Tube and manufacturing method thereof

Abstract

Provided is a pipe in which residual stress is released while maintaining flexibility. A pipe containing a thermoplastic resin composition having a sea-island structure formed from an island phase containing a rubber and a sea phase containing a thermoplastic resin, the thermoplastic resin composition containing 100 parts by mass of the rubber and 30-120 parts by mass of the thermoplastic resin, the thickness of the pipe being 0.1 mm or more, in a cross-section obtained by cutting the tube with a plane including the central axis of the tube, the circularity of the island phase in a cross-section from the inner surface of the tube to 5 [mu] m in the thickness direction is referred to as circularity (inner surface), and the circularity of the island phase in a cross-section from the center of the tube to 5 [mu] m in the thickness direction is referred to as circularity (center). The circularity (inner surface) and circularity (center) satisfy formula (1) and formula (2): 0.35 < = circularity (inner surface) < = 1.0 (1); (2) 60 < = circularity (inner surface) / circularity (center) * 100 < = 120.

Description

Technical Field

[0001] This invention relates to pipes and methods of manufacturing them. More specifically, this invention relates to pipes with low residual stress and methods of manufacturing them. Background Technology

[0002] Japanese Patent Application Publication No. 2020-105284 (Patent Document 1) discloses a refrigerant delivery hose that uses a thermoplastic resin composition consisting of a matrix containing a thermoplastic resin and a region containing rubber dispersed in the matrix, which is extruded into the inner layer of a refrigerant delivery hose for an automobile air conditioning system.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-105284 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, the inner tube of the refrigerant delivery hose disclosed in Patent Document 1 suffers from residual stress. This is undesirable under the hot environment during hose use. The present invention provides a hose that relieves residual stress while maintaining flexibility.

[0008] Problem-solving methods

[0009] The present invention (I) is a pipe containing a thermoplastic resin composition having an island structure, said island structure being formed by an island phase containing rubber and a sea phase containing thermoplastic resin.

[0010] The thermoplastic resin composition contains 100 parts by weight of rubber and 30-120 parts by weight of thermoplastic resin.

[0011] The thickness of the tube is 0.1mm or more.

[0012] In a cross-section obtained by cutting the tube with a plane containing the tube's central axis, the roundness of the island phase in the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm is called roundness (inner surface), and the roundness of the island phase in the cross-section extending from the center of the tube's thickness direction to 5 μm is called roundness (center). When roundness (inner surface) and roundness (center) satisfy equations (1) and (2):

[0013] 0.35≤circularity (inner surface)≤1.0 (1)

[0014] 60≤circularity (inner surface) / circularity (center)×100≤120 (2).

[0015] The present invention (II) is a method for manufacturing the tube of the present invention (I), characterized in that the method includes a step of extruding a thermoplastic resin composition into a tubular shape by pull extrusion molding.

[0016] The present invention includes the following embodiments.

[0017] [1]. A pipe comprising a thermoplastic resin composition having an island structure, said island structure being formed of an island phase containing rubber and an ocean phase containing thermoplastic resin.

[0018] The thermoplastic resin composition contains 100 parts by weight of rubber and 30-120 parts by weight of thermoplastic resin.

[0019] The thickness of the tube is 0.1mm or more.

[0020] In a cross-section obtained by cutting the tube with a plane containing the tube's central axis, the roundness of the island phase in the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm is called roundness (inner surface), and the roundness of the island phase in the cross-section extending from the center of the tube's thickness direction to 5 μm is called roundness (center). When roundness (inner surface) and roundness (center) satisfy equations (1) and (2):

[0021] 0.35≤circularity (inner surface)≤1.0 (1)

[0022] 60≤circularity (inner surface) / circularity (center)×100≤120 (2).

[0023] [2]. As described in [1], in a cross-section obtained by cutting the tube with a plane containing the central axis of the tube, the aspect ratio of the island phase in the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm is called the aspect ratio (inner surface), and the aspect ratio of the island phase in the cross-section extending from the center of the tube in the thickness direction to 5 μm is called the aspect ratio (center). The aspect ratio (inner surface) and the aspect ratio (center) satisfy equations (3) and (4):

[0024] 1≤ aspect ratio (inner surface)≤3 (3)

[0025] 90≤ aspect ratio (inner surface) / aspect ratio (center) × 100≤150 (4).

