JP2000355045A - Hollow molded article and blow molding method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow molded article excellent in molding processability, wall thickness distribution, surface gloss, transparency and flexibility, high in mechanical strength, capable of being reduced in wall thickness and wt. and easily folded to be reduced in volume. SOLUTION: A hollow molded article is molded by the blow molding of a parison having at least one layer comprising a compsn. containing polyethylene with a melt flow rate of 4 g/10 min or less obtained by copolymerizing ethylene and a higher α-olefin by a metallocene catalyst and polyethylene with a melt flow rate of 10 g/10 min or more obtained by copolymerizing ethylene and a higher α-olefin by a metallocene catalyst in a wt. ratio of 98:2-60:40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article mainly composed of low-density polyethylene, and more particularly, to surface gloss, transparency, impact strength, and flexibility made of low-density polyethylene copolymerized using a metallocene catalyst. TECHNICAL FIELD The present invention relates to a hollow molded article excellent in heat resistance, environmental stress cracking property and the like, and a blow molding method thereof.

[0002]

2. Description of the Related Art Conventionally, blow molded articles made of polyethylene resin have been widely used.

[0003] In this hollow molded article, a composition mainly composed of a polyethylene resin is extruded or injection molded to form an intermediate molded article (preform or parison) for hollow molding, and the intermediate molded article is blow molded. Various types of liquid filling bottles, containers for industrial chemicals, containers for transportation and storage, and other hollow molded products are known.

[0004] The polyethylene resin used is a low-density polyethylene used for molded articles such as relatively small and medium-sized containers because it is called soft polyethylene and is milky white, translucent and rich in flexibility. Also, there is a high-density polyethylene which is widely used in molded products such as small to large containers because of its high rigidity which is called hard polyethylene.

[0005] A hollow molded article using low-density polyethylene is excellent in transparency and flexibility, but has poor mechanical strength, and a hollow molded article using high-density polyethylene has low resistance to chemicals. Excellent in properties and mechanical strength, but poor in flexibility.

There is also a polyethylene obtained by copolymerizing ethylene and a high (4-12 carbon atoms) α-olefin with a metallocene catalyst (hereinafter referred to as “metallocene polyethylene”).

Metallocene polyethylene is superior to conventional low-density polyethylene in terms of surface gloss, transparency, flexibility, environmental stress cracking resistance (ESCR), impact strength, extraction resistance, low-temperature heat sealability, and the like. Because of its characteristics, it is mainly used in the field of film products by utilizing its characteristics.

Further, in order to make use of the excellent characteristics in a hollow molded article such as a container, a composition comprising a mixture of metallocene polyethylene and low-density polyethylene or high-density polyethylene is blow-molded to form a hollow molded article. Has also been done.

[0009]

The metallocene polyethylene has a relatively narrow molecular weight distribution as compared with conventional low-density polyethylene, and also has butene and hexene because the active site of the metallocene catalyst is uniform (single site). And the like, and the composition distribution is similarly narrow, and further, the low molecular weight component is extremely small. In addition, the solid structure has structural features different from those of conventional low-density polyethylene, such as a thin crystalline lamella and a molecular skeleton with many tie molecules.

As a result, the metallocene polyethylene has a low non-Newtonian viscosity compared to conventional low-density polyethylene, and therefore has a unique melt flow such as a low melt viscosity in a low shear rate region and a high melt viscosity in a high shear rate region. It exhibits properties and is prone to drawdown and melt fracture.

In the case of a blow molding method, in particular, a direct blow (or extrusion blow) molding method, in which a so-called cylindrically extruded intermediate molded body is sandwiched between molding dies and air is blown into the molding die, the draw of the intermediate molded body is performed during molding. There is a problem in molding processability such as large down, and rough surface called sharkskin (shark skin surface) is likely to occur on the surface of the hollow molded product, and it is difficult to make appearance characteristics such as surface gloss and transparency. It can be a factor.

[0012] Therefore, it has been practiced to blow-mold an intermediate molded article of a composition obtained by mixing a metallocene polyethylene and a conventional low-density polyethylene or high-density polyethylene to form a hollow molded article. There is now a step forward in molding hollow molded products that make full use of excellent properties.

[0013]

DISCLOSURE OF THE INVENTION The present invention provides excellent moldability without impairing the properties of metallocene polyethylene, as well as surface gloss, surface smoothness, transparency, and the like.
It has excellent properties such as flexibility, impact resistance, environmental stress cracking resistance, extraction resistance, and squeezing property. Moreover, if the density is the same, the mechanical strength such as tensile rupture strength is large, and the thickness of molded products is reduced. A hollow molded article and a blow molding method suitable for reprocessing after use because the weight can be reduced and the volume can be easily folded to reduce the volume. And a high α-olefin are copolymerized to obtain a melt flow rate of 4 g /
A polyethylene having a melt flow rate of 10 g / 10 minutes or more obtained by copolymerizing ethylene and a high α-olefin with a metallocene catalyst at a weight ratio of 98: 2 to 60:40 is used. A molded article obtained by blow molding a parison provided with at least one layer of the composition to be contained.

