JPH0277438A - Foamable styrene based resin granule for fish box and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title granule having surface coated with a surfactant, definite releasing ratio of foaming agent contained in a resin and water content, capable of complete and mutual melt-sticking of foamed granules and advantageously applicable also in a mold for article (e.g., fish box) having thin and complicate shape. CONSTITUTION:The aimed foamable styrene based resin granule for fish box, etc., wherein the surface of the foamable styrene based resin granule containing 1-20 pts.wt. foaming agent in 100 pts.wt. styrene based resin particle is coated with 0.01-0.3 pts.wt. non-ionic surfactant having 7-15 HLB(hydroiphilic-lipophilic balance) based on 100 pts. resin particle and surface-attached water content is <=0.5wt.%, preferably <=0.1wt.% and releasing ratio of foaming agent contained in the above-mentioned resin particle is 3-40wt.%, preferably 6-25wt.%. As the non-ionic surfactant, polyoxyethylenealkyl ether or polyoxyethlenealkylphenol ether is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to expandable styrenic resin particles and a method for producing the same. More specifically, in the production of molded products with a cell structure, foamed particles during the molding process are completely fused together at their interfaces, making it possible to produce molded products with as few interparticle gaps as possible. This invention relates to expandable styrenic resin particles for use in buckets, etc., and a method for producing the same.

[Prior art and problems]

Expandable styrene resin particles can be obtained by impregnating polystyrene resin particles with a blowing agent, i.e., an easily evolvable aliphatic hydrocarbon that only slightly swells the particles, such as n-penkune, in an aqueous suspension; Alternatively, it is produced by impregnating polystyrene resin particles with a gaseous blowing agent such as butane or propane at room temperature in an aqueous suspension together with a small amount of a solvent such as toluene or cyclohexane that dissolves the particles.

The expandable styrenic resin particles thus produced are suitable for industrially and economically producing zero-expandable styrenic resin moldings, which are used as raw materials for manufacturing expanded styrene resin moldings. The styrene-based resin particles are made into pre-expanded particles using water vapor or the like, and the pre-expanded particles are filled into a closed mold having a desired shape with a large number of small holes in the wall surface. A method of ejecting a heating medium such as water vapor from the holes to heat the pre-expanded particles to a temperature higher than the softening point of the particles to fuse them together, and then taking them out from the mold to obtain a foamed styrene resin molded article in the desired shape. is common.

The molded body obtained by the above method is formed by the pre-expanded particles further foaming in the mold and fusing with each other while filling the gaps between the particles, but conventionally it has been impossible to obtain a molded body with no gaps between the particles. In particular, the filling rate of the pre-expanded particles near the mold wall surface -1 is lower than in other parts, so it is difficult to completely fill the gaps between the particles, and as a result, the particles appear on the surface of the resulting molded product. The gap exists as a depression.

The presence of such particle gaps on the surface of the molded object impairs the appearance of the molded object and causes a decrease in the strength of the molded object.
Particularly in recent years, molded objects such as fish buckets are often used with printing, but in this case, ink does not adhere to the gaps between the particles, so the areas where the ink does not adhere remain the white color of the expanded particles. Ink may be scattered, or conversely, ink may accumulate in the gaps between particles and appear as extremely dark dots, significantly impairing the appearance of the print and lowering its commercial value.

As a method for reducing the particle gaps in such molded bodies,
A method is known to increase the cell diameter of the foamed particles to thicken the surface cell membrane of the foamed particles, suppress the collapse of the surface cell membrane during heat molding, maintain the foaming power of the pre-expanded particles, and reduce the gap between particles. It is being

However, when using such a method, as the cell diameter increases, light scattering from the cell membrane of the molded product decreases, resulting in the molded product appearing dark, and there are limitations to the technology for increasing the cell diameter. Because of this, the surface cell membrane cannot reach the thickness necessary to completely fill the interparticle gaps, and as a result, the reality is that no satisfactory molded product with no interparticle gaps has yet been obtained. .

The present inventors developed a method to solve the above problem and filed a patent application (Japanese Patent Application Laid-Open No. 63-69844), the content of which is as follows:
The surface of expandable styrenic resin particles containing 1 to 20 parts by weight of a blowing agent in 100 parts by weight of styrenic resin particles has a HLB (hydrophilicity-lipophilic balance) Lipophil
eBalance))) The resin particles are coated with 0.01 to 0.3 parts by weight of a nonionic surfactant having a value of 7 or more, and the moisture adhering to the surface of the resulting coated resin particles is 0.5% by weight or less, and the resin particles The contents of the present invention include expandable styrenic resin particles characterized in that the dissipation rate of the blowing agent contained therein is 3 to 40% by weight, and a method for producing the same.