[0026] [3]. The tube as described in [1] or [2] contains an elastomer with a polyisobutylene backbone.

[0027] [4]. The tube described in [3] has an elastomer with a polyisobutylene backbone selected from at least one of butyl rubber, halogenated butyl rubber, isobutylene-p-methylstyrene copolymer rubber, halogenated isobutylene-p-methylstyrene copolymer rubber and styrene-isobutylene-styrene block copolymer.

[0028] [5]. The tube as described in any one of [1] to [4] contains polyamide in its thermoplastic resin.

[0029] [6]. The tube as described in [5], wherein the polyamide is at least one selected from polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 6 / 66 copolymer, polyamide 6 / 12 copolymer, polyamide 46, polyamide 6T, polyamide 9T and polyamide MXD6.

[0030] [7]. The tube as described in any one of [1] to [6] has cross-linked rubber.

[0031] [8]. A method for manufacturing a tube according to any one of [1] to [7], the method comprising a step of extruding a thermoplastic resin composition into a tubular shape by pull-out extrusion molding.

[0032] Invention Effects

[0033] The tube of this invention has low residual stress. Attached Figure Description

[0034] Figure 1 This is a scanning probe microscope image of the cross-section of the tube in Example 1.

[0035] Figure 2 This is a scanning probe microscope image of the cross-section of the tube in Example 2.

[0036] Figure 3 This is a scanning probe microscope image of the cross-section of the tube in Example 3.

[0037] Figure 4 This is a scanning probe microscope image of the cross-section of the tube in Example 5.

[0038] Figure 5 This is a scanning probe microscope image of the cross-section of the tube in Example 6.

[0039] Figure 6 This is a scanning probe microscope image of the cross-section of the tube in Example 7.

[0040] Figure 7 This is a scanning probe microscope image of the cross-section of the tube in Comparative Example 1.

[0041] Figure 8 It is a diagram showing the cross-section of the tube used to take microscope photographs.

[0042] Figure 9 This is a diagram used to illustrate the method of the curling test.

[0043] Figure 10It is a schematic cross-sectional view of a die used for pull-out extrusion molding.

[0044] Figure 11 It is a schematic cross-sectional view of a die used for filling extrusion molding. Detailed Implementation

[0045] This invention relates to a pipe containing a thermoplastic resin composition having an island structure, said island structure being formed by an island phase containing rubber and a sea phase containing thermoplastic resin.

[0046] The thermoplastic resin composition contains 100 parts by weight of rubber and 30-120 parts by weight of thermoplastic resin.

[0047] The thickness of the tube is 0.1mm or more.

[0048] In a cross-section obtained by cutting the tube with a plane containing the tube's central axis, the roundness of the island phase in the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm is called roundness (inner surface), and the roundness of the island phase in the cross-section extending from the center of the tube's thickness direction to 5 μm is called roundness (center). When roundness (inner surface) and roundness (center) satisfy equations (1) and (2):

[0049] 0.35≤circularity (inner surface)≤1.0 (1)

[0050] 60≤circularity (inner surface) / circularity (center)×100≤120 (2).

[0051] Figure 8 This is a diagram showing a cross-section of tube 1, from which a microscope image will be taken. Figure 8 a shows the cross-section of pipe 1 when it is cut with a plane passing through the central axis 2 of pipe 1. Figure 8 b is used Figure 8 An enlarged view of the part enclosed by the circle 'a'. Figure 8 In the diagram, 3 represents the inner surface of the tube, 4 represents the outer surface of the tube, 5 represents the center line along the thickness direction of the tube, 6 represents the range from the inner surface of the tube along the thickness direction up to 5 μm, and 7 represents the range within 5 μm from the center of the tube's thickness direction. The range 7 within 5 μm from the center of the tube's thickness direction, in other words, refers to the area enclosed by line 8 extending 2.5 μm outward from line 5 (the center line along the thickness direction) and line 9 extending 2.5 μm inward from line 5 (the center line along the thickness direction).

