JP2014028953A - Modified fluorine resin mixture, fluorine resin molded article, and method for manufacturing fluorine resin molded article - Google Patents

Abstract

A modified fluororesin mixture having excellent crack resistance, a fluororesin molded product, and a method for producing a fluororesin molded product are provided.
Irradiation is made of two or more kinds of fluororesins having different melting points, and the irradiation is not less than the melting point of the fluororesin having the highest melting point and not less than the glass transition temperature of the fluororesin having the highest glass transition temperature. A modified fluororesin mixture obtained by irradiating the fluororesin mixture with radiation at a temperature.
[Selection figure] None

Description

The present invention relates to a modified fluororesin mixture, a fluororesin molded product, and a method for producing a fluororesin molded product.

Fluorine-containing copolymers are excellent in heat resistance, chemical resistance, weather resistance, contamination resistance, and the like, and are used in various fields such as semiconductors, automobiles, architecture, electrical / electronics, chemical plants, and pharmaceuticals.
Various methods for further improving various properties such as heat resistance, mechanical properties and radiation resistance of such a fluorinated copolymer have been studied.

As one method for modifying a fluorinated copolymer, it is known to irradiate with radiation. As such a modification method, a method is generally known in which a fluorine-containing copolymer is heated to a melting point or higher and irradiated with radiation (Patent Document 1).
However, after molding the fluorinated copolymer, if the resulting molded product is heated to a temperature higher than the melting point of the fluorinated copolymer and irradiated with radiation, the shape of the molded product may change. It was. In addition, there has been a problem that the deterioration of the fluororesin due to the irradiation of radiation becomes large and the desired mechanical properties cannot be obtained sufficiently.

Patent Document 2 discloses that ionizing radiation with a high dose rate of 100 kGy / sec or more is irradiated from a particle accelerator within a range of irradiation doses of 200 kGy to 100 MGy without irradiation in advance. A method for producing a modified fluororesin by crosslinking the resin and improving heat resistance and chemical resistance in a simple and short time is disclosed.

In Patent Document 3, a fluororesin heated from 0 to 150 ° C. or from 0 ° C. to a crystal dispersion temperature is irradiated with ionizing radiation at an irradiation amount of 5 Gy to 500 kGy, and the irradiated fluororesin is heated to a predetermined temperature. It is disclosed that the heat resistance deterioration characteristic and the compression strain resistance are improved by holding for a predetermined time.

In Patent Document 4, after forming a fluororesin layer on a substrate, the fluororesin layer is heated to a temperature in a range up to 150 ° C. higher than the melting point of the fluororesin and fired. By setting the temperature of the fluororesin layer to a temperature in a range from a temperature 60 ° C. lower than the melting point (Tm) of the fluororesin to a temperature lower than the melting point by 1 ° C., crosslinking is performed by irradiation with radiation. A method for producing a composite material having a cross-linked fluororesin layer having excellent adhesion to a substrate is disclosed.

In Patent Document 5, a base material having thermal stability at a temperature equal to or higher than the melting point of the fluororesin is a modified fluororesin coating material coated with a cross-linked fluororesin film, and the cross-linking of the fluororesin is 250 to 250. It is disclosed to be performed with ionizing radiation at a temperature in the range of 400 ° C.

JP 2002-338766 A Japanese Patent Laid-Open No. 11-349711 JP 2002-327068 A JP 2010-155443 A JP 2011-105012 A

However, the fluororesins obtained by these conventional reforming methods still have insufficient crack resistance. In addition, when modifying a mixture of two or more kinds of fluororesins by irradiating with ionizing radiation, the irradiation temperature condition and the like have not been sufficiently studied.

In order to obtain a small molded product or a complex molded product with a fluorine-containing copolymer, a material having excellent moldability and good fluidity is required. However, a fluorine-containing copolymer having excellent fluidity has a relatively low molecular weight, and therefore has poor crack resistance. For this reason, when obtaining a molded body as described above, it is common to obtain a desired molded body by performing compression molding and subsequent secondary processing without performing extrusion molding or injection molding using a material having a high molecular weight. It was the target. Such a conventional method has a problem in that the productivity is low and the cost of the final product is high.

An object of this invention is to provide the modified fluororesin mixture excellent in crack resistance, a fluororesin molded product, and the manufacturing method of a fluororesin molded product in view of the said present condition.

