JP2943055B2 - Extruded foam sheet of rubber-modified styrene polymer resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an extruded foamed sheet of a rubber-modified styrenic polymer resin. More specifically, the present invention relates to a resin-extruded foamed sheet obtained by extruding and foaming a rubber-modified styrenic polymer resin having excellent flexibility and shock absorption.

[0002]

2. Description of the Related Art Polystyrene resin foams are excellent in molding processability, surface gloss, light weight, heat insulation, etc., and those having a thickness of 3 mm or less are called "polystyrene paper", Widely used for containers such as lunch boxes, bowls and trays. However, packaging containers using conventional polystyrene paper have high rigidity and are hard,
When storing soft fruits (for example, pears and peaches)
Scratches, dents, and the like are produced on the fruit surface, which has the disadvantage of lowering the commercial value and lowering the product yield.

[0003] 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, there is no description in the gazette as to what type of copolymer having properties should be used as the styrene-butadiene copolymer.

Therefore, the present inventors have found that the rubbery polymer particles having a salami structure, in which small particles of a styrene resin are scattered in a rubbery polymer phase, are generally widely used, have an average particle diameter of 1 to 2 μm. About the rubber-modified styrenic polymer resin of
As a result of the extrusion foaming test, the extruded foamed sheet obtained shows that as the foam is extruded and foamed at a higher magnification, the formation of the cell membrane becomes incomplete, the closed cell ratio becomes lower, the gas retention is reduced, and the secondary foaming property is reduced. It became inadequate. In particular, when extrusion foaming is performed at a high magnification of a foam density of 0.12 g / cm ³ or less, the foam has a low foaming agent retention property, a low foaming agent during storage, a poor secondary foaming power, and vacuum forming. Only an extruded foamed sheet having remarkably inferior secondary moldability was obtained, and a secondary molded article from the sheet had extremely low buffering properties.

Further, Japanese Patent Publication No. 1-60407 discloses that
No rubber component (butadiene rubber, ethylene-propylene rubber, styrene-butadiene rubber) is added to polystyrene resin.
A method for continuously producing a foamed molded article of a rubber-modified polystyrene resin blended or copolymerized with a foam density of 0.15 to 0.7% is described.
g / cm ³ low foaming, and the thickness of the foamed sheet is 0.3
Only extremely thin ones of １．０1.0 mm are described.

[0006] The inventors of the present invention used a rubber-modified polystyrene resin described in the same publication to produce a foam having a foam density of 0.07 to 0.07.
When an extrusion foaming test was performed to obtain a high foam of 0.12 g / cm ³ , the obtained foamed sheet had a low closed cell rate, so the holding property of the foaming agent was poor, the secondary foaming power was low, and the secondary foaming was performed. The resulting molded article had poor cushioning properties.

[0007] JP-A-53-124574 and JP-B-4-49861 disclose an extrusion method using a material obtained by mechanically mixing and dispersing a styrene-butadiene block copolymer in a polystyrene resin using an extruder. A method for making a foam sheet is described. However, the present inventors have 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 an industrial production method for an expanded polystyrene sheet. In other words, the uniform dispersion of the foam cannot be obtained, and the formed foam sheet has incomplete formation of a foam film, and the sheet has a low foaming ratio and a low independent foaming rate. Secondary foaming was insufficient, and only a secondary molded article having poor impact resistance was obtained.

Japanese Patent Application Laid-Open No. 6-228357 discloses a rubber-modified polystyrene resin composition having a single occlusion structure in which 60% or more of soft component particles have an average particle diameter of 0.6 μm or less. Foams are described. The single occlusion structure is also referred to as a core-shell structure, a capsule structure, or the like, and is composed of a nucleus portion that is a single continuous phase made of a styrene-based resin and a rubber-like polymer that includes the nucleus portion (occlude). It refers to a particulate structure composed of shell parts.
However, this rubber-modified polystyrene resin composition is obtained by foaming the resin composition impregnated with a volatile foaming agent by steam heating to form a foam, and extruding the resin composition impregnated with the volatile foaming agent 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 a general polystyrene, the formation of the foam film is incomplete, the closed cell rate is low, and the foaming agent is stored during storage. Since the secondary foaming property decreases due to the decrease, a secondary molded article excellent in impact resistance cannot be obtained from the foamed sheet.

