JP2000133047A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition ideal as a connection part and a terminal for an electric wire and a cable having a small content of processed oil, a low viscosity, a low stickiness and an excellent molding processability. SOLUTION: An insulation rubber composition contains a base rubber and an inorganic filler. The base rubber is constituted of 50-90 wt.% of a first ethylene-propylene rubber having Mooney viscosity ML 1+4 (100 deg.C) of 10 or less and 50-10 wt.% of a second ethylene-propylene rubber having Mooney viscosity ML 1+4 (100 deg.C) of 11-25. An amount to be formulated of the inorganic filler is 20-100 pts.wt. against 100 pts.wt. of the base rubber. The composition contains the processed oil of 6 wt.% or less against the whole composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition,
In particular, the present invention relates to an insulating rubber composition and a conductive rubber composition used as connection parts and terminal parts of electric wires and cables.

[0002]

2. Description of the Related Art Insulated rubber materials used for insulated wires, cables, their connections, and terminal parts are based on ethylene-propylene rubber in terms of electrical characteristics and heat resistance, and various kinds of fillers, aging prevention. A rubber composition is used in which an auxiliary agent such as an agent, a process oil or a metal oxide is compounded.

[0003] The connection of electric wires and cables and terminal parts are manufactured by methods such as compression molding, transfer molding and injection molding. For example, in compression molding,
First, an unvulcanized rubber sheet having a thickness of usually about 1 to 10 mm is cut into a predetermined size, and is preformed into a product shape. Next, the preform is put into a mold, and 120 to 17
A product having predetermined dimensions and physical properties can be obtained by being sandwiched between hot plates of a press machine heated to 0 ° C., pressurized and heated.

In this production method, the unvulcanized rubber sheet is usually produced by winding a wide sheet of about 500 to 800 mm in a roll shape. As shown in FIG. 1, the rubber sheet roll is usually obtained by winding a rubber sheet 2 around a shaft 1 together with a separator 3 in a roll shape. After a predetermined amount of rubber sheet is drawn from the rubber sheet roll, the rubber sheet is cut so as to have an arbitrary width and length in order to preform it into a shape close to the shape of the product. The manufacturing method of transfer molding is basically the same as compression molding, except that rubber is put into a pot provided in the mold without performing pre-molding, and this is injected into the mold by pressing pressure. It is. For this reason, it is necessary to cut the rubber to the size to be put into the pot.

[0005] As shown in FIG. 1, the rubber sheet wound in a roll shape is wound under tension, so that pressure is applied between the rubber sheets. When only the rubber sheet is wound, the rubber adheres to each other due to this pressure. In order to prevent this, a separator made of resin, cloth, or the like is usually wound between the rubber sheets.

[0006] In the manufacturing process, a large amount of unvulcanized rubber sheet for about one to two days is cut and stored in a state where the separator is peeled off in order to improve work efficiency. Since the unvulcanized rubber sheets are stacked and left with the separator removed, there is a problem that if the unvulcanized rubber has high adhesiveness, the sheets adhere to each other and cannot be peeled off. Such problems can be avoided by stacking unvulcanized rubber sheets with the separator in close contact, but in this case, when preforming, it is said that the separator is stripped from each uncured rubber sheet that has been cut finely Work is required. Furthermore, when weighing the unvulcanized rubber to be used, weighing control including a separator is required, so that workability is significantly reduced.

[0007] Therefore, the high tackiness of the rubber lowers the work efficiency and lowers the productivity. Reducing the tackiness of rubber is an important factor as a processing characteristic of rubber for improving productivity.