[0052] In the present invention, when the pipe 1 is cut by a plane containing the central axis 2, the roundness of the island phase in the cross section from the inner surface 3 of the pipe along the thickness direction to 5 μm is called the roundness (inner surface), and the roundness of the island phase in the cross section of the pipe within the central 5 μm range 7 of the thickness direction is called the roundness (center), the roundness (inner surface) and roundness (center) satisfy equations (1) and (2):

[0053] 0.35≤circularity (inner surface)≤1.0 (1)

[0054] 60≤circularity (inner surface) / circularity (center)×100≤120 (2).

[0055] The tube of the present invention preferably satisfies formula (1'):

[0056] 0.36≤circularity (inner surface)≤1.0・・・(1')

[0057] The preferred expression satisfies (1”):

[0058] 0.38≤circularity (inner surface)≤1.0・・・(1”).

[0059] The tube of the present invention preferably satisfies formula (2'):

[0060] 65≤circularity (inner surface) / circularity (center)×100≤120…(2')

[0061] More preferably, satisfying formula (2”):

[0062] 70≤circularity (inner surface) / circularity (center)×100≤115・・・(2”).

[0063] By satisfying equations (1) and (2), the residual stress of the tube is less, and when the tube is used as the inner layer of a hose for refrigerant delivery, fewer cracks occur.

[0064] Here, the so-called circularity is defined by equation (5) when S represents the area of ​​an island phase and L represents the perimeter of the island phase.

[0065] Circularity = 4πS / L 2 ・・・(5)

[0066] The circularity of a perfect circle is 1. The closer the circularity is to 1, the closer the shape of the island phase is to a perfect circle.

[0067] In the present invention, when the pipe 1 is cut with a plane containing the central axis 2 of the pipe 1, the aspect ratio of the island phase in the cross section from the inner surface 3 of the pipe 1 along the thickness direction to 5 μm is called the aspect ratio (inner surface), and the aspect ratio of the island phase in the cross section of the central 5 μm range 7 of the thickness direction of the pipe is called the aspect ratio (center), the aspect ratio (inner surface) and the aspect ratio (center) preferably satisfy equations (3) and (4):

[0068] 1≤ aspect ratio (inner surface)≤3 (3)

[0069] 90≤ aspect ratio (inner surface) / aspect ratio (center) × 100≤150 (4).

[0070] The tube of the present invention more preferably satisfies formula (3'):

[0071] 1≤ aspect ratio (inner surface)≤2.9…(3')

[0072] Therefore, the preferred option is to satisfy equation (3”):

[0073] 1≤ aspect ratio (inner surface)≤2.85・・・(3”).

[0074] The tube of the present invention more preferably satisfies formula (4'):

[0075] 90≤ aspect ratio (inner surface) / aspect ratio (center) × 100≤148…(4’)

[0076] Therefore, the preferred option is to satisfy equation (4”):

[0077] 100≤ aspect ratio (inner surface) / aspect ratio (center) × 100≤145・・・(4”)。

[0078] By satisfying equations (3) and (4), the tube has less residual stress, and when the tube is used as the inner layer of a hose for refrigerant delivery, fewer cracks occur.

[0079] Here, aspect ratio refers to the ratio of the major axis to the minor axis calculated from the major and minor axes of an island phase approximated by an ellipse. Ellipse approximation can be performed using the Fit Ellipse feature in the image processing software ImgageJ.

[0080] The cross-section obtained by cutting tube 1 with a plane passing through the central axis 2 of tube 1 can be observed using an atomic force microscope (AFM) as a scanning probe microscope (SPM). There are no particular limitations on the measurement mode, but tapping mode is preferred. Alternatively, observation can be performed using an electron microscope (scanning electron microscope (SEM), transmission electron microscope (TEM), etc.).

[0081] A cross-section measuring 5 μm in length and 5 μm in width was photographed using a microscope. The resulting cross-sectional image was then binarized using the image processing software ImageJ, with the peaks and the midpoint of the peaks as boundaries. Images with a wavelength of 10000 nm in the binarized image were then analyzed. 2 The circularity of all island phases with the above areas was calculated, and the average value was obtained. Additionally, for phases with a diameter of 10000 nm... 2 For all islands with the above area, approximate them with an ellipse, find the major and minor axes, calculate the aspect ratio (major axis / minor axis), and find the average value.