As a result of studying such a requirement, the inventors of the present invention have modified fluorine having excellent crack resistance by irradiating a mixture of two or more fluororesins having different melting points at a specific range of irradiation temperature. It discovered that it could be set as a resin mixture, and completed this invention.

That is, the present invention comprises two or more types of fluororesins having different melting points, and among the above fluororesins, the melting point of the fluororesin having the highest melting point and the glass transition temperature of the fluororesin having the highest glass transition temperature. A modified fluororesin mixture obtained by irradiating the fluororesin mixture with radiation at an irradiation temperature of

The present invention is also a fluororesin molded article comprising the modified fluororesin mixture.

The present invention also includes a step of molding a mixture of two or more kinds of fluororesins having different melting points, and a fluororesin having a glass transition temperature which is not higher than the melting point of the fluororesin having the highest melting point and has the highest glass transition temperature. It is also a fluororesin molded product obtained by a method for producing a molded product having a step of irradiating the molded mixture of fluororesin with radiation at an irradiation temperature equal to or higher than the glass transition temperature.

The fluororesin preferably has a melt flow rate at 372 ° C. of 0.5 to 100 g / 10 min.

The fluororesin includes a fluorine-containing copolymer (A) containing only tetrafluoroethylene units and perfluoro (alkyl vinyl ether) units, and a fluorine-containing copolymer (B) containing tetrafluoroethylene units and hexafluoropropylene units. It is preferable that

The mass ratio ((A) / (B)) of the fluorine-containing copolymer (A) to the fluorine-containing copolymer (B) is preferably 1/9 to 7/3.

The present invention further includes a step of molding a mixture of two or more kinds of fluororesins having different melting points, and a fluororesin having a highest glass transition temperature below the melting point of the fluororesin having the highest melting point among the fluororesins. It is also a method for producing a fluororesin molded product, comprising a step of irradiating the molded mixture of the fluororesin with radiation at an irradiation temperature equal to or higher than the glass transition temperature.

In the production method of the present invention, the irradiation temperature is preferably 150 to 300 ° C., and the radiation dose is preferably 10 kGy to 250 kGy.

According to the present invention, it is possible to obtain a modified fluororesin mixture and a fluororesin molded product having excellent crack resistance.

The present invention is described in detail below.

The present invention comprises two or more types of fluororesins having different melting points. Among the fluororesins, the irradiation is equal to or lower than the melting point of the fluororesin having the highest melting point and above the glass transition temperature of the fluororesin having the highest glass transition temperature. A modified fluororesin mixture obtained by irradiating the fluororesin mixture with radiation at a temperature. For this reason, the modified fluororesin mixture of the present invention is excellent in crack resistance.

In a mixture of two or more types of fluororesins with different melting points, irradiation with radiation at a temperature below the melting point of the fluororesin with the highest melting point makes the fluororesin with a low melting point easy to move and the crosslinking reaction is efficient. Presumed to progress. Further, the crosslinking proceeds in a state where the fluororesin having the highest melting point is not melted, which is effective for maintaining the shape of the fluororesin molded product.

The modified fluororesin mixture of the present invention comprises two or more fluororesins having different melting points.
Examples of the fluororesin include polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene- Examples include hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVdF), polychlorotrifluoroethylene (PCTFE), and the like.
The two or more types of fluororesin are preferably fluororesins that can be melt-molded.

Of these, it is effective to mix a perfluoro fluororesin excellent in chemical resistance, heat resistance and dielectric properties.

The fluororesin includes a fluorocopolymer (A) containing only tetrafluoroethylene (TFE) units and perfluoro (alkyl vinyl ether) (PAVE) units, tetrafluoroethylene (TFE) units and hexafluoropropylene (HFP) units. The fluorine-containing copolymer (B) containing is preferable. The fluororesin is preferably a mixture of the two specific types of copolymers.

