heat shrinkable film

Abstract

To provide a novel heat-shrinkable film and a method for manufacturing the same.SOLUTION: A method for manufacturing a heat-shrinkable film comprises: a molding step for heating a thermoplastic resin containing a polymer having a repeating unit represented by the general formula (A): -(Ar-S)- [In the general formula (A), the group Ar represents an aromatic hydrocarbon group which may have a substituent group.] to a temperature of 280°C or more to subject it to continuous melt extrusion molding, and cooling the obtained molded film to obtain a yet-to-be-stretched film with a crystallinity of 20% or less; and a stretching step for stretching the yet-to-be-stretched film in a temperature environment less than a crystallization temperature to obtain the heat-shrinkable film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat-shrinkable film and a method for producing the same, a method for producing a heat-resistant film, and a method for producing a heat-resistant member. [Background technology]

[0002] Heat-resistant members made of heat-resistant resins have been used in various fields. For example, polyphenylene sulfide resin is known to be a resin with excellent heat resistance, chemical resistance, mechanical strength, etc. Patent Document 1 discloses a polyphenylene sulfide film made of polyphenylene sulfide resin, which has a heat shrinkage rate of 0.05% in all directions of the film after 5 minutes at 200°C. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-47360 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, polyphenylene sulfide resins are characterized by excellent heat resistance, chemical resistance, mechanical strength, and the like, and these properties of polyphenylene sulfide resins are realized by the crystallization of the polyphenylene sulfide resins. Therefore, conventional polyphenylene sulfide films are characterized by excellent dimensional stability when exposed to high-temperature environments. That is, on the other hand, polyphenylene sulfide films hardly shrink thermally, making them difficult to apply to applications such as covering the surface of components by thermal shrinkage.

[0005] Under these circumstances, a main object of the present invention is to provide a novel heat-shrinkable film. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems of the conventional art, and as a result have found that a novel heat-shrinkable film can be obtained by forming an unstretched film under predetermined production conditions and then stretching it.

[0007] More specifically, the inventors have found that by adopting a method for producing a heat-shrinkable film, which comprises a molding step in which a thermoplastic resin containing a polymer having a repeating unit represented by the general formula (A): -(Ar-S)- (in the general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent) is heated to a temperature of 280°C or higher and subjected to continuous melt extrusion molding, and the obtained molded film is cooled to obtain an unstretched film having a crystallinity of 20% or less, and a stretching step in which the unstretched film is stretched in a temperature environment below the crystallization temperature to obtain a heat-shrinkable film, a film having heat shrinkability can be obtained, even though it is formed from a resin with excellent heat resistance.

[0008] That is, the present invention provides the following aspects of the invention. Item 1. The following general formula (A): -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.] a molding step of heating a thermoplastic resin containing a polymer having a repeating unit represented by the formula (I) to a temperature of 280°C or higher, subjecting it to continuous melt extrusion molding, and cooling the obtained molded film to obtain an unstretched film having a crystallinity of 20% or less; a stretching step of stretching the unstretched film in a temperature environment below the crystallization temperature to obtain a heat-shrinkable film; A method for producing a heat-shrinkable film, comprising: Item 2. The method for producing a heat-shrinkable film according to Item 1, wherein the temperature at which the formed film is cooled is 90°C or lower. Item 3. The method for producing a heat-shrinkable film according to Item 1 or 2, wherein the crystallization temperature is 160°C or lower. Item 4. The method for producing a heat-shrinkable film according to any one of Items 1 to 3, wherein the heat-shrinkable film has a heat shrinkage rate of 1% or more when heated in a gas phase at a temperature of 100°C for 5 minutes. Item 5. The method for producing a heat-shrinkable film according to any one of Items 1 to 4, wherein the heat-shrinkable film has a crystallinity of 10% or less after being placed in a gas phase at a temperature of 90°C for 5 minutes from an environment at a temperature of 25°C. Item 6. The method for producing a heat-shrinkable film according to any one of Items 1 to 5, wherein the heat-shrinkable film is a cylindrical endless film. Item 7. A step of preparing the heat-shrinkable film according to any one of items 1 to 6; a shrinking step of heating the heat-shrinkable film at a temperature equal to or higher than its crystallization temperature to cause heat shrinkage; A method for producing a heat-resistant film, comprising: Item 8. A step of preparing the heat-shrinkable film according to any one of items 1 to 6; placing a member inside the heat-shrinkable film; a covering step of heating the heat-shrinkable film at a temperature equal to or higher than the crystallization temperature to heat-shrink the heat-shrinkable film, thereby covering the member with a heat-resistant film resulting from the heat-shrinkable film; A method for manufacturing a heat-resistant member, comprising: Item 9. The following general formula (A): -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.] The thermoplastic resin contains a polymer having a repeating unit represented by A heat-shrinkable film that has a thermal shrinkage rate of 1% or more when heated in a gas phase at 100°C for 5 minutes. Item 10. The heat-shrinkable film according to Item 9, wherein the heat-shrinkable film has a crystallinity of 10% or less after being transferred from an environment at a temperature of 25°C to a gas phase at a temperature of 90°C for 5 minutes. Item 11. The heat-shrinkable film according to Item 9 or 10, wherein the heat-shrinkable film is a cylindrical endless film. Item 12. A method for producing a heat-resistant film, comprising a shrinking step of heating the heat-shrinkable film according to any one of items 9 to 11 at a temperature equal to or higher than the crystallization temperature to cause heat shrinkage. Item 13. A step of preparing the heat-shrinkable film according to any one of items 9 to 11; placing a member inside the heat-shrinkable film; a covering step of heating the heat-shrinkable film at a temperature equal to or higher than the crystallization temperature to heat-shrink the heat-shrinkable film, thereby covering the member with a heat-resistant film resulting from the heat-shrinkable film; A method for manufacturing a heat-resistant member, comprising: [Effects of the Invention]

