KR940005547B1 - Process for producing expandable polystyren resin particles - Google Patents

Abstract

The particle of foaming polystyrene based resin is prepd. by: adding and dissolving 5-30 wt.pts. of styrene polymer comprising larger particle of above 6 mesh, midle particle of 6-45 mesh or below 45 mesh; and suspention-polymerizing to prepare the polymer particle with 0.05-3.0 wt.pts. of the catalyst comprising benzoil peroxide, t-butyl perbenzoate or dicumul peroxide; adding 0.05-4.0 wt.pts. of tricalcium phosphate or pyrophosphoric acid magnesium as dispersing agent, 0.08-0.1 wt.pts. of alkylbenzene sulfonic acid natrium or dodecylbenzene sulfonic acid natrium as dispersing assistant, and 2-15 wt.pts. of pentane or butane as foaming agent.

Description

Method for producing expandable polystyrene resin particles

Figure 1a is a graph showing the particle size distribution of the polystyrene-based resin particles prepared in Example 1 according to the present invention,

b is a graph showing the particle size distribution of the polystyrene resin particles prepared in Comparative Example 1 according to the conventional suspension polymerization method;

Figure 2a is a graph showing the foamability over time of the polystyrene-based resin particles prepared in Example 1 according to the present invention,

b is a graph showing the foamability over time of the polystyrene-based resin particles prepared in Comparative Example 1 according to the conventional suspension polymerization method;

Figure 3a is a micrograph showing the microstructure of the polystyrene-based resin particles prepared in Example 1 according to the present invention,

b is a photomicrograph showing the microstructure of the polystyrene-based resin particles prepared in Comparative Example 1 according to the conventional suspension polymerization method.

The present invention relates to a new method for preparing expandable polystyrene resin particles, and more particularly, to polymerize after all the particles or small particles of the spylene polymer produced during the polymerization process by dissolving and suspending the spylene monomer. The present invention relates to a method for producing expandable polypropylene resin particles having a uniform particle size distribution.

Until now, various methods have been proposed for the production of styrene polymer particles. Among them, emulsion polymerization or suspension polymerization are known. In general, spherical polymer particles can be produced by suspension polymerization.

The suspension polymerization method is a method of adding a suitable suspension stabilizer to water, dispersing the styrene monomer under stirring, and adding a polymerization catalyst to polymerize it, but in this case, it is affected by the viscosity increase or stirring state of the solution during polymerization, and is a complicated process such as dispersion and bonding. Because of this, even when the proper conditions for polymerization are set, the finally obtained polymer particles exhibit a wide particle size distribution. That is, it is very difficult to obtain particles having a specific narrow range of particle size distribution since the generation of alleles of 6 mesh or more in the polymer particles results in small particles passing through the 45 meshes, especially micro particles passing through the 70 meshes. In addition, since the production rate of these alleles or small particles is 25% or more, a separate screening process is required.

In addition, in obtaining the granulated particles by impregnating and maturing the foaming agent with the foaming agent thus produced, in the case of microparticles having a small particle size, volatilization of the foaming agent impregnated therein occurs quickly, and the foaming force is liable to drop during aging. On the contrary, in the case of large particles having a large particle size, the expansion of the blowing agent in the particles is slow during aging, and thus a long time of aging takes a long time, and thus the foaming power tends to be lowered.

Therefore, when the foaming agent is impregnated using polymer particles containing both alleles and small particles produced by the conventional suspension polymerization method, it is difficult to foam uniformly due to different foaming time between the sobilizer and alleles at the time of foaming. As a result, a filling defect occurs during molding processing to obtain a molded article having poor fusion and surface state, and a aging period of a long time (more than 7 days) is required to obtain a stable bubble structure during foaming.

Therefore, if the foaming agent is impregnated using polymer particles containing both the alleles and the small particles produced by the conventional suspension polymerization method, the foaming time between the small particles and the alleles at the time of foaming is difficult to uniformly foam. Poor filling during the molding process results in a molded article having poor fusion and surface condition, and requires a aging period of a long time (more than 7 days) in order to obtain a stable bubble structure during foaming.

