JP2000313778A - Resin material for biaxial orientation blow molding by cold parison method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin material good in molding stability at the time of orientation blow molding and capable of providing a polyolefin-based resin molded form excellent in thickness uniformity, transparency and flexibility. SOLUTION: This resin material is such one as to consist mainly of a polyolefin-based resin such as a propylene-α-olefin copolymer (containing >=22 wt.% of comonomer, 5-50 g/10 min in MFR) or ethylene-α-olefin copolymer produced using a metallocene-based catalyst (containing >=6 wt.% of comonomer, <=0.900 g/cm3 in density, 5-50 g/10 min in MFR) and be capable of obtaining an injection-molded sheet with 2 mm thickness having an infrared transmittance at wavelength 2.86 μm of >=25%. A molded form such as a container is obtained by using the above resin material in its biaxial orientation blow molding by cold parison method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold parison method biaxial stretch blow molding which is capable of providing a polyolefin resin molded article which is excellent in molding stability and thickness unevenness during stretch blow molding, and which is excellent in transparency and gloss. Related to resin materials.

[0002]

2. Description of the Related Art Many plastic containers such as plastic beverage bottles and cosmetic bottles are manufactured by blow molding a resin material. Conventionally, polyethylene, polypropylene, polyvinyl chloride, and polyethylene terephthalate have been mainly used as resin materials used for such blow molding. However, crystalline resins such as polyethylene and polypropylene are inferior in transparency and glossiness and are not suitable for use in transparent containers that can replace glass bottles. Polyvinyl chloride is excellent in transparency and gloss, but has problems in recyclability and hygiene.In the case of polyethylene terephthalate, it has excellent transparency and gloss, but heat shrinkage and water absorption are higher than polyethylene and polypropylene. Degradability was poor.

On the other hand, the transparency and glossiness of polyolefin resins such as polyethylene and polypropylene are improved by blow molding with stretching (stretch blow molding). For this reason, biaxial stretch blow molding by a one-stage hot parison method in which an injection molding machine and a blow molding machine are integrated has been used in part. However, since this method uses a hot parison heated by injection molding, it tends to be broken during stretch blow molding due to temperature fluctuation during injection molding, residual stress, and the like, and therefore, it is necessary to increase the draw ratio. Since it is impossible, it was difficult to obtain a molded article having high transparency and high gloss such as polyethylene terephthalate.

[0004] Further, even if an attempt is made to use a resin material having a high MFR (melt flow rate) which is excellent in transferability and the like in order to improve the transparency and glossiness, the parison will not be formed from the injection mold due to the high temperature of the parison. Mould not be released, resulting in M
Since a resin material having a high FR cannot be used, there is a problem that transparency and gloss are inferior.

As an alternative to the hot parison method, a method in which a preform once injection-molded is completely cooled (also referred to as a cold parison) is stretched and blown later, that is, a biaxial stretch blow by a two-stage cold parison method. Has recently been used. In this method, the injection molding and the stretch blow molding are separated, so it is hardly affected by the injection molding, and the preform can be sufficiently cooled and taken out of the injection mold.
A high-transparency, high-gloss blow molded article can be obtained without being restricted by the use of MFR.

[0006]

As described above, in order to obtain a high gloss and high transparency blow molded article using a polyolefin resin such as polyethylene or polypropylene, the above-described biaxial stretch blow molding by the cold parison method is required. Most preferably, in this method, the preform is heated externally or internally with an electric infrared lamp heater or the like, so that a temperature difference is likely to occur between the surface of the preform wall and the inside. Therefore, when a thick preform of the crystallized resin is stretch blow-molded, a temperature distribution occurs in the thickness direction, so that the temperature range in which blow molding can be performed is extremely narrow, and the thickness tends to be uneven (poor in uneven thickness). There was a problem.

The present invention has been made in view of such circumstances, and has good molding stability at the time of stretch blow molding, and has excellent wall thickness unevenness (it is hard to cause wall thickness unevenness), and also has excellent transparency and flexibility. An object of the present invention is to provide a cold parison method biaxial stretch blow molding resin material which can provide a molded polyolefin resin.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problem can be solved by using a resin material having an infrared transmittance of a certain level or more at a specific wavelength. The invention has been completed.

