JP7186111B2 - polyethylene resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyethylene resin composition containing a polyethylene resin and a specific liquid crystal polymer.

Polyethylene resins are used in a wide range of applications, such as various films, sheets, fibers, injection molded products, wire coatings, and containers, due to their excellent economic efficiency, flexibility, and chemical resistance.

In particular, lids for food and beverage containers and soft drink bottles are required to be excellent in moldability, light weight, and slipperiness, and to shorten the molding cycle to improve production efficiency. , the demand for polyethylene resin with low melting point is increasing.

For example, a bottle cap made of a polyethylene resin composition having a specific melt flow rate and fluidity index has been proposed (Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-300357

However, polyethylene resin does not have sufficient mechanical strength such as rigidity and toughness, and there is a risk that the threaded portion may be deformed during the core die-cutting process during cap molding or during screw tightening during use.

In addition, recently, it has become common to sell tea and coffee beverages in a state where they have been heated by a heater. ing. However, polyethylene resins are not suitable for heating containers because of their poor heat resistance.

Furthermore, since polyethylene resins are inferior in gas barrier properties, there is a possibility that the contents of the container may deteriorate.

An object of the present invention is to provide a polyethylene resin composition which is superior in heat resistance and mechanical strength and has improved gas barrier properties as compared with a single polyethylene resin. In particular, it is an object of the present invention to provide a polyethylene resin composition which is excellent in heat resistance and mechanical strength and has improved gas barrier properties without impairing the flexibility inherent in polyethylene resins, especially bending deflection characteristics. .

The present inventors have made intensive studies on improving the heat resistance, mechanical strength and gas barrier properties of polyethylene resin. The inventors have found that it is possible to obtain a polyethylene resin composition having improved properties and exhibiting predetermined flexural deflection characteristics, and have completed the present invention.

That is, the present invention provides a polyethylene resin composition containing 100 parts by mass of a polyethylene resin and 0.1 to 100 parts by mass of a liquid crystal polymer having a crystal melting temperature of less than 210°C and having a bending deflection of 5 mm or more. .

INDUSTRIAL APPLICABILITY The polyethylene resin composition of the present invention is excellent in heat resistance, mechanical strength and gas barrier properties, and exhibits predetermined bending and deflection characteristics. be able to.

The polyethylene resin used in the present invention is not particularly limited, but examples thereof include low density polyethylene, linear low density polyethylene, high density polyethylene and the like. These may be used alone or in combination of two or more.

Among these, high-density polyethylene is preferable from the viewpoint of gas barrier properties of the obtained polyethylene resin composition.

The polyethylene resin used in the present invention is an ethylene polymer containing ethylene as a main raw material, and may be an ethylene homopolymer, or a mixture of ethylene and an α-olefin preferably having 3 to 20 carbon atoms. It may be a copolymer.

Examples of α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1 -octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-octadecene and 1-eicosene.

The α-olefins having 3 to 20 carbon atoms may be used alone or in combination of two or more.

Specific examples of copolymers of ethylene and α-olefins having 3 to 20 carbon atoms include ethylene-propylene copolymers, ethylene-1-butene copolymers, and ethylene-1-hexene copolymers. , ethylene-1-octene copolymer, ethylene-1-butene-1-hexene copolymer and ethylene-1-butene-1-octene copolymer.

The copolymer of ethylene and α-olefin may be a random copolymer or a block copolymer.

The polyethylene resin used in the present invention may be, for example, a single ethylene polymer polymerized in a single polymerization tank, or a mixture of two or more ethylene polymers. The mixture can be obtained by a method of melt-kneading using a single-screw or multi-screw extruder or the like, or a method of multi-stage polymerization in two or more polymerization tanks under different conditions.

In the copolymer of ethylene and α-olefin, the content of structural units provided by α-olefin is 5 mol% or less in the copolymer from the viewpoint of thermal stability of the obtained polyethylene resin composition. preferably 2 mol % or less.

That is, the content of ethylene structural units in the polyethylene resin is preferably 95 mol% or more, more preferably 98 mol% or more.

Although the method for producing the polyethylene resin used in the present invention is not particularly limited, it can be produced, for example, by the method shown below.

When the polyethylene resin is high-density polyethylene, for example, transition metal compounds such as titanium and zirconium, Ziegler catalysts composed of magnesium compounds, Phillips catalysts represented by chromium oxide catalysts, and transition metal compounds such as zirconium, hafnium, and titanium. Ethylene or ethylene and α- It is produced by (co)polymerizing with olefin.

