JP5481131B2 - Vinyl aromatic hydrocarbon resin composition suitable for blow molding - Google Patents

Description

The present invention relates to a vinyl aromatic hydrocarbon resin composition suitable for blow molding.

As materials generally used for blow molding, polyester-based resin compositions (Patent Document 1), polyolefin-based resin compositions (Patent Document 2), polystyrene-based resin compositions (Patent Document 3), and the like are known. Various performance improvements are achieved by the combination. Among these, a transparent and flexible resin composition (Patent Document 4) is known by combining a polystyrene resin and a polyolefin resin.

Furthermore, an example shown in Patent Document 5 is known as an attempt to use a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, or a composition raw material mainly composed of this block copolymer.

In block copolymers consisting of vinyl aromatic hydrocarbons and conjugated dienes, the impact resistance decreases when the proportion of conjugated dienes is decreased to increase the rigidity, and conversely, the proportion of conjugated dienes increases to increase the impact resistance. Increasing the number generally causes a problem such that the product is easily deformed due to softening. As a means to solve this problem, by using a molecular structure having a block made of a vinyl aromatic hydrocarbon having a relatively high molecular weight while maintaining a constant conjugated diene ratio, rigidity can be increased while maintaining impact resistance. Patent Document 6 shows that transparency when mixed with a vinyl aromatic hydrocarbon polymer can also be improved.

JP-A-5-214223 JP-A-9-59455 JP2001-2868 JP 2002-226669 A JP-A-5-98051 JP 2006-089593 A

An object of the present invention is to provide a vinyl aromatic hydrocarbon-based resin composition suitable for novel blow molding.

That is, the present invention comprises (A) a block composed of at least one vinyl aromatic hydrocarbon monomer unit, and at least one vinyl aromatic hydrocarbon monomer unit and a conjugated diene monomer unit. consists block copolymer having a block (1), is due to satisfy vinyl aromatic hydrocarbon-based resin composition (2).
(1) The ratio of the block copolymer in which the number average molecular weight of the longest block chain length (hereinafter referred to as the longest block chain length) composed of vinyl aromatic hydrocarbon monomer units is 70,000 or more and 120,000 or less is 15 mass% or more and 30 mass% or less. (2) The die swell at 180 ° C. and a shear rate of 1216 (/ s) is 1.2 or more and 1.3 or less.
(B) The vinyl aromatic hydrocarbon resin composition according to (A), wherein the proportion of the conjugated diene monomer unit is 15% by mass or more and 30% by mass or less.
(C) A vinyl aromatic hydrocarbon resin composition comprising the vinyl aromatic hydrocarbon resin composition and a styrene resin.
(D) A blow bottle in which the vinyl aromatic hydrocarbon resin composition is molded.

The vinyl aromatic hydrocarbon-based resin composition of the present invention, when blow-molded, can give a molded product having a good appearance with less vertical lines (die lines) without impairing transparency, rigidity, and impact resistance. Has characteristics.

Examples of the vinyl aromatic hydrocarbon used in the present invention include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and α-methylstyrene. , Vinyl naphthalene, vinyl anthracene, etc., with styrene being particularly preferred.

As the conjugated diene used in the present invention, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3 -Hexadiene and the like, particularly preferably 1,3-butadiene and isoprene.

The longest block chain length composed of vinyl aromatic hydrocarbon monomer units is from 70,000 to 120,000 in terms of number average molecular weight. It can be improved. If the block copolymer exceeds 120,000, a streak pattern is observed and the appearance is poor. In addition, when only a block copolymer of less than 70,000 is included, the flow is not stable during extrusion, and a wave pattern is generated or the film is drawn down, making it difficult to mold.