[0009] According to the present invention, a novel heat-shrinkable film and a method for producing the same can be provided. Furthermore, according to the present invention, a method for producing a heat-resistant film and a method for producing a heat-resistant member using the heat-shrinkable film can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic perspective view of a case where the heat-shrinkable film of the present invention is a cylindrical endless film. [Figure 2] FIG. 2 is a schematic diagram illustrating a method for covering a member by heat-shrinking a heat-shrinkable film of the present invention in the case where the heat-shrinkable film is a cylindrical endless film. DETAILED DESCRIPTION OF THE INVENTION

[0011] The method for producing a heat-shrinkable film of the present invention is characterized by comprising a molding step of heating a thermoplastic resin containing a polymer having a repeating unit represented by the following general formula (A) to a temperature of 280°C or higher and subjecting it to continuous melt extrusion molding, and cooling the resulting molded film to obtain an unstretched film having a crystallinity of 20% or less, and a stretching step of stretching the unstretched film in a temperature environment below the crystallization temperature to obtain a heat-shrinkable film. By virtue of these characteristics, the method for producing a heat-shrinkable film of the present invention can produce a novel heat-shrinkable film. Specifically, for example, it is possible to produce a heat-shrinkable film formed from a thermoplastic resin containing a polymer having a repeating unit represented by the following general formula (A), which has a heat shrinkage of 1% or more when heated in a gas phase at a temperature of 100°C for 5 minutes.

[0012] -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.]

[0013] Hereinafter, a method for producing the heat-shrinkable film of the present invention, the heat-shrinkable film of the present invention, a heat-resistant film obtained by heat-shrinking the heat-shrinkable film, and a method for producing a heat-resistant member in which a member is covered with a heat-resistant film obtained by heat-shrinking the heat-shrinkable film will be described in detail.

[0014] 1. Manufacturing method of heat-shrinkable film The heat-shrinkable film of the present invention having the above-mentioned heat-shrinkage properties can be suitably produced, for example, by the following production method comprising a molding step and a stretching step.

[0015] (molding process) In the molding process, the compound represented by the following general formula (A): -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.] A thermoplastic resin containing a polymer having a repeating unit represented by the formula: is heated to a temperature of 280°C or higher and subjected to continuous melt extrusion molding, and the obtained molded film is cooled to obtain an unstretched film having a crystallinity of 20% or less.

[0016] In the molding process, first, raw materials such as the thermoplastic resin and, if necessary, fillers and additives described below are heated to a temperature of 280°C or higher, and then molded into a film by continuous melt extrusion molding to obtain a molded film.

[0017] In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent, and is preferably a phenylene group which may have a substituent.

[0018] When the group Ar has a substituent, the substituent is not particularly limited, but from the viewpoint of improving the heat shrinkability of the heat shrinkable film, preferred examples of the substituent include an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom. From the same viewpoint, it is preferable that the group Ar has no substituent, and it is more preferable that the group Ar is a phenylene group.

[0019] In the general formula (A), the polymer in which the group Ar is a phenylene group is polyphenylene sulfide ( PPS ) is a polymer called

[0020] Polyphenylene sulfide is readily available commercially.

[0021] In the present invention, the polymer having a repeating unit represented by general formula (A) may be a homopolymer constituted by the repeating unit, or may be a copolymer with other repeating units.

[0022] The thermoplastic resin may further contain other polymers in addition to the above polymers. Examples of other polymers include polyetherimide (PEI), polyamideimide (PAI), polyetherketone (PEK), polyphenylsulfone (PPSU), etc. These other polymers can be used, for example, to reinforce the above polymers.