Therefore, in order to shorten the aging of the impregnated particles, various methods have been tried in the past, and a method of aging under atmospheric conditions in which a low temperature of 20 ° C. or less is maintained is known. However, this method requires special storage facilities and management, and if the temperature is high, the foaming agent volatilizes rapidly on the surface of the impregnated resin particles. do.

In addition, a method of using a small amount of foaming agent during the mixing is known among the methods for shortening the aging time. Such a method causes a decrease in foaming power during foaming, and thus it is impossible to obtain foams with high foaming and up to a constant magnification.

There are other methods to reduce the molecular weight of the styrene polymer to shorten the aging time. However, in this case, since the polymer has a low molecular weight, the heat resistance may be reduced, resulting in shrinkage of the foam granules during foaming and deterioration of physical properties of the molded article.

Therefore, it has been desired to obtain spherical styrene polymer particles of homogeneous particle size, and to obtain foam granules having a uniform bubble structure and high foaming and up to a constant magnification.

It is an object of the present invention to provide a method which can produce foam particles having high foaming and constant magnification by obtaining polymer particles densely packed in the range of the central particle size and impregnating the foaming agent therewith.

The object of the present invention is that in the styrene polymerization process, polymer particles of homogeneous particle size distribution obtained by dissolving and suspending styrene polymer particles having a specific particle size in an amount of 5 to 30 parts by weight based on 100 parts by weight of styrene monomer. It is achieved by the method of impregnating the blowing agent in the aging process.

According to the method of the present invention, particles having a particle size of 16 to 30 mesh can be obtained in a high yield of 85 to 93%, and thus the particle size of the obtained polymer is homogeneous. The foam structure is homogeneous and foaming up to high foaming and constant magnification can be obtained. When a molded article is produced using such foamed granules, a molded article having good fusion and surface condition can be obtained.

Hereinafter, the present invention will be described in detail.

First, in the styrene polymer particles obtained by the conventional suspension polymerization method, all particles of 6 mesh or more, intermediate particles in the range of 6 to 45 mesh, or small particles passing through 45 mesh are added to 5 to 30 parts by weight based on 100 parts by weight of styrene monomer. It is dissolved and suspended and then polymerized in the presence of a polymerization catalyst.

The particle size distribution of the polymer particles thus obtained is very homogeneous because the productivity of the 16 to 30 mesh reaches 85 to 93%. At this time, among the styrene polymers used as part of the polymer raw material, the particles having a median particle size of 6 to 45 mesh can be impregnated on their own and used as a foaming resin. If the particles of the polymer are dissolved in the styrene monomer as in the present invention, In this case, the uniformity of the particle size distribution and the shortening effect of the aging time of the particles can be sufficiently obtained, but there is no economic efficiency in the manufacturing process. Therefore, the dissolving styrene polymer particles used as part of the raw material in the present invention, it is preferable to use 6 mesh or more allele or 45 mesh or less.

The dissolving styrene polymer particles used in the method of the present invention are styrene polymers, such as styrene homopolymers or copolymers of styrene and acrylonitrile or copolymers of styrene and α-methylstyrene, with respect to 100 parts by weight of styrene monomer. 5 to 30 parts by weight, suitably 5 to 25 parts by weight is good to use.

If the dissolved styrene polymer particles are polymerized using less than the above amount, the effect obtained in the present invention cannot be obtained, and if the dissolved styrene polymer particles are used more than the above amount, the dispersion of the styrene monomer causes poor dispersion due to the viscosity increase of the styrene monomer. If particles cannot be obtained, and water droplets penetrate into the particles due to poor dispersion, it is difficult to release the particles to the outside, so that pin holes are formed in the resin particles to deteriorate the surface of the foam granules and lower the physical properties of the molded body.

As the styrene monomer used in the present invention, a styrene monomer is mainly used, and a mixture of a copolymerizable monomer with styrene having a styrene monomer as a main component, for example, a mixture of styrene monomer and α-methylstyrene or acrylonitrile, etc. may be used. Can be.

The styrene polymer may be used by dissolving in the styrene monomer in a predissolution tank or by dissolving in a reactor during the polymerization process.

