JPH07179648A - Production of high-expansion-ratio styrene resin foam - Google Patents

Abstract

PURPOSE:To produce a resin foam while attaining the shortening of the production time, the reduction of the area necessary for storage, the production efficiency, etc., by thermally expanding an expandable styrene resin to a specified bulk expansion degree, shrinking the resin by cooling, re-expanding the resin to the initial bulk expanding degree in a carbon dioxide atmosphere and expanding the last resin. CONSTITUTION:100 pts.wt. styrene resin (e.g. polystyrene) being a homo-or co-polymer of a styrene monomer and containing a blowing agent comprising at least one selected from among aliphatic and halohydrocarbons, etc., is mixed with 0.001-0.01wt.% organosulfur compound as a cell modifier and optionally a solvent, a flame retardant, etc., and the resulting mixture is subjected directly to thermal expansion in one or more stages, or is subjected to primary expansion under a gauge pressure of below 0.5kg/cm<2> in the presence of an organic solvent to a bulk expansion degree of 100-350, and is shrunk by cooling in air to obtain the shrunk particles of the primary expansion, which are then reexpanded to the initial expansion degree in an atmosphere containing at least 50% carbon dioxide to obtain particles of primary expansion having a bulk expansion degree of 90-350, which in turn are packed into a mold and expansion-molded by heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a bulk ratio of 100 to 350.
The present invention relates to a method for producing a highly foamed styrene-based resin molded product, which comprises foaming and molding after shrinking primary highly foamed particles that have been double-heated and foamed and then once shrunk in the air, are recovered in a carbon dioxide gas atmosphere.

[0002]

2. Description of the Related Art Foaming styrenic resin particles containing a foaming agent are used as a raw material to obtain primary expanded particles by heating the particles, which are then filled in a molding die and steam-heated to obtain a desired shape. To obtain a foamed molded product. Conventionally, as such a foamed molded product, a foamed product having a foaming ratio of several times to about 80 times is appropriately used according to the application, but recently, a cushioning packaging material, a heat insulating material, a float material, a cut product of a block. In fields such as the above, higher expansion ratios have been required.

As a method for obtaining a molded product having a high expansion ratio, for example, Japanese Patent Laid-Open No. 182353/1988 discloses a method in which a specific foaming agent and an organic solvent are used in combination, and primary expansion is followed by shrinking. A method for recovering and then foam-molding to obtain a polystyrene high-foam molded article is disclosed. In general,
If the bulk ratio is about several times to about 80 times, it can be molded without shrinking after heat-foaming, but especially foam particles heat-foamed to 100 times or more highly shrink when taken out into the air and cooled. However, it could be molded only after recovering this shrinkage. Also, it took several days to recover naturally in the atmosphere. Since it takes a long time to recover naturally, the production efficiency is low and many storage places are required.

When the amount of the foaming agent remaining in the primary foamed particles obtained by heat-foaming is small, it takes one week for the contracted primary foamed particles to naturally recover to the expansion ratio during heat-foaming. Since it may require a long period of time as described above, it was not suitable for industrial production.

In view of such circumstances, the inventors of the present invention contracted after primary foaming in the production of a high-foam molded article obtained by foam-molding primary expanded particles that have been heat-expanded to a bulk ratio of 100 to 350 times. As a result of diligent studies to quickly recover the expanded particles to almost the original bulk ratio and perform foam molding to obtain a highly expanded styrene resin molded product, place the shrunk expanded particles in a carbon dioxide gas atmosphere. Then, they found that they could recover very quickly, and completed the present invention.

[0006]

Means for Solving the Problems That is, expandable styrenic resin particles are heated and expanded to a bulk ratio of 100 to 350 times, cooled in the air and contracted to obtain contracted primary highly expanded particles, and the particles are carbonated. 90 to 1 of original bulk ratio in gas atmosphere
The present invention is directed to a method for producing a styrene resin highly foamed molded product, which comprises recovering the content of the styrene resin to 00%, and then filling it in a molding die and performing heat foaming molding.

