WO2021161620A1

WO2021161620A1 - Heat shrink tube

Info

Publication number: WO2021161620A1
Application number: PCT/JP2020/044436
Authority: WO
Inventors: 遼太福本; 太郎藤田; 西川　信也; 清一郎村田
Original assignee: 住友電気工業株式会社; 住友電工ファインポリマー株式会社
Priority date: 2020-02-13
Filing date: 2020-11-30
Publication date: 2021-08-19
Also published as: JPWO2021161620A1

Abstract

The invention is a heat shrink tube comprising a fluoropolymer as the main component and a fatty acid amide, wherein the fluoropolymer includes a fluororubber and a fluororesin. The heat shrink tube has a melting heat amount of between 1 J/g and 12 J/g inclusive at 70°C or higher, as measured with a differential scanning calorimeter.

Description

Heat shrink tube

This disclosure relates to heat shrinkable tubes. This application claims priority based on Japanese Patent Application No. 2020-022886, which is a Japanese patent application filed on February 13, 2020, and incorporates all the contents described in the Japanese patent application. ..

Fluororesin has excellent heat resistance, chemical resistance, and insulation properties, and can be extruded. Therefore, fluororesin is widely used as a main component of heat-shrinkable tubes that cover and protect connections such as electric wires and pipes. There is.

Since the heat-shrinkable tube containing fluororesin has relatively high rigidity, for example, fluororubber or the like is mixed with the heat-shrinkable tube in applications requiring flexibility (see JP-A-2015-39843).

JP-A-2015-39843

The heat-shrinkable tube according to one aspect of the present disclosure contains a fatty acid amide and a fluoropolymer as a main component, and the fluoropolymer contains fluororubber and fluororesin at 70 ° C. or higher as measured by a differential scanning calorimeter. The amount of heat of fusion is 1 J / g or more and 12 J / g or less.

FIG. 1 is a schematic perspective view showing a heat-shrinkable tube according to an embodiment of the present disclosure.

[Issues to be solved by this disclosure]
This heat-shrinkable tube is required to have not only flexibility when coating a base material, but also quality improvement in terms of manufacturing such as shape retention during storage and suppression of sticking between tubes.

The present disclosure has been made based on such circumstances, and provides a heat-shrinkable tube capable of suppressing sticking between tubes while having good flexibility and improving shape retention during storage. With the goal.
[Effect of the present disclosure]
According to the present disclosure, it is possible to suppress sticking between tubes while providing good flexibility, and to improve shape retention during storage.
[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.

The present inventors have found that although the flexibility is improved by reducing the crystal content of the fluoropolymer, the shape retention during storage may be lowered and the tubes may be stuck to each other. In addition, general lubricants are more likely to deteriorate over time than fluoropolymers. Therefore, the heat-shrinkable tube containing the lubricant tends to cause aged deterioration. However, it was also found that by selecting fatty acid amide as a lubricant, it is possible to suppress sticking between tubes while maintaining aging resistance. As a result of further studies based on these findings, it was found that these problems can be solved by combining a fluoropolymer containing a fluororubber and a fluororesin with a fatty acid amide in a specific ratio.

The heat-shrinkable tube has excellent heat resistance because it is mainly composed of a fluoropolymer containing fluororubber and fluororesin. Further, when the amount of heat of melting at 70 ° C. or higher measured by a differential scanning calorimeter is 1 J / g or more, natural shrinkage during storage can be suppressed, so that shape retention during storage can be improved. On the other hand, when the amount of heat of melting is 12 J / g or less, flexibility can be imparted to the heat-shrinkable tube. Further, since the heat-shrinkable tube contains a fatty acid amide as a lubricant, it is possible to suppress sticking between the tubes while maintaining aging resistance. Therefore, the heat-shrinkable tube can suppress sticking between the tubes while having good flexibility, and can improve the shape retention during storage. Here, the "main component" means a component having the highest content, and means a component contained in an amount of 50% by mass or more with respect to the total mass.

