JPS5824449B2 - How to use styrene cage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for returning a foamed styrenic resin molded article to its original state of unfoamed foamable resin particles and regenerating the foamable particles.

Styrenic resin foam moldings are made from foamable beads, which are pre-foamed, placed in a perforated mold, and the particles are foamed and fused within the mold. Made.

The foamed molded product thus produced is used as a packaging material, etc., but once used, it is discarded without being recycled.

However, discarded foam moldings do not rot and decompose even when exposed to rain and wind, so they remain for an indefinite period of time, making it difficult to find a place to dispose of them.

The reason why foamed molded products are discarded is that the large number of air bubbles contained therein cannot be easily crushed.

Although the bubbles can be crushed by melt-kneading using an extruder, the resin with the bubbles crushed in this way has poor heat resistance and cannot be made into a good foam.

Even if the bubbles can be crushed by some other method, there will still be some foaming agent left inside.
When processing this, there will always be some air bubbles in the product.
Therefore, it cannot be used as a raw material for making general molded bodies without bubbles.

Also, since this foamed molded product has air bubbles, it is possible to use it as is as a raw material for producing foam, but if you try to impregnate it with a foaming agent, the foaming agent will be mixed into the air bubbles. It enters in the form of clumps, thereby producing large bubbles, resulting in non-uniform foaming, making it impossible to produce a good foam.

For this reason, the foamed molded product was never used again.

The inventor intended to turn a styrene resin molded article that had already expanded and contained a large number of cells into expandable beads again.

The method for manufacturing expandable beads is described in Japanese Patent Publication No. 47-519.
The method disclosed in Japanese Patent No. 38 is known.

This method uses unfoamed styrene resin particles as a raw material, suspends them in water, adds a small amount of solvent, and then impregnates them with a gaseous blowing agent.

There is no mention that foamed particles can be used as raw material.

In addition, as mentioned above, it is difficult to completely remove air bubbles from already foamed particles until they are melted in an extruder and completely removed, so this method is used to eliminate air bubbles. I couldn't even imagine that it would be possible.

However, in an attempt to heat and compress the foamed product,
The air bubbles contained therein were reduced and the resulting particles were pulverized into particles with a size of approximately 5 mrft.

These particles are suspended in water, and a small amount of styrene resin solvent is added to it.
- Hold for 2 hours and then attempt to inject butane.

As a result, as mentioned above, when the foamed particles are suspended in water, a solvent is added first, the mixture is heated to above the softening point of the resin and stirred for a while, and then a foaming agent is press-injected. It was confirmed that all the air bubbles disappeared and good expandable beads were obtained.

This invention was made based on this confirmation.

This invention uses resin particles, which are made of a styrene resin that has already foamed and contains a large number of bubbles, and whose particle size is 1 cIrL or less, as a raw material, and disperses them in water, and
Add the solvent or swelling agent to the resin particles from 05 to 1
．． After adding 5% by weight and stirring for at least 30 minutes above the softening point of the resin, add an aliphatic hydrocarbon, cycloaliphatic hydrocarbon, or halogenated fat whose boiling point is lower than the softening point of the styrenic resin. The present invention relates to a method for regenerating expandable styrenic resin particles, which is characterized by adding group hydrocarbons under normal conditions and allowing the hydrocarbons to permeate into the resin particles.

The various requirements of this invention will be explained in detail as follows.

The resin used as a raw material is a styrene resin that has already been foamed and contains many cells.

This styrene-based resin is a commonly used foam molded product, which may be foamed approximately 50 to 60 times, but it is preferable to heat this foam to a temperature higher than the softening point of the styrene-based resin, and The foaming ratio is reduced to about 5 times.

If a molded product that has been expanded to about 50-60 times is heated above its softening point, its volume can be easily reduced and the expansion ratio can be increased to 10.
It becomes about 0 times.

However, it is not easy to reduce the expansion ratio to about 5 times by simply heating the molded product.

In order to reduce the expansion ratio to about 5 times, the heated and shrunk molded body must be further mechanically compressed.

Even if the resin is mechanically compressed in this manner, the compressed resin still contains a large number of air bubbles.

The resin used as a raw material in the method of this invention is preferably one that has been mechanically compressed and has a low expansion ratio as described above.

The above raw material resin is used in the form of particles.

In order to make the above-mentioned 50-60 times expanded molded product into particles, it may be cut or crushed.

When using a material with a small expansion ratio, it is desirable to lower the expansion ratio first and then cut or crush it into particles.

The degree of pulverization is appropriately determined depending on the expansion ratio immediately before pulverization, but in any case, the particle size is 16 rrL or less.

When the foaming ratio is large, the particle size should be increased (
When the expansion ratio is small, the particle size is made small.

For example, if a lump of a molded product shrunk by heating has an average expansion ratio of 5 times, it is crushed to a particle size of 5-8 meshes.