Further, regarding the mass ratio of the conjugated diene to the entire mass of the vinyl aromatic hydrocarbon resin composition, the mass ratio of the conjugated diene monomer unit is 15% by mass in order to ensure practical impact resistance and flexibility. It is above, Preferably it is 20 mass% or more. In order to maintain moldability and rigidity, it is 30% by mass or less, preferably 27% by mass or less, and more preferably 24% by mass or less. When the mass ratio of the conjugated diene monomer unit is less than 15 mass%, the impact resistance is insufficient, and thus it cannot be put to practical use. In addition, if the mass ratio of the conjugated diene monomer unit exceeds 30% by mass, the blow moldability may be impaired, and a satisfactory product form may not be obtained. This can cause production problems such as

Furthermore, as for the molecular weight of the block copolymer, it is desirable that the number average molecular weight (polystyrene conversion method) by gel permeation chromatography (hereinafter GPC) is in the range of 50,000 to 500,000. When the molecular weight of the block copolymer is less than 50,000, it is difficult to maintain the shape of the parison in a semi-molten state, for example, at the time of blow molding, and a good product may not be obtained. On the other hand, if it exceeds 500,000, the fluidity is deteriorated, so that it takes a lot of time and energy to produce the block copolymer, and the molding processability is also lowered, which is not preferable in practice.

The block copolymer of the present invention can be produced by living anionic polymerization. In the living anion polymerization, since the polymerization of the raw material monomer continues in a chemically stable organic solvent as long as the polymerization active terminal is present, the residual monomer can be kept low. Further, unless there are special conditions, there is a characteristic in the polymerization reaction that the deactivation of the reaction active terminal during the polymerization and the movement of the polymerization active site do not occur. Therefore, the molecular weight and molecular structure of the copolymer in the present invention are the same as those of the monomer, the polymerization initiator, the randomizing agent, and the proton donating substance (hereinafter referred to as “polymerization terminator”) used for deactivating the active terminal. It is possible to control by changing the amount, the timing of addition, the number of times of addition, and the order of addition as appropriate according to the purpose.

For example, when polymerizing a block having a so-called tapered structure in which the proportion of vinyl aromatic hydrocarbon monomer units and conjugated diene monomer units changes continuously, vinyl aromatic hydrocarbon and conjugated diene are simultaneously bundled. Can be added to the reaction system.

Furthermore, in order to make a block having a random structure of a vinyl aromatic hydrocarbon monomer unit and a conjugated diene monomer unit, a vinyl aromatic hydrocarbon and a conjugated diene may be charged into the reaction system little by little at the same time. Moreover, when polymerizing a random block, in order to make it react as uniformly as possible, it is preferable to keep the temperature of a reaction system constant between 40 degreeC-120 degreeC. Further, when making a taper structure or a random structure, a randomizing agent can be appropriately added in the reaction system in order to further enhance the randomness of the vinyl aromatic hydrocarbon and the conjugated diene.

In the present invention, the randomizing agent is a polar molecule, and amines, ethers, thioethers, phosphoramides, alkylbenzene sulfonates, and other potassium or sodium alkoxides can be used. Suitable amines include tertiary amines such as trimethylamine, triethylamine, tetramethylethylenediamine, and cyclic tertiary amines. Examples of ethers include dimethyl ether, diethyl ether, diphenyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, and tetrahydrofuran. In addition, triphenylphosphine, hexamethylphosphoramide, potassium alkylbenzenesulfonate or butoxide such as sodium, potassium, and sodium can be used.

One or more randomizing agents can be used, and the addition ratio is suitably 0.001 to 10 parts by mass in total per 100 parts by mass of the monomer used as a raw material.

Polymerization solvents include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane and isooctane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane, or benzene and toluene. Aromatic hydrocarbons such as ethylbenzene and xylene can be used.

The organolithium compound that is a polymerization initiator is a compound in which one or more lithium atoms are bonded in the molecule. In the present invention, for example, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyl Monofunctional polymerization initiators such as lithium and tert-butyl lithium, and polyfunctional polymerization initiators such as hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium can be used.

In the present invention, at least one or more selected from water, alcohols, inorganic acids, organic acids, and phenolic compounds is selected as a polymerization terminator, and the polymerization is terminated when added to the reaction system. Water can be used in particular as a polymerization terminator. Since the deactivation stoichiometric number of the polymerization active terminal is proportional to the stoichiometric number of the added polymerization terminator, only a part of the polymerization active terminal is deactivated during the polymerization, and then additional raw material monomers are added. In addition, a production method in which polymerization is further continued can be employed. There is no particular limitation on the number of deactivations during the process unless all the polymerization active terminals are deactivated.

