JP3305068B2 - Expanded polytetrafluoroethylene and method for producing the same - Google Patents
Expanded polytetrafluoroethylene and method for producing the sameInfo
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- JP3305068B2 JP3305068B2 JP26701893A JP26701893A JP3305068B2 JP 3305068 B2 JP3305068 B2 JP 3305068B2 JP 26701893 A JP26701893 A JP 26701893A JP 26701893 A JP26701893 A JP 26701893A JP 3305068 B2 JP3305068 B2 JP 3305068B2
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、発泡ポリテトラフルオ
ロエチレン（以下、ＰＴＦＥという）及びその製造方法
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expanded polytetrafluoroethylene (hereinafter referred to as PTFE) and a method for producing the same.
【０００２】[0002]
【従来の技術】ＰＴＦＥは耐薬品性と耐熱性に優れたプ
ラスチックであり、従来、産業用、民生用樹脂として広
く利用されている。また、ＰＴＦＥは結晶性高分子であ
り、その結晶融解温度が３２７℃と極めて高く、更に、
結晶融解温度以上での流動性も著しく高い。これは分子
間の凝集力が高いためである。そのため、通常の方法で
発泡体を製造することは困難である。2. Description of the Related Art PTFE is a plastic having excellent chemical resistance and heat resistance, and has been widely used as an industrial or consumer resin. PTFE is a crystalline polymer, and its crystal melting temperature is extremely high at 327 ° C.
The fluidity above the crystal melting temperature is also extremely high. This is because the cohesion between molecules is high. Therefore, it is difficult to produce a foam by an ordinary method.
【０００３】一方、ポリエチレン等の汎用ポリマーで
は、ポリマーに予め発泡剤を混合させておき、室温程度
の比較的低い温度で放射線を照射してポリマーを架橋さ
せ、その後、加熱して発泡剤を分解させて発泡体を製造
する技術が開発されている。しかし、ＰＴＦＥには適当
な発泡剤がなく、放射線架橋する技術も知られていなか
った。On the other hand, in general-purpose polymers such as polyethylene, a blowing agent is mixed with the polymer in advance, and the polymer is cross-linked by irradiating radiation at a relatively low temperature such as room temperature. A technique for producing a foam has been developed. However, PTFE does not have a suitable foaming agent, and no technology for radiation crosslinking has been known.
【０００４】本発明者らは、ポリテトラフルオロエチレ
ンの結晶融点以上の温度で酸素不存在下において１ｋＧ
ｙ以上の電離性放射線を照射することによって架橋反応
を起こさせ、耐放射線性に優れたＰＴＦＥが得られるこ
とを見いだした。さらに、得られたＰＴＦＥが低結晶性
でゴム弾性を有することも見いだした。従って、耐放射
線性のみならずゴム弾性を有するＰＴＦＥが得られた。The present inventors have proposed that 1 kG is obtained in the absence of oxygen at a temperature higher than the crystal melting point of polytetrafluoroethylene.
It has been found that a cross-linking reaction is caused by irradiation with ionizing radiation of y or more to obtain PTFE having excellent radiation resistance. Furthermore, it was found that the obtained PTFE had low crystallinity and rubber elasticity. Therefore, PTFE having not only radiation resistance but also rubber elasticity was obtained.
【０００５】しかしながら、この方法ではＰＴＦＥの放
射線架橋に際して、ＰＴＦＥをその結晶融点以上の温度
にしなければならないので、従来の発泡剤を使用してＰ
ＴＦＥ発泡体を製造することはできなかった。However, in this method, when PTFE is crosslinked by radiation, the temperature of the PTFE must be higher than its crystalline melting point.
TFE foam could not be produced.
【０００６】[0006]
【発明が解決しようとする課題】上記問題点に鑑み、本
発明は、発泡ＰＴＦＥ及びその製造方法を提供すること
を目的とする。SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide expanded PTFE and a method for producing the same.
【０００７】[0007]
【課題を解決するための手段】上記課題を解決すべく、
本発明によれば、ポリテトラフルオロエチレンに結晶融
点以上の温度で酸素不存在下において０．５ｋＧｙ／ｓ
〜１００ｋＧｙ／ｓの線量率で電離性放射線を照射する
ことから成るポリテトラフルオロエチレン発泡体の製造
法が提供される。Means for Solving the Problems In order to solve the above problems,
According to the present invention, 0.5 kGy / s of polytetrafluoroethylene in the absence of oxygen at a temperature equal to or higher than the crystal melting point is used.
