JPH07156174A - Continuous production of polyethylene material having high strength and high modulus of elasticity - Google Patents

Abstract

PURPOSE:To continuously produce a polyethylene material having high strength and the high modulus of elasticity by intermittently charging a polyethylene powder with an ultrahigh mol.wt. in a molding cylinder and repeating the push-in operation of the polyethylene powder by a ram to continuously take out a molded object and subsequently stretching the molded object. CONSTITUTION:The polyethylene powder with an ultrahigh mol.wt. the instrinsic viscosity in decalin at l35 deg.C of which is introduced into a hopper 3 and of which is 5-50dl/g is intermittently pushed in the inlet part of a molding cylinder 1 by a ram 2 and subjected to compression molding within the molding cylinder 1 by repeating the push-in operation due to the ram and an extrusion molded object is continuously obtained from a lower die 5. This extrusion molded object is rolled and stretched to continuously produce a polyethylene material having high strength and the high modulus of elasticity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for continuously producing a high-strength, high-modulus polyethylene material. More specifically, it relates to a method for efficiently producing a high-strength, high-modulus polyethylene material by continuously extruding a specific ultra-high molecular weight polyethylene powder by a specific method and then stretching.

[0002]

2. Description of the Related Art So-called ultra-high molecular weight polyethylene having a remarkably high molecular weight is used in various fields as an engineering plastic having excellent characteristics such as impact resistance, abrasion resistance and self-lubricating property. Since this ultrahigh molecular weight polyethylene has a much higher molecular weight than general-purpose polyethylene, it is expected that a molded product having high strength and high elasticity can be obtained if it can be highly oriented. Various studies have been made.

[0003] However, ultrahigh molecular weight polyethylene has a higher melt viscosity than general-purpose polyethylene, the molding processability is extremely poor by a conventional method, and it is not possible to stretch it to highly orient it.

Paul Smith, Peter Yarn Lemstra et al. Proposed a method for producing a fiber having high strength and high elastic modulus by drawing a gel obtained from a decalin solution (dope) of an ultrahigh molecular weight polyolefin at a high ratio. (JP-A-5
6-15408). The polymer concentration in the dope is
It has been carried out at an extremely low concentration of 3% by weight with a weight average molecular weight of 1.5 million and 1% by weight with 4 million. In practical use, a large amount of solvent is used and a highly viscous solution is prepared. It is extremely disadvantageous in terms of economics such as method and handling.

There are also various proposals for a method of highly stretching and highly orienting a single crystal mat of an ultrahigh molecular weight polyolefin [JP-A-59-187614, JP-A-60-15120, and JP-A-60-15120]. 60-97836, Proceedings of the Society of Polymer Science, Vol. 34, No. 4, page 873 (1985).
etc].

However, in these methods, an ultrahigh molecular weight polyolefin is previously made into a dilute solution of a solvent such as xylene, decalin or kerosene, and then solid phase extrusion is carried out using a single crystal mat obtained by cooling or isothermal crystallization. Stretching is performed. Therefore, this method still has not solved the problem that a large amount of solvent must be used when producing a single crystal mat.

In order to solve the above-mentioned problems, the inventors of the present invention compression-mold ultra-high molecular weight polyethylene powder at a temperature below the melting point of the powder without melting or melting and then rolling. And a method for producing a high-strength and high-modulus polyethylene material by stretching and stretching have been proposed (JP-A-63-
41512 and JP-A-63-66207).

Further, as a result of further studies, the present inventors have found that ultrahigh molecular weight polyethylene powder is continuously compression-molded by a specific device under a temperature condition lower than the melting point of the polyethylene powder, and then rolled and stretched. Have found that a polyolefin material having high strength and elastic modulus can be produced with high production efficiency (JP-A-2-258237).
issue).

