Softened EVOH resin composition, refrigerant transport hose and tire

Abstract

To provide a softening EVOH-based resin composition excellent in gas barrier property and flexibility.SOLUTION: A softening EVOH-based resin composition is prepared by replacing with a softening component, a part of ethylene-vinyl alcohol copolymer in EVOH-based resin composition including ethylene-vinyl alcohol copolymer and elastomer. The composition is characterized in that the softening rate (%) calculated by formula (1): softening rate (%)=[(10% modulus of EVOH-based resin composition)-(10% modulus of softening material of that composition) / (10% modulus of EVOH-based resin composition]×100 ...(1), satisfies formula (2): 20%≤softening rate≤100% ...(2), and the permeability aggravation rate calculated by formula (3): permeability aggravation rate (%)=[(oxygen permeation degree of softening EVOH-based resin composition)-(that degree of EVOH-based resin composition / that degree of EVOH-based resin composition]×100 ...(3), satisfies formula (4): 0%≤permeability aggravation rate≤3,500% ...(4).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a softened EVOH-based resin composition, a refrigerant transport hose, and a tire. More specifically, the present invention relates to a softened EVOH-based resin composition in which a part of an ethylene-vinyl alcohol copolymer in an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer is replaced with a softening component, and to a refrigerant transport hose and a tire containing the softened EVOH-based resin composition. [Background technology]

[0002] Ethylene-vinyl alcohol copolymers have high gas barrier properties and are therefore expected to be used as the inner layer material of hoses and as inner liners for tires.

[0003] For example, Japanese Patent Application Laid-Open No. 2009-137195 (Patent Document 1) discloses a hose in which an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer is used for the inner layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-137195 A Summary of the Invention [Problem to be solved by the invention]

[0005] EVOH-based resin compositions have high gas barrier properties, but because they are hard and inflexible, when used as inner layer materials for hoses, they have the disadvantage of being less flexible than existing hoses. An object of the present invention is to provide a softened EVOH resin composition which has been softened while retaining its gas barrier properties. [Means for solving the problem]

[0006] The present inventors have discovered that by replacing a portion of the ethylene-vinyl alcohol copolymer in an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer with a softening component, it is possible to prepare a softened EVOH resin composition that has been softened while retaining gas barrier properties, and have thus completed the present invention.

[0007] The present invention (I) is a softened EVOH-based resin composition in which a part of an ethylene-vinyl alcohol copolymer in an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer is replaced with a softening component, the softened EVOH-based resin composition being represented by the formula (1) Softening rate (%)={(10% modulus of EVOH-based resin composition−10% modulus of softened EVOH-based resin composition) / 10% modulus of EVOH-based resin composition}×100 (1) The flexibility ratio is calculated by the formula (2) 20%≦flexibility rate≦100% (2) and satisfy the formula (3). Permeability deterioration rate (%)={(oxygen permeability of softened EVOH-based resin composition−oxygen permeability of EVOH-based resin composition) / oxygen permeability of EVOH-based resin composition}×100 (3) The permeability deterioration rate calculated by the formula (4) 0%≦Permeability deterioration rate≦3500% (4) The present invention is characterized in that: The present invention (II) is a refrigerant transport hose containing the softened EVOH-based resin composition of the present invention (I). The present invention (III) is a tire comprising the softened EVOH-based resin composition of the present invention (I).

[0008] The present invention includes the following embodiments. [1] A softened EVOH-based resin composition in which a part of an ethylene-vinyl alcohol copolymer in an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer is replaced with a softening component, the softened EVOH-based resin composition being represented by the formula (1). Softening rate (%)={(10% modulus of EVOH-based resin composition−10% modulus of softened EVOH-based resin composition) / 10% modulus of EVOH-based resin composition}×100 (1) The flexibility ratio is calculated by the formula (2) 20%≦flexibility rate≦100% (2) and satisfy the formula (3). Permeability deterioration rate (%)={(oxygen permeability of softened EVOH-based resin composition−oxygen permeability of EVOH-based resin composition) / oxygen permeability of EVOH-based resin composition}×100 (3) The permeability deterioration rate calculated by the formula (4) 0%≦Permeability deterioration rate≦3500% (4) A softened EVOH-based resin composition that satisfies the above requirements. [2] The softened EVOH-based resin composition according to [1], wherein the softening component is a polyester-polyester thermoplastic elastomer. [3] The softened EVOH-based resin composition according to [1] or [2], wherein the elastomer is a maleic anhydride-modified polyolefin. [4] The softened EVOH-based resin composition according to any one of [1] to [3], wherein the volume ratio of the elastomer is 50 volume % or more. [5] A softened EVOH-based resin composition according to any one of [1] to [4], in which 40% by volume or more of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition is substituted with a softening component. [6] The softened EVOH resin composition according to any one of [1] to [5], wherein the ethylene ratio of the ethylene-vinyl alcohol copolymer is 30 mol % or more. [7] A refrigerant transport hose comprising the softened EVOH-based resin composition according to any one of [1] to [6]. [8] A tire comprising the softened EVOH-based resin composition according to any one of [1] to [6]. Effect of the Invention