Further, when the polyethylene resin is a linear low-density polyethylene, for example, using a catalyst such as the Ziegler catalyst, the Phillips catalyst, the metallocene catalyst, etc., a gas phase method, a solution method, a high pressure method, a slurry method, etc. The process is made by polymerizing ethylene, or by copolymerizing ethylene with α-olefins, and the like.

In addition, when the polyethylene resin is low-density polyethylene, for example, a radical generator such as peroxide is used as a polymerization initiator, and ethylene is polymerized by a process such as a high-pressure radical polymerization method, or ethylene and α-olefin are polymerized. Manufactured by copolymerization.

The above polymerization may be performed in a batch system or in a continuous system. Further, it may be a one-stage production method, or a multi-stage polymerization method in which production is carried out in multiple stages of two or more stages under different conditions.

Liquid crystalline polymers in the context of the present invention are liquid crystalline polyesters or liquid crystalline polyesteramides that form an anisotropic melt phase, referred to by those skilled in the art as thermotropic liquid crystalline polymers.

The nature of the anisotropic melt phase can be confirmed by conventional polarimetry using crossed polarizers. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing the sample placed on a Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. The liquid crystal polymer in the present invention is optically anisotropic, ie, it transmits light when examined between crossed polarizers. If the sample is optically anisotropic, polarized light is transmitted even at rest.

The crystalline melting temperature of the liquid crystal polymer in the present invention measured by a differential scanning calorimeter is less than 210°C, preferably 205°C or less, more preferably 200°C or less, still more preferably 195°C or less. The liquid crystal polymer in the invention preferably has a crystalline melting temperature of 150° C. or higher, more preferably 155° C. or higher, and still more preferably 160° C. or higher as measured by a differential scanning calorimeter.

When the crystalline melting temperature of the liquid crystal polymer is less than 210° C., the liquid crystal polymer is uniformly dispersed in the polyethylene resin matrix, making it easier to obtain excellent gas barrier properties and mechanical properties.

In the present specification and claims, the term "crystal melting temperature" refers to the crystal melting temperature measured at a heating rate of 20°C/min with a differential scanning calorimeter (hereinafter abbreviated as DSC). It is obtained from the peak temperature. More specifically, after observing the endothermic peak temperature (Tm1) observed when measuring the liquid crystal polymer sample under the temperature rising condition of 20 ° C./min from room temperature, 10 at a temperature 20 to 50 ° C higher than Tm1 After holding the sample for 20 minutes and then cooling the sample to room temperature under the condition of temperature decrease of 20°C/minute, the endothermic peak was measured again under the condition of temperature increase of 20°C/minute. It is the crystalline melting temperature of the polymer. As a measuring instrument, for example, Exstar6000 manufactured by Seiko Instruments Inc. can be used.

The repeating units constituting the liquid crystal polymer in the present invention include aromatic oxycarbonyl repeating units, aromatic dicarbonyl repeating units, aromatic dioxy repeating units, aromatic aminooxy repeating units, aromatic diamino repeating units, and aromatic aminocarbonyl repeating units. Examples include repeating units and combinations thereof.

Specific examples of monomers that give aromatic oxycarbonyl repeating units include, for example, aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 6-hydroxy-2 -naphthoic acid, 5-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 4'-hydroxyphenyl-4-benzoic acid, 3'-hydroxyphenyl-4-benzoic acid, 4'-hydroxyphenyl- 3-benzoic acid and the like, alkyl, alkoxy or halogen-substituted products thereof, and ester-forming derivatives such as acylates, ester derivatives and acid halides thereof. Among these, 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferred because the mechanical properties, heat resistance, crystal melting temperature and moldability of the resulting liquid crystal polymer can be easily adjusted to appropriate levels.

Specific examples of monomers that give aromatic dicarbonyl repeating units include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7 -naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-dicarboxybiphenyl, etc., alkyl, alkoxy or halogen-substituted products thereof, ester derivatives thereof, ester-forming derivatives such as acid halides, etc. mentioned. Among these, terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid are preferable because the mechanical properties, heat resistance, crystal melting temperature and moldability of the resulting liquid crystal polymer can be easily adjusted to appropriate levels.

Specific examples of monomers that give aromatic dioxy repeating units include aromatic diols such as hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1, 4-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl, 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl ether and the like, and alkyl, alkoxy or halogen substituted versions thereof; and ester-forming derivatives such as acylated products thereof. Among these, hydroquinone and 4,4'-dihydroxybiphenyl are preferable because the reactivity during polymerization and the mechanical properties, heat resistance, crystal melting temperature, and moldability of the resulting liquid crystal polymer can be easily adjusted to appropriate levels.