That is, the present invention relates to a resin material used for the biaxial stretch blow molding of the cold parison method, which comprises a polyolefin-based resin as a main component and a 2 mm-thick injection-molded sheet. Provided is a cold parison method biaxial stretch blow molding resin material having a transmittance of 25% or more.

In the present invention, the polyolefin resin is a random copolymer of propylene and an α-olefin, and the copolymerization ratio of the α-olefin is 2% by weight or more. The cold parison method biaxial stretch blow molding resin material is provided.

The present invention also provides the cold parison method biaxial stretch blow molding resin material, wherein the polypropylene resin has an MFR of 5 to 50 g / 10 minutes.

Further, the present invention provides that the polyolefin resin is a copolymer of ethylene and an α-olefin, and the copolymerization ratio of the α-olefin is 6% by weight or more. The resin material for the cold parison method biaxial stretch blow molding is provided.

[0013] Further, the present invention provides a method for producing a polyethylene resin, wherein the density of the polyethylene resin is 0.9.
The cold parison method biaxial stretch blow molding resin material is characterized by being a copolymer of ethylene and an α-olefin of not more than 00 g / cm ³ .

Further, the present invention provides the cold parison method biaxial stretch blow molding resin material, wherein the polyethylene-based resin has an MFR of 5 to 50 g / 10 minutes. The present invention also provides a polyolefin-based resin molded product made of any one of the above-mentioned cold parison method biaxial stretch blow molding resin materials.

[0015]

Embodiments of the present invention will be described below.

(1) Cold Parison Method Biaxial Stretch Blow Molding The resin material of the present invention is used for cold parison method biaxial stretch blow molding. The cold parison biaxial stretch blow molding method is a molding method generally used in polyethylene terephthalate container molding and the like, and the injection molding process and the stretch blow molding process are independent as separate processes. Features. Specifically, after the bottomed preform formed by injection molding is completely cooled until it is solidified, the cooled preform (cold parison) is subjected to stretch blow molding.

The molding machine used in the cold parison biaxial stretch blow molding method is generally one in which the injection molding machine and the stretch blow molding machine are independent of each other, but until the preform is completely solidified. If the cooling condition is satisfied, the injection molding step and the stretch blow step may be performed continuously.

Injection molding can be performed by a general-purpose injection molding machine equipped with one or a plurality of preform molds. First, a polyolefin-based resin material for molding is heated and melted, and pressure is applied to inject the resin material into a cavity of a mold from a nozzle to form a preform (a bottomed parison). The injection molding conditions at this time are not particularly limited, and preferably, the injection temperature is 150 to
At 250 ° C., the injection pressure is 5 kg / cm ² or more, and the mold clamping pressure is 50 ton or more. Any injection molding machine that satisfies these conditions may be used. The formed preform is quenched in a mold.

The stretch blow molding machine used in the present invention comprises:
The preform heating unit includes a preform heating unit and a blow mold unit including a stretching rod. The preform heating unit includes at least an external heating unit, and further includes an internal heating unit (an inner surface-side heating unit) as necessary. I have.

The preform molded and cooled in the injection molding step is then reheated in a preform heating section of the stretch blow molding machine. The external heating part of the preform is generally composed of an infrared lamp heater.
The infrared wavelength of the infrared lamp heater is usually 1-5 μm
Of the degree. Also, the preform inner surface side heating is not necessarily required for molding, but molding stability is improved,
Since there is an advantage that the molding cycle can be shortened, it is preferable to perform inner surface side heating. The inner side heating is usually performed by a method such as insertion of heated air or a heating rod.

The shape of the preform is a test tube shape having a mouth, and the mouth generally has a screw portion capable of fitting with a cap, but usually, the mouth does not stretch blow. The thickness of the stretch blown portion of the preform is preferably 0.5 to 6 mm. If the thickness is small, there is a problem from the viewpoint that the preform is easily deformed during conveyance and the shape retention is likely to be reduced during heating of the preform.
On the other hand, when the thickness is large, in the case of a crystalline resin such as polyolefin, the amount of transmitted infrared rays from an infrared lamp heater is reduced, and heat conduction is also deteriorated. This is not preferred because the temperature difference between the surface layer and the inside becomes large, the temperature range in which blow molding can be performed in stretch blowing becomes narrow, and the thickness tends to be uneven.

