Fluororesin powder and molded body thereof

Abstract

To provide fluororesin powder with which it is possible to improve mechanical properties of a molded body using only PTFE after subjected to a heating step, without using an unheated fluororesin.SOLUTION: A fluororesin powder includes a polytetrafluoroethylene resin (A) whose melting point is 333°C or below, and a modified polytetrafluoroethylene resin (B) whose melting point is 333°C or below.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a fluororesin powder and a molded article thereof, and more particularly to a powder and a molded article using a fluororesin that has a history of being heated to a temperature equal to or higher than its melting point, such as a recycled product. [Background technology]

[0002] Fluorine resins are synthetic resins with excellent heat resistance, electrical insulation, and weather resistance, and are widely used in industrial fields such as chemical materials, electrical and electronic parts, semiconductors, and automobiles. When fluororesins such as polytetrafluoroethylene (PTFE) that have been heat-treated (sintered) are reused as raw material powder, there is a problem that the mechanical strength of the resulting molded body is significantly reduced. Various studies have been conducted on methods of utilizing heat-treated (sintered) fluororesins, for example, as shown in Patent Documents 1 to 10. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4714310 [Patent Document 2] JP 2015-108126 A [Patent Document 3] Patent No. 6612001 [Patent Document 4] JP 2003-245983 A [Patent Document 5] Special Publication No. 4-23658 [Patent Document 6] Patent Publication No. 2022-159201 [Patent Document 7] Patent Publication No. 2022-159202 [Patent Document 8] Patent Publication No. 2022-159203 [Patent Document 9] Patent Publication No. 2022-159204 [Patent Document 10] Patent Publication No. 2022-159205 Summary of the Invention [Problem to be solved by the invention]

[0004] At present, the main technology under consideration is, for example, mixing heated fluororesin with unheated fluororesin, which does not necessarily provide sufficient effects in terms of reducing the environmental load or raw material costs. In particular, molded products recycled from PTFE that has been subjected to a heating process have a problem in that mechanical properties such as tensile strength and tensile elongation are significantly reduced.

[0005] An object of the present invention is to provide a fluororesin powder that can improve the mechanical properties of a molded article made using only PTFE that has been subjected to a heating process, without using unheated fluororesin. [Means for solving the problem]

[0006] According to the present invention, the following fluororesin powder and the like are provided. 1. A fluororesin powder comprising: a polytetrafluoroethylene resin (A) having a melting point of 333°C or lower; and a modified polytetrafluoroethylene resin (B) having a melting point of 333°C or lower. 2. The storage modulus G' of the modified polytetrafluoroethylene resin (B) at a temperature of about 300°C when measured under conditions of a frequency of 1 Hz and a strain of 0.3% is 1.0 x 10 5 2. The fluororesin powder according to 1, having a viscosity of 0.1 Pa or less. 3. The polytetrafluoroethylene resin (A) has a median diameter D 50 3. The fluororesin powder according to 1 or 2, which is a powder having a size of 20 μm to 500 μm. 4. The modified polytetrafluoroethylene resin (B) has a median diameter D 50 4. The fluororesin powder according to any one of 1 to 3, which is a powder having a size of 20 μm to 500 μm. 5. The fluororesin powder according to any one of 1 to 4, wherein the content of the modified polytetrafluoroethylene resin (B) is 5 mass % or more based on the total content of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B). 6. The fluororesin powder according to any one of 1 to 4, wherein the content of the modified polytetrafluoroethylene resin (B) is 20 mass % or more based on the total content of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B). 7. A molded article obtained by molding the fluororesin powder according to any one of 1 to 6. 8. The molded article according to 7, having a tensile strength of 15 MPa or more. 9. The molded article according to 7 or 8, having a tensile elongation of 100% or more. 10. The molded article according to any one of 7 to 9, having a specific gravity of 1.81 or more. 11. A step of pulverizing the polytetrafluoroethylene resin molded body and the modified polytetrafluoroethylene resin molded body; mixing the polytetrafluoroethylene resin powder obtained in the above step with the modified polytetrafluoroethylene resin powder. Effect of the Invention

[0007] According to the present invention, it is possible to provide a fluororesin powder that can improve the mechanical properties of a molded article using only PTFE that has been subjected to a heating process, without using unheated fluororesin. [Brief description of the drawings]

[0008] [Figure 1] 1A to 1C are diagrams illustrating a method for producing a molded article according to the present invention. [Diagram 2] FIG. 1 is a diagram showing the results of measuring the storage modulus G′ of each PTFE. [Diagram 3] 1 shows stress-strain curves measured by a tensile test for the molded bodies produced in the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The fluororesin powder and molded article according to the present invention will be described below. In this specification, "x to y" represents a numerical range of "x or more, y or less." When there are multiple lower limit values, such as "x or more," or multiple upper limit values, such as "y or less," for one technical item, any combination of the upper limit values ​​and lower limit values ​​may be selected.

