Laminates and fluororesin molded products

Abstract

To provide a laminate that exhibits excellent heat insulation and heat resistance, and a fluorine resin molding.SOLUTION: According to an embodiment, a laminate is provided. The laminate has a first layer that contains polytetrafluoroethylene and has a solid structure, a second layer that contains polytetrafluoroethylene and has a porous structure, and a third layer that is interposed between the first layer and the second layer and contains molten fluorine resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate and a fluororesin molded article. [Background technology]

[0002] Fluororesin molded products are used in a wide variety of fields, including semiconductor manufacturing equipment, automotive electrical components, office automation equipment, home appliances, medical equipment, and food manufacturing equipment.

[0003] For example, a fluororesin integral vessel made of a fluororesin such as polytetrafluoroethylene (PTFE) is known. The fluororesin integral vessel is produced, for example, by an isostatic molding method. As an example of the isostatic molding method, Patent Document 1 describes a method in which polytetrafluoroethylene powder is pressed at 1500 kg / cm 2 ~10000kg / cm 2 It is described that the molded body is then isostatically pressed under high pressure conditions and then sintered.

[0004] In cases where the tank is not required to be integral (seamless), a welded tank may be used, in which a flat PTFE sheet is welded into a square cylindrical shape with a bottom. For example, these tanks may need to maintain the temperature of the liquid poured into the tank constant. PTFE tubes are also used in semiconductor manufacturing equipment. Since various chemicals pass through the PTFE tube, the PTFE tube may need to be thermally insulated to prevent the properties of the chemicals from changing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-182791 [Patent Document 2] Japanese Patent Application Publication No. 7-001630 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, there are cases where a fluororesin molded product is required to have heat insulation. In this case, for example, a fluororesin sheet (porous sheet) having a porous structure is laminated on the front and back surfaces of a PTFE sheet that are not in contact with a chemical solution. However, in addition to the high non-adhesiveness of fluororesin, the PTFE sheet may be exposed to a high temperature environment in some cases. For example, in the above-mentioned semiconductor manufacturing equipment, when a porous sheet is wrapped around a PTFE tube, the porous sheet may be deformed by exposure to high temperature, and a gap may be generated between the PTFE tube and the porous sheet, or the porous sheet may be detached.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laminate and a fluororesin molded article having excellent heat insulation properties and heat resistance. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a laminate comprising a first layer containing polytetrafluoroethylene and having a solid structure, a second layer containing polytetrafluoroethylene and having a porous structure, and a third layer interposed between the first and second layers and containing a melt-type fluororesin. The ratio of the thickness of the first layer to the thickness of the laminate is within the range of 55% to 70%.

[0009] According to a second aspect of the present invention, there is provided a fluororesin molded article comprising the laminate according to the first aspect. Effect of the Invention

[0010] According to the present invention, it is possible to provide a laminate and a fluororesin molded article having excellent heat insulation properties and heat resistance. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a cross-sectional view illustrating an example of a laminate according to an embodiment. [Diagram 2] FIG. 1 is a cross-sectional perspective view illustrating an example of a fluororesin molded article according to an embodiment. [Diagram 3] FIG. 4 is a perspective view illustrating a schematic configuration of another example of a fluororesin molded article according to an embodiment. [Figure 4] 4 is a cross-sectional view taken along line IV-IV of the fluororesin molded product shown in FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments will be described with reference to the drawings as appropriate. Note that the same reference numerals are used to designate common components throughout the embodiments, and duplicated descriptions will be omitted. Also, each figure is a schematic diagram for explaining the embodiments and for facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known techniques.

[0013] (First embodiment) The laminate according to the first embodiment will be described with reference to the drawings.