[0009]

The present invention provides good dispersibility without using a special mixing and dispersing means such as a twin-screw extruder and the like, and provides good foam film formation by ordinary extrusion foaming. It is an object of the present invention to provide an extruded foam sheet having a high closed cell ratio, a small decrease in a foaming agent gas during storage, and therefore having excellent secondary foam moldability.

[0010]

The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, as a resin composition for extrusion foaming, a rubber-modified styrene polymer resin having specific physical properties has been obtained. By using a resin consisting of a styrene-based polymer resin having a specific Z-average molecular weight, the object was achieved.

The extruded rubber-modified styrene polymer resin foam sheet of the present invention comprises (A) a rubbery polymer particle dispersed in a continuous phase of a styrene polymer as a resin component, The average particle diameter of the particles is 3 μm or less, the Z-average molecular weight of the styrene-based polymer is 330,000 or more,
And using a rubber-modified styrene polymer resin of methanol-soluble fraction is 4% by weight or less, (B) a resin which Z average molecular weight is from 700,000 more styrene-based polymer resin, (C)
It is an extruded foamed sheet formed by extruding and foaming a rubber-modified styrenic polymer resin composition to which a volatile foaming agent is added as a foaming agent.

The rubber-modified styrenic polymer resin extruded foam sheet of the present invention comprises, as a resin component, (A) a rubbery polymer particle dispersed in a continuous phase of a styrenic polymer. A rubber-modified styrene-based polymer resin having an average particle diameter of 3 μm or less and a methanol-soluble content of 4% by weight or less, and (B) a Z-average molecular weight of 70
Resin component 100 composed of 10,000 or more styrene-based polymer resins
With (D) a resin comprising at least one resin 5 to 25 parts by weight selected from styrene-butadiene block copolymer and a hydrogenated product thereof with respect to the weight part, volatile as (C) and blowing agent It is an extruded foamed sheet formed by extruding and foaming a rubber-modified styrenic polymer resin composition to which a foaming agent has been added. The rubber-modified styrenic polymer tree of the present invention
The extruded fat foam sheet has a density of 0.05 g / cm ³ and is independent
It is preferable that the bubble rate is 70% or more.

The rubber-modified styrene-based polymer resin extruded foam sheet of the present invention has rubber-like polymer particles dispersed in a continuous phase of a styrene-based polymer as a resin component. Using a rubber-modified styrene-based polymer resin having an average 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 foamed sheet obtained by extrusion-foaming a rubber-modified styrenic polymer resin composition to which a volatile foaming agent is added as a foaming agent using a tandem extruder composed of a single-screw single-stage extruder and a single-screw two-stage extruder < br />.

Further, the extruded rubber-modified styrene polymer resin foam sheet of the present invention has rubber-like polymer particles dispersed in a continuous phase of a styrene-based polymer as a resin component. Is not more than 1.3 μm, 100 parts by weight of 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 in the styrene-based polymer. 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 a hydrogenated product thereof, and adding a volatile foaming agent as a foaming agent Is a foam sheet extruded and foamed using a tandem extruder composed of a single-screw single-stage extruder and a single-screw two-stage extruder.

The average particle size of the rubber-like polymer particles dispersed in the rubber-modified styrene-based polymer resin described in this specification is defined as a transmission electron micrograph of an ultrathin section of the rubber-modified styrene-based polymer resin. Is the value obtained by measuring the particle diameter of 500 dispersed rubber particles and calculating by the following equation. In the case where the rubber particles are oriented, the average value of the minor axis and the major axis is defined as the particle diameter.

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

Further, the Z-average molecular weight of the styrene-based polymer of the rubber-modified styrene-based polymer resin or the Z-average molecular weight of the styrene-based polymer resin described in the present specification refers to the rubber-modified styrene-based polymer resin or It is a value measured by gel permeation chromatography under the following conditions for a gel obtained by dissolving a styrene polymer resin in chloroform and removing the gel component by filtration.

[0018]

The methanol-soluble portion of the rubber-modified styrene-based polymer resin described in this specification is obtained by dissolving 1 g of the rubber-modified styrene-based polymer resin in 10 ml of methyl ethyl ketone at room temperature, and adding 300 ml of methanol. When the solid content obtained by re-precipitation and filtration is dried and weighed, the amount of the resin composition component dissolved and lost in methanol during this operation is based on the amount of the initially used resin. The weight ratio (% by weight) is defined as methanol-soluble matter.

