JPH11968A - Rubber molded form - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber molded form wherein when tensile strength is large, and not less than two layers such as an insulation rubber layer and a conductive rubber layer are compounded to be integrated, an interlayer adhesion force is large. SOLUTION: The rubber molded form is provided wherein rubber materials (11, 12, 13) in which a rubber composition composed of base ribber containing 70 to 90 wt.% of ethylene and propylene copolymer and 2 to 30 wt.% of ethylene, propylene and diene copolymer, is chemically crosslinked to obtain 150 to 350% degree of swelling, are combinedly integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber molded article (rubber mold) having a composite integrated structure of two or more layers, such as an insulating layer and a conductive layer, for forming an intermediate connection portion and a terminal connection portion of a power cable. About.

[0002]

2. Description of the Related Art Rubber-moulded connection parts are used as connection members in intermediate connection portions and terminal connection portions of power cables. Examples of the rubber molded product used for this component are different depending on the type of the connection component, and include, for example, a stress cone, an insulating cylinder, a π-type or T-type molded product, and the like. This will be described with reference to the drawings. FIG. 1 shows a stress cone,
FIG. 2 shows an insulating cylinder, and FIG. 3 shows a π-type rubber molded product, each of which is shown in a sectional view. In FIG. 1, 1 is a conductive layer, 2
Indicates an insulating layer. 2 and 3, reference numeral 11 denotes an internal conductive layer, 12 denotes an insulating layer, and 13 denotes an external conductive layer. Figures 1-3
Is a through hole for a cable to be connected or a cable with a sheath removed. In any of the rubber molded products shown in FIGS. 1 to 3, the conductive layer made of conductive rubber and the insulating layer made of insulating rubber have a composite integrated structure.

[0003] In such a rubber molded product, ethylene rubber which is non-polar and has excellent electrical insulation properties is used as a base rubber.
Propylene copolymer (EPM) or ethylene propylene diene copolymer (EPDM) is used.
A conductive substance or an insulating substance is added to this base rubber to be used as a conductive rubber or an insulating rubber. In this rubber molded product, it is necessary that the conductive layer and the insulating layer are combined and integrated as described above, and not only the strength such as tensile strength but also the adhesiveness between both layers are important. If the adhesion between the two layers is weak and the separation occurs, the electric field concentrates on that portion, and the connection component is broken. This problem is particularly remarkable in the case of a π-type or T-type molded product having a bent portion in a rubber molded product (a molded product having a branched portion). For example, in the molded product shown in FIG. 3, the inner conductive layer, the insulating layer, and the outer conductive layer are laminated in a state in which the layers are bent at 90 ° at the portion A, and the molding pressure at the time of rubber crosslinking molding is applied to this portion. It is hard to take. Therefore, the adhesive strength between the layers is weak, and the interface between the layers is apt to be peeled off.
However, conventional rubber materials could not sufficiently cope with such a problem. For example, when a conductive rubber or an insulating rubber material using EPM as a base rubber is used, the adhesion between the insulating rubber layer and the conductive rubber layer is very strong, but the tensile strength of the insulating rubber material is low, and the connecting parts of the power cable are used. There was a problem that the tensile strength required as a material was not satisfied.
On the other hand, when a material of conductive rubber or insulating rubber using EPDM as a base rubber is used, the tensile strength is high, and the standard required as a connection component material of a power cable is sufficiently satisfied.
There is a problem that the adhesive force between the insulating rubber layer and the conductive rubber layer is low, and separation occurs at the interface between the two layers.

