Fluororesin powder and molded articles 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] This invention relates to fluororesin powder and molded articles thereof. More specifically, it relates to powder and molded articles using fluororesin that has a history of being heated to a temperature above its melting point, such as recycled products. [Background technology]

[0002] Fluororesins 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 components, semiconductors, and automobiles. However, there is a problem in that when fluororesins such as polytetrafluoroethylene (PTFE) that have been heat-treated (fired) are used again as raw material powder, the mechanical strength of the resulting molded product decreases significantly. Various studies have been conducted on methods for utilizing heat-treated (fired) fluororesins, such as those described in Patent Documents 1 to 10. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4714310 [Patent Document 2] Japanese Patent Publication No. 2015-108126 [Patent Document 3] Patent No. 6612001 [Patent Document 4] Japanese Patent Publication No. 2003-245983 [Patent Document 5] Special Publication No. 4-23658 [Patent Document 6] Japanese Patent Publication No. 2022-159201 [Patent Document 7] Japanese Patent Publication No. 2022-159202 [Patent Document 8] Japanese Patent Publication No. 2022-159203 [Patent Document 9] Japanese Patent Publication No. 2022-159204 [Patent Document 10] Japanese Patent Publication No. 2022-159205 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Currently, the technologies being considered primarily involve mixing unheated fluororesin with heated fluororesin, which has not necessarily yielded sufficient results in reducing environmental impact or raw material costs. Furthermore, molded articles made from recycled PTFE that has undergone a heating process have a significant drawback: a substantial decrease in mechanical properties such as tensile strength and tensile elongation.

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

[0006] According to the present invention, the following fluororesin powders 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 near 300°C, measured under conditions of a frequency of 1 Hz and a strain of 0.3%, is 1.0 × 10⁻⁶. 5 The fluororesin powder described in 1, having a Pa of less than or equal to Pa. 3. The polytetrafluoroethylene resin (A) has a median diameter D 50 The fluororesin powder according to 1 or 2, wherein the powder is 20 μm to 500 μm in size. 4. The modified polytetrafluoroethylene resin (B) has a median diameter D 50 A fluororesin powder according to any one of 1 to 3, wherein the powder is 20 μm to 500 μm in size. 5. The fluororesin powder according to any one of 1 to 4, wherein the content of the modified polytetrafluoroethylene resin (B) is 5% by mass or more based on the total 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% by mass or more based on the total of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B). 7. A molded body obtained by molding the fluororesin powder according to any one of 1 to 6. 8. The molded body according to 7, having a tensile strength of 15 MPa or more. 9. The molded body according to 7 or 8, having a tensile elongation rate of 100% or more. 10. The molded body according to any one of 7 to 9, having a specific gravity of 1.81 or more. 11. A step of pulverizing a molded body of a polytetrafluoroethylene resin and a molded body of a modified polytetrafluoroethylene resin, and A step of mixing the powder of the polytetrafluoroethylene resin obtained in the above step and the powder of the modified polytetrafluoroethylene resin, a method for producing a fluororesin powder.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a fluororesin powder capable of improving the mechanical properties of a molded body using only PTFE that has undergone a heating process without using an unheated fluororesin.

Brief Description of the Drawings

[0008] [Figure 1] It is a diagram for explaining a method for producing a molded body of the present invention. [Figure 2] It is a diagram showing the measurement results of the storage elastic modulus G' of each PTFE. [Figure 3] It is a stress-strain curve measured by a tensile test of molded bodies prepared in Examples and Comparative Examples.

Embodiments for Carrying Out the Invention

[0009] The following describes the fluororesin powder and molded article according to the present invention. In this specification, "x~y" represents a numerical range of "greater than or equal to x and less than or equal to y". If there are multiple lower limits such as "greater than or equal to x" or multiple upper limits such as "less than or equal to y" for a single technical matter, these upper and lower limits may be arbitrarily selected and combined.

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

[0011] Polytetrafluoroethylene resin (homo-PTFE) (A) can be used without particular restrictions as long as its melting point is 333°C or lower. For example, recycled products recovered from commercially available homo-PTFE molded articles can be used. Modified polytetrafluoroethylene resin (modified PTFE) (B) can also be used without particular restrictions as long as its melting point is 333°C or lower, and examples include recycled products recovered from molded modified PTFE that are commercially available industrially.

