JPS6044763B2 - Manufacturing method for electric wires and cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electric wires and cables using an electrical insulator made of an ethylene propylene rubber mixture that has high mechanical strength, electrical properties, and processability.

Ethylene propylene rubber is widely used as an electrical insulation material for electric wires and cables because it has superior electrical properties, heat resistance, and weather resistance compared to natural rubber and butyl rubber.

However, the frame strength is low, and the electrical properties are not sufficient for use in high voltage fields.

In order to compensate for these shortcomings, we have mainly used combination drugs,
Efforts have been made to improve the composition, but it has not been possible to meet the high requirements.

In addition, it is extremely difficult to improve the appearance of extrusion when the extrusion process is low. The present invention aims to improve these drawbacks and provide a manufacturing method that can yield wires and cables that have excellent extrusion processability and extruded appearance, and have sufficient mechanical strength and electrical properties even when the content of filler is reduced. It was done for a purpose.

In order to achieve this purpose, silicon is added to 100 parts by weight of ethylene propylene rubber having an ethylene content of 78 to 85 mol% based on the ethylene propylene content in the polymer, a crystalline index of 8 to 16, and a molecular weight distribution index of 3 or more. It has been found that it is extremely effective to extrusion coat the outer periphery of the conductor with a mixture containing not more than 12 parts of filler selected from acid salts, carbonates, and carbon black, and then vulcanize the mixture.

Here, the ethylene propylene rubber in the present invention is:
It means a binary copolymer of ethylene and propylene, and a multi-component copolymer consisting of ethylene, propylene, and at least one type of non-conjugated diene. The method for producing ethylene propylene rubber used in the present invention will be described below. The polymerization catalyst has the general formula VO(0
R) NX3-n (R = alkyl group having 6 to 12 carbon atoms, n
= an integer from 1 to 3, X = chlorine, bromine), and is produced by the reaction of various alcohols with vanadium oxytrichloride.

The present catalyst system may be one obtained by distilling and purifying and isolating the above-mentioned reactant after the reaction, or the reaction solution may be used as it is as a vanadium catalyst component without performing any of these treatments. The number of carbon atoms in the alkyl group of the alcohol used is 6 to 12.
It is. Specifically, n-hexyl alcohol, secondary hexyl alcohol, n-heptyl alcohol, 2◆
Examples include ethylhexanol, n-octyl alcohol, and dodecyl alcohol. Among these, primary alcohols that contain substantially no water are preferred.
The amount of these alcohols used may be extremely small, and it is sufficient to add and react 0.01 to 5 moles, preferably 0.5 to 3 moles of alcohol per mole of vanadium oxytrichloride. On the other hand, as the organoaluminum compound which is another component of the polymerization catalyst, any compound that is generally used as a catalyst for producing EPM or EPDM can be used. , X=chlorine, bromine). Kill aluminum seiki halide is preferred.

In the polymerization of the present invention, the amount of vanadium component of the catalyst relative to the solvent is 0.6 x 10-3 to 2
．． ~x10-3 gram atom/'solvent, A1/v (gram atomic ratio) of 2 to 6, and polymerization temperature of 20 to 60°C. Uno is preferable. Examples of the non-conjugated diene which is the third component of the EPDM of the present invention include 1,4-hexadiene, methyltetrahydroindene, synchropentadiene, 5-ethylidene-2-norbonnene, and the like.

Examples of the polymerization solvent of the present invention include aliphatic hydrocarbons such as pentane, hexane, and heptane, cycloaliphatic hydrocarbons such as cyclohexane and methylcyclohexane, benzene,
Aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as tetrachloroethylene and chlorobenzene, or mixtures thereof are used. The crystal index was determined as follows.

Low-density polyethylene with a specific gravity of 0.920 (
YF-30) manufactured by Mitsubishi Yuka was selected, and the endothermic area that could be absorbed in the temperature range of 20°C to 120°C was determined using a traveling calorimeter.

Next, the endothermic area of a given ethylene propylene rubber was determined in the same manner, and the relative value when the endothermic area of the standard substance was taken as 100 was calculated as the crystallization index. The values shown here are obtained using a scanning type working calorimeter DT-20S manufactured by Shimadzu Corporation, with a heating rate of 200C/Minl and a chart speed of 20TnI.
Measurement was carried out under the conditions of n/Minl sensitivity ±5 μV and sample weight of 20 m9. Moreover, the molecular weight distribution index was determined as follows. In the present invention, the Q value used as the molecular weight distribution index of ethylene propylene rubber is defined as (where Mw represents the weight average molecular weight and MN represents the number average molecular weight).

