JP7005867B2 - High-strength ultra-high molecular weight polyethylene molded product and its manufacturing method - Google Patents

Description

The present invention relates to a method for producing a high-strength molded body obtained by laminating an ultra-high molecular weight polyethylene stretched film and the molded body.

Ultra-high molecular weight polyethylene is polyethylene with a molecular weight of 1 million or more, and is a resin with excellent self-lubricating properties, wear resistance, dimensional stability, chemical resistance, etc., and covers a wide range of gears, gaskets, artificial joints, films, fibers, etc. Is being used. Among them, the stretched film has been used as a separator film for batteries in recent years, and its use is expected to increase in the future due to the widespread use of electric vehicles and tablet terminals. On the other hand, there is a demand for reuse of scraps and used films that are discarded in the process of producing a separator film.
However, ultra-high molecular weight polyethylene has poor fluidity, is not suitable for injection molding and extrusion molding, and is a material that is difficult to pelletize. Is not found at present. Further, in general, plastic is deteriorated by material recycling and its physical properties are deteriorated, so that the range of use of recycled material is limited as compared with virgin material.
On the other hand, it is known that the strength of plastic is increased by the orientation of molecules, and the same is true for ultra-high molecular weight polyethylene.
Conventionally, Patent Document 1 exists as a technique utilizing the orientation of ultra-high molecular weight polyethylene.
The technique of Patent Document 1 uses ultra-high molecular weight polyethylene for sliding parts and aligns the molecules by the shear flow of injection molding. However, since the oriented portion is limited to the shear layer of the resin molded body, molding is performed. The degree of body orientation is low, and the molecular orientation depends on the shape of the mold cavity.

Japanese Unexamined Patent Publication No. H06-218752

Molecules are similarly oriented in the stretched separator film and have excellent mechanical properties, but in the recycling process, when heated at a temperature higher than the melting point of ultra-high molecular weight polyethylene, they are integrated. Although a molded product can be obtained, it has a problem that the orientation is lost.
Therefore, the inventor of the present invention searched for a method of reusing the film body of ultra-high molecular weight polyethylene and repeated trial and error. Below, it was found that a molded body can be obtained by promoting fusion between the film bodies while maintaining the orientation. The molded product has excellent physical properties based on the orientation and characteristics such as a low coefficient of friction, and we have sought to develop a new application that makes the best use of its advantages.

The method for producing an ultra-high molecular weight polyethylene molded product according to claim 1 targets a) an ultra-high molecular weight polyethylene stretched film body having orientation, and b) orients the orientation in one direction and a direction different from that adjacent to the one. The films are sequentially laminated at different angles of combination, c) a polyethylene film is inserted between the film in one direction and the film in a different direction, and d) the molding temperature is in the range of 140 ° C to 163 ° C. It is characterized by e) pressurizing the molding pressure to 1 MPa to 30 MPa while heating, f) cooling to 70 ° C. or lower while maintaining the pressurized state, and g) obtaining an integrated molded body while maintaining the orientation. And.

The method for producing an ultra-high molecular weight polyethylene molded body according to claim 2 is characterized in that an angle formed by a film in one direction and a film in a different direction is 90 degrees.

The method for producing an ultra-high molecular weight polyethylene molded product according to claim 3 is characterized in that an angle formed by a film in one direction and a film in a different direction is 45 degrees.

In the molded product according to claim 4, the ultra-high molecular weight polyethylene stretched film body having orientation is sequentially laminated by changing the combined angle of the orientation in one direction and the adjacent and different directions. It is characterized in that a polyethylene film is inserted between the film in one direction and the film in a different direction to be integrated while maintaining the orientation.

In the present invention, fusion is promoted between the laminated ultra-high molecular weight polyethylene stretched films, and they are integrated with each other. At the same time, the orientation of the stretched film is maintained. This is confirmed from the images of the scanning electron microscope (SEM) and the high strength exhibited in the tensile test.
However, the fusion between the ultra-high molecular weight polyethylene stretched films is 140 ° C. or higher, a high tensile strength value is obtained at 163 ° C. or lower, and the integrated molded body having orientation at 139 ° C. or lower and 164 ° C. or higher is available. I can't get it. This is because the temperature required to promote molecular motion to some extent is required for fusion between the films, and the orientation of the ultra-high molecular weight polyethylene film is a factor of the high tensile strength. It is required that the temperature should be low enough to be maintained, and it is presumed that these are achieved in the range of 140 ° C to 163 ° C.
Further, the retention of the orientation is related to the molding pressure, and the orientation is obtained when the pressure is applied at a pressure of 1 to 30 MPa, which is also confirmed by a differential scanning calorimeter (DSC).
This orientation is promoted and maintained by the cooling step to 70 ° C. or lower.
The obtained molded product has the low friction property inherent in ultra-high molecular weight polyethylene on the surface, and high integration is obtained inside.
In principle, these effects are exhibited when the films are stacked with the orientation aligned in the same direction, but when the films are stacked with the orientation changed from one direction to a different direction. By inserting a low molecular weight polyethylene film between the films, fusion and orientation retention with each other are ensured.

It is a perspective view which shows the case where the orientation of a film is superposed in the same direction. It is a photographic view which observed the cross section of a molded body by SEM, (a) is a partial cross-sectional view, and (b) is a cross-sectional view in a state where a part thereof is enlarged. It is an X-ray-diffraction diagram of the molded product when it is molded at a molding temperature of 150 ° C. It is a DSC curve comparing the case where the forming pressure is not applied and the case where the forming pressure is applied. (A) is an overall view and (b) is a partially enlarged view. It is a perspective view of the aspect of laminating the films by changing the orientation direction, and shows the case where (a) is rotated 90 degrees and superposed, and (b) is rotated 45 degrees and superposed. It is a photographic view of the Charpy fracture surface of the molded body when the orientation is rotated by 90 degrees, and (a) is a partial cross-sectional view, and (b) is a cross-sectional view in a state where a part thereof is enlarged.

Ultra-high molecular weight polyethylene is polyethylene with a molecular weight of 1 million or more, and has excellent properties such as wear resistance, low friction resistance, and dimensional stability. It is used as a separator film.
The separator film for a battery is a film body stretched at a temperature of about 120 ° C. to 150 ° C., has a large number of holes, and has, for example, a thickness of 0.5 to 500 μm and a width of 500 mm ×. It has a form with a length of 10 m. In the present invention, a battery separator film having a thickness of 60 μm is used as a sample.
Ultra-high molecular weight polyethylene has extremely low fluidity and is not suitable for injection molding or extrusion molding, and it is difficult to pelletize it by extrusion molding. By cutting, etc., it becomes possible to process into gears, gaskets, etc.
Therefore, with respect to the reuse of the battery separator film, attention was paid to molding by compression molding of the film body.

The ultra-high molecular weight polyethylene used as the battery separator film is stretched to form a film body as described above, and has the property of having molecular orientation due to the stretching.
Molecular orientation refers to a state in which polyethylene molecular chains are lined up in the same direction to some extent with respect to the stretching direction of the film, and molecular orientation refers to its properties. The crystal structure of the ultra-high molecular weight polyethylene stretched film includes a stretched chain crystal and a folded chain crystal (lamella), and the stretched chain crystal is generated by stretching while leaving a part of the folded chain crystal, and this is the orientation. Is thought to give birth to.
This molecular orientation is an important characteristic that characterizes the molded product of the present invention, as will be described later.

In the present invention, the ultra-high molecular weight polyethylene films are arranged in a predetermined number of sheets in a state where the orientations are aligned in the same direction (see FIG. 1), and the films are compressed by a compression molding machine or the like.
It can be said that the orientation is the same as the direction in which the film is stretched when the ultra-high molecular weight polyethylene film is manufactured as described above.

We searched for various conditions that enable compression molding of ultra-high molecular weight polyethylene films laminated in the above arrangement.
First, regarding the temperature conditions, the molded product was molded at each point of 130 ° C., 140 ° C., 150 ° C., 160 ° C., and 170 ° C., and a tensile test, an X-ray diffraction measurement, a DSC measurement, and an SEM observation were performed.