However, as a result of continued research, the expandable styrenic resin particles obtained by the above method were heated and foamed using a heating medium such as water vapor to produce pre-expanded particles, and the pre-expanded particles were shaped into desired shapes. The particles are then filled into a closed mold with a large number of small holes in the wall, and heated to a temperature above the softening point of the pre-expanded particles by ejecting a heating medium such as steam from the small holes in the mold. , fused together, cooled with water, released from the mold,
In a method for obtaining a foamed styrene resin molded article having a desired shape, when a certain mold is used, the filling of the pre-expanded particles into the mold is locally significantly inhibited, and shrinkage occurs in that part. The problem became clear. The specific mold is a mold that is thin and has a complicated shape, such as a fish tank, and in which a large amount of water used to cool the mold remains as water droplets on the wall surface of the mold.

[Means for solving problems]

In view of this situation, the present inventors aimed to improve the drawbacks of the above-mentioned conventional technology by completely fusion of foamed particles at their boundary surfaces during the molding process, and with the aim of reducing the gap between particles as much as possible. Expandable styrene that makes it possible to produce molded products of high quality, and does not cause filling defects with pre-expanded particles even in molds where a large amount of cooled water remains as water droplets on the wall, such as in molds such as Uokyo. As a result of intensive research in order to obtain resin particles based on the present invention, the present invention has been completed.

That is, the first aspect of the present invention is that the surface of expandable styrenic resin particles containing 1 to 20 parts by weight of a blowing agent in 100 parts by weight of styrenic resin particles is
HLB (1'l aqueous-lipophilic equilibrium (Hydroph)
ile-Lipophile Balance ) )
Nonionic surfactants with a value of 7 to 15 0. Coated with 1 to 0.3 parts by weight of O, the moisture adhering to the surface of the resulting coated resin particles is 0.5% by weight or less, and the dissipation rate of the blowing agent contained in the cough resin particles is 3 to 40% by weight. The second aspect of the present invention is to provide expandable styrenic resin particles for fish envelops, etc., which are characterized by: To 100 parts by weight of the resin particles, HLB
(Hydrophilic-lipophilic equilibrium (Hydrophile-L
ipophile Balance ) ) value is 7 to 1
After coating 0.01 to 0.3 parts by weight of the nonionic surfactant No. 5 in the form of an aqueous solution or aqueous dispersion, the water adhering to the surface of the coated resin particles and the resin particles are added to 3 to 40 parts by weight of the blowing agent. Each content includes a method for producing expandable styrene resin particles for fish snails, etc., which is characterized by performing a drying treatment to dissipate the weight percentage.

The expandable styrenic resin particles in the present invention are resin particles obtained by adding a blowing agent during polymerization and impregnating it after polymerization, such as a polymer of styrene alone or other polymers mainly composed of styrene Polymer particles made of a copolymer with a vinyl monomer, etc., containing a foaming agent that is liquid or gaseous at room temperature in the polymer core, or impregnated after polymerization, and that can be foamed by heating. . Of course, additives commonly used in i11 may be contained.

As the blowing agent, an easily volatile hydrocarbon having a boiling point lower than the softening temperature of the resin particles is used, and it is preferable that the blowing agent does not dissolve the resin particles or only slightly swells the resin particles. From these viewpoints, suitable blowing agents include low-boiling aliphatic hydrocarbons such as propane, butane, and pentane; The amount of the blowing agent, which may be used in place of hydrogen or a halogenated hydrocarbon such as methyl chloride or chlorofluorocarbon, is 1 to 20 parts by weight per 100 parts by weight of the styrene resin particles.

If it is less than 1 part by weight, the necessary expansion ratio cannot be obtained, and even if it exceeds 20 parts by weight, no further improvement in the degree of foaming can be expected.
On the contrary, it becomes uneconomical.

The nonionic surfactant used as a coating agent in the present invention has an HLB value of 7 to 15, preferably 9 to 13. Nonionic surfactants with an HLB of less than 7 tend to be oil-soluble, and this It cannot be used for the purpose of invention. Also H
When LB exceeds 15, the surface of the pre-expanded particles becomes hydrophilic, and the particles have a thin and complex shape like the side panels of a rain hat, so that a large amount of water that cools the mold remains as water droplets on the wall surface. In such a mold, insufficient filling of pre-expanded particles occurs, which is undesirable.

