Flexible tube

Abstract

Provided is a flexible tube having excellent resistance to acidic and alkaline fluids such as an aqueous sodium hypochlorite solution or an aqueous sodium hydroxide solution, the flexible tube being used in factories for manufacturing foods such as beverages, cosmetics, fragrances, pharmaceuticals or other products, and the like. The flexible pipe according to the present invention comprises at least: a first resin layer which is composed of a fluororesin, has a thickness of 0.05-0.5 mm, and accounts for 1-16% of the total thickness of the flexible pipe; and a second resin layer comprising a thermoplastic resin different from the first resin layer, the flexural modulus of the fluororesin measured on the basis of ASTM D790 being 500-1200 MPa, and the ratio (A) / (B) of the peak area (A) corresponding to a C-H bond at a wave number of 1400-1500 cm <-1 > and the peak area (B) corresponding to a C-F bond at a wave number of 1000-1100 cm <-1 > obtained on the basis of FTIR measurement being 0.2-4.0.

Description

Technical Field

[0001] The present invention relates to a flexible tube that is excellent in resistance to acidic and alkaline fluids such as aqueous sodium hypochlorite solution or aqueous sodium hydroxide solution and is used in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products. Background Art

[0002] Fluororesins have excellent properties such as chemical resistance, heat resistance, weather resistance, and gas barrier properties, and have few eluates. Flexible tubes using fluororesins as materials in direct contact with fluids are used in various industrial fields. However, since fluororesins are hard and expensive, laminated hoses have been proposed in which a thermoplastic resin is laminated on the outer peripheral layer to reduce the amount of fluororesin used.

[0003] For example, in Patent Document 1, a fuel hose is disclosed that is laminated with an ethylene / tetrafluoroethylene copolymer (hereinafter referred to as ETFE) excellent in fuel barrier properties, chemical resistance, and heat resistance as an inner layer material, and a polyamide excellent in mechanical properties and durability as an outer layer material. In addition, in Patent Document 2, a fuel hose is disclosed that has high resistance to hydrocarbon fuels and fuel vapors by covalently bonding an inner layer made of PVDF and an outer layer made of a thermoplastic resin.

[0004] However, although these fuel hoses are excellent in fuel barrier properties and chemical resistance, they lack flexibility. Especially in applications such as manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products where piping freedom is required, when a flexible tube is installed, if the radius of the circle (bending radius) described by the flexible tube is small, there is a problem that the flexible tube kinks and blocks the flow path.

[0005] In view of this, a laminated hose has been proposed that uses a softer polyurethane as the thermoplastic resin laminated on the outer peripheral surface.

[0006] In Patent Document 3, a food hose with excellent flexibility is disclosed that is laminated with a polyamide layer and a polyurethane layer on an inner layer made of ETFE.

[0007] However, in manufacturing plants for foods, cosmetics, fragrances, pharmaceuticals, etc., as a countermeasure against foreign substances mixed into products during the manufacturing process, including a process of cleaning the inner surface of the tube with acidic and alkaline fluids such as aqueous sodium hypochlorite solution or aqueous sodium hydroxide solution whenever the fluid flowing in the tube changes corresponding to multiple products. The acid and base components of the liquid medicine used in the cleaning corrode the polyamide layer through the liquid contact surface, resulting in delamination and a problem of blocking the flow path.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent No. 4247103 Gazette

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-535986 Gazette

[0012] Patent Document 3: Japanese Patent No. 4696293 Gazette Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] An object of the present invention is to provide a flexible flexible tube having excellent resistance to acidic and alkaline fluids such as aqueous sodium hypochlorite solution or aqueous sodium hydroxide solution, which is used in manufacturing factories of foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products.

[0015] Means for Solving the Problems

[0016] The object of the present invention is achieved by the following (1) to (4).

[0017] (1) In a flexible tube including at least a first resin layer having a thickness of 0.05 to 0.5 mm made of a fluororesin and the thickness of the layer made of the fluororesin accounting for 1 to 16% of the total thickness of the flexible tube, and a second resin layer made of a thermoplastic resin different from the first resin layer, the flexural modulus of elasticity of the fluororesin measured based on ASTM D790 is 500 to 1200 MPa, and the ratio (A) / (B) of the peak area (A) of the C-H bond corresponding to the wave number 1400 to 1500 cm -1 to the peak area (B) of the C-F bond corresponding to the wave number 1000 to 1100 cm -1 is 0.2 to 4.0.