試験方法：成形した厚さ２ｍｍの成形体から、打ち抜き型を用いてダンベル試験片を作成し、試験片はＪＩＳ Ｋ ６２５１のダンベル状５号形とした。引張試験はＪＩＳ Ｋ ７１６１－１に従い、島津製作所製オートグラフＡＧ－Ｍ１により行い、引張速度は１０ｍｍ／ｍｉｎで、引張方向は配向方向と平行とした。
この結果、１４０℃～１６０℃の間では、引張り強さが１８５ＭＰａ以上の高い値が得られたが、一方、１７０℃以上では２０ＭＰａと低い値となった。
なお、成形温度１３０℃では、試験片作製時に剥離が生じてしまい、引張試験実施不可であった。 When the molding pressure was 30 MPa, the values of the tensile strength when the molding temperature was 130 ° C. to 170 ° C. were measured, and Table 1 was obtained.

Test method: A dumbbell test piece was prepared from a molded body having a thickness of 2 mm using a punching die, and the test piece was a dumbbell-shaped No. 5 type of JIS K 6251. The tensile test was carried out according to JIS K 7161-1 by Shimadzu Autograph AG-M1, the tensile speed was 10 mm / min, and the tensile direction was parallel to the orientation direction.
As a result, a high tensile strength of 185 MPa or more was obtained between 140 ° C. and 160 ° C., while a low value of 20 MPa or more was obtained at 170 ° C. or higher.
At a molding temperature of 130 ° C., peeling occurred when the test piece was produced, and the tensile test could not be performed.

試験方法：４０ｍｍ×１５０ｍｍに切断した超高分子量ポリエチレンフィルムを２枚用意し、それらを重ね合わせた。鉄板２枚に重ね合わせたフィルムの４０ｍｍ×４０ｍｍ部分を挟み込み、その部分に対して加熱・加圧を行った。残りの４０ｍｍ×１１０ｍｍ部分には熱が加わらないようにした。成形温度を１３４℃～１４０℃とし、成形圧力を３０ＭＰａで加圧時間を１０分とした。試験片の４０ｍｍ×１１０ｍｍ部分をチャックし、島津製作所製オートグラフＡＧ－Ｍ１を用いて引張速度を１０ｍｍ／ｍｉｎで剥離試験を行った。
この結果、１４０℃においては剥離に対し３６Ｎという高い値を示したが、それ以下の１３８℃、１３６℃等では１８Ｎ以下の低い値となり、実用化には不適であることが明らかとなった。
なお、配向方向に対して垂直方向の引張試験を４０ｍｍ×１５０ｍｍに切断した超高分子量ポリエチレンフィルムについて実施したところ、最大荷重は２０Ｎであり、２０Ｎ以上を実用化に適していると判断した。 In order to find the lower limit, two films were fused and the peeling strength was determined. How the tensile load at the time of peeling changed in the range of the molding temperature of 140 ° C. or less was measured, and the results shown in Table 2 were obtained.

Test method: Two ultra-high molecular weight polyethylene films cut into 40 mm × 150 mm were prepared, and they were overlapped. A 40 mm × 40 mm portion of the film laminated on two iron plates was sandwiched, and the portion was heated and pressurized. Heat was not applied to the remaining 40 mm × 110 mm portion. The molding temperature was 134 ° C. to 140 ° C., the molding pressure was 30 MPa, and the pressurizing time was 10 minutes. A 40 mm × 110 mm portion of the test piece was chucked, and a peeling test was performed at a tensile speed of 10 mm / min using an autograph AG-M1 manufactured by Shimadzu Corporation.
As a result, it showed a high value of 36 N for peeling at 140 ° C., but a low value of 18 N or less at 138 ° C., 136 ° C. or the like, which was lower than that, and it became clear that it was not suitable for practical use.
When a tensile test in the direction perpendicular to the orientation direction was carried out on an ultra-high molecular weight polyethylene film cut into 40 mm × 150 mm, the maximum load was 20 N, and it was judged that 20 N or more was suitable for practical use.

