Flexible tube

Abstract

Provided is a flexible tube which is formed by molding a thermoplastic resin composition into a tube shape, has physical properties suitable for a roller pump and the like, and has high durability. In terms of the resin composition, in a stress-strain curve, the strain reaches 300%, and the resin composition does not break; a value obtained by performing primary differentiation on an approximation formula of a stress-strain curve in a region up to a fracture point is positive; and the evaporation residue of a leaching solution after immersion of the resin composition at 25 DEG C for one hour in n-heptane as a solvent is 150 [mu] g / ml or less. The resin composition is characterized in that, in a stress-strain curve, the tensile stress at a strain of 100% is 4.5-8.0 MPa, and the tensile stress at a strain of 300% is included in the range of 11.0-19.0 MPa. The resin composition contains, as a plasticizer, 48-93 parts by weight of an adipic acid-based polyester having a weight-average molecular weight of 3500-5500 per 100 parts by weight of a thermoplastic resin, particularly preferably per 100 parts by weight of a halogen-containing thermoplastic resin.

Description

Technical Field

[0001] The present invention relates to a flexible tube produced by extruding and molding a thermoplastic resin composition. Background Art

[0002] Conventionally, there is known a roller pump which conveys liquid in the flexible tube by flattening a flexible tube arranged in an arc shape along the inner wall surface of a housing formed into a substantially cylindrical surface between the inner wall surface and the roller while rotating the roller along the inner wall surface. These devices are used for feeding, quantitative conveying, flow rate regulation, etc. of fluids in artificial heart-lung devices and hemodialysis devices in the medical field, sauce / spice adding devices in the food field, and raw material adding devices to a reaction kiln in the raw material drug manufacturing process in the pharmaceutical field.

[0003] The flexible tube used in such a roller pump is required to have flexibility and mechanical strength, and also to be durable against repeated squeezing actions by the peristaltic part of the roller pump. Conventionally, the flexible tube used in such a roller pump has been made of a rubber tube represented by silicone or a synthetic resin tube represented by soft vinyl chloride. The rubber or synthetic resin flexible tube is manufactured by extrusion molding, which is easy to mold, and has a circular cross-sectional shape in order to reduce resistance to the fluid flowing inside.

[0004] However, when a circular flexible tube is used in a roller pump, there is a problem that a gap remains near the fold when the tube is flattened in the radial direction, which easily causes leakage and makes it difficult to create a vacuum state in the flexible tube. In order to eliminate such a gap, a considerable pressure is required, and when the circular flexible tube is repeatedly flattened or restored by such pressure, if the elasticity of the flexible tube is insufficient, the elastic force of the flexible tube is weakened and the flexible tube may not be restored to its original circular cross-section.

[0005] As such a flexible tube, a multilayer flexible tube disclosed in Patent Document 1 includes a first layer and a second layer, wherein the first layer comprises a polyolefin material having a bending elastic modulus of 150 MPa or less, and the second layer comprises a blend of a propylene polymer and a styrene block copolymer. According to this multilayer flexible tube, a combination of desired characteristics such as mechanical damping, hardness, a single glass transition temperature, transparency, or a minimum bending radius can be imparted, and no additives eluted into a process stream are contained, and in some cases, no harmful byproducts are generated during incineration.

[0006] In addition, the multilayer flexible tube disclosed in Patent Document 2 is a multilayer flexible tube having an inner layer and an outer layer, wherein the inner layer comprises a melt-processable fluoropolymer, and the outer layer comprises a melt-processable polymer having a Shore hardness lower than that of the inner layer. The fluoropolymer comprises a copolymer of polyvinylidene fluoride (PVDF) and hexafluoropropylene (HFP), and the hexafluoropropylene is present at a molar concentration of more than 30% based on a total molar concentration of 100% of the copolymer. According to this multilayer flexible tube, it is easy to clean and has resistance to pollutants.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 5475794

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-173172 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, in the case of the multilayer flexible tube of the above-mentioned patent document 1, when the polyolefin material used in the multilayer flexible tube circulates oily fluid, substances other than plasticizers may be eluted from the inner surface of the flexible tube, which is not ideal in the medical, food, pharmaceutical fields, etc. In addition, there are the following problems: the physical properties change due to the elution of the substance, the risk of breakage increases, and the life is shortened. In particular, when used for a roller pump that is repeatedly flattened, there is a problem of reduced flow rate due to breakage, deformation, and elongation of the multilayer flexible tube. Moreover, in order to meet the mechanical characteristics, it has a multilayer structure, so the life may be shortened due to peeling between layers. In the case of the multilayer flexible tube of the above-mentioned patent document 2, it also has a multilayer structure. When used for a roller pump, the life may be shortened due to peeling between layers.