[0018] (2) The flexible tube according to (1) above, wherein the thermoplastic resin of the second resin layer is a polyamide resin, and the thickness of the second resin layer is 0.05 to 0.4 mm.

[0019] (3) The flexible tube according to (2) above, wherein a third resin layer made of a thermoplastic resin is laminated outside the second resin layer, the ratio (E) = (D) / (C) of the inner diameter (C) of the flexible tube to the total thickness (D) of the flexible tube is 0.4 or less, the ratio (H) = (G) / (F) of the thickness (F) of the first resin layer to the thickness (G) of the third resin layer is 4.0 or more, and the product (E)×(H) of the ratios (E) and (H) satisfies 0.8 to 1.7.

[0020] (4) The flexible tube according to (3) above, wherein at least one reinforcing material made of fiber, monofilament, steel wire, or spring is included between adjacent layers.

[0021] Advantages of the Invention

[0022] According to the present invention, a flexible tube excellent in resistance to acidic or alkaline fluids such as aqueous sodium hypochlorite solution or aqueous sodium hydroxide solution and soft can be obtained for use in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products, etc. Detailed Embodiments

[0023] Hereinafter, preferred embodiments of the flexible tube of the present invention will be described in detail.

[0024] The flexible tube according to the embodiment of the present invention is, for example, a flexible tube excellent in resistance to acidic or alkaline fluids such as aqueous sodium hypochlorite solution or aqueous sodium hydroxide solution for use in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products, etc.

[0025] <First Resin Layer>

[0026] The first resin layer is formed of a fluororesin. In order to impart conductivity, carbon-based or metal-based conductive fillers may be added, but it is not limited thereto.

[0027] The thickness of the first resin layer is preferably 0.05 to 0.5 mm, more preferably 0.1 to 0.4 mm. If the thickness is less than 0.05 mm, the acidic or alkaline fluid permeates and corrodes the second resin layer, so it cannot be used as a flexible tube for transporting acidic or alkaline fluids. On the other hand, if the thickness is greater than 0.5 mm, although the permeation of acidic or alkaline fluids can be suppressed, kinking easily occurs during bending, and a flexible tube that can be piped with a small bending radius cannot be obtained. Therefore, by setting the thickness within the above range, a flexible tube with softness and improved resistance to permeation of acidic or alkaline fluids can be obtained for the first resin layer. Even when transporting acidic or alkaline fluids, it will not corrode, and even when set with a small bending radius, it will not kink, which is a novel flexible tube.

[0028] In addition, if the thickness of the first resin layer exceeds 16% of the total thickness of the flexible tube, when the flexible tube is bent, the other layers located outside the first resin layer cannot maintain the circular cross-sectional shape of the first resin layer, and the cross-sectional shape becomes flat, resulting in kinking. If the thickness of the first resin layer is less than 1% of the total thickness of the flexible tube, on the inner side of the bending direction when the flexible tube is bent, the first resin layer follows the movement in the compression direction of the other layers located outside, resulting in wrinkles on the first resin layer, and starting from the wrinkles, the flexible tube kinks, so it is not suitable.

[0029] Preferably, the material of the first resin layer does not contaminate the fluid and is not affected by corrosion from the fluid, etc. Specifically, fluororesins, such as ethylene / tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene / chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride terpolymer (THV), etc., are exemplified, but not limited thereto. ETFE with high mechanical strength and melt formability is preferred, and adhesive ETFE provided with acid-modified adhesive functional groups is more preferred.

[0030] The flexural modulus of elasticity of the fluororesin measured based on ASTM D790 is 500 to 1200 MPa. The flexural modulus of elasticity depends on the number-average molecular weight of the fluororesin and can be used as a reference for the number-average molecular weight. That is, the higher the flexural modulus of elasticity, the higher the number-average molecular weight, and the lower the flexural modulus of elasticity, the lower the number-average molecular weight. Therefore, if the flexural modulus of elasticity is less than 500 MPa, the number-average molecular weight is low, the entanglement of molecular chains is less, the free volume between molecular chains becomes larger, and it is easy to permeate acidic and alkaline fluids. If the flexural modulus of elasticity is greater than 1200 MPa, the number-average molecular weight is high, the melt formability is reduced, and a soft flexible tube cannot be obtained. The flexural modulus of elasticity is preferably 600 to 1100 MPa.