A method is provided for producing a polytetrafluoroethylene foam comprising irradiating with ionizing radiation at a dose rate of １００100 kGy / s.
【０００８】また、本発明によれば、ポリテトラフルオ
ロエチレンに結晶融点以上の温度で酸素不存在下におい
て０．５ｋＧｙ／ｓ〜１００ｋＧｙ／ｓの線量率で電離
性放射線を照射して得られるポリテトラフルオロエチレ
ン発泡体が提供される。Further, according to the present invention, a polytetrafluoroethylene obtained by irradiating ionizing radiation with a dose rate of 0.5 kGy / s to 100 kGy / s in the absence of oxygen at a temperature equal to or higher than the crystal melting point. A tetrafluoroethylene foam is provided.
【０００９】上述の通り、本発明者らは、ＰＴＦＥにそ
の結晶融点以上の温度で真空或いは不活性ガス中にて放
射線を照射すると、ＰＴＦＥが架橋することを見い出し
た。このとき、高温での熱分解及び放射線分解によって
ＰＴＦＥのモノマーやオリゴマー等の分解生成物が生成
する。真空中で放射線を照射したときを例にとると、放
射線の線量率が低い場合には分解生成物はそのままＰＴ
ＦＥ外に放出されるが、線量率が高くなると分解生成物
は気泡となってＰＴＦＥ内に残り、これを冷却するとＰ
ＴＦＥ発泡体が得られる。また、不活性ガス中で放射線
を照射した場合には、放射線照射後高温の状態で脱気し
てから冷却するとＰＴＦＥ発泡体が得られる。As described above, the present inventors have found that when PTFE is irradiated with radiation in a vacuum or in an inert gas at a temperature higher than its crystalline melting point, the PTFE is crosslinked. At this time, decomposition products such as PTFE monomers and oligomers are generated by thermal decomposition and radiolysis at a high temperature. For example, when radiation is irradiated in a vacuum, if the radiation dose rate is low, the decomposition product
It is released out of the FE, but when the dose rate increases, the decomposition products remain as bubbles in the PTFE, and when this is cooled, P
A TFE foam is obtained. In addition, when irradiation is performed in an inert gas, PTFE foam is obtained by degassing at a high temperature after the irradiation and then cooling.
【００１０】放射線照射の方法は、照射時の酸化を防止
するため酸素不存在下、すなわち真空中、又は不活性ガ
ス、例えば窒素、アルゴン又はヘリウム雰囲気におい
て、結晶融点（３２７℃）以上の温度で電離性放射線
（γ線、電子線、Ｘ線、中性子線、高エネルギーイオ
ン、以下放射線という）を照射する。特に電子線を照射
すると好ましい結果が得られる。照射温度については、
ＰＴＦＥの結晶融点である３２７℃以上であることが必
要であるが、３４０℃〜３５０℃前後の温度が望まし
い。なお、本発明においては、結晶融点が３２７℃以外
であるＰＴＦＥを用いることができるのはいうまでもな
い。[0010] The irradiation method is carried out in the absence of oxygen to prevent oxidation during irradiation, that is, in a vacuum or in an atmosphere of an inert gas such as nitrogen, argon or helium at a temperature higher than the crystal melting point (327 ° C). Irradiation with ionizing radiation (γ-ray, electron beam, X-ray, neutron beam, high energy ion, hereinafter referred to as radiation). Particularly, favorable results are obtained by irradiating an electron beam. Regarding the irradiation temperature,
It is necessary to be 327 ° C. or more, which is the crystal melting point of PTFE, but a temperature of about 340 ° C. to 350 ° C. is desirable. In the present invention, it goes without saying that PTFE having a crystal melting point other than 327 ° C. can be used.