Therefore, examples of nonionic surfactants having an HL B value of 7 to 15 include water-soluble and water-dispersible polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl esters, and polyoxyethylene sorbitan alkyls. Examples include esters, which may be used alone or in combination of two or more. The coating agent is used in an amount of 0.01 to 0.3 parts by weight per 100 parts by weight of the expandable styrene resin particles. 0.0
If it is less than 1 part by weight, the effect of smoothing the surface of the molded product will not be sufficient, and if it exceeds 0.3 part by weight, the grain boundaries on the surface of the molded product will be in a molten state, resulting in poor appearance. The HLB value can be measured by the method described on pages 307 to 327 of the industrial book "Surfactant Handbook".

After coating the expandable styrenic resin particles with an aqueous solution or a nonionic surfactant dispersed in water, water is dried and the foaming agent containing the resin particles is dissipated. Coating with a liquid nonionic surfactant that does not contain water causes uneven coating and does not have any effect on smoothing the surface of the molded article.

As mentioned above, uniform coating is achieved with the aqueous solution or aqueous dispersion, and surprisingly, after coating, the surface moisture is dried to 0.5% by weight or less, preferably 0.1% by weight or less,
Furthermore, 3 to 40% by weight of the blowing agent contained, preferably 6 to 2%
The present inventors found that by performing a 5% by weight dissipation treatment, the surface of the molded product has no particle gaps and exhibits an excellent appearance.0 Surface moisture exceeds 0.5% by weight As a result, interparticle gaps appear on the surface of the molded product, resulting in poor appearance. In addition, if less than 3% by weight of the contained blowing agent escapes, the effect of smoothing the surface of the molded product is not sufficient, and if it exceeds 40% by weight, the grain boundaries on the surface of the molded product collapse, resulting in poor appearance. This reduces the value of the product.

There are various methods for coating the surfaces of expandable styrenic resin particles with the above-mentioned coating agent. An example is a method of mixing. In this case, it is okay to impregnate and coat the expandable styrenic resin particles with an antistatic agent, zinc stearate, talc, an agglomeration inhibitor during pre-foaming such as calcium carbonate, I8 water agent, etc. after coating treatment. Alternatively, as another coating method, expandable styrenic resin particles impregnated with a blowing agent in an aqueous QII liquid are dehydrated using a centrifugal dehydrator, and then a nonionic surfactant or an aqueous solution or dispersion thereof is coated. It is also advantageous to attach the compound to the surface of the resin particles using a blender or the like. In this case, the nonionic surfactant also has an antistatic effect, but other antistatic agents may be mixed and coated if necessary.

There are no particular limitations on the method for drying the moisture adhering to the expandable styrenic resin particles together with the nonionic surfactant.

There are various methods for dissipating the foaming agent contained in the foaming agent. The foaming agent contained in the expandable styrenic resin particles from which the attached moisture has been removed can be diffused. The treatment temperature is below the foaming temperature of the expandable styrenic resin particles, but is preferably 35° C. or higher from the viewpoint of productivity.The amount of dissipation of the foaming agent contained can be adjusted by the treatment temperature and treatment time.

Further, the dryer or the like can simultaneously dry the moisture adhering to the expandable styrenic resin particles together with the nonionic surfactant and dissipate the foaming agent containing the resin particles.

Moisture on the surface of resin particles can be measured using a Karl Fischer moisture meter using a methanol dehydrated solvent.

Further, the amount of foaming agent containing resin particles can be measured by a scattering method using a soaking dryer or the like.

[Action/Effect]

According to the present invention, filling defects of pre-expanded particles can be avoided even in molds that are thin and have a complicated shape, such as molds that have a complex shape and in which a large amount of water used to cool the mold remains as water droplets on the wall surface. It is possible to provide an excellent molded product in which the foamed particles are completely fused to each other without generation of foam particles, and there is substantially no particle gap. It is not necessarily clear why such an excellent molded product can be obtained according to the present invention, but the reason is that the coating material penetrates into the surface area of the expandable styrene resin particles during drying of water, and the surface area of the resin particles is This is thought to be due to the fact that the cell membrane on the surface of the pre-expanded particles becomes thicker due to the change in the composition of the surface portion due to the dissipation of the foaming agent contained therein, thereby increasing the heat resistance. Furthermore, the improvement in the ability to fill the mold is considered to be due to the selection of a nonionic surfactant that does not have a very high affinity for water.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Comparative Example 1 100 parts by weight of styrene monomer, 110 parts by weight of water, 0.15 parts by weight of tricalcium phosphate, and 0.005 parts by weight of sodium dodecylbenzenesulfonate in a pressure-resistant reactor equipped with a stirrer and a temperature detection tube. , pendyl peroxa 110.2
5 parts by weight, tertiary butyl barbenzoate! - 0.1 part by weight and nitrogen 0.5 kg / cII with stirring
Polymerization was carried out at ambient temperature of 90'C under I pressure for 5 hours.