Methanol, ethanol, butanol, etc. as alcohols as polymerization terminators, hydrochloric acid, sulfuric acid, nitric acid, boric acid, phosphoric acid, carbonic acid etc. as inorganic acids, octyl acid, capric acid, lauric acid, myristic acid as organic acids , Carboxylic acids such as palmitic acid, stearic acid, olefinic acid, linoleic acid, linolenic acid, ricinoleic acid, behenic acid, other sulfonic acids, sulfinic acids, etc. are 2- [1- (2-hydroxy-3) as phenolic compounds. , 5-Di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl)- 4-methylphenyl acrylate, octadecyl-3- (3,5-di-tert-butyl Such as 4-hydroxyphenyl) propionate and the like.

When the polymerization is completed, it is necessary to deactivate all the active ends by adding a sufficient amount of a polymerization terminator to the number of active ends at that time.

As a method of separating the copolymer solution after the deactivation treatment from the solvent, (1) a method of precipitating in a poor solvent such as methanol, (2) supplying the copolymer solution to a heating roll, Method of separating only copolymer by evaporating solvent (drum dryer method), (3) The heated copolymer solution was kept at a pressure lower than the equilibrium vapor pressure at the temperature of the organic solvent contained therein. Method of devolatilization by supplying continuously or intermittently into cans (flash evaporation method), (4) Method of devolatilization through vent type extruder, (5) Co-weighting while stirring in warm water Examples include a method in which a combined solution is blown to evaporate the solvent (a steam stripping method) and a combination of these.

Furthermore, the block copolymer of the present invention thus produced can be mixed with a styrene resin containing at least one selected from the following polymers, if necessary.

The styrenic resin that can be mixed with the block copolymer of the present invention may be one obtained by polymerizing vinyl aromatic hydrocarbons, and polystyrene is preferably used. Examples of other styrenic resins include vinyl aromatic hydrocarbon- (meth) acrylic acid esters and / or (meth) acrylic acid copolymers. Examples of (meth) acrylic acid ester monomers include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like. Examples of the acid monomer include acrylic acid and methacrylic acid. Furthermore, high impact polystyrene can be added for the purpose of improving the blocking property within a range that does not greatly affect the transparency.

In the present invention, the blending ratio of the styrene resin is preferably 70 parts by mass or less with respect to 100 parts by mass of the block copolymer. When it exceeds 70 mass parts, there exists a tendency for the impact resistance of the molded object obtained to be impaired. In particular, when high impact polystyrene is used, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less. If the amount exceeds 5 parts by mass, the original transparency is hindered, and the effect of the present invention becomes meaningless. These vinyl aromatic hydrocarbon polymers are preferably mixed by melt kneading using an extruder or the like. In addition, it is possible to perform secondary processing into various shapes and sheets at the same time while melt-kneading with an injection molding machine or a sheet extruder.

Various additives can be further blended in the vinyl aromatic hydrocarbon resin composition obtained in the present invention as long as the transparency is not hindered. When the vinyl aromatic hydrocarbon resin composition is subjected to various heat treatments, or the molded product is used in an oxidizing atmosphere or under irradiation with ultraviolet rays, etc. In order to further impart physical properties suitable for, additives such as stabilizers, lubricants, processing aids, antiblocking agents, antistatic agents, antifogging agents, weather resistance improvers, softeners, plasticizers and the like can be added.

Examples of the stabilizer include 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,6- Phenolic antioxidants such as di-tert-butyl-4-methylphenol, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, trisnonylphenyl phosphite, bis (2,6 -Di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite Such as down-based antioxidants.

In addition, as lubricants, processing aids, antiblocking agents, antistatic agents, and antifogging agents, saturated fatty acids such as palmitic acid, stearic acid and behenic acid, fatty acid esters such as octyl palmitate and octyl stearate, and pentaerythritol fatty acid Esters, fatty acid amides such as erucic acid amide, oleic acid amide, stearic acid amide, ethylene bis stearic acid amide, glycerin-mono-fatty acid ester, glycerin-di-fatty acid ester, and sorbitan-mono-palmitic acid ester Sorbitan fatty acid esters such as sorbitan mono-stearate, higher alcohols such as myristyl alcohol, cetyl alcohol, stearyl alcohol, paraffin wax, And petroleum waxes Tallinn waxes.

