JPS63159408A - Preparation of polyethylene of high strength and high modulus of elasticity - Google Patents

Abstract

PURPOSE:To prepare a PE material of a high strength and a high modulus of elasticity, by stretching a specified ultra-high-MW PE at a temperature below its m.p. CONSTITUTION:Ethylene is polymerized in the presence of a catalyst consisting of a solid catalyst ingredient containing at least Mg, Ti and/or V and an organometallic compound at a hydrogen concentration of 0-10mol% and a pressure of 0-70kg/cm<2>G at -20-110 deg.C to give 50-99wt% PE having an intrinsic viscosity of 12-50dl/g (at 135 deg.C in decalin). The PE is further polymerized at a hydrogen concentration of 35-95mol% and a pressure of 1-70kg/cm<2>G at 40-100 deg.C to give 50-0.5wt% PE having an intrinsic viscosity of 0.1-4.9dl/g, whereby an ultra-high-MW PE having an intrinsic viscosity of 5-50dl/g is obtained. The PE is then stretched 2-100 times at a temperature from 20 deg.C to the m.p. of PE.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to high strength and high modulus polyethylene materials (
Regarding the method for producing fibers, films, etc.), in more detail, high-strength, high-modulus polyethylene is produced by stretching ultra-high molecular weight polyethylene powder obtained by combining a specific catalyst and a specific polymerization method under specific conditions. Relating to a method of manufacturing the material.

Problems to be solved by conventional techniques and inventions So-called ultra-high molecular weight polyethylene, which has an extremely high molecular weight of about 1 million or more, is an engineering plastic with features such as excellent impact resistance, abrasion resistance, and self-lubricating properties. It is used in a wide range of fields such as food machinery, civil engineering machinery, chemical machinery, agriculture, mining, sports, leisure, etc., hoppers, silos, various gears, lining materials, ski linings, etc.

Ultra-high molecular weight polyethylene has a much higher molecular weight than general-purpose polyethylene, so if it can be highly oriented, it may be possible to obtain a stretched product with unprecedented strength and elasticity. Various changes are being considered. However, since ultra-high molecular weight polyethylene has an extremely high melt viscosity compared to general-purpose polyethylene, it is currently almost impossible to extrude it using normal methods, nor can it be highly oriented by stretching.

Ball-Smith, Peter Jahn-Lemstra, and others have developed a method for producing fibers with high strength and high elastic modulus by stretching a gel obtained from a decalin solution (dope) of ultra-high molecular weight polyethylene to a high magnification (Japanese Patent Application Laid-Open No. 56-15408). The polymer concentration in the dope is 3% by weight for those with a weight average molecular weight of 1.5 x 106, and 1% by weight for those with a weight average molecular weight of 4 x 106, which is only an extremely low concentration. It is extremely disadvantageous in terms of economic efficiency, such as the preparation method and handling of high-viscosity solutions.

In order to overcome the above-mentioned problems, various proposals have been made regarding methods for highly stretching and highly oriented ultra-high molecular weight polyethylene by methods such as extrusion, stretching or rolling below its melting point [JP-A-59] -187614, JP-A-60-15120, JP-A-60-97836, Proceedings of the Society of Polymer Science, Vol. 34, No. 4, p. 873 (1985), etc.]
.

However, in conventionally known methods, ultra-high molecular weight polyethylene is made into a dilute solution in a solvent such as xylene, decalin, kerosene, etc., and then cooled or isothermally crystallized to obtain a single crystal mat, which is then solid-phase extruded, stretched, etc. However, this method does not solve the problem that a large amount of solvent must be used when producing a single crystal mat.

-Although it is possible to solid-phase extrude and stretch ultra-high molecular weight polyethylene as it is without using a Banri crystal mat, the pressure during extrusion is extremely high in the commonly used one-stage polymer products, the extrusion speed is low, and the stretching ratio is also low. Unable to raise
The strength and modulus of elasticity of the obtained molded products were also low, and improvements were desired.