The Q value was measured as follows in accordance with 1 Journal of Japan Rubber Association, Vol. 45, No. 2, p. 105 (1972). (1)
Creation of 10gK-Ma+1-GPC count correlation diagram Using several types of monodisperse standard polystyrene with known molecular weights,
[η] of the polymer and GPC (GelPermeat
iOnChrOmatOgraph) count is measured, and a correlation diagram between IOg[η] and GPC count is created.

Next, based on the relationship of 10g[η] ・M=10gK-Ma+1, from the above correlation diagram, 10gK-Ma+1-GP
Create a C count correlation diagram.

(2) Sample preparation Sample EPM or EPDM (hereinafter referred to as rubber) is cut into small pieces and weighed at 70n1g using a direct-reading chemical balance.

This sample rubber was placed in an Erlenmeyer flask, and 10 m9 of an anti-aging agent (1r NOxlO76 manufactured by Ciba-Geigi Co., Ltd.) was added.
Add 25 ml of tetrahydrofuran. Add this mixture to 5
The mixture was heated at 5°C for 3 minutes, the pressure was released, the mixture was allowed to cool, and the polymer was shaken at 25°C for 3 minutes to dissolve the polymer. then 8
The gel content was filtered through a wire mesh with NO. 4 Filter paper, GA-200 glass filter 1, NO. 5. Filter through a filter with a sandwiched filter paper.

Next, a 0.5μ millibore filter, a GA-200 glass filter, and a NO. 4. Filter the mixture through a filter with a sandwich of filter paper.

The filtrate is subjected to GPC.

(3) GPC measurement conditions Find the molecular weight M.

(5) From the M of each fraction determined in (4) above, calculate the molecular weight of the Mi:i fraction and the number of molecules of the Ni:i fraction.

Hitherto, various ethylene propylene rubbers having only one of the characteristics of high ethylene content and wide molecular weight distribution have been provided, but no rubber has been found that has both characteristics.

Therefore, it could not be expected to have high mechanical strength and electrical properties as an insulating material for electric wires and cables. In the present invention, by increasing the amount of ethylene far more than before and allowing the presence of microcrystals formed from this ethylene chain,
As a result of numerous experiments with the aim of improving these properties, we found that products with an ethylene content of 78 to 85 mol% and a crystalline index of 8 to 16 achieved the specified purpose without losing rubber elasticity. I found out what I can do.

The reason why the range is limited in this way is that only in this range, the microcrystals of the ethylene chain form physical crosslinking points, which do not restrict the movement of the polymer molecules in the amorphous part too much and form the rubber as a whole. This is thought to be because the conditions are appropriately distributed to maintain the same characteristics. If it exceeds this range, the number of crystals will naturally increase, restricting molecular movement and causing a loss of rubbery properties, and below this range, the effect of improving properties will be small. However, simply limiting the amount of ethylene and the amount of crystals in this way does not provide sufficient extrudability.

It has been discovered that when these conditions are satisfied and the molecular weight distribution index is defined in the range of 3 or more, the extrusion workability, particularly the extrusion appearance, can be extremely improved even with low filling. In other words, if the molecular weight distribution index is less than 3, the fluidity properties will be poor and the extrusion appearance will be rough, making it difficult to obtain a smooth product.Although this upper limit is not particularly specified, it is practically limited to about 6 for synthesis purposes.
Anything larger than that is difficult to manufacture. The vulcanizing agent used in the present invention is dicumyl peroxide, 1,3-bis(
Organic peroxides represented by tert-butyl peroxy, isopropyl) benzene are most suitable, and these can be used alone or in combination with sulfur, ethylene dimethacrylate, diallyl phthalate, P-quinone dioxime, etc. Good to use.

Also, sulfur-promoter systems such as sulfur-tetramethylthiuram disulfide-zinc dibutyldithiocarbamate-mercaptobenzothiazole, sulfur-tetraethylthiuram disulfide-N,N'' dithiobis(morpholine), zinc sulfur-dimethylthiuram disulfide-mercaptobenzothiazole,
Mercaptobenzothiazole and the like can be used, and other resin or quinoid vulcanization is also possible. From the viewpoint of mechanical strength and electrical properties, it is necessary to use a filler selected from silicates such as talc and clay.

The amount of filler added is 12 parts by weight per 100 parts by weight of the base rubber.
The characteristics of rubber can be sufficiently maintained by setting the range not to exceed the saliva volume area.

A softener is not necessarily necessary because the ethylene propylene rubber according to the present invention has particularly excellent processability, but if it is added, petroleum-based process oil is suitable, paraffin-based, paraffin-based, etc.
Either naphthene type or aroma type may be used.