[0023] In the thermoplastic resin, the proportion of the polymer having the repeating unit represented by the general formula (A) is preferably about 50 to 100% by mass, more preferably about 80 to 100% by mass. The proportion of the other polymer is preferably about 0 to 20% by mass. When the proportion of the polymer and the other polymer in the thermoplastic resin is within this range, the thermoplastic resin can exhibit a heat shrinkage rate sufficient to cover the surface of the member.

[0024] The melting point of the thermoplastic resin is not particularly limited as long as it exhibits excellent heat resistance, but is preferably about 220 to 380°C, and more preferably about 250 to 340°C.

[0025] In addition to the thermoplastic resin, the heat-shrinkable film may contain a filler or additive as needed. The filler is added as needed for the purpose of increasing the mechanical strength of the covering member obtained by heat-shrinking the heat-shrinkable film of the present invention. As the filler, known fillers can be used, and inorganic fillers such as plate-shaped, flake-shaped, and scale-shaped fillers, carbon black, etc. can be used.

[0026] Examples of inorganic fillers include scaly or thin-flaked mica, mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, plate-like or thin-flaked titanium dioxide, scaly titanate compounds such as potassium titanate and lithium titanate, and boehmite. Among these, preferred fillers include mica, sericite, illite, talc, kaolinite, montmorillonite, scaly titanate compounds, and boehmite. Examples of carbon black include gas black, acetylene black, oil furnace black, thermal black, channel black, ketjen black, and carbon nanofilm. One type of filler may be used alone, or two or more types may be used in combination. When the heat-shrinkable film contains a filler, the filler content is preferably about 3 to 30% by mass.

[0027] Examples of additives include antioxidants, heat stabilizers, thermal conductive agents, plasticizers, light stabilizers, lubricants, antifogging agents, antiblocking agents, slip agents, crosslinking agents, crosslinking aids, adhesives, flame retardants, and dispersants. The additives may be used singly or in combination of two or more. When the heat-shrinkable film contains additives, the content of the additives is preferably about 30 to 60% by mass.

[0028] Known mixing means can be used to mix the raw materials, for example, twin-screw extrusion molding. Known melt extrusion molding means can be used to mix the raw materials, for example, a method using a single-screw extruder and a circular mandrel die for extrusion molding. The thickness of the resulting molded film can be adjusted to the desired thickness by appropriately setting the lip width of the circular mandrel and the extrusion molding conditions. A mandrel such as an air ring may be used at the die outlet to accurately maintain the shape of the film after extrusion. Furthermore, by installing a circular mandrel die at the tip of the twin-screw extruder, the raw materials can be mixed and melt-extruded simultaneously to form a film.

[0029] The heating temperature in continuous melt extrusion molding is 280°C or higher, from the viewpoint of bringing the thermoplastic resin into a moldable molten state and allowing the resulting heat-shrinkable film to exhibit a heat shrinkage sufficient to cover the surface of a component in a low-temperature environment (e.g., about 100°C) (e.g., a heat shrinkage of 1% or more when left standing at 100°C for 5 minutes), and may be appropriately set depending on the thermoplastic resin used as a raw material. The heating temperature is preferably about 290 to 350°C, more preferably about 300 to 340°C.

[0030] In the molding step, the obtained molded film is cooled to obtain an unstretched film with a crystallinity of 20% or less. That is, in the method for producing a heat-shrinkable film of the present invention, it is necessary to cool the molded film at a cooling temperature at which the crystallinity of the unstretched film does not exceed 20%. The temperature at which the unstretched film is cooled is preferably equal to or lower than the glass transition temperature of the thermoplastic resin forming the unstretched film, preferably 90°C or lower, and more preferably 80 to 90°C. For example, since the glass transition temperature of polyphenylene sulfide is 88°C, when polyphenylene sulfide is used as the thermoplastic resin, it is preferable to cool the film at a temperature of 88°C or lower (preferably 80 to 88°C).

[0031] The crystallinity of the unstretched film may be 20% or less, but from the viewpoint of more suitably exhibiting the effects of the present invention, it is preferably 10% or less, more preferably 5% or less, even more preferably 2% or less, and particularly preferably 0%. In the present invention, the method for measuring the crystallinity is as follows.

[0032] <Method for measuring crystallinity> Using a differential scanning calorimeter (e.g., DSC-60 manufactured by Shimadzu Corporation), the heat of crystallization and the heat of fusion are measured in accordance with the measurement method described in JIS K 7121 when the temperature is increased from 30°C to 300°C at a rate of 10°C / min, and calculated using the following formula. Crystallinity = (heat of fusion - heat of crystallization) / estimated heat of fusion at 100% crystallization x 100

[0033] The formed film can be cooled, for example, using a cooling mandrel. More specifically, the melt-extruded molten thermoplastic resin is formed into a film along a mandrel-shaped sizing (sizing mandrel). At this time, the sizing mandrel is set to the cooling temperature.