The fluorine-containing copolymer (A) consists only of TFE units and PAVE units.
As PAVE which comprises a fluorine-containing copolymer (A), general formula (1):
^{_{CF 2 = CFO (CF 2 CFY}} 1 O) p - (CF 2 CF 2 CF 2 O) q -R f (1)
(Wherein, ^{Y 1} represents F or CF _3, ^{R f} represents an integer of .p 0-5 representing a perfluoroalkyl group having 1 to 5 carbon atoms, q is an integer of 0-5. ) And general formula (2):
CFX = CXOCF ₂ OR ¹ (2)
Wherein X is the same or different and represents H, F or CF ₃ , and R ¹ represents at least one atom selected from the group consisting of H, Cl, Br and I, which is linear or branched. 1 to 2 fluoroalkyl groups having 1 to 6 carbon atoms, or 1 to 2 atoms selected from the group consisting of H, Cl, Br and I Represents a cyclic fluoroalkyl group having 5 or 6 carbon atoms.)
The at least 1 sort (s) selected from the group which consists of can be mentioned.

Especially, as said PAVE, what has a bulky side chain is preferable and specifically, perfluoro (propyl vinyl ether) (PPVE) is preferable.

The TFE / PAVE copolymer preferably contains 0.1 to 10% by mass of polymer units based on PAVE, more preferably 1.0 to 8.0% by mass, and even more preferably 2% based on the total polymerized units. 0.0 to 6.5% by mass, particularly preferably 3.5 to 6.0% by mass.
The amount of polymerized units based on the PAVE is measured by ¹⁹ F-NMR method.

The fluorinated copolymer (A) preferably has a melting point of 280 to 322 ° C.
The melting point is more preferably 290 ° C. or higher, and more preferably 315 ° C. or lower.
The melting point is a temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 ° C./min using a differential scanning calorimeter [DSC].

The fluorine-containing copolymer (A) preferably has a glass transition temperature (Tg) of 70 to 110 ° C.
The glass transition temperature is more preferably 80 ° C. or higher, and more preferably 100 ° C. or lower.
The glass transition temperature is a value obtained by measurement by dynamic viscoelasticity measurement.

The fluorine-containing copolymer (A) is produced, for example, by a conventionally known method such as emulsion polymerization and suspension polymerization by appropriately mixing monomers as constituent units and additives such as a polymerization initiator. be able to.

The fluorine-containing copolymer (B) contains tetrafluoroethylene (TFE) units and hexafluoropropylene (HFP) units.
The fluorine-containing copolymer (B) preferably has a mass ratio (TFE / HFP) of TFE units to HFP units of 70 to 99/1 to 30 (mass%).
Within the above range, a modified fluororesin mixture having excellent crack resistance can be obtained.
The mass ratio (TFE / HFP) is more preferably 85 to 95/5 to 15 (mass%).

The fluorine-containing copolymer (B) preferably further contains perfluoro (alkyl vinyl ether) (PAVE) units. By further including PAVE units, the crack resistance can be further improved.
Examples of the PAVE unit contained in the fluorinated copolymer (B) include the same PAVE units as those constituting the fluorinated copolymer (A) described above.
Especially, PPVE is more preferable at the point which is excellent in the improvement of crack resistance.

When the fluorine-containing copolymer (B) is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter also referred to as “TFE / HFP / PAVE copolymer”), the mass ratio (TFE / HFP / PAVE) is preferably 70 to 99.8 / 0.1 to 25 / 0.1 to 25 (mass%). Within the above range, the heat resistance and chemical resistance are excellent.
The mass ratio (TFE / HFP / PAVE) is more preferably 75 to 98 / 0.1 to 20 / 0.1 to 20 (mass%).

In the TFE / HFP / PAVE copolymer, the HFP unit is preferably 25% by mass or less based on the total monomer units.
When the content of the HFP unit is in the above range, a fluororesin molded product having excellent heat resistance can be obtained.
The content of the HFP unit is more preferably 20% by mass or less, and further preferably 18% by mass or less. Especially preferably, it is 15 mass% or less. Moreover, 0.1 mass% or more is preferable and, as for content of a HFP unit, 1 mass% or more is more preferable. Especially preferably, it is 2 mass% or more.
The content of HFP units can be measured by ¹⁹ F-NMR method.

The content of the PAVE unit is more preferably 20% by mass or less, and further preferably 10% by mass or less. Especially preferably, it is 3 mass% or less. Moreover, 0.1 mass% or more is preferable and, as for content of a PAVE unit, 1 mass% or more is more preferable. In addition, content of a PAVE unit can be measured by a ¹⁹ F-NMR method.