[0004]

Accordingly, the present invention provides
It has high tensile strength.
It is an object of the present invention to provide a rubber molded product having a large adhesive strength between two layers when the composite is integrally formed in layers. Further, the present invention is a composite of a power cable having two or more layers, such as an insulating rubber layer and a conductive rubber layer, having a large adhesive strength between the two layers, hardly causing interface separation between the two layers, and having a high tensile strength. An object of the present invention is to provide a rubber molded product suitable for connection parts.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to overcome the above-mentioned drawbacks of the conventional rubber molded product for power cable connecting parts, and as a result, have found that ethylene-propylene copolymer and ethylene-propylene By using a rubber material having a swelling degree of 150 to 350% by chemically crosslinking a rubber composition using a base rubber obtained by mixing a diene copolymer with a predetermined ratio, the insulating rubber layer and the conductive rubber It has been found that the adhesion between the layers can be made very strong and the above object can be achieved, and the present invention has been made based on this finding. That is, the present invention provides (1) a rubber composition comprising a base rubber containing 70 to 98% by weight of an ethylene / propylene copolymer and 2 to 30% by weight of an ethylene / propylene / diene copolymer by chemically crosslinking. Swelling degree 150 ~
A rubber molded product characterized by combining and integrating 350% of rubber materials, and (2) a rubber material used for an intermediate connection part or a terminal connection part of a power cable, wherein the rubber material is a composite of an insulating layer and a conductive layer. The present invention provides a rubber molded product according to the above (1), which has an integrated structure.

In the present invention, the degree of swelling is determined by the following equation (1).

[0007]

(Equation 1)

In the formula, W1 is 15 mm or less in width and 40 m in length.
m or less, the test piece of the crosslinked rubber having a thickness of 2 mm or less is immersed in 800 ml of cyclohexane solvent, and is the mass of the test piece after being left at room temperature for 48 hours. W2 is the above test piece at 80 ° C. for 18 hours or more. It is the mass of the test piece after vacuum drying. In the present invention, "composite and integral" means that two or more rubber layers are firmly adhered so as not to cause peeling to form a rubber molded product.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a mixed rubber of an ethylene / propylene copolymer (EPM) and an ethylene / propylene / diene copolymer (EPDM) is used. The ethylene / propylene copolymer alone has a lower crosslink density than the ethylene / propylene / diene copolymer, and the degree of swelling of the crosslinked rubber material exceeds 350%. On the other hand, when the ethylene-propylene-diene copolymer is used alone, the cross-linking density is high and the swelling degree is less than 150% when cross-linked, so the above mixture is used. The EPM used in the present invention preferably has an ethylene component content of 45 to 60% by weight, and the EPDM preferably has an ethylene component content of 55 to 70% by weight. When the ethylene component content is within these ranges, the balance of various properties such as mechanical properties and moldability becomes better.

The ethylene / propylene rubber composition used in the present invention has an ethylene / propylene copolymer of 70 to 70%.
98% by weight, preferably 75 to 95% by weight, the ethylene / propylene / diene copolymer is 2 to 30% by weight,
Preferably it is 5 to 25% by weight. When a base polymer containing more than 98% by weight of ethylene / propylene copolymer and less than 2% by weight of ethylene / propylene / diene copolymer is used as the insulating rubber material, the tensile strength of the base material required for the power cable connection component material is reduced. Insufficient or insufficient strength. If the ethylene / propylene copolymer is less than 70% by weight and the ethylene / propylene / diene copolymer exceeds 30% by weight, two layers (insulating layer and conductive layer)
This is because the adhesive strength becomes low. Examples of the diene component of the ethylene / propylene / diene copolymer include dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and 1,4-hexadiene.

In the present invention, a rubber material having a swelling degree of 150 to 350% is obtained by subjecting the rubber composition to a chemical crosslinking treatment. The chemical crosslinking treatment method itself can be performed by a conventionally known method. For example, it can be carried out by subjecting a rubber composition to a predetermined amount of an organic peroxide to a crosslinking reaction at 120 to 150 ° C. for 1 hour or more. Examples of the organic peroxide compounded as a crosslinking agent in the rubber composition in the present invention include dialkyl peroxides such as 1,3-bis (t-butylperoxyisopropyl) benzene and dicumyl peroxide; Peroxy ketals such as 1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane are exemplified. These crosslinking agents may be used in a range where the degree of swelling is in the range of 150 to 350%, and the amount of use is usually in the range of 2 to 5% by weight based on the rubber composition.