Monomers that provide aromatic aminooxy repeat units, aromatic diamino repeat units and aromatic aminocarbonyl repeat units include aromatic hydroxylamines, aromatic diamines and aromatic aminocarboxylic acids.

Copolymers that combine these repeating units may or may not form an anisotropic melt phase, depending on the composition and composition ratio of the monomers and the sequence distribution of each repeating unit in the copolymer. Although present, liquid crystalline polymers in the present invention are limited to copolymers that form anisotropic melt phases.

The liquid crystal polymer in the present invention may be a blend of two or more liquid crystal polymers.

As the liquid crystal polymer having a crystal melting temperature of less than 210° C. in the present invention, a wholly aromatic liquid crystal polyester comprising repeating units represented by formulas [I] to [VI] is suitable.

[Wherein, p, q, r, s, t and u each represent the composition ratio (mol%) of each repeating unit in the liquid crystal polymer and satisfy the following formula:
35≦p≦55,
25≤q≤45,
2≦r≦15,
0≦s≦5,
2≤t≤15,
0≤u≤5,
r≧s,
p+q+r+s+t+u=100. ]

In the wholly aromatic liquid crystal polyester suitably used in the present invention, the composition ratio p of the repeating unit represented by the formula [I] to the wholly aromatic liquid crystal polyester is preferably 35 to 55 mol%, more preferably 38 ~53 mol%. Also, the composition ratio q of the repeating unit represented by the formula [II] to the wholly aromatic liquid crystal polyester is preferably 25 to 45 mol %, more preferably 28 to 43 mol %.

In the wholly aromatic liquid crystal polyester preferably used in the present invention, the repeating units represented by the formulas [I] and [II] preferably satisfy the relationship p>q, and p/q is 1.0. It is more preferably 01 to 2.0, even more preferably 1.03 to 1.9, and particularly preferably 1.08 to 1.8.

Examples of monomers that give the repeating unit represented by formula [I] include 4-hydroxybenzoic acid and ester-forming derivatives such as acylates, ester derivatives and acid halides thereof.

Examples of monomers that give the repeating unit represented by formula [II] include 6-hydroxy-2-naphthoic acid and ester-forming derivatives such as acylates, ester derivatives and acid halides thereof.

Further, the wholly aromatic liquid crystalline polyester preferably used in the present invention contains an aromatic dioxy repeating unit represented by the formula [III]. The composition ratio r of the repeating unit represented by the formula [III] to the wholly aromatic liquid crystal polyester is preferably 2 to 15 mol %, more preferably 4 to 14 mol %.

Monomers that give the repeating unit represented by formula [III] include, for example, 4,4'-dihydroxybiphenyl and its ester-forming derivatives such as acylated products.

The wholly aromatic liquid crystalline polyester preferably used in the present invention may further contain a repeating unit represented by the formula [IV] as an aromatic dioxy repeating unit. The composition ratio s of the repeating unit represented by the formula [IV] to the wholly aromatic liquid crystal polyester is preferably 0 to 5 mol %, more preferably 0 to 4 mol %.

When the repeating unit represented by the formula [IV] is included as the aromatic dioxy repeating unit, the relationship r≧s is satisfied.

Monomers that provide the repeating unit represented by formula [IV] include, for example, hydroquinone and its ester-forming derivatives such as acylated products.

Further, the wholly aromatic liquid crystal polyester preferably used in the present invention contains an aromatic dicarbonyl repeating unit represented by the formula [V]. The composition ratio t of the repeating unit represented by formula [V] to the wholly aromatic liquid crystal polyester is preferably 2 to 15 mol %, more preferably 4 to 14 mol %.

Examples of monomers that give the repeating unit represented by formula [V] include 2,6-naphthalenedicarboxylic acid, its ester derivatives, and ester-forming derivatives such as acid halides.

The wholly aromatic liquid crystalline polyester preferably used in the present invention may further contain a repeating unit represented by the formula [VI] as an aromatic dicarbonyl repeating unit. The compositional ratio u of the repeating unit represented by the formula [VI] to the wholly aromatic liquid crystal polyester is preferably 0 to 5 mol %, more preferably 1 to 4 mol %.

When the repeating unit represented by the formula [VI] is included as the aromatic dicarbonyl repeating unit, it preferably satisfies the relationship of t≧u.

Examples of monomers that give the repeating unit represented by formula [VI] include terephthalic acid and isophthalic acid, their ester derivatives, and ester-forming derivatives such as acid halides. Among these, isophthalic acid is preferable because the crystal melting temperature can be adjusted to be lower.

That is, the repeating unit represented by the formula [VI] is preferably a repeating unit represented by the following formula [VII].