[0031] In addition, the ratio (A) / (B) of the peak area (A) corresponding to the C-H bond at a wavenumber of 1400 to 1500 cm -1 obtained by FTIR measurement of the fluororesin to the peak area (B) corresponding to the C-F bond at a wavenumber of 1000 to 1100 cm -1 is 0.2 to 4.0. This peak area ratio corresponds to the ratio of C-H units to C-F units in the fluororesin, that is, the higher the peak area ratio, the more C-H units, and the lower the peak area ratio, the more C-F units. Therefore, when the peak area ratio is less than 0.2, the C-F units are more, and as a fluororesin, the mechanical strength is high, the melt formability is reduced, and a soft flexible tube cannot be obtained. On the other hand, when the peak area ratio is greater than 4.0, the C-H units become more. Since the atomic diameter of the H atom is smaller than that of the F atom, the C-C bond bonded to the H atom is easy to rotate, the free volume becomes larger, and it is easy to permeate acidic and alkaline fluids.

[0032] <Second resin layer>

[0033] The second resin layer is formed of a thermoplastic resin different from the first resin layer, and additives may be added to express functions such as softness, thermal stability, light stability, and weather resistance. As additives, there are plasticizers or stabilizers that impart softness. For example, as plasticizers, alkoxybenzoate plasticizers with a molecular weight of 200 to 400 can be exemplified, but not limited thereto.

[0034] The second resin layer preferably uses a material with flexibility and excellent adhesiveness to fluororesin. As thermoplastic resins, polyamide, polyvinyl chloride, polyamide-based elastomers, polyurethane-based elastomers, polystyrene-based elastomers, olefin-based elastomers, or their mixtures, and modified resins treated by conventionally known methods can be cited, but are not limited thereto. Polyamide 11 or polyamide 12, polyamide-based elastomers, and their mixtures with a flexural modulus of elasticity measured according to ISO 178 of 200 to 1300 MPa are preferred.

[0035] The thickness of the second resin layer is preferably 0.05 to 0.4 mm, more preferably 0.1 to 0.35 mm.

[0036] If the thickness is less than 0.05 mm, the mechanical strength of the flexible tube decreases. On the other hand, if it is thicker than 0.4 mm, a flexible flexible tube cannot be obtained. Therefore, by setting the thickness within the above range, the second resin layer can achieve flexibility.

[0037] <The third resin layer>

[0038] The third resin layer is formed of a thermoplastic resin, and additives may be added to express functions such as flexibility, thermal stability, light stability, and weather resistance. As additives, plasticizers or stabilizers that impart flexibility can be cited, but are not limited thereto.

[0039] The third resin layer preferably uses a material with excellent flexibility. As thermoplastic resins, polyamide, polyvinyl chloride, polyamide-based elastomers, polyurethane-based elastomers, polystyrene-based elastomers, olefin-based elastomers, or their mixtures can be cited, but are not limited thereto. Polyurethane-based elastomers with low mechanical strength and excellent flexibility are preferred, and more preferably, polyurethane elastomers of esters, hexanoic acids, carbonates, and ethers with a Shore A hardness of 60 to 95 and a resilience of 40 to 70% measured according to JIS K7311.

[0040] To impart appropriate flexibility to the flexible tube, the thickness of the third resin layer is preferably 0.1 to 5.0 mm, more preferably 0.5 to 3.5 mm.

[0041] <Reinforcing material>

[0042] As the reinforcing material, for example, multiple or single braids made of polyester, PET, nylon (registered trademark), or aramid fibers can be cited; monofilaments made of olefin resins, polyester resins, etc.; multifilaments braiding fine monofilaments (monofilament: single fiber); flat yarns (or tape yarns) made of ribbon wires; metal wires made of stainless steel, etc., or coils made of hard materials similar to stainless steel.

