JP3736351B2 - Method and apparatus for producing modified fluorine resin - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for producing a modified fluororesin, and in particular, a method and an apparatus for producing a modified fluororesin that crosslink the fluororesin by irradiating the fluororesin with ionizing radiation under a low oxygen partial pressure. About.
[0002]
[Prior art]
The modified fluororesin is produced by irradiating the fluororesin with ionizing radiation (hereinafter referred to as radiation) under a low oxygen partial pressure to crosslink the fluororesin. Conventionally, in order to place the fluororesin under a low oxygen partial pressure, the fluororesin is placed in a sealed container that is cut off from the atmosphere, and the fluororesin is irradiated with radiation in the hermetic container.
[0003]
[Problems to be solved by the invention]
However, in this method, it is necessary to make the entire radiation irradiation apparatus for producing the modified fluorine resin airtight. In addition, it takes a long time for exhaust and gas exchange to lower the oxygen partial pressure to a predetermined value after the fluororesin is placed in the radiation irradiation apparatus. Naturally, the time required for evacuation depends on the ability of an evacuation device such as a vacuum pump.
[0004]
In addition, special measures are required to feed the fluororesin material into an airtight irradiation apparatus and take out the irradiated material from the apparatus, which greatly restricts the material transport means and the processing capacity of the apparatus.
[0005]
An object of the present invention is to eliminate the waiting time required for lowering the oxygen partial pressure to a predetermined value, which is required when the fluororesin is crosslinked in a radiation irradiation apparatus that is hermetically sealed.
[0006]
Another object of the present invention is to eliminate restrictions on conveying means and processing capacity associated with a method of crosslinking a fluorine resin in a radiation irradiation apparatus that is kept airtight.
[0007]
The present invention further eliminates the waiting time required to reduce the oxygen partial pressure to a predetermined value, which is required when the fluororesin is crosslinked in a radiation irradiation apparatus that is kept airtight, and further improves the conveying means and processing capacity. It is an object of the present invention to provide a modified fluororesin manufacturing apparatus that eliminates the limitations and is efficient and low in cost.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the present invention provides a modified fluororesin manufacturing method in which ionizing radiation is irradiated to crosslink the fluororesin, and a gas stream having a predetermined oxygen partial pressure in an open space is applied to the fluororesin. The fluorine resin is irradiated with the ionizing radiation at a point where the oxygen partial pressure becomes the lowest while spraying , and the fluorine resin is crosslinked.
[0009]
The apparatus for producing a modified fluororesin of the present invention crosslinks this fluororesin by irradiating it with ionizing radiation while transporting the fluororesin at a predetermined temperature and under a predetermined oxygen partial pressure lower than that in the atmosphere. In the modified fluororesin manufacturing equipment,
A compartment of a space that is extended in the horizontal direction through which the fluororesin passes and is open to the atmosphere at both ends; a transport means for transporting the fluororesin along the compartment; and a center in the horizontal direction of the compartment Irradiating means for irradiating ionizing radiation from above in the vertical direction at the position, heating means for heating the irradiation position in the section by the irradiating means to a predetermined temperature, and a plurality provided along the section and passing through the section Gas flow jetting means for blowing a gas flow having a predetermined oxygen partial pressure to the fluororesin.
[0010]
As ionizing radiation, X-rays, γ-rays, electron beams, and high-energy ion fluxes can be used. You may use a neutron beam instead of these or with these.
[0011]
The predetermined oxygen partial pressure is 100 torr or less. If it exceeds 100 torr, the crosslinking reaction is suppressed, the resin is deteriorated by thermal decomposition, and the mechanical strength and the elongation amount are reduced. The air stream may contain an inert gas such as argon, helium, or nitrogen. Gases such as hydrogen, carbon dioxide, carbon monoxide, methane, ethane, ethylene, and acetylene may be included as necessary.
[0012]
The method of the present invention can be applied to tetrafluoroethylene polymers including copolymers and is useful. In particular, it is useful for polytetrafluoroethylene, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymers, and tetrafluoroethylene-hexafluoropropylene copolymers.
