JPH07118324A - Ultrahigh-molecular-weight polyethylene - Google Patents

Abstract

PURPOSE:To provide a new ultrahigh-mol.-wt. polyethylene which has higher mol.wt. and density than those of the conventional ultrahigh-mol.-wt. polyethylenes. CONSTITUTION:An ultrahigh-mol.-wt. polyethylene having a wt.-average mol.wt. of 5X10<6> or higher and a density of 0.930-0.950g/cm<3> is obtd. by polymerizing ethylene in the presence of a chromium catalyst contg. a chromium compd., an amine or a metal amide, and an alkylaluminum compd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to ultra high molecular weight polyethylene.

[0002]

2. Description of the Related Art Ultrahigh molecular weight polyethylene is usually 10
It has a weight average molecular weight of 0 to 2,000,000 and is superior to general-purpose polyethylene in impact resistance, abrasion resistance, chemical resistance, tensile strength, and the like, and thus has attracted attention in various fields. Such properties are expressed largely depending on the molecular weight of ultrahigh molecular weight polyethylene. Therefore, if the molecular weight is further increased, further improvement in these physical properties is expected.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel ultrahigh molecular weight polyethylene having a higher molecular weight and a higher density than conventional ultrahigh molecular weight polyethylene. To provide.

[Means for Solving the Problems]

That is, the gist of the present invention is that the weight average molecular weight is 5 × 10 ⁶ or more and the density is 0.930 to 0.9.
It exists in an ultrahigh molecular weight polyethylene characterized in that it is 50 g / cm ³ .

The present invention will be described in detail below. First, the method for producing the ultrahigh molecular weight polyethylene of the present invention will be described. The ultrahigh molecular weight polyethylene of the present invention can be obtained, for example, by a polymerization reaction of ethylene using a catalyst system comprising at least a chromium compound and an amine or a metal amide and an alkylaluminum compound as a chromium catalyst.

The chromium compound used in the chromium-based catalyst is
It is represented by the general formula CrXn. However, in the general formula, X is any organic group or inorganic group or a negative atom, and n is 1 to
Represents an integer of 6, and when n is 2 or more, X may be the same or different from each other. The valence of chromium is 0 to 6, and n in the above formula is preferably 2 or more.

Examples of the organic group include various groups having usually 1 to 30 carbon atoms. Specific examples thereof include a hydrocarbon group, a carbonyl group, an alkoxy group, a carboxyl group, a β-diketonate group, a β-ketocarboxyl group, a β-ketoester group and an amide group. Examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group and an aralkyl group. Examples of the inorganic group include a chromium salt-forming group such as a nitrate group and a sulfate group, and examples of the negative atom include oxygen and halogen.

The preferred chromium compound is an alkoxy salt of chromium, a carboxyl salt, a β-diketonate salt, a salt of β-ketoester with an anion, or a chromium halide, specifically, chromium (IV) tert-butoxide. , Chromium (III) acetylacetonate, chromium (III)
Trifluoroacetylacetonate, chromium (III) Hexafluoroacetylacetonate, chromium (III) (2
2,6,6-tetramethyl-3,5-heptanedionate), Cr (PhCOCHCOPh) ₃ (provided that P is
h represents a phenyl group. ), Chromium (II) acetate, chromium (III) acetate, chromium (III) 2-ethylhexanoate, chromium (III) benzoate, chromium (III) naphthenate, Cr (CH ₃ COCHCOOCH ₃ ) ₃ , chromium (III) chloride , Chromium chloride, chromium bromide, chromium bromide, chromium iodide, chromium iodide, chromium fluoride, chromium fluoride and the like.

Further, a complex composed of the above-mentioned chromium compound and an electron donor can also be preferably used. The electron donor is selected from compounds containing nitrogen, oxygen, phosphorus or sulfur.

Examples of the nitrogen-containing compound include nitrile, amine and amide. Specific examples thereof include acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethylethylenediamine, diethylamine,
Examples include isopropylamine, hexamethyldisilazane, and pyrrolidone.

Examples of the oxygen-containing compound include esters, ethers, ketones, alcohols, aldehydes,
Specific examples include ethyl acetate, methyl acetate, tetrahydrofuran, dioxane, diethyl ether, dimethoxyethane, diglyme, triglyme, acetone, methyl ethyl ketone, methanol, ethanol, acetaldehyde and the like.