[0009]

As described above, the present inventors have already proposed a means for continuously compression-molding ultra-high molecular weight polyethylene powder under a relatively low pressure to form a sheet, and by the method, a post-process is performed. Rolling worked very effectively, and the total draw ratio including the roll ratio could be increased, which made a great contribution to mass production in terms of quality and productivity. However, during compression molding, there may be a case where minute pressure non-uniformity occurs, and that part becomes a defect, and pressure is released at both edges of the sheet, resulting in poor yield and production speed. It tended to decline. Rolling of such defective portions inside the compression-molded sheet and uneven portions such as both end portions lacks uniformity, and rolling of defective portions causes banks, which significantly reduces productivity and yield. It was Further, when a sheet having a defective portion is continuously produced in the subsequent stretching step, the stretching ratio cannot be greatly increased, resulting in various problems such as poor yield.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a specific ultrahigh molecular weight polyethylene powder is extruded at a temperature lower than the melting point of the polyethylene powder, High strength by stretching
In the method for continuously producing a high elastic modulus polyethylene material, the extrusion molding is carried out by intermittently putting the polyethylene powder into a molding cylinder and pushing it in by a ram to take out an extruded product in a continuous state,
The present invention was found to be able to continuously extrude with a simple device, to have a high draw ratio in the subsequent drawing step, and to produce a high-strength, high-modulus polyethylene material at a lower cost than in the past. Reached

That is, according to the present invention, an ultrahigh molecular weight polyethylene powder having an intrinsic viscosity in decalin at 135 ° C. of 5 to 50 dl / g is extruded at a temperature lower than the melting point of the polyethylene powder and then stretched. In a method for continuously producing a high-strength, high-modulus polyethylene material, the extrusion molding continuously removes the extruded product by repeating the operation of intermittently inserting the polyethylene powder into a molding cylinder and pushing it with a ram. And a method for continuously producing a high-strength, high-modulus polyethylene material, characterized in that an extruded product is rolled prior to the stretching. Regarding

The present invention will be described in detail below. (1) High molecular weight polyethylene powder The ultra high molecular weight polyethylene used for producing the high-strength, high-modulus polyethylene material of the present invention has an intrinsic viscosity in decalin of 135 ° C. of 5 to 50 dl / g, preferably 8 to
40 dl / g, more preferably 10 to 30 dl / g, and have a viscosity average molecular weight of 500,000 to 12,000,000, preferably 900,000 to 9,000,000, and more preferably 1.2,000,000 to 60.
It is equivalent to 0,000.

If the intrinsic viscosity is less than 5 dl / g, the mechanical properties of the stretched product deteriorate, which is not preferable. Also, 50 dl
If it exceeds / g, the workability in compression molding, rolling and stretching is poor, which is also not preferable.

The shape of these ultra high molecular weight polyethylenes is not particularly limited, but usually, granular or powdery ones are preferably used, for example, a particle size of 2000 μm or less, preferably 1 to 2000 μm, more preferably 10 ~ 1000μ
The range is m. In addition, it is preferable that the particle size distribution is narrow so that there are few defects during compression molding and a homogeneous sheet or film can be obtained.

The above-mentioned ultra-high molecular weight polyethylene used in the present invention is a catalyst component containing at least one compound selected from the compounds containing transition metal elements of Groups IV to VI of the periodic table and, if necessary, an organometallic compound. It can be obtained by homopolymerization of ethylene or copolymerization of eletin and α-olefin in the presence of a catalyst in combination with a compound.

The α-olefin has 3 to 12 carbon atoms,
Preferably 3 to 6 can be used. Specific examples include propylene, butene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, dodecene-1. Of these, particularly preferred are propylene, butene-1,4-methylpentene-
1, hexane-1. As the comonomer, dienes such as butadiene, 1.4-hexadiene, vinyl norbornene, ethylidene-norbornene and the like may be used in combination. The α-olefin content in the ethylene / α-olefin copolymer is 0.001 to 10 mol%, preferably
It is 0.01 to 5 mol%, more preferably 0.1 to 1 mol%.

Periodic Tables IV to VI constituting the catalyst components
As the compound containing a group transition metal, specifically, a titanium compound, a vanadium compound, a chromium compound, a zirconium compound, a hafnium compound and the like are preferable. Also,
You may use these compounds in combination of multiple types.