[0043] <Laminated structure>

[0044] The flexible tube of the present invention is a flexible tube including a laminated structure, in which a first resin layer made of the fluororesin of the present invention and a second resin layer made of a thermoplastic resin are laminated.

[0045] In the flexible tube of the present invention, the first resin layer has chemical resistance and few eluates, and the second resin layer has flexibility and adhesiveness to the first resin layer. Thus, a flexible tube with excellent chemical resistance, extremely few eluates, and less likely to break compared to a single-layer tube made of fluororesin can be formed. By further laminating a soft third resin layer, a flexible tube that is soft and does not kink even when set with a small bending radius and is not available in the past can be obtained.

[0046] As long as the basic laminated structure is included, a flexible tube with a layer made of other thermoplastic resins further laminated thereon can also be manufactured, and a reinforcing material can be provided between any adjacent layers. The total number of layers of the flexible tube is not particularly limited, at least 3 layers or more, usually 3 - 8 layers, preferably 3 - 5 layers.

[0047] The overall wall thickness of the flexible tube is determined in consideration of the inner diameter of the flexible tube and various characteristics such as flexibility and pressure resistance according to the use. From the viewpoints of pressure resistance, kink resistance, and handling, it is preferred that as the inner diameter of the flexible tube increases, the wall thickness also increases. Specifically, the ratio (E) of the inner diameter (C) of the flexible tube to the total thickness (D) of the flexible tube = (D) / (C) is preferably 0.4 or less. If (E) is greater than 0.4, the wall thickness of the flexible tube is thick relative to the inner diameter, and the flexibility of the flexible tube is impaired, making it unsuitable for use in various manufacturing factories and the like where piping freedom is required. In addition, the ratio (H) of the thickness (G) of the third resin layer to the thickness (F) of the first resin layer = (G) / (F) is preferably 4.0 or more. When (H) is less than 4.0, the thickness of the third resin layer is not sufficient to impart flexibility to the flexible tube, and a soft flexible tube cannot be obtained.

[0048] Furthermore, based on (E) and (H), the thicknesses of the first resin layer and the third resin layer can be defined relative to the total thickness of the flexible tube that varies with the inner diameter. It is preferred that (E)×(H) satisfies the range of 0.8 - 1.7. When (E)×(H) is less than 0.8, since the total thickness of the flexible tube is thin relative to the inner diameter of the flexible tube, the cross-sectional circular shape cannot be maintained when bending the flexible tube, and the cross-sectional shape is flat, resulting in kinking. When it is greater than 1.7, since the total thickness of the flexible tube is thick relative to the inner diameter of the flexible tube, the inner side in the bending direction when bending the flexible tube is compressed, resulting in wrinkles, and starting from the wrinkles, the flexible tube kinks.

[0049] The bending radius (R) increases as the inner diameter of the flexible tube increases. The flexible tube of the present invention is preferably such that when the value (R) / (C) obtained by dividing the bending radius (R) by the inner diameter (C) is less than 15, and (R) / (C) is less than 15, it does not kink even when set with a small bending radius. It is preferably less than 13, and more preferably less than 11.

[0050] <Laminating method>

[0051] As a method for forming the flexible tube of the present invention, there can be mentioned (1) a co-extrusion molding method in which the adhesive fluororesin constituting the first resin layer and the thermoplastic resin constituting the second resin layer are co-extruded in a molten state and the two are melt-bonded to form a double-layer structure flexible tube in one step; (2) a method in which the outer surface of a tube obtained by extruding a fluororesin constituting the first resin layer is modified by a discharge treatment such as plasma discharge or corona discharge, and a chemical solution treatment such as sodium etching, various adhesive functional groups are introduced into the surface, and then the thermoplastic resin constituting the second resin layer is extruded and laminated onto the fluororesin tube that has undergone the outer surface treatment, and so on.

[0052] From the viewpoint of productivity, a co-extrusion molding method is preferably employed. In order to improve the adhesion between layers, an adhesive fluororesin can be used for the first resin layer.