[0014] FIG. 1 is a cross-sectional view that shows a schematic example of a laminate. The laminate 10 includes a first layer 1 having a solid structure, a second layer 2 having a porous structure, and a third layer 3 interposed between the first layer 1 and the second layer 2. The third layer 3, which contains a melt-type fluororesin, bonds or welds the first layer 1 and the second layer 2 to each other. The second layer 2 has a mesh structure composed of nodes and fibrils of polytetrafluoroethylene (PTFE), for example. The second layer includes numerous vent holes 2a that exist as gaps in the mesh structure. Although FIG. 1 shows a case where the vent holes 2a are independent pores, the vent holes 2a mainly exist as interconnected pores. The vent holes 2a may include independent pores.

[0015] The laminate 10 may have, for example, a sheet or film shape, or may be flat. The thickness of the laminate 10 is not particularly limited, but may be within the range of, for example, 2 mm to 25 mm.

[0016] The laminate 10 may be a simple sheet, film, or plate, or may constitute at least a part of a fluororesin molded product described later. Examples of the fluororesin molded product include a fluororesin tube shown in Fig. 2 and a fluororesin tank shown in Figs. 3 and 4.

[0017] Since all of the first to third layers constituting the laminate 10 contain fluororesin, the laminate 10 has various properties of fluororesin, namely, chemical resistance, flame retardancy, weather resistance, low friction, non-adhesiveness, etc. A PTFE-containing sheet alone having a solid structure like the first layer is used in various applications, but problems due to the solid structure include, for example, insufficient heat insulating performance and a large mass per unit volume. The laminate 10 according to the embodiment includes a second layer having a porous structure in addition to the first layer, and therefore has the advantage that the heat insulating effect due to the second layer is obtained and the mass per unit volume of the porous structure portion is small.

[0018] However, the second layer having a porous structure may contain residual stress from the time of manufacture, and as described above, the stress may be released in a high-temperature environment, causing the layer to deform.

[0019] The laminate according to the embodiment includes a third layer containing a molten fluororesin between a first layer having a solid structure and a second layer having a porous structure. The third layer bonds the first layer and the second layer, so that even if the second layer having a porous structure is deformed, the first layer having a solid structure follows this deformation. Therefore, gaps are unlikely to occur between the first layer and the second layer, and the excellent heat insulating performance derived from the porous structure of the second layer can be maintained.

[0020] The first to third layers will now be specifically described.

[0021] The first layer contains polytetrafluoroethylene and has a solid structure. The first layer may be made of only polytetrafluoroethylene. The first layer may contain a fluororesin other than PTFE. The first layer may contain at least one additive selected from the group consisting of a liquid repellent material, a hydrophilic material, a conductive material, a coloring material, an antistatic material, and an antibacterial material. The specific gravity of the first layer is, for example, within the range of 2.13 to 2.2.

[0022] The thickness of the first layer can be changed depending on the application of the laminate, but is, for example, within the range of 1 mm to 20 mm.

[0023] The ratio of the thickness of the first layer to the thickness of the laminate is, for example, in the range of 10% to 95%, and preferably in the range of 40% to 70%. If this ratio is too small, for example, the laminate may not have sufficient rigidity. If this ratio is too large, it may not have sufficient heat insulating effect. The ratio may be in the range of 55% to 95%, or may be in the range of 55% to 70%. When the ratio is in the range of 55% to 70%, the laminate can have both high rigidity and sufficient heat insulating performance.

[0024] The first layer may be a sheet manufactured by, for example, the following method. First, a fine powder or molding powder made of PTFE resin is prepared, and an auxiliary is mixed with this to obtain a mixture. The mixture is filled into a mold and pressure molded to obtain a preform. This is extruded into a rod shape, rolled, and then the auxiliary is removed to obtain an unsintered PTFE sheet. The unsintered PTFE sheet is sintered and then stretched to obtain a PTFE sheet having a solid structure.

[0025] The second layer contains polytetrafluoroethylene and has a porous structure. The second layer may be made of only polytetrafluoroethylene. The second layer may contain a fluororesin other than PTFE. The second layer may contain at least one additive selected from the group consisting of a liquid repellent material, a hydrophilic material, a conductive material, a coloring material, an antistatic material, and an antibacterial material.