The reheated preform is stretch-blown in a blow mold provided with a stretching rod. The stretching ratio is such that the size of the final molded body is 1.5 to 5 times the preform in the longitudinal (axial) direction and 1.5 to 5 times the preform in the horizontal (circumferential) direction. preferable. In this case, the longitudinal stretching is performed by extruding a stretching rod (stretching rod) from the mouth to the bottom.
Stretch blow is performed by applying pressure in one or more stages with high-pressure air of kg / cm ² . The stretching may be performed vertically and horizontally at the same time or separately, but it is preferable that the stretching is performed at the same time.

The resin temperature (heating temperature of the preform) at the time of stretch blowing is not particularly limited because it varies depending on the optimum temperature of the resin material to be used, but in the case of a polyolefin resin, the temperature is not higher than the melting point and not lower than the crystallization temperature. Preferably, it is usually 80 to 150 ° C.

(2) Resin Material The resin material of the present invention is used for the above-described biaxial stretch blow molding of the cold parison method, is mainly composed of a polyolefin resin, and has a thickness of 2 mm. The infrared ray transmittance at a wavelength of 2.86 μm when formed into a molded sheet is at least 25%, preferably at least 30%.

The infrared transmittance of the polyolefin resin in the present invention is a value obtained by measuring the transmittance of an injection molded sheet having a wavelength of 2.86 μm and a thickness of 2 mm using a commercially available general-purpose infrared spectrophotometer. This wavelength is a central wavelength of the infrared wavelength of the infrared lamp heater and has almost no influence of absorption caused by the polyolefin skeleton structure. This injection molded sheet was injection molded at the same injection temperature and mold cooling temperature as the preform molding. Specifically, the injection temperature was 150 to 250 ° C., and the mold temperature was 2
It was injection molded under the conditions of 5 ° C. and injection pressure of 200 to 600 kg / cm ² .

As the infrared transmittance is higher, heat is more easily transmitted to the inside, so that the temperature distribution in the thickness direction is small and the temperature difference between the surface layer and the inside is small, so that it is preferable. As a method of increasing the infrared transmittance, a method of selecting a resin material having a high infrared transmittance or a method of reducing the thickness of the preform can be mentioned. There is a problem that it is easy to maintain the shape during heating. The present invention provides, as a resin material having a high infrared transmittance suitable for biaxial stretch blow molding of the cold parison method, a resin material containing a polyolefin-based resin shown below as a main component.

Polyolefin Resin The polyolefin resin used in the present invention includes a polypropylene resin or a polyethylene resin.

(I) Polypropylene Resin As the polypropylene resin used in the present invention, a homopolymer of propylene or a random copolymer or block copolymer of propylene and α-olefin containing propylene as a main component is used. No. Among them, a random copolymer of propylene and an α-olefin is preferable.

The comonomer in the random copolymer includes ethylene or an α-olefin having 4 to 8 carbon atoms. Examples of the α-olefin having 4 to 8 carbon atoms include 1-butene, 1-hexene, 1-octene, 4-methylbutene-1 and the like. Among these comonomers, ethylene or 1-butene is preferred from the viewpoint of cost and the like.

The random copolymer is obtained by subjecting propylene and one or more α-olefins to a process such as a slurry, bulk or gas phase method in the presence of a Ziegler-Natta catalyst, a metallocene catalyst or the like. Obtained by random copolymerization.

The content of α-olefin in the random copolymer is 2% by weight or more, preferably 3 to 10% by weight. If the α-olefin content is too low, the infrared transmittance tends to decrease, so that the molding stability during stretch blow molding, the unevenness in thickness is reduced, and the transparency and gloss of the obtained molded product may be poor. is there. In addition, when the thickness of the preform is large, the temperature may not sufficiently rise to the inside and molding may be difficult. On the other hand, if the content of the α-olefin is too high, there is a problem that the rigidity of the molded article is reduced and the production cost of the random copolymer itself is increased.

The MFR of the polypropylene resin used in the present invention is 5 to 50 g / 10 minutes, preferably 10 to 40 g / 10 minutes. If the MFR is low, a residual stress is generated in the preform obtained by injection molding, the molding stability during biaxial stretch blow molding is poor, and the transparency and gloss of the obtained molded product are also poor. On the other hand, if the MFR is too high, the transparency and glossiness are improved, but the impact strength of the resin material is reduced, and when used as a bottle, the drop strength is poor. The measurement of the MFR of these polypropylene-based resins is a value measured at a temperature of 230 ° C. (a load of 2.16 kg) by a flow test method of JIS-K7210 thermoplastics.