試験方法：表１と同じ試験方法によった。
この結果、１６１℃及び１６３℃では２２３ＭＰａ以上の強い引張強さが得られたが、１６４℃以上となると２４ＭＰａ以下の低い値となり、成形時の温度は最高で１６３℃迄であり、それ以上では実用化に不適な値となった。
上記のことから、成形時の温度は、成形圧力を３０ＭＰａとしたとき、１４０～１６３℃の範囲で高い引張強さが得られることが確認された。 Next, in order to find the upper limit, how the tensile strength changes in the molding temperature range of 160 ° C. or higher was measured, and the results shown in Table 3 were obtained.

Test method: The same test method as in Table 1 was used.
As a result, strong tensile strength of 223 MPa or more was obtained at 161 ° C and 163 ° C, but it became a low value of 24 MPa or less at 164 ° C or higher, and the temperature at the time of molding was up to 163 ° C at the maximum, and above that. The value was unsuitable for practical use.
From the above, it was confirmed that a high tensile strength can be obtained in the range of 140 to 163 ° C. when the molding pressure is 30 MPa.

試験方法：表２と同じ試験方法によった。
１４５℃以上では、剥離時の平均荷重が２７Ｎ以上となり、融着の強さを示したが、１４０℃以下では１３Ｎ以下となり実用化に不適な値となった。 A test to the same effect as above was examined when the molding pressure was 10 MPa.
As a result, Table 4 was obtained.

Test method: The same test method as in Table 2 was used.
At 145 ° C or higher, the average load at the time of peeling was 27 N or higher, indicating the strength of fusion, but at 140 ° C or lower, it was 13 N or lower, which was unsuitable for practical use.

When a more desirable temperature was searched for in the range of the molding temperature of 140 ° C. to 163 ° C., 150 ° C. showed a very high value of 110N in the peeling test of Table 4 above, and was around 150 ± 3 ° C. It is considered that the optimum value exists in.

試験方法：表１と同じ試験方法によった。
この結果、１５５℃～１５７℃にあっては、１２６ＭＰａ以上の高い引張強さを示すが、１５８℃に至っては２８ＭＰａ以下の低い値となった。
上記を総合すると、成形圧力を１０ＭＰａ以上とした場合には、成形温度を１４５℃～１５７℃の範囲とすることが望ましいものとなった。 Next, the upper limit value when the molding pressure was set to 10 MPa was obtained, and the results shown in Table 5 were obtained.

Test method: The same test method as in Table 1 was used.
As a result, it showed a high tensile strength of 126 MPa or more at 155 ° C to 157 ° C, but a low value of 28 MPa or less at 158 ° C.
Overall, when the molding pressure is 10 MPa or more, it is desirable that the molding temperature is in the range of 145 ° C to 157 ° C.

試験方法：表１と同じ試験方法によった。
この結果、１０ＭＰａ以下であっても１ＭＰａ以上とすることで１９７ＭＰａ以上の引張強さを得ることができ、実用化に適したものとなった。
なお、０．５ＭＰａでは、成形時に配向方向に対して収縮が起こり、正常な成形体が得られなかった。
このことから、成形時の圧力条件は、１～３０ＭＰａの範囲で１９７ＭＰａ以上の高い引張強さが得られることが確認された。 Next, the pressurization conditions were examined.
As for the molding pressures of 30 MPa and 10 MPa, as shown in Tables 1 to 5 above, it was confirmed that a high tensile strength of 126 MPa or more can be obtained when the molding temperature is 140 ° C. to 163 ° C. in that range. ..
Therefore, how the tensile strength changes when the molding temperature is 150 ° C. and the molding pressure is 10 MPa or less is measured, and the results shown in Table 6 are obtained.

