JP3346125B2 - Expandable ABS resin particles and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable ABS resin particles suitable for a foamed molded article having excellent chemical resistance and toughness, especially excellent surface appearance and heat resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Polystyrene foams have excellent cushioning properties and heat insulation properties, and are easy to mold, but are inferior in heat resistance, chemical resistance and toughness. have. Such a disadvantage of the polystyrene foam can be solved by the ABS resin foam.
Attention has been focused on resin foams.

As a method for producing foamed ABS resin particles, for example, ABS resin particles are dispersed in an aqueous medium in a closed container, and then a volatile foaming agent is added.
After impregnation at a temperature higher than the glass transition temperature of the BS resin by 20 ° C. or more, one end of the closed vessel is opened, and the ABS resin and the aqueous medium are discharged to a lower pressure region than in the closed vessel (Japanese Patent Laid-Open No. 63-63). However, this method requires large-scale equipment and has a problem that the production cost is unavoidable because it is transported from the manufacturer to the processing manufacturer in the form of already expanded particles. is there.

On the other hand, as a method for producing expandable ABS resin particles, a method using an ABS resin having a special structure, or a method for defining the amount of an internal volatile foaming agent and the amount of water in the ABS resin particles (Japanese Patent Publication No. 57-57). -48380, JP-A-50-
No. 12156) has been proposed. Since the former method has a disadvantage that the ABS resin is limited, the present inventors have studied the latter method.

However, in order to produce foamable ABS resin particles according to the latter method, the ABS resin is dispersed in an aqueous medium and impregnated with a volatile foaming agent. In some cases, the volatile foaming agent necessary for foaming may not be sufficiently impregnated, and it is necessary to increase the amount of the volatile foaming agent added. However, when the amount of the volatile foaming agent added is increased, the ABS resin particles dispersed in the aqueous medium are likely to coagulate with each other, resulting in a problem in suspension stability. In addition, when foamable ABS resin particles having a large internal moisture content are foamed, the foam size and the structure of the foamed particles greatly change with the aging of the internal moisture content, so that foamed particles having a constant cell structure can be obtained. It was hard to be. Furthermore, even if the internal moisture is reduced by heating the expandable particles, bubbles near the surface of the expandable particles become finer, and a thick non-foamed layer is formed on the surface of the expandable particles. It was found that the surface of the molded article shrank and melted, and an ABS foam having a beautiful surface appearance could not be obtained.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the internal water content in the resin particles after impregnation with the blowing agent has been reduced to a certain amount or less. By making the non-foamed layer on the particle surface when the resin particles are foamed 30 times less than a certain amount, 300 g /
A that can be foamed to a density of 1 l or less and has a clean surface appearance
The present inventors have found that expandable ABS resin particles suitable for producing a BS resin foam can be obtained, and have completed the present invention.

That is, the present invention relates to foamable ABS resin particles containing a foaming agent, wherein the resin particles have an internal water content of 5% by weight or less and expand the resin particles 30 times. The foamable ABS resin particles are characterized in that the non-foamed layer on the surface of the particles at the time of contact is 50 μm or less. Here, the internal water content in the resin particles is preferably 4% by weight or less.

Here, the non-foamed layer on the surface of the particles is 10
It is preferably about 30 μm. Further, the present invention relates to a method for obtaining the expandable ABS resin particles, wherein AB
In a method for producing expandable ABS resin particles by dispersing S resin particles in an aqueous medium in a closed container and impregnating with a volatile foaming agent, at least when the volatile foaming agent is impregnated, the concentration with respect to the aqueous medium is at least 0.1%. This is a method for producing expandable ABS resin particles, characterized in that an electrolyte is present in an amount of from 0.01 to 2 mol / l.

Here, the concentration of the electrolyte to be present in the aqueous medium is preferably 0.03 to 1 mol / l. Here, too, the temperature of the aqueous medium is preferably from 70 to 140 ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The foamable ABS resin particles of the present invention are foamable ABS resins containing a foaming agent, and have an internal water content of 5% by weight or less, preferably 4% by weight or less. And the non-foamed layer on the particle surface when the resin particles are foamed 30 times is 50 μm or less, preferably 10 to 30 μm.