[0009] The softened EVOH resin composition of the present invention has excellent gas barrier properties and also excellent flexibility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention relates to a softened EVOH-based resin composition. The softened EVOH-based resin composition is an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer, in which a part of the ethylene-vinyl alcohol copolymer is replaced with a softening component. That is, the softened EVOH-based resin composition contains an ethylene-vinyl alcohol copolymer, an elastomer, and a softening component.

[0011] The softened EVOH-based resin composition is a compound represented by the formula (1) Softening rate (%)={(10% modulus of EVOH-based resin composition−10% modulus of softened EVOH-based resin composition) / 10% modulus of EVOH-based resin composition}×100 (1) The flexibility ratio calculated by the formula (2) 20%≦flexibility rate≦100% (2) and preferably satisfies formula (2') 20%≦flexibility rate≦80% (2′) More preferably, the formula (2″) is satisfied. 20%≦Flexibility rate≦60% (2″) Meet the following. When the flexibility rate satisfies the above formula, the flexibility of the hose is improved. The method for making the softening rate satisfy the above formula is to replace EVOH with a softening component that has high affinity with EVOH. However, the 10% modulus is the value at 25°C and is measured in accordance with JIS K7161.

[0012] The softened EVOH-based resin composition is represented by the formula (3). Permeability deterioration rate (%)={(oxygen permeability of softened EVOH-based resin composition−oxygen permeability of EVOH-based resin composition) / oxygen permeability of EVOH-based resin composition}×100 (3) The permeability deterioration rate calculated by the formula (4) 0%≦Permeability deterioration rate≦3500% (4) and preferably satisfies formula (4') 0%≦Permeability deterioration rate≦3450% (4′) More preferably, the formula (4″) is satisfied. 0%≦Permeability deterioration rate≦3400% (4″) Meet the following. When the permeability deterioration rate satisfies the above formula, the high gas barrier properties of EVOH can be maintained, which is expected to lead to weight reduction through thinner hoses. The method for making the rate of deterioration of permeability satisfy the above formula is to replace EVOH with a softening component that has high affinity with EVOH. However, the oxygen permeability is measured at a temperature of 21°C and a relative humidity of 50%.

[0013] The 10% modulus of the softened EVOH-based resin composition is preferably 0.5 to 10 MPa, more preferably 0.5 to 9.0 MPa, and even more preferably 0.5 to 7.0 MPa. If the 10% modulus is too small, it is impossible to attach metal fittings during hose production. If the 10% modulus is too large, the flexibility of the hose deteriorates.

[0014] The oxygen permeability of the softened EVOH-based resin composition is preferably 0.0001 to 0.0400 cm 3 mm / (m 2 ·day·mmHg), more preferably 0.0001 to 0.0300cm 3 mm / (m 2 ·day·mmHg), and more preferably 0.0001 to 0.0200 cm 3 mm / (m 2 If the oxygen permeability is too high, the hose must be made thicker when it is made, which reduces the flexibility of the hose.

[0015] Ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH") is a copolymer consisting of ethylene units (-CH2CH2-) and vinyl alcohol units (-CH2-CH(OH)-), and may contain other structural units in addition to the ethylene units and vinyl alcohol units, as long as the effects of the present invention are not impaired. The ratio (mol %) of the ethylene units to all structural units constituting the ethylene-vinyl alcohol copolymer is hereinafter referred to as the "ethylene ratio" of the ethylene-vinyl alcohol copolymer. The ethylene-vinyl alcohol copolymer is a saponification product of an ethylene-vinyl acetate copolymer, and its saponification degree is preferably 90% or more, more preferably 98% or more. If the saponification degree of the ethylene-vinyl alcohol copolymer is too low, the gas barrier property is deteriorated.

[0016] The ethylene ratio of the ethylene-vinyl alcohol copolymer is preferably 30 mol% or more, more preferably 30 to 90 mol%, and further preferably 30 to 60 mol%. If the ethylene ratio is too low, the flexibility of the ethylene-vinyl alcohol copolymer deteriorates. Conversely, if the ethylene ratio is too high, the gas barrier property deteriorates.

[0017] The elastomer is not limited as long as it exhibits the effects of the present invention. For example, preferred examples include butyl-based rubber, modified butyl-based rubber, olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, polyamide elastomer, and polyester elastomer, and among these, olefin-based thermoplastic elastomer is preferred. Examples of olefin-based thermoplastic elastomers include ethylene-α-olefin copolymers (ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-pentene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, etc.), ethylene-ethyl acrylate copolymers, maleic anhydride-modified polyolefins, maleic anhydride-modified ethylene-ethyl acrylate copolymers, ethylene-glycidyl methacrylate copolymers, etc., among which maleic anhydride-modified polyolefins are preferred. Examples of maleic anhydride-modified polyolefins include maleic anhydride-modified ethylene-α-olefin copolymers. By using maleic anhydride-modified polyolefins as elastomers, the affinity with EVOH is increased, making it possible to compound an elastomer component at a volume ratio of 50 volume % or more, and the softening effect is increased.

[0018] The volume ratio of the elastomer in the softened EVOH-based resin composition is preferably 50% by volume or more, more preferably 50 to 90% by volume, and even more preferably 60 to 90% by volume. If the volume ratio of the elastomer is too low, the softening effect is small. If the volume ratio of the elastomer is too high, the gas barrier property is deteriorated.

[0019] The softening component is a thermoplastic resin, a thermoplastic elastomer, a plasticizer, etc. other than the EVOH and elastomer contained in the EVOH-based resin composition. Specific examples of the softening component include a styrene-based thermoplastic elastomer, a polyamide elastomer, and a polyester elastomer. The softening component is preferably a polyester-polyester thermoplastic elastomer of a polyester elastomer. The polyester-polyester thermoplastic elastomer refers to a thermoplastic elastomer composed of a hard segment composed of a crystalline polyester block and a soft segment composed of a non-crystalline polyester block. Specific examples of the polyester-polyester thermoplastic elastomer include a thermoplastic elastomer in which the hard segment is a polybutylene terephthalate block and the soft segment is an aliphatic polyester block such as poly(ε-caprolactone) or polybutylene adipate. By using a polyester-polyester thermoplastic elastomer as the softening component, the affinity between the acid-modified polyolefin and EVOH is increased, and even if 40% or more by volume of EVOH is replaced, the gas barrier property is not significantly deteriorated.

[0020] The softened EVOH-based resin composition is preferably one in which 40% by volume or more of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition is replaced with a softening component, more preferably one in which 40 to 80% by volume of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition is replaced with a softening component, and even more preferably one in which 40 to 70% by volume of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition is replaced with a softening component. The ratio of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition replaced with the softening component is hereinafter also referred to as the "substitution rate". If the substitution rate is too low, sufficient softening effect cannot be obtained. If the substitution rate is too high, the gas barrier property deteriorates.

[0021] The softened EVOH-based resin composition includes an ethylene-vinyl alcohol copolymer, an elastomer, and a softening component. The volume ratio of the elastomer in the softened EVOH-based resin composition is preferably 50% by volume or more, more preferably 50 to 90% by volume, and even more preferably 60 to 90% by volume. If the volume ratio of the elastomer is too low, the softening effect is small. If the volume ratio of the elastomer is too high, the gas barrier property is deteriorated. The volume ratio of the softening component in the softened EVOH-based resin composition is preferably 10 to 35 volume %, more preferably 10 to 30 volume %, and further preferably 10 to 25 volume %. If the content of the softening component is too small, the softening effect is small. If the content of the softening component is too high, the gas barrier property is deteriorated. The softened EVOH-based resin composition may contain components other than the ethylene-vinyl alcohol copolymer, the elastomer, and the softening component, to the extent that the effects of the present invention are not impaired. Examples of the components other than the ethylene-vinyl alcohol copolymer, the elastomer, and the softening component include processing aids, crosslinking agents, antioxidants, and color masterbatches.

[0022] The method for producing the softened EVOH-based resin composition is not particularly limited. For example, the softened EVOH-based resin composition can be produced by kneading an ethylene-vinyl alcohol copolymer, an elastomer, a softening component, and, as necessary, other components, using a twin-screw kneading extruder or the like.

[0023] The softened EVOH-based resin composition is preferably used as an inner layer material for a hose or an inner liner for a tire.

[0024] The present invention (II) is a refrigerant transport hose containing the softened EVOH-based resin composition of the present invention (I). The refrigerant transport hose preferably comprises an inner layer, a reinforcing layer and an outer layer, and the inner layer comprises the softened EVOH-based resin composition of the present invention (I). Since the inner layer of the refrigerant transport hose comprises the softened EVOH-based resin composition of the present invention (I), the flexibility of the hose is improved. The reinforcing layer may be, for example and without limitation, a layer of braided fabric. The outer layer is a layer made of, but not limited to, a thermoplastic resin composition, a thermoplastic elastomer composition, rubber, or the like. The method for producing the refrigerant transport hose is not particularly limited. For example, the refrigerant transport hose can be produced by first extruding the inner layer into a tubular shape by extrusion molding, then braiding fibers that will become a reinforcing layer on the tube, and further covering the fibers with an outer layer by extrusion molding. The refrigerant transport hose of the present invention (II) can be used as a hose for transporting refrigerants such as air conditioners, and is particularly suitable for use as a hose for transporting refrigerants in automotive air conditioners. Refrigerants for air conditioners include hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), hydrocarbons, carbon dioxide, ammonia, water, etc., HFCs include R410A, R32, R404A, R407C, R507A, R134a, etc., HFOs include R1234yf, R1234ze, 1233zd, R1123, R1224yd, R1336mzz, etc., and hydrocarbons include methane, ethane, propane, propylene, butane, isobutane, hexafluoropropane, pentane, etc.

[0025] The present invention (III) is a tire comprising the softened EVOH-based resin composition of the present invention (I). The tire is preferably a pneumatic tire. The tire includes, but is not limited to, an inner liner, a carcass layer, a belt layer, and a tread layer, in this order from the inside, and preferably, the inner liner includes the softened EVOH-based resin composition of the present invention (I). The air leakage rate is reduced by the inner liner including the softened EVOH-based resin composition of the present invention (I). The tire can be manufactured by a conventional method. For example, the softened EVOH-based resin composition of the present invention (I) is molded into a sheet by a molding method such as T-die extrusion molding or inflation molding to produce a sheet of the softened EVOH-based resin composition of the present invention (I). The sheet of the softened EVOH-based resin composition of the present invention (I) is placed on a tire molding drum, and members used in normal tire manufacturing, such as a carcass layer, a belt layer, and a tread layer made of unvulcanized rubber, are laminated on top of it in order, and after molding, the drum is removed to obtain a green tire, and then this green tire is heated and vulcanized according to a conventional method, whereby a tire can be manufactured. EXAMPLES

[0026] [raw materials] The raw materials used in the following examples and comparative examples are as follows. (Ethylene-vinyl alcohol copolymer) EVOH: Mitsubishi Chemical Corporation's ethylene-vinyl alcohol copolymer (ethylene ratio 48 mol%) "Soarnol" (registered trademark) H4815 (Elastomer) Mah-PO: Maleic anhydride modified ethylene-1-butene copolymer "Tafmer" (registered trademark) MH7020 manufactured by Mitsui Chemicals, Inc. Br-IPMS: Brominated isobutylene-p-methylstyrene copolymer "EXXPRO" (registered trademark) 3745 manufactured by ExxonMobil Chemical Corporation (Softening ingredient) TPEE-1: Thermoplastic polyester elastomer "Pelprene" (registered trademark) S-1001 manufactured by Toyobo Co., Ltd. TPEE-2: Thermoplastic polyester elastomer "Pelprene" (registered trademark) P-30B manufactured by Toyobo Co., Ltd. Triacetin: Glyceryl triacetate manufactured by Daihachi Chemical Industry Co., Ltd.