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

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

[0014] Examples of perfluoroalkyl groups having 1 to 10 carbon atoms in formula (1) include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl groups. Perfluoropropyl is preferred.

[0015] The proportion of perfluoroalkyl vinyl ether polymerization units represented by the above formula (1) is preferably 1% by weight or less, and preferably in the range of 0.001% by mass to 1% by mass. This facilitates fusion between powder particles during firing, resulting in a molded article with excellent strength after heating.

[0016] In one embodiment, the storage modulus G' of modified PTFE(B) at a temperature near 300°C, measured under conditions of a frequency of 1 Hz and a strain of 0.3%, is 1.0 × 10⁻⁶. 5 It is below Pa. The storage elastic modulus G’ near 300°C being 1.0×10 5 Pa or less means that the modified PTFE has been heated to a temperature above its melting point in the past. The modified PTFE showing the above heat behavior can be obtained, for example, by adjusting the heating rate (e.g., 0.01 - 20 °C / min), the maximum temperature reached (e.g., a temperature above the melting point (327 °C). For example, 327 °C - 400 °C.), the holding time thereof (1 minute - 4.5 hours), the pressure of the pressure treatment before the heat treatment (e.g., 10 MPa - 100 MPa), etc. when heat-treating the unheated resin.

[0017] In one embodiment, the homopolymer PTFE (A) is a powder with a median diameter D 50 of 20 μm - 500 μm. Thereby, a dense molded body is likely to be obtained. The median diameter D 50 of the homopolymer PTFE (A) is 50 μm or more, 100 μm or more, 150 μm or more, or 180 μm or more. Also, the median diameter D 50 of the homopolymer PTFE (A) is 450 μm or less, 400 μm or less, or 350 μm or less.

[0018] In one embodiment, the modified PTFE (B) is a powder with a median diameter D 50 of 20 μm - 500 μm. Thereby, a dense molded body is likely to be obtained. The median diameter D 50 of the modified PTFE (B) is 50 μm or more, 100 μm or more, 150 μm or more, or 180 μm or more. Also, the median diameter D 50 of the homopolymer PTFE (A) is 450 μm or less, 400 μm or less, or 350 μm or less. Note that the median diameter D 50 of the powder is measured by the method described in the examples.

[0019] The fluororesin powder of the resin according to this embodiment can be obtained, for example, by a manufacturing method that includes the steps of: grinding 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 grinding step with the polytetrafluoroethylene resin powder (modified PTFE(B) powder).

[0020] In the grinding process, the grinding method is not particularly limited as long as it can grind the molded body to a desired particle size. For example, a mixer, hammer mill, jet mill, stone mill grinder, or freeze grinder can be used. Grinding may be performed in one go using one type of equipment, or it may be performed in stages using multiple types of equipment. For example, homo-PTFE and modified PTFE, which are molded pieces in the form of individual flakes, may be ground to a desired particle size using a mixer, or the homo-PTFE and modified PTFE in the form of individual flakes may be ground to a predetermined particle size using a mixer and then ground to a desired particle size using a hammer mill.

[0021] Furthermore, cryopreservation may be employed, in which molded articles of homo-PTFE and modified PTFE are cooled to a frozen state and then pulverized. In cryopreservation, it is preferable to cool to a temperature below the glass transition temperature of the resin. For example, it is preferable to cool to -190°C or below, -196°C or below, and even to -250°C or below. Furthermore, the molded bodies of homo-PTFE and modified PTFE may be mixed beforehand and pulverized simultaneously, or they may be pulverized separately.