(Ii) Polyethylene Resin The polyethylene resin used in the present invention includes high-density polyethylene (HDPE) and high-pressure polyethylene (H
P-LDPE), linear low density polyethylene (LL)
DPE), ultra-low density linear polyethylene (VL-LP)
E), ethylene-vinyl acetate copolymer (EVA) and the like. These resins may be used alone or in a mixture at an arbitrary ratio.

The preferred polyethylene resin is a random copolymer of ethylene and an α-olefin (ethylene / α-olefin copolymer), and more preferably the comonomer α-olefin has 3 carbon atoms.
And an ethylene / α-olefin copolymer selected from those having a molecular weight of from 12 to 12. Particularly preferably, ethylene and the α-
It is obtained by copolymerizing an olefin with an ionic polymerization catalyst.

The α-olefin used here preferably has 3 to 10 carbon atoms, more preferably 1-butene or 1-hexene, from the viewpoint of cost and copolymerization performance. The α-olefin can be copolymerized not only alone but also in combination of two or more.

The content of α-olefin in the ethylene / α-olefin copolymer is at least 6% by weight, preferably at least 8% by weight. Although the upper limit of the α-olefin content is not particularly limited, it is 40% by weight or less, more preferably 35% by weight or less. If the α-olefin content is too low, the infrared transmittance tends to decrease, so that the molding stability during stretch blow molding, the unevenness in thickness is reduced, and the transparency and gloss of the obtained molded product may be poor. is there. In addition, when the thickness of the preform is large, the temperature may not sufficiently rise to the inside and molding may be difficult. On the other hand, if the content of the α-olefin is too high, there is a problem that the rigidity of the molded article is reduced and the production cost of the ethylene / α-olefin copolymer itself is increased.

The ionic polymerization catalyst preferably used in the production of the polyethylene resin of the present invention includes a Ziegler type catalyst and a Phillips type catalyst as a multi-site type catalyst, and a metallocene type catalyst as a single-site type catalyst. It is a metallocene type catalyst (metallocene catalyst).

The metallocene catalyst is described in International Publication WO
91/04257 and other ligands having one or two cyclopentadienyl skeletons coordinated to transition metals of groups IVb to VIb of the periodic table, preferably titanium, zirconium and hafnium Known catalysts are a combination of a metallocene compound and an alumoxane. Examples of the polymerization process include a gas phase method, a slurry method, and a bulk method, but are not particularly limited.

The density of the polyethylene resin is preferably 0.900 g / cm ³ or less, more preferably 0.8 g / cm ³ or less.
It is 50 to 0.890 g / cm ³ . If the density is too high, the infrared transmittance is reduced, so that the molding stability during stretch blow, the uneven thickness, and the transparency and gloss of the molded product are inferior. In addition, when the preform has a large thickness, the temperature does not rise to the inside, and molding becomes difficult. On the other hand, if the density is too low, the rigidity of the molded body becomes low, and ethylene / α-
There is also a problem that the production cost of the olefin copolymer increases. The density of these polyethylene resins is determined by JI
The sheet cooled at a rate of 25 ° C./min was measured by the test method of S-K6760.

The MFR of the polyethylene resin is preferably 5 to 50 g / 10 min, more preferably 10 to 40 g / 10 min.
g / 10 minutes. If the MFR is low, a preform obtained by injection molding generates residual stress, and molding stability during biaxial stretch blow molding is poor, and transparency and gloss are also poor. On the other hand, if the MFR is too high, the transparency and gloss are improved, but the impact strength of the material is reduced, and when used as a bottle, the drop strength is inferior. The MFR of these polyethylene resins was measured at a temperature of 190 ° C. (2.1 ° C.) according to the flow test method for thermoplastics according to JIS-K7210.
(6 kg load).