In the present invention, a catalyst is used to polymerize the styrene monomer. As the catalyst to be used, organic peroxides such as benzoyl peroxide, t-butylperbenzoate, lauryl peroxide and dicumyl peroxide are used.

According to the present invention, such a catalyst is used by dissolving in a part of the styrene monomer used in the polymerization, and the amount of use is preferably 0.05 to 3.0 parts by weight based on 100 parts by weight of the styrene monomer.

If the amount of use is less than 0.05 parts by weight, the polymerization time is long, productivity is reduced, and at 3.0 parts by weight or more, the polymerization takes place in a short time, but the molecular weight of the polymer is lowered to obtain a satisfactory molded body.

In the present invention, the polymerization temperature is preferably 80 to 130 ° C., and the polymerization time is longer than 80 ° C., and when the temperature is 130 ° C. or more, the molecular weight is lowered to obtain a satisfactory molded body.

In the present invention it is also possible to use dispersants for the dispersion of styrene polymers or monomers. Dispersants that can be used at this time include water-soluble high molecular materials such as polyvinyl alcohol, methyl cellulose, and inorganic materials that are poorly soluble in water such as calcium phosphate and magnesium pyrophosphate.

At this time, it is good to use a dispersant in 0.05 to 4.0 parts by weight based on water.

In addition, dispersion aids, such as alkylbenzenesulfonic acid soda and sodium dodecylbenzenesulfonic acid which are anionic surfactants, can be used with 0.08-0.2 weight part with respect to water. The stirring speed of the reactor is 100 ~ 145 rpm.

Subsequently, the foamed granules are obtained by impregnating the polymer particles having a particle size distribution of 85 to 93% in the 16 to 30 mesh obtained by the polymerization step after impregnating with the blowing agent.

The styrene polymer obtained by the conventional suspension polymerization method requires aging for a long time of 7 days or longer in order to obtain a stable bubble structure of the foamed granules after impregnating the foaming agent. As a long time of aging takes place, the foaming force is lowered. However, since the particles of the polymer obtained by the present invention are matured within one day after impregnation, foaming up to a high magnification and a constant magnification is possible and productivity can be increased by shortening the process cycle.

As a result of the shortening of the aging time, the foaming force of the styrene particles obtained by the present invention ((a) of FIG. 2) is less than that of the styrene particles obtained by the conventional method ((b) of FIG. 2). Very good can be observed. (See Figures 2 (a) and (b).)

As the blowing agent used in the present invention, aliphatic hydrocarbon-based pentane and butane which do not dissolve the styrene polymer particles are preferable.

When the blowing agent is added, it is preferable to add the styrene monomer after the polymerization is completed.

In addition, in the present invention, flame retardants such as tribromophenylaryl ether, hydroxybromocyclododecane, pentabromomonochlorocyclohexane, and tetrabromocyclooctane, and paraffin chloride and ethylene depending on the use of the finally obtained expandable resin particles. Internal lubricants, such as bisamide and polystyrene wax, can also be used.

The present invention will be described in more detail with reference to the following Examples.

Example 1

33 kg of styrene monomer was added to a 100-liter reactor and stirred at 130 rpm to dissolve 3.3 kg of styrene polymer particles having a particle size of 45 mesh or less, followed by 40 kg of pure water and 46 g of magnesium pyrophosphate and 1.85 g of dodecylbenzenesulfonate as a dispersant. Was added.

Separately, 100 g of benzoyl peroxide and 18 g of t-butyl peroxide were dissolved in 2 kg of styrene monomer and introduced into the reactor for about 30 minutes. Thereafter, the dispersion state of the suspension was confirmed while maintaining the temperature in the reactor at 85 ° C., and then polymerized at 90 ° C. for 3 hours, followed by postpolymerization at 130 ° C. for about 1 hour 30 minutes.

After completion of the polymerization, the mixture was cooled to 25 ° C. or lower, and then hydrochloric acid was added to neutralize the suspension, and the particles of the polymer were measured and shown in Table 1 and FIG. 1. As can be seen from Table 1 and FIG. 1, in this example, a particle size distribution of 90% was obtained in the central particle size range of 16 to 30 mesh.