Examples of titanium compounds include titanium halides, alkoxy halides, alkoxides, and halogenated oxides, and tetravalent titanium compounds and trivalent titanium compounds are preferable. Specific examples of the tetravalent titanium compound include Ti (OR) _n X _4-n (wherein R represents an alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, or an aralkyl group, and X represents A halogen atom is shown, and n is 0 ≦ n ≦ 4), and titanium tetrachloride is particularly preferable.

Examples of the trivalent titanium compound include titanium trihalides such as titanium trichloride, and the general formula Ti (OR) _m X _4-m (wherein R is an alkyl group having 1 to 20 carbon atoms, Represents an aryl group or an alkyl group, and X represents a halogen atom.
Is 0 ≦ m ≦ 4. And a trivalent titanium compound obtained by reducing a tetravalent alkoxytitanium halide represented by the formula (1) with an organometallic compound of a metal of groups I to III of the periodic table. Of these titanium compounds, tetravalent titanium compounds are particularly preferable.

Examples of the vanadium compound include vanadium halides, alkoxy halides, alkoxides and halogenated oxides. Specific examples thereof include tetrahalogenated vanadium such as vanadium tetrachloride and tetraethoxyvanadium. Examples thereof include tetravalent vanadium compounds, pentavalent vanadium compounds such as vanadium oxytrichloride, ethoxydichlorovanadyl, triethoxyvanadyl and tributoxyvanadyl, and trivalent vanadium compounds such as vanadium trichloride and vanadium triethoxide.

Further, the above titanium compound or vanadium compound may be treated with one or more electron donating compounds. Examples of the electron donating compound include ethers, thioethers, thiolphosphines, stibines, arsines, amines, amides, ketones and esters.

The titanium compound or vanadium compound may be used in combination with the magnesium compound. Examples of the magnesium compound used in combination include metal magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, and the like, and a metal and a magnesium atom selected from silicon, aluminum, and calcium. Treating or reacting double salts, double oxides, carbonates, chlorides or hydroxides containing and further with these inorganic solid compounds with oxygen-containing compounds, sulfur-containing compounds, aromatic hydrocarbons, halogen-containing substances Examples thereof include those obtained by adding the above magnesium compound to an oxide containing silicon and aluminum.

When a titanium compound or a vanadium compound and a magnesium compound are used in combination, the contacting method between them is not particularly limited and a known method can be adopted.

Examples of the oxygen-containing compound include water,
Examples thereof include organic oxygen-containing compounds such as alcohols, phenols, ketones, aldehydes, carboxylic acids, esters, polysiloxanes and acid amides, and inorganic oxygen-containing compounds such as metal alkoxides and metal oxychlorides. Examples of the sulfur-containing compound include organic sulfur-containing compounds such as thole and thioether, and inorganic sulfur compounds such as sulfur dioxide, sulfur trioxide and sulfuric acid. Aromatic hydrocarbons include benzene, toluene, xylene, anthracene,
Various monocyclic and polycyclic aromatic hydrocarbon compounds such as phenanthrene can be exemplified. Examples of halogen-containing substances include compounds such as chlorine, hydrogen chloride, metal chlorides, and organic halides.

As another example of the catalyst system, a reaction system in which a reaction product of an organomagnesium compound such as a so-called Grignard compound and a titanium compound is used and an organoaluminum compound is combined therewith can be exemplified.

Examples of other catalyst systems include SiO ₂ , A
A solid substance obtained by contacting an inorganic oxide such as l ₂ O ₃ with the above-mentioned solid catalyst component containing at least magnesium and titanium and using an organoaluminum compound in combination can be exemplified.

In these catalyst systems, the titanium compound can be used as an adduct with the organic carboxylic acid ester, and the above-mentioned inorganic solid compound containing magnesium can be used after being contact-treated with the organic carboxylic acid ester. You can also Further, there is no problem even if the organoaluminum compound is used as an adduct with the organic carboxylic acid ester. Further, in all cases, it is possible to carry out the use of a catalyst system prepared in the presence of an organic carboxylic acid ester without any trouble.