Another important property in processing unvulcanized rubber is the viscosity of the unvulcanized rubber. This is an index indicating the flow characteristics after the unvulcanized rubber has been charged into the mold. If the viscosity is high, it causes factors such as streaks at the fused portion of the rubber in compression molding, resulting in defective production. Further, in transfer molding, it causes a rubber filling defect and the like. Here, FIG. 2A shows an example of a cross-sectional view of the inside of the cavity of an insulating rubber molding die using conductive rubber as an insert during transfer molding, and FIG. 2B shows a side view thereof. In the transfer molding, for example, rubber is injected from a gate 7 into a cavity 6 in a mold 5 in which a core metal 4 is arranged as shown in FIG. 2, and the rubber flows in the direction of arrow 9. In the example shown in FIG. 2, the conductive rubber layer 8 is formed. When the rubber is filled in such a state, if the viscosity is high, the rubber does not flow to the tip of a portion showing a triangle in the cross section in the cavity 6 and the filling is defective. Therefore, in order to obtain good processability, it is desirable to lower the viscosity of the unvulcanized rubber.

In the injection molding,
Rubber material is usually 3-10mm thick and 30-100mm wide
It has a band-like shape having a cross-sectional shape of, and is stored and stored on a pallet or the like. At this time, since the unvulcanized rubbers come into contact with each other, if the tackiness is high, the same problem as described above occurs in that the rubber materials are less likely to peel off. Also at the time of rubber molding by injection molding, if the viscosity is high as in transfer molding, there is a problem that the rubber does not flow into the thin portion, so that it is desirable that the viscosity is low to prevent poor filling.

[0010] In such applications, as a method of lowering the viscosity of the rubber material to increase the fluidity, a method of frequently using process oil has been adopted. However, when the process oil is frequently used, the adhesion between the unvulcanized rubber compounds becomes large, and there are problems such as oil transfer to other fitting members and bleeding.

[0011] Although a rubber composition which has improved fluidity and low tackiness without using a large amount of process oil is desired, a rubber composition satisfying these conditions has not yet been obtained.

[0012]

SUMMARY OF THE INVENTION Therefore, the present invention provides a process for connecting electric wires and cables, which has a low process oil content, a low viscosity and a low tackiness, and has excellent moldability.
It is an object of the present invention to provide an optimal rubber composition for terminals.

[0013]

In order to solve the above-mentioned problems, the present invention provides an insulating rubber composition containing a base rubber and an inorganic filler, wherein the base rubber has a Mooney viscosity ML 1 + 4 ( 100 ° C.) of 50 to 90% by weight of a first ethylene propylene rubber having a Mooney viscosity of ML 1 + 4
(100 ° C.) is 50 to 10% by weight of a second ethylene propylene rubber having 11 to 25, and the amount of the inorganic filler is 2 to 100 parts by weight of the base rubber.
0 to 100 parts by weight, 6% by weight based on the whole composition
Provided is an insulating rubber composition containing a process oil in the following ratio.

The present invention is also a conductive rubber composition comprising a base rubber and a conductivity-imparting component, wherein the base rubber has a first ethylene propylene having a Mooney viscosity ML 1 + 4 (100 ° C.) of 10 or less. 50 to 90% by weight of the second rubber and 50 to 10% by weight of a second ethylene propylene rubber having a Mooney viscosity ML 1 + 4 (100 ° C.) of 11 to 25. Base rubber 1
The present invention provides a conductive rubber composition characterized by containing 20 to 60 parts by weight with respect to 00 parts by weight and containing a process oil in a proportion of 6% by weight or less based on the whole composition.

Hereinafter, the present invention will be described in detail.

In the rubber composition of the present invention, the base rubber is composed of two kinds of ethylene propylene rubbers having different first and second viscosities (hereinafter, also simply referred to as EP rubbers). EP rubber refers to ethylene propylene copolymer rubber (EPM) and ethylene propylene diene terpolymer (EPDM), and ethylene propylene diene terpolymer refers to ethylene and propylene. And a diene-based monomer such as ethylidene norbornene, 1,4-hexadiene and dicyclopentadiene.

The first EP rubber has Mooney viscosity ML 1
+4 (100 ° C.) is 10 or less, and in the present invention,
Such low viscosity polymers were used to sufficiently reduce the viscosity of the composition while minimizing the amount of process oil added. The proportion of the first EP rubber in the base rubber is from 50% by weight to 90% by weight, and more preferably from 60% by weight to 80% by weight. If the proportion of the first EP rubber is less than 50% by weight, the viscosity of the composition cannot be sufficiently reduced, while if it exceeds 90% by weight, the tackiness of the material becomes high, causing a handling problem. .