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have developed an ultra-high molecular weight polyethylene powder obtained by combining a specific catalyst and a specific polymerization method. The present invention was completed based on the discovery that a polyethylene material with high strength and high modulus of elasticity can be produced by drawing the polyethylene material in a solid state.

That is, in the present invention, the intrinsic viscosity in decalin at 135°C is 5 to 50 d/g, preferably 5 to 30 d/g.
g, and by stretching ultra-high molecular weight polyethylene powder obtained by at least the following two-step polymerization reaction at a temperature below the melting point of the polyethylene,
The present invention relates to a method of manufacturing high modulus polyethylene material.

(First step) Ethylene is polymerized in the absence of hydrogen or at a reduced hydrogen concentration using a catalyst consisting of a solid catalyst component containing at least Mg, TI and/or ■ and an organometallic compound, at 135°C in decalin. The intrinsic viscosity at is 12-5
A step of producing 50 to 99.5 parts by weight of polyethylene of 0 df/g.

(Second stage) A step of producing 50 to 0.5 parts by weight of polyethylene by polymerizing ethylene under a higher hydrogen concentration than in the first stage.

Effects of the Invention The ultra-high molecular weight polyethylene powder used in the method of the invention has the following effects (characteristics).

[1] Due to its excellent processability, it can be stretched at a high magnification, and highly strong and highly elastic polyethylene materials (fibers, films, etc.) can be produced in an extremely stable manner.

(2) Since it has excellent processability, it is possible to draw with less power and at high speed, and it is possible to produce fibers, films, etc. with high strength and high elastic modulus extremely economically.

A more specific method for producing the ultra-high molecular weight polyethylene powder used in the present invention will be described below.

First, in the first step, ethylene is mixed with a hydrogen concentration of 0 to about 10
by polymerization in a solvent or in the gas phase, in mol%
Intrinsic viscosity in decalin at 135℃ is 12-50d
50 to 99.5 parts by weight, preferably 70 to 99 parts by weight of polyethylene of 12 to 32 dE/g, preferably 12 to 32 dE/g.

The polymerization catalyst used at this time is at least Mg1T1.
It is composed of a solid catalyst component containing V and/or V and an organometallic compound (described later), and the polymerization pressure is 0 to 70.
Kg/Ct・G1 The polymerization temperature used is a temperature below the melting point of polyethylene, -20 to 110°C1, preferably 0 to 9
It is carried out at 0°C, more preferably at 20-80°C. As the polymerization solvent, an organic solvent inert to the Ziegler type catalyst is used. Specifically, saturated hydrocarbons such as butane, pentane, hexane, heptane, octane, cyclohexane,
Examples include aromatic hydrocarbons such as benzene, toluene, and xylene, and depending on the needs of the molding process of the obtained ultra-high molecular weight polyethylene, high-boiling point organic solvents such as decalin, tetralin, decane, and kerosene may also be used. .

Then, in the second stage, the hydrogen concentration is set to 35 to 95 mol %, and ethylene is subsequently polymerized to produce 50 to 0.5 parts by weight, preferably 30 to 1 part by weight, of polyethylene. The polymerization pressure is 0 to 70 kg/c-.G1 temperature is 40 to 100°C, preferably 60 to 90°C, and a catalyst may be added as necessary. Furthermore, the intrinsic viscosity of the polyethylene produced in the second stage is approximately 0.1 to 4. 9c
le/g (135°C, in decalin).

Copolymerizing α-olefins other than ethylene as a comonomer is undesirable because it tends to cause a decrease in the molecular weight of the resulting polymer;
~5 mol 96 of a small α-olefin may be used. As the α-olefin at this time, those used in the copolymerization of ethylene using a normal Ziegler type catalyst, such as propylene, butene-1,4-methylpentene-1, hexane-1, and octene-1, can be used. .

