JP4812826B2 - Polytetrafluoroethylene resin fine powder or its extrusion - Google Patents
Polytetrafluoroethylene resin fine powder or its extrusion Download PDFInfo
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Description
本発明は、ガス分離膜、液体分離膜、液体の脱気或いは液体への気体の溶解を目的とする気液の隔膜、人工血管などの医療用材料等に利用される四フッ化エチレン樹脂ファインパウダー、或いはその押出成形品に関するものである。 The present invention relates to an ethylene tetrafluoride resin fine used for medical materials such as gas separation membranes, liquid separation membranes, gas-liquid diaphragms for the purpose of degassing liquids or dissolving gases in liquids, and artificial blood vessels. The present invention relates to powder or an extruded product thereof.
四弗化エチレン樹脂(以下、PTFEと略記)を素材とする多孔質体(フッ素樹脂多孔質体と称する)は、耐薬品性、耐熱性などの材質的に優れた特徴と、均一で微細な多孔質構造を持ち、従来から例えば、分離膜、人工血管、カテーテル、培養器等の多くの用途に利用されている。また撥水性であることを利用した、水系液体の脱気、或いは逆に水系液体への気体溶解隔膜としても用いられている。 A porous body made of tetrafluoroethylene resin (hereinafter abbreviated as PTFE) (referred to as a fluororesin porous body) has excellent material characteristics such as chemical resistance and heat resistance, and is uniform and fine. It has a porous structure and has been conventionally used in many applications such as separation membranes, artificial blood vessels, catheters, and incubators. It is also used as a degassing of aqueous liquids utilizing the water repellency, or conversely as a gas-dissolving diaphragm for aqueous liquids.
このフッ素樹脂多孔質体は、通常、原料となるPTFEファインパウダーに液状潤滑剤(助剤)を混合し、予備成型にて円筒状に押し固めた後、所定の形状にペースト押出し、この押出成形品を長軸方向に延伸して多孔化し、しかる後、焼成する方法により製造されている。多孔化は、延伸法以外にも、造孔剤混合後の造孔剤の抽出や、発泡剤による発泡などの方法があるが、多孔化の程度を表す気孔率やフィルター性能、或いは強度といった性能の面から先の延伸法が優れている。 This fluororesin porous body is usually prepared by mixing a liquid lubricant (auxiliary) with PTFE fine powder as a raw material, pressing it into a cylindrical shape by pre-molding, and extruding the paste into a predetermined shape. The product is manufactured by a method of stretching the product in the major axis direction to make it porous, and then firing it. In addition to the stretching method, there are methods such as extraction of a pore-forming agent after mixing with a pore-forming agent and foaming with a foaming agent, but porosity such as porosity, filter performance, or strength that represents the degree of porosity. From this aspect, the previous stretching method is excellent.
フッ素樹脂多孔質体は、各種用途に応じて、平均孔径、透過率、透過流量、強度などの特性が所望の水準にあることが求められる。これら特性のうちフィルターとしての性能を主に決めるのは、その多孔質内を透過する気体や液体の透過流量と濾過分別する粒子の大きさの限界値すなわち孔径である。この2つの特性は各々、多孔質に占める空気の割合である気孔率と、アルコール中での空気の透過開始圧力であるバブルポイントで代用されることが多い。尚、バブルポイントは毛細管現象を利用した方法であり、孔径が小さいほど毛細管現象が大きくなることからバブルポイントが高い方が孔は小さいことを表す。 The fluororesin porous body is required to have characteristics such as an average pore diameter, a transmittance, a permeation flow rate, and strength at desired levels according to various uses. Of these characteristics, the filter performance is mainly determined by the permeation flow rate of the gas or liquid that permeates the porous body and the limit value of the size of the particles to be separated by filtration, that is, the pore diameter. These two characteristics are often substituted by a porosity, which is the proportion of air in the porous body, and a bubble point, which is the permeation start pressure of air in alcohol. The bubble point is a method using a capillary phenomenon, and the smaller the hole diameter, the larger the capillary phenomenon. Therefore, the higher the bubble point, the smaller the hole.