The content of the fatty acid amide with respect to 100 parts by mass of the fluoropolymer is preferably 0.1 part by mass or more and 10 parts by mass or less. By setting the content of the fatty acid amide in the above range, it is possible to improve the effect of suppressing the adhesion between the heat-shrinkable tubes while having good aging resistance.

It is preferable that the fluororubber is vinylidene fluoride-based rubber (FKM). Since the fluororubber is a vinylidene fluoride-based rubber, heat resistance, workability, and price are improved.

It is preferable that the fluororesin is polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, or a combination thereof. When the fluororesin is polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer or a combination thereof, the effect of suppressing natural shrinkage during storage and heat resistance can be further improved.

The content of the fatty acid amide is preferably 0.2 parts by mass or more and 5 parts by mass or less. When the content of the fatty acid amide is in the above range, the effect of suppressing the adhesion between the heat-shrinkable tubes can be further improved while maintaining the aging resistance.

The second modulus is preferably 50 MPa or less. When the second modulus is 50 MPa or less, the flexibility of the heat-shrinkable tube can be further improved. Here, the "second modulus" is the slope of a straight line connecting a point on the stress-strain curve and the origin, and is a value measured based on ASTM-D5223-92. It is the slope of the straight line connecting the point on the stress-strain curve and the origin, and is an index of the susceptibility to strain.
[Details of Embodiments of the present disclosure]
Hereinafter, the heat-shrinkable tube according to the embodiment of the present disclosure will be described in detail with reference to the drawings as appropriate.
<Heat shrink tube>
The heat shrinkable tube according to one embodiment of the present disclosure is used as a coating material for protecting an object to be coated. The heat-shrinkable tube is a tube that shrinks in diameter when heated. More specifically, the object to be coated is protected by heating the heat-shrinkable tube into which the object to be coated is inserted on the object to be coated and coating the object to be coated with the contracted body of the heat-shrinkable tube.

The heat-shrinkable tube 1 of FIG. 1 is composed of a cylindrical single-layer base material layer. The heat-shrinkable tube 1 is used, for example, for covering a connection portion between objects to be coated, a terminal of wiring, a metal tube, etc. for protection, insulation, waterproofing, corrosion protection, and the like. Further, the heat-shrinkable tube is formed of a resin composition for forming the heat-shrinkable tube, and the heat-shrinkable tube 1 contains a fatty acid amide and a fluoropolymer as a main component. The heat-shrinkable tube 1 is excellent in heat resistance because it contains a fluoropolymer containing fluororubber and fluororesin as a main component.

The average inner diameter and average thickness of the heat-shrinkable tube 1 are appropriately selected according to the application and the like. The average inner diameter of the heat-shrinkable tube 1 before heat-shrinkage can be, for example, 1 mm or more and 60 mm or less. The average inner diameter of the heat-shrinkable tube 1 after heat-shrinking can be, for example, 30% or more and 50% or less of the average inner diameter before heat-shrinking. The average thickness of the heat-shrinkable tube 1 can be, for example, 0.1 mm or more and 5 mm or less.

The lower limit of the amount of heat of fusion measured by the differential scanning calorimeter of the heat shrink tube 1 at 70 ° C. or higher is 1 J / g, preferably 2 J / g. When the lower limit of the heat of fusion is in the above range, natural shrinkage during storage can be suppressed, so that shape retention during storage can be improved. On the other hand, the upper limit of the heat of fusion is 12 J / g, preferably 8 J / g. When the upper limit of the heat of fusion is within the above range, flexibility can be imparted to the heat shrinkable tube. The heat of fusion can be obtained from the melting curve obtained by differential scanning calorimetry. The melting curve is obtained by performing differential scanning calorimetry under the following conditions. Using a differential scanning calorimeter, raise the temperature of a 5 mg sample from -50 ° C to 300 ° C at a heating rate of 10 ° C / min in a nitrogen atmosphere, and calculate the area of all endothermic peaks that appear after 70 ° C. Ask. If the peak is multimodal, the area of the entire peak is calculated and calculated.