The component (A) used in the present invention, that is, the rubber-like polymer particles have an average particle size of 3 μm or less, the styrene-based polymer has a Z-average molecular weight of 330,000 or more and a methanol-soluble content of 4 The rubber-modified styrenic polymer resin of not more than weight% can be produced by various methods.
For example, polybutadiene rubber, polyisoprene rubber,
It can be produced by polymerizing a styrene-based monomer such as styrene, α-methylstyrene and p-methylstyrene in the presence of a rubber-like polymer such as styrene-butadiene copolymer rubber. Further, it can also be produced by copolymerizing the styrene-based monomer and the (meth) acrylate monomer in the presence of the rubber-like polymer. The rubber-modified styrenic polymer resins obtained by these methods are all obtained as resins in which rubbery polymer particles are dispersed in a styrenic 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 a styrenic polymer are encapsulated in a core-shell structure. May be dispersed in the continuous phase of the styrene-based polymer, or rubber-like polymer particles in which small particles of the styrene-based polymer are scattered in a salami structure are dispersed in the continuous phase of the styrene-based polymer. You may be doing.

The rubber-modified styrenic polymer resin used in the present invention has an average particle size of its rubbery polymer particles of 3 μm or less, preferably 2 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 becomes incomplete, the closed cell ratio of the foam decreases, and therefore the extruded foam has poor shock absorbing properties. At the same time, the secondary foaming power is low, and the cushioning property (impact absorption) also deteriorates due to insufficient thickness of the secondary foam molded article.

The rubber-modified styrenic polymer resin used in the present invention has a Z-average molecular weight of 33
It is at least 10,000, preferably at least 350,000. When the Z-average molecular weight decreases, the average particle diameter of the rubber-like polymer particles becomes 3 μm.
Even if it is less than m, formation of a cell membrane at the time of extrusion foaming will be incomplete, the closed cell ratio of the foam will be reduced, and the shock absorption will be poor. The reason is not always clear, but Z
The higher the average molecular weight, the higher the melt viscosity of the matrix phase and the more easily the foam film is stabilized. Along with the rubber particles in the styrene-based polymer resin are also oriented in the stretching direction of the cell membrane, but since the styrene-based polymer having a larger Z-average molecular weight is more likely to have the rubber particles sandwiched in the matrix phase, the orientation tendency becomes stronger. Therefore, for the same rubber particle diameter,
A styrene-based polymer having a larger Z-average molecular weight has
It is considered that the rubber particles can be more stably present in the thickness of the extremely thin bubble film of m.

The orientation tendency of the rubber particles in the above case is more remarkable in the case of the rubber-modified styrene-based polymer having a salami structure in which small particles of the styrene-based polymer are scattered in the rubber-like polymer phase. It is possible to stably exist those having a large particle diameter in the continuous phase of the styrene-based polymer. Are preferred,
Further, in the case of the salami structure, a so-called high cis butadiene rubber in which the ratio of the 1,4-cis structure of the contained butadiene rubber is 70% or more is more preferable.

The rubber-modified styrenic 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 methanol-soluble component is too large, the melt tension of the resin during extrusion foam molding becomes insufficient, and it becomes difficult to form a sheet.

Means for reducing the methanol-soluble content of the rubber-modified styrenic polymer resin include, for example, white oil, liquid paraffin, polyethylene wax, etc., which are added to improve the fluidity during extrusion during polymerization. Means include reducing the amount of the modifier added, and removing unreacted monomers and polymerization solvent after polymerization sufficiently under reduced pressure.

The content of the rubbery polymer in the rubber-modified styrenic polymer resin used in the present invention is usually 2 to 15% by weight, preferably 4 to 10% by weight. If the content of the rubbery polymer is too small, the flexibility and the buffering property will be impaired. On the other hand, if the content of the rubber-like polymer is too large, the formation of the cell membrane becomes incomplete, the closed cell rate is reduced, the retention of the cell foaming agent is reduced, and the amount of the foaming agent during storage is reduced. In addition, only an extruded foam sheet having poor secondary foaming power and extremely poor secondary moldability such as vacuum molding can be obtained.