【００１１】発泡の条件は、真空中での照射と不活性ガ
ス中での照射とでは異なるが、一般的には、放射線を照
射するＰＴＦＥの厚みが厚いほど、照射温度が高いほ
ど、また、線量率が高いほど発泡し易くなる。線量率は
０．５ｋＧｙ／ｓ〜１００ｋＧｙ／ｓの範囲が好まし
く、特に０．５ｋＧｙ／ｓ〜５０ｋＧｙ／ｓの範囲が好
ましい。発生する気泡の大きさは積算線量に依存してお
り、線量の増大につれて小さくなる傾向にある。不活性
ガス中で放射線を照射する場合には、線量率の影響や照
射温度の影響は小さくなる。The foaming conditions are different between irradiation in a vacuum and irradiation in an inert gas, but in general, the thicker the PTFE to be irradiated, the higher the irradiation temperature, The higher the dose rate, the easier it is to foam. The dose rate is preferably in the range of 0.5 kGy / s to 100 kGy / s , and particularly preferably in the range of 0.5 kGy / s to 50 kGy / s . The size of the generated bubbles depends on the integrated dose, and tends to decrease as the dose increases. When irradiation is performed in an inert gas, the influence of the dose rate and the influence of the irradiation temperature are reduced.
【００１２】また、線量率と温度との関係も発泡に影響
を及ぼす。特に発泡の量と気泡の大きさに影響を及ぼ
す。本発明においては、真空中で放射線を照射するとき
には、放射線を照射しつつＰＴＦＥを発泡させ、一方、
不活性ガス中で放射線を照射するときには、放射線の照
射後に不活性ガスを脱気してＰＴＦＥを発泡させるが、
何れの場合であっても、ある程度放射線照射してＰＴＦ
Ｅを架橋してから発泡させると好ましい結果が得られ
る。[0012] The relationship between dose rate and temperature also affects foaming. In particular, it affects the amount of foam and the size of the cells. In the present invention, when irradiating the radiation in a vacuum, the PTFE is expanded while irradiating the radiation,
When irradiating radiation in an inert gas, the PTFE is foamed by degassing the inert gas after the irradiation,
In any case, PTF
Preferred results are obtained when E is crosslinked and then foamed.
【００１３】真空中で放射線を照射するときには、放射
線を照射するＰＴＦＥの厚みが１ｍｍ程度のものである
場合、ＰＴＦＥをその結晶融解温度以上に加熱して、放
射線をその線量率が５ｋＧｙ／ｓ〜５０ｋＧｙ／ｓとな
るように照射することが望ましい。一方、不活性ガス中
で放射線を照射するときには、大気圧又は加圧状態でＰ
ＴＦＥをその結晶融解温度以上に加熱して放射線を照射
し、照射後ＰＴＦＥの温度を下げる前に脱気する。一般
に、急速に脱気すると発生する個々の気泡が大きくなる
傾向になる。なお、発生する気泡の大きさは、上述の通
り積算線量にも依存する他、脱気時のＰＴＦＥの温度に
も影響される。When radiating radiation in a vacuum, if the thickness of the PTFE to be irradiated is about 1 mm, the PTFE is heated to a temperature higher than its crystal melting temperature, and the radiation is irradiated at a dose rate of 5 kGy / s. Irradiation is desirably performed at 50 kGy / s. On the other hand, when irradiating radiation in an inert gas, P
The TFE is heated above its crystal melting temperature and irradiated with radiation, degassed after the irradiation and before lowering the temperature of the PTFE. Generally, individual bubbles generated when degassing rapidly tend to become large. The size of the generated bubbles depends on the integrated dose as described above, and is also affected by the temperature of the PTFE at the time of degassing.
【００１４】積算線量は、放射線の真空中での照射及び
不活性ガス中での照射ともに１００ｋＧｙから２ＭＧｙ
の範囲が特に好ましいが、この範囲外であってもＰＴＦ
Ｅの発泡は可能である。The integrated dose ranges from 100 kGy to 2 MGy for both irradiation in a vacuum and irradiation in an inert gas.
Is particularly preferred, but even outside this range, the PTF
E foaming is possible.
【００１５】放射線が照射されるＰＴＦＥの形状には特
に制限はなく、如何なる形状のＰＴＦＥであっても改質
することができる。しかしながら、放射線を全体にわた
って均一に照射できるという観点からは、シート状や板
状の形状であることが好ましい。The shape of the PTFE to be irradiated is not particularly limited, and any shape of the PTFE can be modified. However, from the viewpoint that the radiation can be uniformly irradiated over the entirety, it is preferable that the shape be a sheet shape or a plate shape.