If the internal water content in the resin particles is too large, there arises a problem that the surface appearance such as shrinkage and melt is deteriorated when the molded article is formed into a foam. If the non-foamed layer on the particle surface is too thick, not only is the foamability and moldability hardly improved, but also the surface appearance deteriorates, such as shrinkage and melt. Conversely, if the non-foamed layer on the particle surface is too thin, there is a possibility that a melt may occur depending on the steam pressure during molding. Therefore, it is necessary to prevent the obtained expandable resin particles from being excessively dried at a high temperature.

The internal water content is determined by placing the precisely weighed particles in dry methanol and performing a titration with a Karl Fischer reagent while stirring to determine the surface water content. The separately weighed particles are dissolved in dry toluene. While stirring, titration was performed with a Karl Fischer reagent to determine the total amount of moisture attached to and contained in the expandable ABS resin particles. From the determined total amount of moisture, the surface moisture determined above that adhered to the particle surface was determined. It is obtained as a value obtained by subtracting the amount.

The non-foamed layer according to the present invention refers to a non-foamed portion existing from the surface of the foamed particles to the bubbles in the vicinity of the surface. And the thickness of the non-foamed layer was randomly measured at 10 locations from an optical microscope photograph, and the average thickness was determined.

The ABS used in the method for producing the expandable ABS resin particles of the present invention or the expandable ABS resin particles described below.
Examples of the resin include butadiene polymer, a copolymer of butadiene and a copolymerizable vinyl monomer, and ethylene-
In the presence of rubbery polymers such as propylene-diene copolymers, block copolymers of butadiene and aromatic vinyl monomers, and copolymers of acrylic and methacrylic esters and copolymerizable vinyl monomers. For example, one or more aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, and one or more vinyl cyanide such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, etc. Examples thereof include those obtained by polymerizing a monomer by a method such as emulsion polymerization or bulk polymerization. During this polymerization, monomers such as maleic anhydride, maleic acid, itaconic acid, N-phenylmaleimide, and (meth) acrylic acid ester copolymerizable with an aromatic vinyl monomer or a vinyl cyanide monomer may be further polymerized. good. Further, a commercially available product may be used.

Further, ABS resins include inorganic fillers such as talc, clay, calcium carbonate and titanium oxide, antioxidants, antistatic agents, ultraviolet absorbers, carbon black, aluminum stearate, zinc stearate,
Lubricant such as -t-butyl aluminum benzoate and the like, flame retardant such as tris (dibromopropyl) phosphate, pentabromodiphenyl ether, tetrabromobutane, dibromoethyl benzol, 1,2,5,6,9,10-hexabromocyclodecane May be contained.

The ABS resin particles used in the present invention are:
It is a particle having a size of 0.5 to 5 mm obtained by granulating the BS resin by strand cutting, underwater cutting, hot cutting, or the like, and the shape may be spherical or cylindrical. As one method for obtaining the expandable ABS resin particles of the present invention described above,
ABS resin particles are dispersed in an aqueous medium in a closed container in the presence of a suspending agent, and impregnated with a volatile foaming agent to form foamable ABS.
In the method for producing resin particles, at least at the time of impregnation of the volatile blowing agent, the concentration with respect to the aqueous medium is 0.0
A method for producing expandable ABS resin particles, characterized in that an electrolyte is present in an amount of 1 to 2 mol / l.

In the present invention, as the suspending agent for dispersing the ABS resin particles in an aqueous medium, a commercially available suspending agent may be used or may be synthesized. For example, polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, etc. And water-insoluble inorganic salts such as magnesium pyrophosphate and tribasic calcium phosphate, etc., and these may be used in combination with a surfactant. In addition,
When a poorly water-soluble inorganic salt is used, it is preferable to use an anionic surfactant such as sodium dodecyl sulfate or sodium dodecylbenzenesulfonate in combination.

The amount of the suspending agent used is 100 parts of ABS resin particles.
0.01 to 5.0 parts by weight with respect to parts by weight is preferable. In the above-mentioned combination system of the poorly water-soluble inorganic salt and the anionic surfactant, the poorly water-soluble inorganic salt is added to 100 parts by weight of the ABS resin particles. The amount is preferably 0.05 to 3.0 parts by weight, and the anionic surfactant is preferably 0.0001 to 0.5 parts by weight.

