JPH08231748A - Rubber modified styrene-based polymer resin composition for extrusion forming, extruded and foamed sheet of the same resin and production of extruded and foamed sheet of the same resin - Google Patents

Abstract

PURPOSE: To provide a composition having high closed cell ratio and slight reduction in a blowing agent during storage, and capable of being readily extruded and expanded. CONSTITUTION: This rubber modified styrene-based polymer resin composition for extrusion foaming uses a rubber modified styrene-based polymer resin having <=1.3μm average particle diameter of rubber-like polymer particles, >=450,000 Z-average molecular weight of a styrene-based polymer and <=4wt.% methanol-soluble content as a resin component. The objective extruded and foamed rubber modified styrene-based polymer resin sheet is obtained by extruding and foaming the rubber modified styrene- based polymer resin composition for extrusion foaming containing a volatile blowing agent and has 0.05-0.2g/cm<3> and >=70% closed cell ratio. The objective method for producing the extruded and foamed rubber modified styrene-based polymer resin sheet comprises extruding and foaming the rubber modified styrene-based polymer resin composition containing the volatile blowing agent by using a tandem extruder consisting of a uniaxial one-stage extruder and a uniaxial two stage extruder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified styrene polymer resin composition for extrusion foaming, the same resin extrusion foaming sheet, and a method for producing the same resin extrusion foaming sheet. More specifically, secondary molding properties such as vacuum molding and pressure molding are good, and a rubber-modified styrene-based polymer resin composition for extrusion foaming, which is easily obtained as an extruded foam sheet having excellent flexibility and impact absorption, The present invention relates to the resin extruded foam sheet and a method for manufacturing the resin extruded foam sheet.

[0002]

2. Description of the Related Art Polystyrene-based resin foams are excellent in molding processability, surface glossiness, lightness, heat insulation, etc., and those with a thickness of 3 mm or less are called "polystyrene paper", and pre-packaged Widely used for bento boxes, bowls, trays and other containers. However, because the conventional packaging container using polystyrene paper has high rigidity and hardness,
When storing soft fruits (such as pears and peaches),
There were drawbacks such as scratches and dents on the surface of the fruit, leading to a decrease in product value and a decrease in product yield.

In order to improve the flexibility of polystyrene resin,
Many attempts have been made to modify with rubber. For example, JP-A-53-8293 describes a method of obtaining a flexible sheet by extrusion-foaming a styrene-butadiene copolymer. However, in this publication, there is no description of what property the copolymer should have as a styrene-butadiene copolymer.

Therefore, the inventors of the present invention have widely used rubber-like polymer phase, in which small particles of styrene resin are scattered, and the average particle size of the rubber-like polymer particles having a salami structure is 1 to 2 μm. Regarding the rubber-modified styrene polymer resin of
An extrusion foaming test showed that the more extruded foamed sheets were obtained, the more incompletely foamed the film formed, the lower the closed cell ratio, the lower gas retention, and the lower the secondary foamability. It became insufficient. In particular, when the foam is extruded and foamed at a high expansion ratio of 0.12 g / cm ³ or less, the retention of the foaming agent in the cells is low, and the secondary foaming power is poor due to the decrease of the foaming agent during storage, and the vacuum forming However, only an extruded foamed sheet having remarkably inferior secondary moldability was obtained, and the secondary molded product from the sheet had remarkably low cushioning property.

Further, Japanese Patent Publication No. 1-60407 discloses that
Rubber component (butadiene rubber, ethylene-propylene rubber, styrene-butadiene rubber) is added to polystyrene resin
A method for continuously producing a foam-molded article of a rubber-modified polystyrene resin blended or copolymerized with 20 to 20% by weight is described, but the foam density is 0.15 to 0.7 in each case.
Low foaming of g / cm ³ and the thickness of the foam sheet is 0.3
Only very thin ones of ~ 1.0 mm are described.

[0006] Therefore, the present inventors have used the rubber-modified polystyrene resin described in the above publication to obtain a foaming density of 0.07 to
When an extrusion foaming test was performed to obtain a high foam of 0.12 g / cm ³ , the foamed sheet obtained had a low closed cell ratio, so the retention of the foaming agent was poor, and the secondary foaming power was low, resulting in secondary foaming. The resulting secondary molded product had poor buffering properties.

Further, in Japanese Patent Application Laid-Open No. 53-124574 and Japanese Patent Publication No. 4-49861, extrusion is carried out by using a polystyrene resin in which a styrene / butadiene block copolymer is mechanically mixed and dispersed by an extruder. A method of making a foamed sheet is described. However, when the present inventors tested this method using a tandem extruder composed of a single-screw single-stage extruder and a single-screw two-stage extruder, which is the mainstream of the industrial production method of expanded polystyrene sheet, the resin was The resulting foamed sheet has an incomplete formation of the foam film, and the foaming ratio and the closed cell ratio of the sheet are low, the foaming agent is reduced during storage, and the secondary foaming during secondary molding occurs. Secondary foaming became insufficient, and only a secondary molded product having poor impact resistance was obtained.