Specific examples of the chromium compound include chromium trioxide or a catalyst called a Phillips catalyst in which a compound that forms chromium oxide at least partially by firing is supported on an inorganic oxide carrier. Examples of the inorganic oxide carrier include silica, alumina, silica-alumina, titania, zirconia, thoria, and a mixture thereof, and silica and silica-alumina are preferable.

Examples of the chromium compound to be supported include oxides of chromium, or compounds that form chromium oxide at least partially by firing, such as halides of chromium, oxyhalides, nitrates, acetates, nitrates, alcoholates and the like. Specific examples thereof include chromium trioxide, chromyl chloride, potassium dichromate, ammonium chromate, chromium nitrate, chromium acetate, chromium acetylacetonate, and ditertiarybutyl chromate.

The chromium compound can be supported on the carrier by a known method such as impregnation, solvent removal, sublimation and the like, and an appropriate method may be used depending on the kind of the chromium compound used. The amount of chromium supported is 0.1 to 10% by weight, preferably 0.1 to 10% by weight of chromium atoms based on the carrier.
It is 0.3 to 5% by weight, more preferably 0.5 to 3% by weight.

As described above, the chromium compound-carrying support is fired to activate it. The firing activation is generally carried out in a non-reducing atmosphere substantially free of water, for example, in the presence of oxygen. It may be carried out in the presence of an inert gas or under reduced pressure. Dry air is preferably used.
Firing is performed at a temperature of 450 ° C. or higher, preferably 500 to 900.
It is carried out at 0 ° C. for several minutes to several hours, preferably 0.5 to 10 hours.
It is preferable to perform the activation under a fluidized state by sufficiently using dry air during firing.

It is also possible to use a known method in which titanates, fluorine-containing salts and the like are added at the time of supporting or firing to control the activity and the like.

The catalyst carrying the chromium compound may be reduced with carbon monoxide, ethylene, organoaluminum, etc. before use.

Examples of the zirconium compound or the hafnium compound include a zirconium compound or a hafnium compound having a group having a conjugated π electron as a ligand, and are represented by the general formula: R ¹ _a R ² _b MR ³ _c R ⁴ _d ( here, M represents a zirconium or hafnium ^{atom, R 1, R 2, R} 3 and R ⁴ represents a hydrocarbon residue having 1 to 20 carbon atoms, a halogen atom or a hydrogen atom. in addition, R ^1, R ² ，
At least one of R ³ and R ⁴ is a hydrocarbon residue.
The compounds represented by a, b, c and d satisfy the conditional expression of a + b + c + d = 4). As the hydrocarbon residue in the formula, an alkyl group, an aryl group, a cycloalkyl group, an aralkyl group, an alkoxy group,
A cycloalkadienyl group, a sulfur-containing hydrocarbon residue, a nitrogen-containing hydrocarbon residue, a phosphorus-containing hydrocarbon residue and the like are preferable.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group and an oleyl group, and an aryl group includes a phenyl group. Group, tolyl group and the like, as the cycloalkyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, a bicyclononyl group and the like, and as the aralkyl group, a benzyl group, a neofile group and the like. It

Examples of the cycloalkadienyl group include cyclopentadienyl group, methylcyclopentadienyl group, ethylcyclopentadienyl group, dimethylcyclopentadienyl group, indenyl group, tetrahydroindenyl group and the like. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and the like. Examples of the sulfur-containing hydrocarbon residue include a thioethyl group and a thiophenyl group, and examples of the nitrogen-containing hydrocarbon residue include a dimethylamide group, a diethylamide group and a dipropylamide group.

Other examples include unsaturated fatty residues such as vinyl group, allyl group, propenyl group, isopropenyl group and 1-butenyl group, and unsaturated alicyclic groups such as letalohexenyl group. Examples of the halogen atom include fluorine, chlorine and bromine.

Of course, these zirconium compounds or hafnium compounds can also be used by supporting them on the above-mentioned inorganic oxide carrier.