Next, the component (B) used in the present invention, ie, a styrene-based polymer resin having a Z-average molecular weight of 700,000 or more, is a styrene-based monomer, ie, styrene, α-methylstyrene, p-methylstyrene, or the like. It is produced by polymerizing one or more of the above. The styrene polymer resin has a Z-average molecular weight of 700,000 or more, preferably 850,000 or more. If the Z-average molecular weight of the styrenic polymer resin is too small, the formation of a cell membrane at the time of extrusion foaming will be incomplete, and the closed cell ratio will decrease.

Means for controlling the Z-average molecular weight of the styrenic polymer resin include polymerization temperature, the amount of a radical polymerization initiator added, mercaptans such as lauryl mercaptan, and chain transfer agents such as α-methylstyrene dimer. Means for adjusting or changing the amount of addition of phenol.

The rubber-modified styrene polymer resin (A) and the styrene polymer resin (B) used in the present invention are used.
Is preferably 5 to 100 parts by weight with respect to 100 parts by weight of the former. If the compounding ratio of the latter is too small, the formation of a cell membrane at the time of extrusion foaming becomes incomplete, and the closed cell ratio is reduced. On the other hand, if the latter compounding ratio is too large, the flexibility and the impactability of the ribbon are impaired.

The resin components in the rubber-modified styrene-based polymer resin composition for extrusion foaming used in the present invention include the rubber-modified styrene-based polymer resin (A) and the styrene-based polymer resin (B). The resin (A) and the resin (B) may have a total amount of 100
When 5 to 25 parts by weight of at least one resin selected from a styrene / butadiene block copolymer and a hydrogenated product thereof is blended with respect to parts by weight, while maintaining good foamability, the extruded foam sheet and The flexibility of the secondary molded product can be improved.

The amount of the rubbery polymer component based on the rubber-modified styrenic polymer resin (A) in all the resin components in the rubber-modified styrenic polymer resin composition for extrusion foaming used in the present invention is usually 5 to 5. 15% by weight, preferably 5-1
2% by weight. If the amount of the rubber polymer component is too small,
If the flexibility and impact absorption of the foam and the secondary molded product are deteriorated, and the rubber component content is too large, the formation of a foam film of the foam becomes incomplete, the closed cell ratio is reduced, and the secondary molding is performed. When the air bubbles are destroyed, the secondary workability decreases.

The rubber-modified styrenic polymer resin composition for extrusion foaming used in the present invention contains a foaming agent in addition to the above resin components. In particular, in the case of a resin composition for producing an extruded foam sheet having excellent secondary moldability, volatile foaming agents such as propane, n-butane, i-butane, and n-
Volatile hydrocarbon blowing agents such as pentane and i-pentane are added. One of these volatile foaming agents may be used, or two or more thereof may be used in combination.

Further, various additives can be added to the rubber-modified styrenic polymer resin composition for extrusion foaming used in 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, silicon oxide, vermiculite and the like.
In addition, the cell nucleating agent has 12 to 22 carbon atoms as a dispersing aid.
Metal salts of higher fatty acids such as capric acid, stearic acid and palmitic acid (eg, Ca, Na, Li, Z
n, Al, Mg, etc.). 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 may be dry blending, or may be added using a master batch kneaded with a resin in advance.

Next, the rubber-modified styrenic polymer resin foam sheet of the present invention is formed by extruding the above-mentioned rubber-modified styrenic polymer resin composition for extrusion foaming of the present invention into a sheet-like shape or the like 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, easy uniform dispersion It is possible to disperse using a twin-screw extruder, or disperse in advance in a resin component, without dispersing using a special mixing means such as a so-called “master batch method”, Even if only a tandem extruder composed of a single-screw single-stage extruder and a single-screw two-stage extruder is used, as is conventionally used in the industrial production of expanded polystyrene sheets, the formation of a foam film is easily completed, Foaming Rate be higher (i.e. Density 0.05
０．２0.2 g / cm ³ ) and a foamed rubber-modified styrene polymer resin sheet having a closed cell ratio of 70% or more.

[0036]

The present invention will be described in detail below with reference to examples and comparative examples. The density, closed cell rate, flexibility, loss on heating, amount of foaming agent added, foaming agent holding performance, surface hardness, cell formation, and rubber component amount (polybutadiene-equivalent rubber component amount) described in these examples are as follows. is there.