【００１６】本発明の方法により得られたＰＴＦＥは、
発泡体であると同時に、耐放射線性であり、しかも架橋
構造をも有するのでこれまで使用が不可能であった放射
線環境下での工業材料として、また放射線滅菌可能な医
療用具素材としての利用が可能となる。今迄は、ＰＴＦ
Ｅから成る医療用具は放射線滅菌ができなかったことか
ら、蒸気、あるいはガス滅菌に因っているが、滅菌の確
実性の点から放射線滅菌の利用が可能となる。また、得
られたＰＴＦＥ発泡体はゴム特性も備えることから、特
に、耐熱、耐薬品性を要請される機器類の熱絶縁材料や
シール材料やパッキング材料としての特性の著しい向上
が期待できる。PTFE obtained by the method of the present invention is
As a foam, it is radiation-resistant and has a cross-linked structure, so it can be used as an industrial material in a radiation environment, which was previously impossible to use, and as a radiation-sterilizable medical device material. It becomes possible. Until now, PTF
Since the medical device made of E cannot be sterilized by radiation, it is based on steam or gas sterilization. However, radiation sterilization can be used from the viewpoint of sterilization certainty. In addition, since the obtained PTFE foam also has rubber properties, it can be expected that the properties as a heat insulating material, a sealing material, and a packing material for equipment requiring heat resistance and chemical resistance are remarkably improved.
【００１７】以下に実施例を挙げて本発明を具体的に説
明するが、本発明はこれらに制限されるものではない。Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.
【００１８】[0018]
【実施例１】厚さ１．０ｍｍの市販のＰＴＦＥシートを
真空中（０．０１トル以下）において、３４０℃に加熱
して、２ＭｅＶの電子線を１．０ｋＧｙ／ｓの線量率で
照射した。照射２００秒後（積算線量２００ｋＧｙ）
に、照射を終了し、ＰＴＦＥを室温まで冷却した。その
結果、厚さが約３ミリのＰＴＦＥ発泡体が得られた。Example 1 A commercially available PTFE sheet having a thickness of 1.0 mm was heated to 340 ° C. in a vacuum (0.01 Torr or less) and irradiated with an electron beam of 2 MeV at a dose rate of 1.0 kGy / s. . 200 seconds after irradiation (total dose 200 kGy)
Then, the irradiation was terminated, and the PTFE was cooled to room temperature. As a result, a PTFE foam having a thickness of about 3 mm was obtained.
【００１９】得られたＰＴＦＥ発泡体の重量は３％減少
していたが、ＰＴＦＥの架橋による結晶融点の低下は３
４０℃の一点設定温度で電子線を照射したときの変化と
ほぼ同一であった。Although the weight of the obtained PTFE foam was reduced by 3%, the decrease in the crystal melting point due to the cross-linking of PTFE was 3%.
The change was almost the same as when the electron beam was irradiated at a single set temperature of 40 ° C.
【００２０】[0020]
【実施例２】厚さ０．５ｍｍの市販のＰＴＦＥシート
を、実施例１と同じ条件で発泡させたところ、ＰＴＦＥ
発泡体は得られたが、多くの気泡は破壊されていた。こ
れは、照射で発生した分解ガスがＰＴＦＥの発泡を引き
起こすが、シートの厚さに比べて気泡のサイズが大きい
ためと考えられる。Example 2 A commercially available PTFE sheet having a thickness of 0.5 mm was foamed under the same conditions as in Example 1.
A foam was obtained, but many cells were broken. This is presumably because the decomposition gas generated by the irradiation causes the PTFE to foam, but the size of the bubbles is larger than the thickness of the sheet.
【００２１】[0021]
【実施例３】厚さ１．０ｍｍの市販のＰＴＦＥシート
を、１気圧（大気圧）のアルゴンガスを封入した照射容
器に入れ、ＰＴＦＥを３４０℃に加熱して、２ＭｅＶの
電子線を０．５ｋＧｙ／ｓの線量率で１０００秒間（積
算線量５００ｋＧｙ）照射した。照射終了後に、照射容
器内のアルゴンガスを徐々に脱気しつつ、ＰＴＦＥを室
温まで冷却したところ、厚さ約４ｍｍのＰＴＦＥ発泡体
が得られた。このＰＴＦＥ発泡体中の気泡の大きさは極
めて小さく、発泡体全体が白濁していた。このＰＴＦＥ
発泡体の重量減少は、それぞれ４％であった。Example 3 A commercially available PTFE sheet having a thickness of 1.0 mm was placed in an irradiation container filled with 1 atm (atmospheric pressure) of argon gas. Irradiation was performed at a dose rate of 5 kGy / s for 1000 seconds (integrated dose of 500 kGy). After the irradiation was completed, the PTFE was cooled to room temperature while gradually degassing the argon gas in the irradiation container, to obtain a PTFE foam having a thickness of about 4 mm. The size of the cells in the PTFE foam was extremely small, and the entire foam was clouded. This PTFE
The weight loss of the foam was 4% each.