The fluorine-containing copolymer (B) may further contain other ethylenic monomer (α) units.
Other ethylenic monomers (α) are not particularly limited as long as they are monomer units copolymerizable with TFE units, HFP units, and PAVE units. For example, vinyl fluoride (VF), vinylidene fluoride Examples thereof include fluorine-containing ethylenic monomers such as (VdF), chlorotrifluoroethylene [CTFE], and ethylene (ETFE), and non-fluorinated ethylenic monomers such as ethylene, propylene, and alkyl vinyl ether.

When the fluorine-containing copolymer (B) is a TFE / HFP / PAVE / other ethylenic monomer (α) copolymer, the mass ratio (TFE / HFP / PAVE / other ethylenic monomer (α )) Is preferably 70 to 98 / 0.1 to 25 / 0.1 to 25 / 0.1 to 25 (mass%).

The fluorinated copolymer (B) preferably has a melting point of 200 to 322 ° C. If the melting point is less than 200 ° C., the amount of radicals involved in the crosslinking reaction is insufficient, and the crosslinking effect may not be sufficiently exhibited. When the temperature exceeds 322 ° C., the molecular weight is reduced due to main chain cleavage, and the mechanical strength may be greatly reduced. The melting point is more preferably 220 ° C. or higher, more preferably 300 ° C. or lower, and further preferably 280 ° C. or lower.
The melting point is a temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 ° C./min using a differential scanning calorimeter [DSC].

The fluorine-containing copolymer (B) preferably has a glass transition temperature (Tg) of 60 to 110 ° C.
The glass transition temperature is more preferably 65 ° C. or higher, and more preferably 100 ° C. or lower.
The glass transition temperature is a value obtained by measurement by dynamic viscoelasticity measurement.

The fluorine-containing copolymer (B) is, for example, a conventionally known method such as emulsion polymerization, solution polymerization or suspension polymerization by appropriately mixing monomers as constituent units and additives such as a polymerization initiator. Can be manufactured.

The mass ratio ((A) / (B)) between the fluorinated copolymer (A) and the fluorinated copolymer (B) is preferably from 1/9 to 7/3. When the mixing ratio is within the above range, a modified fluororesin mixture having excellent crack resistance can be obtained.
The mass ratio is more preferably 5/5 to 2/8. Compared with the fluorine-containing copolymer (A), the ratio of the fluorine-containing copolymer (B) generally inferior in crack resistance is high, so that the improvement of the fluorine-containing copolymer (B), which has been desired to be improved, is desired. It is possible to obtain a material having characteristics of the fluorinated copolymer (B) such as high insulation while greatly improving crack resistance.
The fluororesin mixture may be prepared by a known method such as mixing and melting (mixing and kneading) two or more fluororesins having different melting points. The melt mixing can be performed at a temperature equal to or higher than the melting point of the fluororesin having the highest melting point among two or more fluororesins having different melting points.

All of the fluororesins preferably have a melt flow rate (MFR) at 372 ° C. of 0.1 to 100 g / 10 min. When the MFR is in the above range, the crosslinking effect is remarkable.
The MFR is more preferably 0.5 g / 10 min or more, more preferably 80 g / 10 min or less, and still more preferably 40 g / 10 min or less. According to ASTM D1238, the MFR uses a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), and the mass of the polymer flowing out per 10 minutes from a nozzle having an inner diameter of 2 mm and a length of 8 mm under a load of 372 ° C. and 5 kg ( g / 10 minutes).

The modified fluororesin mixture of the present invention comprises a mixture of two or more fluororesins having different melting points. Among the fluororesins contained in the mixture, the melting point of the fluororesin having the highest melting point or less and the glass transition It can be obtained by irradiating the fluororesin mixture with radiation at an irradiation temperature equal to or higher than the glass transition temperature of the highest fluororesin. Accordingly, even after the fluororesin mixture is molded into a desired shape, radiation can be irradiated without impairing the shape of the molded product.
As described above, the mixture of two or more kinds of fluororesins is heated to the above-mentioned specific range of temperatures and irradiated with radiation, whereby the crack resistance is improved. Because it has many large side chains and these side chains move greatly even at low temperatures, it is assumed that the effect of irradiation with radiation can be sufficiently obtained even at low temperatures. .