Next, 1.8 parts by weight of cyclohexane and 8.5 parts by weight of butane were added, the temperature was raised to 105°C, and impregnation with the blowing agent was carried out for 6 hours. This was cooled to room temperature to obtain true spherical expandable polystyrene resin particles. After drying the resin particles, they were sieved to obtain particles of 14 to 20 meshes, and then 0.09 part of zinc stearate was added thereto, stirred with a ribbon blender, and then taken out.

The obtained expandable polystyrene resin particles were heated with steam in a batch pre-expanding machine to obtain pre-expanded particles with an apparent volume of about 60 times.

After drying the pre-expanded particles in the atmosphere for 24 hours,
Fillability of the pre-expanded particles into a mold and molding evaluation of surface particle gaps of the molded body were evaluated using a Burlstar 180 automatic molding machine (manufactured by Toyo Kikinzoku ■).

However, in order to strictly evaluate the filling property, the mold is HN-15 type (height 35C11, width 25 value, depth 2
0 am, thickness 2 cm), the thalassometry at the time of filling was 0, and the water cooling time was 1 minute and 30 seconds to create a state in which the mold was extremely wet. The evaluation results are shown in Table 1.

Examples 1 to 3, Comparative Example 2 Expandable styrenic resin particles 1 obtained in the same manner as Comparative Example 1
After uniformly applying 1 part of a 5% by weight aqueous solution of polyoxyethylene nonylphenol ether having an HLB of 13.3 to 00 parts by weight, the moisture was dried in a flash dryer, and then the water was dried at 40°C in a box-type ventilation dryer. 0-2 as shown
A blowing agent dissipation process was carried out for 0 minutes.

The obtained resin was evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

The contained blowing agent dissipation rate was determined by dividing the difference between the amount of blowing agent contained in the treated portion and the amount of blowing agent contained after treatment by the amount of blowing agent contained in the treated portion. In addition, the amount of blowing agent contained in each of the particles at that time was 150
The amount of weight loss when the sample was left in a soaking dryer at ℃ for 30 minutes was determined by dividing it by the initial weight. The surface moisture was measured using a Karl Fischer moisture meter.

Examples 6 to 9, Comparative Examples 3 to 5 Examples 1 to 3 except that the coating agent was changed as shown in Table 2.
It was evaluated in the same manner. The results are shown in Table 2.

Claims (1)

[Claims] 1. 1 to 2 blowing agents in 100 parts by weight of styrene resin particles
The surface of expandable styrenic resin particles containing 0 parts by weight of HLB [hydrophilicity-lipophilic equilibrium (Hydrophile-Lipophilic balance)
balance)] is coated with 0.01 to 0.3 parts by weight of a nonionic surfactant having a value of 7 to 15, and the surface adhesion moisture of the resulting coated resin particles is 0.5% by weight or less, and the resin 1. Expandable styrenic resin particles for use in fish cages, etc., characterized in that the dissipation rate of the blowing agent contained in the particles is 3 to 40% by weight. 2. The resin particles according to claim 1, wherein the nonionic surfactant is an ether type nonionic surfactant selected from polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, and mixtures thereof. 3. The resin particles according to claim 1, wherein the moisture content attached to the surface is 0.1% by weight or less. 4. The resin particles according to claim 1, wherein the blowing agent contained has a dissipation rate of 6 to 25% by weight. 5. 1 to 2 blowing agents in 100 parts by weight of styrene resin particles
0 parts by weight of expandable styrenic resin particles containing 0 parts by weight of HLB [hydrophilicity-lipophilic equilibrium
After coating 0.01 to 0.3 parts by weight of a nonionic surfactant having a value of 7 to 15 in an aqueous solution or aqueous dispersion state, the water adhering to the surface of the coated resin particles and the content of the resin particles are 1. A method for producing expandable styrenic resin particles for use in fish cages, etc., which comprises performing a drying treatment to dissipate 3 to 40% by weight of the foaming agent. 6. The production method according to claim 5, wherein the nonionic surfactant is an ether type nonionic surfactant selected from polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, and mixtures thereof. 7. After drying the moisture adhering to the surface of the coated resin particles to reduce the surface moisture to 0.5% by weight or less, a drying treatment in which the foaming agent containing the resin particles is evaporated at a temperature lower than the foaming temperature of the resin particles. 6. The manufacturing method according to claim 5. 8. The manufacturing method according to claim 5, wherein the drying of moisture adhering to the surface of the coated resin particles and the evaporation of the blowing agent contained therein are carried out simultaneously.