Note that p+q+r+s+t+u=100 in formulas [I] to [VI].

Also, it is preferable that r+s=t+u.

Two or more types of monomers may be used for each of the above monomers that provide the repeating units represented by formulas [I] to [VI].

The wholly aromatic liquid crystalline polyester preferably used in the present invention is composed of repeating units represented by formulas [I] to [VI], as described above, within a range that does not impair the object of the present invention. In addition to the main monomer that gives the repeating units represented by the general formulas [I] to [VI], other repeating units, that is, repeating units other than the repeating units represented by the general formulas [I] to [VI] A monomer that provides the unit may be copolymerized. Examples of monomers that provide other repeating units include aromatic hydroxycarboxylic acids, aromatic diols, aromatic dicarboxylic acids, aromatic hydroxydicarboxylic acids, aromatic hydroxylamines, aromatic diamines, aromatic aminocarboxylic acids, alicyclic Examples include tricarboxylic acids, aliphatic diols, alicyclic diols, aromatic mercaptocarboxylic acids, aromatic dithiols and aromatic mercaptophenols. It is preferable that the amount of these other repeating unit-providing monomers is 10 mol % or less of the total amount of the repeating unit-providing monomers represented by formulas [I] to [VI]. In the present invention, the liquid crystal polymer having a crystal melting temperature of less than 210° C. does not contain repeating units other than the repeating units represented by general formulas [I] to [VI], that is, formulas [I] to [VI]. A wholly aromatic liquid crystalline polyester composed of repeating units represented by is particularly preferable.

The method for producing the liquid crystal polymer in the present invention is not particularly limited, and a known polycondensation method for forming an ester bond or an amide bond between the above monomer components, such as a melt acidolysis method or a slurry polymerization method, can be used. .

The melt acidolysis process is a process in which the monomers are first heated to form a melt of reactants, followed by continuing the reaction to obtain a molten polymer. A vacuum may be applied to facilitate removal of volatiles (eg, acetic acid, water, etc.) that are by-produced in the final stages of condensation. This method is particularly suitable for use in the present invention.

Slurry polymerization is a process in which the reaction is carried out in the presence of a heat exchange fluid and the solid product is obtained in suspension in the heat exchange medium.

In both the melt acidolysis method and the slurry polymerization method, the polymerizable monomer component used in producing the liquid crystal polymer may be subjected to the reaction in a modified form obtained by esterifying the hydroxyl group, that is, in the form of a lower acyl ester. can. The lower acyl group preferably has 2 to 5 carbon atoms, more preferably 2 or 3 carbon atoms. Particularly preferred is a method of using an acetic acid ester of the monomer component for the reaction.

The lower acyl ester of the monomer may be acylated separately and synthesized in advance, or may be generated in the reaction system by adding an acylating agent such as acetic anhydride to the monomer during production of the liquid crystal polymer. .

A catalyst may optionally be used in either the melt acidolysis method or the slurry polymerization method.

Specific examples of catalysts include organic tin compounds such as dialkyltin oxide (e.g., dibutyltin oxide) and diaryltin oxide; metal oxides such as titanium dioxide; antimony compounds such as antimony trioxide; titanium compounds; alkali and alkaline earth metal salts of carboxylic acids (eg potassium acetate); gaseous acid catalysts such as Lewis acids (eg boron trifluoride), hydrogen halides (eg hydrogen chloride) and the like.

The proportion of the catalyst used is usually 10-1000 ppm, preferably 20-200 ppm, based on the total amount of the monomers.

The liquid crystal polymer obtained by such a polycondensation reaction is extracted from the polymerization reactor in a molten state, processed into pellets, flakes or powder, and blended with a polyethylene resin.

The content of the liquid crystal polymer in the polyethylene resin composition of the present invention is 0.1 to 100 parts by mass, preferably 1 to 80 parts by mass, more preferably 2 to 70 parts by mass, relative to 100 parts by mass of the polyethylene resin. parts, particularly preferably 3 to 50 parts by mass.

If the content of the liquid crystal polymer is less than 0.1 parts by mass, it tends to be difficult to sufficiently obtain the effect of improving heat resistance, mechanical strength, and gas barrier properties. , the flexibility of the polyethylene resin composition, especially the flexural flexibility, tends to be impaired.

The polyethylene resin composition of the present invention is characterized in that the liquid crystal polymer to be blended has a crystal melting temperature of less than 210 ° C., so that the liquid crystal polymer is uniformly dispersed in the polyethylene resin as the matrix resin, and melt-kneaded at a low temperature. Since blending is possible, thermal decomposition of the polyethylene resin is suppressed, and a resin composition having excellent heat resistance, mechanical strength and gas barrier properties can be obtained.
Therefore, a compatibilizer is not particularly necessary for blending, but a compatibilizer may be added for the purpose of further improving the compatibility between the polyethylene resin and the liquid crystal polymer. When adding a compatibilizer, the compatibilizer is preferably added in an amount of 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the polyethylene resin.