Further, in JP-A-6-228357, a rubber-modified polystyrene resin composition having a single occlusion structure in which 60% or more of the soft component particles have an average particle diameter of 0.6 μm or less, and the resin composition are used. Foams were described. The single occlusion structure is also called a core-shell structure, a capsule structure, etc., and is composed of a core portion that is a single continuous phase made of styrene resin and a rubbery polymer that encloses the core portion (occlude). It refers to a granular structure composed of shell parts. However, this rubber-modified polystyrene resin composition is one in which the resin composition after impregnating the volatile foaming agent is foamed by heating with steam to form a foam, and the resin composition after impregnating the volatile foaming agent is extruded as it is. It does not foam. And
Even if this resin composition is impregnated with a volatile foaming agent and extruded and foamed using general polystyrene, the formation of the foam film is incomplete, the closed cell ratio is low, and the foaming agent is reduced during storage. As a result, the secondary foaming property is lowered, so that a secondary molded article excellent in impact resistance cannot be obtained from the foamed sheet.

[0009]

DISCLOSURE OF THE INVENTION The present invention has good dispersibility without using a special mixing / dispersing means such as a twin-screw extruder, etc. An expanded foam sheet with a high closed cell rate and a small reduction of foaming agent gas during storage, and thus an excellent secondary foam moldability, is obtained. Secondary foam having higher impact resistance and flexibility than the expanded sheet. An object is to provide a rubber-modified styrene-based polymer resin composition for extrusion foaming in which a molded article can be easily obtained, to provide the resin extrusion foam sheet, and to provide a method for producing the resin extrusion foam sheet. To do.

[0010]

As a result of various studies to solve the above problems, the present inventors have found that a rubber having specific physical properties as a resin component used in the production of a resin composition for extrusion foaming. The purpose could be achieved by using the modified styrene polymer resin.

That is, the rubber-modified styrenic polymer resin composition for extrusion foaming of the present invention has rubber-like polymer particles dispersed in the continuous phase of the styrene-based polymer as a resin component. A rubber-modified styrene-based polymer resin in which the average particle diameter of the coalesced particles is 1.3 μm or less, the Z-average molecular weight of the styrene-based polymer is 450,000 or more, and the methanol-soluble content is 4% by weight or less. A composition characterized by being used.

The rubber-modified styrenic polymer composition of the present invention has, as a resin component, rubber-like polymer particles dispersed in a continuous phase of the styrene-based polymer. 100 parts by weight of a rubber-modified styrene-based polymer resin having a particle diameter of 1.3 μm or less, a Z-average molecular weight of the styrene-based polymer of 450,000 or more, and a methanol-soluble content of 4% by weight or less; A composition comprising a mixture of 5 to 25 parts by weight of at least one resin selected from a styrene / butadiene block copolymer and a hydrogenated product thereof.

The rubber-modified styrenic polymer resin extruded foamed sheet of the present invention has rubber-like polymer particles dispersed as a resin component in the continuous phase of the styrene-based polymer. Using a rubber-modified styrene-based polymer resin having an average particle size of 1.3 μm or less, a Z-average molecular weight of the styrene-based polymer of 450,000 or more, and a methanol-soluble content of 4% by weight or less, A density of 0.05 to 0.2 g / c obtained by extruding a rubber-modified styrene-based polymer resin composition to which a volatile foaming agent is added as a foaming agent.
It is an extruded foam sheet having a closed cell ratio of 70% or more at m ³ .

The rubber-modified styrenic polymer resin extruded foam sheet of the present invention has rubber-like polymer particles dispersed as a resin component in the continuous phase of the styrene-based polymer. Having a mean particle size of 1.3 μm or less, a Z-average molecular weight of the styrene-based polymer of 450,000 or more, and a methanol-soluble content of 4% by weight or less, 100 parts by weight of a rubber-modified styrene-based polymer resin And styrene
Rubber-modified styrene polymer resin composition using a mixture of 5 to 25 parts by weight of at least one resin selected from a butadiene block copolymer and its hydrogenated product, and adding a volatile foaming agent as a foaming agent Is an extruded foam sheet having a density of 0.05 to 0.2 g / cm ³ and a closed cell ratio of 70% or more.

The method for producing a rubber-modified styrenic polymer resin extruded foam sheet of the present invention is characterized in that rubber-like polymer particles are dispersed as a resin component in a continuous phase of a styrene-based polymer, Average particle size of polymer particles is 1.3 μm
And the Z-average molecular weight of the styrene-based polymer is 45 or less.
A rubber-modified styrene-based polymer resin composition containing a rubber-modified styrene-based polymer resin having a methanol-soluble content of 4% by weight or less and a volatile foaming agent added as a foaming agent The method is characterized in that extrusion foaming is carried out using a tandem extruder composed of a one-stage extruder and a single-screw two-stage extruder.