As the water for dispersing the particles, water containing a surfactant or a dispersant is used.

As these surfactants or dispersants, common surfactants or dispersants used when obtaining polystyrene particles by suspending styrene monomers in water and polymerizing the suspension can be used as they are.

By way of example, the surfactant is, for example, sodium dodecylbenzenesulfonate, and the dispersant is, for example, magnesium pyrophosphate.

Such surfactants or dispersants are used in the range of several tenths of a percent or -10,000th percent by weight of the water.

This water was used as a convenience for later press-fitting the blowing agent.
placed in an autoclave.

When dispersing the resin particles in water, the ratio between the two should be such that the amount of resin particles is as large as possible within the limit that the resin particles can be dispersed in water.

When the resin particles are initially dispersed in water, the resin particles contain a large number of air bubbles, so the amount of the resin particles is quite large (even though the absolute amount of the resin is not very large).

Moreover, the resin particles gradually lose their bubbles during the treatment process of the method of this invention, so that the volume of the resin particles decreases in the final stage.

Therefore, the possibility that the particles will aggregate is not so great.

Generally, at the initial dispersion stage, if the particles are largely foamed, the proportion of water used in the resin will be large based on weight, and conversely, if the particles are only slightly foamed, the proportion of water used will be small. Become.

Therefore, it is advantageous to use particles with a small expansion ratio because the absolute amount of resin particles obtained in one operation becomes large.

A small amount of a solvent for the styrene resin is added to the above water.

Suitable solvents are aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, or aliphatic halogenated hydrocarbons such as tetrachloroethylene.

The amount used depends somewhat on the amount of water and the properties of the resin particles, but it ranges from 0.5 to 1.5% by weight based on the resin particles.
shall be.

The solvent may be added to the water before, after, or simultaneously with dispersing the resin particles in the water.

After dispersing resin particles and a solvent in water, this is heated to a temperature above the softening point of the resin particles.

At this time, the water is stirred well to ensure that the resin particles are well dispersed in the water.

As a stirring method, it is desirable to use a method in which a shaft rotates and blades are attached around the shaft, and as the blade rotates, the water is pushed down toward the bottom of the container.

Further, the heating is carried out at a temperature above the softening point of the resin, and stirring is continued at this temperature for at least 30 minutes, preferably for 1 to 2 hours.

A blowing agent is then forced into the system.

As the blowing agent, an aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon having a boiling point lower than the softening point of the styrene resin is used, such as propane, propylene, butane, pentane, hexane, and cyclohexane.

The blowing agent may also be a halogenated aliphatic hydrocarbon, such as dichlorodifluoromethane, whose boiling point is below the softening point of the styrenic resin.

All of these blowing agents have boiling points below the softening point of the styrene resin, so they naturally become gases under normal pressure at the temperature at which they are injected. When placed under pressure, some parts may become liquid.

When such a blowing agent is compressed and kept under pressure,
The blowing agent gradually penetrates into the styrenic resin particles, and the pressure inside the container gradually decreases.

The degree to which the blowing agent has penetrated into the resin particles can be determined by this decrease in pressure.

When the blowing agent has penetrated into the styrene resin particles, the temperature inside the container is lowered, the pressure of the remaining blowing agent is removed, and the contents are taken out.

Thereafter, the dispersed resin particles are separated from the water and washed with water to obtain resin particles.

This is the desired expandable particle.

The expandable particles obtained in this way do not have sharp corners as they do when crushed, but have a rounded shape.

In addition, the many air bubbles that were initially contained in the particles have been completely crushed, resulting in particles without air bubbles.

Additionally, the particles contain a blowing agent.

Therefore, like the conventional expandable particles made from new raw materials, if these particles are left for a while and then brought into contact with steam and foamed, they will become exactly the same as the conventional expandable particles made from new raw materials. , foams evenly and well, and fuses well with each other to give a good foamed molded product.

In this way, good expandable particles can be obtained again from foams that were previously discarded.

Next, examples will be given to describe the details of the method of the present invention and to clarify its effects.

Example 1 Pure water 3000? 9 g of magnesium pyrophosphate as a dispersant and 0.41 g of dodecylbenzenesulfone-acid sodium as a surfactant were added to the autoclave, which had an internal volume of 5.6 liters and was equipped with a stirrer.

Add 12 g of toluene to this aqueous solution, stir well,
This was dispersed.

Next, expanded polystyrene particles were added to this aqueous solution.

As the polystyrene particles, polystyrene particles with an expansion ratio of about 5 times and a particle size of 5 to 8 mesh are used.
001' was dispersed in an aqueous solution.

Thereafter, the aqueous solution was heated with stirring and maintained at 95° C. for 2 hours, and then a mixture of 607 pentane and 501 butane was pressurized into the solution.