[0013] On the other hand, polyvinyl chloride, which is easy to process, has been used in flexible pipes. However, polyvinyl chloride also has the problem of elution of substances depending on the type of fluid. When using low molecular weight plasticizers such as DEHP (di(2-ethylhexyl) phthalate) which is suspected to have an impact on health, when transporting fluids used in the medical, food, and pharmaceutical fields, plasticizers such as DEHP may be eluted into the fluid and may be harmful to health.

[0014] The present invention has been made in view of the above-mentioned problems in the background art, and an object of the present invention is to provide a flexible tube having physical properties suitable for a roller pump and having high durability.

[0015] Solutions for solving problems

[0016] The above-mentioned objects are achieved by the present invention according to the following (1) to (5).

[0017] (1) A flexible tube formed by molding a thermoplastic resin composition into a tube, wherein the resin composition does not break when the strain reaches 300% in a stress-strain curve; the value obtained by first differentiating an approximate equation of the stress-strain curve in a region up to the breaking point is positive (+); and the evaporation residue of an leaching liquid after immersing the resin composition in n-heptane as a solvent at 25°C for 1 hour is 150 μg / ml or less.

[0018] (2) The flexible tube according to (1) above, wherein the resin composition has the following properties: in a stress-strain curve, the tensile stress at a strain of 100% is 4.5 to 8.0 MPa, and the tensile stress at a strain of 300% is within the range of 11.0 to 19.0 MPa.

[0019] (3) The flexible tube according to (2) above, wherein the resin composition has a tensile stress of 4.9 to 7.0 MPa at a strain of 100% and a tensile stress of 12.0 to 15.5 MPa at a strain of 300% in a stress-strain curve, and an IRHD (International Rubber Hardness Degrees) hardness of 62 to 75 degrees.

[0020] (4) The flexible tube according to (2) above, wherein the flexible tube is used in a peristaltic portion of a roller pump.

[0021] (5) The flexible tube according to (2), (3) or (4) above, comprising at least one of phthalic acid-based polyester, adipic acid-based polyester, trimellitic acid-based polyester and acetylcitric acid-based polyester as a plasticizer.

[0022] (6) The flexible tube according to the above (5), wherein the plasticizer comprises 48 to 93 parts by weight of a polyester plasticizer having a weight average molecular weight of 3,500 to 5,500 based on 100 parts by weight of the halogen-containing thermoplastic resin.

[0023] (7) The flexible tube according to the above (6), wherein the polyester plasticizer is an adipic acid-based polyester.

[0024] Effects of the Invention

[0025] The flexible tube of the present invention uses a thermoplastic resin, has physical properties suitable for roller pumps, etc., and can stably transport a fluid in a fixed amount. In addition, by using a specific plasticizer, the elution into the oily fluid is small, the physical properties of the flexible tube do not change, and the durability is high. Since the elution into the fluid is small, it can be safely used in the medical, food, pharmaceutical fields, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a stress (σ)-strain (ε) curve diagram of a flexible pipe according to an embodiment of the present invention.

[0027] Figure 2 This is a graph showing the strain (ε) and the first differential value (d) of Example 1 of the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the present invention will be described. The flexible tube of this embodiment is a tubular body produced by extrusion-molding a resin composition composed of a thermoplastic resin into a tubular shape using an extruder.

[0029] In particular, the flexible tube of this embodiment is formed of the resin composition having the following physical properties: physical properties suitable for applications accompanied by repeated deformation of a roller pump. The characteristics required for this application are: in the stress-strain curve of the flexible tube obtained by a tensile test according to the test method of JIS K 6723, the strain does not break until 300%; and the value obtained by first differentiating the approximate formula of the stress-strain curve in the area up to the breaking point is positive (+). Here, the breaking point is defined as the strain when the tensile stress becomes the maximum in the stress-strain curve. The approximate formula of the stress-strain curve can be obtained using the polynomial approximation function of the accumulation software, and as the accumulation software, Microsoft Excel and the like can be listed.

[0030] Therefore, when used in a roller pump, the discharge amount changes less with time and the durability is high.