[0034] The cooling time for cooling the formed film is preferably 5 seconds or more, more preferably 10 seconds or more, and even more preferably 10 to 90 seconds.

[0035] The thickness of the unstretched film is not particularly limited and may be adjusted appropriately depending on the use of the heat-shrinkable film, but is, for example, 300 μm or less, preferably about 10 to 150 μm, and more preferably about 20 to 50 μm.

[0036] (Stretching process) In the stretching step, the film (unstretched film) formed in the above-mentioned molding step is stretched in a temperature environment below the crystallization temperature of the thermoplastic resin forming the unstretched film. This stretching step imparts the heat-shrinkable film with the aforementioned heat-shrinkability. This stretching step may be carried out continuously with the molding step or as a separate step. The film stretching step can be carried out by film stretching using a known stretching device. The film stretching may be simultaneous biaxial stretching or uniaxial stretching in the TD direction only.

[0037] The temperature in the atmosphere in which the stretching process is performed is set to be below the crystallization temperature of the thermoplastic resin forming the unstretched film. Because polymers having repeating units represented by the general formula (1) are crystalline resins, the higher the stretching temperature, the more rapidly the crystallization progresses. The more rapidly the crystallization progresses, the higher the mechanical strength of the film, but the lower the film's heat shrinkage. Therefore, in the present invention, to impart heat shrinkability to the unstretched film, the film is stretched at a temperature below the crystallization temperature. Note that "below the crystallization temperature" refers to a temperature below which the crystallization of the thermoplastic resin forming the unstretched film is accelerated, for example, 124°C or lower, preferably about 88 to 110°C, and more preferably about 90 to 100°C. By selecting a temperature below the crystallization temperature of the thermoplastic resin to prevent excessive crystallization, a heat shrinkage sufficient to coat the surface of a component can be achieved in a low-temperature environment. For example, since polyphenylene sulfide crystallizes at temperatures above 124°C, when polyphenylene sulfide is used as the thermoplastic resin, stretching at a temperature below 124°C is preferred.

[0038] In the stretching process, stretching conditions are set to impart the desired heat shrinkability to the unstretched film. Specifically, the heat shrinkage rate in the TD direction is controlled by the ratio of the outer diameter of the unstretched film to the outer diameter of the stretched film (transverse stretching ratio). The transverse stretching ratio can be set to, for example, 1.10 or more. The shrinkage rate in the MD direction is controlled by the ratio of the speed of the unstretched film entering the stretching section to the speed of the stretched film leaving the stretching section (longitudinal stretching ratio). On the other hand, to obtain a heat-shrinkable film, the longitudinal stretching ratio can be any ratio. Therefore, it is possible to perform transverse stretching alone, with the longitudinal length not fixed but with some freedom. Depending on the intended use, the longitudinal stretching ratio may be set within a range of approximately 0.95 to 1.20.

[0039] The heat-shrinkable film of the present invention is obtained as a long film through the above-mentioned molding and stretching steps, and can be cut to a desired length depending on the size of the member to be covered by heat-shrinking the heat-shrinkable film of the present invention.

[0040] The crystallinity of the heat-shrinkable film obtained by the manufacturing method of the present invention is preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and particularly preferably 2% or less, from the viewpoint of exhibiting excellent heat-shrinkability.

[0041] Furthermore, the heat-shrinkable film obtained by the manufacturing method of the present invention preferably has a crystallinity of 10% or less, more preferably 5% or less, and particularly preferably 2% or less after being placed in a gas phase at a temperature of 90°C for 5 minutes from an environment at a temperature of 25°C.

[0042] The shape of the heat-shrinkable film obtained by the production method of the present invention may be a sheet, a cylinder (tube), etc. For example, from the viewpoint of heat-shrinking the heat-shrinkable film of the present invention to suitably cover the surface of a cylindrical or columnar member, the film is preferably a cylindrical endless film.

[0043] The thickness of the heat-shrinkable film is not particularly limited and may be adjusted appropriately depending on the application of the heat-shrinkable film, but is, for example, 300 μm or less, preferably about 10 to 150 μm, and more preferably about 20 to 50 μm. For example, when the heat-shrinkable film of the present invention is tubular, it is preferable to set the wall thickness M of the tube (see FIG. 1) to such a thickness.