[0053] As an acid-modified adhesive fluororesin, and as ETFE into which adhesive functional groups have been introduced, there are "Fluon (registered trademark) LM-ETFE AH series (manufactured by AGC Inc.)" and "Neoflon (registered trademark) EFERP series (manufactured by Daikin Industries, Ltd.)", etc.

[0054] As an example, when an acid-modified adhesive fluororesin is used in the first resin layer, a polyamide having good compatibility with the acid-modified adhesive fluororesin is used in the second resin layer, and a polyurethane elastomer having good compatibility with the polyamide and excellent heat resistance is used in the third resin layer. By co-extruding and laminating the three layers at the same time, a flexible tube with excellent chemical resistance and heat resistance and softness can be obtained.

[0055] The flexible tube of the present invention has excellent chemical resistance and softness. In addition, due to its excellent heat resistance, corrosion resistance, oil resistance, weather resistance, etc., it can be applied to tubes and hoses for food, cosmetics, fragrances, pharmaceuticals, medical use, fuels, coolants, pure water, inks, etc.

[0056] Example 1

[0057] Hereinafter, the present invention will be specifically described with reference to examples, but the technical scope of the present invention is not limited thereto.

[0058] In addition, the peak area ratio, chemical resistance, and flexibility as measurement items are measured by the following methods.

[0059] <Peak area ratio>

[0060] Regarding the peak area ratio, for FTIR measurement, a Fourier transform infrared spectrophotometer "FT / IR-6100 type A (wavenumber interval 0.482117 cm -1 )" manufactured by JASCO Corporation is used, and the granulated resin is used as a sample for measurement. First, the first derivative value obtained by dividing the increase in transmittance by the increase in wavenumber and the second derivative value obtained by dividing the increase in the first derivative value by the increase in wavenumber are calculated respectively. The point of positive and negative change of the first derivative value is taken as the extreme value, and the point of positive and negative change of the second derivative value is taken as the inflection point. Within the extreme value, the point where the transmittance takes the minimum value is set as the peak value, and the two adjacent inflection points on both sides are set as the peak bases [1] and [2]. The difference between the transmittance of the straight line connecting the peak bases [1] and [2] and the transmittance of the peak value in the wavenumber of the peak value is set as the peak height. Then, the central value of the transmittance of the straight line connecting the peak bases [1] and [2] and the transmittance of the peak value in the wavenumber of the peak value is taken as the half value, and the width of the waveform in the half value (half value width) is obtained.

[0061] Based on the peak corresponding to the C-H bond appearing at the wavenumber of 1400 - 1500 cm -1 , the peak height and the half value width are obtained, and their product is taken as the peak area (A) corresponding to the C-H bond. Based on the peak corresponding to the C-F bond appearing at the wavenumber of 1000 - 1100 cm -1 , the peak height and the half value width are obtained, and their product is taken as the peak area (B) corresponding to the C-F bond. The ratio (A) / (B) of them is taken as the peak area ratio. Here, Table 1 shows a calculation example of the peak area corresponding to the C-F bond at the wavenumber of 1000 - 1100 cm -1 of the adhesive ETFE5.

[0062]

Table 1

[0063] FTIR measurement data and peak area (1000 - 1100 cm-1) of the adhesive ETFE5

[0064]

[0065] <Chemical resistance>

[0066] Regarding chemical resistance, 35% hydrochloric acid aqueous solution was sealed in the flexible tubes of Examples 1 to 31 and Comparative Examples 1 to 5 (12 flexible tubes of 30 cm each obtained from the same production batch for each example and comparative example), and the time until delamination occurred was measured when placed in an environment of 23°C. After cutting the positions 10 cm and 20 cm from the end of the flexible tube respectively, an external force was applied until the inner surfaces contacted each other and became flat, and when it was restored in the circumferential direction by the restoring force of the flexible tube itself, it was confirmed whether delamination occurred between layers. The confirmation of delamination was carried out one by one every week. Those with a delamination time of more than 2 months were designated as ◎, those with more than 1.5 months and less than 2 months were designated as 〇, those with more than 1 month and less than 1.5 months were designated as △, and those with less than 1 month were designated as ×.