[0031] In the stress-strain curve of the flexible tube, if the value obtained by differentiating the approximate formula in the area up to the breaking point is not a positive (+) value, the yield strength of the flexible tube is small, the discharge volume fluctuates greatly, and the flow rate decreases with time. It is not preferable that the roller pump cannot maintain stable performance.

[0032] Here, the roller pump is also called a tube pump, a peristaltic pump, etc., and is composed of a flexible tube and a peristaltic part having a plurality of protrusions. The roller pump is a pump that transports fluid by pushing the protrusions against the flexible tube as the peristaltic part rotates, squeezing out the fluid in the flexible tube.

[0033] In addition, the flexible tube was subjected to a dissolution test according to the test method of "Ministry of Health, Labor and Welfare Notice No. 370 of 1959, Standards for Foods, Additives, etc., Chapter 3, Apparatus and Containers and Packages D (Revised: Ministry of Health, Labor and Welfare Notice No. 267 of August 2, 2002)", and the evaporation residue of the leaching liquid obtained by eluting at 25°C for 1 hour using n-heptane as the dissolution liquid was 150μg / ml or less. The evaporation residue is mainly obtained by the dissolution of the plasticizer of the flexible tube, and the dissolution of the substance is not ideal in the medical, food, and pharmaceutical fields. In addition, it causes changes in the physical properties of the flexible tube. When used in a roller pump, the flow rate decreases due to deformation such as breakage and elongation of the flexible tube, and the roller pump cannot maintain stable performance, which is not preferred. The evaporation residue of the leaching liquid using n-heptane as the solvent is preferably 150μg / ml or less, and more preferably 120μg / ml or less.

[0034] Moreover, in the stress-strain curve of the flexible tube, if the tensile stress is less than 4.5 MPa at a strain of 100%, the flexible tube is easy to stretch, resulting in a decrease in flow rate due to deformation such as stretching, and a break due to wear of the flexible tube winding in the pump head. If the tensile stress is greater than 8.0 MPa, the flexible tube is difficult to stretch, and cracks appear in the case of repeated flattening or recovery, and breakage occurs in a short time. In addition, if the tensile stress is out of the range of 11.0 to 19.0 MPa at a strain of 300%, the same elongation and cracks occur when the plastic deformation of the flexible tube is aggravated by the operating load such as long-term operation of the roller pump and application of the roller pump with a high rotation speed. In the use of the roller pump that repeatedly causes elastic deformation and plastic deformation, it does not have high durability and cannot maintain stable performance. Therefore, in the stress-strain curve of the flexible pipe, it is ideal that the tensile stress is 4.5 to 8.0 MPa at a strain of 100%, and the tensile stress is within the range of 11.0 to 19.0 MPa at a strain of 300%. At this time, the IRHD hardness of the flexible pipe (measured according to the test method of "ISO48 vulcanized rubber or thermoplastic rubber - hardness determination method -") is in the range of 60 to 81 degrees.

[0035] It is further preferred that, in order to make a flexible tube most suitable for a roller pump, in its stress-strain curve, the tensile stress at a strain of 100% is 4.9 to 7.0 MPa, and the tensile stress at a strain of 300% is within the range of 12.0 to 15.5 MPa. At this time, the IRHD hardness is within the range of 62 to 75 degrees.

[0036] Next, the resin composition of the flexible tube according to the embodiment of the present invention will be described.

[0037] The flexible pipe of the present invention contains a thermoplastic resin. The thermoplastic resin is not particularly limited as long as it is a thermoplastic resin, but a halogen-containing thermoplastic resin is preferably used.

[0038] Examples of the halogen-containing thermoplastic resin include polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, vinyl chloride-vinyl acetate copolymers, vinyl chloride-ethylene copolymers, vinyl chloride-propylene copolymers, vinyl chloride-styrene copolymers, vinyl chloride-isobutylene copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-styrene-maleic anhydride terpolymers, vinyl chloride-styrene-acrylonitrile terpolymers, vinyl chloride-butadiene copolymers, vinyl chloride-isoprene copolymers, vinyl chloride-propylene chloride copolymers, vinyl chloride-vinylidene chloride-vinyl acetate terpolymers, vinyl chloride-maleic acid ester copolymers, vinyl chloride-methacrylate copolymers, vinyl chloride-acrylonitrile copolymers, and vinyl chloride-various vinyl ether copolymers; and mixed materials thereof, but the invention is not limited thereto.