The electrolyte used in the production method of the present invention comprises:
Any substance capable of dissociating ions in an aqueous solution may be used.
Lithium chloride, sodium chloride, magnesium chloride, potassium chloride, calcium chloride, ammonium chloride, sodium sulfate, magnesium sulfate, potassium sulfate, calcium sulfate, aluminum sulfate, ammonium sulfate, sodium nitrate, magnesium nitrate, potassium nitrate, calcium nitrate, ammonium nitrate, sodium carbonate Inorganic salts such as magnesium carbonate, potassium carbonate, calcium carbonate and ammonium carbonate, or alkali metal salts of water-soluble carboxylic acids such as potassium acetate, sodium acetate, sodium octoate, sodium benzoate and disodium succinate And the like. Particularly, alkali metal salts such as sodium and potassium are preferable because the effect of reducing the internal water content is large with a small amount of added weight, and the foamable ABS resin particles of the present invention can be easily obtained. Sodium is preferable because it has the above-mentioned effects and can be obtained in large quantities at low cost industrially.

The amount of the electrolyte added to the aqueous medium is 0.01 to 2 mol / l, preferably 0.03 to 1 mol / l, based on the aqueous medium. 0.01mol
When the concentration is less than / 1, a sufficient effect of reducing the internal water content in the obtained resin particles cannot be obtained. When the concentration is more than 2 mol / l, not only the effect of reducing the internal water content corresponding thereto is not obtained, but also depending on the type of electrolyte, the suspension stability may be significantly impaired and the electrolyte may be easily aggregated.

The time for adding the electrolyte is not particularly limited. The electrolyte may be added from the beginning or may be added during the impregnation of the foaming agent. However, it is usually preferable to add the electrolyte from the beginning. Further, the temperature of the aqueous medium is from 70 to 140 from the viewpoint of preventing the setting of the ABS resin particles and impregnating the foaming agent into the ABS resin particles.
C is preferred. As volatile foaming agents, propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, hexane, trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, chloromethane, chloroethane, dichloromethane, methanol, diethyl Organic compounds having a boiling point of 80 ° C. or lower such as ether can be used alone or in combination of two or more.

The blowing agent is usually supplied in such an amount that the content of the blowing agent in the produced polymer particles becomes 1 to 20% by weight. In addition, foaming properties can be enhanced by adding a solvent such as a nonvolatile plasticizer or volatile cyclohexane, xylene, or toluene.

The foamable AB thus obtained is
If the S resin particles are dried at a high temperature for a long period of time, a thick non-foamed layer is likely to be formed on the surface of the particles. Therefore, the drying must be performed to such an extent that a non-foamed layer having a thickness exceeding 50 μm is not generated. Here, drying to such an extent that a non-foamed layer having a thickness exceeding 50 μm is not generated means that after extracting the ABS resin system impregnated with the volatile foaming agent from the closed container, for example, after centrifuging, the nitrogen or The reduction rate of the internal water content before and after the step of removing the water attached to the bead surface with air or the like is within 30%. That is, the reduction rate of the internal water content is the ratio of the internal water content reduction due to air drying of nitrogen or air to the internal water content immediately after the ABS resin particles impregnated with the foaming agent are centrifuged. Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

[0024]

【Example】

Example 1 A 30 mm uniaxial extruder for a raw material ABS resin having a composition weight ratio of styrene: butadiene: acrylonitrile = 62.9: 14.6: 22.5, an average particle diameter of rubber particles of 0.14 μm, and a softening temperature of 102 ° C. After being melted, ABS resin particles of 1.2 mg / piece were cut by a water cut die.

In a 3 liter autoclave equipped with a stirrer, 600 g of ion-exchanged water and sodium pyrophosphate 4.
0 g and 8.0 g of magnesium sulfate were added to synthesize magnesium pyrophosphate, and then 0.45 g of sodium dodecyl sulfate, 27 g of sodium chloride and the obtained ABS
600 g of resin particles were added, the temperature was raised to 120 ° C. over 1 hour, and after reaching 120 ° C., 66 g of pentane was added. After it was kept at 120 ° C. for 10 hours as it was, it was cooled to room temperature. The concentration of the electrolyte (total of sodium chloride and sodium sulfate by-produced during the synthesis of magnesium pyrophosphate) in the ion-exchanged water corresponds to 0.54 mol / l.

Foamable ABS obtained from autoclave
The resin particles were taken out, the magnesium pyrophosphate adhered to the surface was dissolved with nitric acid, washed with water, and then centrifuged. Next, the expandable ABS resin particles are placed in a metal cylindrical container having an inner diameter of 10 cm and a height of 25 cm, on which a metal mesh having a mesh of 0.1 mm is attached on the upper and lower sides, and dried nitrogen at 20 ° C. at a flow rate of 500 liters per minute. Was blown dry from the bottom for 10 minutes.

