JPH0651816B2 - Method for producing sheet or film comprising ultrahigh molecular weight polyethylene composition - Google Patents

Description

The present invention relates to a method for producing a sheet or film made of an ultrahigh molecular weight polyethylene composition, which comprises forming the ultrahigh molecular weight polyethylene into a thin sheet, film or tape form on an industrial scale. To a manufacturing method suitable for. Ultra-high molecular weight polyethylene is used for mechanical parts such as gears, pulleys and sprockets, and various linings because it has good physical properties such as wear resistance and excellent mechanical strength. . However, since the molecular weight is high, the melt viscosity is high, so the molding method is limited, and compression molding, extrusion molding using a special molding machine, injection molding are carried out, but most are limited to compression molding. However, the molding time may require several hours per time. Even if extrusion molding is performed, for example, 1 mm
When trying to make the following sheets, a high pressure is required to pass through the forming die, and even if the die has a high pressure, so-called melt fracture occurs at the time of outflow, and a uniform sheet cannot be obtained. . Furthermore, even if an attempt is made to obtain a film, tape or monofilament by stretching, the stretchability thereof is worse than that of ordinary polyethylene, and the desired product cannot be obtained at present. For these reasons, despite its excellent performance, the range and amount of use of ultra high molecular weight polyethylene is limited.

Conventionally, in order to improve the moldability of the above-mentioned ultra-high molecular weight polyethylene, for example, Japanese Patent Publications No. 43-24252 and 44-
In 27413, it has been proposed to add some kind of flow improver to improve moldability, but from the consideration of not impairing the inherent performance of ultra high molecular weight polyethylene, the upper limit of its addition amount is 5 ppm. However, the improvement in moldability was not fully satisfactory. In addition, JP-A-57-1773035, 57-172942, 57-19
Although a method of adding up to about 40% by weight has been proposed in 3319, even this method can shorten the molding time in the conventional method of molding ultrahigh molecular weight polyethylene a little, but it falls into the range of conventional methods. I will end up.

In view of the above situation, the present inventors have earnestly studied and, as a result, have widely changed the molding machine for sheets, films, tapes and the like which have been conventionally used for conventional polyethylene, and the conventional industrial scale. The inventors have found the ultra-high molecular weight polyethylene composition of the present invention capable of obtaining a sheet, film, or tape-shaped molded article that cannot be obtained at high speed with high productivity, and arrived at the present invention.

The gist of the present invention is (A) 0.5 to 55% by weight of polyethylene having a viscosity average molecular weight of 400,000 or more, and (B) 15 carbon atoms.
An ultrahigh molecular weight polyethylene composition obtained by uniformly mixing 99.5 to 45% by weight of a flow improver having a melting point lower than that of polyethylene, which is a solid at room temperature selected from the above alcohols, ethers, ketones or esters, into a sheet or film. A method for producing an ultrahigh molecular weight polyethylene sheet or film, which comprises molding, and extracting the component (B) with lower alcohol or water or a mixture of lower alcohol and water during or after the molding.

The features of the present invention are summarized as follows. That is, since it is a flow-improving agent of component (B) that contains a large amount of ultra high molecular weight polyethylene, it can be formed into a film at a high speed by an ordinary molding method.
It can be formed into a sheet or tape.

As in the case of the component (B), it is possible to stretch at a high magnification.

The component (B) can usually be easily extracted with a lower alcohol.

As can be seen from the above, by using the composition of the present invention, films, sheets and tapes of ultra-high molecular weight polyethylene, which have hitherto been impossible, can be obtained economically on an industrial scale.

The present invention will be described in detail below.

The ultrahigh molecular weight polyethylene (component (A)) used in the production method of the present invention means polyethylene having a viscosity average molecular weight of 400,000 or more.

Ultra-high-molecular-weight polyethylene is polymerized using the same catalysts as those used for producing ordinary polyethylene, such as Mg-Ti catalysts and cocatalysts such as organoaluminum compounds.
The molecular weight modifier, for example, H _2, is used in an extremely large amount by using a very small amount as compared with the amount used in the ordinary polymerization of polyethylene. As the copolymerization component, an α-olefin other than ethylene, etc. may be used in an appropriate amount as in the case of ordinary polyethylene.