The volume (Vcm ³ ) of a foam having a known density weight (Wg) is measured by a submersion method, and the value obtained by dividing the weight by the volume is defined as the density (g / cm 3).

Closed cell ratio The true volume of about 25 cm ³ of a foam having a known density (g / cm ³ ) was measured using an air comparison type hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. (S,%) is calculated. S = {Vx−W / ρ} Va−W / ρ} × 100 (%) where Vx: volume of the true foam measured by the above-mentioned device (cm ³ ) Va: volume of the 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 formed container is subjected to JIS-K7220. The compressive stress of 20% strain at a compressing speed of 10 mm / min was determined by a method according to the standard, and evaluated according to the following criteria. ○ 4.0 kg or less △ 4.1 to 5.9 kg × 6.0 kg or more

Weight loss (W ₂ g) after heating a foam having a known weight (W ₁ g) at 120 ° C. for 4 hours was determined, and the weight loss (V,
%). V = {(W ₁ −W ₂ ) / W ₁ } × 100 (%)

Addition amount of foaming agent Addition amount of foaming agent is obtained by dividing the addition amount of foaming agent (B kg / Hr) at the time of extrusion molding by the total amount of composition discharged from the extruder (Q kg / Hr), and (E%). E = (B / Q) × 100 (%)

Foaming agent holding performance The heating loss of the foamed sheet stored in a sheet in a constant temperature room at 23 ° C. is one half of the foaming agent addition amount during extrusion molding.
Obtain the number of days after which the half life is reached. From the half-life, the blowing 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 The hardness of the bottom surface of the fruit container molded with the mold shown in FIG. 1 was measured using a C-type hardness meter (SRIS (Japanese Rubber Association Standard) 0101) manufactured by Kobunshi Keiki Co., Ltd. The surface hardness was evaluated based on the values according to the following criteria. ○ 45 or less △ 46 to 59 × 60 or more

Bubble Formation An optical microscope photograph (magnification: 25 times) was taken from a section of a cross section in the thickness direction of the foam sheet, and the photograph was visually inspected to evaluate the quality of bubble formation according to the following criteria. ○ Destruction of air bubbles is hardly observed △ Some air bubbles are open cells × Most air bubbles are open cells

Amount of rubber component (amount of rubber component in terms of polybutadiene) The amount of a rubber component (amount of rubber component in terms of polybutadiene) of the rubber-modified styrene-based polymer resin is converted into an amount of polybutadiene by quantifying double bonds by an iodine monochloride method. The following method was used. Solution A: Dissolve 18 g of iodine monochloride in 1000 ml of carbon tetrachloride. Liquid B: 10 g of potassium iodide, 800 ml of water, ethanol 2
Dissolve in 00 ml of the mixture. Solution C: 10 g of sodium thiosulfate is dissolved in 1000 ml of water, and the molarity is determined by standardization according to a conventional method.

About 0.4 g of the sample was precisely weighed (Wg) in a 100 ml volumetric flask, and well dispersed by adding 75 ml of chloroform. Then, 20 ml of solution A was added and stored in a cool and dark place. Align with the line. 25m
1) is collected, 60 ml of solution B is added, and titrated with solution C (molarity X) (Aml in the main test, Bml in the blank test). The rubber component amount (polybutadiene-converted rubber component amount) is calculated by the following equation. Rubber component amount (% by weight) = {10.8 × X × (BA)} / W

(Example 1) A butadiene-based polymer rubber in which polystyrene is encapsulated in small particles is dispersed in the form of particles, and the butadiene component accounts for 8% by weight of the whole polymer. A rubber-modified polystyrene resin having a polymer having a rubber average particle diameter of 0.2 μm, a polystyrene phase having a Z-average molecular weight of 55,000, and a methanol-soluble content of 1.6% by weight was used. That is, 100 parts by weight of this rubber-modified polystyrene was mixed with a polystyrene having a Z-average molecular weight of 970,000 (Denka Styrol HRM, trade name of Denki Kagaku Co., Ltd.).
-3), 10 parts by weight of talc, 2 parts by weight of talc as a cell nucleating agent, and 0.3% of zinc stearate as a dispersing aid.
Add the parts by weight and stir and mix well with a mixer.
5 mm, L / D is supplied to the hopper of a single screw extruder of 33, and melt-kneaded at 235 ° C. in front of the extruder screw;
In the melt-kneaded product, a mixed butane of 65% n-butane and 35% i-butane was continuously fed from a blowing agent injection hole provided in the middle stage of the extruder so as to be 2.5% by weight of the total extruded amount. The mixture was injected, cooled to 160 ° C. at the subsequent stage of the extruder screw, extruded and foamed into a tube from a die, cooled with a mandrel, and cut into one side of the tubular foam sheet with a cutter to obtain a foam sheet. The obtained foam sheet has a thickness of 1.8 mm,
The density was 0.10 g / cm ³ , and as shown in Table 1, the foam formation was good, the closed cell ratio was high, the foaming agent retention performance was excellent, the surface hardness was low, and the flexibility was excellent.