Further, in the method for producing a rubber-modified styrene polymer resin extruded foam sheet of the present invention, rubber-like polymer particles are dispersed as a resin component in a continuous phase of the styrene polymer. Average particle size of polymer particles is 1.3 μm
And the Z-average molecular weight of the styrene-based polymer is 45 or less.
100 parts by weight of a rubber-modified styrene polymer resin having a methanol-soluble content of 4% by weight or less, and at least one resin selected from a styrene / butadiene block copolymer and a hydrogenated product thereof. A rubber-modified styrene-based polymer resin composition containing a mixture of 5 to 25 parts by weight and a volatile foaming agent as a foaming agent is tandem extruded from a single-screw single-stage extruder and a single-screw two-stage extruder. It is a method of extrusion foaming using a machine.

The average particle size of the rubber-like polymer particles dispersed in the rubber-modified styrene-based polymer resin described in the present specification is the transmission electron micrograph of an ultrathin section of the rubber-modified styrene-based polymer resin. Is a value calculated by measuring the particle size of 500 dispersed rubber particles and using the following formula. When the rubber particles are oriented, the average value of the short diameter and the long diameter is defined as the particle diameter.

Average particle diameter = Σ ni Di ² / Σ ni Di In the formula, ni is the number of particles having the particle diameter Di.

The Z-average molecular weight of the styrene-based polymer of the rubber-modified styrene-based polymer resin described in the present specification is determined by filtering the rubber-modified styrene-based polymer resin dissolved in chloroform to remove the gel component. The measured values are those measured by gel permeation chromatography under the following conditions.

Device: S manufactured by Tosoh Corporation
C-8020 type GPC column: GPC AC manufactured by Showa Denko KK
-80M Mobile phase: Chloroform Sample concentration: 0.25% by weight Measurement temperature: 40 ° C Detector: UV-visible detector

The methanol-soluble content of the rubber-modified styrenic polymer resin described in the present specification is obtained by dissolving 1 g of the rubber-modified styrenic polymer resin in 10 ml of methyl ethyl ketone at room temperature and adding 300 ml of methanol. When the solid content obtained by reprecipitation and filtration was dried and weighed, the weight ratio of the amount of the resin composition component lost by dissolution in methanol during this operation to the amount of the resin used initially ( (% By weight) to obtain a methanol-soluble component.

The rubber-like polymer particles used in the present invention have an average particle size of 1.3 μm or less, and Z of the styrene-based polymer is used.
The rubber-modified styrene polymer resin having an average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less can be produced by various methods. For example, in the presence of a rubber-like polymer such as polybutadiene rubber, polyisoprene rubber, styrene-butadiene copolymer rubber,
It can be produced by polymerizing styrene-based monomers such as styrene, α-methylstyrene and p-methylstyrene. It can also be produced by copolymerizing the styrene-based monomer and the (meth) acrylic acid ester monomer in the coexistence of the rubber-like polymer. The rubber-modified styrene-based polymer resin obtained by these methods is obtained as a resin in which particles of the rubber-like polymer are dispersed in a styrene-based polymer resin matrix.

The rubber-modified styrenic polymer resin used in the present invention obtained by these methods is a rubber-like polymer particle in which small particles of the styrene polymer are encapsulated in a core-shell structure. May be dispersed in the continuous phase, or rubber-like polymer particles in which small particles of the styrene-based polymer are scattered in a salami structure inside the continuous phase of the styrene-based polymer. It may be dispersed.

The rubber-modified styrenic polymer resin used in the present invention has an average particle size of the rubber-like polymer particles of 1.3 μm or less, preferably 0.6 μm or less, more preferably 0.4 μm or less. . If the average particle diameter of the rubber-like polymer particles is too large, the formation of a cell membrane during extrusion foaming will be incomplete, and the closed cell rate of the foam will be reduced, and therefore the extruded foam will be inferior in impact absorption. In addition, the secondary foaming power is low, and the cushioning property (shock absorbing property) is deteriorated due to the insufficient thickness of the secondary foamed molded product.

In the above-mentioned method for producing the rubber-modified styrenic polymer resin used in the present invention, in order to control the particle size of the dispersed rubber-like polymer, the shape of the stirring device in the polymerization tank, the number of revolutions of the stirrer and the stirring time are used. It can be carried out by controlling various factors such as the polymerization temperature and cannot be uniquely determined. However, in general, it is possible to reduce the particle diameter by stirring the rubber during polymerization under such conditions that stress is applied to the rubber, for example, by increasing the rotation speed.