The polyethylene resin composition of the present invention may further contain inorganic or organic fillers as optional components.

Specific examples of inorganic or organic fillers that may be contained in the polyethylene resin composition of the present invention include glass fiber, silica alumina fiber, alumina fiber, carbon fiber, potassium titanate fiber, aluminum borate fiber, Aramid fibers, polyarylate fibers, talc, mica, graphite, wollastonite, dolomite, clay, glass flakes, glass beads, glass balloons, calcium carbonate, barium sulfate, titanium oxide, etc., are used alone. may be used, or two or more may be used in combination.

Among these, talc and glass fiber are preferred because they have an excellent balance between physical properties and cost.

Also, the inorganic or organic filler may be surface-treated. Examples of surface treatment methods include a method of adsorbing a surface treatment agent to the surface of a filler, a method of adding a surface treatment agent when kneading a polyethylene resin composition and a filler, and the like.

Surface treatment agents include reactive coupling agents (silane coupling agents, titanate coupling agents, borane coupling agents, etc.), lubricants (higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, fluorocarbon surfactants, etc.). agents, etc.).

The content of the inorganic or organic filler is preferably 1 to 150 parts by mass, more preferably 10 to 100 parts by mass, per 100 parts by mass of the total amount of the polyethylene resin and the liquid crystal polymer.

If the content of the inorganic or organic filler is less than 1 part by mass, it tends to be difficult to obtain the effect of improving mechanical strength such as rigidity and heat resistance of the polyethylene resin composition. tend to be less sexual.

In addition to the polyethylene resin and the liquid crystal polymer, other additives may be added to the polyethylene resin composition of the present invention as long as the objects of the present invention are not impaired.

Specific examples of other additives include lubricants (higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts (herein, higher fatty acids refer to those having 10 to 25 carbon atoms), etc.). , release modifiers (polysiloxane, fluorine resin, etc.), colorants (dyes, pigments, carbon black, etc.), flame retardants, antistatic agents, surfactants, nucleating agents (talc, organic phosphates, sorbitols, etc.) etc.), anti-blocking agents, antioxidants (phosphorus-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, etc.), weathering agents, heat stabilizers, neutralizers, and the like. These additives may be used alone or in combination of two or more.

The total amount of other additives in the polyethylene resin composition is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the total amount of the polyethylene resin and the liquid crystal polymer.

If the total amount of other additives is less than 0.01 part by mass, the function of the additive tends to be difficult to achieve, and if it exceeds 5 parts by mass, the thermal stability during molding of the polyethylene resin composition is reduced. tends to get worse.

In addition, among the above other additives, when using additives such as lubricants, release agents, anti-blocking agents, etc., they may be added during the preparation of the polyethylene resin composition, or during the molding process. You may make it adhere to the pellet surface of a polyethylene resin composition.

In addition to the polyethylene resin and the liquid crystal polymer, other resin components may be added to the polyethylene resin composition of the present invention as long as the object of the present invention is not impaired.

Specific examples of other resin components include, for example, polyamides, polyesters, polyacetals, polyphenylene ethers, modified products thereof, thermoplastic resins such as polysulfone, polyethersulfone, polyetherimide, and polyamideimide, phenolic resins, epoxy resins, and the like. Thermosetting resins such as resins and polyimide resins can be used. These resin components may be used alone or in combination of two or more.

When other resin components are contained, the content of the resin components is preferably 0.1 to 100 parts by mass, more preferably 0.1 to 80 parts by mass, based on 100 parts by mass of the total amount of the polyethylene resin and the liquid crystal polymer. preferable.

The polyethylene resin composition of the present invention is prepared by mixing a polyethylene resin, a liquid crystal polymer, and optionally a compatibilizer, an inorganic filler, other additives or other resin components, followed by a Banbury mixer, kneader, single-screw or twin-screw extrusion. It can be obtained by melt-kneading using a machine or the like under temperature conditions from the vicinity of the crystal melting temperature of the liquid crystal polymer to +50° C. of the crystal melting temperature.

Other additives and other resin components may be blended in advance with either the polyethylene resin or the liquid crystal polymer, or the polyethylene resin composition obtained by melt-kneading the polyethylene resin and the liquid crystal polymer is molded. It may be blended on occasion.