[0022] By mixing the homo-PTFE(A) powder obtained in the above grinding process with the modified PTFE(B) powder, a fluororesin powder of the resin according to this embodiment can be obtained. The mixing method is not particularly limited, and known devices such as a stirrer can be used. In one embodiment, the content of modified PTFE(B) is 5% by mass or more relative to the total of homo-PTFE(A) and modified PTFE(B). This significantly enhances the effect of incorporating modified PTFE(B), improving the tensile elongation of the resulting molded article. Furthermore, if the modified PTFE(B) content is 20% by mass or more, the rigidity of the resulting molded article will be higher. The content of 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 fluororesin powder of the present invention described above. The molded article of this embodiment may contain optional components in addition to 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 additives, pigments, antioxidants, reflective agents, opacities, lubricants, processing stabilizers, plasticizers, foaming agents, and fillers. The total content of optional components in the molded article is usually 50% by mass or less. In one embodiment, the molded body does not contain any fluororesin other than the fluororesin powder of the present invention described above.

[0024] In one embodiment, the tensile strength of the molded article may be 15 MPa or more, 18 MPa or more, or 20 MPa or more. There is no particular upper limit to the tensile strength of a molded article, but it 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 article may be 100% or more, 150% or more, or 200% or more. There is no particular upper limit to the tensile strength of a molded article, but it 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 the range where the tensile elongation is 0% to 50%. The rigidity of the molded article in this embodiment is improved by mixing homo PTFE (A) and modified PTFE (B).

[0027] In one embodiment, the specific gravity of the molded article is 1.81 or higher. Because the molded article of this embodiment has high density, it possesses excellent mechanical properties. The specific gravity may be 2.00 or higher, 2.10 or higher, or 2.17 or higher. Typically, it is 2.19 or lower. The specific gravity of the molded article is measured by the method described in the examples.

[0028] The molded article according to this embodiment can be obtained, for example, by a manufacturing method including the following steps (1) and (2). (1) The process of filling a mold with the fluororesin powder of the present invention described above and applying pressure. (2) A process of heating a mold filled with powder to sinter the powder filled in the mold.

[0029] (Process (1) Pressurizing the powder) Figure 1 is a diagram illustrating the method for manufacturing a molded article according to the present invention. The fluororesin powder 10 of the present invention described above is filled into a mold and pressurized. The pressurized powder is compressed and molded within the mold (see Figure 1(a)).

[0030] Median diameter D of modified PTFE resin powder according to one embodiment of the present invention, to be filled into a mold 50 The particle size is preferably 20 μm to 500 μm. This allows the PTFE powder to easily fuse when the molded body of the powder is heated and fired in step (2) described later, resulting in a dense molded body with excellent strength after heating. The smaller the particle size of the powder, the higher the strength of the molded body obtained after reheating tends to be.

[0031] The pressurized pressure may be 5 MPa to 100 MPa, 20 MPa to 60 MPa, or 30 MPa to 50 MPa. By pressurizing the molded body obtained in this process within the above pressure range, when it is heated and fired in step (2) described later, weldability is easily achieved between the PTFE powder particles, and excellent strength can be obtained in the molded body obtained after heating.

[0032] (Process (2) Firing of the molded body) The mold filled with powder is heated to sinter the powder inside the mold (see Figures 1(b) and 1(c)). The firing temperature may be 300°C to 400°C, 330°C to 370°C, or 360°C to 370°C. By firing within the above temperature range, the fluidity of the PTFE constituting the molded body 11 is moderately increased, facilitating the fusion of the PTFE powder particles 10, and resulting in a molded body with excellent strength obtained after this process.

[0033] The firing of the molded body can be performed, for example, by placing a mold filled with powder into a heating furnace, raising the temperature inside the furnace at a predetermined rate, and holding it at the firing temperature for a predetermined time. When the temperature inside a furnace is raised after a mold filled with powder has been placed into the furnace, the rate of heating may be 0.01 to 20°C / min, 0.05 to 10°C / min, or 0.1 to 3.0°C / min.

[0034] During firing, the heating rate may be kept constant until the firing temperature is reached, or the heating rate may be changed in stages until the firing temperature is reached. When the heating rate is changed in steps, it is preferable to heat the material at a predetermined rate until it reaches a temperature range close to the firing temperature, for example, a temperature range about 1°C to 20°C lower than the firing temperature, and then to further heat it until it reaches the firing temperature, using a lower heating rate than the previous heating rates.