[0010] [Fluororesin powder] The resin fluororesin powder according to one embodiment of the present invention contains a polytetrafluoroethylene resin (A) and a modified polytetrafluoroethylene resin (B). The resin (A) and the resin (B) are characterized in that their melting points are both 333°C or lower. The fact that the melting point of polytetrafluoroethylene resin (hereinafter sometimes referred to as PTFE) is 333°C or lower means that the PTFE has been heated to a temperature equal to or higher than its melting point in the past. This fact is also disclosed in Patent Documents 6 to 10. In this embodiment, for both homo-PTFE and modified PTFE, a resin having a history of being heated to a temperature equal to or higher than its melting point in the past, such as a recycled product, is used.

[0011] The polytetrafluoroethylene resin (homo PTFE) (A) can be used without any particular limitation as long as it has a melting point of 333° C. or less. For example, recycled products recovered from industrially commercially available molded articles of homo PTFE can be used. The modified polytetrafluoroethylene resin (modified PTFE) (B) can also be used without any particular limitation so long as it has a melting point of 333° C. or less, and examples of such resins include recycled products recovered from molded bodies of modified PTFE that are commercially available on an industrial scale.

[0012] Homo-PTFE is a homopolymer of tetrafluoroethylene. Modified PTFE is a copolymer of tetrafluoroethylene and a modifying monomer. Examples of the modified monomer include perfluoroolefins such as hexafluoropropylene (HFP), hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF), perhaloolefins such as chlorotrifluoroethylene, perfluorovinyl ether, perfluoroallyl ether, (perfluoroalkyl)ethylene, and ethylene. The modified monomer may be one type or multiple types.

[0013] In one embodiment, the modified PTFE (B) is a PTFE modified with a perfluoroalkyl vinyl ether represented by the following formula (1). CF2=CF-OR f (1) (In formula (1), R f is a perfluoroalkyl group having 1 to 10 carbon atoms, or a perfluoroorganic group represented by the following formula (2): [ka] (In formula (2), n is an integer of 1 to 4.)

[0014] Examples of the perfluoroalkyl group having 1 to 10 carbon atoms in the formula (1) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, etc. A perfluoropropyl group is preferred.

[0015] The proportion of the perfluoroalkyl vinyl ether polymerization unit represented by the above formula (1) is preferably 1% by weight or less, and more preferably in the range of 0.001% by weight to 1% by weight, which makes it easier for fusion between powder particles to occur during firing, and the molded product obtained after heating has excellent strength.

[0016] In one embodiment, the storage modulus G' of the modified PTFE (B) at a temperature of about 300°C when measured under conditions of a frequency of 1 Hz and a strain of 0.3% is 1.0 x 10 5 Pa or less. Storage modulus G' at around 300°C is 1.0×10 5 Pa or less means that the modified PTFE has been previously heated to a temperature above its melting point. The modified PTFE exhibiting the above-mentioned hot behavior can be obtained, for example, by adjusting the heating rate (e.g., 0.01 to 20°C / min) when heat-treating an unheated resin, the maximum temperature (e.g., a temperature equal to or higher than the melting point (327°C), e.g., 327°C to 400°C) and the holding time (1 minute to 4.5 hours), the pressure applied in the pressurization treatment before heat treatment (e.g., 10 MPa to 100 MPa), etc.

[0017] In one embodiment, the homo-PTFE (A) has a median diameter D 50 The median diameter D of homo-PTFE (A) is 20μm to 500μm. This makes it easier to obtain dense compacts. 50 is 50 μm or more, 100 μm or more, 150 μm or more, or 180 μm or more. In addition, the median diameter D 50 is 450 μm or less, 400 μm or less, or 350 μm or less.

[0018] In one embodiment, the modified PTFE (B) has a median diameter D 50 The median diameter D of the modified PTFE (B) is 20 μm to 500 μm. This makes it easier to obtain dense molded products. 50 is 50 μm or more, 100 μm or more, 150 μm or more, or 180 μm or more. In addition, the median diameter D 50 is 450 μm or less, 400 μm or less, or 350 μm or less. The median diameter of the powder D 50 is measured by the method described in the Examples.