The deflection temperature under load (ASTM D648, load 1.82 MPa) of the polyethylene resin composition of the present invention obtained in this way was measured by a strip-shaped test piece (length 127 mm, width 12.7 mm, thickness 3.2 mm). , preferably 50°C or higher, more preferably 55 to 150°C, still more preferably 60 to 145°C.

The bending deflection amount of the polyethylene resin composition of the present invention is 5 mm or more, preferably 6 to 18 mm, more preferably 7 to 16 mm. When the bending deflection amount is less than 5 mm, the flexibility is lowered.

The bending strength of the polyethylene resin composition of the present invention is usually 6 MPa or more, preferably 7 to 50 MPa, more preferably 8 to 45 MPa.

The flexural modulus of the polyethylene resin composition of the present invention is usually 0.15 GPa or more, preferably 0.20 to 8 GPa, more preferably 0.25 to 6 GPa, and still more preferably 0.3 to 5 GPa.

The amount of bending deflection, bending strength, and bending elastic modulus are measured according to ISO 178 using a strip-shaped test piece having a length of 80.0 mm, a width of 10.0 mm, and a thickness of 4.0 mm.

The polyethylene resin composition of the present invention has an oxygen gas permeability according to JIS K7126-2 of usually 120 cm ³ /m ² ·24 h·atm or less, preferably 115 cm ³ /m ² ·24 h·atm or less, more preferably 105 cm ³ /m ² ·24 h·atm or less, more preferably 70 ^{cm 3} /m ² ·24 h·atm or less, particularly preferably 45 cm ³ /m ² ·24 h·atm or less, usually 0.01 cm ³ /m It exhibits an oxygen gas permeability of ² ·24 h·atm or more, and has the advantage of having a small oxygen gas permeability and excellent gas barrier properties.

The polyethylene resin composition of the present invention is melt-processed by a known molding method such as injection molding, extrusion molding, blow molding, injection compression molding, or compression molding to form a product such as a molded article, film, sheet, or fiber. be able to.

Molded articles composed of the polyethylene resin composition of the present invention include, for example, machine parts, electric/electronic parts, construction/civil engineering materials, household/office supplies, furniture parts and daily necessities, but particularly containers and A molded article as a lid member is useful.

The container composed of the polyethylene resin composition of the present invention can be used for rice products, processed foods, side dishes, pickles, Japanese confectionery, Western confectionery, juice, alcoholic beverages, food and drink such as seasonings, cosmetics such as hair styling products, foundations and perfumes, It can be used as a container for storing various contents such as hand washing detergents, face washing detergents, kitchen detergents, laundry detergents, shampoos, rinses and other detergents. Among these, it is particularly useful as a container for storing food and drink.

The lid member composed of the polyethylene resin composition of the present invention has a shape that can seal the mouth of a container or bottle containing drinking water or the like. caps and disc closers having a threaded portion, claw-like projection, annular projection, annular groove, etc.).

The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these.

Deflection temperature under load, flexural modulus, flexural strength, tensile strength, flexural deflection, oxygen gas permeability and crystal melting temperature in the examples were measured by the following methods.

(1) Deflection temperature under load (DTUL)
Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industry Co., Ltd.), a cylinder temperature of crystal melting temperature +20 to 40 ° C., a mold temperature of 70 ° C., length 127 mm, width 12.7 mm, thickness 3. A strip-shaped test piece of 2 mm was formed, and using this, measurement was performed according to ASTM D648 with a load of 1.82 MPa and a temperature increase rate of 2° C./min.

(2) Amount of bending deflection, bending strength and bending elastic modulus Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industry Co., Ltd.), the cylinder temperature was set to 250°C, the mold temperature was 40°C, and the length was 80.5°C. A strip-shaped test piece having a width of 0 mm, a width of 10.0 mm, and a thickness of 4.0 mm was formed, and the measurement was performed according to ISO 178 using this.

(3) Tensile modulus Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industry Co., Ltd.), injection molding is performed at a cylinder temperature of crystal melting temperature +20 to 40 ° C. and a mold temperature of 40 ° C., thickness 4.0 mm. A dumbbell test piece of type A1 was produced. Using INSTRON 5567 (Instron Japan Co., Ltd. universal testing machine), using a contact type extensometer with a gauge length of 25 mm, a test speed of 1 mm / min, a distance between chucks of 115 mm, ISO 527-1 Measured according to

(4) Oxygen gas permeability Using an injection molding machine (FE80S 12ASE type manufactured by Nissei Plastic Industry Co., Ltd.), a cylinder temperature of 250 ° C. and a mold temperature of 40 ° C. Mold a 100 mm square test piece with a thickness of 1.5 mm. Using this, an oxygen gas permeability test was conducted at a temperature of 20° C. and a humidity of 65% according to JIS K 7126-2. It means that the smaller the oxygen gas permeability, the better the gas barrier property.