[0013]
The irradiation with radiation is preferably performed at a temperature 10 to 30 ° C. higher than the melting point of the fluororesin. Many of the fluororesins have a melting point of 270 ° C. to 330 ° C. For example, in the case of polytetrafluoroethylene having a melting point of 310 ° C., the irradiation temperature is suitably 320 to 340 ° C. In order to heat the fluororesin to such a temperature, a heater or the like is used as usual.
[0014]
A low oxygen partial pressure air flow is obtained by blowing a gas having an appropriate composition from a container having an internal pressure of 1.01 to 5.0 atm onto the fluororesin, so that the fluororesin is discharged from the atmosphere outside the apparatus. Blocked.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a radiation irradiation apparatus used in the method of the present invention. This apparatus includes a gantry 1, a roller conveyor 2, heaters 4 a and 4 b, a gas pipe 5, titanium foils 6 a and 6 b, a top plate 7, and a particle accelerator 8. The gas pipe 5 has a branch pipe 5a. This apparatus is suitable for continuously irradiating a sheet-like fluorine resin.
[0016]
On the gantry 1, the fluororesin material 3 is conveyed from the right to the left in the figure by the roller conveyor 2, and is heated from both the upper and lower sides by the heaters 4a and 4b (for example, 340 ± 5 ° C.). A gas flow having a low oxygen concentration discharged from the branch pipe 5a of the gas pipe 5 is blown onto the upper surface of the fluororesin material 3. For example, nitrogen gas having an oxygen partial pressure of 100 torr or less is blown out from the gas pipe 5 having an internal pressure of 5 atm onto the fluororesin material 3 through the branch pipe 5a. The fluorine resin material 3 which is cut off from the atmosphere by the gas stream and placed under a low oxygen partial pressure is irradiated with γ rays including electron beams from the particle accelerator 8 through the titanium foils 6a and 6b. At the site where irradiation takes place, the oxygen partial pressure inside the device is lowest because it is farthest from the material inlet and outlet of the device. The material inlet and outlet are made as small as possible to keep the oxygen partial pressure in the apparatus low.
[0017]
FIG. 2 shows another radiation irradiation apparatus used in the method of the present invention. This apparatus is a radiation cross-linking reforming apparatus of a fluororesin material (for example, a block shape) having a large thickness. The main part of this apparatus is the same as the apparatus of FIG. 1, from the gantry 1, the roller conveyor 12, the heaters 4 a and 4 b, the gas pipe 5, the branch pipe 5 a, the titanium foils 6 a and 6 b, the top plate 7, and the particle accelerator 8. Become. In addition to this, the apparatus of FIG. 2 has a container 13 and six partition plates 9A, 9B, 9C, 9D, 9E, and 9F for reducing the intrusion of outside air. In this respect, the apparatus of FIG. Different. The partition plates 9A and below can be opened and closed for transferring the fluororesin material 3, but are not sealed. The fluororesin material 3 is stopped at each of the five sections A, B, C, D, and E between the partition plates 9A to 9F, heated to a low oxygen concentration, and irradiated with radiation in the section C. That is, this apparatus is a semi-continuous processing system.
[0018]
On the gantry 1, the fluororesin material 3 is conveyed from the right to the left in the figure by the roller conveyor 12. The partition plate 9A is first opened, and the fluororesin material 3 enters the section A and is heated from above by the heater 14a. The partition plate 9A is closed, and a gas flow having a low oxygen concentration released from the branch pipe 5a of the gas pipe 5 is blown onto the upper surface of the fluororesin material 3. When the oxygen concentration in the compartment A becomes sufficiently low, the partition plate 9B is opened, the fluororesin material 3 is transferred to the compartment B, and the partition plate 9B is closed. The fluororesin material 3 is further heated by the heater 14a under an air flow having a low oxygen concentration released from the branch pipe 5a. The fluororesin material 3 heated in stages in this way is transferred to the section C and heated to, for example, 340 ± 5 ° C. by the heaters 14a and 14c.
[0019]
Fluorine resin material 3 heated under a low oxygen partial pressure is irradiated with γ rays including an electron beam from particle accelerator 8 through titanium foils 6a and 6b in section C. In zone C where irradiation takes place, the oxygen partial pressure is lowest because it is farthest from the material inlet and outlet of the device. After the crosslinking reaction, the partition plate 9D is opened, and the fluororesin material 3 is sent from the section C to the section D, and further sent to the section E while being heated under a low oxygen partial pressure. When the partition plate 9F is opened and the fluororesin material 3 is sent out from the last section E, the partition plate 9F is closed, and the interior of the section E once opened to the atmosphere is reduced again by the air flow from the branch pipe 5a. To recover.
[0020]
The apparatus of FIG. 2 can also be used when the fluororesin material 3 is a powder. The powder is put in a container 13 and placed on a roller conveyor 12 and irradiated with radiation.
[0021]
【The invention's effect】
According to the method for producing a modified fluororesin of the present invention, it is not necessary to keep the entire radiation irradiation apparatus for cross-linking the fluororesin, so that no waiting time is required until the oxygen partial pressure is lowered to a predetermined value. In addition, the restrictions on the conveying means and processing capability in the conventional method of cross-linking the fluororesin with the radiation irradiation apparatus kept airtight are eliminated. As a result, the modified fluorine resin can be produced efficiently and at a low cost.
[0022]
According to the modified fluororesin manufacturing apparatus of the present invention, there is no need for a long waiting time until the oxygen partial pressure is lowered to a predetermined value as in the case of cross-linking the fluororesin in a radiation irradiation apparatus that is kept airtight. Moreover, since restrictions on the conveying means and processing capacity are eliminated, the modified fluororesin can be produced efficiently and at a low cost.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a radiation irradiation apparatus used in the method of the present invention. FIG. 2 is an explanatory diagram of a radiation irradiation apparatus used in the method of the present invention.
DESCRIPTION OF SYMBOLS 1 Stand 2 Roller conveyor 3 Fluororesin material 4a, 4b Heater 5 Gas piping 5a Branch pipe 6a, 6b Titanium foil,
7 Top plate 8 Particle accelerator 9A, 9B, 9C, 9D, 9E, 9F Partition plate 12 Roller conveyor 13 Container 14a, 14c Heater A, B, C, D, E Section

Claims (9)

In a method for producing a modified fluororesin, which is irradiated with ionizing radiation to crosslink the fluororesin,
While blowing a gas stream having a predetermined oxygen partial pressure to the fluorine resin in an open space, the fluorine resin is irradiated with the ionizing radiation at a point where the oxygen partial pressure is lowest. A method for producing a modified fluororesin, characterized by crosslinking. The method for producing a modified fluororesin according to claim 1 , wherein the predetermined oxygen partial pressure is 100 torr or less . The method for producing a modified fluororesin according to claim 1 , wherein the gas stream is generated by releasing a pressurized gas into the open space . The method for producing a modified fluororesin according to claim 1 , wherein the fluororesin is crosslinked by irradiating the ionizing radiation at a predetermined temperature . 5. The method for producing a modified fluororesin according to claim 4 , wherein the predetermined temperature is 10 to 30 ° C. higher than the melting point of the fluororesin. The method for producing a modified fluororesin according to claim 4 , wherein the predetermined temperature is obtained by heating the fluororesin. The method for producing a modified fluororesin according to claim 4 , wherein the predetermined temperature is obtained by heating the gas stream or the pressurized gas . An apparatus for producing a modified fluorine resin, which is irradiated with ionizing radiation while being conveyed at a predetermined temperature and under a predetermined partial pressure of oxygen lower than that in the atmosphere, and the fluorine resin is crosslinked and modified. In
  A compartment of a space through which the fluororesin passes, provided extending in the horizontal direction and open to the atmosphere at both ends;
  Conveying means for conveying the fluororesin along the compartment;
  Irradiating means for irradiating ionizing radiation from above in the vertical direction at the horizontal center position of the section;
  Heating means for heating the irradiation position in the section by the irradiation means to a predetermined temperature;
  A modified fluorine resin comprising: a plurality of gas flow jetting means for blowing a gas flow having a predetermined oxygen partial pressure to the fluorine resin that is provided along the compartment and that passes through the compartment. Manufacturing equipment. 9. The apparatus for producing a modified fluororesin according to claim 8 , wherein the predetermined oxygen partial pressure is 100 torr or less, and the predetermined temperature is 10 to 30 ° C. higher than the melting point of the fluororesin.

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