Furthermore, as a step after the third step, there is no problem in adding a higher molecular weight polymer component or a lower molecular weight polymer component as appropriate.

Next, the catalyst used for producing the ultra-high molecular weight polyethylene powder of the present invention is composed of a solid catalyst component containing at least Mg, Ti and/or V, and an organoaluminum compound.

Here, the solid catalyst component is one in which a titanium compound is supported on an inorganic solid compound containing magnesium by a known method.

Inorganic solid compounds containing magnesium include metal magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium chloride, etc., and double salts and complex oxides containing magnesium atoms and metals selected from silicon, aluminum, and calcium. Oxygenated compounds such as carbonates, chlorides or hydroxides, as well as these inorganic solid compounds, water, alcohols, phenols, ketones, aldehydes, carboxylic acids, esters, polysiloxanes, acid amides; metals Inorganic oxygenated compounds such as alkoxides and metal oxyaltates; thiols,
Organic sulfur-containing compounds such as thioethers; sulfur dioxide,
Inorganic sulfur-containing compounds such as sulfur trioxide and sulfur; benzene,
Monocyclic and polycyclic aromatic hydrocarbon compounds such as toluene, xylene, anthracene, and phenanthrene; treated or reacted with /\ halogen-containing compounds such as chlorine, hydrogen chloride, metal chlorides, and organic halides.

The titanium compounds supported on this inorganic solid compound include titanium halides, alkoxy halides,
These include alkoxides, halogenated oxides, etc., and tetravalent or trivalent titanium compounds are preferred. Specifically, the tetravalent titanium compound has the general formula % (where R represents an alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, X represents a halogen atom, and n represents 0≦n≦4), titanium tetrachloride, titanium tetrabromide, titanium tetrachloride, monomethoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxymonochlorotitanium, tetramethoxytitanium, monoethoxy Trichlorotitanium, jetoxydichlorotitanium, triethoxymonochlorotitanium, tetraethoxytitanium, monoisopropoxytrichlorotitanium, diisopropoxydichlorotitanium, triisopropoxymonochlorotitanium, tetraisopropoxytitanium, monobutoxytrichlorotitanium, dibutoxydichlorotitanium,
Examples include tetravalent titanium compounds such as monopentoxytrichlorotitanium, monophenokiditrichlorotitanium, diphenoxydichlorotitanium, triphenoxymonochlorotitanium, and tetraphenoxytitanium. Trivalent titanium compounds include trivalent titanium compounds obtained by reducing titanium tetrahalides such as titanium tetrachloride and titanium tetrabromide with hydrogen, aluminum, titanium, or organometallic compounds of metals from groups I to II of the periodic table. titanium compound - general formula % formula % (where R represents an alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, X represents a halogen atom, and I represents O<m<4 Examples include trivalent titanium compounds obtained by reducing a tetravalent alkoxy titanium halide represented by . Among these titanium compounds, tetravalent titanium compounds are particularly preferred. In addition, vanadium compounds include tetravalent vanadium compounds such as vanadium tetrachloride, trivalent vanadium compounds such as oxyvanadium trichloride and orthoalkylvanadate, and trivalent vanadium compounds such as vanadium trichloride. can be mentioned.

As a specific solid catalyst component, Japanese Patent Publication No. 51-3514
Publication No. 50-23864, Special Publication No. 51-
No. 152, Japanese Patent Publication No. 52-15111, Japanese Patent Application Publication No. 49-106581, Japanese Patent Publication No. 11710-1980, Japanese Patent Publication No. 51-153, Japanese Patent Application Publication No. 1987-959
Examples include those specifically exemplified in Publication No. 09 and the like.

In addition, as other solid catalyst components, reaction products of Grignard compounds and titanium compounds can also be used. Kaisho 57-7
Examples include those specifically described in Publication No. 9009, etc.
In addition, JP-A-56-47407, JP-A-57
A solid catalyst component in which an inorganic oxide is used together with an optionally used organic carboxylic acid ester as described in Japanese Patent Laid-open No. 187305 and Japanese Patent Application Laid-Open No. 58-21405 can also be used.

As the organoaluminum compound of the present invention, the general formula % formula % R2A name OR, RA name (OR)
x.

(Here, R represents an alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, and X represents a halogen atom,
R may be the same or different. ) Preferable compounds include triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminium chloride, diethylaluminium ethoxide, ethylaluminum sesquichloride, and mixtures thereof.

The amount of the organoaluminum compound to be used is not particularly limited, but it can usually be used in an amount of 0.1 to 1000 times the amount of the titanium compound.

Using the above catalyst system, the ultra-high molecular weight polyethylene powder of the present invention is synthesized.

Prior to the polymerization reaction of the present invention, by bringing the α-olefin into contact with the catalyst system of the present invention and then carrying out the polymerization reaction, the polymerization reaction can be carried out more stably than in the case of no treatment.

In addition, the melting point of polyethylene as used in the present invention refers to the ultra-high molecular weight polyethylene powder obtained as described above, which was measured by differential scanning calorimetry (DSC1 heating rate of 5°C/min, sample amount) without any particular heat treatment. 4-5Il1g) refers to the highest melting point (main peak temperature).

Further, in the present invention, it is important to use the obtained ultra-high molecular weight polyethylene as it is, and the effects of the present invention cannot be obtained if it is heated and melted once.

Stretching can be carried out by conventional methods such as extrusion stretching and tension stretching. However, in order to obtain a drawn product with a higher drawing ratio and tensile modulus, it is preferable to carry out two-step drawing, in which extrusion drawing is performed and then tension drawing is performed.

Examples of extrusion stretching include solid phase extrusion and roll rolling.

For solid-phase extrusion, for example, the ultra-high molecular weight polyethylene powder described above is placed in a cylinder of a solid-phase extrusion device equipped with a die at the bottom, and heated at a temperature of 20°C or higher, below the melting point of the ultra-high molecular weight polyethylene powder, preferably 90°C or higher. Pressure 0.01-0.1 at a temperature below the melting point of ultra-high molecular weight polyethylene powder
An example is a method of extruding at 20° C. or higher and below the melting point of the ultra-high molecular weight polyethylene powder, preferably 90° C. or higher and below the melting point of the ultra-high molecular weight polyethylene powder after pre-pressurizing at GPa. The stretching ratio (extrusion ratio) varies depending on the molecular weight of the polymer and the polymerization amount (composition ratio) of the first and second stages, but can be arbitrarily selected by changing the die diameter, and is usually 2 to 100 times, preferably It is carried out at a magnification of 3 to 50 times, more preferably 3 to 25 times.

Roll rolling can also be carried out in the same temperature range as solid phase extrusion according to a conventional method.

Examples of the tensile stretching performed subsequent to extrusion stretching include nip stretching and roll stretching, and among these, nip stretching is more preferred.

The temperature in the tensile stretching is 20° C. or higher and lower than the melting point of the ultra-high molecular weight polyethylene powder, preferably 90° C. or higher and lower than the melting point of the ultra-high molecular weight polyethylene powder.

The tensile speed varies depending on the molecular weight and composition ratio of the polymer, but is 1 to 100 a+m/a+in, preferably 5 to 50 a
+a/ It's a win.

The higher the stretching ratio, the higher the strength and the higher the modulus of elasticity. Therefore, it is desirable to increase the stretching ratio as much as possible.
It is possible to stretch twice as much.

By the above stretching method, a fiber or film having a tensile modulus of 120 GPa or more and a strength of 20 Pa or more can be obtained.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Examples Example 1 (a) Preparation of solid catalyst component 10 g of commercially available anhydrous magnesium chloride and aluminum triethoxide were placed in a 400 m stainless steel pot containing 25 stainless steel balls each having a diameter of 1/2 inch. After adding 1.7 g of titanium tetrachloride, ball milling was performed at room temperature for 5 hours under a nitrogen atmosphere, and then 2.2 g of titanium tetrachloride was added, and ball milling was performed for an additional 16 hours.