Further, in a blow molding method for a hollow molded article in which a parison extruded from an extruder is suspended and held in a molding die, cut with an electric heat cutter, and air is blown into the parison from an air blowing nozzle, Flow rate obtained by copolymerizing ethylene and high α-olefin with a metallocene-based catalyst and polyethylene having a melt flow rate of 4 g / 10 min or less obtained by copolymerizing ethylene and high α-olefin with a system catalyst Is 10
g / 10 minutes or more and 98: 2 to 6
A composition containing the composition in a weight ratio of 0:40 was mixed with an extruder.
It is a molding method in which the composition is melted and extruded into a parison having at least one layer of the composition, and air is blown into the parison.

Still further, when the parison is cut by an electric heating cutter, a molding method for extending at least the cutting portion of the parison in the axial direction, and an air-blowing nozzle which has been subjected to lubricity treatment on the outer peripheral surface of the nozzle is inserted into the parison opening; There is a molding method in which air is blown into the parison from the nozzle.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The metallocene polyethylene used in the present invention is a metallocene-based catalyst which contains ethylene and C4 to C4.
It is obtained by copolymerizing 12 high α-olefins. Then, the melt flow rate (hereinafter referred to as “MF
R ") is less than 4 g / 10 minutes and 10 g /
Those having a duration of 10 minutes or more are preferably used.
Metallocene polyethylene (hereinafter sometimes referred to as “metallocene polyethylene-A”) has a MFR of 0.1 to 4 g / 10 min, preferably 2 to 3.5 g / 10 min.
Metallocene polyethylene having a large MFR (hereinafter sometimes referred to as “metallocene polyethylene-B”) has an MFR of 10 to 20 g / 10 min, preferably 1
4 to 18 g / 10 min.

If the MFR is more than 4 g / 10 minutes in the above-mentioned metallocene polyethylene-A and more than 20 g / 10 minutes in the case of metallocene polyethylene-B, it is not preferable because it causes problems in molding processability such as large drawdown.

The mixing ratio of metallocene polyethylene-A and metallocene polyethylene-B is such that metallocene polyethylene-A: metallocene polyethylene-B is 98: 2-6.
0:40, preferably 95: 5 to 70:30,
In this embodiment, metallocene polyethylene-A having a small MFR is used as a matrix resin, and metallocene polyethylene-B having a large MFR is added thereto.

If the mixing ratio is larger than the above-mentioned value, problems arise in molding workability such as a large drawdown and the like, which is not preferable. If the mixing ratio is too small, the surface of the hollow molded product is said to be sharkskin (shark skin surface). It is not preferable because skin roughness easily occurs and appearance characteristics are difficult.

If necessary, colorants such as pigments and dyes, antistatic agents, ultraviolet absorbers, antioxidants,
Light stabilizers, slip agents, inorganic or organic fillers, nucleating agents, and other processing aids may be added.

The metallocene polyethylene-A and the metallocene polyethylene-B are usually used by mixing each granular resin (pellet) and putting it into a hopper such as an extruder. Kneading in a state where the two are not integrated (homogenized) by an extruder, etc. For example, melt and extrude in an inhomogeneous state to the extent that the resins of different MFRs are each maintained substantially at the original MFR without being mixed together Alternatively, a resin obtained by converting the resin into a granular resin (repellet) may be used.

The hollow molded article of the present invention has at least one
One layer is formed of a composition containing metallocene polyethylene-A and metallocene polyethylene-B in a weight ratio of 98: 2 to 60:40, preferably 95: 5 to 70:30, , A single-layer configuration, or a multi-layer configuration. The configuration of the plurality of layers is a configuration in which the layers of the composition are laminated, and the MFR and the weight ratio are different between the layers, or at least one layer is a layer of the composition, and another layer is the layer of the composition. The product is a laminate of a layer of a composition having an MFR or a weight ratio out of the range, a layer obtained by recycling these compositions, or a layer of a polyolefin resin such as high-density polyethylene, low-density polyethylene, or polypropylene. You may.

The thickness of the hollow molded article is generally 0.1 to 5 mm, preferably 0.3 to 3 mm,
In the case of a plurality of layers, the composition layer
To 3 mm, preferably 0.2 to 2 mm, and the other one or more layers have a thickness of 0.02 to 3.5 mm, preferably 0.05 to 2 mm.

Examples of hollow molded articles include various detergent bottles such as shampoo and rinse for hair washing, clothing detergents and dishwashing detergents, medical infusion bottles, filling bottles for drinking water, soup and edible oil, and carton boxes. Containers such as airbags and bag-in-boxes, ice pillows and cool storage containers that contain ice and frozen liquid for cold and hot water utilizing properties such as flexibility and impact strength at low temperatures, and pinch-off strength using good heat sealability. These include high-handled bottles and other various molded products for food and sundries. Moreover, the hollow molded article after use can be easily folded and reduced in volume by making use of characteristics such as flexibility, so that it is also suitable for regeneration processing or the like.

The hollow molded article is an intermediate molded article (hereinafter sometimes referred to as "parison") provided with at least one layer of the above-mentioned composition, and various blow molding methods using this parison, for example, a screw type extruder Or blown parison extruded by a ram extruder into a molding die, cut it with an electric heat cutter, and then blow air from the air blow nozzle into the parison. Parison method,
Further, it is molded by a cold parison method in which a bottomed parison is injection-molded, and the like, and a direct blow molding method using a screw type extruder that effectively affects the moldability of the above composition is preferable.