Meanwhile, 30 kg of the polymer particles thus obtained were impregnated with 40 kg of water, 20 g of magnesium pyrophosphate, and 1.5 g of dodecyl benzene sulfonic acid soda added to a reactor having a capacity of 100 L with stirring. As the blowing agent, 3.0 kg of pentane was added and impregnated at 70 ° C. for 5 hours, and then slowly cooled to 20 ° C., and electrical particles were taken out to measure aging and foaming power.

The aging progress state of the impregnated particles was taken out from the reactor, and the gas volatilization was measured using a gas chromatography apparatus after leaving for a predetermined time in an atmospheric state at room temperature, and the results are shown in FIG. 2 and Table 2. As can be seen from FIG. 2 and Table 2, the gas volatile content of the particles prepared by the present invention is 7.6% after 1 day, whereas the polymer particles produced by the existing suspension method are 6.0%, and the state of ripening is very high. Slow progress was found.

In addition, as a result of measuring the foamability of the particles, the polymer particles according to the present invention had a foamability of 70 times for 5 minutes, whereas the particles of the polymers according to the conventional suspension polymerization method (Comparative Example 1 and Comparative Example 2) had a foaming force up to a constant magnification of 60 times. It was observed that the time taken for the falling and firing was longer.

The foamed particles thus obtained were filled into a mold having a size of 30 cm x 40 cm x 10 cm at 0.9 kg / cm 2 of water vapor pressure to obtain a molded article with good fusion and surface condition without melting the molded article. The molding conditions and the surface state of the molded article are shown in Table 2.

Example 2

Under the same conditions as in Example 1, 33 kg of styrene monomer was added thereto and stirred at 130 rpm, and the particles were dissolved in 5.0 kg of styrene polymer allele of 6 mesh or more size. As a result of polymerization by adding 2.0 g, a polymer having 87% of uniform particles in the central particle size range of 16 to 30 mesh was obtained.

As a result of impregnating the particles thus obtained under the same conditions as in Example 1, a foam having very good gas volatilization of 7.5% and a 5-minute foamability of 72 times after one day aging was obtained. Furthermore, when this foam was shape | molded by the water vapor pressure of 0.9 kg / cm <2>, the molded object with a favorable surface state was obtained by 80% of fusion | melting.

Example 3

Under the same conditions as in Example 1, 32 kg of styrene polymer was added thereto and stirred at 135 rpm, and 6.6 kg of styrene polymer intermediate particles having a particle size of 6 to 45 mesh were dissolved. 2.5 g of sodium sulfonic acid was added.

Separately, 100 g of benzoyl peroxide, 18 g of t-butylperbenzoate, and 80 g of dicumyl peroxide were dissolved in 2 kg of styrene monomer and charged in a reactor for about 30 minutes.

In addition, 40 g of pentabromonochloro hexane, a flame retardant, was dissolved in 1 kg of pure water, and charged into a reactor, and polymerization was performed under the same conditions as in Example 1.

As a result, a polymer having 90.3% of uniform particles in the central particle size range of 16 to 30 mesh was obtained. The particles thus obtained were impregnated under the same conditions as in Example 1 to obtain a very good flame retardant foam having a gas volatile content of 7.48% and a 5-minute foamability of 74 times after 1 day aging. Furthermore, when this foam was shape | molded by the water vapor pressure of 0.9 kg / cm <2>, the molded object with 82% fusion and a favorable surface state was obtained.

Example 4

Under the same conditions as in Example 1, adding 30 kg of styrene monomer and stirring at 140 rpm, dissolving 8.0 kg of styrene polymer microparticles with a particle size of 70 mesh or less, followed by 40 kg of pure water and 48 g of magnesium pyrophosphate and dodecylbenzene sulfonic acid As a result of polymerizing by adding 2.0 g of soda, a polymer having 89% of uniform particles in the central particle size range of 16 to 30 mesh was obtained. The particles thus obtained were dissolved in 1 kg of water under 40 g of blue dye under the same conditions as in Example 3, and impregnated. After aging for 1 day, a foam having a gas volatile content of 7.56% and a 5-minute foamability was 70 times obtained.