[0026] The specific gravity of the second layer is, for example, within a range of 0.10 to 2.0, and preferably within a range of 0.60 to 1.20. When the specific gravity of the second layer is within this range, excellent heat insulating effect is achieved.

[0027] The thickness of the second layer is, for example, in the range of 100 μm to 5 mm, and preferably in the range of 500 μm to 5 mm.

[0028] The ratio of the thickness of the second layer to the thickness of the laminate is, for example, in the range of 5% to 90%, and preferably in the range of 30% to 60%. If this ratio is too small, the laminate may not have a good heat insulating effect. If this ratio is too large, for example, the laminate may not have sufficient rigidity.

[0029] The second layer having a porous structure may be a sheet manufactured by, for example, the following method. First, a fine powder containing a PTFE resin is prepared, and 20 to 30 parts by mass of a hydrocarbon oil as an auxiliary is mixed with 100 parts by mass of this powder. For example, the fine powder may have an average particle size of 250 μm to 800 μm. Here, the average particle size refers to D50, which is the particle size corresponding to 50% of the cumulative number of particles in the particle size distribution measured based on the laser diffraction scattering method.

[0030] The mixture is stirred to be homogenous, and then the paste is extruded and preformed, for example, into a rod shape. The preform obtained is rolled, for example, using a metal rolling roll. Next, the auxiliary agent is removed to obtain an unsintered PTFE tape. The thickness of the unsintered PTFE tape is, for example, within a range of 50 μm to 600 μm. In this specification, "unsintered" means that sintering has not been performed in a temperature environment equal to or higher than the melting point of the PTFE resin.

[0031] The unsintered PTFE tape is uniaxially stretched in the direction in which it was previously rolled, i.e., in the machine direction (MD), at a stretch ratio of 1.5 to 30 times in a temperature environment below the melting point to obtain an unsintered PTFE sheet. The temperature during uniaxial stretching is, for example, within the range of 50°C to 320°C. Fibrils are drawn between the nodes by stretching at such a temperature below the melting point. As a result, a network structure is formed in the PTFE tape, and a porous, unsintered PTFE sheet can be obtained. The thickness of the obtained PTFE sheet is, for example, within the range of 50 μm to 500 μm.

[0032] Then, a PTFE sheet corresponding to the second layer having a porous structure can be obtained by baking at a temperature equal to or higher than the melting point of PTFE. The baking at a temperature equal to or higher than the melting point is performed, for example, in an environment of 350°C to 420°C for 0.1 to 600 seconds.

[0033] The third layer includes a melt-type fluororesin. The melt-type fluororesin is, for example, a fluororesin having melt fluidity, with a melt flow rate in the range of 2 g / 10 min to 40 g / 10 min. The melt-type fluororesin may be, for example, at least one selected from the group consisting of perfluoroalkoxyalkane (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), perfluoroethylenepropene copolymer (FEP), and polyvinylidene fluoride (PVDF). From the viewpoint of excellent heat resistance, the melt-type fluororesin is preferably PFA.

[0034] The thickness of the third layer is, for example, in the range of 10 μm to 500 μm, and preferably in the range of 25 μm to 100 μm.

[0035] The laminate according to the embodiment can be produced, for example, by the following method. First, a sheet made of a molten fluororesin is laminated on a PTFE sheet having a solid structure produced by the above-mentioned method, and a PTFE sheet having a porous structure produced by the above-mentioned method is further laminated on the sheet. Next, the laminate of this three-layer structure is subjected to a heat-sealing press, whereby the molten fluororesin melts to obtain the laminate according to the embodiment. The method of heat-sealing press is not particularly limited, but can be carried out, for example, by using a roll laminator.