As the organometallic compound used in the method for producing the ultrahigh molecular weight polyethylene powder of the present invention, organometallic compounds of Groups 1 to IV of the Periodic Table, which are known as a component of Ziegler type catalysts, can be used. Formula Rn AlX _3-n
(However, R is an alkyl group having 1 to 20 carbon atoms, an aryl group or an alkoxyl group, X is a halogen atom, and n is 0 <n.
≦ 3, where N ≧ 2, each R may be the same or different), and a general formula R ₂ Z _n (wherein R is an alkyl group having 1 to 20 carbon atoms). , Which may be the same or different from each other), and may be a mixture thereof.

Examples of the organic aluminum compound include triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride, monoethoxydialkylaluminum,
Examples include diethoxy monoalkyl aluminum,
In addition, a general formula obtained by the reaction of trialkylaluminum and water

[0041]

[Chemical 1] (Wherein R is a hydrocarbon group having 1 to 18 carbon atoms, n is 2 ≦ n ≦ 100, preferably 2 ≦ n ≦
50 is shown) and the like can also be used.

The amount of the organometallic compound used is not particularly limited, but is usually 0.1 to 1,000 mol based on the transition metal compound.
Can be used 1 time.

The polymerization reaction is carried out in a gas phase state with oxygen and water being substantially cut off or an inert solvent with respect to the catalyst, such as an aliphatic system such as butane, isobutane, pentane, hexane, octane, decane, dodecane. It is carried out in the presence of hydrocarbons, alicyclic hydrocarbons such as cyclopentane and cyclohexane, aromatic hydrocarbons such as benzene and toluene, and petroleum fractions, or using the monomer itself as a solvent. The polymerization temperature is lower than the melting point of the ultrahigh molecular weight polyethylene to be produced, usually -20 to 110 ° C, preferably 0 to 90 ° C.

If the polymerization temperature is not less than the melting point of the ultrahigh molecular weight polyethylene that can be obtained, stretching cannot be performed 20 times or more in the subsequent stretching step, which is not preferable. The polymerization pressure is usually 0 to 70 kg / cm ² G, preferably 0 to 60 kg / cm ²
It is desirable that it is G.

The molecular weight can be adjusted by changing the polymerization conditions such as the polymerization temperature, the polymerization pressure, the type of catalyst, the molar ratio of the catalyst components, hydrogenation to the polymerization system, and there is no particular limitation. Of course, it is possible to carry out a two-step or multi-step polymerization reaction with different polymerization conditions such as hydrogen concentration and polymerization temperature without any trouble.

Thus, a powdery ultra high molecular weight polyethylene is obtained. Next, the process of extrusion molding these ultra high molecular weight polyethylene powders will be described. The extrusion molding of the present invention is characterized in that the above-mentioned polyethylene powder is intermittently put in a molding cylinder and then extruded by a ram is repeated to take out the extruded product in a continuous state.

The apparatus used for these will be briefly described with reference to FIG. 1, which is one specific example. This apparatus basically has a forming cylinder 1, a ram 2, a hopper 3 for supplying raw materials, a forming cylinder temperature adjusting zone 4 and a die 5. The cross-sectional shape of the molding cylinder is not particularly limited as long as a uniform extrudate can be obtained continuously. Further, the shape of the extrudate is not particularly limited, and usually includes a sheet shape, a rod shape, and preferably a sheet shape,
The shape of the die is selected accordingly, but usually, a circular shape, an elliptical shape, a slit shape and the like can be mentioned. As for the shape of such a die, for example, in the case of a circular shape, an O.D. 5-10
mm, preferably 1-8 mm, more preferably 1-5
In the case of slits, the longitudinal direction is usually 5 to 500 mm, preferably 50 to 300 mm, and the lateral direction is usually 0.5 to 10 mm, preferably 1 to 5 mm. The length of the cylinder is not particularly limited, but is usually 100 to 5000 mm, preferably 500 to
About 3000 mm is desirable.