In the present invention, the swelling degree of the rubber material is set to 150.
To 350%, preferably 200 to 300%. When the degree of swelling is large, the cross-linking density of the rubber material is small because it absorbs the solvent and swells.On the other hand, when the degree of swelling is small, the cross-linking density of the rubber material is large because it does not absorb the solvent and does not swell. Indicates that When the degree of swelling is less than 150%, the crosslink density of the rubber material is high and the material strength is high, but the movement of the polymer segment of ethylene / propylene rubber becomes inactive, so that the rubber layer and the insulating layer adhered at the time of cross-linking molding become The rubber polymer chains between the two layers such as the conductive layer are hardly entangled, and the adhesive strength is reduced. When the degree of swelling exceeds 350%, the crosslinking density of the rubber material is low,
Since the polymer segment of the ethylene / propylene rubber actively moves, the entanglement of the rubber polymer chain between the two layers at the time of cross-linking molding increases, and the adhesive strength becomes strong. However, since the crosslink density is low, the material strength is low, and in the case of an insulating rubber material, the tensile strength required for a power cable connection component cannot be satisfied.

Various fillers or additives can be added to the rubber material used in the present invention. A conductive rubber material can be obtained by adding a predetermined amount of carbon black to the rubber material, and an insulating rubber material can be obtained by adding a filler such as calcium carbonate or calcined clay.
That is, in the rubber material used in the present invention, various fillers (for example, talc, clay, calcium carbonate, silica, etc.), carbon black (for example, thermal black, acetylene black, furnace black, etc.), a crosslinking aid (for example, For example, sulfur, quinone dioxime, etc.), crosslinking accelerators (eg, aldehyde ammonias, aldehyde amines, thioureas, guanidines, thiazoles, sulfenamides, thiurams, dithiocarbamates, xanthates, etc.), aging Inhibitors (eg, aminoketones, aromatic secondary amines, monophenols, bisphenols, polyphenols, benzimidazoles, etc.), lubricants (eg, stearic acid, stearates, paraffins, etc.), softeners (eg, Paraffin, naphthenic or allo System process oils, etc. oligomer hydrocarbon), coupling agent (e.g. a silane, titanate, etc.), metal oxides (e.g. zinc oxide,
You may mix | blend a flame retardant (for example, aluminum hydroxide, magnesium hydroxide, a chlorine-type or a bromine-type flame retardant, etc.), and a flame-retardant auxiliary agent (for example, antimony trioxide etc.). In the present invention, it is preferable to use either a conductive rubber material or an insulating rubber material by mixing carbon black and a filler. In addition, the rubber material of the present invention can use a calcined clay or the like which does not have a problem of a decrease in electric characteristics due to moisture absorption as a filler, and can obtain a necessary tensile strength. The carbon black content of the conductive rubber material is usually in the range of 20 to 30% by weight. The amount of the filler can be selected in accordance with the type of the filler as long as the desired tensile strength can be achieved and the rubber material does not become brittle. The amount is not particularly limited, but is usually 30 to 50% by weight. It is. With respect to other compounding agents, the compounding amount can be selected so that the desired effect can be exhibited without impairing the properties of the rubber material.

The production of the rubber molded product according to the present invention can be carried out according to a conventional method. For example, first, a mixture of the ethylene-propylene copolymer and the ethylene-propylene-diene copolymer and a compounding agent excluding the crosslinking agent are mixed with a Banbury mixer or the like, and then a predetermined amount of the crosslinking agent is mixed with an open roll or the like. To obtain an uncrosslinked rubber material. In order to obtain a crosslinked rubber molded product from this rubber material, for example, an uncrosslinked rubber material is placed in advance in a hollow portion of a mold in which the product shape is engraved, and a predetermined pressure is applied at a predetermined temperature at a predetermined temperature by a press machine. After applying, it can be performed by a compression molding method of taking out from a mold. Further, the uncrosslinked rubber material whose viscosity has been reduced by blending the necessary amount of the above-described softener is pressed into the hollow portion of the mold in which the product shape is engraved, and a predetermined pressure is similarly applied at a predetermined temperature for a predetermined time. A transfer molding method or an injection molding method in which a crosslinked molded product is obtained by taking out from a die and obtaining a crosslinked molded product can also be carried out.