The irradiation temperature is composed of a mixture of two or more fluororesins having different melting points. Among the fluororesins contained in the mixture, the irradiation temperature is lower than the melting point of the highest fluororesin and has the highest glass transition temperature. It is above the glass transition temperature of the resin. Specifically, the irradiation temperature is preferably 150 to 300 ° C. The crack resistance of the said mixture obtained as it is the above-mentioned temperature range becomes more favorable.
The irradiation temperature is preferably lower than the melting point of the fluororesin having the lowest melting point among the fluororesins contained in the mixture, and more preferably 20 ° C. lower than the melting point of the fluororesin having the highest melting point. Preferably, the temperature is lower by 25 ° C. or more.
As said irradiation temperature, it is more preferable that it is 180 degreeC or more, It is still more preferable that it is 200 degreeC or more, It is more preferable that it is 275 degrees C or less, It is further more preferable that it is 270 degrees C or less.

The adjustment of the irradiation temperature is not particularly limited, and can be performed by a known method. Specifically, for example, a method of holding the above-mentioned fluororesin mixture in a heating furnace maintained at a predetermined temperature, a method of placing on a hot plate and energizing a heater built in the hot plate, or an external heating means The method of heating a hot plate by is mentioned.

Examples of the radiation include electron beams, ultraviolet rays, gamma rays, X-rays, neutron rays, high energy ions, and the like. Among these, an electron beam is preferable because it has excellent transmission power, a high dose rate, and is suitable for industrial production.
The method of irradiating with radiation is not particularly limited, and examples thereof include a method performed using a conventionally known radiation irradiating apparatus.

Specifically, the radiation dose is preferably 10 kGy to 250 kGy. If it is less than 10 Gy, the amount of radicals involved in the crosslinking reaction is insufficient, and the crosslinking effect may not be sufficiently exhibited. If it exceeds 250 kGy, the molecular weight may be lowered due to main chain cleavage, and the mechanical strength may be greatly reduced.
The irradiation dose of radiation is more preferably 30 kGy or more, further preferably 40 kGy or more, more preferably 220 kGy or less, and further preferably 200 kGy or less.

The irradiation environment is not particularly limited, but the oxygen concentration is preferably 1000 ppm or less, more preferably in the absence of oxygen, and in an inert gas atmosphere such as nitrogen, helium or argon More preferably, it is in the middle.

Thus, the modified fluororesin mixture which has the outstanding crack resistance can be obtained by irradiating the mixture of the 2 or more types of fluororesins described above with radiation at a specific range of irradiation temperature. For this reason, the fluororesin molded product formed using the modified fluororesin mixture of the present invention is excellent in crack resistance.
Such a fluororesin molded article comprising the modified fluororesin mixture of the present invention is also one aspect of the present invention.

In addition, the fluororesin molded product of the present invention includes a step of molding a mixture of two or more fluororesins having different melting points, a glass transition or less than the melting point of the fluororesin having the highest melting point among the fluororesins. It is obtained by a method for producing a molded article having a step of irradiating radiation to the mixture of the fluororesin molded at an irradiation temperature equal to or higher than the glass transition temperature of the fluororesin having the highest temperature. Preferably there is.
A fluororesin molded product obtained by such a specific manufacturing method is also one aspect of the present invention.

By molding a mixture of two or more fluororesins having different melting points into a desired shape and then irradiating the mixture at the irradiation temperature described above, a molded article having excellent crack resistance can be obtained.
Examples of the fluororesin include the same fluororesins as described above.

The method for molding the fluororesin mixture is not particularly limited, and examples thereof include known methods such as injection molding, extrusion molding, inflation method, T-die method, and compression molding. What is necessary is just to select these shaping | molding methods suitably according to the shape of the molded article obtained.
Among these, compression molding, injection molding, or extrusion molding is preferable, and injection molding or extrusion molding is more preferable in terms of facilitating molding of a minute or complicated shape. As the extrusion molding, wire coating extrusion molding, tube extrusion molding, profile extrusion molding, film extrusion molding, fiber extrusion molding and the like are particularly suitable.

The fluororesin molded product of the present invention is produced by irradiation with radiation at a predetermined irradiation temperature after the step of molding the above-mentioned fluororesin mixture.
A method of irradiating the above fluororesin mixture formed into a desired shape with radiation at an irradiation temperature not higher than the melting point of the fluororesin having the highest melting point and not lower than the glass transition temperature of the fluororesin having the highest glass transition temperature. Examples of the method include the same methods as described above.