[0039] Moreover, as needed, the halogen-containing thermoplastic resin can also be a blend, block copolymer, graft copolymer, etc. of other halogen-free synthetic resins, such as acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene terpolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl (meth)acrylate copolymer, polyester, etc.

[0040] In particular, polyvinyl chloride (hereinafter referred to as "PVC") is preferably used as the halogen-containing thermoplastic resin. Transparent or translucent PVC is preferably used. As a specific example of PVC, TK-1700E manufactured by Shin-Etsu Chemical Co., Ltd. is suitable. PVC is used as an example for explanation below.

[0041] Furthermore, the resin composition forming the flexible tube of the present invention contains 48 to 93 parts by weight of a plasticizer and 0.1 to 3.0 parts by weight of an acrylic lubricant as main components based on 100 parts by weight of PVC.

[0042] Furthermore, in addition to the above-mentioned components, various additives (heat stabilizer, light stabilizer, ultraviolet absorber, antioxidant, antifogging agent, antistatic agent, etc.) may be blended into the resin composition as required.

[0043] As the plasticizer, polyester plasticizers such as phthalic acid polyester, adipic acid polyester, trimellitic acid polyester, and acetylcitric acid polyester can be cited. Preferably, polyester plasticizers having a weight average molecular weight of 3500 to 5500 can be cited. More preferably, polyester plasticizers having a weight average molecular weight of 4000 to 5000 can be cited. As the polyester plasticizer, adipic acid polyester is particularly preferred.

[0044] When the content of the polyester plasticizer is less than 48 parts by weight relative to 100 parts by weight of PVC, the resin composition becomes too hard. On the contrary, if the content of the polyester plasticizer exceeds 93 parts by weight, the resin composition becomes too soft, so it is preferred to contain 48 to 93 parts by weight of the polyester plasticizer, and more preferably 68 to 87 parts by weight of the polyester plasticizer.

[0045] Examples of acrylic lubricants include copolymers containing alkyl acrylate and / or alkyl methacrylate as essential components, namely, acrylic resins and / or methacrylic resins, etc. In particular, transparent or translucent acrylic resins and / or methacrylic resins are preferably used.

[0046] The higher the molecular weight of the lubricant formed of acrylic resin and / or methacrylic resin, the more the gelation of PVC is promoted, so it is preferable to use a lubricant formed of acrylic resin and / or methacrylic resin with a weight average molecular weight of 400,000 or less. A lubricant formed of acrylic resin and / or methacrylic resin with a weight average molecular weight of 10,000 to 400,000 is more preferred, and a lubricant formed of acrylic resin and / or methacrylic resin with a weight average molecular weight of 10,000 to 300,000 is further preferred.

[0047] When the content of the lubricant formed of acrylic resin and / or methacrylic resin is less than 0.1 parts by weight relative to 100 parts by weight of PVC, the contact friction force generated between the die (mold) provided inside the extruder and the resin composition flowing along the die is not sufficiently reduced, and a flexible tube having uniform wall thickness and pressure resistance cannot be obtained due to foreign matter such as burnt dust inside the extruder and die deposits generated at the die outlet. On the contrary, when it is greater than 3.0 parts by weight, the contact friction force generated between the die in the extruder and the resin composition is excessively reduced, and a flexible tube of a target shape cannot be obtained.

[0048] Therefore, as a lubricating material formed of an acrylic resin and / or a methacrylic resin, it is preferred to contain 0.5 to 1.2 parts by weight of a lubricating material formed of an acrylic resin and / or a methacrylic resin having a weight average molecular weight of 100,000 to 300,000. Moreover, it is more preferred to contain about 0.8 parts by weight of a lubricating material formed of an acrylic resin and / or a methacrylic resin having a weight average molecular weight of about 200,000 to 230,000. As a specific example of an acrylic lubricating material (lubricating material formed of an acrylic resin and / or a methacrylic resin) having a weight average molecular weight of about 200,000 to 230,000, METABLEN (registered trademark) L-1000 manufactured by Mitsubishi Chemical Corporation meets the requirements.

[0049] In the manufacturing process of the flexible tube according to the embodiment of the present invention, a resin composition containing 48 to 93 parts by weight of an adipic acid polyester having a weight average molecular weight of 3,500 to 5,500 and 0.1 to 3.0 parts by weight of a lubricant material composed of an acrylic resin and / or a methacrylic resin having a weight average molecular weight of 10,000 to 400,000 is extruded into a tube using an extruder by a known method to mold the flexible tube.