[0082] Figure 1 A scanning probe microscope image showing the cross-section of the tube in Example 1. Figure 1 (a) A scanning probe microscope image showing a cross-section extending from the inner surface of the tube in Example 1 along the thickness direction to 5 μm. Figure 1 (b) A scanning probe microscope image of a cross section in the thickness direction of the tube of Example 1, within a 5 μm range from the center.

[0083] same, Figure 2 Example 2 Figure 3 Example 3 Figure 4 Example 5 Figure 5 Example 6 Figure 6 Example 7 is shown. Figure 7 The images shown are scanning probe microscope images of the cross-section of the tube in Comparative Example 1. (a) is a scanning probe microscope image of the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm. (b) is a scanning probe microscope image of the cross-section extending 5 μm from the center of the tube in the thickness direction.

[0084] In conventional tubes, the island phases on the inner surface are stretched. As a result, the roundness of the island phases near the inner surface is smaller than that of the island phases at the center in the thickness direction, and the aspect ratio of the island phases near the inner surface is higher than that of the island phases at the center in the thickness direction (refer to...). Figure 7 The residual stress can be attributed to morphological differences near the inner surface and at the center of the thickness direction. Hose with residual stress is at risk of shape deformation when used at high temperatures.

[0085] The tube of the present invention comprises a thermoplastic resin composition having an island structure consisting of an island phase containing rubber and an ocean phase containing thermoplastic resin.

[0086] The thermoplastic resin composition constituting the tube of the present invention has an island structure formed by island phases and marine phases. By having an island structure, a large amount of rubber can be incorporated while maintaining gas barrier properties, thus achieving a balance between flexibility and gas barrier properties.

[0087] The island phase contains rubber.

[0088] There are no restrictions on the type of rubber, but it is preferable to include an elastomer with a polyisobutylene backbone. The polyisobutylene backbone refers to the chemical structure formed by the polymerization of multiple isobutylene compounds, specifically a structure represented by -〔-CH2-C(CH3)2-]n- (where n is an integer greater than or equal to 2). By including an elastomer with a polyisobutylene backbone in the rubber, both flexibility and gas barrier properties can be achieved.

[0089] The elastomer having a polyisobutylene backbone is not limited to having a polyisobutylene backbone, but is preferably selected from at least one of butyl rubber (IIR), halogenated butyl rubber, isobutylene-p-methylstyrene copolymer rubber (IPMS), halogenated isobutylene-p-methylstyrene copolymer rubber and styrene-isobutylene-styrene block copolymer (SIBS), and more preferably is brominated isobutylene-p-methylstyrene copolymer rubber (BIMS).

[0090] Within the scope that does not impair the effects of the present invention, the island phase may contain components other than rubber.

[0091] Marine facies contain thermoplastic resins.

[0092] Thermoplastic resins include, but are not limited to, polyamides. By incorporating polyamides into thermoplastic resins, both flexibility and gas barrier properties can be achieved.

[0093] The polyamide is preferably selected from at least one of polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 6 / 66 copolymer, polyamide 6 / 12 copolymer, polyamide 46, polyamide 6T, polyamide 9T and polyamide MXD6.

[0094] Without hindering the effects of the present invention, the marine phase may contain components other than thermoplastic resin.

[0095] The thermoplastic resin composition comprises 100 parts by weight of rubber and 30 to 120 parts by weight of thermoplastic resin. The content of thermoplastic resin in the thermoplastic resin composition is 30 to 120 parts by weight, preferably 30 to 115 parts by weight, based on 100 parts by weight of rubber. By ensuring that the content of rubber and thermoplastic resin is within this range, it is possible to ensure that the rubber is dispersed in an island-like structure, thus ensuring softness and gas barrier properties.

[0096] Thermoplastic resin compositions may contain components other than rubber and thermoplastic resins. Examples of components other than rubber and thermoplastic resins include resins other than thermoplastic resins, crosslinking agents, anti-aging agents, viscosity stabilizers, processing aids, etc.