The expandable styrenic resin 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 employing a known method such as an extrusion method in which a foaming agent is press-fitted, kneaded, discharged from a nozzle having a desired shape, and rapidly cooled with water in an unfoamed state and cut. After the foaming agent was contained in the styrene resin by these methods, dehydration, drying, and aging in a cool dark place, the amount of the foaming agent contained in the expandable styrene resin particles was 3 with respect to 100 of the styrene resin. It is preferably -9 parts by weight.
In order to obtain the primary expanded beads having a high bulk ratio of 100 to 350 times by one primary expansion, the foaming agent contained in the styrene resin is preferably 5 to 8 parts by weight.

The styrenic resin used in the present invention is a styrenic monomer alone or a copolymer with another comonomer. Examples of the styrene-based monomer include styrene, paramethylstyrene, vinyltoluene, tertiary butylstyrene and the like. Examples of the copolymerizable comonomer include acrylonitrile, methylmethacrylate, maleic anhydride, acrylic acid, methacrylic acid, N-phenylmaleimide and the like. These styrene resins are polymerized by a known method.

Further, the styrenic resin used in the present invention may contain a cell regulator, if necessary. In particular, when a homopolymer of polystyrene is used as the styrene resin, dilauryl 3,
An organic sulfur compound such as 3-thiodipropinate, dimyristyl 3,3-thiodipropinate and distearyl 3,3-thiodipropinate is added in an amount of 0.001 to 0.01 parts by weight based on 100 parts by weight of polystyrene. It is preferable to use a very small amount. In addition, organic solvents such as benzene, toluene, ethylbenzene styrene, flame retardants, antistatic agents, etc. may be added as necessary.

As the foaming agent contained in the foamable styrene resin in the present invention, an easily volatile foaming agent such as an aliphatic hydrocarbon or a halogenated hydrocarbon can be used alone or in combination of two or more kinds. Specific examples of the aliphatic hydrocarbon include, for example, propane, n-butane, isobutane, n-
Pentane, isopentane, cyclopentane and the like can be 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, it is particularly preferable to use a foaming agent composed of pentane, butane, and a mixture thereof, since a foam having a high magnification can be easily obtained by heating and foaming once.

In the present invention, the method of heat-foaming the expandable styrene resin particles 100 to 350 times is not particularly limited, but a method of directly heat-foaming using steam is particularly preferable. The vapor pressure at this time is normally 0 to 0 in gauge pressure.
2 kg / cm @ 2 is sufficient, and the heating time is selected depending on the amount of the foaming agent contained in the expandable styrenic resin and the target expansion ratio, but it is about 10 seconds to 600 seconds. Is. In the present invention, a high-magnification foam can be obtained in one step of foaming, but if necessary, this may be carried out in multiple steps. In addition, when an organic solvent such as benzene, toluene, ethylbenzene styrene, etc. is added to the expandable styrene resin particles, the vapor pressure at the time of primary foaming is
Usually, it is preferable that the gauge pressure is less than 0.5 kg / cm 2. This is because the primary expanded particles are easily coalesced with each other when the primary expansion is performed at a vapor pressure of 0.5 kg / cm 2 or more.

In the present invention, the expandable styrenic resin particles are heated and expanded to have a bulk ratio of 100 to 350 times, and then cooled in the air to be shrunk to recover the shrunk primary highly expanded particles in a carbon dioxide gas atmosphere. Although it is a feature,
In order to complete the recovery early, it is preferable that the concentration of carbon dioxide gas is at least 50% or more, and especially 8%.
Most preferably, it is 0% or more. For example, in the case of shrunk primary high-expanded particles having a bulk ratio of about 40 to 100 times, the original bulk ratio, for example, a bulk ratio of about 100 to 350 is set within about 15 minutes by setting the carbon dioxide atmosphere concentration to 80% or more. Can be doubled. Further, the time required for recovery can be further shortened by setting the carbon dioxide gas atmosphere to be a pressurized atmosphere, but the pressurized atmosphere is preferably less than 2 atm. As described above, the time required for the recovery can be significantly shortened as compared with the case where the conventional natural recovery in the atmosphere took several days. A good styrene-based resin highly foamed molded article can be manufactured by filling the high-expanded primary particles which have been recovered at an early stage with a bulk expansion ratio of 90 to 350 times in a molding die and foam-molded. Furthermore, after the primary foaming, by continuously introducing the highly expanded styrene resin particles into a carbon dioxide gas atmosphere, it is possible to produce a highly expanded styrene resin molded product without shrinkage.