The second EP rubber has Mooney viscosity ML 1
+4 (100 ° C.) is 11 to 25, and is blended in order to reduce the adhesiveness of the composition. The proportion of the second EP rubber in the base rubber is from 10% by weight to 50% by weight, and more preferably from 20% by weight to 40% by weight. When the proportion of the second EP rubber is less than 10% by weight, the tackiness of the composition becomes high, causing a problem in handleability,
On the other hand, if it exceeds 50% by weight, the hardness of the composition becomes high and the product properties deteriorate.

The insulating rubber composition of the present invention contains 20 to 100 parts by weight of an inorganic filler such as clay, calcium carbonate, talc, and aluminum hydroxide based on 100 parts by weight of the base rubber. In the proportion of If the amount of the inorganic filler is less than 20 parts by weight, the viscosity of the composition becomes high, while if it exceeds 100 parts by weight, the viscosity of the composition becomes high. For example, in a fitting member, there is a problem in that the hardness of the rubber member is increased so that the insertability of the rubber component into the cable is deteriorated. The mixing ratio of the inorganic filler is more preferably 30 parts by weight or more and 50 parts by weight or less based on the base rubber.

On the other hand, the conductive rubber composition of the present invention contains 20 parts by weight of a conductivity-imparting component composed of carbon such as acetylene black and ketjen black, which are highly conductive carbon, based on 100 parts by weight of the base rubber. More than 60
It is blended at a ratio of not more than parts by weight. For example, the amount of acetylene black, which is conductive carbon, is preferably in the range of 40 to 60 parts by weight, and in the case of Ketjen black having good conductivity, the range of 20 to 30 parts by weight is preferable. Becomes If the amount of carbon is less than this preferred range, the volume resistivity of the rubber composition will be large, and if it is more than this preferred range, the viscosity or hardness of the rubber composition will be high. Occurs.

As the vulcanizing agent to be added to the base polymer and vulcanized in the present invention, an organic peroxide is preferably used. For example, dicumyl peroxide (DCP), 5-dimethyl-2,5-di (t-butylperoxy) hexyne, 1,3-bis- (t-butylperoxyisopropyl) benzene, and 1,1-
Di-t-butylperoxy-3,3,5-trimethylcyclohexane and the like.

The amount of the vulcanizing agent can be appropriately determined according to the vulcanization speed, the mechanical properties of the vulcanized product, and the like.
It is about 2 to 5 parts by weight based on 100 parts by weight of the base rubber.

In addition, it is possible to add carbon as a small additive to wax, an antioxidant, a vulcanization accelerator, a metal oxide, and an insulating rubber composition by a known technique as a compounding agent constituting a rubber composition. it can.

In the rubber composition of the present invention, a process oil is added in an amount of 6% by weight or less based on the whole rubber composition in addition to the above-mentioned components. When the blending amount of the process oil exceeds 6% by weight, not only the tackiness of the composition increases, but also problems such as migration of the oil to other fitting members occur, thereby achieving the object of the present invention. Can not.

In producing the rubber composition of the present invention,
First, a first EP rubber and a second EP rubber are mixed at a predetermined ratio, and an inorganic filler is used for an insulating rubber composition, and a conductivity imparting component is used for a conductive rubber composition. The components are mixed at a predetermined ratio, and other components except the vulcanizing agent are added as necessary, and kneaded with a mixer or the like. Next, the rubber composition of the present invention is obtained by adding a vulcanizing agent using an oven roll or the like.

The rubber composition of the present invention thus prepared contains a base rubber in which two types of EP rubbers having different viscosities are blended in an appropriate ratio, so that the amount of process oil added can be reduced. Was. For this reason, low viscosity,
A rubber composition having low tackiness and avoiding all the conventional problems caused by heavy use of process oil was able to provide a rubber composition having optimal characteristics for electric wires, cable connections and terminals.

[0027]

Next, the present invention will be described in more detail with reference to specific examples.