1 g of solid catalyst component obtained after ball milling contains 39a
+g of titanium was included.

(b) Polymerization A two-person stainless steel autoclave equipped with an induction stirrer was purged with nitrogen, and 1000a4 of hexane was added, followed by 1 mmol of triethylaluminum and 1 of the solid catalyst component.
0a+g was added, and the temperature was raised to 60°C while stirring. The vapor pressure of hexane brings the pressure of the system to 1.5 Kg/c12.gauge (hereinafter referred to as Kg/Ct-G), but ethylene is charged until the total pressure reaches 10 kg/(12.G) to initiate polymerization. Ethylene was continuously introduced into the autoclave from an ethylene measuring tank at 5°C so that the total pressure was 10 kg/c-G, and polymerization was carried out until the pressure in the measuring tank decreased by 7 kg/c-min. (Stage 1).

The intrinsic viscosity of the polymer at this time [η is 18.9 cl/g
Met. After that, quickly purge the ethylene in the system,
Hydrogen was charged until the total pressure reached 7 kg/cm2.G, and then ethylene was charged until the total pressure reached 10 kg/Cl2-G, and polymerization was started again at 60°C. Total pressure is 10K
Ethylene was continuously introduced at a rate of 1 g/clII2.G, and polymerization was carried out until the pressure in the metering tank decreased by 3 kg/c1 minute (second stage).

After the polymerization was completed, the polymer slurry was transferred to a beaker, and hexane was removed under reduced pressure to obtain 62 g of white polyethylene. The amount of polymer produced in the first stage was 70 parts by weight, and the amount of polymer produced in the second stage was 30 parts by weight.
η is 11.7dl! ,/g (in decalin, 135°C
)Met.

(c) A die with an inner diameter of 0.39 CI% and a length of IC1 was attached to an Instron capillary rheometer (cylinder inner diameter: 0.9525c+++) that had been partially modified by solid phase extrusion and tensile stretching, and the resultant obtained in (b) was attached. Approximately 10 g of polymer was filled.

After compressing at 90°C for 10 minutes at a pressure of 0.010 Pa, it was compressed at 90°C for 10 minutes at the same temperature. It was extruded at a constant speed of 0.6 cm/sin.

The deformation ratio (stretching ratio) is expressed as the ratio of the cross-sectional area of the cylinder to the cross-sectional area of the die, and in this case was 6 times. The pressure during extrusion is shown in Table 1.

The obtained extrudate was tested at 120°C using a tensile tester with a constant temperature bath.
Stretching was carried out at a crosshead speed of 40 °C/win, and it was possible to stretch the film 35 times.

1) The elastic modulus and strength of the stretched product were measured according to conventional methods. The results are shown in Table 1.

Comparative Example 1 A 2°C stainless steel autoclave equipped with an induction stirrer was purged with nitrogen, hexane was added at 1°C, 0011°C, 1 mmol of triethylaluminum, and Example 1(a).
110 liters of the solid catalyst component obtained in step 1 was added, and the temperature was raised to 60° C. with stirring. The vapor pressure of hexane is 1.5Kg/
cff12・G, but the total pressure of ethylene is 10Kg/C
The polymerization was started by filling the solution until it reached 112·G. Ethylene was continuously introduced so that the total pressure was 10 kg/c-・G, and polymerization was performed for 20 minutes to produce 72 g of white polyethylene.
I got it. The intrinsic viscosity [η] was 18.5 d/g.

When this polymer was subjected to solid phase extrusion according to Example 1(C), it was possible to extrude it at a deformation ratio of 4 times. When the film was then subjected to tensile stretching, it was possible to stretch it 22 times. Table 1 shows the elastic modulus and strength of the stretched product obtained. Compared to Example 1, the elastic modulus was lower and the extrusion pressure was extremely high.

Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1 except that the polymerization temperature was 85° C. to obtain 92 g of white polyethylene. The intrinsic viscosity [η] was 11.5 d/g. This polymer was subjected to solid phase extrusion at 6 times the extrusion according to Example 1 (C), and then subjected to tensile stretching. The stretching ratio was 13 times.

The elastic modulus and strength at this time are shown in Table 1.

Comparative Example 3 In Example 1(C), except that the polymer obtained in Example 1(b) was compression-molded at 200°C and 0.020 Pa for 15 minutes as a sample. The extrudate (stretching ratio: 6 times) carried out in the same manner was further stretched under tension, but it could only be stretched 2.5 times. The elastic modulus and strength of the stretched product are shown in Table 1.

Example 2 In Example 1(b), the pressure decrease in the ethylene metering tank in the first stage polymerization was set to 9.0 Kg/caP, and the pressure decrease in the ethylene metering tank in the second stage polymerization was set to 1.0.
Polymerization was carried out in the same manner as in Example 1(b), except that the weight was adjusted to Kg/c1 min, to obtain 63 g of white polyethylene. The amount of polymer produced in the first stage was 90 parts by weight, the amount of polymer produced in the second stage was 10 parts by weight, and the intrinsic viscosity of the entire polymer [η] was 15.1 d/g.

This polymer was subjected to solid phase extrusion (120
℃, stretching ratio 6 times) and tensile stretching (120° C., stretching ratio 28 times). Table 1 shows the elastic modulus and strength of the stretched product.
It was shown to.

Example 3 In Example 1(b), the pressure reduction in the ethylene measuring tank in the first stage polymerization was set to 8.0 Kg/ct, and the second
Pressure reduction in ethylene measuring tank during stepwise polymerization by 2.0K
Polymerization was carried out in the same manner as in Example 1(b), except that the ratio was adjusted to g/C-min, to obtain 62 g of white polyethylene.

The amount of polymer produced in the first stage was 80 parts by weight, and the amount of polymer produced in the second stage was 20 parts by weight, and the intrinsic viscosity of the entire polymer [η was 13. It was Od/g.

This polymer was subjected to solid phase extrusion (90°C) according to Example 1(C).
, stretching ratio 6 times) and tensile stretching (120° C., stretching ratio 32 times). Table 1 shows the elastic modulus and strength of the stretched product.

Example 4 (a) Preparation of solid catalyst component In Example 1 (a), aluminum triethoxide 1
．． 2.2g of aluminum triethoxide instead of 7g
A solid catalyst component was produced in the same manner as in Example 1(a) except that 3.2 g of silicon tetraethoxide was used. 1 g of the obtained solid catalyst component contains 32+a
It contained g of titanium.

(b) Using the same autoclave as in Polymerization Example 1(b), add 10,100 O of hexane, add 2 mmol of diethylaluminium chloride and 10 mg of the solid catalyst component,
The temperature was raised to 40°C while stirring. The vapor pressure of hexane is 1
．． It becomes 3Kg/ce2・G, but the total pressure of ethylene is 10K.
The polymerization was started by straining until g/c reached 1120G. The total pressure of the autoclave is 1 from the 5℃ ethylene measuring tank.
Ethylene was continuously introduced so that the pressure was 0 Kg/C12.G, and polymerization was carried out until the total pressure of 1J6 decreased by 5 Kg/c-min (first stage).

The intrinsic viscosity [η] of the polymer at this time is 26. 1 d,
It was 5/g.

After that, quickly purge the ethylene in the system and lower the temperature to 80.
The temperature was raised to .degree. C., hydrogen was charged to 8 kg/C-.G, and ethylene was charged until the total pressure reached 10 kg/cIN2.G to start polymerization again. Total pressure is 10Kg/Ct
-G, and the pressure in the measuring tank is 4K.
Polymerization was carried out until g/cs decreased by 2 minutes (second stage).