[0097] The thermoplastic resin composition preferably contains an anti-aging agent. By including an anti-aging agent in the thermoplastic resin composition, its heat aging resistance is improved.

[0098] Examples of anti-aging agents include phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents.

[0099] Phenylenediamine-based anti-aging agents refer to anti-aging agents with an aromatic ring in their molecular structure having two secondary amine substituents. Preferably, they are selected from at least one of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N,N'-diphenyl-p-phenylenediamine, more preferably N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine.

[0100] Quinoline-based anti-aging agents refer to anti-aging agents with a quinoline skeleton in their molecular structure, preferably 2,2,4-trimethyl-1,2-dihydroquinoline polymers.

[0101] Based on 100 parts by weight of the total weight of rubber and thermoplastic resin, the content of the anti-aging agent in the thermoplastic resin composition is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5.0 parts by weight.

[0102] Phenylenediamine-based and quinoline-based anti-aging agents also function as crosslinking agents for rubber.

[0103] The thermoplastic resin composition preferably contains a viscosity stabilizer. By containing a viscosity stabilizer, the increase in viscosity is suppressed during the extrusion molding of the thermoplastic resin composition, which can effectively reduce the generation of residues and thus improve processability.

[0104] Examples of viscosity stabilizers include divalent metal oxides, ammonium salts, and carboxylates.

[0105] Examples of divalent metal oxides include zinc oxide, magnesium oxide, copper oxide, calcium oxide, and iron oxide, with zinc oxide or magnesium oxide being preferred, and zinc oxide being even more preferred.

[0106] Ammonium salts include ammonium carbonate, ammonium bicarbonate, ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate, ammonium acetate, and alkylammonium salts.

[0107] Examples of carboxylates include sodium acetate, potassium acetate, zinc acetate, copper acetate, sodium oxalate, ammonium oxalate, calcium oxalate, and iron oxalate.

[0108] Zinc oxide is the preferred viscosity stabilizer.

[0109] The content of viscosity stabilizer in the thermoplastic resin composition is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the total weight of rubber and thermoplastic resin.

[0110] The viscosity stabilizer is preferably contained in the matrix at 50% by mass or more. By containing 50% by mass or more of the viscosity stabilizer in the matrix, the increase in viscosity can be suppressed during the extrusion molding of the thermoplastic resin composition, the generation of residues can be effectively reduced, and thus the processability is good.

[0111] Thermoplastic resin compositions preferably contain processing aids. Processing aids help improve the extrusion processability of the thermoplastic resin compositions.

[0112] As processing aids, examples include fatty acids, fatty acid metal salts, fatty acid esters, and fatty acid amides.

[0113] As fatty acids, examples include stearic acid, palmitic acid, lauric acid, oleic acid, and linoleic acid, with stearic acid being the preferred choice.

[0114] As fatty acid metal salts, examples include calcium stearate, potassium stearate, zinc stearate, magnesium stearate, and sodium stearate, with calcium stearate being the preferred choice.

[0115] Examples of fatty acid esters include glyceryl monostearate, sorbitol stearate, stearyl stearate, and ethylene glycol distearate.

[0116] Examples of fatty acid amides include stearic acid monoamide, oleic acid monoamide, and ethylene distearate amide.

[0117] The content of processing aids in the thermoplastic resin composition is preferably 0.2 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the total weight of rubber and thermoplastic resin.

[0118] The rubber is preferably already cross-linked. Cross-linking the rubber can improve fatigue resistance. To cross-link the rubber, a cross-linking agent can be incorporated into the thermoplastic resin composition.

[0119] Crosslinking agents include phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents, among which phenylenediamine-based anti-aging agents are preferred.

[0120] Based on 100 parts by weight of rubber, the content of crosslinking agent is preferably 1.0 to 10 parts by weight, more preferably 1.0 to 6.0 parts by weight.

[0121] There are no particular limitations on the manufacturing method of the tube of the present invention, and any known general manufacturing method can be used. Specifically, well-known extrusion molding or draw extrusion molding methods, which are known as extrusion molding methods for wires and the like, can be used.

