JPS63135436A - Production of pre-expanded styrene resin particle - Google Patents

Abstract

PURPOSE:To obtain the title particles which need not be dried and aged and can give a dense and beautiful molding surface, by feeding a volatile expanding agent-containing styrene resin and a pressurized heating gas to a sealed container and heating the mixture under specified conditions of pressure and temperature. CONSTITUTION:Particles of a styrene resin such as a styrene homopolymer are impregnated with a volatile expanding agent of a b.p. <=60 deg.C, such as butane or dichlorofluoromethane, to obtain expandable styrene resin particles. The pre-expansion tank 6 equipped with an agitator shaft fitted with vertical impellers 9 in the middle of a pre-expansion molding machine 1 is evacuated through a vacuum pump and a vacuum pipe 13, and said expandable styrene resin particles are fed by suction from a pipe 4 through the supply cylinder 3 of a feeder 2 to the tank 6. The pressure in the tank 6 is decreased to -50--700mmHg and the resin particles are heated to a temperature higher than the b.p. of the expanding agent and lower than the softening point of the particles by feeding heating steam to a jacket 7 and 7' and at the same time feeding a pressurized heating gas from a supply pipe 14 to the tank to increase the pressure to 0.01-5kg/cm<2>G. The particles are heated for 1-60min.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for pre-foaming expandable styrenic resin particles. According to this method, the ripening period can be eliminated.

[Prior art]

Expandable styrenic resin particles containing 2 to 12% by weight of a volatile swelling agent obtained by a suspension polymerization method are fed into a pre-foaming tank using a screw feeder, and heated under stirring and normal pressure for 85 to 12% by weight.
It has been practiced to introduce water vapor at 100°C into a pre-foaming tank and foam the expandable styrene resin particles 10 to 50 times to obtain pre-foamed particles (% Kosho 50-1722).
No. 3, JP-A-55-148134, JP-A-56-51
No. 76, No. 58-50181).

Since the pressure inside the foam cell is reduced, the pre-expanded particles are immediately filled into the cavity of a mold having steam permeation holes, and then heated with steam to expand the pre-expanded particles. When the molded products are made to form a foamed molded product by melting and fusing them together, and then cooling, the molded product shrinks and cannot withstand practical use.

Therefore, after pre-foaming, the pre-foamed particles are stored in a silo at a temperature of 20 to 100°C until the pressure within the foam cells of the pre-foamed particles becomes approximately equal to atmospheric pressure, also to dry the aggregated water. (the so-called aging process).

The reality is that this aging requires at least 3 to 4 hours for the pre-expanded diameter, and usually 1 to 2 days.

Therefore, for manufacturers of molded foam molding, shortening this aging period has the advantage of improving productivity and reducing the size of storage equipment for aging one pre-expanded particle.

As a method for shortening the aging period, a method has been proposed in which after producing the pre-expanded particles, the pre-expanded particles are aged at a hot air temperature of 60-100°C for 5-20 minutes (Japanese Patent Application Laid-Open No. 1983-1991).
-116526).

This method also requires storage equipment for aging after preliminary foaming.

[Problem that the invention seeks to solve]

The present invention provides a pre-expanded method for obtaining pre-expanded particles that does not require an aging period. In other words, as a heating means for pre-foaming the expandable styrenic resin particles, heated pressurized/hot air is used instead of conventional steam, and the ripening of the pre-foamed resin particles is simultaneously performed at the same time as the pre-foaming. This can be done in a pre-foaming tank. During this pre-foaming, air permeates into the foam cells of the resin particles, and the pressure inside the cells of the pre-foamed resin particles is equal to, or even higher than, atmospheric pressure, so that the resulting pre-foaming Even when the foamed resin particles are taken out of the pre-foaming tank, there is no shrinkage, and therefore aging of the pre-foamed resin particles is not necessary.

[Specific measures to solve the problem]

In the pre-foaming method using hot air, the present inventor uses pressurized hot air, and this hot air permeates into the pre-foamed particles so that the pressure within the foam cells prevents shrinkage during molding of the pre-foamed particles. We judged that the aging process was not necessary if the reduced pressure had been resolved to a certain degree, and when we examined the pressure of the pressurized gas, we found that it was 0.01 to 5 u/e+yl G N 6o
It has been discovered that pre-expanded particles that do not require aging can be obtained by heating for 0.5 to 30 minutes at a temperature of ~150°C, and the present invention has been achieved.

That is, in the present invention, styrene-based resin particles containing a volatile expansion agent are supplied into a sealed container, and then heated pressure gas is introduced into the sealed container to reduce the pressure in the sealed container to 0.01.
The present invention provides a method for producing pre-expanded styrenic resin particles, characterized in that the styrenic resin particles have a foaming ratio of 9/c11IG or more, and further foam the styrenic resin particles.