[0050] The tensile strength and strain of the flexible tube according to the embodiment are set within a predetermined range based on the stress-strain curve, and the flexible tube has high durability and maintains stable performance in applications where repeated elastic deformation and plastic deformation of a roller pump are generated. Therefore, the flexible tube can withstand repeated crushing forces of a roller pump and can stably transport a fluid in a fixed amount.

[0051] In addition, even if the peristaltic part of the roller pump is repeatedly flattened and restored for a long time, it will not break or crack. Moreover, the flexible tube will not plastically stretch with the movement of the roller, and the flow rate will not decrease. The flexible tube of the embodiment of the present invention has a single-layer structure. Therefore, the peeling between layers will not occur like the multi-layer structure.

[0052] Furthermore, adipic acid-based polyesters having a weight average molecular weight of 3,500 to 5,500 are excellent in oil resistance and have little elution, and therefore can be safely used in the medical, food, and pharmaceutical fields.

[0053] It should be noted that the flexible tube of the present invention is not limited to the above-mentioned embodiment. In addition to the above-mentioned components, various additives (heat stabilizer, light stabilizer, ultraviolet absorber, antioxidant, antifogging agent, antistatic agent, etc.) may be blended in the resin composition in a usual amount as required. The size of the flexible tube is not limited, and high durability and safety can be obtained regardless of the size of the flexible tube.

[0054] Example

[0055] Hereinafter, Examples A1 to A7 and Comparative Examples B1 to B6 of the present invention will be described. A plurality of flexible tubes 1 to 12 (inner diameter 4.8 mm, wall thickness 1.6 mm) produced by mixing a thermoplastic resin with a plasticizer were obtained. In addition, a flexible tube (inner diameter 10.0 mm, wall thickness 1.0 mm) produced with the same material ratio as in Examples A1 to A7 and Comparative Examples B1 to B6 was cut to obtain test pieces 1 to 12 molded into a shape similar to a No. 2 dumbbell-shaped test piece described in JIS K 6251. Physical property tests were performed on the flexible tubes 1 to 12 and the test pieces 1 to 12, respectively.

[0056] In Examples A1 to A6, 100 parts by weight of PVC are mixed with plasticizer 1 (adipic acid polyester with a weight average molecular weight of 4,000 to 5,000) as a plasticizer and 0.8 parts by weight of a lubricant (METABLEN (registered trademark) L-1000 of Mitsubishi Chemical Corporation) with a weight average molecular weight of 200,000 to 230,000 formed of an acrylic resin and a methacrylic resin, and the mixture is extruded using an extruder to obtain flexible tubes 1 to 6 and test pieces 1 to 6, wherein the amount of plasticizer 1 as a plasticizer is 50 parts by weight in Example A1, 70 parts by weight in Example A2, 80 parts by weight in Example A3, 85 parts by weight in Example A4, 91 parts by weight in Example A5, and 103 parts by weight in Example 6.

[0057] In Example A7, 85 parts by weight of plasticizer 1 (adipic acid polyester with a weight average molecular weight of 4,000 to 5,000) as a plasticizer and 3.0 parts by weight of an acrylic lubricant with a weight average molecular weight of 200,000 to 230,000 (Mitsubishi Chemical Corporation's METABLEN (registered trademark) L-1000) as a lubricant are mixed with 100 parts by weight of PVC and extruded using an extruder to obtain a flexible tube 7 and a test piece 7.

[0058] In Comparative Example B1, 35 parts by weight of plasticizer 1 (adipic acid polyester with a weight average molecular weight of 4,000 to 5,000) as a plasticizer and 0.8 parts by weight of an acrylic lubricant with a weight average molecular weight of 200,000 to 230,000 (Mitsubishi Chemical Corporation's METABLEN (registered trademark) L-1000) as a lubricant are mixed with 100 parts by weight of PVC and extruded using an extruder to obtain a flexible tube 8 and a test piece 8.

[0059] In Comparative Example B2, 50 parts by weight of plasticizer 2 (adipic acid polyester with a weight average molecular weight of 2000 to 3000) as a plasticizer and 0.8 parts by weight of an acrylic lubricant with a weight average molecular weight of 200,000 to 230,000 (Mitsubishi Chemical Corporation's METABLEN (registered trademark) L-1000) as a lubricant are mixed with 100 parts by weight of PVC and extruded using an extruder to obtain a flexible tube 9 and a test piece 9.

[0060] In Comparative Example B3, 100 parts by weight of PVC was mixed with plasticizer 3 (dioctyl phthalate having a weight average molecular weight of 300 to 500) as a plasticizer, and the mixture was extruded using an extruder to obtain a flexible tube 10 and a test piece 10 .

[0061] In Comparative Example B4, according to the description of Sample 1 of Example 6 of Japanese Patent No. 5475794, a polyolefin material (Engage (registered trademark) 8200 manufactured by Dow Chemicals) was extruded using an extruder to obtain a flexible tube 11 and a test piece 11.

[0062] In Comparative Example B5, according to the description in paragraph 0084 of the above-mentioned Patent Document 2 (Japanese Patent Publication No. 2018-173172), for fluororesin (Kynar Ultraflex of Arkema) and polyurethane (Elastallon C78A of BASF), an outer layer formed of polyurethane is added to the inner layer formed of fluororesin with a wall thickness of 0.2 mm (0.008 in), and the outer layer is extruded with an extrusion molding machine to have a wall thickness of 1.6 mm and an inner diameter of 4.8 mm, thereby obtaining a flexible tube 12 and a test piece 12.

[0063] In Comparative Example B6, PVC was used without mixing a plasticizer. As a result, molding was not possible, and the flexible tube 13 and the test piece 13 could not be obtained.

[0064] First, for the sample samples of Examples A1 to A7 and Comparative Examples B1 to B5, a dissolution test was conducted according to the test method of "Ministry of Health, Labor and Welfare Notice No. 370 of 1959 Standards for Foods, Additives, etc. Chapter 3 Utensils and Containers and Packaging D (Revised: Ministry of Health, Labor and Welfare Notice No. 267 of August 2, 2002)", and the amount of evaporation residue was measured using n-heptane as the leaching liquid. The sample was immersed in all of the flexible tubes 1 to 12 in n-heptane as the leaching liquid, and left at 25°C for 1 hour to prepare the test liquid. In addition, a tensile test was conducted according to the test method of JIS K 6723, and the results are shown in Tables 1 and 2. Figure 1 The test pieces 1 to 12 were used as the samples. The test pieces 1 to 12 were measured 5 times in the test atmosphere of 23±2°C and relative humidity of 50±10%. The average values ​​of the data whose measurement results were included in the confidence interval (95% probability) are shown in Tables 1 and Figure 1 . The testing machine used was Autograph AGS-X manufactured by Shimadzu Corporation, and the tensile test was carried out at a tensile speed of 200 mm / min. In Table 1, for the flexible tubes of Examples 1 to 6, the amount of evaporation residue in the dissolution test is shown; the positive / negative value obtained by first differentiating the approximate formula of the stress-strain curve until fracture; the tensile stress at strains of 100% and 300%; the strain at fracture; the tensile stress at fracture; and the IRHD hardness (based on ISO48 vulcanized rubber or thermoplastic rubber - hardness determination method -, measured by a microscopic standard rubber hardness tester MICRO-IRHD-1 manufactured by Excel).

[0065] [Table 1]

[0066]

[0067] The breaking point is the strain at which the tensile stress obtained by the tensile test reaches the maximum. As an example, Table 2 shows the strain and tensile stress near the breaking point of Example A1.

[0068] [Table 2]

[0069]

[0070] As for the approximate formula of the stress-strain curve, the strain every 0.01 seconds until the breaking point obtained by the tensile test is plotted on the scatter plot, and the sixth-order polynomial (each constant is valid to 30 decimal places) obtained by the polynomial approximation function of the accumulation software (Microsoft Excel365) is used as the approximate formula of the strain, and the approximate value of the strain is calculated. The sixth-order polynomial is obtained by the same method based on the approximate values ​​of the tensile stress and strain until the breaking point obtained by the tensile test, and the sixth-order polynomial is used as the approximate formula of the stress-strain curve until the breaking point. The increase in the approximate value of the tensile stress obtained from the approximate formula of the stress-strain curve is divided by the increase in the approximate value of the strain every 0.01 seconds, and the slope of the approximate formula of the stress-strain curve every 0.01 seconds is calculated and used as the value of the first derivative. In Tables 3 and Figure 2 As an example, the strain at 0.01 to 0.10 seconds and near the breaking point, the approximate value of the strain, the tensile stress, the approximate value of the tensile stress, the value of the first differential, and a graph of the strain and the value of the first differential up to the breaking point of Example 1 are recorded.