With the compositions shown in Tables 1 and 2, the insulating rubber compositions of Examples 1 to 8 and Comparative Examples 1 to 7 were prepared.

[0029]

[Table 1]

[Table 2] The numerical values for the compositions in the table represent the amounts added (parts by weight).

In Examples 1 to 8 and Comparative Examples 1 to 6, zinc oxide ^{* 13} (5 parts by weight), antioxidant ^{* 14} (2 parts by weight), organic peroxide ^{* 15} (3 parts by weight) ) And carbon
^{* 16} (1 part by weight) was further added.

In Comparative Example 7, zinc oxide ^{* 13} (5 parts by weight), antioxidant ^{* 17} (2 parts by weight), stearic acid
^{* 18} (1 part by weight), silane coupling agent ^{* 19} (1 part by weight), carbon ^{* 20} (5 parts by weight), organic peroxide
^{* 15} (2.7 parts by weight) and vulcanization aid ^{* 21} (1 part by weight) were further added.

The components used here are shown below.

* 1 EPDM (Mitsui Chemicals) * 2 EPDM (Mitsui Chemicals) * 3 EPM (JSR) * 4 EPM (JSR) * 5 EPDM (Mitsui Chemicals) * 6 EPDM (Mitsui Chemicals) * 7 Satinton W (manufactured by Engelhard) * 8 White gloss flower CC (manufactured by Shiraishi Calcium) * 9 Heidilite H42M (manufactured by Showa Denko) * 10 MV talc (manufactured by Nippon Mistron) * 11 Thumper 2280 (Made by Nippon Sun Oil Co., Ltd.) * 12 Sansen 4240 (made by Nippon Sun Oil Co., Ltd.) * 13 Two kinds of zinc white (Mitsui Metals Co., Ltd.) * 14 Nocrack CD (Ouchi Shinko Co., Ltd.) * 15 DCP (Mitsui Chemicals Co., Ltd.) * 16 Asahi Carbon # 35 (Asahi Carbon) * 17 Nocrack MB (Ouchi Shinko) * 18 Adeka fatty acid SA-200 (Asahi Denka Kogyo) * 19 A- 72 (Nippon Unicar Co., Ltd.) * 20 Dia Black H (manufactured by Mitsubishi Chemical Industries, Ltd.) * 21 triallyl isocyanurate (manufactured by Nippon Kasei Chemical Co., Ltd.) In addition, physical properties of each EP rubber (Mooney viscosity ML 1 + 4 (1
00) are summarized in Table 3 below.

[0034]

[Table 3] As shown in Table 3, EPT-4010 corresponds to the first EP rubber used in the present invention, and EPT-3012
P and EP02P correspond to the second EP rubber used in the present invention.

In preparing each of the insulating rubber compositions, components other than an organic peroxide (DCP: manufactured by Mitsui Chemicals, Inc.) as a vulcanizing agent were first kneaded with a 1.7 liter Banbury mixer to obtain a mixture. Thereafter, a vulcanizing agent was charged by an oven roll. Finally, it was formed into a sheet and its characteristics were evaluated.

The viscosity was measured in a Mooney scorch test according to JIS K6300 at a measurement temperature of 140 ° C. using a L-shaped rotor. The minimum Mooney viscosity (Vm) obtained in this way was used as the scale.

The tackiness was evaluated by checking whether the unvulcanized sheet having a thickness of 2 mm was left standing at room temperature and peeled off at the sheet interface after 24 hours. A sheet that peeled off at the interface between the sheets was evaluated as good (O), and a sheet that did not peel off at the interface and fused together was evaluated as poor (x).

In evaluating the vulcanized rubber, an unvulcanized rubber was press-vulcanized at 160 ° C. for 30 minutes to prepare a test sheet. Using this, the hardness was measured by JIS-A type according to JIS K 6301 hardness test.

The physical properties are shown in Tables 1 and 2.

The evaluation criteria for Mooney scorch viscosity are as follows. In the case of transfer molding, usually, after forming a conductive rubber layer 8 as shown in FIG. 2, insulating rubber is poured into and filled into a portion having a triangular cross section formed by the conductive rubber layer 8. For this reason, in the case of conductive rubber, it is necessary that the product is easily molded, and in the case of insulating rubber, it must be filled in a thin portion, so that a property having a lower viscosity than that of conductive rubber is required. Preferred values for excellent moldability are that the minimum viscosity at 140 ° C. of Mooney Scorch is 20 or less for conductive rubber and 10 or less for insulating rubber. In the case of insulating rubber, if it exceeds 10, the rubber does not reach the tip of the triangular cross section shown in FIG. 2 and a desired product shape cannot be obtained.

The evaluation criteria for hardness are as follows. These rubber connection and terminal parts are usually used by being inserted into a cable, and are designed with a diameter difference which is an interference fit so that no gap is formed between the cable and the rubber part. Accordingly, a great deal of force is required to insert these rubber parts into the cable, but if the rubber hardness is too high, the rubber parts cannot be inserted by a normal working method. The limit hardness is 64 or less for insulating rubber having a high volume ratio in general products, and is 74 or less for conductive rubber having a low volume ratio.

As shown in Table 1, the present invention (Examples 1 to 3)
The insulating rubber composition of 8) has a Mooney scorch minimum viscosity of 10 or less, which is a preferable range for the insulating rubber composition, and all have good adhesiveness. Further, the hardness of each composition is 64 or less, which is a preferable range.

On the other hand, the compositions of Comparative Examples 1 to 7, which are out of the range of the present invention, cannot satisfy all three properties of viscosity, tackiness, and hardness. Comparative Example 1 is a first EP rubber, that is, a polymer EPT- having a low viscosity.
Since 4010 is 100% by weight and the second EP rubber is not compounded, the adhesiveness is high. Comparative Example 2
In this case, the mixing ratio of the first EP rubber and the second EP rubber is out of the range of the present invention, and EPT-301 having a high viscosity is used.
Since 2P is used as much as 60% by weight, the hardness is 65%.
And deviates from the preferred range. In Comparative Example 3, since the proportion of the filler was as small as 20 parts by weight, the adhesiveness was high.
In Comparative Example 4, since the filler was as large as 120 parts by weight, the Mooney scorch minimum viscosity was as high as 12, and in Comparative Example 5, a high-viscosity polymer (EP941P) was used without blending the second EP rubber. The viscosity is also 1
It is as high as 1. In Comparative Example 6, 3 process oils were used.
Since it contains 0% by weight, it has high adhesiveness, and when used as an actual product, a problem of oil transfer to other fitting members is expected. Comparative Example 7 includes the first and second EPs.
High viscosity polymer EPT-103 without compounding rubber
5 is used in an amount of 100% by weight, so that the viscosity is high and exceeds the preferred range.

Next, with the compositions shown in Tables 4 and 5,
The conductive rubber compositions of Examples 9 to 14 and Comparative Examples 8 to 14 were prepared.

[0045]

[Table 4]

[Table 5] The numerical values for the compositions in the tables represent parts by weight.

Examples 9 to 14 and Comparative Examples 8 to 1
3, zinc oxide ^{* 13} (5 parts by weight), anti-aging agent
^{* 14} (2 parts by weight), organic peroxide ^{* 15} (3 parts by weight), and powdered stearic acid ^{* 24} (1 part by weight) were further added.

In Comparative Example 14, zinc oxide ^{* 13} (5
Parts by weight), anti-aging agent ^{* 17} (2 parts by weight), stearic acid
^{* 18} (1 part by weight), organic peroxide ^{* 15} (2.7 parts by weight), and vulcanization aid ^{* 21} (1 part by weight) were further added.

The components used here are shown below.

* 22 Denka Black (manufactured by Denki Kagaku) * 23 Ketjen Black EC (manufactured by Nippon EC) * 24 Stearic acid powder (manufactured by NOF Corporation) The other components (* 1 to * 21) are as described above. Are the same as those described in Tables 1 and 2.