The molecular weight of ultra high molecular weight polyethylene was measured by using tetralin at 130 ° C. as a solvent, measuring the intrinsic viscosity [η], and calculating from the following equation.

[Η] = KM ^a = 4.60 × 10 ⁻⁴ × M ^0.725 (wherein K and a are constants and M is a molecular weight). Ultrahigh molecular weight polyethylene is used as the component (B) used as a flow improver. The compatibility is good, especially in the melted state, the melting point is lower than that of ultra-high-molecular-weight polyethylene because it is uniformly mixed, the stretchability is improved, and the melting of ultra-high-molecular-weight polyethylene is promoted. Swelling or wetting the film,
It is necessary to satisfy the requirements that it is solid at room temperature and that it is soluble in a lower alcohol, which is a solvent that is easy to handle, because it is easy to handle after being processed into a sheet, tape or the like.

As the component (B), as the number of carbon atoms increases, the compatibility with the ultra-high molecular weight polyethylene becomes better, so that a carbon number of 15 or more is desired to sufficiently swell or wet the ultra-high molecular weight polyethylene. Further, when the number of carbon atoms is 15 or less, it is liquid at room temperature, and it is not preferable in that the component (B) easily bleeds when formed into a stretch-molded product.

Specific examples of the component (B) satisfying the above requirements include cetyl alcohol (CH ₃ (CH ₂ ) ₁₄ CH ₂ OH), heptadecyl alcohol (CH ₃ (CH ₂ ) ₁₅ CH ₂ OH), and stearyl alcohol (CH ₃ ). (CH ₂ ) ₁₆ CH ₂ OH),
Ceryl alcohol (CH ₃ (CH ₂ ) ₂₄ CH ₂ OH),
Behenyl alcohol (CH ₃ (CH ₂ ) ₇ C≡C (CH
₂ ) ₁₁ CH ₂ OH) and other alcohols; dioctyl ether ((C ₈ H ₁₇ ) ₂ O), didecyl ether ((C ₁₀
H _{21) 2} O), didodecyl ether ((C ₁₂ H _25)
2 O), dioctadecyl ether ((C ₁₈ H ₃₇ ) ₂ O)
Ethers such as methyl tetradecyl ketone (CH ₃ C
_{O (CH 2) 13 CH 3} ), n- propyl hexadecyl ketone _{(CH 3 (CH 2) CO} (CH 2) 15 CH 3), didodecyl ketone _{(CH 3 (CH 2) 11} CO (CH 2) 11
CH ₃ ), dioctadecyl ketone (CH ₃ (CH ₂ ) ₁₇
Ketones such as CO (CH ₂ ) ₁₇ CH ₃ ); octyl laurate (CH ₃ (CH ₂ ) ₁₀ COO (CH ₂ ) ₇ C
O ₃ ), ethyl palmitate (CH ₃ (CH ₂ ) ₁₄ CO
OCH ₂ CH ₃ , butyl stearate (CH ₃ (CH
₂ ) ₁₆ COO (CH ₂ ) ₃ CH ₃ ), octyl stearate (CH ₃ (CH ₂ ) ₁₆ COO (CH ₂ ) ₇ CH ₃ ).
And the like.

The composition ratio of the components (A) and (B) is (A) :( B) = 0.5.
˜55: 99.5 to 45 (wt%), more preferably (A) :( B) = 1 to 40: 99˜.
66 (wt%).

As a method for uniformly mixing both components (A) and (B),
A known kneading machine such as a twin-screw extruder, a Brabender kneader, or a Banbury mixer can be used, but after mixing both components (A) and (B) with powder in advance, 150-
By allowing the component (B) to swell the component (A) after leaving it at 180 ° C. and supplying it to the above mixer, uniform mixing of both components can be efficiently achieved. In this uniform mixing, if the weight of the component (A) exceeds 55% by weight, it becomes difficult to perform uniform mixing with the above-mentioned ordinary kneader.

At this time, if the kneading time is short, the ultra-high molecular weight polyethylene will not be sufficiently dissolved, and if kneading is added for a long time in order to make it uniform, the temperature will rise abnormally due to heat generation and a high shearing force will be applied. However, the molecular weight of ultra high molecular weight polyethylene is greatly reduced.

The kneading time varies depending on the ratio of the components (A) and (B), but is usually preferably several minutes to 20 minutes.

The necessity of uniform mixing is mainly due to the following two points.
That is, first, for example, when both components (A) and (B) are simply powder blended and supplied to a single-screw extruder which is usually used for molding, only the component (B) having a low melting point is dissolved first, so that the inside of the extruder is melted. Since slippage occurs, the shearing force is not applied to the ultra high molecular weight polyethylene itself and the melting is incomplete, so that the composition may be extruded intermittently or, in a worse case, it may be clogged to make extrusion impossible. .

Secondly, if the composition is non-uniform, the flow in the die or the like will not be constant, and it will be difficult to obtain, for example, a uniform thin sheet having a thickness of 1 mm or less.

Here, in order to carry out more uniform molding, it is desirable to supply the homogeneous mixture, which has been mixed by the kneading machine, to the extruder in a molten state without solidifying. The reason for this is that once it is cooled and solidified, some phase separation occurs, which results in (A) in the above-mentioned single-screw extruder feeding section.
(B) It is considered that both components are not melted uniformly.

As a method for processing the composition obtained as described above into a sheet or film, a molding method similar to that of ordinary polyethylene is adopted because the component (B) has sufficiently improved fluidity. Can be done. As a specific example, T-die
Examples include roll and blown film molding methods. The sheet or film thus obtained has the component (B) and thus has very good stretchability, so that it can be uniaxially or biaxially stretched at a higher magnification, and is extremely thin and strong. It is possible to get the goods.

In the present invention, the component (B) is extracted during or after the above molding. By doing so, the molded product such as the film or sheet after extraction will be composed of only ultra-high molecular weight polyethylene, and the molded product will have excellent physical properties.
The component (B) is extracted with lower alcohols such as methanol, ethanol, butanol or water or a mixture of water and alcohol in view of easiness of handling in the process, for example, drying of the film. Especially 100 μm
The following films can be performed at a high speed of a few minutes or less if conditions are selected. Further, a known heat stabilizer, ultraviolet stabilizer or the like may be appropriately added as the third component of the present composition.

As described above, the use of the composition of the present invention provides high productivity on an industrial scale, and particularly provides a thin ultra-high molecular weight polyethylene sheet or a film of about several μm which cannot be obtained by the conventional method. I can do things.

Next, in order to clarify the effect of the present invention, examples will be shown, but the present invention is not limited to these examples unless the gist thereof is exceeded.

Reference Example 1 (Production of Ultra High Molecular Weight Polyethylene Composition) Ultra high molecular weight polyethylene 4 having a viscosity average molecular weight of 1.5 million
After 60% by weight of stearyl alcohol was powder blended with 0% by weight, the mixture was allowed to stand in an oven at 170 ° C. for 30 minutes to swell the ultrahigh molecular weight polyethylene with stearyl alcohol. At this time, 0.5 part by weight of a phenolic stabilizer was added to 100 parts by weight of the mixture. This mixture was mixed with a Brabender kneader at a jacket temperature of 1
Kneading was carried out for 10 minutes at 70 ° C. and a rotation speed of 100 rpm. The resin temperature was constant at 195 ° C., the torque was also constant, and the mixture was transparent and uniform in the molten state.

Comparative Example 1 Kneading was performed for 15 minutes using a Brabender kneader using the mixture prepared in the same manner as in Reference Example 1 except that 30% by weight of stearyl alcohol was used with respect to 70% by weight of ultra high molecular weight polyethylene. However, the resin temperature rose to 240 ° C., and the torque fluctuation was very large. Further, the state of the melt was extremely non-uniform, and there were some parts of the ultrahigh molecular weight polyethylene which were not melted.

Reference Example 2 A uniform melt was obtained in the same manner as in Reference Example 1, except that a Banbury mixer was used at a temperature of 160 ° C. for uniform kneading. 30 mm without cooling and solidifying this melt
The sheet was supplied to a φ extruder and extruded from a T die having a clearance of 1 mm at a rotation speed of 40 rpm, and molded using a cooling roll. At this time, the temperature of the extruder was kept constant at 200 ° C and the die was set at 230 ° C. At this time, the amount of the composition extruded was stable, and the state of the sheet was smooth, and a uniform thickness of 0.6 mm could be obtained.

Comparative Example 2 In Reference Example 1, a mixture obtained by wetting ultrahigh molecular weight polyethylene with stearyl alcohol in an oven was supplied to a 30 mmφ extruder in the same manner as in Reference Example 2 without uniform kneading, and molding was performed. The composition was discharged from the die intermittently, and the sheet could not be formed.

Example 1 Using the sheet having a thickness of 0.6 mm obtained in Reference Example 2, 1
When uniaxial stretching was performed at a temperature of 00 ° C. and a speed of 100 mm / min, the stretching ratio reached 25 times. 60
The stearyl alcohol contained was extracted by dipping in ethanol at 5 ° C for 5 minutes. Regarding the stretched product after extraction, the stearyl alcohol was completely removed from the infrared spectrum, and the elastic modulus in the stretching direction was 30 GP and the breaking strength was 1.1 GP, which was very high performance.

Example 2 A smooth sheet having a thickness of 0.6 mm was obtained in the same manner as in Reference Example 2, except that stearyl alcohol was 80% by weight with respect to 20% by weight of ultrahigh molecular weight polyethylene. Simultaneous biaxial stretching of 6 × 6 times was performed at a rate of 100% / sec at a temperature of 80 ° C. using the sheet, and a uniform biaxially stretched film was obtained without cutting in the middle. The thickness of this film was 15μ.

The stearyl alcohol contained was extracted by immersing the film in ethanol at 60 ° C. for 3 minutes. As for the film after extraction, stearyl alcohol was completely removed from the infrared spectrum, and the cutting strength was 0.25 GP.
And showed a very high value.

Example 3 99% by weight of stearyl alcohol was powder blended with 1% by weight of ultra-high molecular weight polyethylene having a viscosity average molecular weight of 1,500,000 and left in an oil bath at 170 ° C. for 30 minutes while stirring with a magnetic stirrer. At this time, 0.5 part by weight of the phenolic stabilizer was added to 100 parts by weight of the mixture. The sheet obtained by pouring this mixture into a mold and cooling and solidifying was immersed in ethanol at 60 ° C. for 5 minutes to extract the contained stearyl alcohol.

As for the sheet after extraction, stearyl alcohol was completely removed from the infrared spectrum, and its cutting strength was 0.02 GP.

Example 4 A smooth sheet was obtained in the same manner as in Example 2 except that 10% by weight of ultrahigh molecular weight polyethylene and 90% by weight of stearyl alcohol were used.
Simultaneous biaxial stretching of 4 × 4 times was performed at a speed of 00% / sec, and a uniform biaxially stretched film was obtained without cutting in the middle.

When stearyl alcohol was extracted from the film in the same manner as in Example 2, a film in which stearyl alcohol was completely removed was obtained. The cutting strength of this film was measured and found to be 0.07 GP.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location C08K 5/07 KEQ 7242-4J 5/10 (72) Inventor Shogo Okumura Kamoshida, Midori-ku, Yokohama-shi, Kanagawa 1000, Machi Sanryo Kasei Co., Ltd. (56) Reference JP-A-57-172942 (JP, A) JP-A-49-52892 (JP, A) JP-B-48-11342 (JP, B1)

Claims (1)

[Claims] 1. (A) 0.5 to 55% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 400,000 or more (B) selected from alcohols, ethers, ketones or esters having 15 or more carbon atoms. An ultrahigh molecular weight polyethylene composition obtained by uniformly mixing 99.5 to 45% by weight of a flow improver, which is a solid at room temperature and has a melting point lower than that of the polyethylene, is molded into a sheet or film in a molten state without solidification, and during the molding Alternatively, a method for producing an ultrahigh molecular weight polyethylene sheet or film, which comprises extracting the component (B) with a lower alcohol or water or a mixture of a lower alcohol and water after molding.