[0044] The heat shrinkable film obtained by the production method of the present invention has a heat shrinkage rate of, for example, 1% or more, preferably 5% or more, more preferably 10% or more, and particularly preferably 20% or more when heated in a gas phase at a temperature of 100°C for 5 minutes. The heat shrinkage rate is measured by the method described in the Examples. When the heat shrinkable film is tubular, the heat shrinkage rate is determined by the method described in the section "2. Heat shrinkable film" below.

[0045] 2.Heat-shrinkable film The heat-shrinkable film of the present invention is formed from a thermoplastic resin containing a polymer having a repeating unit represented by the general formula (A) and is characterized in that the heat shrinkage rate when heated in a gas phase at a temperature of 100°C for 5 minutes is 1% or more.

[0046] The method for producing the heat-shrinkable film of the present invention is not particularly limited, but the film can be suitably produced by employing the production method of the present invention described above in the section "1. Method for producing heat-shrinkable film."

[0047] In the heat-shrinkable film of the present invention, details of the thermoplastic resin containing a polymer having a repeating unit represented by general formula (A), as well as the filler and additives, are as explained above in the section "1. Method for producing heat-shrinkable film."

[0048] As described above, the shape of the heat-shrinkable film of the present invention may be a sheet, a cylindrical (tube), etc. From the viewpoint of heat-shrinking the heat-shrinkable film of the present invention to suitably cover the surface of a cylindrical or columnar member, the film is preferably a cylindrical endless film.

[0049] The thickness of the heat-shrinkable film of the present invention is not particularly limited and may be adjusted appropriately depending on the application of the heat-shrinkable film, but is, for example, 300 μm or less, preferably about 10 to 150 μm, and more preferably about 20 to 50 μm. As described above, for example, when the heat-shrinkable film of the present invention is in the form of a tube, it is preferable to set the wall thickness M of the tube (see FIG. 1) to such a thickness.

[0050] When the heat-shrinkable film of the present invention is tubular, the length L (see FIG. 1) of the tube may be appropriately set depending on the size of the member to be covered, and is not particularly limited, but may be, for example, about 1000 to 4000 mm. The outer diameter N (see FIG. 1) of the tube may be appropriately set depending on the size of the member to be covered, and is not particularly limited, but may be, for example, about 50 to 300 mm.

[0051] The heat-shrinkable film of the present invention has a heat shrinkage rate of 1% or more, preferably 5% or more, more preferably 10% or more, and particularly preferably 20% or more, when heated for 5 minutes in a gas phase at a temperature of 100°C. The heat shrinkage rate is measured by the method described in the Examples. When the heat-shrinkable film is in the form of a tube, the heat shrinkage rate (%) is calculated by cutting the heat-shrinkable tube in the longitudinal direction before and after heat shrinkage, opening the tube, and measuring the circumference of the tube with a vernier caliper, using the following calculation formula: Heat shrinkage rate = (perimeter before heat shrinkage - perimeter after heat shrinkage) ÷ perimeter before heat shrinkage × 100 (%)

[0052] The crystallinity of the heat-shrinkable film of the present invention is preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and particularly preferably 2% or less, from the viewpoint of exhibiting excellent heat-shrinkability.

[0053] Furthermore, the heat-shrinkable film of the present invention preferably has a crystallinity of 10% or less, more preferably 5% or less, and particularly preferably 2% or less after being placed in a gas phase at a temperature of 90°C for 5 minutes from an environment at a temperature of 25°C.

[0054] 3. Manufacturing method of heat-resistant components The heat-resistant member of the present invention is a member whose surface is covered with a covering member obtained by heat-shrinking the heat-shrinkable film of the present invention. The heat-resistant member of the present invention can be produced by placing a member inside the heat-shrinkable film of the present invention and heat-shrinking the heat-shrinkable film to cover the member with the heat-shrinkable film. More specifically, the heat-resistant member of the present invention can be suitably produced by a method comprising the following steps:

[0055] A step of preparing the heat-shrinkable film of the present invention A step of placing a member inside the heat-shrinkable film of the present invention. A coating process in which the heat-shrinkable film of the present invention is heated at a temperature equal to or higher than the crystallization temperature to cause heat shrinkage, thereby coating a member with a heat-resistant film (shrinkable film) formed by the heat-shrinkage of the heat-shrinkable film.

[0056] In the step of placing a member inside the heat-shrinkable film of the present invention, the details of the heat-shrinkable film of the present invention are as described above. The member is not particularly limited, but is preferably a columnar or cylindrical member from the viewpoint of providing heat resistance and the like by suitably covering the outer surface with a heat-resistant member (covering member) heat-shrunk by the heat-shrinkable film of the present invention. Examples of members include those used in fields requiring excellent heat resistance, and specific examples include CFRP rollers.

