JP2014189705A - Polyethylene composition for flexible thin-wall container - Google Patents

Polyethylene composition for flexible thin-wall container Download PDF

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JP2014189705A
JP2014189705A JP2013068028A JP2013068028A JP2014189705A JP 2014189705 A JP2014189705 A JP 2014189705A JP 2013068028 A JP2013068028 A JP 2013068028A JP 2013068028 A JP2013068028 A JP 2013068028A JP 2014189705 A JP2014189705 A JP 2014189705A
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polyethylene composition
component
polyethylene
mfr
density
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Keiichi Yoshimoto
圭一 吉本
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Japan Polyethylene Corp
日本ポリエチレン株式会社
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Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene composition for flexible thin-wall containers excellent in moldability, flexibility, impact resistance and transparency and a container obtained with it.SOLUTION: A polyethylene composition for flexible thin-wall containers contains (C) 0.01-0.5 pt. wt. of a slip agent to 100 pts. wt. of a polyethylene (I) and has properties (a) to (e): (a) a melt flow rate(MFR) at a temperature of 190°C and a load of 2.16 kg is 5-100 g/10 min; (b) a density is 0.890-0.920 g/cm; (c) a flexural modulus of elasticity is 30-200 MPa; (d) a ratio of the tensile impact strength in the flow direction(MD) of the molten resin to the tensile impact strength in the direction(TD) perpendicular to the flow of the molten resin, MD strength/TD strength, is 0.10-1.00 for a molded test specimen of a thickness of 1 mm or smaller; and (e) a friction coefficient is 0.40 or smaller.

Description

  The present invention relates to a polyethylene composition for a soft thin-walled container and a container comprising the same. More specifically, the present invention is excellent in moldability (high fluidity, releasability), flexibility, impact resistance, transparency, and can be easily crushed. The present invention relates to a polyethylene composition for a soft thin-walled container that can store liquids such as soft drinks and milk drinks, dairy products, and the like, and a container made thereof.

Conventionally, high-density polyethylene by single-stage polymerization having a melt flow rate (MFR) of about 40 g / 10 minutes has been used for a polyethylene cup-shaped container formed by injection molding.
Due to the increasing demand for shortening the molding cycle in recent years to increase production efficiency, Patent Document 1 discloses that rigidity, impact resistance, low odor, food obtained by sequentially polymerizing or blending two types of polyethylene. A polyethylene for thin-walled injection-molded containers has been disclosed that is excellent in safety and has moldability with high fluidity that can be injection-molded at low temperatures.
Patent Document 2 discloses a polyethylene for thin-walled containers, in which the balance between rigidity and impact resistance at low temperature is improved, which was insufficient with the invention of Patent Document 1 described above.
However, the cup-type containers using the high-density polyethylene of the invention still have insufficient impact resistance, and since the cup-type containers using them are opaque, the contents cannot be seen from the outside. Since the rigidity is high, it is difficult to be deformed, and it is difficult to reduce the volume at the time of disposal.

Patent Document 3 has one or more elution curve peaks obtained by MFR of 5 to 150 g / 10 min, density of 0.915 g / cm 3 or less, and temperature rising elution fractionation (TREF). An injection molding resin and an injection molding resin composition that satisfy the requirements such as 85 ° C. or less, have excellent transparency, excellent strength at normal temperature and low temperature, and good balance between strength and rigidity. Is disclosed.
In Patent Document 4, a composition comprising an ethylene / α-olefin copolymer that satisfies specific requirements and another ethylene polymer has transparency, flexibility, heat resistance, impact resistance, and heat seal characteristics. It is disclosed that it has excellent anti-blocking properties.

Patent Document 5 discloses a polyethylene composition consisting of 98 to 20% by weight of an ethylene / α-olefin copolymer and 2 to 80% by weight of another ethylene polymer that satisfies specific requirements, and a container comprising the same as a constituent material. However, it is disclosed that it is excellent in transparency, impact resistance, heat seal properties, and anti-blocking properties, and is suitable as a constituent material for sheets, containers, and the like, in which the resin components are less eluted into the contents.
In Patent Document 6, (A) density is 0.88 to 0.97 g / cm 3 , (B) MFR is 0.01 to 100 g / 10 min, (C) molecular weight distribution is 1.5 to 4.0, (D) Elongation viscosity measurement at constant strain rate-Elongation viscosity rise (strain hardening) occurs in the extension viscosity curve, (E) A certain amount of high temperature elution by TREF measurement is satisfied. A polyethylene composition having 99 to 10% by weight of an ethylene (co) polymer and 1 to 90% by weight of a high-pressure radical process polyethylene has a molding processability, mechanical properties such as strength, impact resistance and rigidity, heat resistance, It is disclosed that optical characteristics and the like are good.
Patent Document 7 discloses (A) an ethylene-α-olefin copolymer 51 to 99% by weight produced from a metallocene catalyst having a specific range of density and melt flow rate and a specific range of density and melt flow rate ( B) Polyethylene composition comprising 49 to 1% by weight of high-pressure low-density polyethylene, n-hexane extraction amount of 5% by weight or less and xylene extraction amount of 11% by weight or less, and for injection molding However, it is disclosed that it can be used for parts that come in direct contact with foods that have excellent mechanical properties such as crack resistance and impact resistance, low extractables to solvent, and good injection molding processability. Has been.