[0122] By controlling extrusion conditions, such as extrusion set temperature (die temperature), extrusion speed (extruder screw speed), tube wall thickness, tube inner diameter, etc., the desired roundness (inner surface), roundness (center), aspect ratio (inner surface), and aspect ratio (center) can be obtained.

[0123] The extrusion temperature for thermoplastic resin compositions can be, for example, above 230°C and below 260°C. If it is below 230°C, the processability will deteriorate due to the increased extrusion torque. If it is above 260°C, scorching may occur during residence in the extruder, and the appearance may deteriorate.

[0124] The screw speed during the extrusion of thermoplastic resin compositions varies depending on the size of the extruder and the type of screw. For example, for a 40mm Φ single-screw extruder, the speed can be set between 8 rpm and 50 rpm. If the speed is below 8 rpm, the material will deteriorate due to the longer residence time. If the speed is above 50 rpm, the material will deteriorate due to excessive shear heating.

[0125] This invention (II) relates to a method for manufacturing the tube of this invention (I). The method of this invention (II) is characterized by comprising a step of extruding a thermoplastic resin composition into a tubular shape by pull extrusion molding.

[0126] Figure 10 A schematic cross-sectional view of the die 10 for pull-out extrusion molding is shown.

[0127] Figure 11 A schematic cross-sectional view of the die 11 for filling extrusion molding is shown.

[0128] like Figure 10 As shown, pull-out extrusion molding is a molding method in which the core material 12 and the molten thermoplastic resin composition 13 come into contact with the outside of the mold 10 after leaving the die head 14.

[0129] On the other hand, full extrusion molding is a molding method characterized by the core material 12 and the molten thermoplastic resin composition 13 being in contact under pressure within the die head 14.

[0130] The outer diameter of the core material 12 is, for example, 8 mm or more and 25 mm or less.

[0131] Pull-out extrusion molding can use internally compressed air instead of a core material, or it can be done without it. Figure 10 The mold shown.

[0132] The draw ratio of the cross-sectional area in draw extrusion molding is preferably 1 or more and 100 or less. If it is within the preferred range, a sufficiently productive molding speed can be obtained, and the mechanical properties are good.

[0133] The pull-out balance for pull-out extrusion molding is preferably 1.00 or higher and 1.20 or lower. If it is within the preferred range, the dimensional stability during molding is good.

[0134] The cross-sectional area pull-off rate and pull-off balance are defined by equations (6) and (7).

[0135] Cross-sectional area drawdown ratio = (D d 2 -D t 2 ) / (D o 2 -D i 2 )・・・(6)

[0136] Pull-down balance = (D) d / D t ) / (D o / D i )・・・(7)

[0137] Among them, D d : Die opening diameter

[0138] D t outer diameter of the pin

[0139] D o : Tube outer diameter

[0140] D i : Tube inner diameter (outer diameter of core material)

[0141] The tube of the present invention is not limited to any particular application, but can be used as the inner layer of a rubber hose. Examples of rubber hoses include those for refrigerant delivery, but the invention is not limited to these.

[0142] As specific examples of hoses using the tube of the present invention, hoses containing the tube of the present invention as an inner layer, or hoses containing an inner layer, a reinforcing layer and an outer layer, are provided, characterized in that the inner layer is the tube of the present invention.

[0143] Example

[0144] [raw materials]

[0145] The raw materials used in the following embodiments and comparative examples are as follows.

[0146] Butyl rubber: ExxonMobil Chemicals' brominated isobutylene-p-methylstyrene copolymer rubber "EXXPRO" (registered trademark) 3745

[0147] Acid-modified polyolefins: Maleic acid-modified α-olefin copolymer "TAFMER" (registered trademark) MH7010 manufactured by Mitsui Chemicals Co., Ltd.

[0148] Polyamide 6: Polyamide 6 "UBE Nylon" (registered trademark) manufactured by Ube Industries, Ltd. 1011FB

[0149] Polyamide 6 / 12: Polyamide 6 / 12 copolymer "UBE Nylon" (registered trademark) 7024B manufactured by Ube Industries, Ltd.