In the present invention, the expandable styrenic resin particles include, for example, evastyrene homopolymer, styrene and α-methylstyrene,
Copolymer resin particles with chlorostyrene, acrylonitrile, methyl methacrylate, etc., contain propane,
Contains a volatile swelling agent with a boiling point of 60°C or less at normal pressure, such as aliphatic hydrocarbons such as pentane and hexane, and aliphatic halogenated hydrocarbons such as methyl chloride, dichlorofluoromethane, and trichlorofluoroethane. It is something.

Next, a pre-foaming machine implementing the present invention will be explained using the drawings.

Figure 1 is a sectional view of the pre-foaming machine 1, in which 2 is a feeder for foamable resin particles, 3 is a supply cylinder, 4 is a pipe for feeding foamable resin particles for filling, and 5 is a jacket safety valve. It is. Reference numeral 6 designates a cylindrical pre-foaming tank, and a heating jacket 7, 7' is provided on the peripheral wall of the tank in a cylindrical shape. Reference numeral 8.8' denotes steam supply pipes for the heating medium, and these steam supply pipes are equipped with a pressure gauge, a valve, and a vent pipe (not shown). At the center of the pre-foaming tank 6, a stirring shaft 10 is provided with stirring blades 9,9,9,9 arranged vertically. This stirring shaft 10 is rotated about a horizontal axis by a V-belt 12 that transmits the driving force of a motor 11.

13 is a pressure reducing pipe provided to facilitate the supply of expandable resin particles into the pre-foaming tank 6; 14 is a pressurized and heated gas introduction pipe; and 15 is a pipe for discharging pre-foamed particles. 16 is a discharge port for pre-expanded particles. 1
7 is a safety valve in the foaming tank.

To carry out preliminary foaming using the preliminary foaming machine 1, the pressure inside the preliminary foaming tank 6 is reduced by reducing the pressure in the pressure reducing pipe 13 using a vacuum pump, and the supply cylinder 3 for filling is opened. As a result, the foamable sderene resin particles are sucked into the pre-foaming tank 6 through the pipe 4 and supplied. (
(Gravity fall method is also possible) The pressure inside the pre-foaming tank 6 is -5
0 to -700 gmI (g vacuum is applied.

Prior to supplying the foamable sderene resin particles, stirring f
By starting the rotation of IIIJ10 and introducing heated steam to the jacket 7.7', the pre-foaming tank 6 has a temperature of 60 to 15
It is heated to a temperature of 0°C.

Next, the valve of the pressure reducing pipe 13 and the pipe 4 of the feeder 2
After closing the valve, the heated pressure gas introduction pipe 14
The valve is opened and heated and pressurized gas (excluding water vapor) is introduced into the pre-foaming tank 6 to perform pre-foaming.

As the gas, air, nitrogen gas, carbon dioxide gas, helium, or a mixture thereof can be used, but air, which is inexpensive, is preferable. The temperature of the compressed gas is preferably 60 to 150°C.

The gas pressure is 0.01 to 5#/dG, preferably 0.01 to 5#/dG.
06-5 Cape/iG is good. If there is a pressure of 0.01 storage/dG or more, the pressure gas will penetrate into the pre-expanded particles, but
After pre-foaming, in order to obtain a foam molded product without shrinkage by directly foam molding the mold, the heating time using pressurized gas is 0.01.
kg/adG requires a long time of 6 hours or more,
In order to keep the aging time within 1 hour, the pressure was set to 1.0#/c.
Must be IAG or higher. The higher the pressure, the shorter the heating time (pre-foaming time). However, the pressure is S#/
If it is above cIIG, the internal pressure of the foamed particles will be too high and the foamed particles will be deformed due to the internal pressure of the foamed particles when taken out from the foaming machine, so it is preferable to carry out the process at less than s#/cdG.

The heating time (pre-foaming time) depends on the gas pressure, temperature, and bulk density of the pre-foamed resin particles obtained, but is 1 minute to
The duration is 60 minutes, preferably 5 to 30 minutes.

A guideline for this heating time is a time such that the reduced pressure in the foam cells of the obtained pre-foamed resin particles becomes greater than 1180 mHg and the density of the obtained pre-foamed resin particles becomes a desired density.

The pressure inside the cell is lower than 1180cm, for example -210cm
When the pre-expanded particles of vm f(g are foam-molded into a mold, the foamed molded product obtained is shrunk.

