JP2562654Y2 - Container for electron beam irradiation treatment of polytetrafluoroethylene - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a PTFE electron beam irradiation container in which an electron beam irradiation process is performed while moving an irradiation container containing polytetrafluoroethylene (hereinafter referred to as PTFE) using a conveyor means or the like. It is about.

[0002]

2. Description of the Related Art In general, PTFE fine powder produced by irradiating PTFE with ionizing radiation to reduce its molecular weight is dispersed and blended in printing inks, paints, lubricating oils, raw materials for plastic molding, and the like, and is used for printing inks and paints. In addition to improving the flow characteristics during molding, plastic molding materials improve the abrasion resistance of the printed surface or coating film, and lubricating oils prevent machine noise and prolong the life of the machine due to improved abrasion resistance. It is used in various industrial fields for the purpose of improving the abrasion resistance and chemical resistance of products after molding.

Conventionally, as a method for irradiating PTFE with ionizing radiation, for example, a method of gamma ray irradiation and electron beam irradiation by a cobalt 60 radiation source has been used. When irradiating with gamma rays, a method has been adopted in which PTFE is stored in a gas-permeable container (such as a cardboard box or a metal container with an opening) in the vicinity of a cobalt 60 radiation source and irradiated in a stationary state. Since the dose rate (radiation dose per unit time) of a gamma ray from a 60 source is as low as 1 to 10 kGy / hour, it takes a long time to give an absorbed dose of 30 kGy to 3000 kGy required to reduce the molecular weight of the PTFE. It costs. Further, PTFE decomposition gas (hydrogen fluoride and oxidizable fluoride) is generated little by little during irradiation and for a long time after irradiation. The decomposition gas generated during the irradiation is diffused and mixed into the air in the irradiation chamber, and its concentration is as low as about 1 PPM. The air in the irradiation chamber is sucked, brought into contact with an alkaline aqueous solution to absorb the decomposed gas, and then released to the atmosphere. Further, since the dose rate of the heat generated by the irradiation is low, the heat is not excessively heated by the thermal diffusion.

On the other hand, in the case of the electron beam irradiation treatment, the dose rate reaches about 1000 times that of gamma rays, and therefore, there is an advantage that a short-time irradiation gives a necessary absorbed dose.

[0005]

However, in this electron beam irradiation, the decomposition gas concentration and the temperature rise of the PTFE are extremely high, and the decomposition gas concentration is 100 PP in the irradiation container.
M or more, and may exceed 1000 PPM depending on conditions. In addition, the PTFE temperature also rises with the absorbed dose, and when the dose is large, the PTFE temperature becomes higher than the melting temperature of PTFE, and undesired changes such as discoloration and deterioration occur.

In order to solve these problems, for example, using a ribbon blender or the like, cooling water is passed through a water cooling jacket or water is directly sprayed on the PTFE powder while mechanically stirring PTFE in a fluid state. For example, there has been proposed a method of performing a batch treatment in which heat is removed by such a method as described above, a decomposition gas is sucked, and a contact neutralization treatment is performed with an aqueous alkali solution (Japanese Patent Laid-Open No. 1-294010). However, this method requires a large amount of equipment and a large amount of equipment investment, and therefore is not suitable for mass processing or dedicated processing. On the other hand, the unpolymerized PTFE emulsion-polymerized is mechanically stirred at a high temperature or coagulated and solidified when subjected to excessive vibration, so that the blender method cannot be adopted.

The present invention has been made in view of the above circumstances, and has as its object to provide a PTFE electron beam irradiation processing container which solves the above-mentioned problems by providing an irradiation container provided with a device capable of processing a decomposition gas. It is.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a high molecular weight P
In order to reduce the molecular weight of TFE and to facilitate the pulverization, the container to be subjected to electron beam irradiation while being moved using a conveyor or other transport means has a thin main body with a window made of a thin metal or the like through which the electron beam can be sufficiently transmitted. Container and
In addition, the container body is provided with an absorbing can filled with an absorbent for absorbing a decomposition gas generated by electron beam irradiation, and is provided with an air outlet for cooling a rise in temperature due to electron beam irradiation.