[0150] Polyamide 12: Polyamide 12 "UBESTA" (registered trademark) 3012U manufactured by Ube Industries, Ltd.

[0151] Anti-aging agent: Solutia's phenylenediamine-based anti-aging agent "SANTOFLEX" (registered trademark) 6PPD (substance name: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine)

[0152] Viscosity stabilizer: Three types of zinc oxide manufactured by Seidouka Kogyo Co., Ltd. (as a masterbatch for mixing zinc oxide into polyamide 6; the table shows the amount of zinc oxide added).

[0153] Processing aid-1: Calcium stearate SC-PG manufactured by Sakai Chemical Industry Co., Ltd.

[0154] Processing aid-2: Industrial stearic acid manufactured by Chiba Fatty Acid Co., Ltd.

[0155] [Preparation of thermoplastic resin compositions]

[0156] The raw materials were fed into a twin-screw extruder (manufactured by Nippon Steel Corporation) at the proportions shown in Tables 1 and 2, and mixed at 235°C for 3 minutes. The mixture was continuously extruded from the extruder into strands, cooled with water, and cut with a cutter to obtain granular thermoplastic resin composition for inner layers.

[0157] [Tube Making]

[0158] Using a 40mmφ extruder, under the conditions shown in Tables 1 and 2, a thermoplastic resin composition is extruded into a core material in a tubular shape, and the core material is extracted to produce a tube.

[0159] In the table, "draw extrusion" refers to products manufactured by draw extrusion molding, such as... Figure 10 As shown, this illustrates a method in which a thermoplastic resin composition is brought into contact with a core material outside a mold.

[0160] In the table, "full" refers to products made through full extrusion molding, such as... Figure 11As shown, this illustrates a manufacturing method that involves bringing a thermoplastic resin composition into contact with a core material inside a mold.

[0161] In addition, the thermoplastic resin composition of Comparative Example 2 was not suitable for tubes, so no tubes were made.

[0162] For the fabricated tubes, the island phase roundness and aspect ratio were evaluated, and a curling test was conducted. The flexibility of the thermoplastic resin composition was also evaluated. The evaluation results are shown in Tables 1 and 2.

[0163] In addition, the measurement methods for each evaluation item are as follows.

[0164] [Roundness and aspect ratio of island phases]

[0165] Using a scanning probe microscope (SPM), also known as an atomic force microscope (AFM), the measurement mode was set to tapping mode. A cross-section obtained by cutting the tube with a plane passing through the central axis of the tube was photographed within a 5 μm longitudinal and 5 μm transverse range. Using the image processing software ImageJ, the obtained cross-sectional image was binarized using the peaks and the midpoints of the histogram as boundaries. For the binarized image, a value of 10000 nm was considered. 2 For all island phases with the above areas, calculate the circularity (Circ. term) and obtain the average value. Additionally, for an area of ​​10000 nm... 2 For all the island phases above, approximate them with an ellipse, find the major axis (Major term) and minor axis (Minor term), calculate the aspect ratio (major axis / minor axis), and then calculate the average value.

[0166] [Curling Test]

[0167] Cut out from the pipe Figure 9 The specimen shown in (a) was placed in an oven with the thinner part facing upwards and held vertically. It was heated at 150°C for 30 minutes, and the curling after heating was observed. The specimen bent towards the inner surface due to heating, which indicates that the shrinkage force on the inner surface is greater than that on the outer surface. This can be attributed to the residual stress on the inner surface. Figure 9 (b) shows an example of a test piece before heating. Figure 9 (c) indicates the state of the specimen after heating. The angle between the straight line connecting the tip and root of the thin part of the heated specimen and the straight line (vertical line) along the length of the thick part is defined as the curl angle. The larger the curl angle, the greater the residual stress on the inner surface. A curl angle less than 10° is recorded as 0, and a curl angle greater than 10° is recorded as ×.

