JPS5824450B2 - 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 foam 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 foam moldings were discarded because it was not easy to make them bubble-free (and even if they were recycled as foam beads, they were not of good quality.

For example, if this foamed molded product is melt-kneaded using an extruder, a resin without bubbles can be obtained, but the resin thus obtained has poor heat resistance and cannot be made into a good foamed product.

In addition, if the resin obtained in this way is used in the field of general molded products other than foam, since this resin still has some foaming performance, some air bubbles will be generated in the product, and therefore It cannot be used as a general molded product.

In addition, since this 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 form lumps in the air bubbles. This causes the particles to get stuck in, 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 has already expanded and contained a large number of cells into expandable particles again.

As a method for manufacturing expandable particles, Japanese Patent Publication No. 46-2987
The method disclosed in the publication is known.

In this method, small unfoamed resin particles of uniform particle size are suspended in water, and a mixture of a polymerization initiator and styrene monomer is added at a certain ratio to perform polymerization. In this process, a blowing agent is injected under pressure to obtain expandable particles of uniform size.

It is not mentioned there that already foamed particles can be used as raw material.

Furthermore, as mentioned above, bubbles can be completely disappeared only by putting the foamed particles into an extruder and melting them, since it is difficult to remove the bubbles, so this method can eliminate the bubbles. It was completely unthinkable.

However, in an attempt, the foam molded product was once heated and compressed to reduce the air bubbles contained therein, and the foam was pulverized to a particle size of approximately 5 mm.

An attempt was made to polymerize the styrene monomer by dispersing the particles in water and dropping the styrene monomer therein.

As a result, as mentioned above, when the foamed particles are dispersed in water and styrene monomer containing a polymerization initiator is gradually dropped into the dispersed particles under pressure, the monomer becomes styrene particles. It was found that styrene polymer particles without air bubbles were created by crushing the air bubbles.

Therefore, it was confirmed that if a blowing agent is further press-injected during or after the polymerization, good expandable beads can be obtained.

This invention was made based on such confirmation.

This invention uses resin particles, which are made of a styrene resin that is already foamed and contains a large number of bubbles, and whose particle size is less than ICIrL, as a raw material, and disperses this raw material in water, which is then heated to reach the softening point of the resin. and then gradually add styrene monomer containing a polymerization initiator to polymerize the styrene monomer. A method for regenerating expandable styrenic resin particles, the method comprising injecting an aliphatic hydrocarbon, a cyclic aliphatic hydrocarbon, or a halogenated aliphatic hydrocarbon having be.

The various requirements of this invention method are 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 resin is used in commonly used foam moldings,
In other words, the foam may be foamed to about 50 to 60 times as it is, but it is preferable to increase the foaming ratio to about 5.
This has been reduced to twice that.

If a molded product expanded to about 50 to 60 times is heated above its softening point, the volume will be easily reduced and the expansion ratio will be lowered.

However, it is difficult to reduce the expansion ratio to several times just by heating the molded product.

In order to reduce the expansion ratio to about 5 times, it is necessary to further mechanically compress the molded article that has been shrunk by heating.

Even if the resin is mechanically compressed in this way, the compressed resin still contains many air bubbles.

The resin used as a raw material in the method of this invention is desirably 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 determined appropriately depending on the expansion ratio during pulverization, but even if the particles are crushed, the size of the particles is 1 cIrL.
The following shall apply.

When the expansion ratio is large, the particle size is increased,
When the expansion ratio is small, the particle size is made small.

For example, if a lump of a molded product that has been shrunk by heating has an average expansion ratio of 5 times, the particle size when crushed is 5 times.
-8 meshes is recommended.

The water used to disperse the resin particles contains a surfactant or a dispersant.

As these surfactants or dispersants, those used in suspension polymerization of styrene monomers 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 fractions of a percent or -10,000 percent by weight of water.

This water is placed in an autoclave since it is necessary to pressurize it during the reaction process.

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 resin particles are bulky, but the absolute amount of resin is not so large.

During the treatment process according to the present invention, the resin particles gradually lose air bubbles, so that the volume of the resin particles decreases.