[0035] After firing, the mold filled with powder may be cooled by lowering the temperature inside the furnace at a predetermined rate. The rate of cooling in this case 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] Furthermore, 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 the temperature inside the heating furnace is raised at a predetermined rate. For example, it may also be performed by placing a mold filled with powder into a heating furnace set to the firing temperature and holding it there for a predetermined time.

[0037] The molded articles of this embodiment described above can be used, for example, by forming them into block shapes or pipe shapes, or by forming them into sheet shapes by skiving. The molded body according to this embodiment is suitably used as a valve seat, gasket, packing, heat-resistant material such as heat-resistant insulating tape, substrate for printed circuit boards, printed circuit boards, and release sheet. [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 in any way by these examples. In the following examples and comparative examples, "Heated modified PTFE resin" is modified PTFE resin that has been heat-treated once. "Unheated modified PTFE resin" refers to 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] Manufacturing Example 1 (Heated Homo PTFE Resin Powder A) The number-average molecular weight calculated using Suwa's formula shown below is 1.0 × 10⁻⁶. 7 The cutting chips (heated homo-PTFE resin) generated when a molded body (100mm x 100mm x 100mm) of homo-PTFE resin, obtained by firing unheated homo-PTFE resin powder, were shaped using a lathe were crushed into resin powder using the following procedure. First, the cutting shavings (heated homo-PTFE resin) were cut with scissors to obtain pieces with a major diameter of 3 mm to 5 mm. These pieces were then coarsely ground into a powder with a particle size of 1 mm or less using 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 classified using a sieve to obtain heated homo-PTFE resin powder A. The sieve openings were 425 μm, 300 μm, and 250 μm, and the powder was sieved in this order. Median diameter D of powder A 50 It was 311 μm.

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

[0041] Manufacturing Example 2 (Heated Modified PTFE Resin Powder B) The number-average molecular weight calculated using Suwa's formula is 7.0 × 10 6 The modified PTFE resin molded body (100mm x 100mm x 100mm) obtained by firing unheated modified PTFE resin powder was then shaped using a lathe, and the resulting cutting chips (heated modified PTFE resin) were crushed into resin powder using the following procedure. First, the cutting shavings (heat-treated modified PTFE resin) were cut with scissors into pieces with a major diameter of 3 mm to 5 mm. These pieces were then coarsely ground into a powder with a particle size of 1 mm or less using 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-dried powder was ground using a millstone grinder to obtain heated modified PTFE resin powder B. Median diameter D of powder B 50 It 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: 100 particles are randomly selected from powder A and powder B, and the major and minor diameters of each particle are measured using a microscope. The particle diameter is determined by the arithmetic mean of the major and minor diameters for each particle, and the median diameter D is the median of the 100 particle diameters. 50 That's what I decided.

[0043] <Dynamic Viscoelasticity (DMA) Measurement> Heated homo-PTFE resin powder A, heated modified PTFE resin powder B, unheated powder (number average molecular weight of 1.0 × 10) 7 ) and unheated powder (number average molecular weight is 7.0 × 10 6 Each of these was pressure-molded at a molding surface pressure of 35 MPa to obtain cylindrical samples with a diameter of 15 mm and a height of 2 mm for measuring the storage modulus. The storage modulus G' of each sample was measured under the following equipment and conditions. Measuring device: RSA-G2 (manufactured by T.A. Instrument 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 is 7.0 × 10⁶) 6 ), unheated homo PTFE resin powder (number average molecular weight is 1.0 × 10 7 In both the original PTFE resin powder A and the 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, in the heated homo-PTFE resin powder B, a significant decrease in storage modulus was observed around 300°C.

[0045] Example 1 A mixed powder (fluororesin powder) was obtained by mixing heated homo-PTFE resin powder A (32.1 g, 95% by mass) prepared in Production Example 1 with heated modified PTFE resin powder B (1.7 g, 5% by mass) prepared in Production Example 2. The mixed powder was filled into a cylindrical mold with an inner diameter of 20 mm and compressed from above at a press pressure of 35 MPa for 1 minute (see molding process (Figure 1(a))). Next, the top and bottom surfaces of the cylindrical mold were sandwiched between metal flanges and secured with bolts and nuts. Then, the bolts on the top surface were loosened, a 1 mm spacer was inserted, and the bolts were tightened to remove the spacer. Next, the cylindrical mold was placed in an electric furnace, and the furnace temperature was changed in the following order to calcine the mixed powder (see Figure 1(b)) (calcination process), obtaining a cylindrical molded body 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 heating rate of 1°C / min. Second stage: The temperature is increased from 300°C to 365°C at a heating rate of 0.33°C / min. Third stage: Maintain at 365°C for 4.5 hours. Stage four: Cool the temperature from 365°C to 300°C at a rate of 0.33°C / min. Fifth stage: Cool the temperature from 300°C to 30°C at a rate of 1°C / min.