Test method: The same test method as in Table 1 was used.
As a result, even if it is 10 MPa or less, a tensile strength of 197 MPa or more can be obtained by setting it to 1 MPa or more, which is suitable for practical use.
At 0.5 MPa, shrinkage occurred in the orientation direction during molding, and a normal molded product could not be obtained.
From this, it was confirmed that a high tensile strength of 197 MPa or more can be obtained in the range of 1 to 30 MPa under the pressure condition at the time of molding.

The time required for heating and pressurizing varies depending on the number of ultra-high molecular weight polyethylene films according to the thickness of the target molded product, but when the thickness is 4 mm, the time required is 10 minutes. In the case of a thickness of 10 mm, it took 20 minutes.

Next, the process proceeds to cooling the heated and pressurized film, and the mold sandwiching the ultra-high molecular weight polyethylene film is cooled to bring the temperature to 70 ° C. or lower. The cooling rate is, for example, 10 ° C./min.
The molten crystalline polymer can be cooled to promote crystallization, and the heated and pressurized ultra-high molecular weight polyethylene film can be cooled to have orientation. In order to ensure this cooling sufficiently, the cooling temperature is set to 70 ° C. or lower, which is lower than the crystallization temperature.

Based on the above manufacturing method, the ultra-high molecular weight polyethylene film bodies used as the separator film of the battery are laminated so as to have the same orientation direction, and fused to obtain an integrated molded body.

The above described the case where the ultra-high molecular weight polyethylene stretched film body having orientation is targeted and the films are overlapped with the orientation aligned in the same direction (see FIG. 1), but then the orientation is set to one direction. A case was examined in which the films were sequentially laminated by changing the angle at which the orientations were combined in adjacent and different directions (see FIG. 5).
Then, in this case, the fusion force at the film interface was weak and the film was easily peeled off.
Therefore, it was examined to insert a relatively low amount of polyethylene film between the films and to fuse it under the same conditions as described above.
Here, the low molecular weight polyethylene means a polyethylene having a molecular weight capable of forming a normal film, and refers to a molecular weight of tens of thousands to hundreds of thousands, but specifically, the MFR value is 0.3 to 7 g / 10 min. Refers to polyethylene.
Specifically, for example, a film having a right angle of 90 degrees to each other and being repeatedly overlapped at right angles and parallel to one film (FIG. 5A), and a film having one orientation. On the other hand, an angle of 90 degrees or less, for example, a case where the angle is rotated by 45 degrees, which is a 1/2 right angle (FIG. 5 (B)), is examined.

試験方法：表１と同じ試験方法によった。
この結果、回転角度を９０度とした場合には、引張強さは１３８ＭＰａで、４５度とした場合には、１０６ＭＰａと共に高い引張強さが発揮された。
従って、配向を同一方向に揃えてフィルムを重ね合わせた場合に比べ、配向を異なる方向に組み合わせそこにより低分子量のポリエチレンフィルムを介在させた場合には、多角的であり、一方向の引張強さが若干落ちるものの、１００ＭＰａ以上の引張強さを得ることができ、充分実用性に耐え得ることが確認された。 As a result, in the tensile test, a strong tensile strength was obtained as shown in Table 7.

Test method: The same test method as in Table 1 was used.
As a result, when the rotation angle was 90 degrees, the tensile strength was 138 MPa, and when it was 45 degrees, a high tensile strength was exhibited together with 106 MPa.
Therefore, compared to the case where the orientations are aligned in the same direction and the films are overlapped, when the orientations are combined in different directions and a low molecular weight polyethylene film is interposed there, the orientation is diversified and the tensile strength in one direction is high. However, it was confirmed that a tensile strength of 100 MPa or more could be obtained and that it could sufficiently withstand practicality.

Thus, the ultra-high molecular weight polyethylene stretched film body having the orientation is sequentially laminated by changing the combined angle of the orientation in one direction and the direction different from that adjacent to the one direction, and the film is sequentially laminated in the one direction. A low molecular weight polyethylene film shall be inserted between the film and the film in a different direction. Then, while heating at a molding temperature of 140 ° C. to 163 ° C., the molding pressure is pressurized at 1 MPa to 30 MPa, and cooling is performed at 70 ° C. or lower while maintaining the pressurized state, which is the same as the above.