The pressure inside the foam cell of the pre-expanded resin particles was determined by immediately sealing the obtained pre-expanded resin particles 3,000 OOW in a cylindrical container with a capacity of 3,000 ai, and measuring the pressure inside the foam cell at each elapsed time. The pressure when the pressure inside the cell becomes constant is regarded as the internal pressure of the foamed cell of the pre-expanded resin particles.

〔Example〕

FIG. 2 shows that expandable polystyrene particles containing 7.0 weight percent of butane are supplied into a pre-foaming tank 6 which has been heated to 105°C in advance and the pressure inside the tank is set to 1,650 μHg. Cylinders 3 and 13 are closed, 90°C hot air is supplied into the pre-foaming tank through pipe 14, and the pressure inside the pre-foaming tank is reduced to 1.
Maintained at a pressure of 95 kf/liG for 10 minutes (the bulk density of the obtained pre-expanded particles was 20.7 f/l), ・15 minutes (the bulk density of the obtained pre-expanded particles was 1 s, ot/t) or 20 minutes (the bulk density of the pre-expanded particles obtained is x2.ot/l)
) After heating and pre-foaming, the supply of hot air is stopped and the pressure inside the pre-foaming tank is returned to atmospheric pressure (0#/dG) K, the valve of the pipe 14 is switched to supply compressed air into the pre-foaming tank. 3 shows the change over time in the pressure inside the foam cell of the pre-expanded resin particles which were supplied through the pipe 15 and extracted from the pipe 15.

The same figure also shows pre-expanded polystyrene resin particles with a bulk density of 15.2 t/l obtained by heating for 10 minutes at a pressure of 1.0 #/ff1G and 20 2 shows the change over time in the pressure inside the foam cells of pre-expanded polystyrene resin particles having a bulk density of 12.5 l/l obtained by heating for minutes.

Figure 3 shows hot air at 90°C being used for 6 minutes, 10 minutes, and 20 minutes in a pre-foaming tank with the pipe 15 open (under atmospheric pressure).
Pre-expanded polystyrene resin particles (bulk density 22.2 f/L, respectively) obtained by dividing and pre-foaming 17.
2 f/l, 12.4 f/t).

Immediately after taking out these pre-expanded polystyrene particles from the pre-expanding tank,
Fill the cavity of the mold of ■, then 0.7kf
/aAG steam for 20 seconds to expand the pre-expanded particles and fuse them together to form a molded body, then 20°C cooling water for 30 seconds to cool the molded body, and open the mold to obtain a molded body. The appearance of the foam molded product after one day was as follows.

Table 1 *The experiment was carried out under atmospheric pressure (o#/mG), but the pressure inside the pre-foaming tank was 0.0 due to the influence of the volatile expansion agent and air expansion.
It became 6#/mG.

〔effect〕

According to the pre-foaming method of the present invention, there is no need to age the pre-foamed particles after pre-foaming. Furthermore, since the water vapor does not come into direct contact with the pre-expanded particles during pre-expanding, there is no need to dry the moisture in the pre-expanded particles as in the conventional method. In addition, the surface of the pre-foamed resin particles has good gloss, and the surface of the molded product is beautiful with few gaps between particles.

[Other embodiments]

In carrying out the present invention, paraffin, glyceride stearate, a surfactant, etc., which are crack generators that can shorten the molding time of foam molding, are supplied together with the expandable resin particles into a pre-foaming tank. It is also possible to obtain pre-expanded particles whose surface is coated with a crack-initiating agent.

In addition, although the examples were carried out using styrene homopolymer particles, styrene/α-methylstyrene/acrylonitrile copolymer, styrene/methyl methacrylate copolymer,
Of course, the method can also be applied to styrenic resins such as BS, styrene/acrylonitrile copolymer, styrene/maleic anhydride copolymer, and the like.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pre-foaming machine, and FIGS. 2 and 3 are graphs showing changes over time in the pressure inside the foam cells of pre-foamed particles.

Claims (1)

[Claims] 1) Styrenic resin particles containing a volatile expansion agent are supplied into a sealed container, and then heated pressure gas is introduced into the sealed container to reduce the pressure in the sealed container to 0. 01kg/cm
Pre-expanded styrene, characterized in that the styrene-based resin particles are foamed by heating the foam to a temperature higher than the boiling point of the volatile expansion agent and higher than the softening point of the styrene-based resin particles. Method for producing resin particles. 2) The manufacturing method according to claim 1, wherein the styrene resin particles are styrene homopolymer particles. 3) The manufacturing method according to claim 2, wherein the foaming temperature is 60 to 150°C. 4) The manufacturing method according to claim 1, wherein the pressurized gas is air. 5) The foaming is carried out so that the pressure within the foam cells of the obtained pre-expanded styrenic resin particles is higher than -180 mmkg.
Manufacturing method described in section.