JPS6210112A - Ethylene copolymer and its production - Google Patents

Abstract

PURPOSE:To obtain a copolymer excellent in dielectric breakdown characteristic, long-term performance retention and flexibility and containing no metallic catalyst residues, by polymerizing ethylene containing an ethylenically alpha,beta-unsaturated acid halogenated alkylated phenyl ester in specified conditions. CONSTITUTION:Ethylene containing 0.0015-3mol% (based on the total) ethylenically alpha,beta-unsaturated acid halogenated alkylated phenyl ester of the formula is polymerized at a reaction temperature >=120 deg.C and a reaction pressure >=500kg/cm<2> in the presence of a free radical-generating initiator. In the formula, R is H or -CH3, X is a halogen, Y is a 4-18 C alkyl, n is 0 or 1, m is 1-4 and l is 1-4. Among the monomers of the formula, those having Cl or Br as the halogen are preferable and those having Br are particularly preferable. With respect to the polymer structure of the ethylene copolymer, a random copolymer or a graft copolymer obtained by grafting a monomer of the formula onto an ethylene polymer skeleton is desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a novel ethylene copolymer and a method for producing the same.

The novel ethylene copolymer of the present invention serves as a material for a ring cable having excellent dielectric breakdown properties such as withstand voltage properties, particularly electrical tree properties, water tree properties, and impulse breakdown properties.

Hirobo uJl Cross-linked polyethylene based on low-density polyethylene has excellent electrical properties and heat resistance, so Cv
Although it is widely used as a cable insulation material, dielectric breakdown occurs under ultra-high voltages, and there is a need for materials with higher performance.

For this reason, many studies have been made to improve the insulation value II characteristics under ultra-high voltages.

For example, the presence of impurities such as pores, water, and metals causes charge concentration and deteriorates dielectric breakdown characteristics. Therefore, impurity removal technology is being considered mainly for materials for ultra-high voltage cables, and Clean polyethylene, which does not contain any contaminants, and dry crosslinking technology, which does not create pores, have been developed. By making full use of these technologies, 275
Even KV cables have been put into practical use.

However, such cross-linked polyethylene insulating ring capacitors for high voltage applications have the disadvantage that the insulation thickness becomes extremely thick, and therefore materials with even better withstand voltage characteristics are desired.

If the material itself has the function of avoiding charge concentration, it can be manufactured with a thin material.Therefore, attempts have been made to use calcium stearate, various aromatic compounds, etc. as voltage stabilizers, but methods using these additives have not been successful. , additives may bleed out, causing problems in long-term performance retention (for example, Japanese Patent Publication No. 48-24809, West German Patent No. 12)
48773, French Painting Patent No. 1464601, etc.).

Fl! In view of these current circumstances, the present inventors focused on developing an ethylene copolymer with excellent dielectric breakdown properties, long-term performance retention, flexibility, and no metal catalyst residue. Successfully developed a polymer.

ill, the present invention first relates to ethylene and the general formula (I), (wherein, R is H or -CHa, 0 or 1, m is 1~
a copolymer of an ethylenically type α,β unsaturated acid with a halogenated alkylated phenyl ester group unit, which is an integer of 4 and L represents an integer of 1 to 4, respectively. o, o o s~1
Second, the ethylene copolymer containing 0 mol % of the general formula (
I), (wherein R is H or -C) Lt, X is a halogen atom, Y is an alkyl group of 04 to 18, n is 0 or 1
, m is an integer of 1 to 4, and t is an integer of 1 to 4).

A method for producing an ethylene copolymer, comprising polymerizing ethylene containing 15 to 3 mol% (based on the total amount) at a reaction temperature of 120° C. or higher and a reaction pressure of 5 oon/- or higher using a free radical generating initiator. It provides:

The new ethylene copolymer of the present invention has all the performance requirements as an insulating material for electrical cables, such as voltage resistance, long-term performance retention, flexibility, no metal residue, and cable coating properties. It satisfies the above requirements and shows excellent performance as an insulating material for high-voltage cables.