[0057] (Coating process) In the covering step, a member is placed inside the heat-shrinkable film of the present invention, and the heat-shrinkable film is heated at a temperature equal to or higher than the crystallization temperature to heat-shrink the film and adhere it to the surface of the member. That is, in this covering step, the member is covered with a covering member formed by heat-shrinking the heat-shrinkable film of the present invention, thereby obtaining a heat-resistant member. The heat-shrinking step corresponds to the shrinking step described in the section "4. Method for producing heat-resistant film" below. As described above, the heat-shrinkable film of the present invention exhibits a heat shrinkage rate sufficient to cover the surface of a member in a low-temperature environment (e.g., about 100°C) (e.g., a heat shrinkage rate of 1% or more when left standing at 100°C for 5 minutes). Therefore, the film can be heat-shrunk even at about 100°C, for example, to obtain a suitable heat-resistant member. Note that "above the crystallization temperature" refers to a temperature at which the crystallization of the thermoplastic resin forming the heat-shrinkable film is accelerated, preferably about 120 to 160°C, more preferably about 130 to 150°C. For example, polyphenylene sulfide crystallizes at temperatures of 124° C. or higher, so when polyphenylene sulfide is used as the thermoplastic resin, it is preferable to heat it at a temperature of 124° C. or higher (preferably 124 to 150° C.).

[0058] A schematic diagram for explaining the covering step is shown in Fig. 2. In the covering step, as shown in Fig. 2, the member 2 is placed inside the heat-shrinkable film 1, and in this state the heat-shrinkable film 1 is heated to shrink inward, and the heat-shrinkable film 1 is brought into close contact with the member 2, whereby the heat-shrinkable film 1 covers the surface of the member 2 with a covering member 10 formed by heat shrinkage, thereby obtaining a heat-resistant member.

[0059] The heating temperature in the covering step can be set appropriately depending on the heat resistance temperature of the member, but in the method for producing a heat-resistant member of the present invention, the covering step can be suitably carried out in a relatively low-temperature environment as long as it is at or above the crystallization temperature. From the viewpoint of suitably heat-shrinking the heat-shrinkable film of the present invention and adhering it to the surface of the member, the heating temperature in the covering step is preferably about 120 to 160°C, more preferably about 130 to 150°C. The heating time is set appropriately depending on the size of the heat-shrinkable film and the member, but for example, the above temperature may be maintained for 10 minutes or more, preferably about 10 to 15 minutes, after the heat-shrinkable film reaches the above temperature.

[0060] Coating of a member with the heat-shrinkable film of the present invention can be carried out, for example, in the case of a cylindrical or columnar member, by covering the surface of the member with the heat-shrinkable film of the present invention, leaving it in a free state approximately concentrically, and heating it in a constant temperature bath.

[0061] (Annealing process) The method for producing a heat-resistant member of the present invention may further include an annealing step after the coating step. In the annealing step, the heat-resistant member is heated at a temperature higher than the heating temperature in the coating step. The annealing step is performed as needed to increase the mechanical strength of the heat-resistant member (particularly, to increase the tensile modulus). That is, the annealing step increases the mechanical strength of the coated member made of a thermoplastic resin containing the above-mentioned polymer.

[0062] In the present invention, the heating temperature of the heat-resistant member in the annealing step is preferably higher than the heating temperature in the coating step, specifically, preferably about 160 to 200°C, more preferably about 170 to 180°C.

[0063] The annealing step may be performed by continuously increasing the heating temperature after the heating in the coating step, or by cooling the coated member after the coating step and then heating in the annealing step. The heating time is appropriately set depending on the size of the heat-resistant member, and for example, the above temperature may be maintained for 30 minutes or more, preferably 60 to 90 minutes, after the surface temperature of the heat-resistant member reaches the above temperature.

[0064] The annealing step can be carried out, for example, by heating the heat-resistant member in a constant temperature bath.

[0065] 4. Heat-resistant film manufacturing method The heat-resistant film of the present invention is obtained by heat-shrinking the heat-shrinkable film of the present invention. The heat-resistant film of the present invention can be suitably produced by a method comprising the following steps.

[0066] A step of preparing the heat-shrinkable film of the present invention A shrinking step in which the heat-shrinkable film of the present invention is heated to a temperature equal to or higher than the crystallization temperature to cause heat shrinkage.

[0067] That is, the heat-shrinkable film of the present invention is heated to a temperature equal to or higher than the aforementioned crystallization temperature and heat-shrunk, thereby obtaining the heat-resistant film of the present invention, and if a member is placed inside during the shrinking process, the heat-resistant member of the present invention is obtained.

[0068] In the step of preparing the heat-shrinkable film of the present invention, the details of the heat-shrinkable film of the present invention are as described above. In addition, in the method for producing a covered member of the present invention, the shrinking step is the same as the covering step in "3. Method for producing a heat-resistant member", and may further include the annealing step described above, if necessary. [Example]

[0069] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the present invention, the heat shrinkage rate and the crystallinity of the heat-shrinkable film were measured as follows.