The ram extrusion pressure is not particularly limited as long as it can maintain the shape of the extruded product obtained from the die, but is usually 5 to 10.000 kgf / cm ² , preferably 10 to 5.000 kgf / cm ² , and further. Preferably 5
About 0 to 3.000 kgf / cm ² is preferable. It is essential that the temperature at the time of extrusion molding is lower than the melting point of the ultra high molecular weight polyethylene as a raw material as described above, and is usually 50 ° C.
~ Below melting point of ultra high molecular weight polyethylene, preferably 90
~ 140 ° C is desirable. If the extrusion temperature exceeds the melting point of the ultra high molecular weight polyethylene, the stretching ratio cannot be increased in the subsequent stretching step, which is not preferable. As a heating means for applying a temperature for extrusion molding to the molding apparatus, it is desirable to provide a heating zone 4 for directly heating the molding cylinder portion as shown in FIG.

To carry out the production of the high-strength, high-modulus polyethylene material of the present invention using this exemplified apparatus,
First, the raw material ultrahigh molecular weight polyethylene powder put into the hopper 3 is intermittently pushed into the inlet of the forming cylinder by a ram, and then the ram is pulled upward, and new raw material powder is supplied to the lower portion of the ram and then again. Push the ram into the inlet of the forming cylinder. By repeating this cycle, compression molding is performed in the molding cylinder, and an extruded product is continuously obtained from the lower die. That is, the resin is shot and supplied quantitatively, and the extruded product is continuously taken out. The extrusion speed is not particularly limited, but is usually 5 to 200 mm / min, preferably 10 to
150 mm / min is desirable.

Further, the hopper for supplying the raw material may be vibrated if necessary. Of course, in addition to the vertical extrusion molding apparatus as shown in FIG. 1, a horizontal extrusion molding apparatus performing the same operation as described above can be used without any trouble.

In the present invention, the extruded product thus obtained from the high-strength and high-modulus polyethylene material is stretched, preferably rolled and then stretched.

As a rolling method, a known method can be used, but polyethylene is not melted but is held in a solid state and is sandwiched by rolling rolls having different rotating directions to obtain a rolled sheet or film. At this time, the deformation ratio of the material by the rolling operation can be widely selected,
Usually, rolling efficiency (length after rolling / length before rolling) is 1.
It is desirable to set it to 2 to 20, preferably 1.5 to 10. The temperature at this time is 20 ° C. or higher and lower than the melting point, preferably 90 ° C. or higher and lower than the melting point. Of course, the above rolling operation can be performed in one or more multi-stage rolling steps.

There are various methods of tensile stretching performed after rolling, and the method is not particularly limited as long as the object of the present invention is not impaired. For example, first, as heating means, hot air stretching, cylinder stretching, hot plate stretching are used. and so on. It is also possible to draw between the nip rolls as a means for applying the drawing tension, apply tension between the clover rolls and the multi-stage rolls, or draw while maintaining the drawing tension by the Nelson roll method. Although any of these methods can be used, the most preferred method is to apply tension between nip rolls and stretch on a hot cylinder.

The temperature in the tensile drawing is lower than the melting point of polyethylene powder, usually 20 to 160 ° C., preferably 20 to 1
It is carried out at 50 ° C., more preferably 90 to 145 ° C., particularly preferably 90 to 140 ° C. As a means for stretching at a high ratio, there is multistage stretching. For example, first 100-140
This is a method in which one-stage stretching is performed at 0 ° C., and then further stretching is performed at a temperature higher than the first stage.

The degree of tensile stretching depends on the molecular weight and composition of the polyethylene used and can be appropriately selected, but is usually 0.1 to 500 m / min, preferably 1 to 200 m / min.

The higher the draw ratio, the higher the strength and the high elastic modulus that can be achieved. Therefore, it is desirable to increase the draw ratio as much as possible. In the method of the present invention, the draw ratio is set to the draw efficiency (length after draw / before draw). Length) 2 to 20, preferably 5
The total draw ratio (total draw ratio of rolling and drawing) of at least 20 times or more, usually 60 times or more, and preferably 80 to 200 times is desirable when rolling and drawing are used in combination.