[0019] The resin fluororesin powder according to this embodiment can be obtained, for example, by a production method including the steps of pulverizing a molded body of polytetrafluoroethylene resin and a molded body of modified polytetrafluoroethylene resin, and mixing the polytetrafluoroethylene resin powder (homo-PTFE (A) powder) obtained in the pulverization step with the polytetrafluoroethylene resin powder (modified PTFE (B) powder).

[0020] In the pulverization step, the pulverization method is not particularly limited as long as it can pulverize the molded body to a desired particle size. For example, a mixer, a hammer mill, a jet mill, a stone grinder, or a freeze grinder can be used. The pulverization may be performed at once using one type of tool, or may be performed stepwise using multiple types of tools. For example, homo-PTFE and modified PTFE, which are individual piece molded bodies, may be pulverized to a desired particle size in a mixer, or the homo-PTFE and modified PTFE in the individual piece form may be pulverized to a predetermined particle size in a mixer and then pulverized to the desired particle size in a hammer mill.

[0021] Alternatively, freeze-pulverization may be employed in which the homo-PTFE and modified PTFE molded bodies are cooled to a frozen state and pulverized. In the freeze-pulverization, it is preferable to cool the molded bodies to a temperature below the glass transition temperature of the resin. For example, it is preferable to cool the molded bodies to a temperature below -190°C, below -196°C, or below -250°C. The homo-PTFE molded article and the modified PTFE molded article may be mixed in advance and crushed simultaneously, or each may be crushed separately.

[0022] The homo-PTFE (A) powder obtained in the above-mentioned pulverization step and the modified PTFE (B) powder are mixed to obtain the fluororesin powder of the resin according to this embodiment. The mixing method is not particularly limited, and a known device such as a stirrer can be used. In one embodiment, the content of the modified PTFE (B) is 5% by mass or more based on the total of the homo-PTFE (A) and the modified PTFE (B), whereby the effect of blending the modified PTFE (B) is significantly exhibited, and the tensile elongation of the obtained molded article can be improved. Furthermore, when the content of the modified PTFE (B) is 20% by mass or more, the rigidity of the obtained molded article is increased. The content of the modified PTFE (B) is 95% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0023] [Molded body] A molded article according to one aspect of the present invention is obtained by molding the above-mentioned fluororesin powder of the present invention. The molded article of this embodiment may contain optional components other than the fluororesin powder of the present invention, as long as the effects of the present invention are not lost. Examples of optional components include flame retardants, flame retardant auxiliaries, pigments, antioxidants, reflectivity imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, foaming agents, and fillers. The total content of the optional components in the molded article is usually 50% by mass or less. In one embodiment, the molded body does not contain any other fluororesin than the above-mentioned fluororesin powder of the present invention.

[0024] In one embodiment, the tensile strength of the molded body may be 15 MPa or more, 18 MPa or more, or 20 MPa or more. The upper limit of the tensile strength of the molded article is not particularly limited, but is usually 50 MPa or less. The tensile strength of the molded article is measured by the method described in the Examples.

[0025] In one embodiment, the tensile elongation of the molded body may be 100% or more, 150% or more, or 200% or more. The upper limit of the tensile strength of the molded article is not particularly limited, but is usually 500% or less. The tensile elongation of the molded article is measured by the method described in the Examples.

[0026] In one embodiment, the molded article has a maximum tensile stress of 14 MPa or more in a range of tensile elongation of 0% to 50%. The molded article of this embodiment has improved rigidity by mixing homo-PTFE (A) and modified PTFE (B).

[0027] In one embodiment, the specific gravity of the molded body is 1.81 or more. The molded body of this embodiment has a high density and therefore has excellent mechanical properties. The specific gravity may be 2.00 or more, 2.10 or more, or 2.17 or more. Usually, it is 2.19 or less. The specific gravity of the molded product is measured by the method described in the Examples.

[0028] The molded article of this embodiment can be obtained, for example, by a production method including the following steps (1) and (2). (1) A step of filling the above-mentioned fluororesin powder of the present invention into a mold and applying pressure (2) A process in which the mold filled with powder is heated to bake the powder filled in the mold.

[0029] (Step (1) Pressurizing the powder) FIG. 1 is a diagram for explaining the method for producing a molded article of the present invention. The above-mentioned fluororesin powder 10 of the present invention is filled into a metal mold and pressurized. The pressurized powder is compression molded in the metal mold (see FIG. 1(a)).