[0067] <Flexibility>

[0068] Regarding flexibility, it was evaluated by bending the flexible tubes of Examples 1 to 31 and Comparative Examples 1 to 5. In an environment of 23°C, the flexible tube was bent into a circle with a ratio of diameters in two orthogonal directions of 1:1, and the radius (bending radius) R of the circle described by the flexible tube when the outer diameter of the flexible tube was flattened to 90% of the normal value was measured. Generally, since the bending radius R increases as the inner diameter of the flexible tube increases, in its evaluation, the ratio of the inner diameter (C) of the flexible tube to the bending radius (R) was used.

[0069] Those with (R) / (C) less than 11 were designated as ◎, those with 11 or more and less than 13 were designated as ○, those with 13 or more and less than 15 were designated as △, and those with 15 or more were designated as ×.

[0070] <Comprehensive evaluation>

[0071] First, in terms of chemical resistance, among the evaluations of ◎ (more than 2 months), those with more than 2 months and less than 2.5 months were designated as “◎-”, and those with 2.5 months or more were designated as “◎+”. In terms of flexibility, among the evaluations of ◎ (less than 11), those with 9 or more and less than 11 were designated as “◎-”, and those with less than 9 were designated as “◎+”.

[0072] On this basis, based on the evaluations of ◎+ to × for chemical resistance and flexibility, a comprehensive evaluation was carried out in five grades. Among them, as long as there is one ×, it was set as 1 point, as long as there is one △, it was set as 2 points, as long as there is one ○, it was set as 3 points, as long as there is one ◎-, it was set as 4 points, and if all are ◎+, it was set as 5 points.

[0073] When manufacturing the flexible tubes shown in the examples, adhesive ETFE 1 to 9 with the following characteristics was prepared. The flexural modulus and peak area ratio were adjusted by changing the molar ratio of ethylene and tetrafluoroethylene during polymerization, and the adhesiveness was obtained by adding 0.4 mol% of itaconic anhydride equivalent to the total molar amount of ethylene and tetrafluoroethylene added during polymerization.

[0074] The flexural modulus of the adhesive ETFE1 is 1200 MPa, and the peak area ratio is 4.0.

[0075] The flexural modulus of the adhesive ETFE2 is 1200 MPa, and the peak area ratio is 1.0.

[0076] The flexural modulus of the adhesive ETFE3 is 1200 MPa, and the peak area ratio is 0.2.

[0077] The flexural modulus of the adhesive ETFE4 is 770 MPa, and the peak area ratio is 4.0.

[0078] The flexural modulus of the adhesive ETFE5 is 770 MPa, and the peak area ratio is 1.0.

[0079] The flexural modulus of the adhesive ETFE6 is 770 MPa, and the peak area ratio is 0.2.

[0080] The flexural modulus of the adhesive ETFE7 is 500 MPa, and the peak area ratio is 4.0.

[0081] The flexural modulus of the adhesive ETFE8 is 500 MPa, and the peak area ratio is 1.0.

[0082] The flexural modulus of the adhesive ETFE9 is 500 MPa, and the peak area ratio is 0.2.

[0083] In Example 1, as shown in Table 2, a first resin layer made of the adhesive ETFE1, a second resin layer made of polyamide 12 (Polyplastics-Evonik Co., Ltd. ZL1105) with a flexural modulus of 300 MPa to which a hydroxybenzoic acid alkyl ester plasticizer with a molecular weight of 250 to 350 is added as a plasticizer, and a third resin layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) with a Shore A hardness of 83 and a resilience of 45% were co-extrusion molded so that the thickness of the first resin layer was 0.5 mm, the thickness of the second resin layer was 0.2 mm, and the thickness of the third resin layer was 1.3 mm. After being melt-molded into one body, polyester fibers were wound using a knitting machine, and a 1.5-mm-thick outermost layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) was extruded and laminated on the outside to obtain a flexible tube with an inner diameter of 19 mm and an outer diameter of 26 mm.

[0084]

Table 2

[0085]

[0086] Examples 2 to 31 and Comparative Examples 3 to 5 were prepared by appropriately controlling the materials and thicknesses of each layer to obtain the values shown in Table 2, and flexible tubes were obtained in the same manner as in Example 1.

[0087] In Comparative Example 1, as shown in Table 2, adhesive ETFE5 was extrusion molded to a thickness of 0.2 mm to obtain a single-layer tube with an inner diameter of 9 mm and an outer diameter of 9.4 mm.