通常、濾過の分別能力である孔径・バブルポイントが同じであれば、濾過の処理効率を示す気孔率は高い方が望ましい。ところが、フッ素樹脂多孔体の製造方法として、延伸することで孔をあけていく方法を採用すると、その延伸率を高くしていけば気孔率は高くなっていくが、同時に孔径も大きくなって、濾過性能は小さくなっていく。このように気孔率とバブルポイントとには相関関係があり、通常、気孔率が決まれば、バブルポイントも決まってしまう。
従って、小孔径で濾過性能が高いものは透過流量が小さく、透過流量を大きくするために、気孔率を大きくしようとすると孔径も大きくなって、濾過性能は小さくなってしまう。
そのため、例えば、半導体の高集積化に伴うより高い濾過性能をもつような孔径の小さなフィルターとして使用しようとすると、濾過処理能力が極めて小さいものしか得られず、実用化が困難であった。
Usually, if the pore size and bubble point, which are the separation ability of filtration, are the same, it is desirable that the porosity indicating the filtration processing efficiency is high. However, as a method for producing a fluororesin porous body, if a method of making holes by stretching is adopted, the porosity increases as the stretching rate increases, but at the same time the pore diameter increases, Filtration performance decreases. Thus, there is a correlation between the porosity and the bubble point. Normally, if the porosity is determined, the bubble point is also determined.
Therefore, those having a small pore diameter and high filtration performance have a small permeation flow rate, and in order to increase the permeation flow rate, an attempt to increase the porosity increases the pore diameter, resulting in a decrease in filtration performance.
Therefore, for example, if it is intended to be used as a filter having a small pore diameter so as to have a higher filtration performance associated with higher integration of semiconductors, only a filter having a very small filtration processing capacity can be obtained, and practical application is difficult.
このようにPTFE延伸多孔質体は、その製法上の問題から、延伸時の速度・温度条件の変更で、ある程度、孔径、気孔率の変更が可能なものの、基本的に孔径と気孔率の関係に自由度が小さい。もちろん多孔質体の孔の発生のメカニズムには延伸以外にも、後述するように押出時の圧力によるPTFE粒子同士の接続度合い、焼成時の加熱状況による焼成の度合いなども影響する。しかし、前者には後述のように限界値が存在し、後者は焼成が弱いとフィルターとしての性能は高いが強度や耐久性が損なわれるため多くの場合性能が下がっても完全に焼成する必要がある。
したがって、PTFEファインパウダーを原料としたPTFE多孔質体に於いて、より濾過性能がよく、かつ、処理効率も高いものは実現できなかった。
Thus, the PTFE stretched porous body is basically a relationship between the pore diameter and the porosity, although the pore diameter and porosity can be changed to some extent by changing the speed and temperature conditions during stretching due to problems in the production method. The degree of freedom is small. Of course, in addition to stretching, the pore generation mechanism of the porous body is influenced by the degree of connection between PTFE particles due to the pressure during extrusion and the degree of firing due to the heating condition during firing, as will be described later. However, there is a limit value in the former as described later, and the latter has high filter performance if the firing is weak, but the strength and durability are impaired. is there.
Therefore, a PTFE porous body made of PTFE fine powder as a raw material has not been able to be realized with better filtration performance and higher processing efficiency.
本発明の目的は、延伸に於いてPTFEファインパウダーがもつ特性を向上させて、濾過性能がよく、かつ、処理効率も高いフッ素樹脂多孔質体を提供することにある。 An object of the present invention is to provide a fluororesin porous body that improves the properties of PTFE fine powder in stretching, has good filtration performance, and has high processing efficiency.
本発明者は、この問題について鋭意研究を重ねた結果、フッ素樹脂多孔質体の製造工程に於ける延伸工程前の、原料パウダー段階のPTFEファインパウダー、或いは押出成形段階の押出成形品に、放射線を照射することで、バブルポイントと気孔率との間に相関関係があって、気孔率を大きくしようとするとバブルポイントが小さくなるといったPTFEファインパウダーの本来もつ欠点を改質し、これによって、濾過性能がよく、かつ、処理効率も高いフッ素樹脂多孔質体を得た。 As a result of intensive research on this problem, the present inventor has applied radiation to the PTFE fine powder at the raw material powder stage or the extruded product at the extrusion stage before the stretching process in the fluororesin porous body manufacturing process. , The bubble point and the porosity have a correlation, and when trying to increase the porosity, the bubble point becomes smaller and the inherent disadvantage of the PTFE fine powder is modified. A fluororesin porous body having good performance and high processing efficiency was obtained.