  However, the compositions of these inventions are not necessarily sufficient in terms of fluidity at the time of molding, release properties from the mold, etc., and good moldability (high flow, high spiral flow), softness (low rigidity, Crushing), low friction (releasability), improved strength reduction due to orientation (isotropy, improved tensile impact strength, impact resistance), transparency (low haze), etc. There is still a need.

JP 2006-160987 A JP 2011-153171 A JP-A-6-313072 JP-A-8-302085 Japanese Patent Laid-Open No. 9-31263 JP 2000-212341 A JP 2002-275322 A

  An object of the present invention is to provide a polyethylene composition excellent in moldability, flexibility, impact resistance and transparency and a container obtained therefrom in view of the state of the prior art. In particular, it is an object to provide a material suitable for a flexible and transparent cup-shaped container molded by injection molding and a container obtained therefrom.

  As a result of intensive studies to solve the problems of the conventional techniques as described above, the polyethylene composition having specific physical properties is excellent in moldability, flexibility, impact resistance, and transparency. The inventors have reached the knowledge that it can be suitably used for a soft thin-walled container, and have completed the present invention.

According to 1st invention of this invention, it contains 0.01-0.5 weight part of slip agents (C) with respect to 100 weight part of polyethylene (I), and the following (a)-(e The polyethylene composition for soft thin-walled containers is provided.
(A) Melt flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kg is 5 to 100 g / 10 min. (B) The density is 0.890 to 0.920 g / cm 3 (c) Flexural modulus (D) When a specimen having a thickness of 1 mm or less is molded, the tensile impact strength in the flow direction (MD) of the molten resin and the tensile impact in the direction (TD) perpendicular to the flow of the molten resin Ratio to strength (MD strength / TD strength) is 0.10 to 1.00 (e) Friction coefficient is 0.40 or less

According to a second aspect of the present invention, there is provided the polyethylene composition for a soft thin-walled container according to the first aspect, further having the following property (f).
(F) The spiral flow at 190 ° C., injection pressure 75 MPa, thickness 2 mm is 40 to 70 cm.

According to the third invention of the present invention, in the first or second invention, the polyethylene (I) contains 50 to 95% by weight of the following component (A) and 5 to 50% by weight of the component (B). A polyethylene composition for a soft thin-walled container is provided.
Component (A): Polymerized using a metallocene catalyst having a melt flow rate (MFR) of 1.0 to 100 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, and a density of 0.865 to 0.920 g / cm 3. Ethylene polymer Component (B): Metallocene catalyst having a melt flow rate (MFR) of 6.0 to 100 g / 10 min at a temperature of 190 ° C., a load of 2.16 kg, and a density of 0.895 to 0.925 g / cm 3 Ethylene polymer polymerized without using

  According to a fourth invention of the present invention, there is provided a polyethylene composition for a soft thin-walled container characterized in that, in the third invention, the component (B) is an ethylene polymer polymerized by a high pressure method. The

  According to a fifth aspect of the present invention, in the third aspect, the component (B) is an ethylene polymer polymerized using a Ziegler-Natta catalyst. Things are provided.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the slip agent (C) is an unsaturated fatty acid amide and / or a saturated fatty acid amide. A polyethylene composition is provided.

  According to a seventh aspect of the present invention, there is provided a polyethylene composition for a soft thin-walled container, wherein the slip agent (C) is erucic acid amide in any one of the first to sixth aspects. .

  According to the eighth invention of the present invention, in any one of the third to seventh inventions, the component (A) has a plurality of peaks of the elution temperature-elution curve by the continuous temperature rising elution fractionation method (TREF). Provided is a polyethylene composition for soft thin-walled containers, which is an ethylene / α-olefin copolymer.

  According to the ninth aspect of the present invention, there is provided a soft thin-walled container obtained by injection molding the polyethylene composition of any one of the first to eighth aspects.

According to the present invention, it is possible to produce a polyethylene composition that is excellent in moldability, flexibility, impact resistance, and transparency and can be suitably used for an injection molded container.
That is, according to the present invention, moldability (high flow, high spiral flow), low friction (releasability), softness (low rigidity, crushability), improvement in strength reduction due to orientation (isotropic, To provide a composition and a molded product that are excellent in balance such as improvement in tensile impact strength, impact resistance) and transparency (low haze), especially in terms of fluidity during molding and releasability from a mold. Can do. A container using such a polyethylene composition is excellent in flexibility, impact resistance, and contents visibility, and can be easily reduced in volume at the time of disposal.

Hereinafter, the present invention will be described in detail.
The polyethylene composition for flexible thin-walled containers of the present invention (hereinafter also referred to as “the composition of the present invention”) has a slip agent (C) of 0.01 to 0.5 parts per 100 parts by weight of polyethylene (I). A composition containing parts by weight. In the present invention, containing the slip agent (C) is important for moldability and mold release from the mold. The slip agent (C) will be described later.