Preparation of Resin Material The resin material of the present invention contains the above-mentioned polyolefin-based resin as a main component. If necessary, a crystallization nucleating agent, an antioxidant, a neutralizing agent, an antistatic agent, Additives such as a light stabilizer, an ultraviolet absorber, a lubricant, an anti-blocking agent, and a coloring agent may be added within a range that does not impair the effects of the present invention. In addition, if an opaque colorant is blended, infrared rays will be absorbed only on the outer surface, and the transmittance to the inside will decrease,
Since the temperature difference between the heated outer surface and the inner surface of the preform increases, it is not preferable to add a large amount of the preform.

The resin material of the present invention is obtained by blending the polyolefin resin with additives and the like used as necessary.
It is obtained by melt-kneading. Melt kneading is preferably performed using a roll, a Banbury mixer, a single-screw kneading extruder, a twin-screw kneading extruder, or the like because dispersion is improved and transparency and gloss are excellent. In addition, as a method of compounding the additive, in addition to a method of directly mixing an amount of the additive having a predetermined concentration into the polyolefin resin, the additive is mixed in advance with a small amount of the polyolefin resin by melt-kneading to obtain a high concentration component. (Masterbatch) may be prepared, and the masterbatch method may be used in which the masterbatch is blended with a polyolefin resin and diluted to a predetermined concentration.

(3) Polyolefin resin molded article The polyolefin resin molded article of the present invention is obtained by cold parison biaxial stretch blow molding using the above-mentioned polyolefin resin material. Containers for beverages, fruit containers, food containers such as mineral water, toiletry solutions such as shampoo, rinse, liquid soap and containers for household detergents, containers for liquid cosmetics, chemical containers such as alcohol and industrial chemicals, infusion bottles, blood bottles And various containers such as medical containers.

[0044]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

[0045]

Example 1 (1) Preparation of Resin Material 100% by weight of a polypropylene random copolymer (propylene / ethylene random copolymer; MFR = 30 g / 10 minutes) having an MFR of 30 g / 10 minutes and an ethylene content of 4% by weight Parts by weight of 0.05 parts by weight of tris (2,4-di-t-butylphenyl) phosphite and tetrakis [methylenebis-3- (3 ′, 5′-di-t-butyl-4′-hydroxy) Phenyl) propionate] methane and 0.1 part by weight of calcium stearate were mixed and mixed by a Henschel mixer.
The mixture was melt-kneaded with an extruder having a single-screw full-flight screw having a diameter of 40 mm heated to 30 ° C. to obtain a pellet-shaped resin composition as the resin material of the invention.

(2) Preform molding by injection molding machine A preform was molded by an injection molding machine using the above-mentioned pellet-shaped resin composition. Specifically, Toshiba Machine Co., Ltd. I
Using an S-150E type injection molding machine, injection resin temperature 210
C., injection pressure 10 kg / cm ² , mold cooling temperature 25 ° C., outer diameter 28 mm, height 90 mm, maximum thickness 4.5 m
A test tube-shaped bottomed parison having a m and a weight of 21 g was injection molded. On the other hand, an injection sheet for infrared transmittance measurement was obtained in a sheet mold having a thickness of 2 mm at the same injection resin temperature, injection pressure and mold cooling temperature as in the preform injection molding.

(3) Infrared transmittance measurement Injection sheet for infrared transmittance measurement molded in (2) above
, IR-100 general-purpose infrared spectrophotometer manufactured by JASCO Corporation
2.86 μm (wave number 3500 cm ^-1)so
Was measured.

(4) Blow molding by a biaxial stretch blow molding machine The preform obtained in the above (2) was molded by a cold parison method biaxial stretch blow molding machine. Specifically, a biaxial stretch blow molding machine (EFB100 manufactured by Frontier KK)
0 type biaxial stretch blow molding machine) and the peak wavelength is 1 to
The preform was heated while rotating with a 2 μm electric near-infrared lamp, and when the surface temperature of the preform reached 120 ° C. with a non-contact surface thermometer, the longitudinal stretching ratio was 2.7.
A cylindrical container (molded product) having a longitudinal stretching ratio of 2.4 times was lifted with a longitudinal stretching rod and a primary pressure of 4 kg / kg.
cm ^2, and biaxial stretch blow molding by air pressure of the secondary pressure 25 kg / cm ^2, to obtain a molded body (blow container).