Therefore, there is little risk that the particles will coagulate.

Generally, at the initial dispersion stage, when the particles are largely foamed, the proportion of water used relative to the resin will be large based on weight, and conversely, when 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.

The water in which resin particles are dispersed is heated to near the softening point of the resin.

Since the resin in this case has already been made into expandable particles, it may contain some foaming agent or softener, and therefore its softening point may be somewhat lower than the original softening point of the resin. many.

The degree of heating may be 60°C or higher, preferably 80°C.
The above shall apply.

As a result, the resin particles soften and tend to expel air bubbles to some extent to reduce the volume.

Gradually add styrene monomer to the above water.

In this case, a polymerization initiator is added to the styrene monomer in advance.

As the polymerization initiator, those conventionally used in suspension polymerization of styrene monomers are used as they are.

Examples of polymerization initiators are penzoyl peroxide and tert-butyl perbenzoate.

To add styrene monomer to water in which resin particles are dispersed, do not add the styrene monomer all at once, but gradually add it dropwise. Because it has the property of dissolving styrene monomers, the styrene monomer becomes integrated with the foamed resin particles and gradually polymerizes there.

When the styrene monomer is integrated with the foamed resin particles, the resin particles are already somewhat softened, but the addition of the styrene monomer makes the resin particles even more fluid. , the resin particles expel the air bubbles therein or allow the styrene monomer to enter into the air bubbles.

This results in bubble-free particles. Furthermore, the styrene monomer that has entered the particles polymerizes within the particles to produce a polymer.

In this way, styrenic resin particles without air bubbles are obtained.

A blowing agent is forced into this during or after the polymerization.

As the blowing agent, an aliphatic hydrocarbon, a cycloaliphatic hydrocarbon, or a logenated aliphatic hydrocarbon having a boiling point lower than the softening point of the styrene resin obtained therein is used.

Examples of aliphatic hydrocarbons are propane, propylene, butane, pentane, hexane, etc., examples of cycloaliphatic hydrocarbons are cyclohexane, and examples of halogenated aliphatic hydrocarbons are dichlorofluoromethane. .

Since these blowing agents have a boiling point lower than the softening point of the styrene resin, a portion of the blowing agent may become liquid if it is placed under normal pressure at the temperature at the time of injection.

When this blowing agent is press-fitted and pressure is applied as it is, the blowing agent gradually penetrates into the styrene monomer or resin particles.
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.

Pressure injection of a foaming agent is also somewhat effective in eliminating air bubbles in resin particles.

That is, since pressure is applied when the blowing agent is press-fitted, the bubbles are easily crushed in the softened resin (and the styrene monomer is easy to penetrate into the bubbles).

Moreover, since the foaming agent itself has the property of softening the resin to some extent, the bubbles are easily crushed.

For this reason, it is desirable to inject the blowing agent under pressure during the polymerization process.

When the blowing agent has penetrated into the 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, many air bubbles originally contained in the particles disappear, and the particles become bubble-free particles.

Additionally, the particles contain a blowing agent.

For this reason, similar to conventional expandable particles made from new raw materials, these particles can be left for a while (and then brought into contact with steam and foamed), similar to conventional expandable particles made from new raw materials. , foam evenly, fuse together,
Gives a good foam 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 9 g of magnesium pyrophosphate as a dispersant and 0.4 P of sodium dodecylbenzenesulfonate as a surfactant were added to 2000 g of pure water, and the mixture was placed in an autoclave with an internal volume of 5.6 liters equipped with a stirrer. Ta.

Foamed 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.
0 g was added to the above aqueous solution and stirred to disperse it.

This aqueous solution was heated while stirring and maintained at 85°C.

Separately, 0.1 g of benzoyl peroxide as a polymerization initiator and 0.04 g of tert-butyl perbenzonyone were dissolved in 200 g of styrene monomer, and this styrene monomer was added to the above aqueous solution. The styrene monomer was added dropwise slowly over 4 hours.