[0027] [Examples 1 to 3, Comparative Examples 1 to 13] The raw materials shown in Table 1 or Table 2 were fed into a twin-screw kneading extruder (manufactured by The Japan Steel Works, Ltd.) in the blending ratios shown in Table 1 or Table 2, and kneaded for 3 minutes at 235° C. The kneaded product was continuously extruded from the extruder in the form of strands, cooled with water, and cut with a cutter to obtain pellets of an EVOH-based resin composition or a softened EVOH-based resin composition. The 10% modulus and oxygen permeability of the obtained EVOH-based resin composition or softened EVOH-based resin composition were measured, and the extrusion processability was evaluated. The measurement and evaluation results are shown in Table 1 or Table 2. The measurement and evaluation methods for each measurement and evaluation item are as follows:

[0028] [Measurement of 10% modulus] A sample of the EVOH-based resin composition or the softened EVOH-based resin composition was molded into a sheet having an average thickness of 0.2 mm using a 40 mmφ single-screw extruder with a 200 mm wide T-type die (manufactured by Plagiken Co., Ltd.) with the cylinder and die temperatures set to the melting point of the polymer component with the highest melting point in the sample composition + 10°C, a cooling roll temperature of 50°C, and a take-up speed of 3 m / min. The obtained sheet was punched out into a JIS No. 3 dumbbell shape and subjected to a tensile test at a temperature of 25°C, a relative humidity of 50%, and a speed of 500 mm / min in accordance with JIS K7161. The stress at 10% elongation (10% modulus) was obtained from the obtained stress-strain curve.

[0029] [Oxygen permeability measurement] A sheet prepared in the measurement of 10% modulus was cut out and measured at a temperature of 21° C. and a relative humidity of 50% using OXTRAN 1 / 50 manufactured by MOCON.

[0030] [Evaluation of extrusion processability] A sample of the EVOH-based resin composition or the softened EVOH-based resin composition was extruded at 235°C using a T-die sheet molding device (manufactured by Tommy Machinery Co., Ltd.) to produce a film with a thickness of 200 μm. The sample was evaluated as follows: ◯ if the sample could be molded without any problems; △ if minor particles, holes, or cuts at the sheet edges occurred; and × if serious particles, holes, or cuts at the sheet edges occurred.

[0031] [Table 1]

[0032] [Table 2] [Industrial Applicability]

[0033] The softened EVOH-based resin composition of the present invention can be suitably used as an inner layer material for refrigerant transport hoses or as a material for inner liners of tires.

Claims

1. A softened EVOH-based resin composition comprising an EVOH-based resin composition containing an ethylene-vinyl alcohol copolymer and an elastomer, wherein the amount of the ethylene-vinyl alcohol copolymer is reduced and a softening component is mixed in an amount equal to the amount of the reduced amount of the ethylene-vinyl alcohol copolymer, thereby replacing 40 to 80 volume % of the ethylene-vinyl alcohol copolymer in the EVOH-based resin composition with the softening component, wherein the elastomer is a maleic anhydride modified polyolefin, the softening component is a polyester-polyester thermoplastic elastomer, the volume ratio of the elastomer in the softened EVOH-based resin composition is 50 to 90 volume %, and the softened EVOH-based resin composition satisfies the following formula (1): Softening rate (%)={(10% modulus of EVOH-based resin composition−10% modulus of softened EVOH-based resin composition) / 10% modulus of EVOH-based resin composition}×100 (1) The flexibility ratio is calculated by the formula (2) 20%≦flexibility rate≦100%...(2) and satisfying formula (3). Permeability deterioration rate (%)={(oxygen permeability of softened EVOH-based resin composition−oxygen permeability of EVOH-based resin composition) / oxygen permeability of EVOH-based resin composition}×100 (3) The permeability deterioration rate calculated by the formula (4) 0%≦permeability deterioration rate≦3500% (4) A softened EVOH-based resin composition that satisfies the above requirements.

2. 2. The softened EVOH-based resin composition according to claim 1, wherein the ethylene-vinyl alcohol copolymer has an ethylene ratio of 30 mol % or more.

3. A refrigerant transport hose comprising the softened EVOH resin composition according to claim 1 or 2.

4. A tire comprising the softened EVOH-based resin composition according to claim 1 or 2.

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