The rubber-modified styrenic polymer resin used in the present invention preferably has a rubber component content of 5 to 15.
%, More preferably 5 to 12% by weight. If the amount of the rubber component is too small, the extruded foam and the secondary foam molded article will be inferior in flexibility and impact absorbability, and if the amount of the rubber component is too large, formation of a foam film during extrusion foaming will be unsuccessful. When the secondary foaming is completed, the closed cell rate is reduced, the cells are destroyed during the secondary foam molding, and the moldability is deteriorated.

The rubber-modified styrene polymer resin used in the present invention has a Z-average molecular weight of 45 of the styrene polymer.
It is 10,000 or more, preferably 500,000 or more. If the Z-average molecular weight is too small, even if the rubber-like polymer particles have an average particle size of 1.3 μm or less, the formation of a bubble film during extrusion foaming will be incomplete and the closed cell ratio will decrease, resulting in storage The secondary foamability of the extruded foam decreases due to the escape of the foaming agent, and the impact absorbency of the secondary foam molded article also deteriorates. The reason for this is not clear, but the larger the Z-average molecular weight, the higher the melt viscosity of the matrix phase, and the easier it is to stabilize the cell membrane, and the rubber particle morphology of ultra-thin cut pieces of the cell membrane by a transmission electron micrograph. According to the observation, the rubber particles in the styrene-based polymer resin are oriented in the stretching direction of the foam film as the cells expand during foaming, but the rubber particles are sandwiched in the matrix phase in the styrene-based polymer having a larger Z-average molecular weight. The styrene-based polymer having a larger Z-average molecular weight has more stable rubber particles within a very thin bubble film thickness of 2 to 3 μm, because the orientation tendency becomes stronger and therefore the rubber particles have the same diameter. It is thought that this is due to the fact that it will be able to exist.

The orientation tendency of the rubber particles in the above case is more pronounced in the case of the rubber-modified styrene-based polymer resin having a salami structure in which small particles of the styrene-based resin are scattered in the rubber-like polymer phase. Since it is possible to stably exist even a large particle size in the continuous phase of the styrene-based polymer, in the case where the particle size before orientation is the same,
A salami structure is preferable to a core shell structure.

The means for increasing the Z-average molecular weight of the styrene-based polymer of the rubber-modified styrene-based polymer resin used in the present invention is to lower the polymerization temperature or to reduce the addition amount of the radical polymerization initiator. Alternatively, the Z-average molecular weight can be increased by reducing the addition amount of a mercaptan such as lauryl mercaptan or a chain transfer agent such as α-methylstyrene dimer.

The rubber-modified styrene polymer resin used in the present invention has a methanol-soluble content of 4% by weight or less, preferably 2% by weight or less. If the amount of the methanol-soluble component is too large, the melt tension during extrusion foam molding becomes insufficient, and molding into a sheet becomes difficult.

As means for reducing the methanol-soluble content of the rubber-modified styrenic polymer resin, a fluidity improver such as white oil, liquid paraffin, or polyethylene wax added to improve fluidity at the time of extrusion during polymerization. And a means for sufficiently removing the unreacted monomer and the polymerization solvent after the polymerization under reduced pressure.

The resin component in the rubber-modified styrene-based polymer resin composition for extrusion foaming of the present invention may be only the above-mentioned specific rubber-modified styrene-based polymer resin. For 100 parts by weight,
When at least one resin selected from the styrene / butadiene block copolymer and its hydrogenated product is used in an amount of 5 to 25 parts by weight, preferably 5 to 15 parts by weight, good bubble formation during extrusion foaming is achieved. It is possible to improve the flexibility of the extruded foam or the secondary foam-molded article while maintaining the property. However, if the combined amount is too large, the closed cell rate of the extruded foam decreases, the foaming agent retention performance deteriorates, and the secondary foam moldability of the extruded foam deteriorates.

In addition to the above resin components, a foaming agent is added to the rubber-modified styrene polymer resin composition for extrusion foaming of the present invention. Particularly, in the case of a composition for producing an extruded foam sheet having excellent secondary moldability, a volatile foaming agent such as propane, n-butane, i-butane, n-pentane,
A volatile hydrocarbon blowing agent such as i-pentane is added.
These volatile foaming agents may be used alone or in combination of two or more.

Various additives can be added to the rubber-modified styrene polymer resin composition for extrusion foaming of the present invention.

For example, a cell nucleating agent can be added for the purpose of uniformly adjusting the cell diameter of the extruded foam.
Examples of the cell nucleating agent include talc, magnesium carbonate, perlite, calcium silicate, calcium carbonate,
Examples thereof include silicon oxide and vermiculite.

In addition, as a dispersion aid, a higher fatty acid having 12 to 22 carbon atoms, for example, a metal salt of capric acid, stearic acid, palmitic acid or the like (for example, Ca or N) is added to the bubble nucleating agent.
a, Li, Zn, Al, Mg and the like) can be used together.

Further, an antistatic agent, a flame retardant, carbon black, various pigments and the like can be added.