[0009]

As described above, at the end of the container body, there are provided an absorption can filled with an absorbent for absorbing decomposition gas generated by electron beam irradiation, and a blowing port for cooling a temperature rise caused by electron beam irradiation. Thereby, the electron beam transmitted through the thin metal window on the upper surface of the container body irradiates the inside PTFE,
The absorption of this energy breaks the molecular chains and generates decomposed gas such as hydrogen fluoride and oxidizable fluoride. The decomposed gas flows into the absorption can on the side of the container body and is absorbed by the absorbent, and the generated gas Only the gas (air) from which air has been removed is released to the atmosphere, and the heat generated by the absorption of energy is taken away and cooled by the air blown from the blowing port, and this hot air is similarly released to the atmosphere via the absorption can. You.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings of embodiments.

FIGS. 1 and 2 show an embodiment in which PTFE is accommodated in the lower part of an irradiation container. Reference numeral 1 denotes a container main body which is a rectangular thin housing, and the upper surface of the container main body 1 is capable of sufficiently transmitting an electron beam. A thin metal window 2 made of, for example, titanium or stainless steel foil, is disposed, a predetermined gap 3 through which cooling air can flow through an upper portion 1a of the container body 1, and a high molecular weight P
An absorption can 6 containing TFE 4 and filled with an absorbent 5 made of silica gel, activated carbon, or a mixture of activated carbon and alumina silica gel is connected to one end of the upper gap 3 of the container body 1. The upper end of the can 6 is provided with a suction port 7 communicating with a suction pump (not shown). Also,
At the other end of the upper gap 3 of the container body 1, there is disposed a blower tube 9 whose blower opening 8 faces. In the middle of the blower pipe 9, there is a valve 10.
The valve 10 is normally closed, and only one end on the absorption can 6 side is opened to make the container body 1 hermetically closed. Thus, the entire structure constitutes a container 11 for electron beam irradiation processing.

Now, this operation will be described.
When the PTFE 4 is irradiated with the electron beam, the PTFE 4 is placed in the lower part of the electron beam irradiation processing container 11 by removing the window 2 serving as a lid and accommodating a thickness amount enough to allow the electron beam a to pass therethrough. To a closed state.

In this case, the electron beam irradiation processing container 11 is mounted on, for example, a conveying means, that is, a roller conveyor A as shown in FIG. When the electron beam a emitted from the scan horn C passes below the take-out scan horn C, the electron beam a passes through the thin metal window 2 serving as an electron beam incident surface. When the acceleration energy of, for example, 5 MV, the thin metal window 2 has a window material of 50 μm to 20 μm when using titanium or stainless steel foil.
A thickness of 0 μm is good.

Here, when the PTFE 4 is irradiated with the electron beam a, the energy is absorbed and the molecular weight decreases. At this time, the temperature inside the container rises (unless the electron beam reaches the bottom of the container, a sufficient reaction occurs. Therefore, the container itself is inevitably heated and the temperature rises), and highly toxic decomposition gas b mainly composed of hydrogen fluoride is generated. Due to the generation of the decomposed gas, the volume of the air in the container 11 expands, and the decomposed gas flows into the communicating can 6 which is adsorbed by the absorbent 5, and the clean gas is released to the atmosphere from the suction port 7 side. You.

Further, the cooling air blow port 8 attached to the container 11 keeps the valve 10 closed during normal irradiation processing, but cool air is blown to promote the depolymerization of PTFE 4 or to remove heat. In the case of blowing, the valve 10 is opened, the air outlet 8 is opened, the air c flows into the gap (gap) 3, and the air c is forcibly sucked by a suction pump (not shown) connected to the suction port 7 of the absorption can 6. In addition, heat removal inside the container, treatment of a decomposition gas such as hydrogen fluoride adsorbed on the PTFE 4, and supply of oxygen to the PTFE 4 can be simultaneously performed. In particular, in the case of emulsion-polymerized PTFE, irradiation treatment can be performed without applying external stress, so that the molecular weight can be reduced without impairing its physical properties.

FIGS. 3 and 4 show another embodiment in which a heat absorbing water tank is combined with the bottom of the container body. In this case, the PTFE 4 housed in the container body 1 is
2 and the like, and intermediate storage is provided to form gaps 3 and 13 in the upper and lower portions, and a water tank 14 for absorbing excess heat passing through the PTFE layer is attached to the bottom of the container body 1 to form a stacked structure. At this time, the cooling air blowing port 8 is disposed at one end of the lower gap 13, and the cooling air c from the blowing port 8 rises in the wire mesh 12 and the PTFE 4 and passes through the upper gap 3 to the absorption can 6 side. Take the channel that flows to.