(5) Crystal melting temperature Exstar 6000 manufactured by Seiko Instruments Inc. was used as a differential scanning calorimeter. Hold for 10 minutes at a temperature 20-50° C. higher than that. Next, the sample is cooled to room temperature under the condition of temperature decrease of 20°C/min, and the temperature of the peak top of the exothermic peak observed at that time is taken as the crystallization temperature (Tc) of the liquid crystal polymer, and then again at 20°C/min. An endothermic peak was observed when measuring under the temperature rising condition of , and the temperature showing the peak top was taken as the crystalline melting temperature (Tm) of the liquid crystal polymer.

In the examples, the following abbreviations represent the following compounds.
PE: polyethylene resin LCP: liquid crystal polymer POB: 4-hydroxybenzoic acid BON6: 6-hydroxy-2-naphthoic acid BP: 4,4'-dihydroxybiphenyl HQ: hydroquinone NDA: 2,6-naphthalenedicarboxylic acid IPA: isophthalic acid TPA: terephthalic acid

(polyethylene resin)
In the examples, the following were used as polyethylene resins.
PE: ULTZEX 1030L (made of prime polymer, linear low-density polyethylene, MFR 3.6 g/10 min, density 909 kg/m ³ )

(Synthesis of LCP)
[Synthesis Example 1 (LCP-1)]
POB: 386.0 g (43 mol %), BON6: 403.6 g (33 mol %), BP: 145.2 g (12 mol %), NDA : 126.0 g (9 mol%) and IPA: 32.4 g (3 mol%) were charged, and acetic anhydride was charged in an amount of 1.03 times the amount of hydroxyl groups (moles) of all monomers, and under the following conditions: Deacetic acid polymerization was performed.

In a nitrogen gas atmosphere, the temperature was raised from room temperature to 150° C. over 1 hour, and the same temperature was maintained for 30 minutes. Subsequently, the temperature was rapidly raised to 210° C. while distilling off the by-produced acetic acid, and the temperature was maintained for 30 minutes. Then, after raising the temperature to 340° C. over 4 hours, the pressure was reduced to 10 mmHg over 80 minutes. When a predetermined torque was exhibited, the polymerization reaction was terminated, the contents of the reaction vessel were taken out, and pellets of the liquid crystal polymer were obtained with a pulverizer. The amount of acetic acid distilled off during polymerization was almost the same as the theoretical value.

The crystal melting temperature of the resulting liquid crystal polymer (LCP-1) measured by DSC was 183°C.

[Synthesis Example 2 (LCP-2)]
POB: 323.2 g (36 mol %), BON6: 48.9 g (4 mol %), TPA: 323.9 g (30 mol %), BP : 169.4 g (14 mol %) and HQ: 114.5 g (16 mol %) were charged, and acetic anhydride was charged in an amount of 1.03 times the amount of hydroxyl groups (mol) of all monomers. Deacetic acid polymerization was carried out under the following conditions.

Under a nitrogen gas atmosphere, the temperature was raised from room temperature to 145° C. over 1 hour and maintained at 145° C. for 30 minutes. Next, the temperature was raised to 350° C. over 7 hours while acetic acid, which was produced as a by-product, was distilled off, and then the pressure was reduced to 5 mmHg over 80 minutes. When a predetermined torque was exhibited, the polymerization reaction was terminated, the contents were taken out from the reaction vessel, and pellets of the liquid crystal polymer were obtained with a pulverizer. The amount of acetic acid distilled off during polymerization was almost the same as the theoretical value. The crystalline melting temperature (Tm) of the obtained pellets was 335°C.

[Examples 1 to 3 and Comparative Examples 1 to 3]
Polyethylene resin, LCP-1 and LCP-2 are dry blended so that the contents shown in Table 1, and a twin-screw extruder (TEX-30 manufactured by Nippon Steel Co., Ltd.) is used to extrudate the cylinder at a temperature of 250 ° C. (LCP The mixture was melt-kneaded at 350° C. when using -2 to obtain pellets of the polyethylene resin composition.

These polyethylene resin compositions were measured for deflection temperature under load, bending deflection amount, bending strength, bending elastic modulus, tensile elastic modulus and oxygen gas permeability. Table 1 shows the results.

