After the foaming agent is contained in polystyrene by these methods, the amount of the foaming agent contained in the expandable polystyrene particles at the time of primary foaming after dehydration, drying and aging in a cool dark place is 100 parts by weight of polystyrene. 0.08 ~
It should be 0.16 mol%. In order to include the above-mentioned amount of the foaming agent in the expandable polystyrene particles at the time of primary foaming, the foaming agent may be scattered during aging in a dehydrated, dried, and cool dark place. It is necessary to increase the impregnated amount of. Further, when the amount of the foaming agent contained in the expandable polystyrene particles is less than 0.08 mol%, it becomes difficult to foam at a foaming ratio of 100 times or more,
On the other hand, if it exceeds 0.16 mol%, the foaming agent cannot be uniformly dispersed in polystyrene, and primary foamed particles having a non-uniform cell size are likely to be formed, which is not preferable.

The expandable polystyrene particles used in the present invention include organic sulfur compounds represented by the following general formula (1).

[Chemical 5] For example, dilauryl 3,3-thiodipropinate, dimyristyl 3,3-thiodipropinate, distearyl 3,3-thiodipropinate, etc. may be used as polystyrene 100
It is necessary to contain 0.001 to 0.01 parts by weight with respect to parts by weight. These organic sulfur-based compounds are generally used as antioxidants, but in the present invention, the above-mentioned specific amount of the foaming agent and an extremely small amount of this organic sulfur-based compound are used in combination as a bubble control agent. Since it is possible to adjust to the optimum cell diameter, it is possible to obtain highly expanded primary particles and to obtain expanded particles having a specific cell diameter. The obtained primary expanded beads have excellent moldability, and a highly expanded molded product can be obtained. In addition, since the highly expanded particles of the present invention do not contain an organic solvent, there is no possibility that the expanded particles will adhere to each other during the primary expansion.

The organic sulfur compound used in the present invention is used as a cell regulator, and if it is less than 0.001 part by weight, the average cell diameter which is the upper limit of the optimal cell diameter is 0.3 m.
It is not preferable because bubbles larger than m are formed and the moldability is deteriorated. On the other hand, when the content of the organic sulfur compound is more than 0.01 part by weight, the average cell diameter becomes too finer than 0.05 mm, and the primary expansion ratio can be expanded up to about 160 times at most. Is not preferable because the shrinkage does not recover to the bulk ratio before shrinkage, and therefore the moldability remarkably deteriorates.

Examples of the method for adding the organic sulfur compound include, for example, a method of adding during the suspension polymerization and the nuclear polymerization impregnation, a method of pelletizing polystyrene into particles using an extruder, or a time of the extrusion impregnation. The method of adding to and mixing with is preferably used, and even a very small amount can be uniformly dispersed.

When talc, which is conventionally used as a cell regulator, is used, it is difficult to disperse the talc uniformly, even if it is added in an extremely small amount, for example, 0.01 parts by weight. Therefore, the obtained primary expanded beads are likely to have unevenness of expansion, and such primary expanded beads have poor foam moldability. On the other hand, organic sulfur compounds used in the present invention, for example, dilauryl 3,3
-Thiodipropinate can be melted at a relatively low temperature of about 37 ° C, and even if the addition amount is very small, particles can be obtained during suspension polymerization, nuclear polymerization impregnation, or by using an extruder. It can be melted and uniformly dispersed in polystyrene when pelletized.

In the present invention, the primary expansion of expandable polystyrene particles by 100 to 300 times is carried out by directly heating with steam having a gauge pressure of 0.4 kg / cm 2 or more and less than 1.5 kg / cm 2. Need to foam. This is 1 when the vapor pressure is less than 0.4 kg / cm 2.
It takes a long time to expand the foam by more than 00 times, and as a result, the amount of the foaming agent dissipated during the primary foaming increases and the amount of the residual foaming agent contained in the obtained primary foamed particles becomes too small, resulting in moldability. This is because it gets worse. On the other hand, the vapor pressure is 1.5 kg
Above / cm2, air bubbles tend to break during primary foaming,
In particular, in the case of a high polystyrene foam as in the present application, the cell membrane is thin and its influence is large, and primary foamed particles having good moldability cannot be obtained, which is not preferable. Also, the heating time is
Depending on the amount of foaming agent contained in the expandable styrenic resin,
Although it is selected according to the target expansion ratio, it is preferably within 150 seconds in order to prevent the foaming agent from escaping as much as possible.