[0070] <Heat shrinkage rate> The heat-shrinkable film (50 mm wide, 500 mm long) of Example 1 described below was transferred from an atmospheric environment at 25°C to a thermostatic chamber at 100°C, where it was heated for 5 minutes and the heat shrinkage percentage was measured. The heat shrinkage percentage was calculated by measuring the width of the film with calipers and using the following formula. The results are shown in Table 1. Heat shrinkage rate = (width before heat shrinkage - width after heat shrinkage) ÷ width before heat shrinkage × 100 (%)

[0071] Furthermore, each heat-shrinkable tube (500 mm long) obtained in Examples 2 and 3 described below was transferred from an atmospheric environment at 25°C to a thermostatic oven at 100°C, heated for 5 minutes, and the heat shrinkage rate was measured. The heat shrinkage rate (%) was calculated by cutting the heat-shrinkable tube longitudinally before and after heat shrinkage, measuring the circumference of the tube with a vernier caliper, and then using the following calculation formula. The results are shown in Table 1. Heat shrinkage rate = (perimeter before heat shrinkage - perimeter after heat shrinkage) ÷ perimeter before heat shrinkage × 100 (%)

[0072] <Crystallinity> The unstretched film and the heat-shrinkable film were each measured for heat of crystallization and heat of fusion using a differential scanning calorimeter (Shimadzu DSC-60) in accordance with the measurement method described in JIS K 7121, when the temperature was raised from 30°C to 380°C at a rate of 10°C / min, and the crystallinity was calculated using the following formula. The results are shown in Table 1. Crystallinity = (heat of fusion - heat of crystallization) / estimated heat of fusion at 100% crystallization x 100

[0073] The heat-shrinkable film was also transferred from an atmospheric environment at 25°C to a thermostatic chamber at 90°C and heated for 5 minutes, after which the crystallinity was calculated in the same manner. The results are shown in Table 1.

[0074] Example 1 A heat-shrinkable film was produced by the following molding and stretching steps. PPS (Polyphenylene sulfide, W300 manufactured by Polyplastics Co., Ltd.) was used. Next, the thermoplastic resin was melted at a barrel temperature of 300°C and extruded through a T-die to perform continuous melt extrusion molding. The resulting molded film (thickness 120 μm) was cooled and solidified using a roll cooled to 85°C (cooling time 5 seconds) to obtain an unstretched film (thickness 120 μm). Next, the unstretched film was stretched 1.2 times in the TD direction using a tenter-type stretching machine at a stretching temperature of 94°C to obtain a heat-shrinkable film (thickness 100 μm). The crystallization temperature (glass transition temperature) of the thermoplastic resin, the cooling temperature and crystallization temperature of the unstretched film, the heat shrinkage rate of the film, the stretching temperature, crystallization temperature, the crystallization degree after heating in a gas phase at 100°C for 5 minutes, and the thickness are summarized in Table 1.

[0075] <Example 2> A heat-shrinkable tube (tubular heat-shrinkable film) was produced by the following molding and stretching steps. PPS (polyphenylene sulfide, W-300 manufactured by Polyplastics Co., Ltd.) was used as a thermoplastic resin and fed into a single-screw extruder with a screw diameter of 30 m and heated and kneaded at 330°C. The material was then melt-extruded through an annular die at a speed of 2.0 m / min to form a molded tube. A sizing mandrel (outer diameter φ6 mm, 30 mm long) was used to circulate pressurized water inside the mandrel, which was set to 85°C, to produce an unstretched tube with an inner diameter of φ5.8 mm and a wall thickness of 100 μm.

[0076] Next, the unstretched tube obtained in the molding process was cut to a length of 1000 mm and expanded by applying internal pressure (0.14 MPa) in a cylinder with an inner diameter of φ7.5 mm heated to 94°C. While maintaining the outer diameter of the tube, it was cooled to a temperature (50°C) below Tg (88°C) to produce a heat-shrinkable tube with an outer diameter of φ7.5 mm and a wall thickness of 80 μm.

[0077] Example 3 A heat-shrinkable tube (tubular heat-shrinkable film) was produced using the following molding and stretching processes. PPS (polyphenylene sulfide, Polyplastics W-300) was used as the thermoplastic resin and fed into a single-screw extruder with a screw diameter of 30 m and heated and kneaded at 330°C. The thermoplastic resin was then melt-extruded through an annular die at a speed of 2.0 m / min to form a molded tube. A sizing mandrel (outer diameter φ40.5 mm, 30 mm long) was used to circulate pressurized water through the mandrel, which was set to 85°C. The resulting unstretched tube (inner diameter φ40 mm, wall thickness 30 μm) was pinched and wound around a core.