[0168] [Softness]

[0169] Using a 40mmφ single-shaft extruder (Plagiken Co., Ltd.) with a 200mm wide T-die, the temperature of the barrel and die is set to the melting point of the polymer component with the highest melting point in the thermoplastic resin composition +10°C. The thermoplastic resin composition is molded into a sheet with an average thickness of 1.0mm under the conditions of a cooling roller temperature of 50°C and a traction speed of 3m / min.

[0170] A sheet with an average thickness of 1.0 mm was punched into a dumbbell shape according to JIS No. 6. Tensile tests were conducted according to JIS K7161 at a temperature of 25℃, relative humidity of 50%, and a speed of 500 mm / min. The stress at 10% stretch was determined from the obtained stress-strain curve and taken as the 10% modulus. A 10% modulus below 20 MPa was evaluated as good flexibility (〇), and a 10% modulus above 20 MPa was evaluated as poor flexibility (×).

[0171]

[0172] Industry availability

[0173] The tube of the present invention can be well used as the inner layer of a hose for refrigerant delivery.

[0174] Explanation of symbols in attached drawings

[0175] 1 tube

[0176] 2 central axes

[0177] Inner surface of 3 tubes

[0178] 4 outer surfaces

[0179] Centerline of 5 tubes in the thickness direction

[0180] 6. The range from the inner surface of the tube along the thickness direction up to 5 μm.

[0181] The central 5μm range in the thickness direction of tube 7

[0182] 8. A line extending 2.5 μm outwards from the center line 5 in the tube thickness direction.

[0183] 9. A line extending 2.5 μm inward from the center line 5 along the tube thickness direction.

[0184] 10 Dies for pull-out extrusion molding

[0185] 11. Filling the extrusion molding die

[0186] 12 core materials

[0187] 13 Thermoplastic Resin Compositions

[0188] 14 mold heads

Claims

1. A pipe comprising a thermoplastic resin composition having an island structure, said island structure being formed of an island phase containing rubber and a sea phase containing thermoplastic resin. The thermoplastic resin composition contains 100 parts by weight of rubber and 30-120 parts by weight of thermoplastic resin. The thickness of the tube is 0.1mm or more. In a cross-section obtained by cutting the tube with a plane containing the tube's central axis, the roundness of the island phase in the cross-section extending from the inner surface of the tube along the thickness direction to 5 μm is called the inner surface roundness, and the roundness of the island phase in the cross-section extending from the center of the tube's thickness direction to 5 μm is called the central roundness. When the inner surface roundness and the central roundness satisfy equations (1) and (2): 0.35≤inner surface roundness≤1.0 (1) 60≤inner surface roundness / central roundness×100≤120 (2).

2. The pipe as described in claim 1, in the cross-section obtained by cutting the pipe with a plane containing the central axis of the pipe, the aspect ratio of the island phase in the cross-section extending from the inner surface of the pipe along the thickness direction to 5 μm is called the inner surface aspect ratio, and the aspect ratio of the island phase in the cross-section extending from the central 5 μm of the thickness direction of the pipe is called the central aspect ratio, the inner surface aspect ratio and the central aspect ratio satisfy equations (3) and (4): 1≤inner surface aspect ratio≤3 (3) 90≤Inner surface aspect ratio / Central aspect ratio×100≤150 (4).

3. The tube as described in claim 1 or 2, wherein the rubber contains an elastomer having a polyisobutylene backbone.

4. The tube as claimed in claim 3, wherein the elastomer having a polyisobutylene backbone is selected from at least one of butyl rubber, halogenated butyl rubber, isobutylene-p-methylstyrene copolymer rubber, halogenated isobutylene-p-methylstyrene copolymer rubber, and styrene-isobutylene-styrene block copolymer.

5. The tube according to any one of claims 1 to 4, wherein the thermoplastic resin contains polyamide.

6. The tube of claim 5, wherein the polyamide is at least one selected from polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 6 / 66 copolymer, polyamide 6 / 12 copolymer, polyamide 46, polyamide 6T, polyamide 9T and polyamide MXD6.

7. The tube according to any one of claims 1 to 6, wherein the rubber is cross-linked.

8. A method for manufacturing a tube according to any one of claims 1 to 7, the method comprising the step of extruding a thermoplastic resin composition into a tubular shape by pull-out extrusion molding.

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