0.2 parts by weight of zinc stearate, 0.1 parts by weight of glyceride stearate, and 0.01 parts by weight of bis (hydroxyethyl) alkylamine as an antistatic agent per 100 parts by weight of the obtained expandable ABS resin particles. After mixing and coating, the mixture was charged into a batch-type foaming machine equipped with a stirrer, and steam having a pressure of 1.0 kgf / cm ² was blown therein, and heated and foamed up to 30 times to obtain foamed particles of ABS resin.

The foamed particles thus obtained were filled in a molding die, and heated at a steam pressure of 0.8 kgf / cm ² for 15 seconds to obtain a foamed molded product. Rubber particle size of ABS resin,
The softening temperature, the internal moisture content in the expandable resin particles obtained as described above, the internal moisture reduction ratio, the volatile content and the thickness of the non-foamed layer, and the surface appearance and heat resistance of the foamed molded article are determined by the following methods. evaluated.

Measurement of rubber particle size of ABS resin: In a TEM observation photograph, the particle size of 100 to 200 rubber particles was measured and calculated by the following equation. Average particle size = ΣNiD ² / ΣNiD Softening temperature: Vicat softening temperature measured according to JIS K7206. Measurement of volatile content: After the weighed sample was heated at 120 ° C. for 4 hours, it was weighed again, and the change in weight before and after heating was taken as the volatile content.

Internal water content: The precisely weighed particles are placed in dry methanol, and while stirring, titration is performed with a Karl Fischer reagent to determine the surface water content. The separately weighed particles are dissolved in dry toluene and stirred. Then, titration was performed with a Karl Fischer reagent to determine the total amount of water attached to and contained in the expandable ABS resin particles, and the above-determined surface moisture amount attached to the particle surface was subtracted from the determined total moisture amount. Value.

Internal moisture reduction ratio: A impregnated with blowing agent
Immediately after the BS resin particles are centrifuged, and after air drying such as nitrogen or air, the internal water content is measured in the same manner as above, and the difference between these internal water contents is determined by the internal water content measured in the former. I sought it. Thickness of non-foamed layer: A thin section of the foamed particle cross section was prepared, and the thickness of the non-foamed layer at 10 locations was randomly measured from an optical micrograph and averaged.

Surface appearance: The surface appearance of the foamed molded article was visually evaluated according to the following criteria. ；: Almost no shrinkage, melt, or gap. Δ: Shrinkage, melt, gaps are observed. X; remarkable shrinkage, melt, and gaps are observed. Heat resistance: The foam molded article cut into a size of 50 × 50 × 25 mm was heated at 90 ° C. for 22 hours, and the case where the deformation ratio before and after heating was less than 1% was ○, and the case where it was 1% or more was ×.

Example 2 An ABS resin having a composition weight ratio of styrene: butadiene: acrylonitrile: 62.8: 15.0: 22.2, an average particle size of rubber particles of 0.21 μm, and a softening temperature of 97 ° C. is used as a raw material. Others were performed similarly to Example 1. Example 3 Except that an ABS resin having a composition weight ratio of styrene: butadiene: acrylonitrile: 62.0: 15.1: 22.9, an average particle diameter of rubber particles of 0.20 μm, and a softening temperature of 100 ° C. was used as a raw material. It carried out like Example 1.

Example 4 An ABS resin having a composition weight ratio of styrene: butadiene: acrylonitrile: 61.2: 16.5: 22.3, an average particle diameter of rubber particles of 0.30 μm, and a softening temperature of 95 ° C. is used as a raw material. Others were performed similarly to Example 1. Example 5 600 g of ABS resin pellets used in Example 1, 900 g of ion-exchanged water, 4.5 g of tribasic calcium phosphate, 0.045 g of sodium dodecylbenzenesulfonate, and 45 g of sodium chloride were placed in a 3 liter autoclave. Performed similarly. The concentration of the electrolyte in the aqueous medium is 0.85 mol / l.

EXAMPLE 6 600 g of the ABS resin pellets used in Example 1, 900 g of ion-exchanged water, 4.0 g of sodium pyrophosphate, 8.0 g of magnesium sulfate, 0.4 g of sodium dodecyl sulfate
5 g was placed in a 3 liter autoclave, and the same procedure as in Example 1 was carried out. The concentration of the electrolyte in the aqueous medium is 0.03
mol / l.