Further, in the present invention, if desired, prior to the rolling step, a step of continuously compression-molding an extruded product of ultrahigh molecular weight polyethylene is preferably carried out. In the compression molding step in this case, for example, the polyethylene extrudate is supplied between a pair of endless belts which are vertically opposed to each other, and the extrudate is moved while being sandwiched between the endless belts, and is provided inside the endless belt. The pressurizing means continuously performs compression molding at a temperature lower than the melting point of the extrudate, and preferably, the pressurizing means provided inside the endless belt includes a pressurizing plate and the pressurizing plate. It is preferable that the endless belt is composed of a group of rollers that are rotatably connected to each other.

The apparatus used for this will be briefly described with reference to FIG. 2, which is a specific example.

This apparatus is basically composed of a pair of endless belts 10 and 11 vertically opposed to each other, which are tensioned by rolls 6 to 9, and pressurization for pressing a powder sample through the endless belts. The plate 12 and the roller 13 which is rotatably connected to each other between the pressure plate and the endless belt have a pressure unit.

The pressing means in the present invention comprises a pressing plate provided inside the endless belt and a group of rollers which are rotatably connected to each other between the pressing plate and the endless belt. As a group of rotatable rollers connected to each other interposed between the pressure plate and the endless belt, the rotation axes of the rollers in the roller group are arranged substantially perpendicular to the traveling direction of the endless belt and do not contact each other. It is suitable to arrange a large number of them in close contact with each other.

The center axes of both ends of each of these rollers are fixed by a chain 14, and the chain is engaged with a sprocket 15 arranged before and after the pressure plate, whereby the roller group is set to one of the running speeds of the endless belt. It is better to drive at a speed of about / 2.

This roller group may be fixedly interposed between the endless belt and the pressure plate. In this case, however, the frictional force due to the slip is respectively generated between the roller group and the endless belt and the pressure plate. As a result, there is a problem in the durability of the device.

The pressure plate is not particularly limited as long as the surface in contact with the roller group is smooth and the pressure can be transmitted uniformly.

The length of the pressure plate in the running direction of the endless belt is usually 30 to 400 cm, preferably 50 to 2
It is about 00 cm. Average pressure which pressure plate is applied to the endless belt is usually less than 100 kg / cm ^2, preferably, 0.1~50kg / cm ² more preferably from 0.1 to 20 kg / cm ² or so, preferably 0.5 to 1
0 kg / cm ² , more preferably 1.0 to 8.0 kg
/ Cm ² of pressure. The pressure plate can first press the polyethylene extrudate through the endless belt.
Although it has a significant role, it can be used at the same time as a heating means for the object to be compressed. In the method of the present invention,
Performing the compression step at a temperature lower than the melting point of the mixture to be compressed is extremely important in obtaining a high-strength, high-modulus polyethylene material through a stretching step that is subsequently performed. However, in order to obtain a good compression molded product, it is desirable that the temperature is lower than the melting point of the mixture and is within an allowable range. That is, it is usually 50 ° C or higher and lower than the melting point, preferably 90 to 140 ° C. As a heating means for the object to be compressed for that purpose, it is optimal to directly heat the endless belt in the pressing section, but as shown in FIG. It is practically convenient to heat the object to be compressed from the pressure plate through the group of rollers and the endless belt, or to dispose the preheater 17 close to the endless belt to heat the object as shown in FIG. .

As a mode of arranging the heating means 16 on the pressure plate, an insulating heater 18 may be provided and an electric heater may be embedded in the pressure plate, or a circulation path for a heat medium may be provided in the pressure plate. May be provided and heated using a heat medium.

The running speed of the endless belt depends on the length of the pressure plate and the compression conditions, but is usually 10 cm / cm.
Minutes or more, preferably about 50 to 200 cm / min. The extruded product from the ram extruding device 19 on the endless belt was preheated if necessary, and then moved to the narrow pressure portion by the upper and lower endless belts, and then the roller group and the pressure plate were arranged. Moved to the compression unit. Here, the pressure from a hydraulic cylinder (not shown) is transmitted from the hydraulic piston 15 to the pressure plate, and a compression force is applied to the object to be compressed via the roller group and the endless belt. At this time, heat from the heating body is also transferred to the object to be compressed through the roller group and the endless belt,
The temperature of the object to be compressed is maintained at a predetermined temperature.