The method of adding the additives such as the bubble nucleating agent is as follows.
It may be a dry blend, or may be added by using a masterbatch which is kneaded with a rubber-modified styrene polymer resin or the like in advance.

The rubber-modified styrene-based polymer resin foam sheet of the present invention is obtained by extruding the rubber-modified styrene-based polymer resin composition for extrusion and foaming of the present invention into a sheet-like shape to obtain a density of 0. 05~0.2g / cm ^3, but is obtained by the 70% closed cell ratio, extruded foam rubber-modified styrene polymer resin composition of the present invention is excellent in dispersibility, and readily uniform dispersion Therefore, it is possible to sufficiently disperse using a twin-screw extruder, or to disperse in a resin in advance, that is, without using a special mixing means such as a so-called "masterbatch method", that is, Complete formation of the cell membrane is easy and foaming is easy even by using a tandem extruder consisting of a single-screw single-stage extruder and a single-screw two-stage extruder, which has been used in the conventional industrial production of expanded polystyrene sheets. Double And high (i.e. Density 0.05
～0.2G / in cm ^3), and closed cell ratio is can be a rubber-modified styrene polymer resin foam sheet of 70% or more.

[0040]

[Examples] Hereinafter, examples and comparative examples will be described in detail. The density, closed cell ratio, flexibility, loss on heating, amount of foaming agent added, foaming agent retention performance, surface hardness, foam film formation and rubber component amount (polybutadiene conversion rubber component amount) described in these examples are as follows. Is.

Density The volume (Vcm ³ ) of a foam whose weight (Wg) is known is measured by the water immersion method, and the weight is divided by the volume to obtain the density (g
/ Cm ³ ).

Closed Cell Rate The true volume of a foam having a known density (g / cm ³ ) of about 25 cm ³ was measured using a Toshiba Beckman Co. air-comparison hydrometer 930, and the closed cell rate was calculated by the following formula. Calculate (S,%) S = {Vx−W / ρ} ÷ {Va−W / ρ} × 100
(%) In the formula, Vx: true foam volume (c
m ³ ) Va: Volume of foam (weight / density) (cm ³ ) W: Weight of foam (g) ρ: Density of base resin of foam (g / cm ³ )

Flexibility Using a mold composed of a convex mold and a concave mold shown in FIG. 1, a hemispherical ball-shaped fruit container is vacuum-formed from a resin extruded foam sheet, and the obtained molding container is JIS-K7220. A compression stress of 20% strain at a compression rate of 10 mm / min was obtained by a similar method and evaluated according to the following criteria. ○ 4.0 kg or less △ 4.1 to 5.9 kg × 6.0 kg or more

The heating loss weight determined known weight after foam heated for 4 hours at 120 ° C. of _{(W 1 g) (W 2} g), heating loss from the following formula (V,
%) Is calculated. V = {(W ₁ −W ₂ ) / W ₁ } × 100 (%)

Amount of foaming agent added Amount of foaming agent obtained by dividing the amount of foaming agent added during extrusion molding (B Kg / Hr) by the total amount of the composition discharged from the extruder (Q Kg / Hr). (E%). E = (B / Q) × 100 (%)

Foaming agent retention performance The above-mentioned heat loss of the foamed sheet stored as a sheet in a thermostatic chamber at 23 ° C. is half the amount of the foaming agent added during extrusion molding.
Calculate the number of days that has become the half-life. From the half-life, the foaming agent retention performance was evaluated according to the following criteria. ○ Half-life is 15 days or more △ Half-life is 5 to 14 days × Half-life is 4 days or less

Surface hardness Using a C-type hardness meter {SRIS (Japan Rubber Association Standard) 0101} manufactured by Kobunshi Keiki Co., Ltd., the hardness of the bottom surface of the fruit container molded with the mold shown in FIG. 1 was measured, and the average thereof was measured. The value was used to evaluate the surface hardness according to the following criteria. ○ 45 or less △ 46 to 59 × 60 or more

Bubble Film Formation An optical microscope photograph (magnification 25 times) was taken from a section of the cross section in the thickness direction of the foam sheet, and the photograph was visually inspected to evaluate the quality of the bubble film formation based on the following criteria. ○ Almost no air bubbles are broken △ Some of the air bubbles are open cells × Most of the air bubbles are open cells

Rubber Component Amount (Polybutadiene Equivalent Rubber Component Amount) The rubber component amount of the rubber-modified styrene-based polymer resin (polybutadiene equivalent rubber component amount) is converted into a polybutadiene amount by quantifying double bonds by the iodine monochloride method. According to the following method. Solution A: 18 g of iodine monochloride is dissolved in 1000 ml of carbon tetrachloride. Solution B: Potassium iodide 10 g, water 800 ml, ethanol 2
Dissolve in 00 ml of mixture. Solution C: Dissolve 10 g of sodium thiosulfate in 1000 ml of water, and standardize by standard method to determine the molar concentration.