(Example 2) The amount of polystyrene having a Z-average molecular weight of 970,000 used in Example 1 was changed to 25 parts by weight, and the extruder had a diameter of 65 mm with a foaming agent injection hole in the middle of each shaft. An extruded foamed sheet was manufactured in the same manner as in Example 1 except that a tandem extruder composed of an extruder and a single-screw two-stage extruder having a diameter of 90 mm was used. The obtained foam sheet is
The thickness was 2.0 mm and the density was 0.09 g / cm ^3.
As shown in the above, good bubble formation, high closed cell rate,
Excellent foaming agent retention performance, low surface hardness, and excellent flexibility.

Example 3 The rubbery polymer phase has a salami structure in which small particles of polystyrene are scattered, and the average particle size of the rubbery polymer having the salami structure is 2.7 μm, which occupies the whole rubber-modified polystyrene. The butadiene component content is 7% by weight, and the polystyrene Z
A rubber-modified polystyrene resin having an average molecular weight of 45,000 and a methanol-soluble content of the rubber-modified polystyrene of 2.1% by weight was used. That is, 25 parts by weight of polystyrene having a Z-average molecular weight of 970,000 was added to 100 parts by weight of this rubber-modified polystyrene, and the other steps were the same as in Example 1 to produce a foamed sheet. The obtained foam sheet has a thickness of 1.8 mm, a density of 0.10 g / cm ³ ,
As shown in Table 1, the foam formation was good, the closed cell ratio was high, the foaming agent retention performance was excellent, the surface hardness was low, and the flexibility was excellent.

Example 4 Polybutadiene rubber having polystyrene encapsulated therein in the form of small particles is of a core-shell structure in which particles are dispersed. The butadiene component accounts for 8% by weight of the whole rubber-modified polystyrene. A rubber-modified polystyrene resin having a rubber average particle diameter of 0.3 μm, a Z-average molecular weight of polystyrene of 340,000, and a methanol-soluble content of 0% was used. That is, a foamed sheet was manufactured using this rubber-modified polystyrene and using the same method as in Example 1 except for the above. The obtained foamed sheet has a thickness of 1.6 mm, a density of 0.11 g / cm ³ , and has good foam formation, a high closed cell rate, excellent foaming agent holding performance, and excellent surface hardness as shown in Table 1. But low in flexibility.

Example 5 As an extruder, a diameter φ48 having a foaming agent injection hole in the middle was used.
A foamed sheet was manufactured in the same manner as in Example 1 except that a tandem extruder composed of a twin-screw single-stage extruder having a diameter of 90 mm and a single-screw two-stage extruder having a diameter of 90 mm was used. The obtained foam sheet has a thickness of 2.2 mm and a density of 0.08 g / cm.
³ , and as shown in Table 1, the foam formation was good, the closed cell ratio was high, the foaming agent retention performance was excellent, the surface hardness was low, and the flexibility was excellent.

Example 6 A commercially available styrene-butadiene-styrene block copolymer (Clayton D1116, trade name of Ciel Chemical) was added to 100 parts by weight of the rubber-modified polystyrene used in Example 2.
Was added, and 30 parts by weight of polystyrene having a Z-average molecular weight of 970,000 were added. Otherwise, a foamed sheet was produced in the same manner as in Example 2. The obtained foamed sheet had a thickness of 1.5 mm and a density of 0.12 g / cm ^{3. As} shown in Table 2, although the foaming agent retention performance was slightly low, the foam formation was good and the closed cell rate was high, The surface hardness was low and the flexibility was excellent.