Examples of phosphorus-containing compounds include hexamethylphosphamide, hexamethylphosphorus triamide, triethylphosphite, tributylphosphine oxide, triethylphosphine and the like. On the other hand, examples of the sulfur-containing compound include carbon disulfide, dimethyl sulfoxide, tetramethylene sulfone, thiophene and dimethyl sulfide.

Therefore, as an example of a complex composed of a chromium compound and an electron donor, a chromium halide ether complex,
Ester complex, ketone complex, aldehyde complex, alcohol complex, amine complex, nitrile complex, phosphine complex,
Examples thereof include thioether complexes. Specifically, Cr
Cl ₃ / 3THF, CrCl ₃ / 3dioxane, C
_{rCl 3 · (CH 3 CO 2} n-C 4 H 9), CrCl 3
_{· (CH 3 CO 2 C 2} H 5), CrCl 3 · 3 (i-C
₃ H ₇ OH), CrCl ₃ · 3 [CH ₃ (CH ₂ ) ₃ C
H (C ₂ H ₅ ) CH ₂ OH], CrCl ₃ / 3pyri
_{dine, CrCl 3 · 2 (i} -C 3 H 7 NH 2),
[CrCl ₃ · 3CH ₃ CN] · CH ₃ CN, CrCl
_{3 · 3PPh 3, CrCl 2 ·} 2THF, CrCl 2 ·
2pyridine, CrCl ₂ · 2 [(C ₂ H ₅ ) ₂ N
H], CrCl ₂ · 2CH ₃ CN, CrCl ₂ · 2 [P
(CH ₃ ) ₂ Ph] and the like.

As the chromium compound, a compound soluble in a hydrocarbon solvent is preferable, and a β-diketonate salt of chromium,
Carboxylates, salts with anions of β-ketoesters, β
-Ketocarboxylic acid salts, amide complexes, carbonyl complexes, carbene complexes, various cyclopentadienyl complexes, alkyl complexes, phenyl complexes and the like. Examples of various carbonyl complexes of chromium, carbene complexes, cyclopentadienyl complexes, alkyl complexes, and phenyl complexes include Cr (CO) ₆ , (C ₆ H ₆ ) Cr (CO) ₃ ,
(CO) ₅ Cr (= CCH ₃ (OCH ₃ )), (CO)
₅ Cr (= CC ₆ H ₅ (OCH ₃ )), CpCrCl ₂
(Where Cp represents a cyclopentadienyl group), (
Cp * CrClCH ₃ ) ₂ (where Cp * represents a pentamethylcyclopentadienyl group), (CH ₃ ) ₂ CrC
1 and the like are exemplified.

The chromium compound can be used by supporting it on a carrier such as an inorganic oxide, but it is preferable to use it in combination with other catalyst components without supporting it on the carrier. That is, if a chromium-based catalyst is used in a specific contact mode according to a preferable polymerization reaction of ethylene described below, high catalytic activity can be obtained without supporting the chromium compound on the carrier. When the chromium compound is used without being loaded on the carrier, the loading on the carrier which involves complicated operations can be omitted, and the total amount of the catalyst used (the total amount of the carrier and the catalyst component) is increased by the use of the carrier. It is possible to avoid the problem.

The amine used for the chromium-based catalyst is a primary or secondary amine. Examples of primary amines include ammonia, ethylamine, isopropylamine, cyclohexylamine, benzylamine, aniline, naphthylamine, and the like, and secondary amines include diethylamine, diisopropylamine, dicyclohexylamine,
Dibenzylamine, bis (trimethylsilyl) amine,
Morpholine, imidazole, indoline, indole,
Pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,4
Examples include 5-tetrachloropyrrole, 2-acylpyrrole, pyrazole, pyrrolidine and the like.

The metal amide used for the chromium-based catalyst is 1
A metal amide derived from a primary or secondary amine, specifically, a primary or secondary amine and a group IA, I
An amide obtained by reaction with a metal selected from Group IA, Group IIIB and Group IVB. Specific examples of such metal amides include lithium amide, sodium ethylamide, calcium diethylamide, lithium diisopropylamide, potassium benzylamide, sodium bis (trimethylsilyl) amide, lithium indolide, sodium pyrrolide, lithium pyrrolide and potassium. Examples thereof include pyrrolide, potassium pyrrolidide, aluminum diethylpyrrolide, ethylaluminum dipyrrolide and aluminum tripyrolide.

Among the above amines or metal amides, 2
Primary amines, metal amides derived from secondary amines or mixtures thereof are preferably used. Secondary amines include pyrrole, 2,5-dimethylpyrrole, 3,4
-Dimethylpyrrole, 3,4-dichloropyrrole, 2,
3,4,5-Tetrachloropyrrole and 2-acylpyrrole are particularly preferable, and as the metal amide derived from a secondary amine, aluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrolide,
Particularly preferred are sodium pyrrolide, lithium pyrrolide and potassium pyrrolide. Among the pyrrole derivatives, those having a hydrocarbon group on the pyrrole ring are particularly preferable.

As the alkylaluminum compound used in the chromium-based catalyst, an alkylaluminum compound represented by the following general formula (1) is preferably used.

Embedded image R ¹ _m Al (OR ² ) _n H _p X _q (1)

In the formula, R ¹ and R ² usually have a carbon number of 1 to
15, preferably 1 to 8 hydrocarbon groups, which may be the same or different from each other, X represents a halogen atom, m is 0 <m ≦ 3, n is 0 ≦ n <3, p Is 0 ≦ p <
3 and q are numbers of 0 ≦ q <3, and
It represents a number that is m + n + p + q = 3.

Examples of the above-mentioned alkylaluminum compound include trialkylaluminum compounds represented by the following general formula (2), halogenated alkylaluminum compounds represented by the general formula (3), and alkoxy groups represented by the general formula (4). Examples thereof include aluminum compounds and alkylaluminum hydride compounds represented by the general formula (5). The meanings of R ¹ , X and R ² in each formula are the same as above.

[0022]

Embedded image R ¹ ₃ Al (2) R ¹ _m AlX _3-m (m is 1.5 ≦ m <3) (3) R ¹ _m Al (OR ² ) _3-m ( m is 0 <m <3, preferably 1.5 ≦ m <3) (4) R ¹ _m AlH _3-m (5) (m is 0 <m <3, preferably 1. 5 ≦ m <3)

Specific examples of the alkylaluminum compound include trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride, diethylaluminum ethoxide, diethylaluminum hydride and the like. Among these, trialkylaluminums are particularly preferable in that the amount of polymer by-products is small.

The ethylene polymerization reaction is carried out in a solvent using a catalyst system comprising the above catalyst components. The amount of chromium compound used is usually 0.1 × per liter of solvent.
The range is from 10 ^{−3 to 5} g, preferably 1.0 × 10 ^{−3 to 2} g. On the other hand, the amount of the alkylaluminum compound used is usually 0.1 mmol or more per 1 g of the chromium compound, but from the viewpoint of catalytic activity, it is preferably 5 mmol or more. And the upper limit is usually 50 mol. The amount of amine or metal amide used is 1
It is usually 0.001 equivalent or more per g, preferably 0.005 to 1000 equivalents, more preferably 0.01 to
The range is 100 equivalents.

The contact between ethylene and the chromium-based catalyst is preferably carried out in such a manner that the chromium compound and the alkylaluminum compound do not come in contact with each other in advance. According to such an aspect, 1-hexene useful as a raw material monomer for linear low density polyethylene (L-LDPE) can be produced as a by-product at the same time as the ultrahigh molecular weight polyethylene of the present invention.

The above-mentioned specific contact mode is specifically as follows.
When the amine is represented by "amine or metal amide", (1) a method of introducing ethylene and a chromium compound into a solution containing an amine and an alkylaluminum compound, and (2) ethylene and alkyl into a solution containing a chromium compound and an amine. Method of introducing aluminum compound (3) Method of introducing ethylene, amine and alkylaluminum compound into a solution containing a chromium compound, (4)
Ethylene in a solution containing an alkylaluminum compound,
It can be carried out by a method of introducing a chromium compound and an amine, (5) a method of introducing each of a chromium compound, an amine, an alkylaluminum compound and ethylene into a reactor simultaneously and independently. And each said solution is prepared using a reaction solvent.

In the above description, the phrase "a mode in which the chromium compound and the alkylaluminum compound do not come into contact with each other in advance" means not only at the start of the reaction but also at the subsequent supply of additional ethylene and catalyst components to the reactor. It means that such an aspect is maintained.

As the reaction solvent, a linear or alicyclic saturated hydrocarbon such as butane, pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, decalin, benzene, toluene, xylene, ethylbenzene, mesitylene, tetralin, etc. Aromatic hydrocarbons,
Chain chlorinated hydrocarbons such as chloroform, carbon tetrachloride, methylene chloride, dichloroethane, trichloroethane and tetrachloroethane, and chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene are used. They are,
Besides being used alone, it can also be used as a mixed solvent.