[0088] In Comparative Example 2, as shown in Table 2, a first resin layer made of a polyurethane elastomer (1180A manufactured by BASF), a second resin layer made of polyamide 12 (ZL1105 manufactured by Polyplastics-Evonik Co., Ltd.) with a flexural modulus of 300 MPa and a hydroxybenzoic acid alkyl ester plasticizer with a molecular weight of 250 to 350 added as a plasticizer, and a third resin layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) with a Shore A hardness of 83 and a resilience of 45% were co-extrusion molded so that the thickness of the first resin layer was 0.2 mm, the thickness of the second resin layer was 0.2 mm, and the thickness of the third resin layer was 1.6 mm. After melt-molding them into one body, polyester fibers were wound using a knitting machine, and an outermost layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) was extrusion molded and laminated on the outside to make the total thickness of the flexible tube 3.5 mm, thereby obtaining a flexible tube with an inner diameter of 19 mm and an outer diameter of 26 mm.

[0089] In Comparative Example 5, as shown in Table 2, a first resin layer made of adhesive ETFE5, a second resin layer made of polyamide 12 (ZL1105 manufactured by Polyplastics-Evonik Co., Ltd.) with a flexural modulus of 300 MPa and a hydroxybenzoic acid alkyl ester plasticizer with a molecular weight of 250 to 350 added as a plasticizer, and a third resin layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) with a Shore A hardness of 83 and a resilience of 45% were co-extrusion molded so that the thickness of the first resin layer was 0.2 mm, the thickness of the second resin layer was 0.1 mm, and the thickness of the third resin layer was 0.3 mm. After melt-molding them into one body, polyester fibers were wound using a knitting machine, and an outermost layer made of a carbonate-based polyurethane elastomer (P-880 manufactured by Dainichi Seika Kogyo Co., Ltd.) was extrusion molded and laminated on the outside to make the total thickness of the flexible tube 2.0 mm, thereby obtaining a flexible tube with an inner diameter of 19 mm and an outer diameter of 23 mm.

[0090] Measurements were carried out based on the above test methods, and the results obtained were as follows.

[0091] Examples 1 to 31, since the thickness of the first resin layer is in the range of 0.05 to 0.5 mm and the thickness of the first resin layer is 1 to 16% of the total thickness of the flexible tube, the comprehensive evaluation is above 2 points (<chemical resistance> is above △ (above 1 month and less than 1.5 months), and <flexibility> is above △ (above 13 and less than 15)), having sufficient chemical resistance and flexibility for use in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products.

[0092] Among them, the comprehensive evaluations of Examples 1 to 2, Examples 4 to 28, and Examples 30 to 31 are above 3 points (<chemical resistance> is above ○ (above 1.5 months and less than 2 months), and <flexibility> is above ○ (above 11 and less than 13)), with excellent chemical resistance and flexibility. In particular, the comprehensive evaluations of Examples 10 to 22 are above 4 (<chemical resistance> is ◎ (above 2 months), and <flexibility> is ◎ (less than 11)), with even more excellent chemical resistance and flexibility.

[0093] In addition, for Examples 11 to 21, the thickness of the second resin layer is in the range of 0.05 to 0.4 mm, and the comprehensive evaluation is 5 points (<chemical resistance> and <flexibility> are both ◎+), with the best chemical resistance and flexibility among Examples 1 to 31.

[0094] For Comparative Examples 1 to 5, the comprehensive evaluation is 1 point (either <chemical resistance> or <flexibility> is ×), and the evaluation result is that either <chemical resistance> or <flexibility> is poor.

[0095] For Comparative Example 1, which has a single-layer structure and no peeling occurs, "chemical resistance" cannot be evaluated. In addition, since there is no outer layer that maintains a circular cross-sectional shape when the flexible tube is bent, <flexibility> is × (above 15), and the evaluation result is poor. Although there is no peeling of acidic or alkaline fluids, the flexibility is significantly low, and it does not have sufficient flexibility for use in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products.