About 0.4 g of the sample was precisely weighed in a 100 ml volumetric flask (Wg), 75 ml of chloroform was added to disperse well, 20 ml of solution A was added, and the mixture was stored in a cool dark place. Align with the line. 25m
Sample 1 is taken, 60 ml of solution B is added and titrated with solution C (molar concentration X) (main test Aml, blank test Bml). The rubber component amount (polybutadiene equivalent rubber component amount) is calculated by the following formula. Amount of rubber component (% by weight) = [{10.8 × X × (B-
A)} / W] × 100

(Example 1) A core-shell structure in which polystyrene is dispersed in the form of small particles inside, the butadiene component in the whole is 8% by weight, and the average particle diameter of the rubber particles is 0.2 μm. A rubber-modified polystyrene resin having a Z-average molecular weight of 55,000 and a methanol-soluble content of 1.6 wt% was used.

That is, with respect to 100 parts by weight of this rubber-modified polystyrene resin, 2 parts by weight of talc as a cell nucleating agent,
0.3 parts by weight of zinc stearate as a dispersion aid was added and well mixed with a mixer, and then a diameter of φ65 mm, L /
D is supplied to the hopper of a single-screw extruder of 33, melt-kneaded at 235 ° C. in the preceding stage of the extruder screw, and the melt-kneaded product has a total extrusion amount of 2. from a foaming agent injection hole provided in the middle stage of the extruder. A mixed butane containing 65% of n-butane and 35% of i-butane was added so as to be 5% by weight, then cooled to 160 ° C. in the latter stage of the extruder screw, and extruded into a tubular form through a die to obtain the obtained tubular form. After cooling the foamed sheet with a mandrel, one side was cut open with a cutter to obtain a foamed sheet.

The foamed sheet thus obtained had a wall thickness of 2 mm and a density of 0.09 g / cm ³ , and as shown in Table 1, the formation of a cell membrane was good, the closed cell rate was high, and the foaming agent retention performance was excellent. The surface hardness of the secondary molded product was low and the flexibility was excellent.

(Example 2) 100 parts by weight of the same rubber-modified polystyrene resin as in Example 1 was added to a commercially available styrene-butadiene-styrene block copolymer (Calichemical TRKX 155P, trade name of Ciel Chemical Co., styrene content 40 parts by weight). %) Was used as a resin component, and otherwise the same as in Example 1 to produce a foamed sheet.

The foamed sheet obtained had a wall thickness of 1.8 mm,
The density is 0.10 g / cm ³ , and as shown in Table 1, the formation of a bubble film is good, the closed cell ratio is high, the foaming agent retention performance is excellent, the surface hardness of the secondary molded product is low, and the flexibility is high. Was excellent.

(Example 3) 100 parts by weight of the same rubber-modified polystyrene resin as in Example 1 was added to a commercially available styrene / butadiene / styrene block copolymer (trade name: Crayton D1116, trade name of Ciel Chemical Co., styrene content 21% by weight). Using a resin added with 10 parts by weight as a resin component,
And as an extruder, it has a diameter φ with a foaming agent injection hole in the middle.
A tandem extruder composed of a uniaxial single-stage extruder having a diameter of 65 mm and a uniaxial twin-stage extruder having a diameter of 90 mm was used. Otherwise, a foamed sheet was produced according to the method of Example 1.

The foamed sheet thus obtained had a wall thickness of 1.8 mm,
As shown in Table 1, the density was 0.10 g / cm ³ , the cell film formation was good, the closed cell ratio was high, the foaming agent retention performance was excellent, the surface hardness of the secondary molded product was low, and the flexibility was excellent. Was there.

Example 4 A core-shell type in which a butadiene-based polymer rubber in which polystyrene was encapsulated in the form of small particles was dispersed in the form of particles was used, and the amount of butadiene component relative to the whole was 9% by weight. The average particle size of the polymer rubber particles is 0.3 μm, and Z of polystyrene is
A foamed sheet was produced in the same manner as in Example 1 except that a rubber-modified polystyrene resin having an average molecular weight of 480,000 and a methanol-soluble content of 0.6% by weight was used.

The foamed sheet thus obtained had a wall thickness of 1.6 mm,
As shown in Table 1, the density is 0.11 g / cm ³ , the cell film formation is good, the closed cell ratio is high, the foaming agent retention performance is excellent, the surface hardness of the secondary molded product is low, and the flexibility is excellent. Was there.

(Example 5) As the extruder to be used, a tandem extruder composed of a twin-screw single-stage extruder having a foaming agent injection hole and a diameter of φ48 mm and a single-axis two-stage extruder having a diameter of φ90 mm was used. A foamed sheet was manufactured in the same manner as in Example 2 except for the above.