In addition, the mode of superimposing the film bodies by changing the angle between one direction and a different direction is as follows: a) when each film is changed one by one, and b) a film in which the above orientations are aligned in the same direction. In the case of b), a low-molecular-weight polyethylene film shall be inserted between each unit.
The difference in this aspect is determined by the shape and thickness of the desired molded product.

Based on the above manufacturing method, a molded product characterized by laminating ultra-high molecular weight polyethylene stretched films having orientation in the same direction and integrating them by fusion can be obtained. It becomes a thing.
Further, the ultra-high molecular weight polyethylene stretched film body having the orientation is sequentially laminated by changing the combined angle of the orientation in one direction and the direction different from that adjacent to the one direction, and the film in the one direction. A molded product is obtained by inserting a low molecular weight polyethylene film between the film and the film in a different direction.

The action and effect of the present invention will be described.
In the present invention, it is presumed that fusion occurs between the laminated ultra-high molecular weight polyethylene films.
It can also be seen from the scanning electron microscope (SEM) observation image.
The images shown in FIGS. 2A and 2B are SEM images obtained by observing the cut surface of the molded product with JSM-6510LA manufactured by JEOL Ltd., and the cut surface is smooth and no peeling is observed. It shows that the films are fused together.

The portion A in the center of the image shown in FIG. 2A is a portion in which a cut is made in the cut surface of the molded body and pulled in the orientation direction to be peeled off. Here, a linear structure is seen parallel to the orientation direction, and in an enlarged view of FIG. 2 (b), a fibril extending perpendicular to the linear structure is observed.
That is, the existence of a molecular structure oriented from this linear structure can be seen. It also closely resembles the shish kebab structure, where the fibril is expected to be a transcrystal for oriented molecules, which is expected to contribute to facilitating fusion between films.

On the other hand, when certain conditions are not met, for example, when the molding temperature exceeds 164 ° C., a phenomenon occurs in which the tensile strength drops to 24 MPa or less. It is considered that the fusion in the present invention is not limited to mere molecular diffusion due to heat, but other factors also work, and this is due to the presence or absence of orientation existing in the film of ultra-high molecular weight polyethylene by the present invention. I guessed it wasn't.
The orientation in the present invention refers to the property that ultra-high molecular weight polyethylene molecular chains or crystals are arranged in the stretching direction.
Therefore, in addition to the above SEM observation, X-ray diffraction measurement and DSC measurement were attempted.

When the molding temperature of the ultra-high molecular weight polyethylene film was set to 150 ° C. and the molding pressure was set to 10 MPa, X-ray diffraction measurement was performed by RINT RAPID-S manufactured by Rigaku Co., Ltd., and an image as shown in FIG. 3 was obtained. Was done. Diffraction spots were observed on the equatorial line of the dividing, suggesting the existence of orientation.

Then, the measurement by DSC was performed.
The DSC measures heat absorption and heat generation due to state changes, and grasps the phase transition, crystallization, etc. of the structure. A DSC7020 manufactured by Hitachi High-Tech Science Co., Ltd. was used, and an aluminum container was used for the measurement.
As a result, as shown in FIG. 4A, in the case of the sample in which the film was heated in a non-pressurized state, only the endothermic peak derived from the melting of the folded chain crystals of the ultra-high molecular weight polyethylene was observed, whereas the molding temperature was formed. In the sample at 150 ° C. and the molding pressure of 10 MPa, an endothermic peak which seems to be derived from the melting of the stretched chain crystals was observed.
That is, in FIG. 4 (b), which is a part thereof enlarged, the graph of the molded product pressurized to 10 MPa at 150 ° C. shows endothermic peaks indicating melting of the stretched chain crystal at the two points indicated by the arrows. On the other hand, this was not seen in the one heated without pressurization.
From this, it was confirmed that the ultra-high molecular weight polyethylene film molded under pressure conditions showed orientation within a certain molding temperature range.