DETAILED DESCRIPTION OF THE INVENTION The ethylene copolymer of the present invention is a novel copolymer that has not been described in any literature. , Y is an alkyl group of 04 to 18, n is 0 or l, m is an integer of 1 to 4, t
each represents an integer from 1 to 4), the monomer represented by the general formula (1) is contained in an amount of o, o o s to 10 mol%, preferably o, o
The content is approximately 5 mol %.

Examples of the monomer represented by the above general formula (1) include dibromononylphenyl methacrylate, dichlorononylphenyl methacrylate, dibromooctylphenyl methacrylate, dichlorooctylphenyl methacrylate, dibromostearyl phenyl methacrylate, dichlorostearylphenyl methacrylate, cyfuromonylphenyl Acrylate, dichlorononylphenyl acrylate, dibromooctylphenyl acrylate,
Dichlorooctylphenyl acrylate, dibromostearyl phenyl acrylate, tribromononyl methacrylate, tribromononyl acrylate, tribromostearyl methacrylate, tribromostearyl acrylate, bromodinonylphenyl methacrylate, bromodioctyl phenyl methacrylate, bromodioctyl phenyl acrylate, difluorononylphenyl methacrylate , diiodinated nonylphenyl methacrylate, dibromononylbenzyl methacrylate, dichlorononylbenzyl methacrylate, and the like.

Among the monomers represented by general formula (I), it is preferable that the halogen atom is Ct or Br, and Ct or Br is particularly preferable.

There are no particular restrictions on the polymer structure of the ethylene copolymer, but a random copolymer or a graft copolymer in which a monomer represented by the above general formula (1) is grafted onto the ethylene polymer main chain is desirable.

The ethylene copolymer of the present invention comprises ethylene and general formula (1)
In addition to the monomers represented by the formula, other monomers can be added to modify the resin, and the modified monomers can be contained up to 10 mol %.

As the modifying comonomer, monomers known to be copolymerizable with ethylene can be used.

For example, vinyl esters such as vinyl acetate and vinyl propionate, acrylic esters such as ethyl acrylate, methyl acrylate, and butyl acrylate, methacrylic esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate, and ethylene such as acrylic acid and methacrylic acid. They are α, β unsaturated acids.

The novel ethylene copolymer of the present invention has a number average molecular weight of 10
00 or more. When the molecular weight is less than 1000, long-term performance deteriorates. Preferably, the molecular weight is 3000 or more.

The ethylene copolymer of the present invention is a very unique polymer that exhibits excellent dielectric breakdown properties and flame retardancy, so it can be applied to a variety of other uses in addition to the above-mentioned use as an insulating material for ring capaples. It is.

For example, it can be used as an insulating material for wires and cables by extrusion molding, or it can be formed into a film by a T-die method or an inflation method and used as an insulating film, a general-purpose film, and a flame-retardant film.

The ethylene copolymer of the present invention can also be used to produce various molded products by blow molding, injection molding, extrusion molding, etc. As a specific example of extrusion molding, a laminated film can be obtained by extrusion coating a film made of another plastic or a material other than plastic (metal foil, paper, cloth, etc.).

Since the ethylene copolymer of the present invention falls under the category of thermoplastic resin, it may be used with other thermoplastic resins such as polyethylene, polypropylene ethylene-vinyl acetate copolymer, etc., as commonly used for this type of resin material. It can also be used by blending it with coalescents, petroleum resins, waxes, stabilizers, band-1 inhibitors, anti-aging agents, voltage stabilizers, carbon black, ultraviolet absorbers, synthetic rubber or natural rubber, lubricants. , an inorganic filler, etc. can also be blended and used.

Further, it can also be used as a crosslinked product by a chemical crosslinking agent, electron beam, or graft copolymerization of vinyltrimethoxysilane or the like. In that case, commonly used chemical crosslinking agents such as dicumyl peroxide and percadox can be used, and furthermore, it is not impossible to use anti-aging agents and other additives in combination.

The ethylene copolymer of the present invention is produced by subjecting a predetermined unit to copolymerization conditions, but it can be produced using a known high-pressure polyethylene production apparatus using radical polymerization.