The amount of the foaming agent contained in the heat-expanded polystyrene primary expanded particles is 70% or more of the amount of the foaming agent contained in the expandable polystyrene particles during the primary expansion. It is particularly preferable because of its excellent properties. That is, since the amount of the foaming agent contained in the expandable polystyrene particles is 0.08 to 0.16 mol% with respect to 100 parts by weight of polystyrene, the amount of the volatile foaming agent in the primary expanded polystyrene particles is 0.056-
It is in the range of 0.16 mol%. In order to control the amount of the residual volatile blowing agent in the primary expanded polystyrene particles within this preferable range, direct heating is performed using a steam pressure of 0.4 kg / cm2 or more and less than 1.5 kg / cm2. Need to foam.

[0017]

EXAMPLES Next, the present invention will be described more specifically by way of examples. Example 1 When obtaining pearl-like polystyrene by suspension polymerization, 0.001 part by weight of dilauryl 3,3-thiodipropinate as a cell adjuster was added to 100 parts by weight of polystyrene, and the average particle size was 0.5 mm. To obtain pearl-like polystyrene. This pearl-like polystyrene has n as a foaming agent.
-Using 0.20 mol% of pentane, the foaming agent was impregnated at a temperature of 100 ° C for about 5 hours to obtain expandable polystyrene particles containing 0.15 mol% of n-pentane. The expandable polystyrene particles were dehydrated and dried, and then aged in a cool box for about 7 days to obtain expandable polystyrene particles containing 0.11 mol% of n-pentane. Next, the expandable polystyrene particles obtained were subjected to primary expansion with a vapor pressure (gauge pressure) of 0.9 kg / cm 2. The primary expanded beads were once shrunk and many wrinkles were visually observed on the particle surface, but when left naturally for about 2 days, the wrinkles on the particle surface disappeared and the particles shrank and recovered. Table 1 shows the expansion ratio, the average cell diameter, and the content of the foaming agent of the primary expanded particles that have recovered by shrinking.

The primary expanded particles which have been recovered by shrinkage are filled in a mold of 300 × 400 × 50 mm having steam holes, and 1.0 k
The moldability was evaluated by foam molding at a vapor pressure (gauge pressure) of g / cm 2. The results are shown in Table 1.

[0019]

[Table 1] (1) Moldability was evaluated by the fusion property and shrinkage property of the molded body. (2) The evaluation of the fusion property is the ratio of the number of particles torn inside the foamed particles, not to those separated at the boundary surface between the foamed particles, in the fracture surface when the molded body is torn. However, 80% or more was evaluated as ◯, and less than 80% was evaluated as x. (3) The shrinkage is evaluated by measuring the shrinkage ratio of the molded product with respect to the die size, and the dimensional shrinkage ratio is 1% or less as ◯, the dimensional shrinkage ratio exceeds 1% and 5% or less as Δ, and the dimensional shrinkage ratio is When the percentage exceeds 5%, it is defined as x.

Example 2 Primary expanded particles were obtained in the same manner as in Example 1 except that 0.005 parts by weight of dilauryl 3,3-thiodipropinate was added as a cell regulator. The obtained primary expanded beads were once shrunk and many wrinkles were visually observed on the particle surface, but when left naturally for about 2 days, the wrinkles on the particle surface disappeared and the particles shrank and recovered. The moldability of the primary expanded particles that have recovered by shrinkage was evaluated, and the results are shown in Table 2.

[0021]

[Table 2]

Comparative Example 1 Primary expanded particles were obtained in the same manner as in Example 1 except that 0.015 parts by weight of dilauryl 3,3-thiodipropinate was added as a cell regulator. The obtained primary expanded particles once contracted, and many wrinkles were visually observed on the surface of the particles. Although it was naturally left for about 2 days, wrinkles on the surface of the particles were not eliminated, and in particular, the primary expanded beads whose heating time for primary expansion was 30 seconds had many wrinkles left on the surface of the particles. Then, the moldability was evaluated, and the results are shown in Table 3.

[0023]

[Table 3]

Comparative Example 2 Primary expanded particles were obtained in the same manner as in Example 1 except that no cell regulator was added. The obtained primary expanded beads were once shrunk and many wrinkles were visually observed on the particle surface, but when left naturally for about 2 days, the wrinkles on the particle surface disappeared and the particles shrank and recovered. The moldability of the primary expanded particles that had been recovered by shrinkage was evaluated, and the results are shown in Table 4.