本発明によれば、PTFEファインパウダーの延伸性を制御することが可能であり、適当な放射線照射量を選ぶことによって同じ透過性でも、より高い濾過性能を持つフッ素樹脂多孔質体を得ることが可能となる。また、示差走査熱量計による溶融ピークの解析によってその性能を予め知ることが可能であり、工業的によく制御された生産が可能となる。これらの発明品の用途に特に制限は無いが、分離膜用途などに好適に用いることができる。 According to the present invention, it is possible to control the stretchability of PTFE fine powder, and it is possible to obtain a fluororesin porous body having higher filtration performance with the same permeability by selecting an appropriate radiation dose. It becomes possible. Further, the performance can be known in advance by analyzing the melting peak with a differential scanning calorimeter, and industrially well-controlled production becomes possible. Although there is no restriction | limiting in particular in the use of these invention goods, It can use suitably for a separation membrane use etc.
本発明のフッ素樹脂多孔質体は、例えば以下のような技術で製造することができる。まず、押出工程でPTFEファインパウダーと潤滑剤の混合ペーストをシート状やチューブ状に押出し、必要に応じて圧延し、次に延伸を行う。この工程で、押出で圧着された樹脂パウダー同士が延伸により離れて裂けるようにしてできた亀裂状の孔間に糸を引くように繊維が延伸方向に形成される。この後または同時に少なくともPTFEの融点327℃以上に加熱し、焼結することでフッ素樹脂多孔質体を得ることができる。 The fluororesin porous body of the present invention can be produced, for example, by the following technique. First, a mixed paste of PTFE fine powder and a lubricant is extruded into a sheet shape or a tube shape in an extrusion process, rolled as necessary, and then stretched. In this step, fibers are formed in the stretching direction so that yarns are pulled between crack-like holes formed such that the resin powders pressure-bonded by extrusion are torn apart by stretching. Thereafter or simultaneously, the fluororesin porous body can be obtained by heating to at least the melting point of PTFE of 327 ° C. or higher and sintering.
本発明では、上記の工程において、延伸工程前のいずれかの段階でPTFEファインパウダーに、重イオン線、アルファ線、ベータ線すなわち電子線、ガンマ線、X線、紫外線等の放射線を照射する。この線種については、重イオンなどの大きな粒子線ではPTFE分子に与える影響にムラができる点、X線や紫外線ではPTFE分子に与えるエネルギーが小さい点からあまり適さず、汎用性から考えると電子線やガンマ線の使用が望ましく、粉末や押出成形への均一な照射処理が出来る点から透過性の高いガンマ線が最も望ましい。 In the present invention, the PTFE fine powder is irradiated with radiation such as heavy ion rays, alpha rays, beta rays, that is, electron rays, gamma rays, X rays, ultraviolet rays, etc. at any stage before the stretching step in the above process. This line type is not very suitable because it can cause uneven effects on PTFE molecules with large particle beams such as heavy ions, and X-rays and ultraviolet rays have little energy to be applied to PTFE molecules. And gamma rays are desirable, and gamma rays with high permeability are most desirable from the viewpoint that uniform irradiation treatment to powder and extrusion molding is possible.
本発明における延伸前の放射線照射量は、一般的な高分子処理の放射線照射量と比較すると極めて微量な照射量とする必要がある。具体的には10Gy以上1000Gy未満であり、後述の延伸性を制御する観点から100Gyから500Gyの範囲であることが望ましい。 The irradiation dose before stretching in the present invention needs to be a very small amount compared with the irradiation dose of a general polymer treatment. Specifically, it is 10 Gy or more and less than 1000 Gy , and it is desirable that it is in the range of 100 Gy to 500 Gy from the viewpoint of controlling the stretchability described later.
本発明の機能について以下に述べる。PTFEファインパウダーの数百μmの二次粒子は、約0.2μm程度の大きさの一次粒子が集まってできており、この一次粒子の中では帯状の結晶が折り畳まれた状態で存在する。押出工程における流動によって粒子同士が擦れ合うことで形成される一次粒子間のコネクションは両粒子を接続させ、延伸時に粒子間が引き延ばされると一次粒子内の折り畳まれた結晶の帯がほどけて繊維状構造となる。すなわち延伸による多孔質構造は、このコネクション形成の量と折り畳み構造からの結晶の帯のつむぎだし具合の2つによって決定される。 The function of the present invention will be described below. The secondary particles of several hundred μm of the PTFE fine powder are formed by collecting primary particles having a size of about 0.2 μm, and in the primary particles, a band-like crystal is present in a folded state. The connection between the primary particles formed by particles rubbing by the flow in the extrusion process connects both particles, and when the particles are stretched during stretching, the folded crystal band in the primary particles unwinds and forms a fiber It becomes a structure. That is, the porous structure formed by stretching is determined by two factors, that is, the amount of connection formation and the degree of squeezing of the crystal band from the folded structure.