The catalyst used in this radical polymerization is a compound that generates free radicals, such as oxygen, dialkyl peroxide such as ditertiary butyl peroxide, tertiary butyl cumyl peroxide, dicumyl peroxide, etc.
acetyl peroxide, isobutyl peroxide,
Diacyl peroxide such as octanoyl peroxide, diimpropyl peroxydicarbonate, di-2-
Peroxy dicarbonates such as ethylhexyl peroxydicarbonate, peroxy esters such as tert-butyl peroxy isobutyrate, tert-butyl peroxy bivalate, tert-butyl peroxy laurate, methyl ethyl ketone peroxide, cyclohexanone peroxide, etc. ketone peroxide, 1
, 1 Bistersya butyl peroxycyclohexane,
Peroxy ketals such as 2,2-bistaryabutyl peroxyoctane, hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxinide, and azo compounds such as 2,2-azobisisobutyronitrile.

This polymerization is preferably carried out in a continuous manner. As the polymerization apparatus, a continuous stirring seed reactor or a continuous hole tube reactor, which are commonly used in high-pressure radical polymerization of ethylene, can be used.

The polymerization can be carried out as a single-zone process using these single reactors, but many reactors can be used in series, possibly with connected condensers, or several internal sections can be used for each zone process. A single reactor can also be used, effectively divided into zones. In each zone method, monomers are added to each reactor or reaction zone in such a way that the reaction conditions in each zone are different to control the properties of the polymer obtained in each reactor or reaction zone. It is common to adjust the composition, catalyst concentration, molecular weight regulator concentration, etc. When multiple reactors are connected in series, in addition to the combination of two or more seed reactors or two or more front reactors, one or more seed reactors and one or more front reactors are used. Combinations with type reactors can also be used.

In the present invention, ethylene and the monomer represented by general formula (I) are supplied to the above-mentioned polymerization apparatus, and radically polymerized in the presence of the above-mentioned catalyst. In this case, ethylene and the general formula (
The proportion of the monomer represented by formula (1) is appropriately selected so that the ethylene copolymer of the present invention has a desired composition, but the polymerization ability of the monomer represented by general formula (1) is compared to that of ethylene. Since the monomer represented by general formula (1) is large in size, the monomer represented by general formula (1) is usually polymerized in the state of ethylene containing 0.0015 to 3 mol%, preferably 0.0015 to 2 mol%, based on the total amount in the polymerization system. .

The polymerization pressure employed is a pressure in excess of 5ooy/-, preferably in the range of 1000 to 4000 #/-. Further, the polymerization temperature is at least 120°C, but preferably in the range of 150 to 300°C.

The polymer produced in the reactor or reactors can be separated from unreacted monomer and processed as in the production of conventional high pressure polyethylene. The mixture of unreacted monomers is mixed with an additional amount of the same monomers,
Repressurize and circulate to the reactor. The additional amount of monomer added as described above is of a composition that returns the composition of the mixture to that of the original polymerization system, and generally this additional amount of monomer is separated from the polymerization vessel. It has a composition roughly equivalent to that of a polymer.

In the present invention, the reactor is preferably a seed reactor in order to obtain a copolymer with a uniform composition.

The catalyst is usually dissolved in a solvent with a small chain transfer effect and directly injected into the reactor using a high pressure pump. Concentration is 0.5-3
0% by weight is preferred.

Suitable solvents include, for example, hexane, heptane, white spirit, hydrocarbon oils, cyclohexane, toluene, higher branched chain saturated fatty acid hydrocarbons, and mixtures of these liquids.

In addition, when injecting the monomer represented by general formula (I), it is possible to dissolve it alone or in a solvent with a small chain transfer effect,
Inject directly into the reactor with a high pressure pump. Examples of this solvent include aromatic compounds such as ethyl benzoate, toluene, and methyl benzoate, and aliphatic esters such as ethyl acetate.

In high-pressure radical polymerization, a chain transfer agent is generally used to adjust the molecular weight, except in special cases.

In the present invention, all chain transfer agents used in ordinary high-pressure radical polymerization can be used.