[0071] [Table 3]

[0072] Tensile test results of Example A1

[0073]

[0074] Comparative Example B1 broke before the strain reached 300% in the tensile test. This is because the tensile stress is stronger than the elongation, and the elongation is difficult. When used in a roller pump, the durability against repeated deformation is low. Therefore, Comparative Example B1 is not suitable for a roller pump.

[0075] Comparative Examples B2 to B4 had an evaporation residue of more than 150 μg / ml in the dissolution test, and a large amount of plasticizers were eluted, so they could not be safely used in the medical, food, and pharmaceutical fields. In addition, when used in a roller pump, the physical properties also changed, so the durability was also low. Therefore, Comparative Examples B2 to B4 are not suitable for roller pumps.

[0076] Comparative Example B5 broke before the strain reached 300% in the tensile test, and a negative region was formed in the first differentiation of the stress-strain curve until the break. This is because the interlayer peeling between the two different materials occurred. When used in a roller pump, the flow rate was unstable due to the deformation of the flexible tube, and mixed materials were also generated due to the peeling of the inner layer. Therefore, Comparative Example B5 is not suitable for a roller pump.

[0077] Examples A1 to A7 are shown in Table 1 and Figure 1 As shown in (Examples 1 to 6), in the stress-strain curve, the strain does not break until 300%, and the value obtained by first differentiating the approximate formula of the stress-strain curve until breaking is always positive (+). Therefore, the tensile stress increases with the strain until breaking, and especially when used in a roller pump, the discharge amount changes less with time and the durability is high.

[0078] In view of this, in order to ensure a stable flow rate in a roller pump, it is ideal that the flexible tube is formed of a resin composition such that, in a stress-strain curve, the strain does not break up to 300%; the value obtained by first differentiating the approximate formula of the stress-strain curve in the region up to the breaking point is positive (+); and the evaporation residue of the leaching liquid after immersion in n-heptane as a solvent at 25°C for 1 hour is 150 μg / ml or less.

[0079] Next, the performance of Examples A1 to A7 and Comparative Examples B1 to B5 was evaluated as roller pump tubes, and the results are shown in Table 4. For the roller pump, a roller pump head 313X manufactured by Watson Marlow was used for a 313 / WI pump manufactured by Isowatec Corporation, and the resin compositions of Examples 1 to 7 and Comparative Examples B1 to B5 were molded into tubular shapes with a predetermined inner diameter (4.8 mm) and thickness (1.6 mm) using an extruder as a sample tube. The performance of the roller pump tube when n-heptane at 23±3°C was circulated at a roller speed of 150 rpm of the pump head was evaluated based on the following indicators, which are shown in Table 4.

[0080] The “mixed matter” is a result of evaluating the presence or absence of mixed matter in the fluid in two levels: “not generated” is evaluated as ◎, and “generated” is evaluated as ×.

[0081] “Flow rate change rate after 1 hour” is the result of evaluating the flow rate change rate relative to the initial flow rate 1 hour after the start of operation of the roller pump in the following four levels: “less than 3%” is evaluated as ◎, “3% or more and less than 5%” is evaluated as 0, “5% or more and less than 7%” is evaluated as △, and “7% or more” is evaluated as ×.

[0082] The “duration of flow rate” is the time from the start of operation until the flow rate reaches 90% of the initial flow rate, which is evaluated in four levels: “1000 hours or more” is evaluated as ◎, “600 hours or more and less than 1000 hours” is evaluated as 0, “200 hours or more and less than 600 hours” is evaluated as △, and “less than 200 hours” is evaluated as ×.

[0083] [Table 4]

[0084]

[0085] Examples A1 to A7 obtained good evaluation results in all of "mixed matter", "flow rate change rate after 1 hour", and "flow rate duration". In contrast, Comparative Examples B1 to B5 obtained poor evaluation results in any of "mixed matter", "flow rate change rate after 1 hour", and "flow rate duration".

[0086] The tensile stress of Comparative Example B1 was large relative to the strain. As a result of repeated flattening and recovery of the peristaltic part of the roller pump, cracks appeared and ruptures occurred in a short period of time. Damage to the inner layer was also confirmed, and "mixed matter" and "duration of flow rate" became poor evaluation results.