The rubber molded product of the present invention is preferably used for a rubber molded connection part having a composite integrated structure of an insulating layer and a conductive layer, which forms an intermediate connection portion and a terminal connection portion of a power cable. In this case, the shape of the power cable connection component is not particularly limited, and it can be used in any of a T-type, a π-type, a stress cone type, an insulating cylindrical type, and the like. Because of its high performance, it can be suitably used for connection parts having a shape to which a molding pressure is not easily applied, for example, a T-shaped or π-shaped shape having a 90 ° bend. An example in which the rubber molded product of the present invention is applied to a power cable connection component will be described with reference to the drawings, but the present invention is not limited to this. FIG. 4 is a partial cross-sectional view showing an example in which the insulating cylinder of FIG.
With the sheath stripped off, the insulating tube 15 is inserted into one of the cable outer conductors 14 to connect the cable conductors 16 and 1 to be connected.
After electrically connecting the cable conductors 6 completely with each other with the conductive sleeve 17, the insulating cylinder 15 is slid to the connection portion 18 to which the cable conductor is connected. In the figure, 19 is a cable insulation, and 20 is a conductive tape. FIG. 5 is a partial cross-sectional view showing an example in which the π-shaped molded product of FIG. 3 is applied. This connecting part has a fitting 23 and a conductor 23 inside each connecting part. 4 except that four cables can be connected simultaneously.
It is similar to that of Here, the same symbols as those in FIGS. 3 and 4 indicate the same components.

[0016]

Next, the present invention will be described in more detail with reference to examples. Examples 1 to 6 and Comparative Examples 1 to 4 The rubber compositions having the compositions shown in Tables 1 and 2 were kneaded using a Banbury mixer, and Examples 1 to 3 and Comparative Examples 1 and 2 were each run at 150 ° C. for 15 minutes. Examples 4 to 6 and Comparative Examples 3 and 4 were subjected to a crosslinking treatment at 150 ° C. for 10 minutes and formed into sheets or connection parts. The units of the compositions in Tables 1 and 2 are% by weight, and the total of the ethylene / propylene copolymer and the ethylene / propylene / diene copolymer is 1%, respectively.
This is the value when 00 is set. The ethylene / propylene copolymer is Mitsui EPT0045 (trade name, manufactured by Mitsui Petrochemical Co., Ltd.), and the ethylene / propylene / diene copolymer is Mitsui E
PT1045 (trade name, manufactured by Mitsui Petrochemical Co., Ltd.) was used.
The following tests were performed on the molded articles of the insulating rubber (Examples 1 to 3 and Comparative Examples 1 and 2) and the conductive rubber (Examples 4 to 6 and Comparative Examples 3 and 4) thus obtained, and evaluated. did. The results are shown in Tables 1 and 2.

Tensile Strength A tensile test was performed using a sheet having a thickness of 2 mm in accordance with JIS K6301. From the same sheet as swelling degree, length 40mm, width 15mm, thickness 2
mm, a test piece was immersed in 800 ml of a cyclohexane solution, the mass (W1) after standing at room temperature for 48 hours was measured, and then the test piece was vacuum-dried for 18 hours or more (W2). ) Was measured, and the degree of swelling was determined according to the above equation (1).

Adhesion test 1 The thickness of the insulating rubber of Examples 1 to 3 and Comparative Examples 1 and 2 was 4 mm.
The uncrosslinked conductive rubbers of Examples 4 to 6 are placed on Examples 1 to 3 and the uncrosslinked conductive rubbers of Comparative Examples 3 and 4 are placed on Comparative Examples 1 and 2 at 150 ° C. for 10 minutes. Cross-linked, width 15
An adhesive test specimen having a thickness of 100 mm, a length of 100 mm, and a thickness of 6 mm (insulating layer 4 mm, conductive layer 2 mm) was prepared. FIG. 6 shows a cross-sectional view of this test piece. In FIG. 6, 2 is an insulating layer, 1 is a conductive layer, and one end of each of 1, 2 was pulled by a tensile tester, and the adhesive strength was calculated by the following equation (2).
Further, the peeled state at that time was observed.