1. Polyethylene (I)
In order for polyethylene (I) to have the properties (a) to (e) described later, etc., it is preferable to contain the following component (A) and component (B).
Component (A): Polymerized using a metallocene catalyst having a melt flow rate (MFR) of 1.0 to 100 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, and a density of 0.865 to 0.920 g / cm 3. Ethylene polymer Component (B): Metallocene catalyst having a melt flow rate (MFR) of 6.0 to 100 g / 10 min at a temperature of 190 ° C., a load of 2.16 kg, and a density of 0.895 to 0.925 g / cm 3 Ethylene polymer polymerized without using

  Polyethylene (I) is preferably 50 to 95% by weight, more preferably 55 to 90% by weight, and still more preferably 60% by weight of component (A) with respect to 100% by weight of the total amount of components (A) and (B). -85 weight%, Preferably a component (B) is contained 5-50 weight%, More preferably, it is 10-45 weight%, More preferably, it contains 15-40 weight%. When the content ratio of the component (A) is less than 50% by weight (when the content ratio of the component (B) exceeds 50% by weight), the impact resistance is lowered, and the content ratio of the component (A) is 95% by weight. (If the content of the component (B) is less than 5% by weight), the fluidity tends to decrease and the moldability tends to deteriorate. Hereinafter, the component (A) and the component (B) will be described.

2. Component (A): Ethylene Polymer The ethylene polymer of the component (A) that can be used in the composition of the present invention has a melt flow rate (MFR) of 1.0 to 190 at a temperature of 190 ° C. and a load of 2.16 kg. It is an ethylene polymer polymerized using a metallocene catalyst having a density of 100 g / 10 min and a density of 0.865 to 0.920 g / cm 3 .

(1) Production method of component (A) The polymerization catalyst of the ethylene-based polymer of component (A) is a metallocene catalyst called a complex formed by coordination of a ligand having a cyclopentadiene skeleton to a transition metal and a promoter. Are combined. By polymerizing the component (A) using a metallocene catalyst, a specific orientation can be exhibited when the obtained composition is injection-molded, and the tensile direction of the molten resin in the flow direction (MD) during molding The ratio (MD strength / TD strength) of the impact strength and the tensile impact strength in the perpendicular direction (TD) with MD can be set to a specific range.
As a specific metallocene catalyst, a complex catalyst in which a ligand having a cyclopentadiene skeleton such as methylcyclopentadiene, dimethylcyclopentadiene or indene is coordinated to a transition metal containing Ti, Zr, Hf, lanthanide series, etc. In addition, as a co-catalyst, a combination of an organometallic compound of elements of Group 1 to Group 3 of the periodic table such as aluminoxane, and a supported type in which these complex catalysts are supported on a carrier such as silica can be cited. It is done.

The ethylene-based polymer polymerization catalyst of component (A) is a single-site catalyst (known publication: Japanese Patent Laid-Open No. 58-19309, as long as it satisfies the range of the characteristics of the polymer defined in the present invention. 59-95292, 59-23011, 60-35006, 60-35007, 60-35008, 60-35209, 61-130314, JP 3-163088), or a combination of other catalysts.
Further, for example, an ethylene polymer polymerized by a single site catalyst described in JP-A-8-302805 and JP-A-9-31263 is an elution temperature by continuous temperature rising elution fractionation (TREF)- It is an ethylene / α-olefin copolymer having a plurality of peaks in the elution curve, and such an ethylene / α-olefin copolymer having a plurality of TREF peaks is cited as preferred in the present invention because of its excellent heat resistance. It is done.

  The ethylene-based polymer of component (A) is a homopolymer of ethylene, or ethylene and an α-olefin having 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1 It can be obtained by copolymerization with pentene, 1-octene or the like. Also, copolymerization with a diene for the purpose of modification is possible. Examples of the diene compound used at this time include butadiene, 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene, and the like. The comonomer content during the polymerization can be arbitrarily selected. For example, in the case of copolymerization of ethylene and an α-olefin having 3 to 12 carbon atoms, an ethylene / α-olefin copolymer is used. The α-olefin content is 0 to 40 mol%, preferably 0 to 30 mol%.

The component (A) can be produced by a production process such as a gas phase polymerization method, a solution polymerization method, or a slurry polymerization method, and the gas phase polymerization method is preferable. Among the polymerization conditions of the ethylene polymer, the polymerization temperature can be selected from the range of 0 to 300 ° C. The polymerization pressure can be selected from the range of atmospheric pressure to about 100 kg / cm 2 .

(2) MFR of component (A)
The ethylene-based polymer of component (A) has an MFR of 1.0 to 100 g / 10 minutes, preferably 5.0 to 90 g / 10 minutes, more preferably 10 to 50 g / 10 minutes. When the MFR is less than 1.0 g / 10 minutes, the viscosity of the resin becomes high and the fluidity is insufficient at the time of molding, so that a sufficient flow length cannot be obtained. On the other hand, when MFR exceeds 100 g / 10 minutes, impact resistance tends to be lowered. Here, MFR is a value measured according to JIS K6922-2.
The MFR of component (A) can be adjusted by the ethylene polymerization temperature, the use of a chain transfer agent, etc., and a desired product can be obtained. That is, by increasing the polymerization temperature of ethylene and α-olefin, the MFR can be increased as a result of decreasing the molecular weight, and as the result of increasing the molecular weight by decreasing the polymerization temperature, the MFR can be decreased. Can do. Further, in the copolymerization reaction of ethylene and α-olefin, the MFR can be increased as a result of decreasing the molecular weight by increasing the amount of coexisting hydrogen (amount of chain transfer agent). By reducing the amount of chain transfer agent, the MFR can be reduced as a result of increasing the molecular weight.