The polyethylene resin composition (Examples 1 to 3) in each example has a bending deflection amount of 7 to 14 mm, a bending strength of 8.5 to 25.2 MPa, a bending elastic modulus of 0.34 to 1.43 GPa, and a tensile elasticity. It had a modulus of 0.33 to 2.49 GPa, an oxygen gas permeability of 24 to 102 cm ³ /m ² ·24 h·atm, and was excellent in mechanical properties and gas barrier properties.

In contrast, the polyethylene resin composition of Comparative Example 1 containing no liquid crystal polymer was inferior in rigidity and gas barrier properties.

The polyethylene resin composition of Comparative Example 2, in which the content of the liquid crystal polymer exceeded 100 parts by mass, was inferior in bending deflection.

Further, in Comparative Example 3 using a liquid crystal polymer (LCP-2) having a high crystal melting temperature, a polyethylene resin composition could not be obtained due to thermal deterioration during melt-kneading.

本発明の好ましい態様は以下を包含する。
〔１〕ポリエチレン樹脂１００質量部、および
結晶融解温度が２１０℃未満である液晶ポリマー０．１～１００質量部
を含有し、曲げ撓み量が５ｍｍ以上である、ポリエチレン樹脂組成物。
〔２〕液晶ポリマーは、式［Ｉ］～［ＶＩ］
［化１］

［式中、ｐ、ｑ、ｒ、ｓ、ｔおよびｕは、それぞれ各繰返し単位の液晶ポリマー中での組成比（モル％）を示し、以下の式を満たす：
３５≦ｐ≦５５、
２５≦ｑ≦４５、
２≦ｒ≦１５、
０≦ｓ≦５、
２≦ｔ≦１５、
０≦ｕ≦５、
ｒ≧ｓ、
ｐ＋ｑ＋ｒ＋ｓ＋ｔ＋ｕ＝１００］
で表される繰返し単位を含んで構成される全芳香族液晶ポリエステルである、〔１〕に記載のポリエチレン樹脂組成物。
〔３〕式［ＶＩ］で表される繰返し単位は、式［ＶＩＩ］
［化２］

で表される繰返し単位である、〔２〕に記載のポリエチレン樹脂組成物。
〔４〕さらにｐ＞ｑを満たす、〔２〕または〔３〕に記載のポリエチレン樹脂組成物。
〔５〕〔１〕～〔４〕のいずれかに記載のポリエチレン樹脂組成物から構成される成形品。
〔６〕成形品が容器または蓋部材である、〔５〕に記載の成形品。

Preferred embodiments of the invention include the following.
[1] 100 parts by mass of polyethylene resin, and
0.1 to 100 parts by mass of a liquid crystal polymer having a crystal melting temperature of less than 210°C
A polyethylene resin composition containing and having a bending deflection amount of 5 mm or more.
[2] The liquid crystal polymer has formulas [I] to [VI]
[Chemical 1]

[Wherein, p, q, r, s, t and u each represent the composition ratio (mol%) of each repeating unit in the liquid crystal polymer and satisfy the following formula:
35≦p≦55,
25≤q≤45,
2≦r≦15,
0≦s≦5,
2≤t≤15,
0≤u≤5,
r≧s,
p+q+r+s+t+u=100]
The polyethylene resin composition according to [1], which is a wholly aromatic liquid crystalline polyester comprising a repeating unit represented by:
[3] The repeating unit represented by formula [VI] is represented by formula [VII]
[Chemical 2]

The polyethylene resin composition according to [2], which is a repeating unit represented by
[4] The polyethylene resin composition according to [2] or [3], which further satisfies p>q.
[5] A molded article composed of the polyethylene resin composition according to any one of [1] to [4].
[6] The molded article according to [5], which is a container or a lid member.

Claims (5)

100 parts by mass of a polyethylene resin, and 0.1 to 100 parts by mass of a liquid crystal polymer having a crystal melting temperature of less than 210°C,
The liquid crystal polymer has formulas [I] to [VI]

[Wherein, p, q, r, s, t and u each represent the composition ratio (mol%) of each repeating unit in the liquid crystal polymer and satisfy the following formula:
35≦p≦55,
25≤q≤45,
2≦r≦15,
0≦s≦5,
2≤t≤15,
0≤u≤5,
r≧s,
p+q+r+s+t+u=100]
A wholly aromatic liquid crystalline polyester comprising a repeating unit represented by
A polyethylene resin composition having a bending deflection amount of 5 mm or more. The repeating unit represented by formula [VI] is represented by formula [VII]

The polyethylene resin composition according to claim 1 , which is a repeating unit represented by. 3. The polyethylene resin composition according to claim 1 , further satisfying p> q . A molded article composed of the polyethylene resin composition according to any one of claims 1 to 3 . 5. The molded article according to claim 4 , wherein the molded article is a container or lid member.