[0019]

(Equation 2)

Adhesion Test 2 A π-type connection part as shown in FIG. 5 was prepared, and the adhesion between the conductive layer and the insulating layer was evaluated. The connecting parts were prepared by first crosslinking the conductive rubber layers of Examples 4 to 6 and Comparative Examples 3 and 4 at 125 ° C. for 1 hour on a conductor, and then working Examples 1 to 3 for Examples 4 to 6. Of Comparative Example 3 or 4
Was obtained by winding the uncrosslinked insulating rubber of Comparative Example 1 or 2 at 135 ° C. for 1 hour (thickness: conductive layer 5 mm, insulating layer 3 mm). Cut this into slices, especially 90
° The adhesiveness of the bent portion was visually evaluated.

[0021]

[Table 1]

[0022]

[Table 2]

The value specified as a so-called electric power standard value (standard value specified by an electric power company or the like) as a tensile strength required for a power cable connecting component material is 3.9 MPa. In Comparative Examples 1 and 3 in which the ethylene / propylene copolymer alone was used as the base rubber and the degree of swelling exceeded 350%, the adhesiveness between the insulating layer and the conductive layer was so strong that the insulating layer was cut, but the tensile strength was low. It is less than 3.9 MPa of this regulation. Further, in Comparative Examples 2 and 4 in which the ethylene-propylene-diene copolymer alone had a swelling degree of less than 150%, the tensile strength exceeded 3.9 MPa, but the adhesion between the insulating layer and the conductive layer was low. It can be seen that it cannot be applied to a connection part having a shape having a curved portion as shown in FIG. On the other hand, Examples 1 to 6 which are the rubber molded products of the present invention satisfy the standard value of the tensile strength, and have a 90 ° bending portion where peeling is likely to occur at both interfaces between the conductive layer and the insulating layer. Also, it can be seen that both layers are firmly adhered without peeling, and that both tensile strength and adhesiveness are satisfied in a well-balanced manner.

[0024]

The rubber molded product of the present invention satisfies the tensile strength required for power cable connection parts, and when combined as an insulating layer and a conductive layer, both layers adhere very strongly. Since it does not peel off, a high quality power cable connection component can be obtained. In particular, 90% of π-type and T-type connection parts are used.
In the part bent at °, usually, the molding pressure at the time of cross-linking molding is less likely to be applied, so the adhesion between the layers is weak and peeling is likely to occur, but according to the rubber molded product of the present invention, such molding pressure is less likely to be applied Since the adhesiveness is high even at the part and does not peel off, there is an excellent effect that it can be suitably used for a π-type or T-type power cable connection part.

[Brief description of the drawings]

FIG. 1 is a sectional view of a stress cone.

FIG. 2 is a sectional view of an insulating cylinder.

FIG. 3 is a sectional view of a π-shaped molded product.

FIG. 4 is a partial cross-sectional view showing a use state of a power cable connecting part to which an insulating tube is applied.

FIG. 5 is a partial cross-sectional view showing a use state of a power cable connection component to which a π-shaped molded product is applied.

FIG. 6 is a sectional view of an adhesive test piece prepared in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive layer 2 Insulating layer 4 Cable penetration hole 11 Inner conductive layer 12 Insulating layer 13 Outer conductive layer 14 Outer cable 15 Insulation cylinder 16 Cable conductor 17 Conductive sleeve 18 Connection part 19 Cable insulation 20 Conductive tape 21 Cable 22 Fitting connection Tool 23 conductor

Claims (2)

[Claims] An ethylene / propylene copolymer 70 to 9
8% by weight of ethylene / propylene / diene copolymer 2
A rubber molded product characterized in that a rubber composition comprising a base rubber containing 30% by weight and a rubber material having a swelling degree of 150 to 350% are compositely integrated with each other by a chemical crosslinking treatment. 2. The rubber molded product according to claim 1, wherein the rubber material has a composite integrated structure of an insulating layer and a conductive layer, which is used for an intermediate connecting portion or a terminal connecting component of the power cable.