The foamed sheet obtained had a wall thickness of 2.0 mm,
The density is 0.09 g / cm ³ , and as shown in Table 1, the formation of a bubble film is good, the closed cell ratio is high, the foaming agent retention performance is excellent, the surface hardness of the secondary molded product is low, and the flexibility is excellent. Was there.

Example 6 A foamed sheet was produced in the same manner as in Example 1 except that a rubber-modified styrene polymer resin having a salami structure was used as the rubber form. As shown in Table 1, the obtained foamed sheet was slightly inferior in terms of bubble film formation and closed cell rate, but the secondary molded article had low surface hardness and excellent flexibility.

Table 1 shows the main points in each of the above Examples 1 to 6, that is, the resin components, the physical properties of the extruded foam sheet and the extruder used.

[0064]

[Table 1]

Note to Table 1: * 1 ... Ciel Chemical Company trade name Califlex TRK
X 155P, styrene / butadiene / styrene block copolymer, styrene content 40% by weight * 2 ... Ciel Chemical Company's trade name Clayton D 111
6, styrene-butadiene-styrene block copolymer, styrene content 21% by weight

(Comparative Example 1) As a resin component, a rubber-like polymer phase has a salami structure in which small particles of a styrene resin are scattered, and the amount of butadiene component in the whole is 7% by weight.
The average particle diameter is 2.7 μm, and the Z of the polystyrene is
Using a rubber-modified polystyrene resin having an average molecular weight of 450,000 and a methanol-soluble content of 2.1% by weight,
A foam sheet was manufactured in the same manner as in Example 1 except for the above.

The foamed sheet obtained had a wall thickness of 1.4 mm,
The density was 0.13 g / cm ³ , and as shown in Table 2, the formation of the bubble film was not sufficient, the closed cell ratio was low, and the foaming agent retention performance was poor.

(Comparative Example 2) A resin having a core-shell structure in which a butadiene-based polymer rubber containing polystyrene in the form of small particles is dispersed as a resin component, and the amount of the butadiene component in the whole is 8% by weight. A foamed sheet was used in the same manner as in Example 1 except that a rubber-modified polystyrene resin having a butadiene polymer rubber having an average particle diameter of 0.3 μm, a polystyrene Z-average molecular weight of 340,000, and a methanol-soluble content of 0% by weight was used. Was manufactured.

The foamed sheet thus obtained had a wall thickness of 1.2 mm,
The density was 0.15 g / cm ³ , and as shown in Table 2, the formation of a bubble film was extremely poor, the closed cell ratio was low, and the foaming agent retention performance was extremely poor.

(Comparative Example 3) The resin component had a core-shell structure in which butadiene-based polymer rubber in which polystyrene was encapsulated in the form of small particles was dispersed in the form of particles, and the butadiene component accounted for 8% by weight, butadiene Extruded in the same manner as in Example 1 except that a rubber-modified polystyrene resin having a polymer rubber having an average particle size of 0.2 μm, a polystyrene Z-average molecular weight of 350,000 and a methanol-soluble content of 4.7% by weight was used. Molded.

However, at the time of the extrusion molding, the resin could not be extruded and foamed into a tubular shape from the die, and the foamed sheet could not be manufactured.

Table 2 shows the main points in each of the above Comparative Examples 1 to 3, that is, the resin component, the physical properties of the extruded foam sheet and the extruder used.

[0073]

[Table 2]

Note to Table 2: * 1 ... It was not possible to evaluate because the sheet could not be extruded and foamed.

Comparative Example 4 A commercially available polystyrene resin (trade name: HRM5, manufactured by Denki Kagaku Co., Ltd.) was used as a resin component, and a foamed sheet was manufactured by the same method as in Example 1 except for the above.

The physical properties of the obtained foamed sheet and the like are as follows, and although the foamed film formation, the closed cell ratio and the foaming agent retention performance were excellent, the surface hardness and flexibility of the secondary molded product were extremely poor. It was

Foamed sheet thickness 2.0 mm Foamed sheet density 0.09 g / cm ³ Closed cell ratio of foamed sheet 93% Foamed film formation of foamed sheet ○ Foaming agent retention performance of foamed sheet ○ Surface hardness of secondary molded product × Secondary molded product flexibility ×

(Comparative Example 5) 100 parts by weight of the commercially available polystyrene resin used in Comparative Example 4 was further mixed with commercially available styrene.
A uniaxial single-stage extruder with a diameter of Φ65 mm having a foaming agent injection hole was used as a resin component, in which 10 parts by weight of a butadiene block copolymer (trade name: Crayton D1116, manufactured by Ciel Chemical Co., Ltd.) was used. φ9
A foamed sheet was produced in the same manner as in Comparative Example 1 except that a tandem extruder composed of a 0 mm uniaxial two-stage extruder was used.