The upper limit of the second modulus of the heat-shrinkable tube 1 is preferably 50 MPa, more preferably 40 MPa. When the second modulus is 50 MPa or less, the flexibility of the heat-shrinkable tube can be further improved. If the second modulus exceeds the upper limit, the flexibility of the heat-shrinkable tube may be insufficient, and it may be difficult to bend and stretch the portion of the object to be coated that is covered with the heat-shrinkable tube. On the other hand, the lower limit of the second modulus of the heat-shrinkable tube is not particularly limited, but is usually about 20 MPa.
[Fluoropolymer]
The fluoropolymer includes fluororubber and fluororesin. Here, the "fluoropolymer" is an organic group in which at least one of the hydrogen atoms bonded to the carbon atom constituting the repeating unit of the polymer chain has a fluorine atom or a fluorine atom (hereinafter, also referred to as "fluorine atom-containing group"). Refers to those replaced with. The fluorine atom-containing group is one in which at least one of the hydrogen atoms in the linear or branched organic group is substituted with a fluorine atom, and examples thereof include a fluoroalkyl group, a fluoroalkoxy group, and a fluoropolyether group. .. The term "fluororubber" refers to a fluoropolymer having no crystals and having a heat of fusion measured by a differential scanning calorimeter of 0 J / g.
(Fluororubber)
Since the heat-shrinkable tube contains fluororubber as a fluoropolymer, the flexibility of the manufactured heat-shrinkable tube is excellent. Examples of the fluororubber include vinylidene fluoride-based rubber (FKM), tetrafluoroethylene-propylene-based rubber (FEPM), tetrafluoroethylene-purple olovinyl ether-based rubber (FFKM), and the like. Among these, FKM having good heat resistance, processability, and price is preferable.
(Fluororesin)
Examples of the fluororesin include polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polyfluoroethylene. Examples thereof include propylene (FEP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE) and the like. Among these, PVDF, THV or a combination thereof is preferable as the fluororesin. Since the melting points of PVDF and THV are relatively low, they can be heat-shrinked at a lower temperature.

The upper limit of the melting point of the fluororesin is preferably 260 ° C, more preferably 150 ° C. If the melting point of the fluororesin exceeds the above upper limit, the shrinkage temperature when the manufactured heat-shrinkable tube is heat-shrinked becomes high, so that the object to be coated may be damaged by heat. On the other hand, the lower limit of the melting point of the fluororesin is not particularly limited as long as the temperature at which the heat-shrinkable tube does not soften or melt during use, but can be, for example, 100 ° C.

The mass ratio of fluororubber to fluororesin is preferably 20/80 or more and 90/10 or less. If the content of the fluororubber is less than the above lower limit, the effect of improving the flexibility of the heat-shrinkable tube formed may be insufficient. On the contrary, if the content of the fluororubber exceeds the upper limit, it is difficult to maintain the shape, which may make it difficult to mold the heat-shrinkable tube. Specifically, when FKM is used as the fluororubber and THV is used as the fluororesin, the mass ratio of the fluororubber to the fluororesin is preferably 20/80 or more and 80/20 or less. When FKM is used as the fluororubber and PVDF is used as the fluororesin, the mass ratio of the fluororubber to the fluororesin is preferably 50/50 or more and 90/10 or less.