[0078] Next, the unstretched tube obtained in the molding process was wound up and moved through a ring of pinch rollers while applying internal pressure while 100°C hot air was blown through a ring-shaped hot air outlet. The internal pressure was adjusted by feedback control to a value that would result in a tube outer diameter of φ50 mm, and the rotation speed of the first pinch roller was set to 1 m / min and the rotation speed of the second pinch roller to 1.2 m / min. The tube was cooled to the temperature (50°C) before the second pinch roller and wound up to produce a heat-shrinkable tube with an outer diameter of φ50 mm and a wall thickness of 25 μm.

[0079] [Evaluation of tensile modulus] The heat-shrinkable film was heated in a thermostatic chamber in an atmospheric environment at 150°C for 30 minutes to heat shrink the film (heat-resistant film) and use it as a sample. The sample was cut into a test piece with the shape and size (20 mm x 250 mm) specified in JIS K 7127, and the tensile modulus of the sample was measured at room temperature at a tension speed of 10 mm / min. The results are shown in Table 1.

[0080] [Table 1] [Explanation of symbols]

[0081] 1...Heat-shrinkable film 2...Components 10...Covering member L: Film length M...film thickness N: Outer diameter of film

Claims

1. The following general formula (A): -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.] a molding step of heating a thermoplastic resin containing polyphenylene sulfide (PPS) having a repeating unit represented by the formula (I) to a temperature of 280°C or higher and subjecting it to continuous melt extrusion molding, and cooling the obtained molded film at a temperature of 80 to 90°C to obtain an unstretched film having a crystallinity of 20% or less; a stretching step of stretching the unstretched film in a temperature environment below the crystallization temperature to obtain a heat-shrinkable film; A method for producing a heat-shrinkable film, comprising:

2. The method for producing a heat-shrinkable film according to claim 1, wherein the temperature at which the formed film is cooled is 80 to 88°C.

3. The method for producing a heat-shrinkable film according to claim 1 or 2, wherein the crystallization temperature is 160°C or lower.

4. The heat shrinkable film has a heat shrinkage rate of 100°C when heated in a gas phase for 5 minutes. The method for producing a heat-shrinkable film according to any one of claims 1 to 3, wherein the heat-shrinkable film thickness is 1% or more.

5. The method for producing a heat-shrinkable film according to any one of claims 1 to 4, wherein the heat-shrinkable film has a crystallinity of 10% or less after being placed in a gas phase at a temperature of 90°C for 5 minutes from an environment at a temperature of 25°C.

6. The method for producing a heat-shrinkable film according to any one of claims 1 to 5, wherein the heat-shrinkable film is a cylindrical endless film.

7. A step of preparing the heat-shrinkable film according to any one of claims 1 to 6; a shrinking step of heating the heat-shrinkable film at a temperature equal to or higher than its crystallization temperature to cause heat shrinkage; A method for producing a heat-resistant film, comprising:

8. A step of preparing the heat-shrinkable film according to any one of claims 1 to 6; placing a member inside the heat-shrinkable film; a covering step of heating the heat-shrinkable film at a temperature equal to or higher than the crystallization temperature to heat-shrink the heat-shrinkable film, thereby covering the member with a heat-resistant film resulting from the heat-shrinkable film; A method for manufacturing a heat-resistant member, comprising:

9. The following general formula (A): -(Ar-S)- (A) [In general formula (A), the group Ar is an aromatic hydrocarbon group which may have a substituent.] The thermoplastic resin is formed from a polyphenylene sulfide (PPS) having a repeating unit represented by A heat-shrinkable film having a crystallinity of 10% or less after being placed in a gas phase at a temperature of 90°C for 5 minutes from an environment at a temperature of 25°C.

10. The heat shrinkable film has a heat shrinkage rate of 100°C when heated in a gas phase for 5 minutes. The heat-shrinkable film according to claim 9, wherein the shrinkage is 1% or more.

11. The heat-shrinkable film according to claim 9 or 10, which is a cylindrical endless film.

12. A method for producing a heat-resistant film, comprising a shrinking step of heating the heat-shrinkable film according to any one of claims 9 to 11 at a temperature equal to or higher than the crystallization temperature to cause heat shrinkage.

13. A step of preparing the heat-shrinkable film according to any one of claims 9 to 11; placing a member inside the heat-shrinkable film; a covering step of heating the heat-shrinkable film at a temperature equal to or higher than the crystallization temperature to heat-shrink the heat-shrinkable film, thereby covering the member with a heat-resistant film resulting from the heat-shrinkable film; A method for manufacturing a heat-resistant member, comprising:

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