The above was the case of a film in which the orientations were aligned in the same direction, but the orientation was changed between one direction and a different direction for the purpose of forming a high-strength molded product in multiple directions. The molded body was molded. An image as shown in FIG. 6 was obtained by SEM observation of the impact fracture surface of this molded product. FIG. 6A shows a case where the parts are different from each other by 90 degrees, and the part in one direction (the part A in the figure) and the part different in the orthogonal direction (90 degrees) (the part B in the figure) are. It is firmly integrated. Further, in FIG. 6B, which is an enlarged view of FIG. 6A, parts C and D, which are polyethylene films, are observed between parts A and B, and parts A and B thereof are observed. The interface with and was in close contact, and good adhesion was confirmed.

試験方法：圧子を３／８インチのアルミナとし、荷重を２００ｇとして測定した。
この結果、成形後の超高分子量ポリエチレンにおいてもバージン材から成形した成形体と同等の低い摩擦係数であることが確認され、超高分子量ポリエチレンの特徴である低摩擦が求められる用途に広く展開が可能となる。 Next, the friction characteristics, impact resistance, and the like of the molded product obtained in the present invention were measured.
That is, one of the major features of ultra-high molecular weight polyethylene is its low friction, which also affects the development of applications.
Therefore, the friction coefficient of the molded body after molding the ultra-high molecular weight polyethylene film under the above conditions was measured by a friction / wear tester (reciprocating friction / wear tester (HEIDON-18L manufactured by Shinto Kagaku Co., Ltd.)). , The results shown in Table 8 were obtained.

Test method: The indenter was 3/8 inch alumina, and the load was 200 g.
As a result, it was confirmed that the ultra-high molecular weight polyethylene after molding has a low friction coefficient equivalent to that of the molded product molded from the virgin material, and it is widely deployed in applications that require low friction, which is a characteristic of ultra high molecular weight polyethylene. It will be possible.

試験方法：ＪＩＳ Ｋ ７１１１－１により、シングルノッチ試験片に対し、エッジワイズ衝撃試験を行った。ハンマーは７．５Ｊ及び４Ｊを用いた。同一方向の成形体においては、配向方向に対して垂直方向の衝撃とした。
この結果、配向が同一方向の成形体の場合には、５７．１ｋＪ／ｍ^２、配向を９０度回転させた場合には４９．０ｋＪ／ｍ^２の衝撃強さとなり、４５度の場合には、破壊しなかった。
従って、配向の回転角度を制御することで、高い耐衝撃性を示すことが証明されたものである。 Next, while ultra-high molecular weight polyethylene is a material having excellent impact resistance, there is a concern that the impact strength is inferior to the oriented molded body. Therefore, a Charpy impact test was conducted. The results are as shown in Table 9.

Test method: An edgewise impact test was performed on a single notch test piece according to JIS K 711-1. Hammers used were 7.5J and 4J. In the molded product in the same direction, the impact was applied in the direction perpendicular to the orientation direction.
As a result, the impact strength is 57.1 kJ / m ² when the orientation is the same direction, 49.0 kJ / m ² when the orientation is rotated 90 degrees, and 45 degrees. , Did not destroy.
Therefore, it has been proved that high impact resistance is exhibited by controlling the rotation angle of orientation.

The above has been described by taking an ultra-high molecular weight polyethylene film for a battery separator as an example, but the present invention is not limited to this, and a wide range of objects made of an ultra-high molecular weight polyethylene stretched film body having orientation are broadly targeted. Can be done.