【００２２】[0022]
【実施例４】厚さ１．０ｍｍの市販のＰＴＦＥシート
を、２気圧（大気圧の２倍）のヘリウムガスを封入した
照射容器に入れ、実施例３と同様の条件にてＰＴＦＥ発
泡体を得た。得られたＰＴＦＥ発泡体は厚さ約４．５ｍ
ｍであり、発泡体中の気泡は、実施例３で得られた発泡
体中の気泡よりも大きくなり、柔軟性に富んでいた。Example 4 A commercially available PTFE sheet having a thickness of 1.0 mm was placed in an irradiation container filled with helium gas at 2 atm (twice the atmospheric pressure), and a PTFE foam was formed under the same conditions as in Example 3. Obtained. The obtained PTFE foam has a thickness of about 4.5 m.
m, and the cells in the foam were larger than the cells in the foam obtained in Example 3 and were rich in flexibility.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 乙幡 和重 東京都新宿区高田馬場４丁目40番13号 株式会社レイテック内 (72)発明者 田畑 米穂 東京都中野区本町４−48−17、701号 (72)発明者 大島 明博 栃木県塩谷郡塩谷町道下822 (56)参考文献 特開 平７−118423（ＪＰ，Ａ) 特開 昭61−146522（ＪＰ，Ａ) 特開 昭61−266439（ＪＰ，Ａ) 特開 平６−116423（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C08J 7/00 - 7/18 C08J 9/02 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazushige Ohata 4-40-13 Takadanobaba, Shinjuku-ku, Tokyo Inside Ray-Tech Co., Ltd. (72) Yoneho Tabata 4-48-17, Honcho, Nakano-ku, Tokyo No. 701 (72) Inventor Akihiro Oshima 822 Michishita, Shioya-machi, Shioya-gun, Tochigi Prefecture (56) References JP-A-7-118423 (JP, A) JP-A-61-146522 (JP, A) JP-A-61- 266439 (JP, A) JP-A-6-116423 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) C08J 7 /00-7/18 C08J 9/02
Claims (2)
点以上の温度で酸素不存在下において０．５ｋＧｙ／ｓ
〜１００ｋＧｙ／ｓの線量率で電離性放射線を照射する
ことから成る、ポリテトラフルオロエチレン発泡体の製
造方法。1. A polytetrafluoroethylene having a temperature of 0.5 kGy / s in the absence of oxygen at a temperature equal to or higher than the crystal melting point.
A method for producing a polytetrafluoroethylene foam, comprising irradiating ionizing radiation at a dose rate of １００100 kGy / s.
以上の温度で酸素不存在下において０．５ｋＧｙ／ｓ〜
１００ｋＧｙ／ｓの線量率で電離性放射線を照射して得
られるポリテトラフルオロエチレン発泡体。2. A polytetrafluoroethylene having a temperature of 0.5 kGy / s or more in the absence of oxygen at a temperature not lower than the crystal melting point.
A polytetrafluoroethylene foam obtained by irradiating with ionizing radiation at a dose rate of 100 kGy / s.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26701893A JP3305068B2 (en) | 1993-10-26 | 1993-10-26 | Expanded polytetrafluoroethylene and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26701893A JP3305068B2 (en) | 1993-10-26 | 1993-10-26 | Expanded polytetrafluoroethylene and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07118424A JPH07118424A (en) | 1995-05-09 |
| JP3305068B2 true JP3305068B2 (en) | 2002-07-22 |
Family
ID=17438917
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26701893A Expired - Lifetime JP3305068B2 (en) | 1993-10-26 | 1993-10-26 | Expanded polytetrafluoroethylene and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3305068B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3317452B2 (en) * | 1992-10-05 | 2002-08-26 | 株式会社レイテック | Modified polytetrafluoroethylene and method for producing the same |
| JP3566805B2 (en) * | 1996-04-11 | 2004-09-15 | 日本原子力研究所 | Sliding member |
| US11826975B2 (en) * | 2016-08-16 | 2023-11-28 | Daikin Industries, Ltd. | Molded article and manufacturing method for molded article |
-
1993
- 1993-10-26 JP JP26701893A patent/JP3305068B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07118424A (en) | 1995-05-09 |
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