[0046] Examples 2-5 A mixed powder was prepared in the same manner as in Example 1, except that the mass ratio of heated homo-PTFE resin powder A and 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 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 strip-shaped test pieces (length 50 mm, width 15 mm, thickness 1.35 mm to 2.2 mm). The obtained test specimens were punched out into a No. 7 dumbbell shape using a clicker press to obtain samples for tensile testing. After measuring the thickness and specific gravity of the obtained tensile test specimens, tensile tests were performed using a benchtop universal testing machine (manufactured by Shimadzu Corporation) under conditions of a tensile speed of 200 mm / min and a chuck distance of 20 mm. The strength at which the specimen fractured (the tensile load value divided by the cross-sectional area of ​​the specimen) and the specimen 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 testing L: Sample length at fracture

[0049] <Specific gravity> Using the water displacement method, the specific gravity was determined from the mass measured in air and the mass measured in water of the same sample using the following formula.

number

[0050] Table 1 shows the tensile strength, tensile elongation, and specific gravity of the molded articles obtained in Examples 1-5 and Comparative Example 1.

[0051] [Table 1]

[0052] Table 1 shows that adding heated modified PTFE resin powder can significantly improve the tensile strength and tensile elongation of heated homo-PTFE resin powder. Figure 3 shows the stress-strain curve measured by a tensile test. Note that a strain of 1 on the horizontal axis corresponds to a tensile elongation of 100%. As a reference example, the results for a molded article prepared in the same manner as in Example 1, except that only pre-heated modified PTFE resin powder B was used instead of the mixed powder, are also shown. From Figure 3, it can be seen that the molded article obtained from a mixture of pre-heated homo-PTFE resin powder and pre-heated modified PTFE resin powder has higher rigidity and higher stress in the low-strain region than the molded article obtained from pre-heated homo-PTFE resin powder alone (Comparative Example 1). [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, and heat-resistant insulating tapes, as well as substrates for printed circuit boards, printed circuit boards, and release sheets.

Claims

1. A polytetrafluoroethylene resin (A) has a melting point of 333°C or lower, It comprises a modified polytetrafluoroethylene resin (B) having a melting point of 333°C or lower, The storage modulus G' of the modified polytetrafluoroethylene resin (B) measured under conditions of a frequency of 1 Hz and a strain of 0.3% at a temperature of approximately 300°C was 1.0 × 10⁻⁶. ５ Fluororesin powder with a pH of Pa or less.

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

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

4. The fluororesin powder according to claim 1 or 2, wherein the content of the modified polytetrafluoroethylene resin (B) is 5% by mass or more relative to the total of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B).

5. The fluororesin powder according to claim 1 or 2, wherein the content of the modified polytetrafluoroethylene resin (B) is 20% by mass or more relative to the total of the polytetrafluoroethylene resin (A) and the modified polytetrafluoroethylene resin (B).

6. A molded article obtained by molding the fluororesin powder described in claim 1.

7. The molded article according to claim 6, wherein the tensile strength is 15 MPa or more.

8. The molded article according to claim 6 or 7, wherein the tensile elongation rate is 100% or more.

9. The molded article according to claim 6 or 7, wherein the specific gravity is 1.81 or higher.

10. A process of crushing a molded body of polytetrafluoroethylene resin and a molded body of modified polytetrafluoroethylene resin, A method for producing a fluororesin powder according to claim 1 or 2, comprising the step of mixing the polytetrafluoroethylene resin powder obtained in the above step with the modified polytetrafluoroethylene resin powder.

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