The compression-molded sheet thus compression-molded leaves the endless belt after passing through the roll portion. In this way, the compression molded sheet is continuously molded. In addition, it is desirable that these compression-molded sheets have a wall thickness of usually 2 to 0.2 mm, preferably 1.5 to 0.5 mm.

Thus, a high strength, high modulus polyethylene material is produced. The polyethylene material obtained usually has a tensile elastic modulus of 120 GPa or more and a tensile strength of 2 GPa or more. Various applications are possible by applying the material thus obtained, for example, by applying splitting treatment or prepreging.

[0069]

EFFECTS OF THE INVENTION The production method of the present invention has been found to have a particular extrusion molding method, whereby the yield can be significantly improved as compared with the conventional method, and a high-strength and high-modulus polyethylene material can be obtained at low cost. To be Moreover, the molding apparatus becomes simpler than ever, and the molding cost is reduced. Further, the fact that molding is possible at a low temperature is an extremely economical process in that not only the heat energy cost is low, but also the stable temperature range is wide and the operation stability is good.

[0070]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 An ultra high molecular weight polyethylene powder having a viscosity average molecular weight of about 3,000,000 was prepared with the equipment and conditions of the following specifications and a thickness of 0.8 mm.
Sheet, and then roll-rolled, slitting the obtained sheet into a width of 5 mm, and then stretching the sheet,
A tape having a total draw ratio of 75 times was obtained. The tape had a tensile strength of 2.7 GPa and a tensile modulus of 125 GPa.

Ram Extruder: Cylinder: Diameter 30 mm Length 600 mm Ram: Stroke 70 mm Die: Width 10 cm Thickness 0.8 mm Temperature: Cylinder 1 115 ° C. 2 125 ° C. 3 130 ° C. Die 130 ° C. Molding speed: Ram cycle (reciprocating) 15 seconds Forming speed 80 mm / min (20 mm / cycle) Rolling device: Roll diameter: 150 mmφ Face length: 300 mm Roll temperature: 135 ° C. (upper and lower) Peripheral speed: 1.5 m / min Rolling ratio: 5 times Stretching device (heat) Plate type): Preheating roll: 250 mmφ, 3 rolls (circulating heat medium oil inside) Nip roll: 200 mmφ, made of silicone rubber (one set for inlet and outlet) Cooling roll: 250 mmφ, 3 rolls (circulating water inside) Heat plate: (Embedded electric heater inside) Length 500mm

[0073]

[Table 1]

[Brief description of drawings]

FIG. 1 is an example of a pushing device using a ram suitable for the manufacturing method of the present invention.

FIG. 2 is an example of a compression molding process using the endless belt of the present invention.

FIG. 3 is an example of a partially enlarged view of a compression molding device.

[Explanation of symbols]

 1 Cylinder 2 Ram 3 Hopper 4 Molding Cylinder Temperature Control Zone 5 Die 6-9 Roll 10-11 Endless Belt 12 Pressure Plate 13 Roller Group 14 Chain 15 Sprocket 16 Heating Means 17 Preheater 18 Insulation Part 19 Ram Extrusion Device

Claims (2)

[Claims] 1. Ultrahigh molecular weight polyethylene powder having an intrinsic viscosity of 5 to 50 dl / g in decalin at 135 ° C. is extruded at a temperature lower than the melting point of the polyethylene powder and then stretched to obtain high strength and high strength. In a method for continuously producing a polyethylene material having a modulus of elasticity, the extrusion molding is characterized in that the polyethylene powder is intermittently put into a molding cylinder, and an extrusion molding is continuously taken out by repeating an operation of pushing the polyethylene powder by a ram. High strength
A continuous method for producing high modulus polyethylene material. 2. The method according to claim 1, prior to stretching.
A continuous method for producing a high-strength, high-modulus polyethylene material, which comprises rolling an extruded product.