The lower limit of the content of the fluoropolymer in the heat-shrinkable tube is preferably 60% by mass, more preferably 80% by mass, still more preferably 90% by mass. On the other hand, the upper limit of the content of the fluoropolymer is preferably 99.9% by mass, more preferably 99.0% by mass. If the content of the fluoropolymer is less than the above lower limit, the heat-shrinking force of the manufactured heat-shrinkable tube is reduced, so that the object to be covered or the like may not be sufficiently covered. In addition, the performance peculiar to the fluoropolymer such as heat resistance may not be sufficiently exhibited in the manufactured heat-shrinkable tube. On the contrary, when the content of the fluoropolymer exceeds the above upper limit, the content of the additive is insufficient, so that the effect of each additive may be insufficient.
[Fatty acid amide]
The heat-shrinkable tube contains a fatty acid amide as a lubricant. By containing fatty acid amide as a lubricant, it is possible to suppress sticking between tubes while maintaining aging resistance. Examples of the fatty acid amide include fatty acid amides in which the fatty acid portion is saturated fatty acids and fatty acid amides in which unsaturated fatty acids are unsaturated fatty acids. Examples of the amide in which the fatty acid portion is a saturated fatty acid include stearic acid amide, lauric acid amide, palmitic acid amide, behenic acid amide, and myristic acid amide. Examples of the amide of an unsaturated fatty acid having a fatty acid moiety include oleic acid amide and erucic acid amide. Examples of other fatty acid amides include bisamides and methylolamides.

As the lower limit of the content of the fatty acid amide with respect to 100 parts by mass of the fluoropolymer, 0.1 part by mass is preferable, and 0.2 part by mass is more preferable. When the content of the fatty acid amide is less than the above lower limit, the effect of suppressing the adhesion between the heat-shrinkable tubes may be reduced. On the other hand, as the upper limit of the content of the fatty acid amide, 10 parts by mass is preferable, and 5 parts by mass is more preferable. If the content of the fatty acid amide exceeds the upper limit, the aging resistance may decrease.

The heat-shrinkable tube 1 may contain other additives, if necessary. Examples of such additives include strength-retaining agents, antioxidants, flame retardants, copper damage inhibitors, colorants, heat stabilizers, ultraviolet absorbers and the like. The content of the additive in the heat-shrinkable tube 1 is more preferably less than 40% by mass, further preferably less than 25% by mass. When the content of the additive is at least the above upper limit, the characteristics of the heat-shrinkable layer may easily vary.

The heat-shrinkable tube has good flexibility, suppresses sticking between tubes, and can improve shape retention during storage. Therefore, the heat-shrinkable tube can be suitably used as a protective material for a covering object for various industrial purposes, for example.
[Manufacturing method of heat shrinkable tube]
The method for producing the heat-shrinkable tube is not particularly limited, but includes, for example, the following steps.
(1) A step of preparing a resin composition for forming a heat-shrinkable tube (hereinafter, also referred to as a resin composition) for forming a heat-shrinkable tube (resin composition preparation step).
(2) Step of extrusion molding a resin composition for forming a heat-shrinkable tube with a melt extrusion molding machine (extrusion molding step)
(3) Step of cross-linking the extruded product by irradiation (cross-linking step)
(4) Step of expanding the diameter of the extruded product to obtain the heat-shrinkable tube (diameter expansion step)
(1) Resin composition preparation step In the resin composition preparation step for forming a heat-shrinkable tube, each resin component of the heat-shrinkable tube, fatty acid amide, and other additives, if necessary, are mixed by a melt mixer or the like. A resin composition for forming a heat-shrinkable tube for forming a heat-shrinkable tube is prepared. As the melting mixer, known ones such as an open roll, a Banbury mixer, a pressurized kneader, a single-screw mixer, and a multi-screw mixer can be used.
(2) Extrusion molding step In the extrusion molding step, the resin composition for forming a heat-shrinkable tube is extruded by a melt extrusion molding machine. Specifically, the resin composition for forming a heat-shrinkable tube is extruded into a cylindrical shape using an extrusion die having a cylindrical space for extruding a layer corresponding to the heat-shrinkable layer. As a result, an extruded product corresponding to the heat-shrinkable layer can be obtained. The dimensions of the extruded product can be designed according to the application and the like.
(3) Cross-linking step In the cross-linking step, the extruded product is cross-linked by irradiation. In this step, by cross-linking the base resin of the extruded product, shrinkage (shape memory effect) when heat-shrinking at a high temperature after the diameter expansion step and shape retention at a high temperature after shrinking are imparted. As a method for cross-linking the base resin, a method of irradiating the resin with radiation (irradiation cross-linking of the base resin) is preferable. Since molding becomes difficult after the base resin is crosslinked by irradiation with radiation, irradiation (crosslinking) with radiation is performed after the extrusion molding step. By irradiating radiation after extrusion molding, molding can be reliably performed and the effect of irradiation with radiation can be sufficiently obtained.