At this time, the PTFE 4 is irradiated with a sufficient electron beam a from above, and the electron beam a
4, the bottom surface of the container is not directly located on the lower surface of the PTFE 4, and the bottom surface of the container is provided with a gap 13 therebetween. A water tank 14 into which water is injected to absorb heat is provided on the bottom surface of the container. As a result, excess energy is absorbed by the water tank 14, so that the temperature of the container body 1 does not rise due to heating, and the material (PTFE 4) is prevented from overheating.

EXAMPLE A 100 μm stainless steel foil window was attached to an irradiation treatment vessel having a length of 148 cm, a width of 45 cm, and a depth of 10 cm, and 12 kg of PTFE was put therein and leveled. The cracking gas absorption can is filled with a cylinder of 5 cm in diameter and 15 cm in length filled with 300 g of kneaded pellets of 30% activated carbon and 70% silica-alumina gel. Irradiation conditions are such that a single irradiation gives an absorption dose of 25 kGy to PTFE. Was set and irradiated 24 times using a conveyor to give an absorbed dose of 600 kGy.

Irradiation conditions Acceleration voltage 5 MV Beam current 10 mA Conveyor speed 2 m / min Table 1 shows the absorbed dose and the concentration of hydrogen fluoride released into the atmosphere through the absorber.

[0020]

When the melting point was measured as a measure of the molecular weight distribution of the irradiated PTFE, it was found to be 313 ° C., and a decrease in the molecular weight equivalent to that of the PTFE irradiated with 600 kGy by gamma rays was recognized. In addition, the PTF that has been subjected to the main irradiation treatment under the same conditions as the PTFE that has been subjected to the irradiation treatment of 600 kGy with gamma rays
As a result of pulverizing E with a fine pulverizer, the particle size distribution obtained a result equivalent to that obtained by γ-ray treatment.

As shown in the above embodiment, the irradiation container of the present invention can be used to reduce the molecular weight of PTFE by an electron beam irradiation apparatus equipped with a conveyor or other conveying means. Further, the material of the irradiation container of the present invention, the material of the electron beam transmitting foil window, the type of the decomposition gas adsorbent, etc. are not limited to the detailed description of the present invention, but may be any as long as they fulfill the function. .

[0023]

As described above, the PTFE electron beam irradiation processing container of the present invention has a gap for passing cool air at least above or below the PTFE layer housed in the container body of the thin case. By arranging an air canister containing an air absorber and an air vent at both ends of the main body, the toxic decomposition gas generated by electron beam irradiation is absorbed by the absorber, and the temperature rise in the container is cooled by passing cool air. Therefore, the PTFE does not raise the temperature more than necessary, does not cause discoloration, deterioration, and the like, and does not cause indoor pollution because there is no exhaust of the decomposition gas. In addition, the present invention has the advantages that the structure is simplified, the manufacturing is easy, the electron beam irradiating device and the transporting means can be made compact, the installation is simple, and the operation is easy. It should be noted that a slat conveyor, a traveling cart, a tray, or the like may be used as a means for conveying the irradiation container in addition to the illustrated roller conveyor.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of an electron beam irradiation processing container showing an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a partially cutaway side view of an electron beam irradiation processing container showing another embodiment.

FIG. 4 is a plan view of the same.

FIG. 5 is an explanatory diagram of electron beam irradiation on a container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container main body 2 Thin metal window 3 Gap 5 Absorbent 6 Absorber can 8 Blast port

Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // B29K 27:18

Claims (1)

(57) [Scope of request for utility model registration] 1. A container which is subjected to an electron beam irradiation process while moving using a conveyor means or the like in order to reduce the molecular weight of high molecular weight polytetrafluoroethylene and to facilitate pulverization. A thin container with a window made of a thin metal or the like that is sufficiently permeable, and an absorbent can filled with an absorbent that absorbs decomposition gas generated by electron beam irradiation are provided in the container body, and the temperature rise due to electron beam irradiation is cooled. A container for electron beam irradiation treatment of polytetrafluoroethylene, comprising: