JPS6166624A - Manufacture of ultra-high-molecular-weight polyethylene film or sheet - Google Patents

Abstract

PURPOSE:To obtain the captioned film having smooth surfaces efficiently by a method wherein the powder of ultra-high-molecular-weight polyethylene is mixed with organic solvent medium, heated to a high temperature to fuse it, extruded from a dual-screw extruder into the shape of film, heated to disperse the organic solvent medium and, therreafter, is cooled. CONSTITUTION:In case the film or sheet consisting of ultra-high-molecular- weight polyethylene having the average molecular weight of one million or more is manufactured, the powder of ultra-high-molecular-weight polyethylene is added into the organic solvent medium to obtain dispersion or mixture containing 10-80 weight % of polyethylene, thereafter, the dispersion or the mixture is heated under a temperature higher than the melting point thereof to fuse and extrude into the shape of film or sheet by the dual-screw extruder. Subsequently, it is heated to disperse the organic solvent medium and thereafter is cooled to obtain the objective film or sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION The present invention relates to a method for producing ultra-high molecular weight polyethylene films or sheets. More specifically, the present invention relates to a method for efficiently producing a film or sheet with a smooth surface from ultra-high molecular weight polyethylene having an average molecular weight of 1 million or more.

``Prior art'' Although ultra-high molecular weight polyethylene with an average molecular weight of 1 million or more has excellent properties such as self-lubricating properties, wear resistance, and low-temperature properties, its melt viscosity is too high, making it difficult to use for the intended purpose. It was difficult to mold it into objects.

The conventionally known molding method for ultra-high molecular weight polyethylene is
(a) A fine powder with a particle size of several tens to hundreds of microns is sintered over a long period of time to form a rod-shaped or plate-shaped sintered body, and then a film is formed from these sintered bodies. (b) A method of dissolving ultra-high molecular weight polyethylene in an organic solvent and forming it into a film or sheet by a casting method; (c) Adding powdered ultra-high molecular weight polyethylene to an organic solvent. A method of extruding a dispersion or mixture obtained by extruding into a film or sheet and volatilizing the organic solvent has been proposed.

The method (a) above has the disadvantage of extremely low productivity, and when the method (b) is used, the ultra-high molecular weight polyethylene solution has a high viscosity and is difficult to handle, and the solution is difficult to handle depending on the selection of temperature conditions. It has drawbacks such as instability such as precipitation of crystals.

In addition, the method 0→ was proposed by the applicant as a solution to the drawbacks seen in methods (a) and (c) above, but when adding ultra-high molecular weight polyethylene to an organic solvent, If the amount is less than a certain amount, for example less than 60% by weight, the ultra-high molecular weight polyethylene will not be uniformly compatible with the organic solvent, and the dispersion or mixture will not be formed into a film or sheet using an ordinary single-screw extruder. When this was applied, it did not feed smoothly into the extruder, resulting in unstable extrusion, and there was room for improvement.

[Problem J to be Solved by the Invention The present inventors have solved the above problems by achieving an average molecular weight of 100.
Made of ultra-high molecular weight polyethylene with a smooth surface)
・As a result of intensive research into a method for efficiently producing polyethylene or 7-carbonate, we developed a dispersion or mixture for forming a film or sheet prepared from an organic solvent and powdered ultra-high molecular weight polyethylene by twin-screw extrusion. The present invention was achieved based on the finding that by extruding by applying a machine, the problem of the above-mentioned biting can be solved and stable extrusion work can be performed.

``Means for solving the problem'' However, the gist of the present invention is that the average molecular weight is
In producing a film or sheet made of ultra-high molecular weight polyethylene of 0,000 or more, the above-mentioned ultra-high molecular weight polyethylene powder is added to an organic solvent to form a dispersion or mixture containing IO-80% by weight of polyethylene, the above-mentioned dispersion. A step of heating and melting a substance or mixture to a temperature higher than their melting temperature and extruding it into a film or sheet using a twin-screw extruder, heating the extruded film or sheet to remove the organic solvent. A method for producing an ultra-high molecular weight polyethylene film or sheet, comprising a step of volatilizing the film or sheet, and a step of cooling the film or sheet.

The present invention will be explained in detail below.

In the present invention, ultra-high molecular weight polyethylene means that the viscosity average molecular weight measured by dissolving it in a solvent such as decalin is i
Refers to more than oo million. Although high-molecular-weight polyethylene with an average molecular weight of less than 10,000 yen has a higher melt viscosity than ordinary polyethylene for molding, it can be molded using ordinary molding techniques, so there is no need to employ the method of the present invention. Ultra-high molecular weight polyethylene as a raw material is commercially available in the form of a fine powder with a particle size of several tens of microns to several hundred microns, and this can be used.

In the method of the present invention, in the first step, the powdered polyethylene is added to an organic solvent at room temperature, and the two are mixed to form a dispersion or mixture. The reason why the ultra-high molecular weight polyethylene as a raw material is added to an organic solvent at room temperature and the two are mixed together is to improve the processability of the ultra-high molecular weight polyethylene as a raw material.

The organic solvent that can be used in this case is preferably selected from those that have the ability to dissolve or swell ultra-high molecular weight polyethylene. Specific examples of organic solvents having this ability include hydrocarbons such as p-xylene, decalin, and octarine, and halogenated hydrocarbons such as tetrachloroethane. These examples are not intended to limit the invention.

Powdered ultra-high molecular weight polyethylene added to organic solvent is
The amount of the dispersion or mixture should be in the range of 10-♂OM amount %. If the amount of ultra-high molecular weight polyethylene is less than 70% by weight, the extrudate obtained in the next extrusion process will not be so strong that it will be difficult to handle, but it will be used in the subsequent process of recovering the organic solvent. It requires a large amount of energy and is extremely uneconomical. On the other hand, when the ♂O0% by weight is too high, the resulting dispersion or mixture becomes difficult or impossible to extrude as a uniform film or sheet in the subsequent extrusion step, which is not preferred. Within the above range, J O, 40
% by weight is particularly preferred. The dispersion or mixture is the above-mentioned 10-
When the amount of ultra-high molecular weight polyethylene is large within the 0% by weight range of ♂O, like flour containing a small amount of water,
The powder becomes wet and hardens into small lumps, and when the amount is low, it becomes a slurry, and the super high vesicle polyethylene does not mix in the organic solvent and becomes suspended.

However, when the dispersion or mixture in this state is charged into a known single-screw extruder in order to be molded into a film or notebook, the biting does not proceed smoothly as described above, and the extrusion is not stable.

Therefore, in the next step, the present invention involves heating the above dispersion or mixture to a temperature higher than their melting temperature, melting the dispersion, and extruding it into a film or notebook using a twin-screw extruder. be.

In the present invention, the "melting temperature of a dispersion or mixture" is based on the measurement method of heat of fusion by differential scanning calorimetry described in ASTM D 3≠/7-♂λ, and the temperature increase rate is 10°C/min. The temperature at which a peak occurs when measured below.

The melting temperature of the dispersion or mixture will vary depending on the type of solvent, the molecular weight of the ultra-high molecular weight polyethylene, and the ratio of solvent to ultra-high molecular weight polyethylene.

For example, in a mixture of ultra-high molecular weight polyethylene with a weight average molecular weight of about 3 million and p-xylene containing 70 weight percent, the melting temperature is /2J''Q, and 60 weight percent of ultra-high molecular weight polyethylene with the same molecular weight is mixed with p-xylene. In the case of a mixture containing decalin, the temperature is 727° C. The melting temperature of the dispersion or mixture is preferably measured and confirmed in advance.

If the temperature at which the dispersion or mixture is heated is lower than its measured melting temperature, the dispersion or mixture will not melt and cannot be extruded into a film or sheet.

The present invention requires the use of a twin-screw extruder when forming a film or sheet from the above-mentioned dispersion or mixture. The process can be carried out using the twin screw extruder. - In addition, as an example of heating a dispersion or a mixture to a temperature above their melting point, if the dispersion or mixture is heated and maintained at ♂O℃ or above while stirring,
A portion of the organic solvent is absorbed into the ultra-high molecular weight polyethylene,
The ultra-high molecular weight polyethylene and the organic solvent are given an affinity, and the ultra-high molecular weight polyethylene and the organic solvent are uniformly mixed to form a tri-blend or wet-blend form, which is then charged into an extruder. This makes it easier to dig in. In this case, the heating and holding temperature varies depending on the type of organic solvent, the particle size of the ultra-high molecular weight polyethylene, the content weight %, etc.
The temperature is selected in the range of 250°C, and the holding time is in the range of 7 to 10 minutes.

There are no particular restrictions on the twin-screw extruder that can be used in the present invention, and examples include co-rotating twin-screw extruders and counter-rotating twin-screw extruders having various performances. By applying a twin-screw extruder, the dispersion or mixture is forcibly fed between the pinches of two screws rotating in the same or different directions in the extruder, and the dispersion or mixture is The organic solvent and ultra-high molecular weight polyethylene are homogeneously melt-mixed, making it possible to stably deliver a film or sheet and ensure excellent quality, which is a major feature of the present invention.

To extrude the dispersion or mixture into a film or notebook, use a T-die, slit die, circular die, etc. that are conventionally used to extrude thermoplastic resins into a film or sheet.

It can be used as is.

Since the film or sheet extruded in the above step contains the organic solvent, in the next step the extruded film or sheet is heated to volatilize the organic solvent. The heating temperature at this time can be selected in the range of 100 to 300°C depending on the type and amount of the organic solvent contained in the film or sheet, the thickness of the film or sheet, etc.

When the heating temperature is lower than 100° C., the solvent volatilization rate is slow, which is undesirable. When the heating temperature is higher than 300° C., the solvent volatilization rate is increased, but the thermal deterioration of the ultra-high molecular weight polyethylene becomes severe, which is undesirable.

To heat the extruded film or sheet, there are two methods: heating it while holding it with paper coated with a release agent, a steel belt, etc., or heating it while holding both ends of the film or sheet in the width direction. You can. In addition, heating methods at this time include a method using hot air, a method using infrared rays, and a method using far infrared rays. Furthermore, a method of passing between a group of heated rolls may be used.

The organic solvent volatilized from the film or sheet is preferably recovered and reused.

The film or notebook from which the organic solvent has been volatilized is then cooled to around room temperature. The film or sheet may be cooled by natural cooling, or by forced cooling such as by blowing cooled air or passing between a group of cooled rolls.

After or during cooling, post-processing such as rolling with rolls may be performed to smooth the surface.

The ultra-high molecular weight film or sheet thus obtained can be wound into a roll and cut into a certain length for subsequent use.

The ultra-high molecular weight polyethylene film or sheet obtained by the method of the present invention can be used for various gaskets, banking, linings, tapes, packaging materials, etc. by taking advantage of its characteristics such as self-lubricity, abrasion resistance, and low-temperature properties. can be used.

"Effects of the Invention" The method of the present invention has the following particularly remarkable effects, and its industrial utility value is extremely large.

(1) In the method of the present invention, unlike the conventional method (a), the method of using a sintered body as a raw material fine powder and cutting out a film or sheet from this sintered body is not adopted. Productivity is much better than the conventional method (a).

(2) When using the method of the present invention, the mixture or dispersion consisting of an organic solvent and powdered ultra-high molecular weight polyethylene is:
It is easy to prepare and can be handled like a dispersion or powder at room temperature, and the process is much simpler than the conventional method (b).

(3) Furthermore, compared to the conventional method (c), 1 dispersion or mixture →
When extruding , →, → with an extruder, the biting progresses extremely smoothly, so the extrusion operation can be performed stably, and the organic solvent in the dispersion and ultra-high molecular weight polyethylene are mixed in the extruder. Since this process is more effective, it is possible to obtain a flat, uniform film or sheet of excellent quality.

“Examples” The present invention will be explained in detail based on Examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Heizenkusu Million 2 Hiro OM (Mitsui Petrochemical Industries ■
manufactured by Ultra High Molecular Weight Polyethylene with a weight average molecular weight of approximately 3 million and an average particle size of approximately 10 microns)
was added to p-xylene so that the concentration of polyethylene was in proportion to the weight of jO, and the two were mixed at room temperature to obtain a slurry-like dispersion.

This dispersion was measured using a differential tanshi calorimeter (manufactured by PerkinElmer, model DEC-■).

Temperature showing a peak (melting temperature of dispersion) by a method according to ASTM D J Hiro/7-♂co (heating rate 10°C/min)
When measured, it was io°C.

This dispersion was passed through a co-rotating twin screw extruder (screw diameter r Orrrm, L/D: j) equipped with a slit die (width 'Iorrrm, slit thickness /, (7sn)
), cylinder temperature W/♂O℃, Gui temperature 200
It was extruded into a sheet under the following conditions: °C, screw rotation speed/0'rpm. As a result, the mixture can be smoothly fed into the extruder, and the extrusion operation is also stable, with an average extrusion speed of 0.2 ky/min.
A sheet-like extrudate having a thickness of about 2 tran was obtained.

This sheet-like extrudate was heated for 10 minutes in a heating furnace whose temperature was adjusted to /♂Q°C to volatilize p-xylene as a solvent.

Next, this sheet-like extrudate was taken out from the heating furnace and cooled to room temperature, and the width was 3 g and the average thickness was /, /jN! An ultra-high molecular weight polyethylene sheet of n was obtained.

Comparative Example/Under the same conditions as in Example/, a slurry-like dispersion of ultra-high molecular weight polyethylene prepared from p-xylene and ultra-high molecular weight polyethylene and having a concentration SO type weight was heated to 120 mm without stirring.
℃ and held for 5 minutes. By this heating treatment, p
- A part of the xylene was absorbed by the ultra-high molecular weight polyethylene powder, and the slurry-like dispersion became a triblend-like state.

This dispersion was transferred to a single-screw extruder (regular AO
Full flight type screw with ran diameter, L, /D::2
2), cylinder temperature l♂θ℃, die temperature 200
When extruded into a sheet under conditions of ℃, the dispersion did not feed smoothly into the extruder, extrusion was intermittent and unstable, and a sheet extrudate with a flat surface could not be obtained. Ta.

Example λ Hi-Zex Million 2≠ (7M (same type as in Example/) was used at a concentration of polyethylene of 5 in p-xylene.
They were added so that the amount was 0% by weight, and the two were mixed at room temperature to obtain a slurry-like dispersion.

This dispersion was prepared using the same slit die and twin screw extruder as those used in Examples/1, and the cylinder temperature, die temperature,
It was extruded into a sheet under the same conditions as in Example, including the screw rotation speed. As a result, it is possible to smoothly feed the dispersion into the extruder, and the extrusion operation is also stable, with an average extrusion speed of 0.1547 minutes. -oran, a sheet-like extrudate with a thickness of about 7.2 mm was obtained.

This sheet-like extrudate was heated for 70 minutes in a heating furnace whose temperature was adjusted to /♂O<0>C to volatilize p-xylene as a solvent. Next, this sheet-like extrudate was taken out from the heating furnace and cooled to room temperature to obtain an ultra-high molecular weight polyethylene sheet with a width of about 3 g and an average thickness of /jmm.

Similar to Comparative Example/Example λ, Heisenkus Million 2taoM
, the concentration of polyethylene in p-xylene is 50% by weight.
and mixed the two at room temperature to obtain a slurry-like dispersion.

This dispersion was transferred to a single screw extruder (normal ≠o
Full flight type screw with tran diameter, L/D medium 22
), cylinder temperature/♂O℃, die temperature 200℃
I tried to extrude it into a sheet under the following conditions, but the biting did not go smoothly and extrusion was impossible.

Example 3 Hi-Zex・λtaoM (manufactured by Mitsui Petrochemical Industries, Ltd.,
ultra-high molecular weight polyethylene with a weight average molecular weight of about 3 million and an average particle size of about 100 microns), p
- Polyethylene was added to xylene so that the concentration was SO weight %, and the two were mixed at room temperature to obtain a slurry-like dispersion.

This dispersion was transferred to a cylinder at a temperature of The dispersion was extruded into a sheet under the same conditions as in Example 1, including die temperature and screw rotation speed.As a result, the dispersion could be smoothly penetrated by the extruder.
In addition, the extrusion operation is stable, with an average extrusion speed of 0. s
A 7-t-shaped extrudate having a width≠own and a thickness of about 7.3 mm was obtained at #/min.

This notebook-shaped extrudate/! It was heated for 70 minutes in a heating furnace whose temperature was adjusted to Q°C to volatilize p-xylene as a solvent.

Then, this notebook-shaped extrudate was taken out from the heating furnace and cooled to room temperature to obtain an ultra-high molecular weight polyethylene notebook having a width of 3° C. and an average thickness of 2TrLM.

Comparative Example 3 A slurry dispersion of ultra-high molecular weight polyethylene prepared from p-xylene and ultra-high molecular weight polyethylene under the same conditions as in Example 3 and having a concentration of jO by weight was heated to 120 ml without stirring.
℃ and held for 5 minutes. By this heating treatment, p
- Some of the xylene was absorbed by the ultra-high molecular weight polyethylene powder, and the slurry-like dispersion became a triblend.

This dispersion was transferred to a single screw extruder (4'0rIn
I tried to extrude it into a sheet using an n-diameter rapid compression type screw, L/D key 22) under the conditions of a cylinder temperature of 0°C and a die density of λOO°C, but the result was not as good as A1. Extrusion was not possible.

Applicant Mitsubishi Monsa/Tokasei Co., Ltd. Agent
Person Patent Attorney Hase - (7 others)

Claims (1)

[Claims] (1) When producing a film or sheet made of ultra-high molecular weight polyethylene with an average molecular weight of 1 million or more, the ultra-high molecular weight polyethylene powder is added to an organic solvent to form a dispersion or mixture containing 10 to 80% by weight of polyethylene. A step of heating the above dispersion or mixture to a temperature higher than their melting temperature to melt it and extruding it into a film or sheet using a twin-screw extruder, heating the extruded film or sheet. A method for producing an ultra-high molecular weight polyethylene film or sheet, comprising the steps of: volatilizing the organic solvent; and cooling the film or sheet.