For example, alkanes such as ethane, propane, butane, hexane, heptane, alkenes such as propylene, butene, hexene, alcohols such as ethanol, methanol, propatool, ketones such as acetone, methyl ethyl ketone, acetaldehyde, propionaldehyde, etc. Aldehydes, such as aldehydes, and many of the compounds used in the low-pressure method can be used.

These gaseous substances are injected into the suction side of the compressor, and the liquid substances are injected into the reaction system by a pump.

The ethylene copolymer of the present invention produced in the reactor is separated from monomers in a separator according to the conventional method of high-pressure radical polymerization, and becomes a product as it is. This product may be used as it is, or may be subjected to various post-treatment steps such as those already used for products obtained by high-pressure radical polymerization.

The novel ethylene copolymer of the present invention can be produced by the following method in addition to the high-pressure radical polymerization method described above. That is, commercially available high-pressure polyethylene, low-pressure polyethylene, etc., such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer , ethylene-methyl acrylate copolymer, and ethene W are grafted together.

In this graft production method, a known graft is used in such a proportion that the ethylene copolymer of the present invention is obtained, and the organic peroxide is added thereto and mixed in a super mixer or the like, and then a uniaxial, The mixture is heated and kneaded using a twin-screw extruder or a Banbury mixer, and conditions commonly used for graft modification of polyethylene and the like can be used for this method.

Experimental Examples Example 1 Using a stirring autoclave type continuous reactor with an internal volume of 1.5 L, 30 #/hour of ethylene and 10 #/hr of dibromononylphenyl methacrylate (abbreviated as DBNPMA) were used.
9 dissolved in toluene at a ratio of 0 t/L
00 sl/hour, propylene total 4001 hours, a solution of tertiarypterperoxyisoptylate dissolved in n-hexane at a rate of 1 t/l as a catalyst was continuously supplied at a rate of 5ooy/hour, and the polymerization pressure was 260 aAy. /aAz
An ethylene copolymer was produced by polymerizing at a polymerization temperature of 220°C.

The obtained ethylene copolymer has MFR=2.7r/10
min, number average molecular weight 20,100, DBNP in polymer
The content of MA was 0.07 mol.

Example 2 Using the same reactor as Example 1, DBNPMA was
o t7t dissolved in toluene at a ratio of 9.7
1/hour, without using propylene, the same catalyst used in Example 1 was dissolved in n-hexane at a ratio of St/l.
An ethylene copolymer was produced by polymerizing in the same manner as in Example 1 except that the polymerization temperature was 218° C. at 50 MIZ.

The obtained ethylene copolymer has MFR=4.0f/10
minute, number average molecular weight 18,900. 17) DB in polymer
The content of NPMA was 0.75 mol%.

Reference Examples 1 to 3 (Evaluation of characteristics of uncrosslinked body) Examples 1 and 2
The properties of these polymers were determined using the ethylene copolymer of the present invention produced in 1999 and commercially available high-pressure polyethylene [Yukan ZF30Rj (manufactured by Mitsubishi Yuka Corporation, MFR = 1.0 f/10 min]) as sample polymers. We conducted an evaluation.

The measurement method used for this characteristic evaluation is as follows.

(1) Molecule &: 'y' By permeation chromatography method.

(2) Comonomer content: Based on infrared spectroscopy.

(3) MFR: JIS K6760 (4) Density: J1 white K6760 (5) Gel fraction: JIS C3005 (6) Electric tree properties: Sample polymer was prepared into a 5-thickness sheet at 160°C and 150 g/d. Each molded piece was cut into a size of 20m x 20m. A needle with a diameter of 1 m and a tip radius of curvature of 5 μm was inserted into the cut piece for 15+ m. On the other hand, a test piece was prepared by applying silver paste to the opposite side to where the needle was inserted (see Figure 1).

An alternating current voltage was applied to this test piece at a voltage increase rate of 500 V/see, and the voltage at which electric tree generation started was measured.