気孔率は延伸率と相関するため、同じ気孔率における孔の大きさは延伸前の押出成形品の単位長さあたりにどれだけたくさんの孔が発生するか、すなわち孔の発生密度と逆相関する。つまり延伸によって発生する孔が多ければ小さな孔がたくさん空き、孔の発生が少なければ1つ1つの孔は大きくなることになる。一般には押出圧が高いほどずり応力が粒子に多くかかりコネクションの形成量が多くなり、開孔密度が高くなる。 Since porosity correlates with stretch ratio, the size of holes at the same porosity is inversely correlated with how many holes are generated per unit length of the extruded product before stretching, that is, with the density of holes generated. . That is, if there are many holes generated by stretching, many small holes are available, and if there are few holes, each hole will be large. In general, the higher the extrusion pressure, the more shear stress is applied to the particles, the greater the amount of connections formed, and the higher the hole density.
従来の技術では押出圧を上げる方法として、押出助剤であるオイルの量を減少させる方法を用いてきた。しかし、発明者らの検討の結果ではコネクションの数は1粒子あたり2個、すなわち隣り合う粒子同士が手をつなぐ状態が限界でありそれ以上押出圧を高くしてもコネクション数は増加しないことがわかっている。 In the prior art, as a method of increasing the extrusion pressure, a method of reducing the amount of oil as an extrusion aid has been used. However, as a result of investigations by the inventors, the number of connections is 2 per particle, that is, the state where adjacent particles are in a state where hands are connected to each other is the limit, and even if the extrusion pressure is increased further, the number of connections may not increase. know.
前に述べたように、延伸による多孔質構造は、コネクション形成の量と折り畳み構造からの結晶の帯のつむぎだし具合によって決定される。本発明者らは限界があるコネクション形成量以外に多孔質構造を制御する方法について鋭意研究を重ねた結果、放射線照射によってPTFEファインパウダー粒子から繊維が発生できる長さを変化させることができることを発見した。すなわちPTFEファインパウダーに放射線を照射していくと一次粒子内の結晶の帯の折り畳み構造が部分的に破壊され糸のつむぎだされる量が短くなっていくのである。 As previously mentioned, the porous structure due to stretching is determined by the amount of connection formation and the extent of the banding of crystals from the folded structure. As a result of intensive studies on the method of controlling the porous structure other than the limited connection formation amount, the present inventors have found that the length of fibers that can be generated from PTFE fine powder particles can be changed by irradiation. did. That is, when the PTFE fine powder is irradiated with radiation, the folded structure of the crystal band in the primary particles is partially broken, and the amount of thread to be pulled out becomes shorter.
この現象は照射後の押出成型品の引張試験における照射量と伸びの関係で示すことが可能である。押出成形品の伸びは放射線の照射量に依存し、伸びの現象は照射量10Gyくらいから検出されはじめ、約1kGy以上の照射よってほとんど伸びなくなる。すなわち繊維形成能力を失い実質的に延伸できなくなる。この伸びの減少は押出前の原料パウダーへの照射と押出成形後の照射とで差はない。また引張強度は押出圧に相関するものの照射量とは相関しない。すなわち放射線照射は押出時のコネクション形成に影響するわけではなく、もっぱら粒子からの糸のつむぎだし、つまり結晶の帯の折り畳み構造の引き延ばしを阻害している。 This phenomenon can be shown by the relationship between the irradiation amount and the elongation in the tensile test of the extruded product after irradiation. The elongation of the extruded product depends on the radiation dose, and the phenomenon of elongation begins to be detected from a dose of about 10 Gy, and hardly becomes stretched by irradiation of about 1 kGy or more. That is, the fiber forming ability is lost and the film cannot be substantially stretched. This decrease in elongation is not different between irradiation of the raw material powder before extrusion and irradiation after extrusion. The tensile strength correlates with the extrusion pressure but does not correlate with the irradiation amount. In other words, irradiation does not affect the connection formation during extrusion, but exclusively inhibits the thread from the particles, that is, the stretching of the folded structure of the crystal band.