The reason why the above-mentioned excellent effect of the present invention can be obtained is not yet clear in detail, but it is presumed as follows.
When ultra-high molecular weight polyethylene films are laminated and heated, the crystals melt and fuse with each other when the temperature exceeds the melting point, but in principle, the orientation created by stretching disappears.
However, according to the study of the present inventor, the molecular orientation should be in the same direction, the molding temperature should be in the range of 140 ° C to 163 ° C, the molding pressure should be 1 to 30 MPa, and the cooling should be 70 ° C or less. It was confirmed that an exception was made.
First, when ultra-high molecular weight polyethylene is stretched into a film, polymer chains and crystals are arranged in the same direction as the stretching direction.
When ultra-high molecular weight polyethylene is laminated in the same direction as the orientation and heated above the melting point under pressure, the crystals melt, but the ultra-high molecular weight polyethylene has many entanglement points in the amorphous part and the folded part of the crystal. As a result, the molecular motion is inhibited, so that the orientation is maintained in the range of 140 ° C. to 163 ° C., which is close to the melting point, without causing a large change in the mutual position of the molecules in a certain range.
Further, the orientation is maintained by applying pressure to the one that loses its orientation without pressurization. This is because when pressure is applied to the molding process, molecular motion is suppressed and orientation relaxation is suppressed, and as a result, the position of large molecules does not change even in the molten state, and the molecular orientation of the ultra-high molecular weight polyethylene film. Etc. will not change significantly.
On the other hand, when the ultra-high molecular weight polyethylene film is laminated in the same direction as the orientation, molecular chains and crystals having the same orientation are lined up at the interface with each other, facilitating fusion and facilitating fusion, and strong tensile strength in the same direction. It will demonstrate its physical properties.
Then, when the ultra-high molecular weight polyethylene film in this state is cooled, the molecules in the state where the molecular orientation is maintained are crystallized as crystal nuclei.
On the other hand, if the ultra-high molecular weight polyethylene film is not laminated in the same direction as the orientation and is combined by changing the orientation angle between one direction and a different direction, a deviation occurs in the crystal direction. The fusion becomes incomplete. Therefore, when a low molecular weight polyethylene film is sandwiched between the two films, the lower molecular weight polyethylene is interposed between the upper and lower films whose crystal directions are deviated. Compared with ultra-high molecular weight polyethylene, this low molecular weight polyethylene has fewer entanglement points with molecules, and when heated above the melting point, molecular motion becomes active and the molecules can take a free form. When this is cooled, crystals are formed between the ultra-high molecular weight polyethylene films in a form suitable for each molecular orientation, or the low molecular weight polyethylene chains are solidified in a state of being entangled with the ultra-high molecular weight polyethylene chains. , The films are bonded to each other. Moreover, it does not hinder the maintenance of the orientation of the ultra-high molecular weight polyethylene, and mechanical strength such as tensile strength is exhibited.
Thus, it is presumed that a molded body integrated by fusion while maintaining the orientation of the stretched ultra-high molecular weight polyethylene film can be obtained.

The molded product of the present invention can be made into a molded product by compression molding with a mold, or if necessary, the molded product with a mold can be processed into a required shape by cutting or the like. , Gears, gaskets, artificial joints, cups, liners, balls, stems, vehicle floor materials, etc.

Claims (4)

a) Targeting ultra-high molecular weight polyethylene stretched film with orientation
b) The films are sequentially laminated by changing the combined angle of the orientation in one direction and the adjacent and different directions.
c) Insert a polyethylene film between the film in one direction and the film in a different direction.
d) While heating the molding temperature to the range of 140 ° C to 163 ° C,
e) Pressurize with a molding pressure of 1 MPa to 30 MPa.
f) Cool to 70 ° C or lower while maintaining the pressurized state,
g) Obtain an integrated molded product while maintaining the orientation.
A method for producing an ultra-high molecular weight polyethylene molded product. The method for producing an ultra-high molecular weight polyethylene molded product according to claim 1, wherein the angle formed by the film in one direction and the film in a different direction is 90 degrees. The method for producing an ultra-high molecular weight polyethylene molded product according to claim 1, wherein the angle formed by the film in one direction and the film in a different direction is 45 degrees. The ultra-high molecular weight polyethylene stretched film body having orientation is sequentially laminated by changing the combined angle of the orientation in one direction and the direction different from that adjacent to it, and the film in one direction and the film in one direction are overlapped with each other. A molded product characterized in that a polyethylene film is inserted between films in different directions and integrated while maintaining orientation.

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