(7) Water tree properties: Each sample polymer was molded into a 5-thickness sheet under the conditions of 160°C and 150 kf/-.
I cut it out. Insert a syringe needle with a diameter of 20 mm into this cut piece.
After inserting the injection needle, 15 minutes were pulled out while injecting distilled water, and a 10-inch-wide aluminum foil was pasted on the side opposite to where the injection needle was inserted to make a test piece (see Figure 2).
.

After applying an AC voltage of 60 Hz and 10 KV to this test piece for 50 hours, the average growth length of water trees was observed using an optical microscope.

(8) Impulse high-pressure fracture characteristics: For the crosslinked material, a 502°C thick press molded sample was used, and for the non-crosslinked material, a 30 μm thick inflation molded sample was used (using a 40m∆ extruder inflation molding machine, molding temperature 150°C, blow ratio Constructed under the conditions of 1.5 filJ3
Impulse high-pressure fracture characteristics were measured using a 0 μm blown film).

The measurement was carried out using 4 negative standard impulse voltages, starting from a voltage of approximately 50% of the expected breakdown level, increasing the voltage by stepping up 2KV/3 times, and measuring the voltage at which breakdown occurred.

(9) Nonflammability: Oxygen index was measured according to JIS K7201.

Table 1 shows the characteristics evaluation results of the ethylene copolymers of the present invention produced in Examples 1 and 2 and Yucalon ZF30RJ.

(Leaving space below) Reference Examples 4 to 6 (Evaluation of properties of crosslinked products) Samples for evaluation of properties of crosslinked products were prepared by setting the temperature of the Brabender mixer to 110°C, adding 100 parts by weight of each sample polymer, and adding dichloromethane as a crosslinking agent. 2 parts by weight of Milperoxide and 3 parts by weight of Santonox RJ O as an anti-aging agent were added and kneaded for 5 minutes, and the mixed wire sample was heated at 130°C.
502℃ and 5mm thick using a hot plate press maintained at
After pre-forming to a thick thickness, these are also pressed into one piece using a hot plate press.
A crosslinked product was obtained by heating and pressing at 80° C. and 100 kg/− gauge pressure for 20 minutes.

Using this crosslinked body, test pieces similar to those in Reference Examples 1 to 3 were created and used.

The results of this characteristic evaluation are shown in Table 2.

(The following is a blank space) From the results shown in the above-mentioned reference examples, the novel ethylene copolymer of the present invention has extremely excellent electrical tree properties, water tree properties, and impulse rupture properties, which are particularly important as materials for high-voltage ring cables. Furthermore, although a crosslinked product is usually used as an electric cable, it is clear that this crosslinked product has particularly excellent water tree properties and impulse breakage properties compared to an uncrosslinked product, and this excellent effect is due to the ethylene This is the first copolymer obtained.

[Brief explanation of the drawing]

Figure 1 shows the second part of the test piece used to measure the electrical tree characteristics.
The figure is a schematic diagram of a test piece used for measuring water tree characteristics. Patent Applicant Mitsubishi Yuka Co., Ltd. Agent Patent Attorney Hidetoshi Furukawa Agent Patent Attorney Masahisa Hase Figure 1

Claims (2)

[Claims] (1) Ethylene and the general formula (I), ▲Mathematical formulas, chemical formulas, tables, etc.▼...(I) (In the formula, R is H or -CH_3, X is a halogen atom, and Y is C_4_~_1_8 , n is 0 or 1, m is an integer of 1 to 4, and l is an integer of 1 to 4), halogenated alkylated phenyl ester of ethylenically type α,β unsaturated acid An ethylene copolymer containing 0.005 to 10 mol% of halogenated alkylated phenyl ester group units. (2) General formula (I), ▲Mathematical formulas, chemical formulas, tables, etc.▼...(I) (In the formula, R is H or -CH_3, X is a halogen atom, and Y is an alkyl of C_4_ to_1_8 a halogenated alkylated phenyl ester of an ethylenically-type α,β-unsaturated acid, represented by 0.0015~3
The reaction temperature of ethylene containing mol% (based on the total amount) was 12%.
A method for producing an ethylene copolymer, comprising polymerizing at 0° C. or higher and a reaction pressure of 500 kg/cm^2 or higher using a free radical generating initiator.