また本発明者らは、これらの現象が示差走査熱量計によるPTFEの吸熱カーブの観察で捕らえることができることを発見した。乳化重合から生成されるPTFEファインパウダーは他の重合方法からなるモールディングパウダーや一旦加熱した後のPTFEがもつ327℃より20℃も高い347℃に吸熱ピークを持つ。放射線照射はこの347℃の融点ピークを335℃付近に変化させることがわかった。 The present inventors have also found that these phenomena can be captured by observing the endothermic curve of PTFE with a differential scanning calorimeter. The PTFE fine powder produced from emulsion polymerization has an endothermic peak at 347 ° C., which is 20 ° C. higher than the 327 ° C. possessed by molding powders made by other polymerization methods and once heated PTFE. It was found that irradiation changed the melting point peak at 347 ° C. to around 335 ° C.
PTFEファインパウダーは、347℃のピークと335℃付近にショルダーをもつことが知られている。放射線をPTFEファインパウダーに照射していくと、10Gyくらいからこの335℃付近のショルダーに吸熱ピークが現れ始め、更に照射量を増加させると347℃のピークは減少していき逆に335℃のピークが大きくなっていく。
そして、約1kGy以上の照射では、もはや347℃のピークは検知できなくなる。(図2参照)
図2チャートAに示されたように、347℃のピークが検知できなくなった状態のPTFEからなる押出成型品は、引張試験をすると、伸びがほとんどなしで破断し、実際に延伸も不可能となる。
PTFE fine powder is known to have a peak at 347 ° C. and a shoulder near 335 ° C. When the PTFE fine powder is irradiated with radiation, an endothermic peak begins to appear in the shoulder near 335 ° C from about 10 Gy, and when the dose is increased further, the peak at 347 ° C decreases and conversely the peak at 335 ° C. Is getting bigger.
And with irradiation of about 1 kGy or more, the peak at 347 ° C. can no longer be detected. (See Figure 2)
As shown in FIG. 2 Chart A, an extruded product made of PTFE in a state where the peak at 347 ° C. cannot be detected is, when subjected to a tensile test, fractured with almost no elongation, and is actually impossible to stretch. Become.
すなわち、本発明の実現に際し、延伸の制御をうまく行うためには、放射線を照射したPTFEに、伸びが大きくなることを示す347℃ピークと、伸びが小さくなることを示す335℃ピークとの両方のピークが存在する必要があることになる。
尚、少なくとも前記の範囲の放射線照射では、結晶量の指標となる結晶融解に必要な熱量すなわち溶融潜熱は未照射の場合と差が認められず、上記に述べた伸びの減少等の現象が放射線によるPTFEの結晶破壊によるものでないことが示唆されている。
That is, in order to successfully control the stretching in realizing the present invention, both the 347 ° C. peak indicating that the elongation is increased and the 335 ° C. peak indicating that the elongation is reduced are applied to the PTFE irradiated with radiation. There will be a need to have a peak.
It should be noted that at least in the above-mentioned range of irradiation, the amount of heat necessary for crystal melting, which is an index of the amount of crystal, that is, the latent heat of fusion, is not different from the case of non-irradiation. It has been suggested that this is not due to PTFE crystal destruction.
この種の融点ピークの変化についての従来の技術としては、例えば特公昭58−145735公報や特許2533229号公報に開示されているPTFEファインパウダーの加熱処理がある。前者はファインパウダーのもつ338℃の融点ショルダーを無くして347℃の単ピークにする方法であり、後者は335℃の単ピークにすることを特徴としている。これらの方法と本発明との最大の違いは本発明の方法が前項で述べたように溶融潜熱の変化を伴わないことにある。すなわちPTFEファインパウダーを加熱処理して行う従来の方法は、結晶が加熱により多少なりとも融けることでその融点に変化を及ぼすため結晶量の変化は避けがたい。本発明の方法では例え特許2533229号公報に開示された方法によって得られた融熱ピークと同様の335℃の単ピークになるまで照射しても溶融潜熱、すなわち結晶の量にはほとんど変化がなく、結晶に及ぼすメカニズムにおいてこれらの加熱法とは別のものであると考えられる。 As a conventional technique for this kind of change in melting point peak, for example, there is a heat treatment of PTFE fine powder disclosed in Japanese Patent Publication No. 58-145735 and Japanese Patent No. 2533229. The former is a method in which the fine powder has a melting point shoulder of 338 ° C. and a single peak at 347 ° C., and the latter is characterized by a single peak at 335 ° C. The biggest difference between these methods and the present invention is that the method of the present invention does not involve a change in latent heat of fusion as described in the previous section. That is, in the conventional method in which PTFE fine powder is heat-treated, the crystal is melted to some extent by heating, and the melting point is changed, so that the change in the amount of crystals is unavoidable. In the method of the present invention, there is almost no change in the latent heat of fusion, that is, the amount of crystals, even if irradiation is performed until a single peak of 335 ° C. is obtained, which is similar to the fusion heat peak obtained by the method disclosed in Japanese Patent No. 2533229. It is considered that the heating mechanism is different from these heating methods.