The antioxidant is amine-based N,N''-diphenylno-P-
Phenyl diamine, phenyl-α-naphthylamine,
Phenol-based 2,2″-methylenebis(4-methyl-6-Tert -butylphenol), 2,6-di-Tert-butyl-4-methylphenol, 4,4″-thiobis(6-Tert-butyl-3
-methylphenol), imidazole-based 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, and other antiaging agents used for rubbers can be used alone or in combination.

In addition to these, stabilizers typified by zinc oxide, dispersants typified by stearic acid, lubricants typified by paraffin are added as compounding agents normally used in ethylene propylene rubber, and surface treatment agents for fillers are added as appropriate. , tackifiers, or voltage stabilizers or radiation resistance improvers, such as polycyclic aromatic oils, or water trituration inhibitors,
Alternatively, a flame retardant may be mixed.

Furthermore, other polymers such as polyethylene and polypropylene may be added to adjust processability and physical properties.

Next, the electrical insulator used in the present invention will be explained based on formulation examples.

(Each formulation example is expressed in weight%) Formulation example 1 Ethylene propylene rubber 100 (ethylene content 78 mol%, ethylidene norbornene content 1 mol%, crystalline index 9, molecular weight distribution index 3.8) dicumyl peroxide 2.5 zinc oxide
5 stearic acid
12-mercaptobenzimidazole 1 Paraffin oil
5 talc
100 formulation example 2 ethylene propylene rubber
100 (ethylene content 80 mol%, crystal index 101, molecular weight distribution index 3.9) dicumyl peroxide 2.5 zinc oxide 5 stearic acid
12-Mercaptobenzimidazole 1 Talc
60 blending example 3 Ethylene propylene rubber 100 (ethylene content 81 mol%
, ethylidenenorbornene content 1 mol%, crystalline index 1
1. Molecular weight distribution index 4.0) Dicumyl peroxide
2.5 zinc oxide
5 stearic acid
12-mercaptobenzimidazole 1 Talc 60 Formulation example 4 Ethylene propylene rubber 10
0 (ethylene content 84 mol%, synchropentadiene 0.5 mol%, crystalline index primary molecular weight distribution index 3.2) dicumyl peroxide 2.5 zinc oxide 5 stearic acid
12-mercaptobenzimidazole 1 Paraffin oil
5 clay (fired)
60 Compounding example 5 Ethylene propylene rubber
100 (ethylene content 85 mol%, crystalline index 13.5 molecular weight distribution index 4.8) sulfur
0.3 Zinc dimethyldithiocarbamate 1.0 Tetramethylthiuram disulfide 1.0 Zinc oxide
5 stearic acid
12-mercaptobenzimidazole 1 Talc 30 Comparative example 1 Ethylene propylene rubber 100
(Ethylene content 70 mol%, ethylidene norbornene content 1 mol%, crystalline index 2, molecular weight distribution index 2.2)
Dicumyl peroxide 2.5 Zinc oxide 5 Stearic acid
12-mercaptobenzimidazole 1 Paraffin oil
5 talc
120 Comparative Example 2 Ethylene Propylene Rubber
100 (ethylene content 78 mol%, ethylidene norbornene content 1 mol%, crystalline index 7, molecular weight distribution index 3.2) dicumyl peroxide
2.8 Zinc oxide
5 stearic acid 12
-Mercaptobenzimidazole 1 talc
60 Comparative Example 3 Ethylene propylene rubber 100 (ethylene content 81 mol%, ethylidene norbornene content 1 mol%, crystalline index 11, molecular weight distribution index 2.2) dicumyl peroxide 2.5, zinc oxide 5 stearic acid
12-mercaptobenzimidazole 1 Paraffin oil
5 talc
After uniformly kneading each of the above 60 compounds using a 150rwLφ mixing roll at a temperature of 80 to 100°C, the mixture was press-vulcanized at a gauge pressure of 80kg/d1 at a temperature of 180°C and formed into an insulating sheet with a thickness of 2Tnm. Characteristics were measured.

However, only the AC breakdown voltage was measured by making sheets with a thickness of 0.35. Further, processability was evaluated by observing the extrusion appearance using an extruder. These results are shown in Table 1.

Tensile properties Using a Schottupa type tensile tester
Measured at a tensile speed of 500Tf$L/Min.
Constant Tampel No. 3 test piece.

AC breakdown voltage: Uses a buried electrode with a thickness of 0.35T0n.
500v'/Sec in transformer oil
Measured by voltage rise rate.

Attach a metal foil electrode with a dielectric loss tangent of 60φ,
Temperature 20℃, Voltage 500V1 Shuttle
Measured with a ring bridge.