[0036] The temperature during the roll lamination is, for example, within a range of 360° C. to 420° C., the line pressure within a range of 20 N / cm to 60 N / cm, and the roll speed within a range of 1 m / min to 4 m / min. By performing lamination under such conditions, the first layer and the second layer can be fused together via the third layer without crushing the pores of the second layer having a porous structure.

[0037] Second embodiment The fluororesin molded article according to the second embodiment includes the laminate according to the first embodiment. That is, at least a portion of the fluororesin molded article is composed of the laminate according to the first embodiment. Fig. 2 is a cross-sectional perspective view of a fluororesin tube 20, which is an example of the fluororesin molded article according to the second embodiment. At least a portion of the fluororesin tube 20 is composed of the laminate 10 described in the first embodiment.

[0038] Specifically, the fluororesin tube 20 comprises a first layer 1 having a solid structure, a second layer 2 having a porous structure, and a third layer 3 interposed between the first layer 1 and the second layer 2. The first layer 1, the second layer 2, and the third layer 3 all have an annular cylindrical shape. The fluororesin tube 20 formed by laminating these three layers also has an annular cylindrical shape. The outer circumferential surface of the first layer 1 contacts the third layer 3, and the inner circumferential surface of the second layer 2 also contacts the third layer 3. The third layer 3 bonds or welds the first layer 1 and the second layer 2 together.

[0039] The total thickness of the fluororesin tube 20 is, for example, within a range of 2 mm to 15 mm. The thickness of the first layer is, for example, within a range of 1.5 mm to 10 mm. The thickness of the second layer is, for example, within a range of 500 μm to 5 mm. The thickness of the third layer is, for example, within a range of 10 μm to 500 μm.

[0040] The fluororesin tube 20 can be manufactured, for example, by the following method. First, PTFE powder is compressed into a tube shape and then sintered to obtain a tubular molded body. A PFA film is wound around the outer periphery of the obtained tubular molded body as a melt-type fluororesin. A PTFE sheet having a porous structure is further wound around the film, and these are heated together. In this way, the fluororesin tube 20 can be obtained. As described in the first embodiment, a melt-type fluororesin other than PFA may be used.

[0041] Next, another example of the fluororesin molded product according to the second embodiment will be described with reference to Figs. 3 and 4. Figs. 3 and 4 show a fluororesin welded tank 30. The fluororesin welded tank 30 may have, for example, a container structure. Specifically, the container structure may have a flat plate portion as a bottom plate and a frame-shaped wall portion. The fluororesin welded tank 30 is a square tank (for example, a box-shaped single tank) including a rectangular bottom plate 4 and frame-shaped walls 5a to 5d extending in a direction intersecting with the main surface direction of the bottom plate 4. At least a part of the bottom plate 4 and the frame-shaped walls 5a to 5d is composed of the laminate according to the first embodiment. Fig. 4 shows, as an example, a case where the entire walls 5a to 5d are composed of the laminate according to the first embodiment.

[0042] Each of the walls 5a to 5d is composed of a laminated body consisting of a first layer 1, a second layer 2, and a third layer 3. In each of the walls 5a to 5d, the first layer 1 having a solid structure is located on the inner wall side of the fluororesin welding tank 30. On the other hand, in each of the walls 5a to 5d, the second layer 2 having a porous structure is located on the outer wall side of the fluororesin welding tank 30. The inner wall of the fluororesin welding tank 30 is composed of four first layers 1 provided in the walls 5a to 5d provided in a frame shape. The frame-shaped inner wall is welded to the bottom plate 4 to form a container structure. In addition, a second layer having a porous structure is laminated on the outer wall side of the first layer 1 provided in each wall, via a third layer containing a molten fluororesin. That is, as shown in FIG. 4, the wall 5d is a laminated body in which the first layer 1, the third layer 3, and the second layer 2 are laminated in this order from the inner wall side to the outer wall side. The other wall portions 5a to 5c have the same structure. The bottom plate 4 may further include a second layer having a porous structure, in this order, via a third layer containing a melt-type fluororesin.