The physical properties of the obtained foamed sheet and the like are as follows, and the foamed film formation, closed cell ratio, foaming agent retention performance, surface hardness and flexibility of the secondary molded product are all inferior. It was

Foamed sheet thickness 1.6 mm Foamed sheet density 0.11 g / cm ³ Closed cell ratio of foamed sheet 65% Foamed film formation of foamed sheet △ Foaming agent retention performance of foamed sheet × Surface hardness of secondary molded product △ Flexibility of secondary molded products △

[0081]

The rubber-modified styrenic polymer resin composition of the present invention can be easily extruded and foamed without using any special mixing means, and the obtained extruded foam sheet is excellent in forming a cell membrane and has a closed cell ratio. The secondary foamed molded product, which has a low surface hardness and is excellent in flexibility, which is more suitable for use as a fruit container than the extruded foamed sheet, is easily obtained because the foaming agent has a high content and a small amount of foaming agent decreases during storage.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a mold including a convex mold and a concave mold for vacuum forming a secondary foam molded product for a flexibility and surface hardness test from an extruded foam sheet. The numbers in the figure are numerical values (mm).

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[Procedure amendment]

[Submission date] April 11, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

About 0.4 g of the sample was precisely weighed in a 100 ml volumetric flask (Wg), 75 ml of chloroform was added to disperse well, 20 ml of solution A was added, and the mixture was stored in a cool and dark place. Align with the line. 25
Collect ml, add 60 ml of solution B, and titrate with solution C (molar concentration X) (main test A ml, blank test B ml). The rubber component amount (polybutadiene equivalent rubber component amount) is calculated by the following formula. Amount of rubber component (% by weight) = {10.8 × X × (BA)}
/ W

Claims (6)

[Claims] 1. As a resin component, rubber-like polymer particles are dispersed in a continuous phase of a styrene-based polymer, and the average particle diameter of the rubber-like polymer particles is 1.3 μm or less. A rubber-modified styrene-based polymer resin for extrusion foaming, characterized in that a rubber-modified styrene-based polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less is used. Composition. 2. A rubber-like polymer particle as a resin component is dispersed in a continuous phase of a styrene-based polymer, and the average particle diameter of the rubber-like polymer particle is 1.3 μm or less. From 100 parts by weight of a rubber-modified styrene polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less, a styrene / butadiene block copolymer and a hydrogenated product thereof. A rubber-modified styrene-based polymer resin composition for extrusion foaming, which comprises using a mixture with 5 to 25 parts by weight of at least one selected resin. 3. A rubber-like polymer particle as a resin component is dispersed in a continuous phase of a styrene-based polymer, and the average particle diameter of the rubber-like polymer particle is 1.3 μm or less. A rubber-modified styrene-based polymer obtained by using a rubber-modified styrene-based polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less and adding a volatile foaming agent as a foaming agent. A rubber-modified styrene-based polymer resin extruded foam sheet having a density of 0.05 to 0.2 g / cm ³ and a closed cell ratio of 70% or more, which is obtained by extruding and foaming a polymer resin composition. 4. As a resin component, rubbery polymer particles are dispersed in a continuous phase of a styrene polymer, and the rubbery polymer particles have an average particle diameter of 1.3 μm or less. From 100 parts by weight of a rubber-modified styrene polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less, a styrene / butadiene block copolymer and a hydrogenated product thereof. A density of 0.0 obtained by extrusion-foaming a rubber-modified styrene-based polymer resin composition using a mixture with 5 to 25 parts by weight of at least one selected resin and adding a volatile foaming agent as a foaming agent.
A rubber-modified styrene polymer resin extruded foam sheet having a closed cell ratio of 70% or more at 5 to 0.2 g / cm ³ . 5. A rubber-like polymer particle as a resin component is dispersed in a continuous phase of a styrene-based polymer, and the average particle diameter of the rubber-like polymer particle is 1.3 μm or less. A rubber-modified styrene-based polymer obtained by using a rubber-modified styrene-based polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less and adding a volatile foaming agent as a foaming agent. A process for producing a rubber-modified styrene-based polymer resin extruded foamed sheet, which comprises extruding and foaming a polymer resin composition using a tandem extruder composed of a single-screw single-stage extruder and a single-screw two-stage extruder. 6. A resin component comprising rubber-like polymer particles dispersed in a continuous phase of a styrene-based polymer, wherein the rubber-like polymer particles have an average particle diameter of 1.3 μm or less. From 100 parts by weight of a rubber-modified styrene polymer resin having a Z-average molecular weight of 450,000 or more and a methanol-soluble content of 4% by weight or less, a styrene / butadiene block copolymer and a hydrogenated product thereof. A rubber-modified styrene-based polymer resin composition prepared by using a mixture with 5 to 25 parts by weight of at least one selected resin and adding a volatile foaming agent as a foaming agent is used as a single-screw single-stage extruder and a single-screw two-stage extrusion machine. A method for producing a rubber-modified styrenic polymer resin extruded foam sheet, which comprises extruding and foaming using a tandem extruder composed of a machine.