[0025]

[Table 4]

Example 3 Using an extruder equipped with a nozzle die at the tip, 0.006 parts by weight of distearyl 3,3-thiodipropinate as a foam control agent was added to 100 parts by weight of polystyrene to form a strand. It was extruded, cooled in water in line, and then cut to obtain pellet-shaped polystyrene particles having a diameter of 0.9 mm and a length of 1.0 mm. To these polystyrene particles,
Using butane 0.22 mol% as a blowing agent, the temperature is 8
The foaming agent was impregnated at 5 ° C. for about 5 hours to obtain expandable polystyrene particles containing 0.15 mol% of butane. The expandable polystyrene particles were dehydrated, dried, and then aged in a cool box for about 5 days to obtain expandable polystyrene particles containing 0.10 mol% of butane. The expandable polystyrene particles obtained were subjected to primary expansion by changing the vapor pressure (gauge pressure) within the range of 0.5 to 1.2 kg / cm 2. The obtained primary expanded beads were once shrunk and many wrinkles were visually observed on the particle surface, but when left naturally for about 2 days, the wrinkles on the particle surface disappeared and the particles shrank and recovered. Table 5 shows the expansion ratio, the average cell diameter, and the content of the foaming agent of the primary expanded particles that have recovered by shrinking.

Next, the shrinkage-recovered primary expanded particles were filled in a mold of 300 × 400 × 50 mm having steam holes, and 1.
The moldability was evaluated by foam molding at a vapor pressure (gauge pressure) of 0 kg / cm @ 2, and the results are shown in Table 5.

[0028]

[Table 5]

Comparative Examples 3 and 4 The expandable polystyrene particles obtained in Example 3 were primarily expanded at vapor pressures (gauge pressures) of 0.3 and 1.5 kg / cm 2, respectively, to obtain primary expanded particles. . The obtained primary expanded particles once contracted, and many wrinkles were visually observed on the surface of the particles. 0.3kg / c if left for 2 days
The primary foamed particles that were primary-foamed with a vapor pressure of m2 disappeared from the wrinkles on the surface of the particle and contracted and recovered, but 1.5 kg / cm2
The primary foamed particles that had been primary-foamed with the vapor pressure of No. 1 had some wrinkles on the particle surface. Next, the moldability was evaluated, and the results are shown in Table 6.

[0030]

[Table 6]

[0031]

As described above, according to the present invention, the expandable polystyrene particles obtained by adjusting the specific amount of the easily volatile foaming agent and the specific bubble controlling agent in the specific range and using them together are used under the vapor pressure of the specific conditions. By performing the primary expansion to a high degree of 100 to 300 times, the polystyrene primary expanded particles having excellent moldability can be obtained. Since the polystyrene primary expanded beads having excellent moldability can be easily molded into a highly foamed molded body of 100 to 300 times, there is an effect that a foamed molded body can be efficiently obtained. Further, according to the present invention, since the foaming can be performed to a high degree without using an additive such as an organic solvent, there is no possibility that the primary expanded particles will adhere to each other.

Claims (2)

[Claims] 1. A compound represented by the following general formula (1) with respect to 100 parts by weight of polystyrene: 0.001 to 0.01 part by weight, and a volatile foaming agent 0.
It contains 056 to 0.16 mol% and has a bulk ratio of 1
A primary expanded polystyrene particle having excellent moldability, which is characterized by having an average cell diameter of 0.00 to 300 times and an average cell diameter of 0.05 to 0.3 mm. 2. A volatile blowing agent of 0.08 to 0.16 mol% relative to 100 parts by weight of polystyrene, and a compound represented by the following general formula (1): Of 0.001 to 0.01 part by weight, and then the expandable polystyrene particles obtained were 0.4 kg / g at a gauge pressure.
0.001-0.01 of the above compound, characterized in that foaming is carried out at a vapor pressure of not less than cm2 and less than 1.5 kg / cm2.
Polystyrene primary containing parts by weight and easily volatile foaming agent 0.056 to 0.16 mol%, and having a bulk ratio of 100 to 300 and an average cell diameter of 0.05 to 0.3 mm and excellent moldability Method for producing expanded beads.