本発明の技術の応用例について、気孔率を変えずに孔径を小さくする場合について具体的に説明する。通常の押出成型品は条件によって異なるが一般に1000%以上の延伸可能である。孔径を小さくしたい場合、延伸率を下げるが、例えば1軸延伸チューブの孔径0.1μ相当品では延伸率を100〜150%に押さえなければならない。未照射では1000%以上の延伸に対応できるため、初期に発生する孔は無理なくある程度大きくなり、次の孔の発生につながらない。すなわち開孔の密度はあまり上がらないことになる。 An application example of the technology of the present invention will be specifically described in the case of reducing the pore diameter without changing the porosity. Ordinary extruded products vary depending on conditions, but generally can be stretched by 1000% or more. When it is desired to reduce the pore diameter, the stretching ratio is lowered. However, for example, in the case of a uniaxially stretched tube having a pore diameter of 0.1 μm, the stretching ratio must be suppressed to 100 to 150%. Unirradiated can cope with stretching of 1000% or more, so that the holes generated in the initial stage become reasonably large to some extent and do not lead to the generation of the next hole. That is, the density of the holes does not increase so much.
これに対して延伸可能な量を制限された照射品の場合は、延伸率が低くても開孔した部分の繊維がそれ以上伸びずに他に開孔部分の発生が可能となり、結果として開孔密度の増加し、同じ延伸率すなわち気孔率でより孔径が小さなものを得ることが可能となる。 On the other hand, in the case of an irradiated product in which the amount that can be stretched is limited, even if the stretch rate is low, the fibers in the perforated portion do not extend any more and other perforated portions can be generated, resulting in the opening. It is possible to increase the pore density and obtain a material having a smaller pore diameter at the same stretch rate, that is, porosity.
本発明の技術は上記の例にあるチューブだけに限定されるものではなく、二軸延伸等より成形の自由度の高いシート状多孔質体やロッド状多孔質体にも応用可能である。またこの例以外にも、例えばガンマ線のような透過性の高い放射線ではなく、ごく表層にしか影響しない加速電圧の低い電子線などを利用することで押出成形体の表面のみに照射してから延伸することで照射部と内部或いは裏側の非照射部の孔径が違う多孔質体の作出などが可能となる。また押出成形体に金属製の網や模様、絵文字などのマスクをかけた状態で放射線照射することで前述の厚み方向でなく面方向に不均一な多孔質構造をもつ多孔質体を得ることも可能であり、染料を使用ないPTFE多孔質体へのマーキング等に利用できる。本発明の技術はPTFEの伸びのみを減少させ強度には影響しないために、様々な応用が考えられる。 The technique of the present invention is not limited to the tube in the above example, but can be applied to a sheet-like porous body or a rod-like porous body having a higher degree of freedom of molding than biaxial stretching or the like. In addition to this example, for example, an electron beam with a low accelerating voltage that only affects the surface layer is used instead of highly transmissive radiation such as gamma rays, and then the surface is irradiated and stretched. By doing so, it becomes possible to create a porous body in which the pore diameters of the irradiated part and the non-irradiated part inside or on the back side are different. It is also possible to obtain a porous body having a non-uniform porous structure not in the thickness direction but in the plane direction by irradiating the extruded molded body with a mask such as a metal net, pattern, or pictograph. It can be used for marking on a porous PTFE body that does not use a dye. Since the technique of the present invention reduces only the elongation of PTFE and does not affect the strength, various applications can be considered.
以下、本発明について、実施例および比較例を挙げて具体的に説明するが、本発明はこれらの実施例のみに限定されるものではない。 EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited only to these Examples.