Comparative Example 1

40 kg of pure water and 46 g of magnesium pyrophosphate and 1.85 g of dodecyl benzene sulfonic acid soda were added to a 100-L reactor, and 38 kg of styrene monomer was added thereto while stirring at 130 rpm.

Separately, 100 g of benzoyl peroxide and 18 g of t-butyl perbenzoate were dissolved in 2 kg of styrene monomer and introduced into the reactor for about 30 minutes. Thereafter, the mixture was polymerized at 90 ° C. for 7 hours and then post-polymerized at 130 ° C. for about 1 hour 30 minutes.

After the polymerization was completed, the mixture was cooled to 25 ° C. or lower, acid was added to neutralize the suspension, and the particle size of the polymer particles was measured. As a result, polymer particles having a wide particle size distribution of 75% in the central particle size range of 16 to 30 mesh were prepared.

The polymer particles thus obtained were impregnated under the same conditions as in Example 1 to measure the aging state and the foamability. As a result, the gas volatilization was 5.8% after 1 day of aging, and the aging progressed slowly. It shows low foamability. In addition, the internal bubble state of the blowing agent is examined under a microscope, it can be seen that it has a very non-uniform bubble structure. (Figure 3 (b)).

The foamed particles were molded under the same conditions as in Example 1 to obtain a molded article having a long cooling time during molding, having an internal fusion of 75% or less, and having a poor surface state.

Comparative Example 2

40 kg of pure water and 46 g of magnesium pyrophosphate and 1.85 g of dodecylbenzene sulfonic acid soda were added to a 100-L reactor, and 38 kg of styrene monomer was added thereto while stirring at 140 rpm.

Separately, 100 g of benzoyl peroxide and 18 g of t-butyl perbenzoate were dissolved in 2 kg of styrene monomer and introduced into the reactor for about 30 minutes. Thereafter, the temperature in the reactor was polymerized at 90 ° C. for 7 hours and then post-polymerized at 130 ° C. for about 1 hour 30 minutes.

After the polymerization was completed, the mixture was cooled to 25 ° C. or lower, acid was added to neutralize the suspension, and the particle size of the polymer particles was measured. As a result, polymer particles having a broad particle size distribution of 74% in the central particle size range of 16 to 30 mesh were prepared.

The polymer particles thus obtained were impregnated under the same conditions as in Example 1 to measure the aging state and the foamability. As a result, the volatile gas volatilization was 6.02% after 1 day of aging, and the aging was slowed. The 5 minute foamability was 60 times lower. It exhibits foamability. In addition, the internal bubble state of the foam was examined, and it was observed that it had a very non-uniform bubble structure.

Claims (4)

5 to 30 parts by weight of an allele of 6 meshes or more, an intermediate particle of 6 to 45 meshes or a particle size of 45 meshes or less is dissolved in 100 parts by weight of a styrene monomer as a polymerization raw material, and benzoyl peroxide as a catalyst for polymerization, Suspension polymerization was carried out using 0.05 to 3.0 parts by weight of t-butylperbenzoate or dicumyl peroxide to prepare polymer particles. A method for producing expandable polystyrene resin particles comprising 0.08 to 0.1 parts by weight of sodium benzenesulfonate and 2 to 15 parts by weight of pentane or butane as a blowing agent. The method of claim 1, wherein the styrene polymer particles are styrene homopolymers or styrene copolymers such as copolymers of styrene and acrylonitrile or copolymers of styrene and α-methylstyrene. Manufacturing method. The method for producing polystyrene-based resin particles according to claim 1, wherein the styrene monomer is a mixture of styrene monomer or acrylonitrile or α-methyl styrene containing styrene monomer as a main component. According to claim 1, Tribromophenylaryl ether, hydroxybromocyclododecane, pentabromomonochlorocyclohexane, tetrabromocyclooctane alone or two or more flame retardant based on 100 parts by weight of the styrene monomer A method for producing expandable polystyrene-based resin particles, characterized in that 0.1 to 3 parts by weight is added by mixing.