Extrusion appearance 50W0fL extruder (L/D=1.2,
Compression ratio = 2, die diameter = 4wrm)
Extrusion temperature: 100℃, screw
Extrude at a rotation speed of 50 revolutions/Mjn.

Next, examples of the electric wire of the present invention will be described.

An insulated wire was manufactured using a mixture of Formulation Example 3 and Comparative Example 1 as a representative composition of the present invention, and the characteristics were compared. That is, in the formulations of Formulation Example 3 and Comparative Example 1, after kneading each component except for the crosslinking agent dicumyl peroxide using a Banbury (capacity 200'), 550 TIUrLφ
Using a mixing roll, dicumyl peroxide was added to prepare a mixture.

Next, this mixture was extruded and coated to a thickness of 4wt on a conductor with a cross-sectional area of 38T0L2 provided with a tape-shaped internal semiconductive layer.
An electric wire was manufactured by steam vulcanization under continuous vulcanization conditions at atmospheric pressure for 5 minutes. Table 2 shows the characteristics of this wire.

AC breakdown voltage: Initially charged at 30K/10 minutes, then
Boosting impulse breakdown voltage at a rate of 5KV/1 Gin: 60K/3 times at first, then 5KV
Step-up DC breakdown voltage: 60KV/5 minutes at first, then 5KV/5
Step-up insulation resistance at the speed of minutes: direct polarization method, applied voltage DC 180V
Dielectric loss tangent: Schuring bridge, applied voltage curve combination example 1~
The insulating sheet used in the present invention shown in No. 5 has extremely excellent performance that far exceeds the conventional characteristic range represented by Comparative Example 1, and has more than double the tensile strength and about 1.5 times the breakdown voltage. It shows the value.

Furthermore, as seen in Formulation Examples 2 to 5, it is recognized that even if the amount of filler is less than half of the conventional amount, a good extrusion appearance can be obtained and processability similar to that of plastics can be obtained. In addition, the dielectric loss tangent is affected by the polar components and impurity ions contained in the filler, so it is desirable to use as little filler as possible.However, even with low filling, processability is good and there is no problem in practical use, so this value is It is noteworthy that it can be reduced to a value of 0.2% or less, which is sufficient for high voltage applications. The excellent performance described above can only be achieved if the limiting conditions of the ethylene propylene rubber in the present invention are satisfied, and if these conditions are violated, these effects are lost as in the following comparative example. Comparative Example 1 is a conventional type of ethylene propylene rubber, and the ethylene content, crystalline index, and molecular weight distribution index are all far below the range of the present invention. Although the extrusion appearance is considerably improved by using a large amount of filler, the tensile strength and electrical properties are significantly inferior to those of the present invention. Comparative Example 2 is a curved example in which the amount of ethylene is within the limited range but the crystalline index is out of range. The tensile strength is considerably lower than that of the invention, proving the feature of the invention that unless both the ethylene content and the crystalline index simultaneously satisfy the predetermined ranges, the effect of improving properties is small.

Comparative Example 3 has a molecular weight distribution index of 2.2, which is smaller than the limited range of the present invention.

Due to the presence of crystals, it can be said that it is equivalent to the present invention in terms of tensile strength and electrical properties, but the extrusion appearance is poor and it cannot be put to practical use. This shows that the molecular weight distribution has a significant influence, and that the limiting value specified in the present invention is an essential condition for improving processability.As is clear from Table 2, the electric wire according to the present invention was Compared to conventional wires, the breakdown voltage is definitely improved by more than 20%, and the insulation resistance is also good.
Furthermore, the dielectric loss tangent is as small as 0.14%, which is superior to oil-immersed cables, which exhibit ideal performance as ultra-high voltage insulation, and the tensile strength is approximately twice as strong, making it suitable for use as rubber electric wires. It can be said that it has revolutionary performance both electrically and mechanically.

As described above about the present invention, by using ethylene propylene rubber having a specific range of ethylene content, crystalline index, and molecular weight distribution index, it is possible to eliminate the drawbacks or insufficient treatment of conventional rubber without losing the original properties of rubber. We were able to develop electric wires and cables using insulators with significantly improved mechanical strength, electrical properties, and workability.

Considering future trends in the field of electrical insulation for electric wires and cables, we believe that the industrial value of the present invention is extremely large.

Claims (1)

[Claims] 1 Ethylene propylene rubber having an ethylene content of 78 to 85 mol% relative to the ethylene propylene content in the polymer, a crystalline index of 8 to 16, and a molecular weight distribution index of 3 or more
12 parts by weight of filler selected from silicates
A method for manufacturing electric wires and cables, which comprises extruding and coating the outer periphery of a conductor with an admixture containing no more than 1 part by weight, and vulcanizing the mixture.