Further, as weather resistance improvers, benzotriazoles such as 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole and 2,4-di-tert-butylphenyl Salicylates such as -3 ', 5'-di-tert-butyl-4'-hydroxybenzoate, benzophenone UV absorbers such as 2-hydroxy-4-n-octoxybenzophenone, and tetrakis (2,2, Examples include hindered amine type weather resistance improvers such as 6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate. White oil and silicone oil can also be added.

These additives are desirably used in an amount of 5 parts by mass or less based on 100 parts by mass of the vinyl aromatic hydrocarbon resin composition. If it exceeds 5 parts by mass, it may cause a decrease in transparency, or may be deposited on the surface of the molded article to cause a poor appearance or a decrease in label adhesion.

The vinyl aromatic hydrocarbon-based resin composition of the present invention is preferably provided as a product such as a container that is blow-molded to have a good appearance and practical strength.

The blow molding method may be a generally known extrusion blow molding or the like, and may follow normal molding conditions and does not require special consideration. The general molding temperature is 170 ° C to 220 ° C. Specific examples of blow-molded products mentioned here include, for example, foods, beverages, and chemical bottles, but the present invention is not particularly limited by these product forms, and is appropriately used as a general-purpose raw material. Can be used.

In the present invention, an antistatic agent or a lubricant may be applied to the surface in order to improve the surface characteristics of the obtained molded product.

The die swell of the vinyl aromatic hydrocarbon resin composition of the present invention has a molding temperature of 180 ° C. suitable for blow molding and a shear rate of 1216 (/ s) at which a strand descending speed close to the actual parison descending speed is obtained. It is 1.2 or more and 1.3 or less under conditions. If the die swell is smaller than 1.2, the parison is difficult to swell and blow molding is difficult, and if the die swell exceeds 1.3, minute irregularities (scratches) at the die exit are easily transferred to the outer surface of the parison. Streaks (die lines) tend to become more prominent and melt fracture tends to occur. The die swell can be adjusted by changing the number average molecular weight of the block copolymer and the ratio of the conjugated diene monomer unit. The number average molecular weight of the block copolymer increases or the ratio of conjugated diene monomer units decreases, so that the die swell value increases and the number average molecular weight decreases or the ratio of conjugated diene monomer units. Decreases due to increase. Furthermore, the ratio of the block copolymer having a number average molecular weight of 70,000 or more and 120,000 or less in the longest block chain length is 15 to 30% by mass in the resin composition. Appearance is improved during molding. When the content exceeds 30% by mass, the vertical lines (die lines) of the molded product tend to be noticeable, and the appearance deteriorates.

The present invention is effective for obtaining a molded product by blow molding.

Hereinafter, the present invention will be described with reference to reference examples, examples and comparative examples. However, the present invention is not limited to the examples.

The block copolymers used in Examples and Comparative Examples were prepared according to the following reference examples.

(Reference Example 1)
Block copolymer 1
(1) In a reaction vessel having a volume of 1.3 m ³ , 514 kg of cyclohexane containing 150 ppm of tetrahydrofuran (hereinafter THF) was added, and 15.6 kg of styrene monomer was further added. The temperature at this time was 27 ° C.
(2) Next, 1730 mL of a cyclohexane solution (initiator) containing n-butyllithium was added, and the temperature was raised to 80 ° C. to polymerize the styrene monomer.
(3) Thereafter, the temperature was lowered to 65 ° C., 75.6 kg of styrene and 37.6 kg of butadiene were added all at once, and polymerization was continued.
(4) Thereafter, 71.2 kg of styrene monomer was added at 40 ° C. for polymerization. At this time, the temperature rose to 78 ° C, but then the temperature was cooled to 70 ° C.
(5) The resin liquid was transferred to another tank and then deactivated by adding 165 g of water to obtain a copolymer having a number average molecular weight of 202,000.
(6) An antioxidant was added to the obtained resin liquid, and a pellet-shaped resin was obtained by deaeration extrusion with a twin-screw extruder with a vacuum vent.