Example 7 600 g of the ABS resin pellets used in Example 4, 900 g of ion-exchanged water, 4.0 g of sodium pyrophosphate, 8.0 g of magnesium sulfate, 0.4 g of sodium dodecyl sulfate
5 g and 9 g of sodium sulfate were put in a 3 liter autoclave, and the same operation as in Example 1 was performed. The concentration of the electrolyte in the aqueous medium is 0.10 mol / l. Example 8 It carried out similarly to Example 1 except having used 63 g of sodium chloride. The concentration of the electrolyte in the aqueous medium is 1.22 mo
1 / l.

COMPARATIVE EXAMPLE 1 As in Example 1, 600 g of the ABS resin pellets used in Example 1, 900 g of ion-exchanged water, 4.5 g of tribasic calcium phosphate, and 0.045 g of sodium dodecylbenzenesulfonate were placed in a 3 liter autoclave. I went to.

Comparative Example 2 As in Example 1, 600 g of the ABS resin pellets used in Example 1, 900 g of ion-exchanged water, 4.5 g of tribasic calcium phosphate, and 0.045 g of sodium dodecylbenzenesulfonate were placed in a 3 liter autoclave. I went to. However, 150 g of pentane was added. When the ABS resin particles were extracted after the impregnation with the volatile foaming agent, the particles were lightly coagulated. The particles were loosened by hand, and then used for post-treatment (acid treatment, drying, etc.), foaming, and molding.

Comparative Example 3 In order to reduce the internal water content of the expandable ABS resin particles obtained in Comparative Example 2, drying was carried out for 60 minutes by a nitrogen stream at 50 ° C. In each of the above Examples and Comparative Examples, the electrolyte concentration, the drying conditions, the internal water content of the obtained expandable resin particles, the internal water reduction ratio, the thickness of the non-foamed layer, the volatile content, the surface appearance of the foamed molded product, and heat resistance The properties were as shown in Table 1.

That is, it can be seen that the expandable ABS resin particles of the present invention (Examples 1 to 8) have excellent expandability and moldability without depending on the softening temperature of the raw material ABS resin.
On the other hand, when the internal water content is high, the volatile foaming agent is not sufficiently impregnated and foamable ABS having excellent foamability and moldability is obtained.
No resin particles were obtained (Comparative Example 1). Also, even if the internal moisture content is forcibly reduced by heating, a large amount of the volatile foaming agent is required at the time of impregnation in order to impregnate the volatile foaming agent sufficient for foaming. It can be seen that coagulation easily occurs during the impregnation of, and the surface appearance is not so good (Comparative Example 3).

[0041]

[Table 1]

[0042]

According to the present invention, the foam molded article molded using the foamable ABS resin particles of the present invention is particularly excellent in surface appearance and heat resistance.

[Brief description of the drawings]

FIG. 1 is an optical microscope photograph (50 ×) of a cross section of a foamed particle when the expandable ABS resin particle of Example 1 is foamed 30 times.
It is.

FIG. 2 is an optical microscope photograph (50 ×) of a cross section of the expanded beads when the expandable ABS resin particles of Comparative Example 3 are expanded 30 times.
It is.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-50-12156 (JP, A) JP-A-58-208333 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 9/16

Claims (6)

(57) [Claims] 1. An expandable ABS resin particle containing a foaming agent, wherein the internal water content in the resin particle is 5% by weight or less and the resin particles are expanded 30 times. Foamable ABS resin particles, characterized in that the non-foamed layer on the surface is 50 μm or less. 2. The expandable ABS resin particles according to claim 1, wherein the internal water content in the resin particles is 4% by weight or less. 3. The non-foamed layer on the particle surface has a thickness of 10 to 30 μm.
The expandable ABS resin particle according to claim 1, which is: 4. A method for producing foamable ABS resin particles by dispersing ABS resin particles in an aqueous medium in a closed container and impregnating with a volatile foaming agent, wherein at least when the volatile foaming agent is impregnated, an aqueous medium is used. Concentration of 0.01
A method for producing expandable ABS resin particles, wherein an electrolyte is present in an amount such that the amount becomes 2 mol / l. 5. The method for producing expandable ABS resin particles according to claim 4, wherein the concentration of the electrolyte to be present in the aqueous medium is 0.03 to 1 mol / l. 6. The method for producing expandable ABS resin particles according to claim 4, wherein the temperature of the aqueous medium is 70 to 140 ° C.