The fluororesin molded product of the present invention may also contain other components as necessary. Other components include additives such as crosslinking agents, antistatic agents, heat stabilizers, foaming agents, foaming nucleating agents, antioxidants, surfactants, photopolymerization initiators, antiwear agents, surface modifiers, etc. Can be mentioned.

The shape of the fluororesin molded product of the present invention is not particularly limited, and examples thereof include films, sheets, plates, rods, blocks, cylinders, containers, electric wires, and tubes. Especially, a sheet | seat and an electric wire are preferable at the point with a severe request | requirement of crack resistance.
The thickness of the sheet is preferably 0.01 to 10 mm.

Although the fluororesin molded product of this invention is not specifically limited, For example, it can apply to the following uses. For example, it can be applied to diaphragm pump diaphragm parts, bellows molded products, wire coating materials, thin-walled tubes, etc. Especially, the diaphragm parts of diaphragm pumps and wire coating materials are required to have resistance to cracking due to repeated motion. It is preferable to be used for the member of the place to be used.

The present invention also includes a step of molding a mixture of two or more kinds of fluororesins having different melting points, and a fluororesin having a glass transition temperature which is not higher than the melting point of the fluororesin having the highest melting point and has the highest glass transition temperature. It is also a method for producing a fluororesin molded product, comprising a step of irradiating the molded mixture of the fluororesin with radiation at an irradiation temperature equal to or higher than the glass transition temperature.
As said fluororesin, the thing similar to the fluororesin mentioned above is mentioned.
The step of molding the fluororesin mixture may be performed in the same manner as the method of molding the fluororesin mixture described above.
The step of irradiating the radiation may be performed in the same manner as the method of irradiating the fluororesin mixture described above.

As described above, according to the present invention, a modified fluororesin mixture having improved crack resistance and a fluororesin molded product can be obtained.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited only to these Examples.

The monomer unit content, MFR, melting point, and glass transition temperature were measured by the following methods.

(Monomer unit content)
The content of each monomer unit was measured by ¹⁹ F-NMR method.

(MFR)
According to ASTM D1238, using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the mass of the polymer flowing out per 10 minutes from a nozzle having an inner diameter of 2 mm and a length of 8 mm under a load of 372 ° C. and 5 kg (g / 10 minutes) )

(Glass transition temperature (Tg))
The dynamic viscoelasticity measurement using DVA-220 (made by IT Measurement Control Co., Ltd.) was performed and determined. The temperature was measured at a rate of temperature increase of 2 ° C./min and a frequency of 10 Hz, and the temperature at the peak of the tan δ value was defined as the glass transition temperature.

(Melting point)
The melting point is a temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 ° C./min using a differential scanning calorimeter [DSC].

Example 1
Fluororesin (A) [tetrafluoroethylene (TFE) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / PPVE = 94.5 / 5.5 (mass ratio)], MFR 25 g / 10 min, melting point 302 ° C., Tg 93 ° C] and fluororesin (B) [tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / HFP / PPVE = 88/11 / 1.0 (mass) Ratio), MFR 25 g / 10 min, melting point 250 ° C., Tg 85 ° C.] were mixed at a mass ratio of 70:30 or 30:70. The obtained mixture was melt-kneaded with a twin-screw extruder (330 ° C.) and re-pelletized to prepare a mixed resin. This mixed resin was processed into a sheet having a thickness of 0.215 mm by a heat press molding machine (330 ° C.) and cut into a strip having a width of 13.0 mm and a length of 130 mm to obtain a test piece.
The obtained test piece was accommodated in an electron beam irradiation container of an electron beam irradiation apparatus (manufactured by NHV Corporation), and then nitrogen gas was added to bring the container into a nitrogen atmosphere. After raising the temperature in the container to 245 ° C. and stabilizing the temperature, the specimen was irradiated with an electron beam under the conditions of an electron beam acceleration voltage of 3000 kV and an irradiation dose intensity of 20 kGy / 5 minutes.
The test piece after the irradiation was subjected to the following MIT repeated bending test. The results are shown in Table 1.