[0087] The weight average molecular weight of the plasticizer in Comparative Examples B2 and B3 was less than 3500, so the "evaporation residue in the dissolution test" was large, and the physical properties changed due to the outflow of the plasticizer, and the "continuation time of the flow rate" became a poor evaluation result. Comparative Example B2 broke in 8 hours, and the "continuation time of the flow rate" became a significantly poor evaluation result. Comparative Example B3 had a large "evaporation residue in the dissolution test", and due to the deformation of the flexible tube, damage to the inner layer was also confirmed, and the "mixed matter" also became a poor evaluation result.

[0088] In Comparative Example B4, the "evaporation residue in the dissolution test" was significantly large, at 12000 μg / ml, resulting in changes in physical properties due to the outflow of substances and damage to the inner surface due to deformation of the flexible tube, resulting in poor evaluation results in all of "mixed matter", "flow rate change rate after 1 hour", and "flow duration".

[0089] Comparative Example B5 obtained a good evaluation result in "evaporation residue in dissolution test", but interlayer peeling occurred, and the evaluation results were poor in all of "mixed matter", "flow rate change rate after 1 hour", and "flow rate duration".

[0090] The evaporation residues of Examples A1 to A7 are less than 150 μg / ml, which meets the dissolution criteria of the test method based on "Ministry of Health, Labor and Welfare Notice No. 370 of 1959, Standards for Foods, Additives, etc., Chapter 3, Apparatus and Containers and Packaging D (Revised: Ministry of Health, Labor and Welfare Notice No. 267 of August 2, 2002)" and can be safely used in medical, food, pharmaceutical fields, etc.

[0091] In addition, Examples A1 to A7 had excellent performance as roller pump tubes, and Examples A2 to A4 and A7 obtained particularly good evaluation results regarding "flow rate change rate after 1 hour" and "flow rate duration".

[0092] Based on the results, it was confirmed that the flexible tube formed by the following resin composition is suitable for the roller pump, in terms of the resin composition, in the stress-strain curve, the strain is not broken until 300%; the value obtained by first differentiating the approximate formula of the stress-strain curve in the region up to the breaking point is positive (+); and the evaporation residue of the leaching liquid after immersion in n-heptane as a solvent at 25°C for 1 hour is 150μg / ml or less. In particular, when the evaporation residue is 120μg / ml or less, the elution of the substance is small, the physical properties of the flexible tube do not change, and the durability is high. The flexible tube of this embodiment has a small amount of elution of the substance and has a prescribed relationship between strain and tensile stress, so it can be used for a roller pump to carry out stable quantitative delivery of fluid. In particular, it has no effect on the human body in the medical, food, and pharmaceutical fields, and can be used safely.

Claims

1. A flexible pipe, characterized in that: It is formed by molding a thermoplastic resin composition into a tube. With respect to the resin composition, In the stress-strain curve, the strain does not break until 300%; The value obtained by first differentiating the approximate expression of the stress-strain curve in the region up to the fracture point is positive; The evaporation residue of the leaching liquid after immersing the resin composition in n-heptane as a solvent at 25° C. for 1 hour is 150 μg / ml or less.

2. The flexible pipe according to claim 1, wherein: The resin composition has the following characteristics: in a stress-strain curve, the tensile stress is 4.5 to 8.0 MPa at a strain of 100%, and the tensile stress is within the range of 11.0 to 19.0 MPa at a strain of 300%.

3. The flexible pipe according to claim 2, wherein: In the stress-strain curve of the resin composition, the tensile stress is 4.9 to 7.0 MPa at a strain of 100%, and the tensile stress is within the range of 12.0 to 15.5 MPa at a strain of 300%. At this time, the IRHD hardness is within the range of 62 to 75 degrees.

4. The flexible pipe according to claim 2, wherein: The flexible tube is used for the peristaltic part of the roller pump.

5. The flexible pipe according to claim 2, 3 or 4, wherein: At least one of phthalic acid-based polyester, adipic acid-based polyester, trimellitic acid-based polyester, and acetylcitric acid-based polyester is contained as a plasticizer.

6. The flexible pipe according to claim 5, wherein: The resin composition contains 48 to 93 parts by weight of a polyester plasticizer having a weight average molecular weight of 3,500 to 5,500, based on 100 parts by weight of a halogen-containing thermoplastic resin.

7. The flexible pipe according to claim 6, wherein: The polyester plasticizer is adipic acid polyester.

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