After continuing to stir for 4 hours, the mixture was cooled and the expandable resin particles were taken out.

The foamable resin particles thus obtained contained 4% pentane and 2.5% butane, and had a rounded shape without sharp corners.

In addition, when the specific gravity of this resin particle was measured, it was found that the specific gravity was 1
．． 005, and the specific gravity of polystyrene is 1.04-1.
05, and therefore had almost no bubbles.

After the foamable resin particles were left to mature at a temperature of 20° C. for 3 days, they were brought into contact with steam at a gauge pressure of 0.4 kg/ca and heated, resulting in foaming about 50 times in 1 minute.

This confirmed that the expandable resin particles were well foamed.

Furthermore, when the foamed particles were examined for the state of the bubbles, it was found that the bubbles had the same size and were evenly dispersed.

Separately, the expandable resin particles are pre-foamed to about 30 times,
After leaving at room temperature for 6 hours, 77 to 30X30X7.5
The mixture was filled into a mold having a size of 1, heated with 0.7 kg/ca steam for 1 minute, then cooled for 2 minutes, and then taken out from the mold.

In this plate, each particle was sufficiently fused and the surface was smooth.

Thus, it was confirmed that the moldability of the resin particles was also good.

Example 2 In this example, the same autoclave as in Example 1 was used, an aqueous solution of the same composition and amount was added thereto, 10 g of ethylbenzene was added as a solvent, and after thorough stirring, the same foaming as in Example 1 was carried out. After dispersing the same amount of polystyrene particles of the same magnification and size and keeping them at 95°C for 2 hours, 60L?
of Penkun and 601 of butane were press-fitted.

After that, stirring was continued for 4 hours, and then the mixture was cooled and the resin particles were taken out.

The resin particles thus obtained contained 4% pentane and 3% butane and had a rounded shape.

It was also confirmed that the resin particles had a specific gravity of 1.005 and contained almost no air bubbles.

After aging these resin particles at a temperature of 20°C for 3 days,
When heated with 0.4 kg/crA steam, it foamed approximately 52 times in 1 minute and 10 seconds, confirming that it foamed well.

In addition, the foamed material had particles of the same size evenly dispersed therein.

Thus, it was confirmed that the resin particles had good foamability.

Separately, pre-expanded particles were made from the resin particles to a size of about 35 times, and after being left at room temperature for 6 hours,
0X7.5 (fill into a mold of size 11771, 0,7
kg/cr; r, of water vapor was brought into contact with the foam board for 1 minute to heat it, followed by cooling for 2 minutes to obtain a foam board.

The particles of this plate were well fused and the surface was beautiful.

Thus, it was confirmed that the moldability of this resin particle was good.

Comparative Example 1 This comparative example is generally similar to Example 1, except that 12 g of toluene is not used, and as a blowing agent, 100 g of pentane is used instead of a mixture of 60 g of pentane and 501 g of butane. Example 1 except that the time to maintain the temperature at 95°C after dispersing the resin particles in the aqueous solution using a vacuum cleaner was extended from 2 hours to 3 hours, and the time to continue stirring after pentane injection was increased to 5 hours. Expandable resin particles were obtained in the same manner as above.

The expandable particles obtained in this way contain a large amount of water and 3% pentane, but when they were treated and foamed in the same manner as in Example 1, large bubbles were sparsely generated. The foaming properties were not good.

Further, when a plate was made in the same manner as in Example 1, the fusion of the particles was poor (the surface of the molded product was also uneven, and the moldability was not good).

Comparative Example 2 This comparative example was processed in much the same way as Example 1, except that the solvent and blowing agent were added to the resin particles at the same time.

Into the same autoclave as in Example 1, put an aqueous solution with the same composition and amount, and disperse resin particles with the same expansion ratio and size. After stirring for an hour, 10' of toluene as a solvent was used. And 60L of pentane as a foaming agent? , butane 501 were press-fitted.

After that, stirring was continued for 5 hours and then cooled to obtain expandable resin particles.

The foamable particles obtained in this way contained a large amount of water, and also contained 3.5% penkune and 2% butane, but when they were foamed, the air bubbles were large and sparse. The foaming ratio was also low at 35 times.

Claims (1)

[Claims] 1 Consisting of styrene-based resin that has already foamed and contains a large number of bubbles, resin particles with a particle size of ICIrL or less are used as a raw material, and the resin particles are dispersed in water, and the solvent is applied to the resin particles. After adding 0.5 to 1.5% by weight and stirring for at least 30 minutes above the softening point of the resin, add aliphatic hydrocarbons and cycloaliphatic carbons whose boiling point is lower than the softening point of the styrene resin. A method for regenerating expandable styrenic resin particles, which comprises adding hydrogen or a non-logenated aliphatic hydrocarbon under pressure and allowing the hydrocarbon to permeate into the resin particles.