(Reference Example 2)
Block copolymer 2
(1) In the same reaction vessel as in Reference Example 1, 470 kg of cyclohexane containing 150 ppm of THF was added, and 10.1 kg of styrene monomer was further added. The temperature at this time was 29 ° C.
(2) Next, 1810 mL of a cyclohexane solution (initiator) containing n-butyllithium was added and the temperature was raised to 80 ° C. to polymerize the styrene monomer.
(3) Thereafter, the temperature was lowered to 60 ° C., and 4.2 kg of butadiene was added all at once and polymerized.
(4) Thereafter, the temperature was lowered to 50 ° C., 57.8 kg of styrene and 32.0 kg of butadiene were added all at once, and polymerization was continued.
(5) Thereafter, 96.2 kg of styrene monomer was added at 40 ° C. for polymerization. At this time, the temperature rose to 84 ° C., but then the temperature was cooled to 70 ° C.
(6) The resin solution was transferred to a separate tank and then deactivated by adding 165 g of water to obtain a copolymer 2 having a molecular weight of 218,000.
(7) The antioxidant was added to the obtained resin liquid in the same manner as in Reference Example 1, and the mixture was degassed and extruded with a twin-screw extruder with a vacuum vent to obtain a pellet-shaped resin.

The block copolymers 3 to 10 were also polymerized by changing the amounts of the styrene monomer, butadiene, and initiator described in Reference Examples 1 and 2, and then deactivated with water, added with an antioxidant, and decompressed. A pellet-shaped resin was obtained by deaeration extrusion with a twin screw extruder with a vent.

The number average molecular weight described in the present invention was measured using the following apparatus.
Device name: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: 4 KF-404HQ (made by Showa Denko KK) Series connection temperature: 40 ° C
Detection: Differential refractometer Solvent: Tetrahydrofuran concentration: 1 mg / 1 mL (THF)
Flow rate: 0.2 mL / min Pressure: 3.8 MPa
Other: The number average molecular weight of the present invention is a molecular weight obtained by applying the retention time of the peak top of each sample to a calibration curve prepared using a standard polystyrene set (PL-1 manufactured by PL Co.) having a known peak top molecular weight. (PS conversion value).

Table 1 shows the number average molecular weight of block copolymers 1 to 10 and the ratio of conjugated diene monomer units. The longest block chain length is the number average molecular weight of the peak having the largest number average molecular weight among the peaks obtained by the following method.

The chain length of the vinyl aromatic hydrocarbon block of the block copolymer can be controlled by the amount charged when polymerizing the vinyl aromatic hydrocarbon and the conjugated diene. Here, the longest block chain length is determined by ozonolysis of the block copolymer by a method described in a known document “Y. TANAKA, et.al., RUBBERCHEMISTRY AND TECHNOLOGY” 59, 16 (1986). The gel aromatic permeation chromatograph (hereinafter abbreviated as GPC) is measured for the obtained vinyl aromatic hydrocarbon polymer component, and the molecular weight corresponding to the chromatogram is obtained from a calibration curve created using a standard polystyrene set, Those exceeding the number average molecular weight of 3,000 were determined from the peak area. An ultraviolet spectroscopic detector with a wavelength set at 254 nm was used as the detector.

The proportion of the conjugated diene monomer unit in the block copolymer can be controlled by the amount of conjugated diene charged. From this, the ratio of the conjugated diene monomer unit was calculated.

About an Example and a comparative example, each block copolymer was blended in the ratio of Table 2, 3. FIG. Moreover, about the styrene resin, the following were used.

General-purpose polystyrene (hereinafter GPPS)
Toyo Styrene Co., Ltd., Toyostyrene G200C, MFR 7.0

Hereinafter, although evaluation of an Example and a comparative example is shown in detail, the item is as follows.

Using a Capillograph 1B (die length: 40 mm, diameter: 1 mm) manufactured by Dieswell Toyo Seiki Co., Ltd., values at a temperature of 180 ° C. and a shear rate of 1216 (/ s) were measured.