After the polymerization was completed, the polymer slurry was transferred to a beaker, and hexane was removed under reduced pressure to obtain 62 g of white polyethylene.

The amount of polymer produced in the first stage was 60 parts by weight, the amount of polymer produced in the second stage was 40 parts by weight, and the intrinsic viscosity [η] of the entire polymer was 12. 2 dJ! /g.

This polymer was subjected to solid phase extrusion (90°C) according to Example 1(c).
, stretching ratio 6 times) and tensile stretching (120° C., stretching ratio 32 times). Table 1 shows the elastic modulus and strength of the stretched product.

Example 5 (a) Preparation of solid catalyst component In Example 1 (a), 2.0 g of titanium tetrachloride was added: Vo (OC2H5)! 0.5g and titanium tetrachloride2. Example 1 (
A solid catalyst component was produced in the same manner as in a). 1 g of the obtained solid catalyst component contains 7.6 mg of vanadium and 3
It contained 0.6 mg of titanium.

(b) Polymerization Using the same autoclave as in Example 1(b), add 1000a+f of hexane, and add 1% triethylaluminum.
mmol and the solid catalyst component 10a+g were added, and the temperature was raised to 60°C while stirring.

The vapor pressure of hexane was 1.5 Kg/cIl12.G, but ethylene was charged until the total pressure reached 10 Kg/d-G to initiate polymerization. Ethylene was continuously introduced from the 5i ethylene measuring tank so that the total pressure of the autoclave was 10 Kg/-・G, and the pressure in the measuring tank was 7 Kg/C112.
Polymerization was carried out until the amount decreased (first stage).

The intrinsic viscosity [η] of the polymer at this time is 20. 5 dl
/g.

After that, quickly purge the ethylene in the system and remove hydrogen by 7K.
g/CI'・G and then add ethylene to a total pressure of 10
The pressure was increased to Kg/co+2.G, and polymerization was started again. The mixture was introduced continuously so that the total pressure was 10 Kg/cl.G, and polymerization was carried out until the pressure in the metering tank decreased by 3 KgZj (second stage).

After the polymerization was completed, the polymer slurry was transferred to a beaker, and hexane was removed under reduced pressure to obtain 60 g of white polyethylene.

The amount of polymer produced in the first stage was 70 parts by weight, the amount of polymer produced in the second stage was 30 parts by weight, and the intrinsic viscosity [η] of the entire polymer was 13.864/g.

This polymer was prepared by solid phase extrusion (110
℃, stretching ratio 6 times) and tensile stretching (120° C., stretching ratio 25 times). Table 1 shows the elastic modulus and strength of the stretched product.
It was shown to.

Example 6 The same procedure as Example 2 was carried out except that the polymerization temperature in the first stage was changed to 20°C, and [η] 30°1 d, e
/g of polymer was obtained. This polymer was prepared as Example 1(c)
Solid-phase extrusion (120° C., stretch ratio 6 times) and tensile stretching (120° C., stretch ratio 26 times) were performed according to the following. Table 1 shows the elastic modulus and strength of the stretched product.

Table 1

Claims (1)

[Scope of Claims] [1] Intrinsic viscosity in decalin at 135°C is 5 to 5
0 dl/g, and a method for producing a high-strength, high-modulus polyethylene material by stretching an ultra-high molecular weight polyethylene powder obtained by at least the following two-stage polymerization reaction at a temperature below the melting point of the polyethylene. (First step) Ethylene is polymerized in the absence of hydrogen or at a reduced hydrogen concentration using a catalyst consisting of a solid catalyst component containing at least Mg, Ti, and/or V and an organometallic compound. The intrinsic viscosity inside is 12~
A step of producing 50 to 99.5 parts by weight of polyethylene of 50 dl/g. (Second stage) A step of producing 50 to 0.5 parts by weight of polyethylene by polymerizing ethylene under a higher hydrogen concentration than in the first stage.