Example 7 The same rubber-modified polystyrene 100 as used in Example 2
In parts by weight, a commercially available styrene-butadiene-styrene block copolymer (Ciel Chemical Co., Ltd., trade name: CAREFLEX)
20 parts by weight of TRKX155P) and 30 parts by weight of polystyrene having a Z-average molecular weight of 970,000 were added, and a foamed sheet was produced in the same manner as in Example 2 except for the above. The obtained foam sheet has a thickness of 1.4 mm and a density of 0.13 g / c.
m is ^3, as shown in Table 2, although the blowing agent retention performance is somewhat inferior, a bubble formation is satisfactory, high closed cell content, a low surface hardness, were excellent in flexibility.

Example 8 A foamed sheet was produced in the same manner as in Example 1 except that the amount of polystyrene having a Z-average molecular weight of 970,000 was changed to 45 parts by weight. The obtained foam sheet has a thickness of 2.0 m.
m, the density was 0.09 g / cm ³ , and as shown in Table 2, the foaming was good, the closed cell ratio was high, and the foaming agent retention performance was excellent, but the surface hardness was high due to the large amount of polystyrene added. And the flexibility was somewhat inferior.

Example 9 A rubber-like polymer having a salami structure in which small particles of polystyrene are scattered in the rubber polymer phase, and having an average particle diameter of 1.
The butadiene component in the rubber-modified polystyrene was 12% by weight, the butadiene rubber 1,4-cis structure ratio was 98%, and the Z-average molecular weight of the polystyrene was 45,000. A rubber-modified polystyrene resin in which the methanol-soluble content of the rubber-modified polystyrene was 0.9% by weight was used. To 100 parts by weight of this rubber-modified polystyrene resin, 15 parts by weight of polystyrene having a Z-average molecular weight of 970,000 were added, and 65% of n-butane was added.
An extruded foamed sheet was produced in the same manner as in Example 2 except that the injection amount of 35% i-butane mixed butane was continuously added so as to be 3.3% by weight of the total extrusion amount. The obtained foam sheet has a thickness of 2.6 mm and a density of 0.07 g / c.
m is ^3, bubble formation as shown in Table 2 is good, high closed cell content, good foaming agent retention performance, surface hardness is low,
In particular, it was excellent in flexibility.

Example 10 To 100 parts by weight of the rubber-modified polystyrene resin used in Example 9, 80 parts by weight of polystyrene having a Z-average molecular weight of 970,000 were added, and the other conditions were the same as in Example 9 except for the extruded foamed sheet. Was manufactured. The obtained foam sheet has a thickness of 2.6 m.
m, a density of 0.07 g / cm ³ , and as shown in Table 2, good foam formation, particularly high closed cell ratio, extremely excellent foaming agent holding performance, low surface hardness, and excellent flexibility. there were.

Comparative Example 1 A foamed sheet was produced in the same manner as in Example 3 except that only the rubber-modified polystyrene used in Example 3 was used (ie, no polystyrene was blended). The obtained foam sheet has a thickness of 1.4 mm and a density of 0.13 g / cm.
³ , as shown in Table 3, the foam formation was poor, the closed cell ratio was low, and the foaming agent holding performance was poor.

Comparative Example 2 A foamed sheet was produced in the same manner as in Example 4 except that only the rubber-modified polystyrene used in Example 4 was used (ie, no polystyrene was blended). The obtained foam sheet has a thickness of 1.2 mm and a density of 0.15 g / cm.
³ , as shown in Table 3, all of which were inferior in bubble formation, closed cell ratio, and foaming agent holding performance.

Comparative Example 3 A rubber-modified polystyrene having a core shell structure in which polybutadiene rubber in which polystyrene is encapsulated in small particles is dispersed in the form of particles, the average particle diameter of the rubber particles is 0.2 μm, A rubber-modified polystyrene having a butadiene rubber component content of 8% by weight, a Z-average molecular weight of polystyrene of 350,000 and a methanol-soluble content of 4.7% by weight was used, and otherwise the same as in Example 1. And subjected to extrusion foaming. However, this resin was much more difficult to extrude and foam into a tube than a die, and a sheet could not be obtained.