Examples of the radiation used for irradiation cross-linking of the base resin include electron beams (β rays) and γ rays. Since the electron accelerator has a low running cost, a high-power electron beam can be obtained, and control is easy, the electron beam is preferable as the radiation.

The irradiation amount is preferably in the range of 50 kGy or more and 400 kGy or less. When the irradiation amount is less than 50 kGy, the degree of cross-linking becomes small and the shape-retaining property at the time of storage is improved, but the shape-retaining property at a high temperature after shrinkage may decrease. On the other hand, when the irradiation amount exceeds 400 kGy, the shrinkage rate of 50 ° C. or lower increases, the shape retention during storage decreases, and the strength of the tube increases, which may make it difficult to expand the diameter.
(4) Diameter expansion process In the diameter expansion process, the diameter of a cylindrical extruded product is expanded. As a method for increasing the diameter of the extruded product, a known method for increasing the diameter, which is usually used for producing a conventional heat-shrinkable tube, can be used. For example, the diameter is expanded to a predetermined inner diameter by a method of introducing compressed air inside the extruded product while it is heated to a temperature equal to or higher than the melting point, a method of reducing the pressure from the outside, a method of inserting a metal rod inside, or the like. After that, a method of cooling and fixing the shape is used. Such an expansion of the diameter of the extruded product is performed so that the inner diameter of the extruded product is, for example, 1.2 times or more and 4 times or less. By fixing the shape of the extruded product with an expanded diameter, the heat-shrinkable tube can be obtained. Examples of this fixing method include a method of cooling to a temperature equal to or lower than the melting point of the base resin component. In the diameter expansion step, in order to reduce the influence on the surface roughness of the inner surface of the heat-shrinkable tube, the roughness of the metal rod can be reduced, or a coating or a lubricant can be applied. Further, by reducing the speed of diameter expansion, the influence on the surface roughness of the inner surface of the heat shrinkable tube can be reduced. The heat-shrinkable tube is formed by expanding the diameter of the extruded product and fixing the shape in this way.

The heat-shrinkable tube has good flexibility, suppresses sticking between tubes, and can improve shape retention during storage.
[Other Embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is not limited to the configuration of the above-described embodiment, but is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The heat-shrinkable tube of the present disclosure is not limited to the heat-shrinkable tube in which the base material layer is formed in a cylindrical shape shown in FIG. 1, and may be, for example, a heat-shrinkable tube in which a base material layer is formed in a cap shape. Such a heat-shrinkable tube can be manufactured by heat-shrinking and closing one end of a cylindrical heat-shrinkable tube. This heat shrinkable tube can be suitably used for, for example, terminal treatment of wiring.

Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to the following examples.
<Heat shrink tube No. 1 to No. 36>
No. 1 composed of a single layer by the following procedure. 1 to No. Thirty-six heat-shrinkable tubes were formed.
[Fluoropolymer]
The following three types were used as the fluoropolymer.
(1) Fluororubber FKM: "TN50A" manufactured by Solvay (density 1.86 g / cm ³ , Mooney viscosity 23 ML, 121 ° C)
(2) Fluororesin THV: "Dynion 221GZ" manufactured by 3M (melting point 115 ° C)
(3) Fluororesin PVDF: "Kiner 2800" manufactured by Arkema (melting point 140 ° C., specific density 1.78)
[Additive]
The following 9 types of additives were used as additives.
(1) Lubricants Elcaic acid amide ("Alflow P-10" manufactured by NOF CORPORATION)
(2) Lubricants oleic acid amide ("Alflow E-10" manufactured by NOF CORPORATION)
(3) Lubricants Stearic acid amide ("Amid Alflow S-10" manufactured by NOF CORPORATION)
(4) Lubricating stearic acid (NOF's "powdered stearic acid Sakura", melting point 57.5 ° C, molecular weight 284)
(5) Lubricants Zinc stearate ("SZ-2000" manufactured by Sakai Chemical Industry Co., Ltd.)
(6) Lubricants Polyethylene wax (Mitsui Chemicals'"High Wax 420P", melting point 118 ° C, molecular weight 4000, density 0.93 g / cm ³ )
(7) Lubricants A mixture of fatty acid ester and paraffin ("Emaster 430W" manufactured by RIKEN Vitamin Co., Ltd.)
(8) Lubricants Acrylic polymer ("Metabren L-1000" manufactured by Mitsubishi Rayon)
(9) Lubricating silicone ("Trefil R902A" manufactured by Toray Dow Corning, specific density 1.33)
A resin composition for forming a heat-shrinkable tube was prepared using the above-mentioned fluoropolymer and additives. The contents of the fluoropolymer and the additive are shown in Tables 1 and 2. "-" Indicates that the corresponding component is not used.
[Manufacturing of heat shrinkable tubes]
A heat-shrinkable tube was produced by extrusion molding using the above resin composition for forming a heat-shrinkable tube. An extrusion die was used for extrusion molding. Extrusion molding was carried out at a die temperature of 200 ° C. and a linear speed of 10 m / min. Next, the molded product extruded by this molding die was irradiated under the condition of an irradiation amount of 90 kGy. By expanding the diameter of the extruded product thus obtained by a diameter-expanding device and fixing the shape, a No. 1 having an outer diameter of 4.4 mm and an inner diameter of 2.6 mm can be obtained. 1 to No. 36 heat shrinkable tubes were obtained.
[evaluation]
Heat shrink tube No. 1 to No. For 36, 180 ° peeling test, stickiness evaluation, heat of fusion, second modulus, natural shrinkage rate during storage and aging resistance were evaluated.
(180 ° peeling test)
In the 180 ° peeling test, the peeling strength was measured according to JIS-K6854-2 (1999) after pressurizing at room temperature for 1 day under a pressure of 100 kPa. The peel strength value (mN / mm) in the 180 ° peel test shown in Table 1, Table 2 and Table 2 is a value obtained by dividing the value obtained by the test by the width of the test piece.
(Sessility)
Based on the value of the peel strength in the 180 ° peel test, the adhesiveness was evaluated in three stages of A, B and C. The evaluation criteria for the change in the shape of the heat-shrinkable tube were as follows. The smaller the value of the peel strength, the higher the effect of suppressing the sticking between the tubes. If the evaluation is A or B, it is passed.

A: 150 mN / mm or less.
B: More than 150 mN / mm and less than 300 mN / mm.

C: Over 300 mN / mm.
(Chemical amount of melting)
The amount of heat of fusion was determined by DSC measurement under the following conditions.

Using a differential scanning calorimeter (trade name “DSC8500”, manufactured by PerkinElmer), a 5 mg sample was heated from −50 ° C. to 300 ° C. at a heating rate of 10 ° C./min under a nitrogen atmosphere. The areas of all endothermic peaks observed after reaching 70 ° C. at the time of this temperature rise were calculated and obtained.
(Second modulus)
The second modulus of each heat-shrinkable tube obtained was measured according to ASTM-D5223-92. The results are shown in Tables 1 and 2. The second modulus means that the smaller the measured value, the more flexible the heat-shrinkable tube.
(Natural shrinkage rate during storage)
Each heat-shrinkable tube after the diameter-expanding step was stored under a constant temperature condition of 50 ° C., and the natural shrinkage rate after 1 month was measured to use it as an index of shape retention during storage. Then, the shrinkage rate [%] was calculated from the following formula.