[0030] The median diameter D of the modified PTFE resin powder of one embodiment of the present invention to be filled into the mold 50 is preferably 20 μm to 500 μm. This makes it easier for the PTFE powder to exhibit fusibility when the molded body of the powder is heated and sintered in step (2) described later, and the molded body obtained after heating becomes dense and has excellent strength. The smaller the particle size of the powder, the higher the strength of the molded body obtained after reheating tends to be.

[0031] The applied pressure may be 5 MPa to 100 MPa, 20 MPa to 60 MPa, or 30 MPa to 50 MPa. By applying pressure within the above range, when the molded body obtained in this step is heated and sintered in the step (2) described below, adhesion between the PTFE powder particles is easily exhibited, and the molded body obtained after heating has excellent strength.

[0032] (Step (2) Firing of Molded Body) The mold filled with the powder is heated to sinter the powder filled in the mold (see Figures 1(b) and (c)). The firing temperature may be from 300°C to 400°C, from 330°C to 370°C, or from 360°C to 370°C. By firing within the above temperature range, the fluidity of the PTFE constituting the molded body 11 is appropriately increased, fusion between the PTFE powder particles 10 is facilitated, and the molded body obtained after this step has excellent strength.

[0033] The sintering of the molded body can be carried out, for example, by placing a mold filled with the powder into a heating furnace, raising the temperature inside the heating furnace at a predetermined heating rate, and holding the temperature at the sintering temperature for a predetermined period of time. When the temperature inside the furnace is increased after the mold filled with the powder is placed in the heating furnace, the temperature increase rate may be 0.01 to 20°C / min, 0.05 to 10°C / min, or 0.1 to 3.0°C / min.

[0034] The temperature during firing may be increased at a constant rate until the firing temperature is reached, or may be increased at a rate that is changed stepwise until the firing temperature is reached. When the temperature increase rate is changed stepwise, it is preferable to increase the temperature at a predetermined rate until the temperature reaches a temperature range close to the firing temperature, for example, a temperature range that is about 1°C to 20°C lower than the firing temperature, and then to set the rate of increase in temperature when further increasing the temperature to the firing temperature to a rate slower than the previous rate of increase in temperature.

[0035] After firing, the temperature inside the furnace may be decreased at a predetermined rate to cool the mold filled with the powder. In this case, the temperature decreasing rate is not particularly limited, but may be 0.01 to 20° C. / min, 0.05 to 10° C. / min, or 0.1 to 3.0° C. / min.

[0036] The firing of the molded body is not limited to a method in which a mold filled with powder is placed in a heating furnace and then the temperature in the heating furnace is increased at a predetermined heating rate. For example, the firing of the molded body may be performed by placing the mold filled with powder in a heating furnace set at the firing temperature and holding it there for a predetermined period of time.

[0037] The molded article of this embodiment described above can be used, for example, by molding into a block or pipe shape, or by molding into a sheet shape by skiving. The molded article of this embodiment is suitably used as heat-resistant materials such as valve seats, gaskets, packings, heat-resistant insulating tapes, substrates for printed circuit boards, printed circuit boards, and release sheets. EXAMPLES

[0038] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way. In the following examples and comparative examples, "Heated modified PTFE resin" is a modified PTFE resin that has been heat-treated once. "Unheated modified PTFE resin" is modified PTFE resin that has never been heat treated. "Heated homo-PTFE resin" is homo-PTFE resin that has been heat-treated once. "Unheated homo-PTFE resin" refers to homo-PTFE resin that has never been heat-treated.

[0039] Production Example 1 (Heated homogeneous PTFE resin powder A) The number average molecular weight calculated using the Suwa formula below is 1.0 x 10 7 The homo-PTFE resin powder was sintered to obtain a homo-PTFE resin molded body (100 mm x 100 mm x 100 mm), which was then turned on a lathe to produce a special shape. The resulting cutting chips (heated homo-PTFE resin) were then pulverized into resin powder in the following manner. First, the cutting chips (heated homo-PTFE resin) were cut with scissors into pieces with a major axis of 3 mm to 5 mm, and then coarsely crushed into powder with a particle diameter of 1 mm or less in a juice mixer. The obtained coarse powder was then cooled to -196°C with liquid nitrogen and freeze-pulverized using a hammer mill cooled with liquid nitrogen. The freeze-pulverized powder was then classified using a sieve to obtain heated homo-PTFE resin powder A. The sieve had openings of 425 μm, 300 μm, and 250 μm, and the powder was sieved in this order. Median diameter D of powder A 50 was 311 μm.

[0040] Mn = 2.1 × 10 10 ΔHc ―5.16 Suwa's Ceremony (In the formula, Mn is the number average molecular weight, and ΔHc is the heat of crystallization (cal / g) measured by differential scanning calorimetry (DSC).)

[0041] Production Example 2 (Heated Modified PTFE Resin Powder B) The number average molecular weight calculated using the Suwa formula is 7.0×10 6 The unheated modified PTFE resin powder was sintered to obtain a modified PTFE resin molded body (100 mm x 100 mm x 100 mm). The molded body was turned into a desired shape by lathe machining. The resulting cutting chips (heated modified PTFE resin) were pulverized into resin powder by the following procedure. First, the cutting chips (heated modified PTFE resin) were cut with scissors into pieces with a long diameter of 3 mm to 5 mm, and then coarsely ground into powder with a particle diameter of 1 mm or less in a juice mixer. The resulting coarse powder was then cooled to -196°C with liquid nitrogen and freeze-ground using a hammer mill cooled with liquid nitrogen. Next, the freeze-ground powder was ground in a stone mill to obtain a heated modified PTFE resin powder B. Median diameter D of powder B 50 was 183 μm.

[0042] <Median diameter D 50 Measurement> Median diameter D of the powder obtained in the manufacturing example 50 The measurement method is as follows. Randomly select 100 particles from each of powder A and powder B, measure the major and minor diameters of each particle using a microscope, and determine the arithmetic mean of the major and minor diameters for each particle as the particle diameter. The median of the particle diameters of the 100 particles is the median diameter D. 50 It was decided.

[0043] <Dynamic Viscoelasticity (DMA) Measurement> Heated homo-PTFE resin powder A, heated modified PTFE resin powder B, unheated powder (number average molecular weight 1.0×10 7 ) and unheated powder (number average molecular weight 7.0×10 6 ) were each pressure-molded at a molding surface pressure of 35 MPa to obtain cylindrical samples for measuring the storage modulus of elasticity, each having a diameter of 15 mm and a height of 2 mm. The storage modulus G' of each sample was measured using the following equipment and conditions. Measurement device: RSA-G2 (manufactured by TA Instruments Japan Co., Ltd.) Measurement conditions: Temperature 60℃~330℃, distortion 0.3%, frequency: 1Hz Measurement mode: Compression mode

[0044] The measurement results are shown in Figure 2. Unheated modified PTFE resin powder (number average molecular weight 7.0 × 10 6 ), unheated homogeneous PTFE resin powder (number average molecular weight is 1.0×10 7 ), and heated homo-PTFE resin powder A, no significant change in storage modulus was observed in the temperature range of 60°C to 330°C. In contrast, heat-modified PTFE resin powder B was observed to exhibit a significant decrease in storage modulus at around 300°C.

[0045] Example 1 The heated homo-PTFE resin powder A (32.1 g, 95% by mass) produced in Production Example 1 and the heated modified PTFE resin powder B (1.7 g, 5% by mass) produced in Production Example 2 were mixed to obtain a mixed powder (fluororesin powder). The mixed powder was filled into a cylindrical mold with an inner diameter of 20 mm and compression molded from above at a pressure of 35 MPa for 1 minute (molding process (see Fig. 1(a))). Next, the upper and lower surfaces of the cylindrical mold were sandwiched between metal flanges and fixed with bolts and nuts, after which the upper bolt was loosened and a 1 mm spacer was inserted, and in this state the bolt was tightened and the spacer was removed. Next, the cylindrical mold was placed in an electric furnace, and the mixed powder was fired (see Figure 1(b)) by changing the temperature inside the electric furnace in the following order (firing process), to obtain a cylindrical compact with a diameter of 20 mm and a height of 50 mm (see Figure 1(c)). (Temperature adjustment) First stage: Heat from 30°C to 300°C at a rate of 1°C / min. Second stage: The temperature is increased from 300°C to 365°C at a rate of 0.33°C / min. Third step: Hold at 365°C for 4.5 hours. Fourth step: The temperature is decreased from 365°C to 300°C at a rate of 0.33°C / min. Fifth step: The temperature is decreased from 300°C to 30°C at a rate of 1°C / min.

[0046] Examples 2 to 5 A mixed powder was prepared in the same manner as in Example 1, except that the mass ratio of the heated homo-PTFE resin powder A and the heated modified PTFE resin powder B in the mixed powder was changed as shown in Table 1, and a molded body was obtained.

[0047] Comparative Example 1 A molded body was obtained in the same manner as in Example 1, except that 20 g of the heated homo-PTFE resin powder A was used instead of the mixed powder.

[0048] <Tensile test> The molded bodies obtained in the examples and comparative examples were cut with a band saw to obtain rectangular test pieces (length 50 mm, width 15 mm, thickness 1.35 mm to 2.2 mm). The obtained test piece was punched into a No. 7 dumbbell shape using a clicker press to obtain a sample for tensile testing. After measuring the thickness and specific gravity of the obtained tensile test sample, a tensile test was performed using a benchtop universal testing machine (manufactured by Shimadzu Corporation) at a tensile speed of 200 mm / min and a chuck distance of 20 mm. The strength at which the sample broke (the value obtained by dividing the tensile load value by the cross-sectional area of ​​the test piece) and the sample length were measured, and the tensile strength (MPa) and tensile elongation (%) were calculated. The tensile elongation was calculated using the following formula (A). The results are shown in Table 3. Tensile elongation (%) = (LL o ) / L o ×100 …(A) L o : Sample length before test L: Sample length at break

[0049] <Specific gravity> Using the underwater displacement method, the specific gravity was calculated from the masses of the same sample measured in air and in water according to the following formula.

number

[0050] The tensile strength, tensile elongation and specific gravity of the molded bodies obtained in Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

[0051] [Table 1]

[0052] It can be seen from Table 1 that the tensile strength and tensile elongation of the heated homo-PTFE resin powder can be significantly improved by adding the heated modified PTFE resin powder. Fig. 3 is a stress-strain curve measured by a tensile test. Note that a strain of 1 on the horizontal axis is equivalent to a tensile elongation of 100%. Also, as a reference example, the results of a molded body produced in the same manner as in Example 1 except that only heated modified PTFE resin powder B was used instead of the mixed powder are shown. From Fig. 3, it can be seen that the molded body obtained from the mixture of heated homo-PTFE resin powder and heated modified PTFE resin powder has higher rigidity than the molded body obtained from heated homo-PTFE resin powder alone (Comparative Example 1), and also has a higher stress in the low strain region. [Industrial Applicability]

[0053] Molded articles formed using the fluororesin powder of the present invention are suitably used as heat-resistant materials such as valve seats, gaskets, packings, heat-resistant insulating tapes, substrates for printed circuit boards, printed circuit boards, and release sheets.

Claims

1. A polytetrafluoroethylene resin (A) having a melting point of 333° C. or lower; A fluororesin powder comprising: (B) a modified polytetrafluoroethylene resin having a melting point of 333°C or lower.

2. The storage modulus G′ of the modified polytetrafluoroethylene resin (B) at a temperature of about 300° C. when measured under conditions of a frequency of 1 Hz and a strain of 0.3% is 1.0×10 ５ The fluororesin powder according to claim 1, wherein the viscosity is 0.01 Pa or less.

3. The polytetrafluoroethylene resin (A) has a median diameter D ５０ The fluororesin powder according to claim 1 or 2, wherein the particle size is 20 μm to 500 μm.

4. The modified polytetrafluoroethylene resin (B) has a median diameter D ５０ The fluororesin powder according to any one of claims 1 to 3, wherein the particle size is 20 µm to 500 µm.

5. The content of the modified polytetrafluoroethylene resin (B) is 5 mass% or more based on the total of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B), The fluororesin powder according to any one of claims 1 to 4.

6. The content of the modified polytetrafluoroethylene resin (B) is 20 mass% or more based on the total of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B), The fluororesin powder according to any one of claims 1 to 4.

7. A molded article obtained by molding the fluororesin powder according to any one of claims 1 to 6.

8. The molded article according to claim 7, having a tensile strength of 15 MPa or more.

9. The molded article according to claim 7 or 8, which has a tensile elongation of 100% or more.

10. The molded article according to any one of claims 7 to 9, having a specific gravity of 1.81 or more.

11. A step of pulverizing the molded body of polytetrafluoroethylene resin and the molded body of modified polytetrafluoroethylene resin; mixing the polytetrafluoroethylene resin powder obtained in the above step with the modified polytetrafluoroethylene resin powder.

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