[0043] Since each of the walls 5a-5d has the second layer 2 having a porous structure, the fluororesin welded tank 30 has high heat insulating performance. Therefore, the temperature of the liquid poured into the tank can be made less likely to change compared to a case in which the walls 5a-5d are made only of PTFE having a solid structure, for example.

[0044] It is desirable that each part constituting the fluororesin welded tank 30 have a thickness of 5 mm or more. By having each part have a sufficient thickness, the mechanical strength of the welded tank can be increased. In the fluororesin welded tank 30 shown in Figs. 3 and 4, it is desirable that the thickness of the bottom plate 4 is 5 mm or more, and that the thickness of each of the frame-shaped walls is 5 mm or more. Meanwhile, the total thickness of each part constituting the fluororesin welded tank 30 may be, for example, 20 mm or less. If the total thickness is 20 mm or less, increases in weight and costs can be suppressed.

[0045] The thickness of the first layer provided in each wall portion is preferably within a range of 3 mm to 20 mm. Having the thickness of the first layer within this range has the effect of suppressing deformation such as warping and swelling. Furthermore, the thickness of the second layer provided in each wall portion is preferably within a range of 1 mm to 10 mm. Having the thickness of the second layer within this range provides excellent heat insulation effects.

[0046] The fluororesin welded tank according to the embodiment can be obtained, for example, by preparing a plurality of the laminates according to the first embodiment and then welding these laminates together to form a tank structure.

[0047] Although a single tank is used as an example in Figures 3 and 4, the present invention is not limited to this and can be applied to a double tank, a single tank divided into multiple spaces, a round tank, a triangular tank, a polygonal tank, etc.

[0048] The present invention is not limited to the above-mentioned embodiment, and can be modified in various ways in the implementation stage without departing from the gist of the invention. In addition, each embodiment may be implemented in combination as appropriate as possible, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed multiple constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, if the problem described in the "Problem to be Solved by the Invention" column can be solved and the effect described in the "Effect of the Invention" column can be obtained, the configuration from which the constituent elements are deleted can be extracted as the invention. The invention as described in the claims of the original application is set forth below. [1] A first layer comprising polytetrafluoroethylene and having a solid structure; A second layer including polytetrafluoroethylene and having a porous structure; a third layer interposed between the first layer and the second layer, the third layer including a melt-type fluororesin. [2] The laminate according to [1], wherein the specific gravity of the first layer is within a range of 2.13 to 2.2. [3] The laminate according to [1] or [2], wherein the specific gravity of the second layer is within the range of 0.10 to 2.0. [4] The laminate according to any one of [1] to [3], wherein the melt-type fluororesin is a perfluoroalkoxyalkane. [5] A fluororesin molded product comprising the laminate according to any one of [1] to [4]. [Explanation of symbols]

[0049] 1...first layer, 2...second layer, 3...third layer, 4...bottom plate, 5a, 5b, 5c, 5d...wall portion, 10...laminate, 20...fluororesin tube, 30...fluororesin welded tank.

Claims

1. A first layer comprising polytetrafluoroethylene and having a solid structure; A second layer comprising polytetrafluoroethylene and having a porous structure; a third layer interposed between the first layer and the second layer and including a melt-type fluororesin, A laminate, wherein the ratio of the thickness of the first layer to the thickness of the laminate is within a range of 55% to 70%.

2. 2. The laminate according to claim 1, wherein the specific gravity of the first layer is within a range of 2.13 to 2.

2.

3. 3. The laminate according to claim 1, wherein the specific gravity of the second layer is within a range of 0.10 to 2.

0.

4. 4. The laminate according to claim 1, wherein the melt-type fluororesin is a perfluoroalkoxyalkane.

5. A fluororesin molded article comprising the laminate according to any one of claims 1 to 4.

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