Shrinkage rate [%] = {[(Inner diameter of tube before storage at 50 ° C)-(Inner diameter of tube after storage at 50 ° C)] / [(Inner diameter of tube before storage at 50 ° C)-(Each heat shrinkage The inner diameter of the tube before the tube diameter expansion step)]} × 100 was obtained.

If the shrinkage rate after storage at 50 ° C. for 1 month is 20% or less, the product is accepted.
(Aging resistance)
Regarding the aging resistance of each of the obtained heat-shrinkable tubes, the tensile strength and elongation after heating at 250 ° C. for 7 days were measured. The tensile strength [MPa] and elongation [%] of the heat-shrinkable tube were measured according to JIS-K-7162 (1994). The greater the tensile strength and elongation of the heat-shrinkable tube, the more aging-resistant it is.

Tables 1 and 2 show the evaluation results of the 180 ° peeling test of the heat-shrinkable tube, stickiness, heat of fusion, second modulus, natural shrinkage during storage, and aging resistance.

From the results of Tables 1 and 2, No. 1 which contains a fluoropolymer containing fluororubber and fluororesin and a fatty acid amide and has a heat of fusion of 1 J / g or more and 12 J / g or less at 70 ° C. or higher. 1 to No. 23 and No. The heat-shrinkable tubes of 30 had a good effect of suppressing sticking between the tubes and spontaneous shrinkage. In addition, No. 1 in which the fatty acid amide content is 0.1 parts by mass or more and 10 parts by mass or less. 1 to No. The heat-shrinkable tube No. 23 has good aging resistance and is particularly excellent in suppressing sticking between tubes, and has a fatty acid amide content of 0.2 parts by mass or more and 5 parts by mass or less. 1 to No. 14, No. 16-No. 18 and No. 20-No. The heat-shrinkable tube of 22 was particularly excellent in aging resistance.

On the other hand, No. which does not contain fatty acid amide. 27-No. 29 and No. 31-No. The heat-shrinkable tubes of 36 were inferior in the effect of suppressing the sticking between the tubes. In addition, No. 1 having a heat of fusion of less than 1 J / g or more than 12 J / g. 24-No. The heat shrinkable tube of 26 was inferior in suppressing effect or flexibility with respect to the natural shrinkage rate.

From the above results, it was shown that the heat-shrinkable tube can suppress sticking between tubes while having good flexibility, and can improve shape retention during storage.

1 Heat shrink tube

Claims

Contains fatty acid amide and fluoropolymer as the main component,
The fluoropolymer contains fluororubber and fluororesin.
A heat-shrinkable tube having a heat of fusion of 1 J / g or more and 12 J / g or less at 70 ° C. or higher as measured by a differential scanning calorimeter.
The heat-shrinkable tube according to claim 1, wherein the content of the fatty acid amide with respect to 100 parts by mass of the fluoropolymer is 0.1 part by mass or more and 10 parts by mass or less.
The heat-shrinkable tube according to claim 1 or 2, wherein the fluororubber is a vinylidene fluoride-based rubber.
The heat-shrinkable tube according to claim 1, claim 2 or claim 3, wherein the fluororesin is polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer or a combination thereof.
The heat-shrinkable tube according to any one of claims 1 to 4, wherein the content of the fatty acid amide with respect to 100 parts by mass of the fluoropolymer is 0.2 parts by mass or more and 5 parts by mass or less.
The heat-shrinkable tube according to any one of claims 1 to 5, wherein the second modulus is 50 MPa or less.