In the present invention, the bulk ratio is 100 to 35.
The primary high-expanded particles that have been heat-expanded to 0 times are once shrunk, but recovered in a carbon dioxide atmosphere is closer to the original bulk ratio than when naturally recovered in the atmosphere.
That is, it can be recovered to 90 to 100% of the bulk ratio at the time of foaming by heating. Further, it was found that even when the amount of the foaming agent remaining in the primary expanded beads is small, a unique effect that the expanded bulk ratio closer to the bulk ratio during heat expansion can be recovered is exhibited.

[0014]

EXAMPLES Next, the method of the present invention will be described more specifically by way of examples. Examples 1 to 3 Pearl-like polystyrene having an average particle diameter of 1.0 mm containing 0.002 parts by weight of dilauryl 3,3-thiodipropinate as a cell adjuster with respect to 100 parts by weight of polystyrene, and n- as a foaming agent. Using 10 parts by weight of butane,
Impregnation in a water dispersion autoclave to give n-butane 8.
Expandable polystyrene particles containing 0 parts by weight were obtained. The expandable polystyrene particles obtained were aged in a cool dark place for 5 days.
The expandable polystyrene particles after aging contained 6.4 parts by weight of n-butane. The vapor pressure (gauge pressure) of the expandable polystyrene particles in the foam tank is 0.9 kg / cm2.
Then, the heating time was changed to 20, 40, and 60 seconds for foaming. Expandable polystyrene particles have a bulk ratio of 105
The primary foaming was performed twice, 215 times, and 310 times, but when it was cooled in the atmosphere, it immediately shrank to 45 times, 55 times, and 65 times, respectively.

Next, when the contracted polystyrene-shrinked primary high-expanded particles were recovered in an atmosphere having a carbon dioxide gas concentration of 90%, the bulk ratio upon heating and foaming was recovered in about 12 minutes.
The recovery behavior in this carbon dioxide atmosphere is shown in FIG. In addition, the recovered bulk magnifications are 105 times and 2 respectively.
It was 15 times and 310 times.

The recovered polystyrene primary high-expanded particles were filled into a 300 × 400 × 50 mm mold having steam holes,
It was heated with steam of 0.8 kg / cm @ 2 (gauge pressure) for 30 seconds, molded, and cooled with water to obtain a highly foamed molded product. This highly foamed molded product was left in a hot air drying chamber at 50 ° C. for 24 hours. The expansion ratio of the obtained polystyrene high-foam molded article is 100 times,
It was 200 times and 300 times, and the characteristics were not damaged.

Comparative Examples 1 to 3 45 times, 55 times, 6 obtained in Examples 1 to 3, respectively.
The polystyrene-shrinked primary expanded particles that had shrunk by 5 times were naturally left in the atmosphere. The recovery behavior in the atmosphere is shown in FIG. In addition, the bulk magnifications that naturally recovered after 2 days were 100 times, 190 times, and 250 times, respectively. In this way, the polystyrene primary expanded particles which were naturally recovered in this manner were used.
Molded in exactly the same manner as described above to obtain a polystyrene high-foam molded product. The expansion ratio of the obtained polystyrene high-foam molded article was 95 times, 180 times, and 240 times.
Only those having a low expansion ratio of about 5% to 25% as compared with those of Nos. 3 to 3 were obtained.