(3) Density of component (A) The ethylene-based polymer of component (A) has a density of 0.865 to 0.920 g / cm 3 , preferably 0.865 to 0.915 g / cm 3 , more preferably 0. 865 to 0.910 g / cm 3 . The lower limit of the density of polyethylene is usually 0.865. On the other hand, when the density exceeds 0.920 g / cm 3 , the rigidity of the molded product increases and the flexibility of the container tends to deteriorate. Here, the density is a value measured according to JIS K6922-2.
The density of the ethylene polymer (A) can be obtained by changing the kind and amount of the comonomer copolymerized with ethylene.

3. Ingredient (B)
The ethylene polymer of component (B) that can be used in the composition of the present invention is an ethylene polymer polymerized without using a metallocene catalyst, and has a melt flow rate at a temperature of 190 ° C. and a load of 2.16 kg ( MFR) is an ethylene polymer having a density of 6.0 to 100 g / 10 min and a density of 0.895 to 0.925 g / cm 3 .

(1) Production method of component (B) The ethylene polymer of component (B) is a homopolymer of ethylene or an α-olefin having 3 to 12 carbon atoms such as propylene, 1-butene, 1-pentene. , 1-hexene, 4-methyl-1-pentene, 1-octene and the like. Also, copolymerization with a diene for the purpose of modification is possible. Examples of the diene compound used at this time include butadiene, 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene, and the like. The comonomer content during the polymerization can be arbitrarily selected. For example, in the case of copolymerization of ethylene and an α-olefin having 3 to 12 carbon atoms, an ethylene / α-olefin copolymer is used. The α-olefin content is 0 to 40 mol%, preferably 0 to 30 mol%.

Component (B) is an ethylene polymer polymerized without using a metallocene catalyst. For example, an ethylene polymer obtained by homopolymerizing ethylene by a high-pressure radical polymerization method or a copolymer of ethylene and another comonomer And a copolymer of ethylene and another comonomer obtained by copolymerizing ethylene and another comonomer using a Ziegler-Natta catalyst.
By using an ethylene polymer polymerized without using a metallocene catalyst as the component (B), the component (A) alone, which is an ethylene polymer polymerized using a metallocene catalyst, tends to be insufficient. The fluidity at the time of molding can be improved, and the properties (a) to (e) of the composition of the present invention can be satisfied simultaneously.

(2) MFR of component (B)
The MFR of the ethylene polymer of the component (B) is in the range of 6.0 to 100 g / 10 minutes, preferably 10 to 80 g / 10 minutes, and more preferably 15 to 60 g / 10 minutes. If the MFR is less than 6.0 g / 10 min, the moldability of the polyethylene composition becomes poor, and if it exceeds 100 g / 10 min, the mechanical strength such as impact resistance and tensile strength of the polyethylene composition is lowered. Here, MFR is a value measured according to JIS K6922-2.
The MFR of the ethylene-based polymer of component (B) can be adjusted by the ethylene polymerization temperature, the use of a chain transfer agent, etc., and a desired product can be obtained. That is, by increasing the polymerization temperature of ethylene and α-olefin, the MFR can be increased as a result of decreasing the molecular weight, and as the result of increasing the molecular weight by decreasing the polymerization temperature, the MFR can be decreased. Can do. Further, in the copolymerization reaction of ethylene and α-olefin, the MFR can be increased as a result of decreasing the molecular weight by increasing the amount of coexisting hydrogen (amount of chain transfer agent). By reducing the amount of chain transfer agent, the MFR can be reduced as a result of increasing the molecular weight.

(3) Density of component (B) The density of the ethylene-based polymer of component (B) is 0.895 to 0.925 g / cm 3 , preferably 0.898 to 0.924 g / cm 3 , more preferably 0. The range is from 900 to 0.922 g / cm 3 . When the density is less than 0.895 g / cm 3, the rigidity of the resulting thin-walled container is insufficient and the container is easily deformed during molding, whereas when the density exceeds 0.925 g / cm 3 , The rigidity tends to increase and the flexibility of the container tends to deteriorate. Here, the density is a value measured according to JIS K6922-2.
The desired density can be obtained by changing the density of the ethylene polymer (B) depending on the type and amount of the comonomer copolymerized with ethylene.