At this time, it was determined how many of the 10 pieces that could be formed without breaking were obtained (in the table, the number of formed bursts is shown). In addition, the preform having different surface temperatures is formed by changing the heating time or lamp output of the preform, and the upper and lower limits of the surface temperature of the preform at which no one can be formed even when 10 preforms are formed are set to 1 ° C. The difference was determined at intervals, and the difference between the upper limit temperature and the lower limit temperature at which molding was possible (molding temperature) was measured. Further, the wall thickness unevenness and transparency in the circumferential direction of the molded body (blow container) were evaluated by the following methods. Table 1 shows the results.

[Evaluation of molded article] The performance of the molded article was evaluated by the following method. 1. Circumferential wall thickness deviation: The degree of wall thickness deviation in the circumferential direction was evaluated according to the following criteria while touching the molded blow container with a hand. A: Very uniform. ＋+: fairly uniform. ：: Somewhat uniform. −-: slightly uneven Δ: considerably uneven ×: Very uneven.

2. Transparency: The degree of transparency was evaluated according to the following criteria while visually observing the molded blow container. A: Very transparent. ＋+: considerably transparent. ：: somewhat transparent. −-: somewhat opaque Δ: considerably opaque ×: Very opaque.

[0052]

Examples 2 to 11 Tables 1 to 4 show the types of resins and molding conditions.
Was performed in the same manner as in Example 1 except that the molded article obtained was evaluated. The results are shown in Tables 1 to 4. The resin material of Example 11 was obtained by melt-mixing 60% by weight of the resin material of Example 1 and 40% by weight of the resin material of Example 6 at 220 ° C. using a single screw extruder. Things.

[0053]

Comparative Examples 1 to 5 The same procedures as in Example 1 were carried out except that the types of resin, molding conditions and the like were changed to those shown in Tables 1 to 4, and the obtained molded articles were evaluated. The results are shown in Tables 1 to 4. The resin material of Comparative Example 5 was prepared by adding a master batch of carbon black having an infrared absorbing effect so that the final carbon black concentration was 2% by weight when the pellets of Example 1 were melt-kneaded. is there.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

[0058]

According to the present invention, by using a resin material having an infrared transmittance at a specific infrared wavelength which is equal to or higher than a certain value, the molding stability at the time of stretch blow molding during the biaxial stretch blow molding of the cold parison method. Thus, it is possible to obtain a molded article having excellent thickness unevenness, and excellent transparency and flexibility. As a result, it is possible to mold various containers, which were not satisfactory with conventional polyolefins, and are industrially very valuable.

Continued on the front page (72) Inventor Kazuhisa Tate 3-1 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture F-term in the Materials Development Center, Polychem Corporation 4F208 AA03C AA04E AA11H AR12 AR15 AR17 AR18 AR20 LA02 LA04 LB01 LG01 LG28 4J002 BB031 BB051 BB121 BB141 BB151 EJ037 EW066 GG01

Claims (7)

[Claims] 1. A resin material used in cold-parison biaxial stretch blow molding, which has an infrared transmittance of 25 at a wavelength of 2.86 μm when a 2 mm-thick injection-molded sheet is mainly composed of a polyolefin-based resin. % Or more, characterized in that it is a cold parison method biaxial stretch blow molding resin material. 2. The method according to claim 1, wherein the polyolefin resin is a random copolymer of propylene and an α-olefin, and the copolymerization ratio of the α-olefin is 2% by weight or more. The resin material for cold-parison biaxial stretch blow molding according to claim 1. 3. The polypropylene resin having an MFR of 5
The resin material for biaxial stretch blow molding of the cold parison method according to claim 2, wherein the resin material has a viscosity of up to 50 g / 10 minutes. 4. The polyolefin-based resin is a copolymer of ethylene and an α-olefin, wherein the α-olefin is a polyethylene resin having a copolymerization ratio of 6% by weight or more, The resin material for the cold parison method biaxial stretch blow molding according to claim 1. 5. The polyethylene resin has a density of 0.900 g / cm ³ when polymerized using a metallocene catalyst.
The cold parison method biaxial stretch blow molding resin material according to claim 1 or 4, wherein the resin material is a copolymer of the following ethylene and α-olefin. 6. The polyethylene resin having an MFR of 5 to 5.
The resin material according to claim 4 or 5, wherein the resin material is 50 g / 10 minutes. 7. A polyolefin resin molded article comprising the resin material for biaxial stretch blow molding of the cold parison method according to claim 1.