Comparative Example 4 As an extruder, a bore of φ48 having a foaming agent injection port in the middle.
A foamed sheet was manufactured in the same manner as in Comparative Example 2 except that a tandem extruder comprising a twin-screw single-stage extruder having a diameter of 90 mm and a single-screw two-stage extruder having a diameter of 90 mm was used. The obtained foam sheet has a thickness of 1.3 mm and a density of 0.14 g / c.
m is ^3, as shown in Table 3, foaming was inferior in closed cell content and a blowing agent retention performance.

Comparative Example 5 As a rubber-modified polystyrene, a rubbery polymer having a salami structure in which small particles of polystyrene are scattered in a rubbery polymer phase has an average particle diameter of 1.3 μm and a butadiene component content of 8
A foamed sheet was produced in the same manner as in Comparative Example 3 except that a rubber-modified polystyrene having a weight-average molecular weight of 310,000, a Z-average molecular weight of polystyrene of 310,000, and a methanol-soluble content of 0.2% by weight was used. . The obtained foam sheet is
It was 1.50 mm in wall thickness and 0.12 g / cm ³ in density, and as shown in Table 3, was inferior in bubble formation, closed cell ratio and foaming agent holding performance.

Comparative Example 6 A foamed sheet was produced in the same manner as in Example 9 except that only the rubber-modified polystyrene resin used in Example 9 was used (ie, no polystyrene was added). The obtained sheet has a thickness of 2.6 mm and a density of 0.07 g / cm ^3.
As shown in Table 3, the formation of bubbles was insufficient, the closed cell ratio was low, and the foaming agent retention performance was also insufficient. Tables 1, 2 and 3 show the resin blend, the physical properties of the foamed sheet, and the extruder used in each of the above Examples and Comparative Examples.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

Notes to Tables 2 and 3; * 1: styrene / butadiene / styrene block copolymer of Ciel Chemical Co., styrene content 21% by weight * 2: styrene / butadiene / styrene block copolymer of Ciel Chemical Co., Ltd. Styrene content: 40% by weight * 3: Extrusion foaming was difficult, and a secondary molded product was not obtained, and could not be evaluated.

[0067]

The rubber-modified styrenic polymer resin composition for extrusion foaming of the present invention can be prepared without using a special mixing means such as a twin-screw extruder, that is, for example, a single-screw single-stage extruder and a single-screw two-stage extrusion. By using a tandem extruder composed of an extruder, it is possible to obtain an extruded foam sheet having a sufficient foam film formation, a high closed cell rate, excellent foaming agent holding performance, and therefore excellent secondary processing properties. It is possible to easily form a container or the like having a lower surface hardness than the extruded foam sheet and having excellent flexibility and suitable for accommodating pears and peaches.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-8293 (JP, A) JP-A-53-124574 (JP, A) JP-A-6-228357 (JP, A) 60407 (JP, B2) JP 4-49861 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) C08J 9/04-9/14 C08L 1/00-101/14

Claims (4)

(57) [Claims] Claims: 1. As a resin component, (A) rubbery polymer particles are dispersed in a continuous phase of a styrenic polymer, and the rubbery polymer particles have an average particle size of 3 μm or less; Rubber-modified styrene-based polymer resin having a Z-average molecular weight of 330,000 or more and a methanol-soluble content of 4% by weight or less, and (B) a styrene-based polymer having a Z-average molecular weight of 700,000 or more A rubber-modified styrene-based polymer resin extruded foam sheet obtained by extrusion-foaming a rubber-modified styrene-based polymer resin composition containing a resin and a (C) volatile foaming agent. 2. A resin component comprising at least one resin selected from the group consisting of a styrene / butadiene block copolymer and a hydrogenated product thereof in an amount of 5 to 100 parts by weight of the resin component of the extruded foamed sheet according to claim 1. 25 parts by weight of resin composition
Oh Ru min, rubber-modified styrene polymer resin extruded foam sheet. 3. The extruded foam sheet according to claim 1, wherein the density of the extruded foam sheet is 0.05 to 0.2.
A rubber-modified styrene polymer resin extruded foam sheet having a closed cell ratio of 70% or more at g / cm ³ . 4. The extruded foam sheet according to claim 1, wherein the extrusion foaming is performed by a tandem extruder including a single-screw single-stage machine and a single-screw double-stage machine. A rubber-modified styrene polymer resin extruded foam sheet.