[0096] For Comparative Example 2, its <flexibility> is ◎ (less than 11), with excellent flexibility, but the resin of the first resin layer itself is eroded by acidic and alkaline fluids, and <chemical resistance> is × (less than 1 month), with significantly reduced chemical resistance, and it does not have sufficient chemical resistance for use in manufacturing plants for foods such as beverages, cosmetics, fragrances, pharmaceuticals, or other products.

[0097] Comparative Example 3 had a relatively thin first resin layer with a thickness of 0.03 mm. Although <Flexibility> was ◎ (less than 11) and the flexibility was excellent, there was more permeation of acidic and alkaline fluids. Therefore, <Chemical Resistance> was × (less than 1 month), and the evaluation result was poor, lacking sufficient chemical resistance for use in manufacturing plants for beverages and other foods, cosmetics, fragrances, pharmaceuticals, or other products.

[0098] Comparative Example 4 had a relatively thick first resin layer with a thickness of 0.8 mm, which inhibited the permeation of acidic and alkaline fluids. Therefore, "Chemical Resistance" was ◎ (more than 2 months), and the chemical resistance was excellent. However, "Flexibility" was × (15 or more), and the evaluation result was poor, with significantly low flexibility and lacking sufficient flexibility for use in manufacturing plants for beverages and other foods, cosmetics, fragrances, pharmaceuticals, or other products.

[0099] Comparative Example 5 had a first resin layer with a thickness in the range of 0.05 to 0.5 mm. <Chemical Resistance> was ◎ (more than 2 months), and the chemical resistance was good. However, the thickness of the first resin layer accounted for 20% of the total thickness of the flexible tube, which was relatively thick. Therefore, the other layers outside the first resin layer could not maintain the circular cross-sectional shape of the first resin layer and became flat. Therefore, <Flexibility> was × (15 or more), and the evaluation result was poor, with significantly low flexibility and lacking sufficient flexibility for use in manufacturing plants for beverages and other foods, cosmetics, fragrances, pharmaceuticals, or other products.

[0100] Based on this result, in a flexible tube including at least a first resin layer made of a fluororesin with a thickness of 0.05 to 0.5 mm and accounting for 1 to 16% of the total thickness of the flexible tube, and a second resin layer made of a thermoplastic resin different from the first resin layer, the flexural modulus of elasticity of the fluororesin measured based on ASTM D790 was 500 to 1200 MPa. Moreover, when the ratio (A) / (B) of the peak area (A) corresponding to the C-H bond to the peak area (B) corresponding to the C-F bond obtained by FTIR measurement was 0.2 to 4.0, the chemical resistance and flexibility were excellent, having sufficient chemical resistance and flexibility for use in manufacturing plants for beverages and other foods, cosmetics, fragrances, pharmaceuticals, or other products.

Claims

1. A flexible tube, comprising at least a first resin layer made of a fluororesin with a thickness of 0.05 to 0.5 mm and accounting for 1 to 16% of the total thickness of the flexible tube, and a second resin layer made of a thermoplastic resin different from the first resin layer, The flexural modulus of elasticity of the fluororesin measured based on ASTM D 790 is 500 to 1200 MPa, and the ratio (A) / (B) of the peak area (A) corresponding to the C-H bond at a wavenumber of 1400 to 1500 cm -1 to the peak area (B) corresponding to the C-F bond at a wavenumber of 1000 to 1100 cm -1 obtained by FTIR measurement is 0.2 to 4.

0.

2. The flexible tube according to claim 1, wherein, the thermoplastic resin of the second resin layer is a polyamide resin, and the thickness of the second resin layer is 0.05 to 0.4 mm.

3. The flexible tube according to claim 2, wherein, a third resin layer made of a thermoplastic resin is laminated on the outer side of the second resin layer, the ratio (E) of the inner diameter (C) of the flexible tube to the total thickness (D) of the flexible tube = (D) / (C) is 0.4 or less, the ratio (H) of the thickness (G) of the third resin layer to the thickness (F) of the first resin layer = (G) / (F) is 4.0 or more, and the product (E)×(H) of the ratios (E) and (H) satisfies 0.8 to 1.

7.

4. The flexible tube according to claim 3, wherein, at least one reinforcing material made of fibers, monofilaments, steel wires, or springs is included between adjacent layers.

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