(MIT repeated bending test)
Performed according to ASTM D2176. Specifically, the test piece having a width of 13.0 mm and a length of 130 mm after irradiation with the electron beam obtained above is mounted on an MIT measuring instrument (model number 12176, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) and a load of 1 The test piece was bent under the conditions of .25 kg, left and right bending angles of 135 degrees and the number of bending times of 175 times / minute, and the number of times until the test piece was cut (the number of MIT repetitions) was measured.

(Examples 2 to 11 and Comparative Examples 1 to 4)
A test piece was obtained in the same manner as in Example 1 except that the electron beam irradiation was performed at the mixing ratio, irradiation temperature, and irradiation dose of the fluororesin described in Table 1, and the MIT repeated bending test was performed. The results are shown in Table 1.

(Examples 12-16, Comparative Examples 5-8)
Fluororesin (A) [tetrafluoroethylene (TFE) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / PPVE = 94.5 / 5.5 (mass ratio), MFR 2.0 g / 10 min, melting point 302 ° C. , Tg 93 ° C.] and fluororesin (B) [tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / HFP / PPVE = 88/11 / 1.0] (Mass ratio, MFR 1.0 g / 10 min, melting point 257 ° C., Tg 85 ° C.), except that the raw materials were mixed in a mass ratio of 70:30, 30:70, or 10:90. In the same manner as in No. 1, a test piece was obtained and subjected to a MIT repeated bending test. The results are shown in Table 2.

(Examples 17 to 21, Comparative Examples 9 to 12)
Fluororesin (A) [tetrafluoroethylene (TFE) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / PPVE = 94.5 / 5.5 (mass ratio)], MFR 70 g / 10 min, melting point 302 ° C., Tg 93 ° C] and fluororesin (B) [tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) / perfluoropropyl vinyl ether (PPVE) copolymer, TFE / HFP / PPVE = 88/11 / 1.0 (mass) Ratio), MFR 65 g / 10 min, melting point 257 ° C., Tg 85 ° C.], except that a raw material mixed in a mass ratio of 70:30, 30:70, or 10:90 was used as in Example 1. Thus, a test piece was obtained and subjected to a MIT repeated bending test. The results are shown in Table 3.

The molded product made of the modified fluororesin mixture of the present invention can be applied to various uses requiring crack resistance, such as a diaphragm part of a diaphragm pump or a bellows molded product, a wire coating material, and a thin tube.

Claims (8)

It consists of two or more fluororesins with different melting points,
By irradiating the mixture of fluororesins with radiation at an irradiation temperature not higher than the melting point of the fluororesin having the highest melting point and not lower than the glass transition temperature of the fluororesin having the highest glass transition temperature. A modified fluororesin mixture characterized by being obtained. A fluororesin molded article comprising the modified fluororesin mixture according to claim 1. Forming a mixture of two or more fluororesins having different melting points; and
Radiation is applied to the molded mixture of the fluororesin at an irradiation temperature not higher than the melting point of the fluororesin having the highest melting point and not lower than the glass transition temperature of the fluororesin having the highest glass transition temperature. A fluororesin molded product obtained by a method for producing a molded product having a step of: The fluororesin molded product according to claim 2 or 3, wherein the fluororesin has a melt flow rate at 372 ° C of 0.5 to 100 g / 10 min. The fluororesin is composed of a fluorine-containing copolymer (A) containing only tetrafluoroethylene units and perfluoro (alkyl vinyl ether) units, and a fluorine-containing copolymer (B) containing tetrafluoroethylene units and hexafluoropropylene units. The fluororesin molded product according to claim 2, 3 or 4. 6. The fluororesin molded article according to claim 5, wherein a mass ratio ((A) / (B)) of the fluorinated copolymer (A) to the fluorinated copolymer (B) is from 1/9 to 7/3. Forming a mixture of two or more fluororesins having different melting points; and
Radiation is applied to the molded mixture of the fluororesin at an irradiation temperature not higher than the melting point of the fluororesin having the highest melting point and not lower than the glass transition temperature of the fluororesin having the highest glass transition temperature. A process for producing a fluororesin molded product comprising the step of: The method for producing a fluororesin molded product according to claim 7, wherein the irradiation temperature is 150 to 300 ° C., and the irradiation dose of radiation is 10 kGy to 250 kGy.