In this direct blow molding method, when the extruded parison is cut, the cut end of the parison may be cut in an inclined state or a closed state because the parison is soft. To prevent this, at least the cutting point of the parison is extended in the axial direction when the parison is cut by the electric heat cutter.Specifically, the relative height in the vertical direction between the crosshead where the parison hangs and the molding die that holds the parison is increased. It is preferable to perform operations such as cutting with an electric cutter while the parison is extended by moving, or performing preliminary blowing immediately before cutting the parison.

Since the density of the metallocene polyethylene is as low as 0.89 to 0.92, it is soft and sticky. Therefore, after the air blowing / cooling is completed, the air blowing nozzle is connected to a parison (or a hollow molded product). When the air blow nozzle is pulled out from the opening, the air blowing nozzle may be in close contact with the inner surface of the opening and may not be smoothly removed, thereby damaging the opening. In order to prevent this, it is preferable to perform a lubricity treatment of coating the outer peripheral surface of the air blowing nozzle inserted into the opening of the parison with, for example, Teflon or ceramic. Thus, more stable continuous production can be performed.

The present invention provides a composition comprising a mixture of at least two metallocene polyethylenes having different MFRs.
By using a blow molded intermediate molded product and a hollow molded product, when extruded from a die of an extruder, the intermediate molded product can be molded without generating drawdown, and a shark skin or the like due to melt fracture does not appear. A hollow molded article having excellent surface gloss and transparency can be obtained.

Although the reason for this is not clear, a high melt viscosity can be obtained by using a metallocene polyethylene having a high melt viscosity (low MFR) as a matrix resin and adding a metallocene polyethylene having a low melt viscosity (high MFR) to the matrix resin. The metallocene polyethylene having a low melt viscosity is layered in the flow direction inside the metallocene polyethylene having a non-uniform structure, and the shear stress in the die that causes melt fracture is reduced by the metallocene polyethylene having a low melt viscosity. Drop,
It is also assumed that the elongational flow after exiting the dice, which causes drawdown, is due to being suppressed by the metallocene polyethylene having a high melt viscosity.

In the first place, the melt fracture phenomenon occurs in a shear flow field in which a molten resin flows in a die due to an extrusion pressure in an extruder, and the drawdown phenomenon is caused by the weight of the intermediate molded product when it is extruded from the die. This is a flow form that occurs in a so-called elongational flow field that is elongated in the direction of gravity. The former phenomenon is caused by the shear stress inside the die, and the latter phenomenon is caused by the melt viscosity in the elongational flow field outside the die.

Therefore, when a low melt viscosity metallocene polyethylene having a low melt fracture phenomenon is added to a high melt viscosity metallocene polyethylene having a low drawdown phenomenon, these metallocene polyethylenes intervene in a flow direction in a die of a molding machine. The low melt viscosity metallocene polyethylene contributes to lowering the shear stress more than the addition ratio, and the high melt viscosity metallocene polyethylene as the matrix resin contributes to preventing the drawdown phenomenon outside the die. It is thought to be.

[0032] These phenomena are also apparent from consideration based on the following model.

FIGS. 1 (a), 1 (b) and 1 (c) show a high-viscosity resin (MFR = 2.2) and a low-viscosity resin (MFR = 16.
5) is a comparative calculation example of a velocity distribution and a shear stress distribution of a simplified multilayer structure model in the case of existing in a layered form, and shows a model of a decrease in shear stress which is an effect of preventing melt fracture. In the figure, for example, high melt viscosity (MFR =
2.2) Metallocene polyethylene (high viscosity resin) is 1
00% (weight ratio) and high melt viscosity (MFR = 2.
10% (weight ratio) of a metallocene polyethylene (low viscosity resin) having a low melt viscosity (MFR = 16.5) was added to and mixed with the metallocene of 2), and all of the added low viscosity resin (10
%) Is assumed to be interposed in a layered manner in the flow direction at that thickness.

FIG. 1 (a) shows the position in the thickness direction in the fluidized bed when the whole (100%) of a high-viscosity resin composition was flown, and the shear stress (Kgf / cm ^-2 ) and flow at that position. The relationship with the speed (cm / sec) is shown. However, the position in the flow channel thickness direction is 0 at the center, + indicates the outer surface side, and-indicates the inner surface side. (Hereinafter, “FIG. 1 (b)”, “FIG. 1
(The same applies to “(c)”.) From this figure, it can be seen that the shear stress on the wall surface involved in the occurrence of melt fracture is as high as 2.4 (Kgf / cm ⁻² ).

FIG. 1 (b) shows that 10%
In the case where the low-viscosity resin is present in a layer at a position 1/3 from the surface in a composition to which a low-viscosity resin (weight ratio) is added and mixed, the position in the thickness direction in the fluidized bed when these are flown, The relationship between the shear stress (Kgf / cm ^-2 ) and the flow velocity (cm / sec) at the position is shown.

From this figure, the shear stress on the wall surface is 1.
6 (Kgf / cm ^-2 ).

FIG. 1 (c) shows that 10%
When the low-viscosity resin is in a layered form on the surface in a composition to which a low-viscosity resin (weight ratio) is added and mixed, the shear stress on the wall surface is a very low value of 0.8 (Kgf / cm ^-2 ). It turns out that it becomes. Based on these facts, the shear stress on the wall surface of the die is present at a position 1/3 inward from the surface when 10% of the low-viscosity resin is added and mixed compared to the composition of the 100% high-viscosity resin. Then (2.4-1.
6) /2.4×100=33% at the surface position, (2.
4−0.8) /2.4×100=67%, that is, about 30 to
It can be seen that it is reduced by 70%.

On the other hand, the elongational viscosity related to the drawdown is occupied by each resin in the cross section (perpendicular to the flow direction) because the low-viscosity resin is interposed in the vertical direction (flow direction) in a layered manner. Since it is proportional to the area, the following equation holds.

When a low-viscosity resin having a viscosity ratio (ηL / ηH) = 1/8 is added and mixed in 10%, and a layer is formed, (ηH × 0.9 + ηL × 0.10) × 1 / ηH × 1
00 = 91.25% and the elongational viscosity remains only about 9% lower.

From the above, it is presumed that the shear stress that causes melt fracture can be reduced by about 30 to 70%, and the drawdown can be maintained at about 90% of the elongational viscosity, which is a factor preventing the drawdown.

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

In the examples and comparative examples, various evaluations of raw materials and hollow molded articles (bottles) were performed as follows.

1) Raw Materials (1) Melt Flow Rate (MFR) Melt flow rate is measured according to JIS K7210. (2) Density The density was 23 ± 0,0 according to the method D of JIS K7112.
Measure at a temperature of 1 ° C.

2) Blow moldability (1) Parison opening After the blow molding machine has been continuously operated without any abnormality, the parison extruded from the die is cut by an electric heat cutter, and the cut parison opening state. Is observed with the naked eye.

A state in which the cut end of the opening is not inclined or closed is defined as “no abnormality” (◎), and the opening is slightly inclined or closed. A state where there was no influence was defined as “substantially no abnormality” (○), and a state where the cut was clearly inclined or closed was defined as “abnormal” (×). (2) Bottle stopper After the blow molding machine has been in continuous operation without any abnormalities, a blow-molded bottle is randomly sampled with air blown into the extruded and cut parison opening through an air blowing nozzle. Then, the state of the plug portion of the bottle is visually observed.

A state in which the plug is not deformed or its inner surface is not damaged is defined as “No abnormality” (（), and a state in which deformation or damage that is difficult to determine with the naked eye is generated is “Almost abnormal”. "No" (O), and a state where deformation or damage was apparently caused by a nozzle or the like was "Abnormal" (X). (3) Drawdown After the blow molding machine has been in a continuous operation state without any abnormality, the extrusion state of the parison is visually observed without touching the parison extruded from the die.

A state in which the parison has been extended by its own weight within a predetermined length within a predetermined tolerance within a predetermined time is defined as "no abnormality".
(◎), the state extended within the permissible limit of the predetermined length range was defined as “substantially no abnormality” (○), and the state extended out of the predetermined length range was defined as “abnormal” (×). (4) After the melt fracture blow molding machine has been in a continuous operation state without any abnormality, the parison extruded from the die is collected without touching the surface, and the surface state of the parison is visually observed. Compare with limit sample.

A state in which skin roughness is hardly observed is defined as “no abnormality” (◎), a state in which skin roughness is slightly generated is defined as “substantially normal” (（), and a state in which skin roughness is apparently defined is “abnormal”. (X).

2) Characteristics of the bottle (1) Thickness distribution After the blow molding machine has been continuously operated without any abnormality, blow-molded bottles are randomly sampled, and a sharp blade is used to vertically extend from the plug to the bottom. Then, the cut port is marked with a predetermined interval from the plug portion to the bottom portion and marked, and the thickness of the marked portion is measured with a micrometer or a dial gauge.

A state in which most of the measured values are within the allowable range is “abnormal” (◎), and a state in which a plurality of measured values are near the allowable limit is “substantially normal” (○). The state where most of the results were out of the limit was regarded as "abnormal" (x). (2) Surface gloss After the blow molding machine has been in a continuous operation state without any abnormality, blow-molded bottles are randomly sampled, and the surface gloss of the bottle is visually observed and compared with the limit sample.

A state in which almost the entire surface of the bottle has a predetermined gloss is defined as “no abnormality” (）), and a state in which a part of the bottle slightly loses gloss (matte) is defined as “almost abnormal”. "No" (O), and a state where the gloss was lost (matte) on most surfaces of the bottle was "Abnormal" (X). (3) Transparency After the blow molding machine has been in a continuous operation state without any abnormality, blow-molded bottles are randomly sampled, and the transparent state of the bottle is visually observed and compared with the limit sample.

A state in which almost all parts of the bottle are transparent is designated as “no abnormality” (◎), and a state in which a part of the bottle has a slightly cloudy part is designated as “substantially normal” (○). The state where there was a cloudy spot on the majority surface of the bottle was defined as "abnormal" (x). (4) Flexibility After the blow molding machine has been in a continuous operation state without any abnormality, the blow-molded bottle is randomly sampled, and the bottle is folded so as to be rolled up from the bottom side toward the plug portion. Observe.

A material that can be folded so as to be easily wrapped is designated as "extremely flexible" (A), and a material that can be folded so as to be easily wrapped is designated as "flexible" (O) and is easily involved. Those that could not be folded like this were designated as "no flexibility" (x). (5) Drop strength After the blow molding machine has been in continuous operation without any abnormality, blow-molded bottles are randomly sampled, filled with a predetermined amount of water, sealed with a stopper, and the bottle is heated at a temperature of 5 ° C. And then drop it repeatedly from a predetermined height (8 m), and observe the state with the naked eye.

A sample which was not damaged by repeated dropping five times was rated "No abnormality" (A), and a sample which was dropped three or four times and was not damaged was rated "Almost no defect" (O).
"Abnormal" if damaged by repeated drops
(X).

[0055]

Example 1 MFR obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst was 2.2 g /
Metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KF26 manufactured by Nippon Polychem Co., Ltd.]
1] 80% by weight, metallocene polyethylene having an MFR of 16.5 g / min and a density of 0.898 g / cm ³ [trade name: Kernel KS560 manufactured by Nippon Polychem Co., Ltd.] 20
% By weight and a tumbler type blender, and then using a blow molding machine equipped with an extruder having a diameter of 55 mm,
A parison is extruded under molding conditions of a screw rotation speed of 20 rpm and a resin temperature of 160 ° C.
mm, a body diameter of 52 mm, a body thickness of 0.85 mm, and a capacity of 400 ml are molded. The air blowing nozzle is made of ordinary stainless steel.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured by the above-described methods.

The results are shown in Table 1. As shown, the parison was formed without cutting off, although the cut end was slightly inclined. The bottle was blow-molded well, except that the plug was slightly damaged to the extent that it would not pose a practical problem, and had good appearance and flexibility such as wall thickness distribution and surface gloss.
Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0058]

Example 2 The same two metallocene polyethylenes as in Example 1 were mixed in a tumbler-type blender, and then mixed with a caliber of 5 mm.
Using a blow molding machine equipped with a 5 mm extruder, a parison was extruded under the same molding conditions as in Example 1.
The same bottle is molded. However, an air blowing nozzle having an outer peripheral surface coated with Teflon is used.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and the bottle are evaluated and measured by the methods described above.

The results are shown in Table 1. As shown, the parison was formed without cutting off, although the cut was slightly inclined. Further, the bottle was blow-molded well without damage to the plug portion and the like, and the appearance and flexibility such as wall thickness distribution and surface gloss were also good. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0061]

Example 3 MFR obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst was 3.5 g /
Metallocene polyethylene having a density of 0.905 g / cm ³ for 10 minutes [trade name: Kernel K, manufactured by Nippon Polychem Co., Ltd.]
F370] 90% by weight, metallocene polyethylene having an MFR of 16.5 g / min and a density of 0.898 g / cm ³ [trade name: Kernel KS56, manufactured by Nippon Polychem Co., Ltd.]
0] by 10% by weight in a tumbler-type blender, and then using the same blow molding machine as in Example 2 (air blowing nozzle having an outer peripheral surface coated with Teflon), and molding conditions similar to those in Example 1. To extrude a parison to form a bottle similar to that of Example 1.

When the parison is cut by the electric heat cutter, the die head on which the parison hangs is moved upward in accordance with the operation of the electric heat cutter in order to extend the cutting point of the parison in the axial direction.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured by the methods described above.

The results are shown in Table 1. The parison was formed without sharkskin or drawdown, and without cutting or tilting the cut. In addition, the bottle is blow-molded well without damage to the plug, etc.
The appearance such as surface gloss and flexibility were also good. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0065]

Example 4 The same two types of metallocene polyethylene as in Example 3 were mixed in a tumbler type blender, and the same blow molding machine (stainless steel air blowing nozzle) as in Example 1 was used. The parison is extruded under the same molding conditions, and the same bottle as in Example 1 is molded.

When the parison is cut in the same manner as in the third embodiment, the cut portion of the parison is extended in the axial direction.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured by the methods described above.

The results are shown in Table 1. As shown, the parison was formed without the cut end being inclined or clogged. In addition, the bottle was blow-molded well, except for a slight damage to the plug, which was not a problem in practical use.
The appearance such as surface gloss and flexibility were also good. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0069]

Example 5 MFR obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst was 2.2 g /
Metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KF2 manufactured by Nippon Polychem Co., Ltd.]
61] 95% by weight and 5% by weight of a metallocene polyethylene having an MFR of 16.5 g / min and a density of 0.898 g / cm ³ [trade name: Kernel KS560 manufactured by Nippon Polychem Co., Ltd.] were mixed in a tumbler-type blender. Thereafter, using the same blow molding machine as in Example 2 (air blowing nozzle having an outer peripheral surface coated with Teflon), Example 1 was used.
A parison is extruded under the same molding conditions as in Example 1 to form a bottle as in Example 1.

In the same manner as in the third embodiment, the parison is cut in the axial direction at the time of parison cutting.

The wall thickness distribution, surface gloss, transparency, flexibility and drop strength of the parison blow moldability and bottle are evaluated and measured by the above-described methods.

The results are shown in Table 2. As shown, the parison was slightly sharkskin-like, had no drawdown, and was formed without inclining or closing the cut. In addition, the bottle was blow-molded well without any damage on the plug portion. Although the wall thickness distribution was good, the appearance such as surface gloss and transparency was slightly inferior, but practically no problem. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0073]

Example 6 MFR obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst was 2.2 g /
Metallocene polyethylene having a density of 0.898 g / cm ³ for 10 minutes [trade name: Kernel KF manufactured by Nippon Polychem Co., Ltd.]
261] 90% by weight and an MFR of 11.0 g / 10
And 10% by weight of a metallocene polyethylene having a density of 0.898 g / cm ^{3 in} a tumbler-type blender, and then using the same blow molding machine as in Example 2 (air blowing nozzle having an outer peripheral surface coated with Teflon). Then, the parison is extruded under the same molding conditions as in Example 1, and the same bottle as in Example 1 is molded.

In the same manner as in the third embodiment, the parison is cut in the axial direction at the time of parison cutting.

A metallocene polyethylene having an MFR of 11.0 g / 10 min and a density of 0.898 g / cm ³ has a MFR of
FR 2.2 g / 10 min, density 0.898 g / cm ³
Metallocene polyethylene [trade name: Kernel KF261 manufactured by Nippon Polychem Co., Ltd.] and MFR of 16.5 g / min.
Metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KS56, manufactured by Nippon Polychem Co., Ltd.]
0] is melted and mixed at a ratio of 20:80, sufficiently homogenized, and re-pelletized. The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated.

The results are shown in Table 2. The parison was molded without any drawdowns, with slight signs of sharkskin, without any inclines or blockages in the cut. In addition, the bottle was blow-molded well without damage to the plug portion. Although the wall thickness distribution was good, the appearance such as surface gloss and transparency was slightly inferior, but practically no problem. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0077]

Example 7 MFR obtained by copolymerizing ethylene and high α-olefin with a metallocene catalyst was 3.5 g /
Metallocene polyethylene having a density of 0.905 g / cm ³ for 10 minutes [trade name: Kernel KF manufactured by Nippon Polychem Co., Ltd.]
370] 65% by weight and an MFR of 16.5 g / 10 min.
Metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KS560, manufactured by Nippon Polychem Co., Ltd.]
After mixing with 35% by weight in a tumbler-type blender, the parison was molded under the same molding conditions as in Example 1 using the same blow molding machine as in Example 2 (air blowing nozzle with an outer peripheral surface coated with Teflon). Is extruded to form a bottle similar to that in Example 1. At the time of parison cutting, the cut portion of the parison is extended in the axial direction as in the third embodiment.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated.

The results are shown in Table 2. As for the parison, there was some drawdown, and the cut was slightly inclined, but was formed without closing. The bottle was well formed except that the inner surface of the plug was not so dent as to cause no practical problem. Although some of the thickness distributions were close to the permissible limit, the appearance and flexibility such as surface gloss and transparency were good.
Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0080]

Example 8 A material obtained by mixing the same two metallocene polyethylenes as in Example 1 with a tumbler-type blender and MF
A high-pressure low-density polyethylene having a R of 0.5 g / 10 min and a density of 0.922 g / cm ³ [trade name: Novatec LD ZE41 manufactured by Nippon Polychem Co., Ltd.]
Using a two-layer blow molding machine (air blowing nozzle with Teflon coating on the outer peripheral surface) equipped with an extruder with a diameter of 5 mm and an extruder with a diameter of 30 mm, the 55 mm extruder has a screw rotation speed of 16 rpm, and the 30 mm mm extruder has a screw. Under the molding conditions of a rotation speed of 22 rpm and a resin temperature of 163 ° C., the thickness ratio of the high-pressure low-density polyethylene layer to the metallocene polyethylene layer is 20:80 with the high-pressure low-density polyethylene layer being the outer layer and the metallocene polyethylene layer being the inner layer. Is extruded to form a bottle similar to that of Example 1.

At the time of parison cutting, the parison cutting portion is extended in the axial direction. Parison blow moldability and bottle thickness distribution, surface gloss, transparency, flexibility,
Evaluate the drop strength.

The results are shown in Table 2. As shown, the parison was formed without drawdown or inclining or clogging of the cut. In addition, the bottle was blow-molded well without damage to the plug portion. Although the wall thickness distribution was good, the appearance and flexibility such as surface gloss and transparency were slightly inferior, but there was no practical problem. Further, the bottle was filled with a predetermined amount of water and dropped from a predetermined height, but the number of times until breakage was slightly lower, but there was no problem in practicality.

[0083]

Comparative Example 1 Metallocene polyethylene used in Example 1 [trade name: Kernel KF2 manufactured by Nippon Polychem Co., Ltd.]
61] as the raw material and the same molding machine as in Example 2 (air blowing nozzle with Teflon-coated outer peripheral surface)
, A parison is extruded under the same molding conditions as in Example 1, and a bottle similar to that of Example 1 is molded. At the time of parison cutting, the cut portion of the parison is extended in the axial direction as in the third embodiment.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured by the methods described above. The results are shown in Table 3. Both the parison and the bottle were molded without any damage. However, the bottle had a rough surface, lacked luster, and lost transparency.

As is clear from this, metallocene polyethylene having a low MFR has a small drawdown during parison molding and can be molded into a bottle. However, melt fracture occurs during parison molding and the surface becomes rough and sharkskin-like. Thus, the molded bottle is inferior in surface gloss and transparency and does not become a commercially valuable bottle. The bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0086]

Comparative Example 2 Metallocene polyethylene used in Example 1 [trade name: Kernel KS56, manufactured by Nippon Polychem Co., Ltd.]
0] as a raw material, using the same molding machine as in Example 2 (air blowing nozzle having an outer peripheral surface coated with Teflon), screw rotation speed 20 rpm, resin temperature 13
The parison is extruded under the molding conditions of 5 ° C., and the same bottle as in Example 1 is molded.

In the same manner as in Example 3, at the time of parison cutting, the parison cutting portion is extended in the axial direction.

The results are shown in Table 3. As shown in Table 3, when the parison was molded, the drawdown was so severe that the bottle could not be molded even though the resin temperature was lowered.

[0089]

Comparative Example 3 Metallocene polyethylene used in Example 3 [trade name: Kernel KF3 manufactured by Nippon Polychem Co., Ltd.]
70] of 60% by weight, and the MFR used in Example 8 was 0.1%.
After mixing with a high pressure method low density polyethylene having a density of 0.922 g / cm3 (trade name: Novatec LD ZE41 manufactured by Nippon Polychem Co., Ltd.) having a density of 0.922 g / cm3 in a tumbler type blender, the same as in Example 2. Molding machine (air blow nozzle with Teflon coating on outer surface)
Using screw speed 20 rpm, resin temperature 1
A parison is extruded under molding conditions of 55 ° C., and a bottle similar to that of Example 1 is molded.

In the same manner as in the third embodiment, when the parison is cut, the cut portion of the parison is extended in the axial direction.

The parison blow moldability and the bottle are evaluated and measured for thickness distribution, surface gloss, transparency, flexibility, and drop strength by the methods described above.

The results are shown in Table 3. Although both the parison and the bottle were formed without any damage, the bottle was cloudy and inferior in transparency. Further, the bottle was filled with a predetermined amount of water and dropped, and was damaged.

[0093]

Comparative Example 4 MFR used in Example 1 was 2.2 g / 1
0 min, metallocene polyethylene having a density of 0.898 g / cm ^ 3 [trade name: Kernel KF2 manufactured by Nippon Polychem Co., Ltd.]
61] 55% by weight, metallocene polyethylene having an MFR of 16.5 g / min and a density of 0.898 g / cm ³ [trade name: Kernel KS560, manufactured by Nippon Polychem Co., Ltd.] 45% by weight of metallocene polyethylene in a tumbler type blender. After mixing, a parison was extruded under the same molding conditions as in Example 1 using the same molding machine as in Example 2 (air blown norm with an outer peripheral surface coated with Teflon), and the same bottle as in Example 1 was used. Is molded.

In the same manner as in the third embodiment, the parison is cut in the axial direction at the time of parison cutting.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured.

The results are shown in Table 3. The parison had a drawdown, the cut was inclined, and sometimes closed,
In some cases, molding was not possible. Although the bottle had good appearance and flexibility such as surface gloss and transparency, a dent was found on the inner surface of the plug, and there was a large variation in the wall thickness distribution of the body, which poses a practical problem. The bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0097]

Comparative Example 5 The MFR used in Example 1 was 16.5 g /
10 minutes, density 0.898g / cm ^ThreeMetallocene poly
Ethylene [Product name: Kernel K, manufactured by Japan Polychem Co., Ltd.]
S560] 30% by weight and MFR of 5.0 g / 10 min.
0.898g / cm density^ThreeMetallocene polyethylene
70% by weight was mixed with a tumbler type blender.
Then, the same molding machine as in Example 2 (the outer peripheral surface was
Example of using air-blown nor
The parison was extruded under the same molding conditions as in Example 1.
Mold bottles.

In the same manner as in Example 3, when parison is cut, the parison cutting portion is extended in the axial direction.

An MFR of 5.0 g / 10 min and a density of 0.
898 g / cm ³ of metallocene polyethylene has a MFR of
Is 2.2 g / 10 min and the density is 0.898 g / cm ³ metallocene polyethylene [trade name, manufactured by Nippon Polychem Co., Ltd .:
Kernel KF261] and a metallocene polyethylene having an MFR of 16.5 g / min and a density of 0.898 g / cm ³ [trade name: Kernel KS560, manufactured by Nippon Polychem Co., Ltd.] are melted and mixed at a ratio of 60 to 40 to be uniform. And repelletized.

The wall thickness distribution, surface gloss, transparency, flexibility and drop strength of the parison blow moldability and bottle are evaluated and measured.

The results are shown in Table 4. The parison had a drawdown, the cut was inclined, and sometimes closed,
In some cases, molding was not possible. Although the bottle had good appearance and flexibility such as surface gloss and transparency, a dent was found on the inner surface of the plug, and there was a large variation in the wall thickness distribution of the body, which poses a practical problem. The bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0102]

Comparative Example 6 MFR used in Example 1 was 2.2 g / 1
0 minute, metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KF, manufactured by Nippon Polychem Co., Ltd.]
261] 80% by weight, metallocene polyethylene having an MFR of 8.2 g / 10 min and a density of 0.898 g / cm ³
0% by weight and mixed in a tumbler type blender.
A parison is extruded under the same molding conditions as in Example 3 using the same molding machine as in Example 2 (air-blown air with an outer peripheral surface coated with Teflon), and a bottle as in Example 1 is molded.

At the time of parison cutting, the parison cutting portion is extended in the axial direction. MFR 8.2g / 10
Metallocene polyethylene having a MFR of 2.2 g / 10 min and a density of 0.898 g / cm ^3.
g / cm ³ metallocene polyethylene [trade name: Kernel KF261 manufactured by Nippon Polychem Co., Ltd.] and MFR of 1
A metallocene polyethylene having a density of 0.898 g / cm ³ and a density of 0.898 g / cm ³ (made by Nippon Polychem Co., Ltd .: Kernel KS560) was melted and mixed at a ratio of 35 to 65, homogenized, and re-pelletized. Use things.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow moldability and bottle are evaluated and measured.

The results are shown in Table 4. The parison was formed without cutting or tilting of the cut and without drawdown, but sharkskin was generated. In addition, the bottle is good without damage to the spout,
It becomes sharkskin and has poor surface gloss and transparency and does not have commercial value. The bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

[0106]

Comparative Example 7: MFR 4.5 g / 10 min, density 0.8
A parison was extruded from a 98 g / cm ³ metallocene polyethylene under the same molding conditions as in Example 3 using the same molding machine as in Example 2 (air blown nor with an outer peripheral surface coated with Teflon). The same bottle is molded.

A metallocene polyethylene having an MFR of 4.5 g / 10 min and a density of 0.898 g / cm ³ is
MFR 2.2 g / 10 min, density 0.898 g / cm
³ metallocene polyethylene [trade name: Kernel KF261 manufactured by Nippon Polychem Co., Ltd.] and MFR of 16.5 g /
Metallocene polyethylene having a density of 0.898 g / cm ³ [trade name: Kernel KS5, manufactured by Nippon Polychem Co., Ltd.]
60] is melted and mixed at a ratio of 65:35 to be homogenized and repelletized.

Further, at the time of parison cutting, the cutting point of the parison is extended in the axial direction.

The wall thickness distribution, surface gloss, transparency, flexibility, and drop strength of the parison blow mold and the bottle are evaluated and measured.

[0110] The results are shown in Table 4. The parison was formed with no cut or slanted cut and without drawdown, but sharkskin was generated. In addition, the bottle is good without damage to the spout,
It becomes sharkskin and has poor surface gloss and transparency and does not have commercial value. The bottle was filled with a predetermined amount of water and dropped from a predetermined height, but was not damaged.

Table 1 shows the results of the above Examples and Comparative Examples.
It is shown in Table 4. ◎ Table 1 ◎ Table 2 ◎ Table 3 ◎ Table 4

[0112]

The hollow molded article according to the present invention is excellent in wall thickness distribution, surface gloss, transparency, flexibility and drop strength, and has good blow moldability.

In particular, since it can be easily folded and reduced in volume by making use of its flexibility, it is suitable for use as an environmentally friendly hollow molded article, for example, for filling bottles and containers for detergents such as hair washing, clothing and tableware, and for filling foods and bottles for food. is there.

In addition, a medical infusion bottle or an ice pillow filled with ice or a frozen liquid for cooling and heating is utilized by taking advantage of the properties such as flexibility and impact strength at low temperatures by utilizing the high extraction resistance and flexibility of the metallocene-based polyethylene resin. It is extremely useful as a hollow molded article having excellent suitability such as a container for use.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a comparative calculation example of a velocity distribution and a shear stress distribution of a simplified multilayer structure model in a case where a high-viscosity resin and a low-viscosity resin exist in layers.

Continued on the front page (72) Inventor Katsutoshi Saeki 1-17-22 Kita-Kasai, Edogawa-ku, Tokyo F-term in Tahara Co., Ltd. (reference) 4F208 AA04A AA04C AR17 AR18 LA01 LA04 LA07 LA08 LB01 LG01 LG04 LG22 LH19 LJ09 LN07 4J002 BB051 BB052 GG01

Claims (4)

[Claims] Claims: 1. A copolymer having a melt flow rate of 4 g / 10 min or less obtained by copolymerizing ethylene and a high α-olefin with a metallocene catalyst, and copolymerizing ethylene and a high α-olefin with a metallocene catalyst. And a polyethylene having a melt flow rate of 10 g / 10 min or more obtained by blow molding a parison provided with at least one layer of a composition containing the composition in a weight ratio of 98: 2 to 60:40. Hollow molded products. 2. A blow molding method for a hollow molded product in which a parison extruded from an extruder is suspended and held in a molding die, cut by an electric heat cutter, and air is blown into the parison from an air blowing nozzle. Flow rate obtained by copolymerizing ethylene and high α-olefin with a metallocene-based catalyst and polyethylene having a melt flow rate of 4 g / 10 min or less obtained by copolymerizing ethylene and high α-olefin with a metal-based catalyst Is 10g
98: 2 to 6
A composition containing the composition in a weight ratio of 0:40 was mixed with an extruder.
A blow molding method for a hollow molded article, comprising: fusing and extruding a parison having at least one layer of the composition, and blowing air into the parison. 3. When cutting a parison with an electric heat cutter,
3. The blow molding method for a hollow molded product according to claim 2, wherein at least a cutting point of the parison is extended in an axial direction. 4. The parison opening according to claim 2, wherein an air blowing nozzle having a lubricity treated on the outer peripheral surface of the nozzle is inserted into the parison opening, and air is blown into the parison from the nozzle. A blow molding method for hollow molded products.