PTFEファインパウダーは、旭アイシーアイフロロポリマーズ社製の四フッ化エチレン樹脂ファインパウダーCD−123を使用した。Co60を線源とするガンマ線を該パウダーに照射量100、300、500、1000、1500Gyの5種類の線量にて照射した。この各パウダーをソルベントナフサ22重量部を混合し、内径1.5mm外径2.7mmのチューブ状に押出成形した。さらに60℃乾燥炉にてナフサを除去し、乾燥押出品を得た。これらを実施例1〜3および参考例4、5とした。また未照射のパウダーを同様にして得た乾燥押出品を比較例1とした。 As the PTFE fine powder, tetrafluoroethylene resin fine powder CD-123 manufactured by Asahi IC Fluoropolymers Co., Ltd. was used. The powder was irradiated with gamma rays having Co60 as a radiation source at doses of 100, 300, 500, 1000 and 1500 Gy. Each powder was mixed with 22 parts by weight of solvent naphtha and extruded into a tube shape having an inner diameter of 1.5 mm and an outer diameter of 2.7 mm. Further, naphtha was removed in a 60 ° C. drying furnace to obtain a dry extruded product. These were designated as Examples 1 to 3 and Reference Examples 4 and 5 . A dry extrudate obtained by similarly obtaining unirradiated powder was used as Comparative Example 1.
さらに上記比較例1の未照射の乾燥押出品に、Co60を線源とするガンマ線を照射量300、500Gyの線量にて照射したものを参考例1、2とした。以上の実施例1〜3、参考例1、2、4、5および比較例1について、引張温度200℃、引張速度100mm/分、チャック間2.5cmにて引張試験を行った。結果を表1に示す。 Further, Reference Examples 1 and 2 were obtained by irradiating the unexposed dry extruded product of Comparative Example 1 above with gamma rays using Co60 as a radiation source at a dose of 300 Gy and 500 Gy. For the above Examples 1 to 3, Reference Examples 1, 2, 4, 5 and Comparative Example 1, a tensile test was performed at a tensile temperature of 200 ° C., a tensile speed of 100 mm / min, and a chuck distance of 2.5 cm. The results are shown in Table 1.
実施例1〜3および参考例1、2、4、5は、比較例1に対してガンマ線の照射量に応じて破断伸びの減少が見られた。降伏点強度については、照射によりパウダーの押出抵抗が下がって流動性が上がるために、同じ助剤配合部数で同じ形状に押し出すと押出圧が下がってしまうことによる。降伏点強度はパウダー粒子間に形成されるコネクションの量に依存するためコネクションを形成させるずり応力すなわち押出圧に依存する。逆に押出後に照射した実施例6、7ではあまり減少しない。 In Examples 1 to 3 and Reference Examples 1 , 2 , 4 , and 5 , a decrease in elongation at break was observed according to the irradiation amount of gamma rays compared to Comparative Example 1. With respect to the yield point strength, the extrusion resistance of the powder is lowered by irradiation and the fluidity is increased, so that the extrusion pressure is lowered when extruded in the same shape with the same number of auxiliary components. The yield point strength depends on the amount of connection formed between the powder particles, and therefore depends on the shear stress that forms the connection, that is, the extrusion pressure. On the contrary, in Examples 6 and 7 irradiated after extrusion, there is not much reduction.
さらに実施例1〜3、参考例1、2、4、5および比較例1について示差走査熱量計にて融点ピークの観察を行った。比較例1では347℃の1ピークであるのに対して、実施例1では照射量が増えるに連れて335℃のピークが徐々に大きくなるのが観察された。335℃のピークと347℃のピークの高さは実施例1と2の間で逆転し、347℃付近の吸収は参考例4ではわずかに残るのみで参考例5ではほとんど見られなくなった。 Further, with respect to Examples 1 to 3, Reference Examples 1, 2, 4, 5 and Comparative Example 1, the melting point peak was observed with a differential scanning calorimeter. In Comparative Example 1, there was one peak at 347 ° C., but in Example 1, it was observed that the peak at 335 ° C. gradually increased as the dose increased. The heights of the peak at 335 ° C. and the peak at 347 ° C. were reversed between Examples 1 and 2. Absorption around 347 ° C. remained only slightly in Reference Example 4 and almost disappeared in Reference Example 5 .
助剤部数を16.5部、ガンマ線照射量を500Gyとしたこと以外は実施例1〜3および参考例4、5と同様にして乾燥押出品を得た。これを炉長1m、炉温550℃の炉内で延伸率75%、巻取線速5.5m/分にて延伸後、同じ加熱炉で炉温600℃、巻取線速5m/分にて焼成した。この延伸多孔質チューブを実施例6とした。 Dry extrudates were obtained in the same manner as in Examples 1 to 3 and Reference Examples 4 and 5 except that the number of auxiliaries was 16.5 parts and the gamma ray irradiation amount was 500 Gy. This was stretched in a furnace with a furnace length of 1 m and a furnace temperature of 550 ° C. at a draw rate of 75% and a winding wire speed of 5.5 m / min, and then in the same heating furnace to a furnace temperature of 600 ° C. and a winding wire speed of 5 m / min. And fired. This stretched porous tube was taken as Example 6.
参考例1の乾燥押出品を使用し、延伸率を100%としたこと以外は実施例6と同様にして参考例3を得た。また、助剤部数21部数としたこと以外は比較例1と同様にして得た乾燥押出品を使用したこと以外は実施例6と同様にして比較例2とした。さらに比較例1の乾燥押出品を使用したこと以外は参考例1と同様にして比較例3とした。 Reference Example 3 was obtained in the same manner as in Example 6 except that the dried extruded product of Reference Example 1 was used and the stretch ratio was 100%. Moreover, it was set as the comparative example 2 like Example 6 except having used the dried extrusion product obtained by carrying out similarly to the comparative example 1 except having set it as 21 parts of adjuvant. Further, Comparative Example 3 was obtained in the same manner as Reference Example 1 except that the dried extruded product of Comparative Example 1 was used.
実施例6、参考例3および比較例2、3の製造条件およびその多孔質の特性について表2、図1に示す。 The production conditions of Example 6, Reference Example 3 and Comparative Examples 2 and 3 and the porous characteristics thereof are shown in Table 2 and FIG.
実施例6および比較例2は押出圧を合わせるために助剤部数を調整したもので、また参考例3と比較例3は同じ乾燥押出品を使用したものである。図1を見ると実施例は各々の対応する比較例に対してほぼ同じ気孔率で孔径が小さな特性をもつことがわかる。 In Example 6 and Comparative Example 2, the number of auxiliaries was adjusted in order to match the extrusion pressure, and Reference Example 3 and Comparative Example 3 used the same dry extruded product. Referring to FIG. 1, it can be seen that the example has a characteristic that the pore diameter is small with substantially the same porosity as each corresponding comparative example.
これは実施例使用した乾燥押出品が放射線照射により延伸性を制限されており、この延伸できる限界近い延伸を行っているためであると考えられる。表1を参考にすると未照射品は800%近く延伸できる。比較例2、3のような75〜100%延伸では、全ての孔が発生しきるまでに至っていなかった。これに対して実施例では75〜100%の延伸は延伸可能範囲の限界に近いものであり、小さな孔が無数に開孔していた。 This is presumably because the dried extrudates used in the examples have stretchability limited by radiation irradiation and are being stretched near the limit at which they can be stretched. Referring to Table 1, the unirradiated product can be stretched by nearly 800%. In the 75-100% stretching as in Comparative Examples 2 and 3, not all the holes were generated. On the other hand, in the examples, stretching of 75 to 100% was close to the limit of the stretchable range, and innumerable small holes were formed.
なお、以上に述べた実施例6、参考例3および比較例2、3は、いずれも示差走査熱量計による分析の結果、融点ピークは327〜329℃の範囲、溶融潜熱も25J/g以下と十分焼成されており、実施例と比較例の差は焼成の度合いの差によるものではないと見なされた。 In addition, in Example 6, Reference Example 3 and Comparative Examples 2 and 3 described above, as a result of analysis by a differential scanning calorimeter, the melting point peak was in the range of 327 to 329 ° C., and the latent heat of fusion was 25 J / g or less. It was considered that the difference between the examples and the comparative examples was not due to the difference in the degree of baking.
実施例1〜3、参考例1、2、4、5および比較例1の製造条件及び強度特性 Production conditions and strength characteristics of Examples 1 to 3, Reference Examples 1, 2, 4, 5 and Comparative Example 1
実施例6、参考例3および比較例2、3の製造条件と多孔質特性 Production conditions and porous properties of Example 6, Reference Example 3 and Comparative Examples 2 and 3
表中、BPはバブルポイント。ASTM−F−316−80の方法により、イソプロピルアルコールを用いて測定した。
In the table, BP is a bubble point. Measurement was performed using isopropyl alcohol by the method of ASTM-F-316-80.
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