4). Slip agent (C)
The slip agent (C) in the present invention is added to polyethylene (I) to impart slip properties, and specific compounds include fatty acid amides.
Examples of fatty acid amides include unsaturated fatty acid amides and / or saturated fatty acid amides. Examples of unsaturated fatty acid amides include oleic acid amide, linoleic acid amide, erucic acid amide, gadoleic acid amide, and saturated fatty acid amides include palmitic acid. Examples thereof include amides, stearic acid amides, and behenic acid amides. Among them, C18-C22 unsaturated fatty acid amides, specifically erucic acid amides, oleic acid amides, and gadrenic acid amides are preferable because they impart good slip properties.
Fatty acid amide is kneaded and mixed in the resin, and when the resin is melt-molded, it partially transfers from the inside of the resin to the resin surface, and it is thought that a bimolecular layer of fatty acid amide is formed on and around the resin surface. The slip property, i.e., the friction coefficient, is reduced. Therefore, in order to obtain excellent initial slip properties, it is necessary to quickly form a bimolecular layer on the resin surface.

It is preferable to add 0.01-0.5 weight part of slip agents (C) of this invention with respect to 100 weight part of polyethylene (I). If the amount is less than 0.01 parts by weight, the desired moldability and slip properties will not be exhibited, and even if the amount exceeds 0.5 parts by weight, no further improvement in the effect can be expected. This may cause a phenomenon and deteriorate the appearance of the molded product.
When producing a composition containing the present slip agent (C), there is a method in which the present slip agent is mixed with polyethylene (I) together with other additives as necessary, and melt-kneaded and pelletized with an extruder. However, a master batch of the slip agent (C) may be produced in advance, mixed with polyethylene (I) so as to finally have the composition ratio of the present invention, and melt-kneaded and molded by an extruder.

5. Polyethylene composition for soft thin container The polyethylene composition of the present invention is characterized by having the following properties (a) to (e).
(A) Melt flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kg is 5 to 100 g / 10 min. (B) The density is 0.890 to 0.920 g / cm 3 (c) Flexural modulus (D) When a specimen having a thickness of 1 mm or less is molded, the tensile impact strength in the flow direction (MD) of the molten resin and the tensile impact in the direction (TD) perpendicular to the flow of the molten resin Ratio to strength (MD strength / TD strength) is 0.10 to 1.00 (e) Friction coefficient is 0.40 or less

Furthermore, the polyethylene composition of the present invention preferably has the following property (f).
(F) The spiral flow at 190 ° C., injection pressure 75 MPa, thickness 2 mm is 40 to 70 cm.

(1) Melt flow rate (MFR)
The polyethylene composition of the present invention has (a) a melt flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kg of 5 to 100 g / 10 min, preferably 10 to 80 g / 10 min, more preferably 15 to 70 g / min. 10 minutes.
When the MFR is less than 5 g / 10 minutes, it is difficult to obtain sufficient fluidity. On the other hand, when the MFR exceeds 100 g / 10 minutes, the impact resistance tends to decrease. Here, MFR is a value measured according to JIS K6922-2.
The MFR can be adjusted by changing the individual MFR of the components (A) and (B) or changing the blending ratio of the two components (A) and (B).

(2) Density The polyethylene composition of the present invention has (b) a density of 0.890 to 0.920 g / cm 3 , preferably 0.891 to 0.920 g / cm 3 , and more preferably 0.892 to 0.8. 915 g / cm 3 .
When the density is less than 0.890 g / cm 3 , the resulting thin-walled container has insufficient rigidity, whereas when the density exceeds 0.920 g / cm 3 , the impact resistance tends to decrease. Here, the density is a value measured according to JIS K6922-2.
The density can be adjusted by changing the individual densities of the components (A) and (B) or by changing the blending ratio of the two components (A) and (B).

(3) Flexural modulus The polyethylene composition of the present invention has (c) a flexural modulus of 30 to 200 MPa, preferably 32 to 180 MPa, more preferably 35 to 150 MPa.
When the flexural modulus is less than 30 MPa, the rigidity is insufficient and the container is insufficient. On the other hand, when the flexural modulus exceeds 200 MPa, it is difficult to easily crush. Here, the flexural modulus is a value measured in accordance with JIS K6922-2 by preparing a 10 × 80 × 4 mm test piece at 210 ° C. by injection molding.
In order to increase the flexural modulus, it can be adjusted by increasing the density of polyethylene or adding a rigid filler.

(4) Tensile impact strength The polyethylene composition of the present invention has (d) the tensile impact strength in the flow direction (MD) of the molten resin during molding and the tensile impact strength in the direction perpendicular to the flow of the molten resin (TD). The ratio (MD strength / TD strength) is 0.10 to 1.00, preferably 0.10 to 0.95, and more preferably 0.15 to 0.90.
The tensile impact strength in the flow direction (MD) of the molten resin during molding and the tensile impact strength in the vertical direction (TD) of the molten resin are as follows: set temperature 190 ° C., mold temperature 40 ° C., injection speed 50 mm / second, cooling time 10 A 120 × 120 × 1 mm flat plate is molded under the conditions of second and holding pressure switching position 5.5 mm, and the direction in which the length direction of the test piece becomes the flow direction (MD) of the molten resin at the time of molding is MD, the test piece The direction in which the length direction is perpendicular to the molten resin flow (TD) is TD, and the tensile impact tester is punched into the shape of the ASTM D1822-06 type S specimen in the MD and TD directions. Can be measured using. If the thickness of the injection plate exceeds 1 mm, the orientation of the resin is relaxed, and the strength balance between the flow direction (MD) and the flow direction (TD) of the thin container changes. Must be done with a thickness of.
If the ratio of the tensile impact strength in the flow direction (MD) of the molten resin during molding and the tensile impact strength in the direction perpendicular to the flow (TD) is out of the above range, the flow direction (MD) and flow of the thin container On the other hand, the strength balance in the vertical direction (TD) deteriorates, which is not preferable.

In general, polyethylene-based resin compositions used for polyethylene cup-type containers tend to be strongly oriented in the flow direction (MD) of the molten resin during molding, so that the tensile impact strength in the MD direction increases, The tensile impact strength in the direction perpendicular to the resin flow (TD) tends to decrease. Therefore, a polyethylene cup-shaped container molded with such a polyethylene-based resin composition tends to easily cause orientation cracks that run in the MD direction at the gate peripheral part of the cup bottom or the cup wall surface due to impact such as dropping. is there. On the other hand, when the composition of the present invention is used, the reason is not necessarily clear, but due to the expression of the unique orientation, the direction (TD) perpendicular to the tensile impact strength in the flow direction (MD) of the molten resin during molding. The tensile impact strength increases, and the ratio of the tensile impact strength in the flow direction (MD) of the molten resin during molding and the tensile impact strength in the direction perpendicular to the flow of the molten resin (MD) (MD strength / TD strength) is specified. It becomes the range. Therefore, by using the composition of the present invention, it is possible to mold a polyethylene cup-type container that is less likely to cause orientation cracking due to impact such as dropping.
The MD intensity / TD intensity can be reduced by increasing the MFR of the component (B), increasing the ratio of the component (A) to the component (B), or the like.

(5) Friction coefficient The polyethylene composition of the present invention has (e) a friction coefficient of 0.40 or less, preferably 0.35 or less, more preferably 0.30 or less. The coefficient of friction referred to in the present invention is measured according to JIS K-7125: 1997. However, as an alternative method, double-sided measurement is performed with a tripogear muse 94i manufactured by Shinto Kagaku using a 120 × 120 × 2 mm flat plate molded at 190 ° C. using an IS-150 injection molding machine manufactured by Toshiba Machine. It is also possible.
When the coefficient of friction exceeds 0.40, the slipperiness is poor, and the mold release becomes difficult when molded. In order to make this friction coefficient 0.40 or less, it can be adjusted by adding an appropriate amount of slip agent (C).

(6) Vicat softening temperature The polyethylene composition of the present invention preferably has a Vicat softening temperature measured according to JIS K-7206 (1999) of 40 ° C or higher, more preferably 80 ° C or higher. If the Vicat softening temperature is high, the heat resistance of the container is improved. The Vicat softening point can be increased by increasing the density of the polyethylene composition or by using the component (A) having a plurality of peaks due to TREF.

(7) Spiral Flow The polyethylene composition of the present invention preferably has (f) a spiral flow of 40 to 70 cm at 190 ° C., an injection pressure of 75 MPa, and a thickness of 2 mm.
The spiral flow has a spiral flow length obtained by using a mold having an Archimedes spiral flow path of 190 ° C., a runner side gate width of 4 mm, a cavity side gate width of 5 mm, a width of 10 mm, a thickness of 2 mm, and a longest flow path length of 2000 mm. It is obtained by measuring.
In order to set the spiral flow within the above range, the MFR of the polyethylene composition can be adjusted within the above range.

(8) Molding method of polyethylene composition for soft thin-wall container The polyethylene composition of the present invention is pelletized by mechanical melt mixing with a pelletizer, homogenizer, etc. according to a conventional method, and then molded by various molding machines. It can be set as a molded article.

  In addition, the polyethylene composition for flexible containers obtained by the above-described method is not limited to the performance, and other conventional olefin polymers and rubbers, antioxidants, ultraviolet absorbers, light, etc. Known additives such as stabilizers, lubricants, antistatic agents, antifogging agents, antiblocking agents, processing aids, color pigments, crosslinking agents, foaming agents, inorganic or organic fillers, flame retardants, and the like can be blended. .

  As additives, for example, one or more antioxidants (phenolic, phosphorus, sulfur), lubricants, antistatic agents, light stabilizers, ultraviolet absorbers, and the like can be used in combination as appropriate. Fillers (agents) include calcium carbonate, talc, metal powder (aluminum, copper, iron, lead, etc.), silica, diatomaceous earth, alumina, gypsum, mica, clay, asbestos, graphite, carbon black, titanium oxide, etc. Among them, it is preferable to use calcium carbonate, talc, mica, and the like. In either case, the polyethylene composition of the present invention can be blended with various additives as necessary, and kneaded with a kneading extruder, a Banbury mixer, or the like to obtain a molding material. However, when used for food containers, it is preferable to use additives as little as possible because the influence on the taste and smell of the container itself and the taste and smell of the contents is reduced.

The polyethylene composition of the present invention is mainly molded by an injection molding method, a compression molding method, or the like, and various molded products such as a container body are preferably obtained by an injection molding method.
Since the polyethylene composition of the present invention satisfies various properties, it is excellent in moldability, high fluidity, odor, impact resistance, food safety, rigidity, etc., and excellent in heat resistance. Therefore, it is suitable for applications such as containers that require such characteristics, and particularly suitable for applications that require flexibility.
In particular, the polyethylene composition of the present invention is optimally used for containers such as soft cups. The polyethylene composition of the present invention is suitably used in a container having a thickness of usually 1 mm or less.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention will not be restrict | limited by these Examples, unless it deviates from the summary. In addition, the physical property of the polyethylene composition used by the Example and the comparative example was measured and evaluated with the following method.
In addition, the elution temperature-elution curve by the continuous temperature rising elution fractionation method (TREF) was performed according to the method described in the Example of Unexamined-Japanese-Patent No. 9-31263.
(1) MFR: Measured according to JIS-K6922-2.
(2) Density: Measured according to JIS-K6922-1,2.
(3) Bending elastic modulus: Molded at 210 ° C. with a JIS-K7152-1 type A mold by injection molding to produce a 10 × 80 × 4 mm test piece, and measured according to JIS-K6922-2 did.
(4) Tensile impact strength in the flow direction (MD) of molten resin and tensile impact strength in the direction perpendicular to MD (TD) when a test piece having a thickness of 1 mm or less is molded ROBOSHOT S-2000i 100B injection molding manufactured by FANUC Using a machine, a 120 × 120 × 1 mm flat plate was molded under the conditions of a set temperature of 190 ° C., a mold temperature of 40 ° C., an injection speed of 50 mm / second, a cooling time of 10 seconds, and a holding pressure switching position of 5.5 mm. The direction in which the length direction of the molten resin flows in the flow direction (MD) during molding is MD, and the direction in which the length direction of the test piece is perpendicular to the MD (TD) is TD. It was punched into the shape of ASTM D1822-06 type S test piece and measured with a T-30 hammer using a Tensile Impact Tester manufactured by Toyo Seiki Seisakusho Co., Ltd.
(5) Friction coefficient: measured in accordance with JIS K-7125: 1997.
(6) Vicat softening temperature: measured in accordance with JIS K-7206 (1999).
(7) Spiral flow length: ROBOSHOT S-2000i 100B injection molding machine manufactured by FANUC, set temperature 190 ° C., injection speed 10 mm / second, injection time 5 seconds, cooling time 10 seconds, holding pressure switching position 7 mm, injection The spiral flow length was measured using a mold having an Archimedes spiral flow path with a runner side gate width of 4 mm, a cavity side gate width of 5 mm, a width of 10 mm, a thickness of 2 mm, and a longest flow path length of 2000 mm under a pressure of 75 MPa.
(8) Hayes Using a ROBOSHOT S-2000i 100B injection molding machine manufactured by FANUC, under the conditions of a set temperature of 190 ° C., a mold temperature of 40 ° C., an injection speed of 50 mm / second, a cooling time of 20 seconds, and a holding pressure switching position of 9.0 mm. A 120 × 120 × 2 mm flat plate was molded, and haze was measured using a HAZEMETER HM-150 manufactured by Murakami Color Research Laboratory.
(9) Evaluation method of fluidity / releasability and container flexibility Fluidity: A spiral flow length within the scope of the present invention was marked with ◯, and one that did not reach the scope of the present invention was marked with x.
Releasability: FANUC ROBOSHOT S-2000i 100B injection molding machine, flange 71φ under the conditions of set temperature 210 ° C, mold temperature 20 ° C, injection speed 150mm / sec, cooling time 15sec, holding pressure switching position 10mm A cup-type container was molded with a cup-type mold having a side thickness of 0.8 mm, a bottom thickness of 1 mm, and a height of 110 mm. When the molded cup-shaped container was taken out from the mold, the one that was able to be removed smoothly was marked with ○, and the one that was hugged to the mold core and could not be removed smoothly was marked with ×.
Container flexibility: For cup-shaped containers molded under the above conditions, those that could be easily crushed by hand while holding the side were marked with ○, and those that were hard and could not be easily crushed were marked with ×. .

The following polyethylene was used as a component (A).
A-1: An ethylene / 1-hexene copolymer polymerized using a metallocene catalyst and having an MFR of 30 g / 10 min and a density of 0.880 g / cm 3 A-2: Implementation of JP-A-9-31263 An ethylene / 1-hexene copolymer having an MFR of 27 g / 10 min and a density of 0.911 g / cm 3 polymerized using a single site metallocene catalyst polymerized by the single site catalyst described in the examples A -3: an ethylene / 1-hexene copolymer polymerized using a metallocene catalyst and having an MFR of 3 g / 10 min and a density of 0.920 g / cm 3 A-4: MFR polymerized using a metallocene catalyst Is an ethylene / 1-hexene copolymer having a density of 0.8 g / 10 min and a density of 0.900 g / cm 3

The following polyethylene was used as a component (B).
B-1: Ethylene polymer polymerized by high pressure method, MFR 45 g / 10 min, density 0.921 g / cm 3 B-2: MFR polymerized by slurry method using Ziegler-Natta catalyst There 40 g / 10 min, a density of 0.960 g / cm 3 ethylene polymer B-3: is polymerized by high pressure process, MFR is 2 g / 10 min, ethylene polymer having a density of 0.924 g / cm 3 B-4: Ethylene polymer polymerized by slurry method using Ziegler-Natta catalyst, MFR 30 g / 10 min, density 0.923 g / cm 3 B-5: MFR polymerized by high pressure method Is an ethylene polymer having a density of 1.0 g / 10 min and a density of 0.919 g / cm 3

  As component (C), erucic acid amide (trade name Neutron-S manufactured by Nippon Seika Co., Ltd.) was used.

(Examples 1-4)
The components (A), (B), and (C) shown in Table 1 were mixed with V.I. After blending using a USV50-28 type extruder and casting with a pelletizer, the physical properties were evaluated. As shown in Table 1, the obtained polyethylene composition was a material excellent in injection moldability (high fluidity, releasability), impact resistance, flexibility, and transparency.

(Comparative Examples 1-5)
The components (A), (B), and (C) shown in Table 1 were mixed with V.I. After blending using a USV50-28 type extruder and casting with a pelletizer, the physical properties were evaluated. As shown in Table 1, the obtained polyethylene composition was a material inferior in any of injection moldability (high fluidity, releasability), impact resistance, flexibility, and transparency.

  The polyethylene composition for a soft thin-walled container according to the present invention has good injection moldability (high fluidity, releasability), impact resistance, flexibility and transparency, so that liquids such as soft drinks and milk drinks and milk It is highly usable in soft thin containers that can store products and the like, especially cup-type containers.

Claims (9)

  1. A soft material characterized by containing 0.01 to 0.5 parts by weight of a slip agent (C) and 100 parts by weight of polyethylene (I) and having the following properties (a) to (e): Polyethylene composition for thin-walled containers.
    (A) Melt flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kg is 5 to 100 g / 10 min. (B) The density is 0.890 to 0.920 g / cm 3 (c) Flexural modulus (D) When a specimen having a thickness of 1 mm or less is molded, the tensile impact strength in the flow direction (MD) of the molten resin and the tensile impact in the direction (TD) perpendicular to the flow of the molten resin Ratio to strength (MD strength / TD strength) is 0.10 to 1.00 (e) Friction coefficient is 0.40 or less
  2. Furthermore, it has the property of following (f), The polyethylene composition for soft thin-walled containers of Claim 1 characterized by the above-mentioned.
    (F) The spiral flow at 190 ° C., injection pressure 75 MPa, thickness 2 mm is 40 to 70 cm.
  3. The polyethylene composition for soft thin-walled containers according to claim 1 or 2, wherein the polyethylene (I) contains the following component (A) 50 to 95% by weight and component (B) 5 to 50% by weight. .
    Component (A): Polymerized using a metallocene catalyst having a melt flow rate (MFR) of 1.0 to 100 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, and a density of 0.865 to 0.920 g / cm 3. Ethylene polymer Component (B): Metallocene catalyst having a melt flow rate (MFR) of 6.0 to 100 g / 10 min at a temperature of 190 ° C., a load of 2.16 kg, and a density of 0.895 to 0.925 g / cm 3 Ethylene polymer polymerized without using
  4.   The polyethylene composition for soft thin-walled containers according to claim 3, wherein the component (B) is an ethylene polymer polymerized by a high-pressure method.
  5.   The polyethylene composition for a soft thin-walled container according to claim 3, wherein the component (B) is an ethylene polymer polymerized using a Ziegler-Natta catalyst.
  6.   The polyethylene composition for soft thin containers according to any one of claims 1 to 5, wherein the slip agent (C) is an unsaturated fatty acid amide and / or a saturated fatty acid amide.
  7.   The polyethylene composition for soft thin-walled containers according to any one of claims 1 to 6, wherein the slip agent (C) is erucic acid amide.
  8.   The component (A) is an ethylene / α-olefin copolymer having a plurality of elution temperature-elution curve peaks determined by a continuous temperature rising elution fractionation method (TREF). The polyethylene composition for soft thin-walled containers according to any one of the above.
  9.   A soft thin-walled container obtained by injection-molding the polyethylene composition according to any one of claims 1 to 8.
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JPH0959442A (en) * 1995-08-25 1997-03-04 Nippon Petrochem Co Ltd Film and sealant
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JP2004277744A (en) * 2004-04-09 2004-10-07 Japan Polyolefins Co Ltd Film and sealant
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JPH06313072A (en) * 1993-03-02 1994-11-08 Mitsubishi Petrochem Co Ltd Resin for injection molding and resin composition for injection molding
JPH0959442A (en) * 1995-08-25 1997-03-04 Nippon Petrochem Co Ltd Film and sealant
JPH10219044A (en) * 1997-02-12 1998-08-18 Chisso Corp Polyolefin resin composition for vessel
JP2001288315A (en) * 2000-04-04 2001-10-16 Japan Polyolefins Co Ltd Resin composition for forming film
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