Examples 4 to 6 Styrene-acrylonitrile resin was extruded into a strand using an extruder equipped with a nozzle die at the tip, cooled in-line, and then cut to a diameter of 1 mm and a length of 1.5.
mm pelletized styrene-acrylonitrile resin was obtained. The pelletized styrene-acrylonitrile resin was impregnated in an aqueous dispersion autoclave using n-pentane as a foaming agent to contain 8.0 parts by weight of n-pentane per 100 parts by weight of styrene-acrylonitrile resin. Expandable styrene-acrylonitrile resin particles were obtained. The resulting expandable styrene-acrylonitrile resin particles were aged in a cool dark place. The foamable styrene-acrylonitrile resin particles after aging contained 7.0 parts by weight of n-pentane. The expandable styrene-acrylonitrile resin particles were heat-foamed with steam of 0 kg / cm 2 (gauge pressure), and the heating time was changed to 1 minute 30 seconds, 4 minutes, and 9 minutes, and foaming was performed. The bulk ratio of the obtained styrene-acrylonitrile resin primary high-expanded particles was 115 times and 2 respectively.
It once foamed 20 times and 320 times, but when it was cooled in the atmosphere, it shrank 80 times, 65 times, and 50 times, respectively.

Next, the shrunk styrene-acrylonitrile resin primary high-expanded particles were placed in an atmospheric pressure atmosphere having a carbon dioxide gas concentration of 98%, and they were recovered in about 10 minutes. The recovered bulk magnifications were 115 times, 220 times, and 320 times, respectively. The recovered styrene-acrylonitrile resin primary high-expanded particles are filled in a 300 × 400 × 50 mm mold having steam holes, heated with steam of 0.5 kg / cm 2 (gauge pressure) for 60 seconds, molded, and cooled with water to obtain a high-foam molded product. Got This highly foamed molded product was left in a hot air drying chamber at 50 ° C. for 24 hours. The styrene-acrylonitrile resin high-foam molded product thus obtained has a foaming ratio of 100 times, 20 times.
It was 0 times and 300 times, and the characteristics were not damaged.

Comparative Examples 4 to 6 80 times, 65 times and 5 times obtained in Examples 4 to 6, respectively.
The styrene-acrylonitrile resin primary high-expanded particles that contracted 0 times were left in the atmosphere. After 7 days, the bulk magnifications that spontaneously recovered were 105 times, 195 times, and 290 times, respectively. The naturally restored styrene-acrylonitrile resin primary expanded particles were molded by the same method as in Examples 4 to 6 to obtain a styrene-acrylonitrile resin highly expanded molded product. The expansion ratio of the obtained styrene-acrylonitrile resin high foam molding was 90 times, 185 times and 280 times.

[0021]

As described above, according to the present invention, the expandable styrenic resin particles are heat-foamed at an expansion ratio of 100 to 350 times, and the styrene resin shrinkage primary high-expanded particles which have been cooled and contracted in the atmosphere are carbonated. By recovering in a gas atmosphere, it is possible to recover in a very short time. Therefore, it is possible to mold at an early stage, and it is possible to reduce the storage time and place for recovery and efficiently produce a highly foamed styrene resin molded product. Further, as compared with the case where it takes a long time in the air to spontaneously recover, it is possible to recover to a higher magnification, so that it is possible to obtain a more highly foamed styrene resin foam molded article. .

[Brief description of drawings]

FIG. 1 shows the recovery behavior in a carbon dioxide atmosphere.

FIG. 2 Recovery behavior in the atmosphere.

Claims (1)

[Claims] 1. A foaming styrenic resin particle having a bulk ratio of 100
After heat-foaming up to 350 times, it is cooled in the air and contracted to obtain contracted primary highly expanded particles, and the particles are recovered to 90 to 100% of the original bulk ratio in a carbon dioxide gas atmosphere, and then in a molding die. A method for producing a highly foamed styrenic resin molded article, comprising: