Multi-layer tube

Abstract

To provide a multi-layer tube having an excellent vibration damping property.SOLUTION: There is provided a multi-layer tube having a layer containing an ethylene-vinyl alcohol copolymer, wherein the multi-layer tube contains a modified ethylene-vinyl alcohol copolymer in which the ethylene-vinyl alcohol copolymer has a structural unit containing a heteroatom selected from oxygen, nitrogen, and sulfur in a side chain and has a durometer hardness of D50 or less as measured from an outer layer side of the multi-layer tube.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a multi-layer tube, and more particularly to a multi-layer tube having excellent vibration damping properties. [Background technology]

[0002] In recent years, resin tubes have come to be widely used for transporting liquids, etc. Resin tubes have many advantages, such as not rusting like metal tubes, being easy to process, allowing greater freedom in design, and being lightweight.

[0003] As an example of the resin tube, Patent Document 1 discloses a multilayer tube composed of at least three layers, in which the inner layer is composed of a fluororesin composition, the middle layer is composed of a composition containing at least an ethylene-vinyl alcohol copolymer and a binder component, and the outer layer is composed of a thermoplastic resin or an elastomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-118329 A Summary of the Invention [Problem to be solved by the invention]

[0005] Tubes used inside machines are required to have vibration damping properties, but the multi-layer tube disclosed in Patent Document 1 does not have sufficient vibration damping properties and tends to vibrate easily during machine operation. SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a multi-layer tube having excellent vibration damping properties. [Means for solving the problem]

[0006] However, in view of these circumstances, the present inventors conducted extensive research and discovered that a multi-layer tube with excellent vibration-damping properties can be obtained by having a layer containing a specific modified ethylene-vinyl alcohol copolymer (hereinafter, ethylene-vinyl alcohol copolymer will be referred to as "EVOH") and having a durometer hardness of D50 or less measured from the outer layer side, and thus completed the present invention.

[0007] That is, the present invention has the following aspects. [1] A multi-layer tube having a layer comprising EVOH, The EVOH contains a modified EVOH having a structural unit represented by the following chemical formula (1): The multi-layer tube has a durometer hardness of D50 or less as measured from the outer layer side of the multi-layer tube. [ka] [2] The multi-layer tube according to [1], wherein the heteroatom in X in the chemical formula (1) is any one selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom. [3] The multi-layer tube according to [1] or [2], wherein the multi-layer tube has a minimum bending radius of 20 mm or less. [4] The multi-layer tube according to any one of [1] to [3], wherein the multi-layer tube has a loss factor of 0.04 or more. Effect of the Invention

[0008] The multilayer tube of the present invention has a layer containing a specific modified EVOH and has a durometer hardness of D50 or less measured from the outer layer side, and therefore has excellent vibration damping properties, and can be suitably used as a tube used inside a machine that is subject to a lot of vibration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described below based on examples of the mode for carrying out the present invention. However, the present invention is not limited to the embodiment described below.

[0010] In the present invention, "T and / or U (T and U are optional configurations)" means at least one of T and U, and means three possibilities: T only, U only, and T and U. When expressed as "V to W" (V and W are arbitrary numbers), unless otherwise specified, it includes the meaning of "V or more and W or less", as well as "preferably greater than V" or "preferably smaller than W". When it is expressed as "V or more" (V is any number) or "W or less" (W is any number), it also includes the meaning that "it is preferably greater than V" or "it is preferably less than W".

[0011] In the present invention, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component in the target object is usually 50 mass % or more, preferably 55 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, and may be 100 mass %.

[0012] A multi-layer tube according to one embodiment of the present invention (hereinafter sometimes referred to as "the present multi-layer tube") is a multi-layer tube having a layer containing EVOH, the EVOH being a modified EVOH having a structural unit represented by the following chemical formula (1), and the durometer hardness measured from the outer layer side of the multi-layer tube is D50 or less. In the present invention, a tube refers to a tubular body having a cavity inside, and is a concept that also includes hoses and the like.

[0013] [ka]

[0014] The layer structure of the present multilayer tube is not particularly limited as long as it has a layer containing EVOH (hereinafter referred to as "EVOH layer"), but it is preferable that the tube has an outer layer in addition to the EVOH layer, and may have an inner layer, an adhesive resin layer, etc. Also, the tube may have two or more layers of the EVOH layer, outer layer, inner layer, adhesive resin layer, etc.

[0015] Specific layer configurations of the present multilayer tube include, for example, outer layer / EVOH layer, outer layer / adhesive resin layer / EVOH layer, outer layer / adhesive resin layer / EVOH layer / inner layer, outer layer 1 / outer layer 2 / adhesive resin layer / EVOH layer / inner layer, etc.

[0016] The multilayer tube has a durometer hardness of D50 or less, preferably D45 or less, more preferably D40 or less, and particularly preferably D30 or less, measured from the outer layer side. Since the lower the hardness, the greater the vibration damping properties, no lower limit is set, but in practical use, the durometer hardness is usually A30 or more, preferably A50 or more. By having a durometer hardness of D50 or less, the multilayer tube has excellent flexibility. The durometer hardness is obtained by cutting the multi-layer tube in half in the circumferential direction with a razor to prepare a semicircular cut tube, and then measuring the durometer hardness from the outer layer side. Since the durometer hardness value changes over time, in the present invention, the value is read within 1 second after the pressurized surfaces come into contact. The above measurement is carried out three times, and the average value is taken as the durometer hardness.

[0017] Furthermore, the multilayer tube preferably has a minimum bending radius of 25 mm or less, more preferably 20 mm or less, and even more preferably 15 mm or less. The smaller the minimum bending radius, the better, but it is practically 1 mm or more, preferably 5 mm or more, and even more preferably 7 mm or more. By having a minimum bending radius of the above numerical value or less, there is a tendency for the tube to have excellent kink resistance. The minimum bending radius is determined by holding both ends of a 1 m long multi-layer tube and bending it in a twisting manner, and determining the radius just before the multi-layer tube breaks as the minimum bending radius.

[0018] The loss factor (η) of the multilayer tube is preferably 0.04 or more, more preferably 0.05 or more, and even more preferably 0.06 or more. When the loss factor is equal to or more than the above value, the vibration damping property tends to be excellent. The upper limit of the loss factor is usually 1.0.

[0019] The loss factor (η) is determined by the following measurement method. A multi-layer tube with a marker attached to the center is clamped at both ends at 30 cm intervals and vibrated. The marker is photographed with a high-speed camera, and the logarithmic decrement (δ) and loss factor (η) are calculated from the vibration of the marker using the following formula. TIFF2025039323000003.tif49131

[0020] The diameter of the present multi-layer tube is not particularly limited, but the inner diameter is preferably 1 to 10 mm, and the outer diameter is preferably 3 to 12 mm. The thickness of the present multi-layer tube is preferably 0.5 μm to 6 mm. Each layer of the multi-layer tube will be described below in order.

[0021] [EVOH layer] The EVOH contained in the EVOH layer is usually a resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, and is a water-insoluble thermoplastic resin.

[0022] The polymerization method of the ethylene and the vinyl ester monomer can be carried out by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, and generally, solution polymerization using methanol as a solvent is used. The saponification of the obtained ethylene-vinyl ester copolymer can also be carried out by a known method.

[0023] The EVOH produced in this manner is mainly composed of structural units derived from ethylene and vinyl alcohol structural units, and usually contains a small amount of vinyl ester structural units that remain unsaponified.

[0024] As the vinyl ester monomer, vinyl acetate is typically used because of its good market availability and efficiency in treating impurities during production. Other vinyl ester monomers include, for example, aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, and aromatic vinyl esters such as vinyl benzoate. Usually, aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms can be used. These can be used alone or in combination of two or more kinds.

[0025] The content of the ethylene structural unit in the EVOH can be controlled by the ethylene pressure when the vinyl ester monomer and ethylene are copolymerized, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, and particularly preferably 30 to 45 mol%. If the content is too low, the melt moldability tends to decrease. Conversely, if the content is too high, the gas barrier property tends to decrease. The content of the ethylene structural unit can be measured based on ISO14663.

[0026] The degree of saponification of the vinyl ester component in the EVOH can be controlled by the amount, temperature, time, etc. of the saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used) used when saponifying the ethylene-vinyl ester copolymer, and is usually 90 to 100 mol%, preferably 95 to 100 mol%, and particularly preferably 99 to 100 mol%. If the degree of saponification is too low, the gas barrier properties, heat stability, moisture resistance, etc. tend to decrease. The degree of saponification of the EVOH can be measured based on JIS K6726 (wherein the EVOH is used as a solution uniformly dissolved in a water / methanol solvent).

[0027] The EVOH may further contain structural units derived from the comonomers shown below within a range that does not impair the effects of the present invention (for example, 10 mol % or less of the EVOH). Examples of the comonomer include olefins such as propylene, 1-butene, and isobutene; hydroxyl-containing α-olefins such as 3-buten-1-ol, 3-butene-1,2-diol, 4-penten-1-ol, and 5-hexene-1,2-diol, and derivatives thereof such as esters and acylation products; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloxy. -Hydroxyalkylvinylidene diacetates such as 2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, or their salts or mono- or dialkyl esters in which the alkyl group has 1 to 18 carbon atoms; acrylamide, N-alkylacrylamide in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salts, acrylamidopropyldimethylamine or its acid salts or its quaternary salts, etc. acrylamides such as methacrylamide, N-alkyl methacrylamides in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethyl methacrylamide, 2-methacrylamidopropanesulfonic acid or its salt, methacrylamidepropyldimethylamine or its acid salt or its quaternary salt, and other methacrylamides; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, and other N-vinylamides; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers in which the alkyl group has 1 to 18 carbon atoms, hydrochloride, etc. vinyl ethers such as alkoxyalkyl vinyl ether and alkoxyalkyl vinyl ether; halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamido-2-methylpropanesulfonic acid. These can be used alone or in combination of two or more.

[0028] In particular, EVOH having a primary hydroxyl group in the side chain is preferred because it provides good secondary formability in stretching treatment and vacuum / pressure molding, and among these, EVOH having a 1,2-diol structure in the side chain is preferred.

[0029] The EVOH used in the present invention may be "post-modified" such as urethanized, acetalized, cyanoethylated, oxyalkylated, or acylated.

[0030] Furthermore, the EVOH may be a mixture with other different EVOHs, and examples of such other EVOHs include those having a different degree of saponification, a different degree of polymerization, and those having different copolymerization components.

[0031] [Modified EVOH] The EVOH used in the present invention contains a modified EVOH having a structural unit represented by the following chemical formula (1) from the viewpoint of vibration damping. The EVOH used in the present invention may contain EVOH other than modified EVOH, but it is preferable from the viewpoint of the effects of the present invention that the EVOH is modified EVOH. The modified EVOH will be described below.

[0032] [ka]

[0033] The modified EVOH has a structural unit represented by the chemical formula (1) in the main chain. The modified EVOH may have a plurality of structural units represented by the chemical formula (1).

[0034] In the chemical formula (1), X represents an organic chain having a heteroatom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, and a silicon atom. From an industrial viewpoint, the heteroatom is preferably an oxygen atom, a nitrogen atom, or a sulfur atom, and more preferably an oxygen atom. When the modified EVOH has a plurality of structural units represented by the chemical formula (1), X may be the same or different, but it is preferable that X is the same.

[0035] From the viewpoint of production, X is preferably an organic chain having a hydrocarbon chain which may have a substituent and which has a carbonyl group as the starting point, and a heteroatom which may have a substituent at the repeating end. Also, X may have other heteroatoms as long as it has a heteroatom at least at the repeating end, which has a carbonyl group as the starting point.

[0036] X is an organic chain having a hydrocarbon chain which may have a substituent and a heteroatom which may have a substituent at a repeating terminal thereof, and the hydrocarbon chain which may have a substituent is represented by R x When the repeating terminal heteroatom which may have a substituent is represented by Z, the compound is represented by the following chemical formula (2).

[0037] [ka]

[0038] In the chemical formula (2), when Z is an oxygen atom, the repeating unit is -CO-R x When Z is a nitrogen atom, the repeating unit is -CO-R x -NH-, -CO-R x -NR 3 When Z is a sulfur atom, the repeating unit is -CO-R x -S- is one example. Examples of the substituents that may be possessed by the hydrocarbon and heteroatoms include alkyl groups such as methyl and ethyl groups, aryl groups such as aromatic rings, and acyl groups such as acetyl groups. x -NR 3 -R in 3 represents an alkyl group such as a methyl group or an ethyl group, an aryl group such as an aromatic ring, or an acyl group such as an acetyl group. Among these, from the viewpoint of improving the gas barrier property, the repeating unit is preferably -CO-R x -O-, -CO-R x -NH- or -CO-R x -S- is preferred, and it is particularly preferred that Z is an oxygen atom. Specifically, it is preferred to contain an aliphatic polyester unit represented by the following chemical formula (3).

[0039] [ka]

[0040] The hydrocarbon chain R in chemical formulas (2) and (3) x is preferably a straight or branched chain having 1 to 10 carbon atoms. Examples of the straight or branched hydrocarbon chain having 1 to 10 carbon atoms include a methylene group (-CH2-), a methine group (-CHR-), a quaternary carbon having no hydrogen atom (-CR 1 R 2 -), propylene group, isopropylene group, butylene group, isobutylene group, phenylene group, etc. 1 , R 2 represents an alkyl group such as a methyl group or an ethyl group, or an aryl group such as an aromatic ring. Of these, the hydrocarbon chain is more preferably a linear or branched alkyl chain having 2 to 8 carbon atoms, and even more preferably a linear or branched alkyl chain having 3 to 7 carbon atoms. Of these, from the viewpoint of improving the storage stability and processing stability of the resin, a linear hydrocarbon chain is preferred, a linear alkyl chain having 2 to 8 carbon atoms is more preferred, and a linear alkyl chain having 3 to 7 carbon atoms is particularly preferred.

[0041] In the chemical formulas (1) to (3), n represents a positive integer. n is preferably an integer from 1 to 20, and more preferably an integer from 1 to 10. If n is too large, the barrier properties tend to decrease, so n is preferably an integer of 20 or less.

[0042] In the chemical formula (1), when n is 2 or more, the multiple Xs may be the same or different, but are preferably the same from the viewpoint of barrier properties. x In the chemical formula (3), when n is 2 or more, a plurality of R x may be the same or different, but are preferably the same from the viewpoint of barrier properties.

[0043] In the resin composition according to the first embodiment of the present invention, the average value of n in the chemical formulas (1) to (3) in the modified EVOH (i.e., sometimes referred to as the average chain length of the graft chains) is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, even more preferably in the range of 1 to 2, and particularly preferably in the range of 1 to 1.5. If the average value of n is too large, the variation in the chain length of the graft chains increases, tending to reduce the gas barrier property, so that it is preferably 10 or less.

[0044] The structural units represented by chemical formulas (1) to (3) can be identified by general organic chemistry techniques such as nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy, and mass spectrometry. The average chain length of the graft chains in the chemical formulas (1) to (3) in the modified EVOH of this embodiment is 1 It can be calculated from the H-NMR measurement results.

[0045] [Method for producing modified EVOH] The modified EVOH having a structural unit represented by chemical formula (1) in its main chain can be obtained, for example, by grafting EVOH and a compound having a heterofunctional group in a molten state of EVOH while heating and stirring in a stirring tank-type production apparatus having stirring blades, or by using an extruder or a shear molding machine equipped with a feedback screw. The repeating unit of chemical formula (1) in the main chain of the modified EVOH, that is, the formation of the side chain graft structure by the graft reaction, begins with the hydroxyl group of EVOH as the initiation terminal.

[0046] [Compounds with heterofunctional groups] The heterofunctional group is a functional group having a heteroatom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, and a silicon atom. Specific examples of the functional group having a heteroatom include an ester group, a carboxylic acid group, an acyl group, a thioester group, an amide group, a carbonate group, a carbamate group, a thiocarbamate group, a carbamide group, an N-acyl group, and an N,N'-diacyl group.

[0047] Examples of compounds having a heterofunctional group include cyclic compounds having a heterofunctional group, carboxylic acid compounds, carbonate compounds, carbamate compounds, thiocarbamate compounds, diacyl compounds, triacyl compounds, and analogs thereof. Of these, cyclic compounds having a heterofunctional group are preferred.

[0048] [Cyclic compounds with heterofunctional groups] As the cyclic compound having a heterofunctional group, a heterocyclic compound having 2 or more carbon atoms is preferable. Examples of the cyclic compound having a heterofunctional group include cyclic esters such as lactones, cyclic amides such as lactams, cyclic carbonates such as ethylene carbonate and propylene carbonate, cyclic thioesters such as thietan-2-one, 3,3-dimethylthietan-2-one, 4-methylthietan-2-one, 3-methylthietan-2-one, 3-ethylthietan-2-one, and 3-methyl-3-ethylthietan-2-one, cyclic carbamates such as ethylene carbamate, imide compounds such as phenylphthalimide and cyclohexane dicarboxyimide, cyclic urea derivatives such as N,N'-dimethylpropyleneurea and 1,3-dimethyl-2-imidazolidinone, and cyclic N,N'-diacyl compounds such as N-acyl-substituted caprolactam. Among these, cyclic esters are preferable, and lactones are more preferable.

[0049] The lactones are preferably lactones having 3 to 10 carbon atoms constituting a ring that forms an aliphatic polyester by ring-opening polymerization. When such lactones do not have a substituent, they are represented by the following general formula (4).

[0050] [ka]

[0051] In the formula (4), n is an integer of 2 to 9, and preferably n is 4 to 5. In addition, the alkylene chain -(CH2) in the formula (4) n Any one of the carbon atoms may have at least one substituent, such as a lower alkyl group having about 1 to 8 carbon atoms, a lower alkoxy group, a cycloalkyl group, a phenyl group or an aralkyl group.

[0052] Specific examples of such lactones include β-propionolactones, γ-butyrolactones, ε-caprolactones, and δ-valerolactones.

[0053] Examples of the β-propionolactones include β-propionolactone, dimethylpropionolactone, and the like.

[0054] Examples of the γ-butyrolactones include butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprylolactone, γ-laurolactone, γ-palmitolactone, γ-stearolactone, crotonolactone, α-angelicalactone, and β-angelicalactone.

[0055] Examples of the ε-caprolactones include monoalkyl-ε-caprolactones such as ε-caprolactone, monomethyl-ε-caprolactone, monoethyl-ε-caprolactone, monodecyl-ε-caprolactone, monopropyl-ε-caprolactone, and monodecyl-ε-caprolactone; dialkyl-ε-caprolactones in which two alkyl groups are substituted on carbon atoms other than the ε position; trialkyl-ε-caprolactones in which three alkyl groups are substituted on carbon atoms other than the ε position; alkoxy-ε-caprolactones such as ethoxy-ε-caprolactone; cycloalkyl-lactones such as cyclohexyl-ε-caprolactone; aralkyl-ε-caprolactones such as benzyl-ε-caprolactone; and aryl-ε-caprolactones such as phenyl-ε-caprolactone.

[0056] Examples of the δ-valerolactones include 5-valerolactone, 3-methyl-5-valerolactone, 3,3-dimethyl-5-valerolactone, 2-methyl-5-valerolactone, and 3-ethyl-5-valerolactone.

[0057] These lactones can be used alone or in combination of two or more.

[0058] Among these, ε-caprolactones and δ-valerolactones are particularly preferred, with ε-caprolactone being particularly preferred since it is inexpensive and easily available.

[0059] [Carboxylic acid compounds] Examples of the carboxylic acid compound include linear carboxylic acid esters, linear carboxylic acid thioesters, linear carboxylic acid amides, acyl halides of carboxylic acids, acid anhydrides, etc. Among these, linear carboxylic acid esters are preferred.

[0060] [Carbonate compounds] Examples of the carbonate compound include various dialkyl carbonates, diaryl carbonates, and aryl alkyl carbonates.

[0061] [Carbamate compounds] Examples of the carbamate compound include methyl carbamate and ethyl carbamate.

[0062] [Thiocarbamate compounds] Examples of the thiocarbamate compound include derivatives such as dimethylamino-S-arylthiocarbamate.

[0063] [Diacyl compounds] Examples of the diacyl compound include diacetamide and diacetyl(cyclopentyl)azane.

[0064] [Triacyl compounds] Examples of triacyl compounds include triacetamide and tribenzamide.

[0065] In addition, as the compound having a heterofunctional group, an oligomer or polymer of the repeating structural unit represented by n in the chemical formulas (1) to (3) can be used. For example, polyesters such as poly-ε-caprolactone and polylactic acid, polyamides such as poly-ε-caprolactam, polythioesters, etc. can be used.

[0066] As described above, the modified EVOH having a structural unit represented by chemical formula (1) can be produced by melt-kneading EVOH and a compound having a heterofunctional group while heating and stirring the EVOH in a molten state in a stirring tank-type production apparatus having stirring blades, or by using an extruder or a shear molding machine equipped with a feedback screw.

[0067] For example, when a cyclic compound having a heterofunctional group is used as the compound having a heterofunctional group, a modified EVOH having a structural unit represented by chemical formula (1) in the main chain can be produced by carrying out a ring-opening polymerization reaction of the cyclic compound having a heterofunctional group and a graft reaction in the presence of EVOH. On the other hand, when a carboxylic acid compound is used as the compound having a heterofunctional group, a modified EVOH having a structural unit represented by chemical formula (1) in the main chain can be produced by carrying out a nucleophilic substitution reaction or dehydration condensation reaction of the carboxylic acid compound in the presence of EVOH and a graft reaction.

[0068] Among these, the modified EVOH is preferably an EVOH containing an aliphatic polyester unit (aliphatic polyester modified EVOH), which is a ring-opening polymer of a lactone ring having 3 to 10 carbon atoms constituting the ring.

[0069] In the case of the reaction involving ring-opening polymerization, it is preferable to add a conventionally known ring-opening polymerization catalyst. Examples of the ring-opening polymerization catalyst include titanium compounds and tin compounds. Specifically, titanium alkoxides such as tetra-n-butoxytitanium, tetraisobutoxytitanium, and tetraisopropoxytitanium, tin alkoxides such as dibutyldibutoxytin, tin ester compounds such as tin 2-ethylhexanoate and dibutyltin diacetate, etc. are included. Among these, tetra-n-butoxytitanium and tin 2-ethylhexanoate are preferred because they are inexpensive and easily available.

[0070] The reaction can also be carried out in a heated, molten state in a kneading machine such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a Brabender.

[0071] In addition, the reaction time and temperature in the ring-opening polymerization are not particularly limited and may be appropriately selected, but it is preferable to carry out the reaction at 50 to 250°C for 10 seconds to 24 hours while stirring, and more preferably to carry out the reaction at 150 to 230°C for 50 seconds to 10 hours while stirring. If the reaction time is shorter than the lower limit or the reaction temperature is lower than the lower limit, the reaction rate decreases, and unreacted compounds tend to bleed out from the molded product, causing deterioration of the surface appearance. If the reaction time is longer than the upper limit or the reaction temperature is higher than the upper limit, crosslinking occurs between the modified EVOH, and poor appearance of the molded product such as fish eyes tends to occur.

[0072] In the modified EVOH thus obtained, the content of the EVOH units forming the main chain of the modified EVOH is usually 40 to 99 mass %, preferably 45 to 95 mass %, and particularly preferably 50 to 90 mass %. The content of the structural unit represented by any one of chemical formulas (1) to (3) grafted to the main chain is usually 1 to 60 mass%, preferably 5 to 55 mass%, and particularly preferably 10 to 50 mass%. If the content of EVOH units is too high, the mechanical strength, particularly the tensile breaking strain, tends to be difficult to improve, while if the amount of EVOH units is too low, the adhesiveness is strong and blocking of the molded product tends to occur easily. The content of EVOH units in the modified EVOH and the content of the structural unit represented by any one of chemical formulas (1) to (3) are 1 It can be calculated from the H-NMR measurement results.

[0073] The number average molecular weight of the modified EVOH (measured by GPC in terms of standard polystyrene) is usually 5,000 to 300,000, preferably 10,000 to 200,000, and particularly preferably 10,000 to 100,000. If the number average molecular weight of the modified EVOH is too high, the melt viscosity tends to be too high, and dispersibility tends to decrease, while if the number average molecular weight of the modified EVOH is too low, the melt viscosity tends to be too low, and stable melt molding tends to be difficult. The number average molecular weight of the modified EVOH can be calculated from the results of GPC measurement.

[0074] The modification rate of the modified EVOH is usually 0.1 to 30 mol%, more preferably 1 to 25 mol%, and particularly preferably 5 to 20 mol%. If the modification rate is too low, the effects of the present invention tend not to be obtained, whereas if the modification rate is too high, the adhesion is strong and blocking of the molded product tends to occur easily. The modification rate is 1 It can be calculated from the H-NMR measurement results.

[0075] Furthermore, the average value of n in the chemical formulas (1) to (3) in the modified EVOH (i.e., the average chain length of the graft chains) is usually 1 to 15, preferably 1 to 10, and particularly preferably 1 to 8. If the average chain length of the graft chains is too long, the adhesion is strong and blocking of the molded product tends to occur easily. The average chain length of the graft chains is, 1 It can be calculated from the H-NMR measurement results.

[0076] Specifically, under the following conditions: 1 By measuring with H-NMR, the modification rate of the modified EVOH and the average chain length of the grafted chains can be calculated. (a) 1 H-NMR measurement conditions Internal standard: Tetramethylsilane Solvent: d6-DMSO -Measured polymer concentration: 5% by mass (sample 0.1 g, solvent 2 mL) ·Measurement temperature: 50℃ (323K) Irradiation pulse: 45° pulse Pulse interval: 10sec Number of times: 16 (b) Resonance absorption peak assignment (I) 0.8 to 0.9 ppm: -CH3 at the end of modified EVOH (II) 1.0 to 1.9 ppm: -CH2- in the modified EVOH main chain and adjacent -CH2- in the graft chain (III) 2.0 ppm: -CH3 of the residual acetyl group of modified EVOH (IV) 2.1 to 2.3 ppm: -CH2- adjacent to the carboxy group of the graft chain (V) 3.3 to 4.0 ppm: -CH- adjacent to -OH of modified EVOH and -CH2- adjacent to -OH of graft chain (VI) 4.0 to 4.7 ppm: -OH of modified EVOH and graft chain, and -CH2- adjacent to the ester bond of the graft chain (c) Calculation of modification rate and average chain length Using the integrals of the resonance absorption peaks (I) to (VI), the following simultaneous equations (i) to (vi) were formulated, and the amount of modified groups C (moles) and the average chain length n (moles) of the grafted chains were calculated from the solutions of the simultaneous equations. Furthermore, the modification rate F (mol%) was calculated from equation (vii). Formula (i): 3 × M = [integral value of peak (I)] Formula (ii): (2 x M) + (2 x A) + (4 x E) + (2 x O) + (6 x n + 2) x C = [integral value of peak (II)] Formula (iii): 3 × A = [integral value of peak (III)] Formula (vi): 2 × n × C = [integral value of peak (IV)] Formula (v): O + (2 × C) = [Integral value of peak (V)] Formula (vi): O + (2 × n-1) × C = [integral value of peak (VI)] Formula (vii): X = C / (M + A + O + C + E) × 100 Here, M, A, O, C, n, E, and F represent the following values: M: Amount of terminal methyl groups in modified EVOH (mol) A: Amount of acetyl groups in modified EVOH (mol) O: Amount of hydroxyl groups in modified EVOH (mol) C: Amount of modified groups in modified EVOH (mol) n: average length of grafted chains (units) E: Amount of ethylene groups in modified EVOH (mol) F: Modification rate of modified EVOH (mol%)

[0077] The glass transition temperature (Tg) of the modified EVOH is usually −50 to 60° C., preferably −30 to 45° C., and particularly preferably −10 to 35° C. If the glass transition temperature is too low, blocking of the molded product tends to occur easily, while if the glass transition temperature is too high, the effects of the present invention tend not to be obtained. The glass transition temperature can be measured using a differential scanning calorimeter.

[0078] Specifically, the glass transition temperature of the modified EVOH can be calculated by measuring with a differential scanning calorimeter under the following conditions. (a) Conditioning of the test specimen: After melting at 230°C for 1 minute, the sample is cooled to -30°C at a cooling rate of 10°C / min. (b) Analysis of glass transition temperature: The sample cooled in (a) is heated to 230°C at a heating rate of 10°C / min. (c) Calculation of glass transition temperature: From the DSC curve obtained in (b), the midpoint temperature of the stepwise change in the glass transition is calculated as the glass transition temperature.

[0079] The MFR (melt flow rate) of the modified EVOH is usually 0.5 to 100 g / 10 min, preferably 1 to 50 g / 10 min, and particularly preferably 3 to 35 g / 10 min. If the MFR is too high, the melt viscosity of the modified EVOH may be too low, making stable melt molding difficult, whereas if the MFR is too low, the melt viscosity of the modified EVOH may be too high, tending to reduce dispersibility. The MFR is an index of the degree of polymerization of EVOH, which is the main chain of the modified EVOH, and can be adjusted by the amount of polymerization initiator and the amount of solvent used when copolymerizing the monomers.

[0080] The flexural modulus of the modified EVOH is preferably 1 to 3000 MPa, more preferably 5 to 2500 MPa, further preferably 10 to 2000 MPa, and particularly preferably 30 to 1500 MPa. When the flexural modulus is within the above range, the effects of the present invention tend to be further enhanced. The flexural modulus can be measured based on ISO 178.

[0081] The melting point of the modified EVOH resin is preferably 40 to 200° C., more preferably 60 to 180° C., further preferably 80 to 160° C., and particularly preferably 100 to 140° C. If the melting point of the modified EVOH resin is too high, the flexibility tends to decrease. By having the melting point within the above range, the effects of the present invention tend to be further enhanced. Grafting of the aliphatic polyester weakens the intermolecular forces, such as hydrogen bonds between hydroxyl groups in the skeletal EVOH-based resin, so that as the modification rate in the modified EVOH-based resin increases, the melting point of the modified EVOH-based resin tends to decrease. The melting point of the modified EVOH-based resin can be measured using a differential scanning calorimeter.

[0082] The EVOH content in the EVOH layer is not particularly limited, but is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, particularly preferably 90% by mass or more, and especially preferably 95% by mass or more.

[0083] The EVOH layer may contain thermoplastic resins other than EVOH and other components, such as heat stabilizers, antioxidants, antistatic agents, colorants, UV absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc., within a range that does not impair the effects of the present invention (for example, usually 30% by mass or less of the EVOH layer, preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less). These additives may be used alone or in combination of two or more.

[0084] The thickness of the EVOH layer is usually from 10 to 1000 μm, preferably from 20 to 500 μm, and more preferably from 25 to 300 μm.

[0085] [Outer layer] The outer layer of the present multi-layer tube is preferably made of a material having a durometer hardness of D50 or less, and among these, those containing polyolefin resin or thermoplastic elastomer as the main component are preferred from the viewpoint of flexibility.

[0086] The polyolefin resin is not particularly limited, and examples thereof include polyethylene, copolymers of propylene and a small amount of other α-olefins (e.g., propylene-ethylene copolymer, propylene / 4-methyl-1-pentene copolymer), poly(4-methyl-1-pentene), polybutene-1, etc. Among these, polyethylene, particularly low-density polyethylene, is preferred from the viewpoint of flexibility.

[0087] Examples of the thermoplastic elastomer include thermoplastic polyurethane elastomers, thermoplastic polyamide elastomers, and thermoplastic olefin elastomers. These may be used alone or in combination of two or more. Among these, thermoplastic polyurethane elastomers and thermoplastic olefin elastomers are preferred.

[0088] [Thermoplastic polyurethane elastomer] The thermoplastic polyurethane elastomer is obtained by the reaction of a polymeric diol, an organic diisocyanate and a chain extender.

[0089] The polymer diol may be a diol having a number average molecular weight of 1000 to 6000, such as a polyester diol, a polyether diol, or a polycarbonate diol. These may be used alone or in combination of two or more. Among these, a polyether diol is preferred. That is, the thermoplastic polyurethane elastomer is preferably a polyether-based thermoplastic polyurethane elastomer. The number average molecular weight of the polymer diol is a number average molecular weight calculated based on a hydroxyl value measured by SITE in accordance with JIS K1557.

[0090] Examples of the polyester diol include polyester diols obtained by reacting at least one dicarboxylic acid component selected from aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and their ester-forming derivatives with a low molecular weight diol, polyester diols obtained by ring-opening polymerization of lactone, etc. These may be used alone or in combination of two or more kinds.

[0091] Specific examples of polyester diols include polyester diols obtained by polycondensation reaction of aliphatic dicarboxylic acids having 6 to 12 carbon atoms, such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid, and ester-forming derivatives thereof, with aliphatic diols having 2 to 10 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, and 2-methyl-1,8-octanediol, polycaprolactone diols, and polyvalerolactone diols.

[0092] Examples of the polyether diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. These may be used alone or in combination of two or more kinds.

[0093] The polycarbonate diol may be, for example, a polycarbonate diol obtained by reacting an aliphatic diol such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or 1,8-octanediol with a carbonate ester such as diphenyl carbonate or alkyl carbonate, or with phosgene. These may be used alone or in combination of two or more kinds.

[0094] The diisocyanate is not particularly limited, but examples thereof include aromatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates each having a molecular weight of 500 or less. Specific examples include 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate (4,4'-dicyclohexylmethane diisocyanate), isophorone diisocyanate, hexamethylene diisocyanate, etc. These may be used alone or in combination of two or more kinds.

[0095] The chain extender may be a chain extender that has been conventionally used in the production of thermoplastic polyurethane elastomers, and examples of such include aliphatic diols, alicyclic diols, and aromatic diols. These may be used alone or in combination of two or more. Among these, preferred chain extenders include diols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,3-propanediol, 1,6-hexanediol, neopentyl glycol, 1,9-nonanediol, cyclohexanediol, and 1,4-bis(β-hydroxyethoxy)benzene.

[0096] The thermoplastic polyurethane elastomer is preferably a thermoplastic polyurethane elastomer obtained by reacting a polymer diol, a chain extender, and an organic diisocyanate in a ratio of polymer diol:chain extender=1:0.2-8 (molar ratio) and a total number of moles of polymer diol and chain extender:number of moles of organic diisocyanate=1:0.98-1.04. By using such a thermoplastic polyurethane elastomer, there is little sudden increase in melt viscosity during melt molding such as extrusion molding and injection molding, and the heat resistance tends to be excellent.

[0097] The method for producing the thermoplastic polyurethane elastomer is not particularly limited, and the thermoplastic polyurethane elastomer may be produced by any of a prepolymer method and a one-shot method using the above-mentioned polymer diol, organic diisocyanate, and chain extender, and utilizing a known urethane reaction.

[0098] [Thermoplastic polyamide elastomer] The thermoplastic polyamide elastomer is usually a block copolymer having polyamide (nylon 6, nylon 66, nylon 11, nylon 12, etc.) as a hard segment and polyether or polyester as a soft segment, i.e., a polyether-polyamide type thermoplastic polyamide elastomer or a polyester-polyamide type thermoplastic polyamide elastomer.

[0099] The polyether-polyamide type thermoplastic polyamide elastomer is generally represented by the following general formula (5).

[0100] [ka]

[0101] The polyether-polyamide type thermoplastic polyamide elastomer represented by the general formula (5) can be produced, for example, by polycondensing a salt of a diamine and a dicarboxylic acid, lactams or aminodicarboxylic acid for constituting a polyamide block (hard segment), and a polyoxyalkylene glycol such as polyoxyethylene glycol or polyoxypropylene glycol for constituting a polyether block (soft segment) in the presence of a dicarboxylic acid such as adipic acid. In the above reaction, a dicarboxylic acid such as adipic acid acts as a molecular weight regulator when forming a polyamide oligomer, and also as a polymerizing agent by forming a polyether diol bond.

[0102] [Thermoplastic polyolefin elastomer] Examples of the thermoplastic polyolefin elastomer include polymers derived mainly from one or more α-olefin monomers, such as polyethylene elastomers and polypropylene elastomers.

[0103] The polyethylene elastomer refers to an elastomer containing structural units derived from ethylene as a main component. The polyethylene elastomer may also contain structural units derived from elements other than ethylene. Examples of the structural units derived from other than ethylene include structural units derived from α-olefins such as propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-nonene, 1-decene, etc. Among these, from the viewpoints of processability and tear strength, ethylene / propylene random copolymers and ethylene / butene random copolymers are preferred.

[0104] The polypropylene elastomer refers to an elastomer containing structural units derived from propylene as a main component. The polypropylene elastomer may contain structural units derived from other than propylene. Examples of the structural units derived from other than propylene include structural units derived from α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-nonene, and 1-decene.

[0105] Specific examples of polypropylene elastomers include homopolypropylene, propylene / ethylene random copolymers, propylene / ethylene block copolymers, propylene / butene random copolymers, propylene / ethylene / butene random copolymers, propylene / pentene random copolymers, propylene / hexene random copolymers, propylene / octene random copolymers, propylene / ethylene / pentene random copolymers, propylene / ethylene / hexene random copolymers, etc. Among these, from the viewpoints of processability and heat resistance, propylene / ethylene random copolymers and propylene / butene random copolymers are preferred, and from the viewpoint of tear strength, propylene / ethylene random copolymers are more preferred.

[0106] The polyolefin resin and thermoplastic elastomer usually have a durometer hardness of D50 or less, preferably D45 or less, more preferably D40 or less, and particularly preferably D30 or less. Since the lower the hardness, the higher the vibration damping property when laminated, no lower limit is set, but in practical use, the durometer hardness is usually A30 or more, preferably A50 or more. Since the durometer hardness of the thermoplastic elastomer is D50 or less, the present multilayer tube tends to have excellent flexibility. The durometer hardness is measured using a durometer hardness tester. Since the value of the durometer hardness changes over time, the value is read within 1 second after the pressurized surface is in close contact. The above measurement is performed three times, and the average value is taken as the durometer hardness.

[0107] The outer layer may contain thermoplastic resins other than thermoplastic elastomers and other components, such as heat stabilizers, antioxidants, antistatic agents, colorants, UV absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, drying agents, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc., within a range that does not impair the effects of the present invention (for example, usually 30% by mass or less of the outer layer, preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less). These additives may be used alone or in combination of two or more.

[0108] The thickness of the outer layer is usually 100 to 4000 μm, preferably 150 to 2000 μm, and more preferably 200 to 1000 μm. When there are two or more outer layers, it is preferable that the thickness of each outer layer is within the above range.

[0109] [Inner layer] The inner layer of the present multi-layer tube preferably contains a fluororesin as a main component from the viewpoints of chemical resistance and water repellency.

[0110] The fluororesin is not particularly limited, but examples thereof include ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), etc. These may be used alone or in combination of two or more. Among them, ethylene-tetrafluoroethylene copolymer (ETFE) is preferred.

[0111] The inner layer may contain thermoplastic resins other than fluororesins and other components, such as heat stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, drying agents, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc., within a range that does not impair the effects of the present invention (for example, usually 30% by mass or less of the inner layer, preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less). These additives may be used alone or in combination of two or more.

[0112] The thickness of the inner layer is usually 10 to 200 μm, preferably 15 to 100 μm, and more preferably 20 to 50 μm. When there are two or more inner layers, it is preferable that the thickness of each inner layer is within the above range.

[0113] [Adhesive resin layer] The adhesive resin layer of the present multi-layer tube preferably contains an adhesive resin as a main component. As the adhesive resin, known resins can be used, and examples thereof include modified polyolefin polymers containing carboxy groups obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to a polyolefin resin by addition reaction, graft reaction, or the like.

[0114] Specific examples of modified polyolefin polymers containing a carboxy group include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene (block and random) copolymers, maleic anhydride-modified ethylene-ethyl acrylate copolymers, maleic anhydride-modified ethylene-vinyl acetate copolymers, maleic anhydride-modified polycyclic olefin resins, and maleic anhydride-modified polyolefin resins. These may be used alone or in combination of two or more. Among these, maleic anhydride-modified polyethylene is preferred.

[0115] In addition, the adhesive resin layer may contain thermoplastic resins other than the adhesive resin and other components, such as heat stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc., within a range that does not impair the effects of the present invention (for example, usually 30% by mass or less of the adhesive resin layer, preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less). These additives may be used alone or in combination of two or more.

[0116] The thickness of the adhesive resin layer is usually 10 to 200 μm, preferably 15 to 100 μm, and more preferably 20 to 50 μm. When there are two or more adhesive resin layers, it is preferable that the thickness of each adhesive resin layer is within the above range.

[0117] [Method for manufacturing multi-layer tube] The method for producing the present multi-layer tube is not particularly limited, but extrusion molding is preferred because it allows multiple layers to be molded simultaneously and is excellent in productivity and interlayer adhesion.

[0118] Furthermore, the present multi-layer tube may be subjected to a stretching treatment, a chemical treatment, a plasma treatment, an electronic cross-linking treatment, or the like, if necessary.

[0119] The present multilayer tube has excellent gas barrier properties, solvent resistance, flexibility, kink resistance, and vibration damping properties, and can therefore be suitably used as an industrial tube (for example, for transporting solvents, ink, etc.). EXAMPLES

[0120] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are based on mass.