Next, the temperature of the aqueous solution was raised to 110°C, and the mixture was further stirred at this temperature for 2 hours, and then the temperature of the aqueous solution was lowered to 90°C, and 100 S' of pentane was injected under pressure.

Thereafter, stirring was continued for an additional 3 hours, and then the mixture was cooled and the resin was taken out to obtain expandable particles.

The expandable particles thus obtained contained 6% pentane therein and had a rounded shape without sharp corners.

In addition, when the specific gravity of this particle was measured, it was found that the specific gravity was 1.0.
1, which is close to the specific gravity of polystyrene of 1.04-1.05, and therefore it was found that there were almost no bubbles.

After the expandable particles were left at a temperature of 20°C for 4 days to mature, they were brought into contact with steam at a gauge pressure of 0.4 kg/cnf and heated.
It foamed twice as much.

This confirmed that the expandable particles foamed well.

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 particles were pre-foamed to about 40 times the size, left at room temperature for 6 hours, filled into a mold with a size of 30 x 30 x 7.5 crIL, and heated with water vapor at 0.7 kg/crA.
After heating for 10 seconds and then cooling for 2 minutes, the plate-shaped molded product was taken out from the mold.

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

In this way, it was confirmed that the moldability of the resin particles was also good.

Example 2 This example was carried out in the same manner as in Example 1, except that the composition of the styrene monomer and the composition of the blowing agent were changed.

The composition of the styrene monomer is as follows: 200 g of styrene monomer, 0 g of benzoyl peroxide as a polymerization initiator.
．． 61 and tert-butyl perbenzony) 0.0
4P and divinylbenzene as crosslinking agent 0.2'f! ′ was used.

A mixture of 60 g of pentane and 501 g of butane was used as a blowing agent.

Other polymerization conditions were the same as in Example 1 (expandable particles were obtained).

The expandable particles thus obtained contained 4% pentane and 2% pentane.
It contained 5% butane and had a rounded shape with no corners.

Further, its specific gravity was 1.005.

When these expandable particles were aged at a temperature of 20° C. for 4 days and then heated with 0.4 kg/ca steam, they expanded 71 times in 4 minutes, confirming that they foamed well.

Moreover, the foamed state was uniform and fine.

In this way, it was confirmed that the foaming property was good.

From these expandable particles, pre-expanded particles were made which were expanded to about 40 times the size, and after being left at room temperature for 8 hours, they were expanded to 30X.
Add the following to a mold with a size of 30X7.5CIrL and make 1.0k
g/crA water vapor was brought into contact with the foam board for 1 minute to heat it, followed by cooling for 2 minutes and 30 seconds to obtain a foam board.

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

In this way, it was confirmed that the expandable particles had good moldability.

Comparative Example 1 This comparative example was carried out in the same manner as in Example 1, except that styrene monomer and polymerization initiator were not used, and the treatment time was slightly longer.

An aqueous solution with the same composition and amount as used in Example 1 and foamed resin particles were placed in the autoclave used in Example 1, and after stirring was continued for 5 hours while maintaining this at 95°C, 1001 of pentane was press-fitted.

After that, stirring was continued for 3 hours, and then the mixture was cooled and the resin particles were taken out.

The thus obtained resin particles contained a large amount of water inside, contained only 3% of pentane, and had a specific gravity of less than 1.

These particles were not foamed uniformly, and even when they were put into a mold to form a plate, the particles were not sufficiently fused and the surface of the plate was rough.

Comparing this result with Example 1, it becomes clear that the method of this invention is superior.

Claims (1)

[Claims] 1. Consisting of styrene-based resin that has already foamed and contains many air bubbles, resin particles with a particle size of Icm or less are used as a raw material, and this raw material is dispersed in water and heated to maintain the temperature above the softening point of the resin. Then, styrene monomer containing a polymerization initiator is gradually added to this to polymerize the styrene monomer, and during or after the polymerization, a fat having a boiling point lower than the softening point of the styrenic resin is It is characterized by injecting a group hydrocarbon, a cyclic aliphatic hydrocarbon, or a halogenated aliphatic hydrocarbon to infiltrate it into the resin particles.
A method for recycling expandable styrenic resin particles.