For the measurement of the following items, a multipurpose test piece A defined in JIS K-7139 was used.
A haze turbidimeter NDH-300A (manufactured by Nippon Denshoku Co., Ltd.) was used to measure based on JIS K 7136.
The bending elastic modulus was measured based on JIS K 7171 using a bend graph manufactured by Toyo Seiki Co., Ltd.

For measurement of the following items, a sheet (thickness: 0.6 mm) produced using a single-axis 40 mmφ (die: T-die type) sheet extruder was used.
DuPont impact strength A DuPont impact tester was used to determine a 50% fracture strength at n20 using a striker with a weight of 100 g and a tip of 12.7 mm. As the shape of the test piece, the above sheet cut to a width of 50 mm and a length of 200 mm was used.

For the measurement of the following items, it was obtained by sheet external extrusion sheet molding using a sheet (width: 40 mm) prepared using a twin screw extruder type lab plast mill (die: T-die type) manufactured by Toyo Seiki Co., Ltd. The obtained sheet was visually observed.
○: 3 or less streaks in the flow direction.
Δ: More than 3 and less than 10 streaks are confirmed in the flow direction.
×: More than 10 streaks are confirmed in the flow direction.

For the measurement of the following items, a small bottle produced using a JB-201-2 type hollow molding machine manufactured by Nippon Steel Works, Ltd. was used.
(Temperature 175-187 ℃, cycle 8 seconds)
Blow moldability appearance The obtained molded product was judged by appearance. Same as above ○: 3 or less streaks in the flow direction.
Δ: More than 3 and less than 10 streaks are confirmed in the flow direction.
X: More than 10 streaks are confirmed in the flow direction, or molding is not possible.

The evaluation results of Examples 1 to 5 are shown in Table 2. From this result, the transparency of the resin composition of the present invention was good with a haze of 0.8 to 1.1, and the bending elastic modulus was also maintained at 1390 to 1650 MPa. Further, the DuPont impact strength was maintained at a practical strength of 0.1 to 0.4 kJ / m. Further, it can be seen that there is no vertical line (die line) in the extruded sheet or blow molded bottle, and the appearance is good.

Table 3 shows the results of Comparative Examples 1-8.
In Comparative Example 1, it can be seen that the longest block chain length of the copolymer contained is long, and the sheet appearance and the blow-molded product are warped (die line), which is not appropriate. In Comparative Example 2, it was composed only of a resin having the shortest block chain length, and although the sheet appearance was good, the die swell was low and blow molding could not be performed. In Comparative Example 3, the die swell value was low and molding could not be performed. In Comparative Examples 4 and 5, the die swell is high, and the appearance is poor at the time of sheet or blow molding. In Comparative Examples 6 and 7, although the copolymer satisfying the longest block chain length is contained, the blending amount is large, and the appearance of the sheet or appearance is poor at the time of molding. Further, in Comparative Example 8, the content of the copolymer having an appropriate longest block chain length is small, the appearance is poor, the flexural modulus is too low as 1230 MPa, and the molded product is not deformed after blow molding. Prone to occur.

Claims (4)

A block consisting of at least one vinyl aromatic hydrocarbon monomer units, made from a block copolymer having blocks consisting of at least one vinyl aromatic hydrocarbon monomer units and conjugated diene monomer units , (1), a vinyl aromatic hydrocarbon resin composition that satisfies the conditions of (2).
(1) The ratio of the block copolymer having a number average molecular weight of the longest block chain length composed of vinyl aromatic hydrocarbon monomer units of 70,000 to 120,000 is 15% by mass to 30% by mass. Less than.
(2) The die swell at 180 ° C. and a shear rate of 1216 (/ s) is 1.2 or more and 1.3 or less. The vinyl aromatic hydrocarbon resin composition according to claim 1, wherein the proportion of the conjugated diene monomer unit is 15% by mass or more and 30% by mass or less. A vinyl aromatic hydrocarbon resin composition comprising the vinyl aromatic hydrocarbon resin composition according to claim 1 or 2 and a styrene resin. A blow molded article using the vinyl aromatic hydrocarbon resin composition according to any one of claims 1 to 3.