[0121] Prior to the examples, the following materials were prepared. [EVOH] Modified EVOH1 [modified EVOH having a structural unit represented by chemical formula (1)]: ethylene content 32 mol%, saponification degree 99.7%, modification rate 5.7 mol%, average chain length of graft chain (aliphatic polyester unit) 2.2, glass transition temperature 22°C, MFR 35g / 10min (210°C, load 2.16kg), melting point 130°C, flexural modulus 100MPa Modified EVOH2 [modified EVOH having a structural unit represented by chemical formula (1)]: ethylene content 32 mol%, saponification degree 99.7%, modification rate 4.5 mol%, average chain length of graft chains (aliphatic polyester units) 1.9, glass transition temperature 26°C, MFR 25g / 10min (210°C, load 2.16kg), melting point 145°C, flexural modulus 1000MPa EVOH1: Ethylene content 32mol%, Saponification degree 99.7%, Glass transition temperature 61℃, MFR 12g / 10min (210℃, load 2.16kg), Melting point 183℃, Flexural modulus 4350MPa EVOH2: Ethylene content 44mol%, Saponification degree 99.7%, Glass transition temperature 55℃, MFR 12g / 10min (210℃, load 2.16kg), Melting point 164℃, Flexural modulus 3300MPa [Thermoplastic elastomer] Thermoplastic polyurethane elastomer (TPU): BASF "1190A10" Thermoplastic polyolefin elastomer (POE): Mitsubishi Chemical Corporation "TX503N" [Thermoplastic resin] Homopolypropylene (hPP): Japan Polypropylene "FB3B" [Fluororesin] Ethylene-tetrafluoroethylene copolymer (ETFE): AGC "LH-8000" [Adhesive resin] Polyester adhesive resin (PES): Mitsubishi Chemical Corporation "GQ131" Polypropylene adhesive resin (PP): Mitsubishi Chemical Corporation "P674V"

[0122] <Example 1> Coextrusion molding was carried out under the following molding conditions so as to obtain the composition and layer structure shown in Table 1 below, to mold a multi-layer tube. [Molding conditions] ·Outer layer 1 (φ30mm): C1 / C2 / C3 / C4 / H=210 / 215 / 215 / 215 / 215℃ ·Outer layer 2 (φ45mm): C1 / C2 / C3 / C4 / H=210 / 215 / 215 / 215 / 215℃ ·Middle layer (φ20mm): C1 / C2 / C3 / C4 / H=210 / 215 / 215 / 215 / 215℃ ·EVOH layer (φ20mm): C1 / C2 / C3 / H=200 / 215 / 215 / 200℃ Inner layer (φ20mm): C1 / C2 / C3 / H=240 / 270 / 265 / 260℃ Die temperature: D1 / D2 / D3=216 / 210 / 200℃ -Thickness of each layer: 225 / 625 / 25 / 100 / 25μm, Total 1000μm The outer diameter of the tube is 7mm, the inner diameter is 5mm (tube thickness 1mm) Here, C1 to C4 refer to the temperature regulators provided in the cylinder of the extruder, H refers to the temperature regulator of the die attached to the tip (head) of the extruder, and D1 to D3 refer to the temperature regulators provided upstream of the die.

[0123] <Examples 2 and 3, Comparative Examples 1 to 4> A multi-layer tube was molded in the same manner as in Example 1, except that the composition and layer structure were as shown in Table 1 below.

[0124] The following evaluations of durometer hardness, vibration damping, and minimum bending radius were carried out using the obtained multilayer tubes of Examples 1 to 3 and Comparative Examples 1 to 4. The results are shown in Table 1 below.

[0125] [Durometer hardness] The multi-layer tube was cut in half in the circumferential direction with a razor to produce a tube cut into a semicircular shape. The cut tube was spread out and both ends were fixed with tape, and then the hardness was measured from the outer layer side using a durometer hardness tester "Asker Rubber Hardness Tester Type A" or "Asker Rubber Hardness Tester Type D" (manufactured by Kobunshi Keiki Co., Ltd.). Since the durometer hardness value changes over time, in this measurement, the value was read within 1 second after the pressure surface was in close contact. The above measurement was performed three times, and the average value was recorded.

[0126] [Vibration Damping] A multi-layer tube with a marker attached to the center was clamped at both ends with a gap of 30 cm. The multi-layer tube was vibrated and the marker was photographed with a high-speed camera. The logarithmic damping rate (δ) of the multi-layer tube was calculated from the vibration of the marker using the following formula, and the loss factor (η) was calculated using the following formula. A larger value indicates better vibration damping. In the following formula, a is the amplitude, a is the n represents the nth amplitude at time tn. Similarly, the amplitudes were measured for n+1, n+2, and so on, and the logarithmic decay rate δ was calculated for the n+mth amplitude. TIFF2025039323000009.tif28128

[0127] [Minimum bending radius] A multi-layer tube with a length of 1m was held at both ends and bent in a twisting motion, and the radius just before it broke was measured as the minimum bending radius. The smaller the value, the better the kink resistance.

[0128] [Table 1]

[0129] From the results in Table 1, the multilayer tubes of Examples 1 to 3, which have an EVOH layer containing a specific modified EVOH and have a durometer hardness of D50 or less measured from the outer layer side, were excellent in vibration damping property and kink resistance. Furthermore, a multi-layer tube having a durometer hardness of more than D50 measured from the outer layer side was inferior in vibration damping and kink resistance even if it had an EVOH layer containing a specific modified EVOH. [Industrial Applicability]

[0130] The multilayer tube of the present invention is excellent in gas barrier properties, solvent resistance, flexibility, kink resistance and vibration damping properties, and can therefore be suitably used as an industrial tube (for example, for transporting solvents, ink, etc.).

Claims

1. A multi-layer tube having a layer containing an ethylene-vinyl alcohol copolymer, The ethylene-vinyl alcohol copolymer contains a modified ethylene-vinyl alcohol copolymer having a structural unit represented by the following chemical formula (1): The multi-layer tube has a durometer hardness of D50 or less as measured from the outer layer side of the multi-layer tube. 【Chemistry 1】

2. 2. The multi-layer tube according to claim 1, wherein the heteroatom for X in the chemical formula (1) is any one selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom.

3. 3. The multi-layer tube according to claim 1, wherein the minimum bending radius of the multi-layer tube is 20 mm or less.

4. 3. The multi-layer tube according to claim 1, wherein the loss factor of the multi-layer tube is 0.04 or more.

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