The reaction temperature is preferably in the range of 0 to 70 ° C. On the other hand, the reaction pressure is from normal pressure to 250 kg / c.
It can be selected from the range of m ² , but usually 100 kg / c
A pressure of m ² is sufficient. And the residence time is usually 1
The range is from minutes to 20 hours, preferably 0.5 to 6 hours. The reaction system may be a batch system, a semi-batch system or a continuous system, and it is preferable that hydrogen is allowed to coexist during the reaction because the catalytic activity is improved.

The ultrahigh molecular weight polyethylene of the present invention is recovered from the reaction solution using a known solid-liquid separation device. Then, the by-produced 1-hexene can be recovered by distillation purification means.

The ultrahigh molecular weight polyethylene of the present invention has a weight average molecular weight of 5 × 10 ⁶ or more and a density of 0.930.
˜0.950 g / cm ³ . Therefore, it has a higher molecular weight and a higher density than the conventionally known ultra-high molecular weight polyethylene. Due to such physical properties, the ultra high molecular weight polyethylene of the present invention has rigidity, impact resistance, and environmental stress crack resistance (ESCR resistance) as compared with conventionally known ultra high molecular weight polyethylene.
It has excellent physical properties such as

[0032]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, the weight average molecular weight was measured by GPC (gel permeshune chromatograph) (apparatus: Waters
"GPC 150CV" manufactured by the company, column: "G manufactured by TSK"
HHXL-HT "), the density is obtained by pelletizing the obtained polymer, and then using the density gradient tube method (JIS K-7112).
D method).

Example 1 A 2.4 liter autoclave heated and dried in a dryer at 150 ° C. was assembled while hot, and then vacuum nitrogen substitution was carried out. The autoclave was equipped with a stirrer equipped with a catalyst feed tube equipped with a rupture plate. n-heptane (98
0 ml), a solution of pyrrole (1.244 mmol) in n-heptane, triethylaluminum (8,000 mmo)
The n-heptane solution of 1) was charged on the barrel side of the autoclave, while the catalyst feed tube was solubilized with n-heptane of chromium (III) 2-ethylhexanoate (200 m).
g, 0.420 mmol). The total amount of n-heptane was 1 liter.

First, the autoclave is heated to 40 ° C.,
Next, ethylene was introduced from the catalyst feed pipe at 40 ° C. The rupture plate ruptured due to ethylene pressure, and the chromium compound was introduced into the autoclave barrel side to start the polymerization reaction of ethylene. Ethylene was introduced until the total pressure was 35 Kg / cm ² , then the total pressure was maintained at 35 Kg / cm ² and the temperature at 40 ° C. After 1 hour, ethanol was pressed into the autoclave to stop the reaction. After depressurizing the pressure of the autoclave and performing degassing, ultra high molecular weight polyethylene in the reaction solution was recovered by a filter. The weight average molecular weight of the obtained ultra high molecular weight polyethylene was 10.2 × 10.
⁶ , the density was 0.932 g / cm ³ . A GPC chart of ultra-high molecular weight polyethylene is shown in FIG.

Example 2 Ultrahigh molecular weight polyethylene was produced and recovered in the same manner as in Example 1 except that the reaction temperature was changed to 60 ° C. The obtained ultra high molecular weight polyethylene had a weight average molecular weight of 8.5 × 10 ⁶ and a density of 0.947.
It was g / cm ³ .

[0036]

According to the present invention described above, a novel ultra high molecular weight polyethylene having a higher molecular weight and a higher density than the conventional ultra high molecular weight polyethylene is provided, and the ultra high molecular weight polyethylene of the present invention is It exhibits excellent physical properties and can be suitably used in various fields.

[Brief description of drawings]

1 is a GPC chart of the ultra high molecular weight polyethylene obtained in Example 1. FIG.

Claims (2)

[Claims] 1. An ultra high molecular weight polyethylene having a weight average molecular weight of 5 × 10 ⁶ or more and a density of 0.930 to 0.950 g / cm ³ . 2. The ultrahigh molecular weight polyethylene according to claim 1, which is obtained by a polymerization reaction of ethylene using a catalyst system comprising at least a combination of a chromium compound and an amine or a metal amide and an alkylaluminum compound as the chromium-based catalyst.