After the conductive rubber compositions of Examples 9 to 14 and Comparative Examples 8 to 14 were obtained in the same manner as described above, the viscosity, tackiness and hardness were evaluated in the same manner as described above. Furthermore, based on the standards of the Japan Rubber Association Standard SRIS2301, the volume resistivity indicating conductivity was measured for each conductive rubber composition.

The physical properties are shown in Tables 4 and 5.

If the volume resistivity of the conductive rubber is too high, there arises a problem that the heat generation temperature in the external conductive layer becomes high and the current flow at the time of the ground fault becomes insufficient.
Therefore, the volume resistivity of the conductive rubber is 5 × 10 ³ Ω-cm.
The following are the preferred ranges.

As shown in Table 4, the present invention (Examples 9 to 9)
The conductive rubber composition of 14) has a Mooney scorch minimum viscosity of 20 or less, which is a preferable range for the conductive rubber composition, and all have good adhesiveness.
Further, each of the compositions has a hardness of 74 or less and a volume resistivity of 5 × 10 ³ Ω-cm or less, and physical properties within a preferred range are obtained.

On the other hand, the compositions of Comparative Examples 8 to 14, which are outside the range of the present invention, cannot satisfy all of the four properties of viscosity, tackiness, hardness, and volume resistivity. In Comparative Example 8, since the amount of acetylene black was as large as 70 parts by weight, the viscosity was high and the hardness was also high. In Comparative Example 9, since only the first EP rubber, that is, a low-viscosity polymer (EPT-4010) was used at 100% by weight, the adhesiveness was high. In Comparative Example 10,
The compounding ratio of the first EP rubber and the second EP rubber is out of the range of the present invention, and the high viscosity EPT-3012P
Is used in an amount of 60% by weight. In Comparative Example 11, since the blending amount of Ketjen Black was as small as 10 parts by weight, the volume resistivity was beyond the preferred range. In Comparative Example 12, since the high viscosity EP941P was used without compounding the second EP rubber, the viscosity exceeded the preferred range and was 21. Comparative Example 1
3 uses 30% by weight of process oil,
It has high tackiness and, when used as an actual product, causes a problem of oil transfer to other fitting members. Comparative Example 14
Uses 100% by weight of a high-viscosity polymer EPT-1035 without compounding the first and second EP rubbers, and thus has a high viscosity and exceeds a suitable range.

[0055]

As described above in detail, the present invention provides a rubber composition having a low content of process oil, low viscosity, excellent moldability and low tackiness. The rubber composition of the present invention is most suitable for electric wires, cable connections, and terminals, and has great industrial value.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a roll of a rubber sheet.

FIG. 2 is a schematic diagram showing the inside of a cavity of an insulating rubber molding die having conductive rubber as an insert.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Shaft 2 ... Rubber sheet 3 ... Separator 4 ... Core metal 5 ... Mold 6 ... Cavity 7 ... Gate 8 ... Conductive rubber layer 9 ... Flow direction of insulating rubber

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takuya Tanaka 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F term (reference) 4J002 AE053 BB15W BB15X DA037 DE146 DE236 DJ036 DJ046 FD016 FD017 FD023 GQ01 GQ02 5G301 DA18 DD04 5G305 AA02 AA04 AB36 BA13 CA47 CA51 CD01 CD17

Claims (2)

[Claims] 1. An insulating rubber composition containing a base rubber and an inorganic filler, wherein the base rubber has a Mooney viscosity ML 1 + 4 (100 ° C.) of 10 or less. 90
Weight% and Mooney viscosity ML 1 + 4 (100 ° C)
5 second ethylene propylene rubber 50 to 10% by weight
Wherein the compounding amount of the inorganic filler is 20 to 100 parts by weight with respect to 100 parts by weight of the base rubber, and the composition contains a process oil in a proportion of 6% by weight or less based on the whole composition. A characteristic insulating rubber composition. 2. A conductive rubber composition containing a base rubber and a conductivity-imparting component, wherein the base rubber has a Mooney viscosity ML 1 + 4 (100 ° C.) of 10 or less. ~ 90
Weight% and Mooney viscosity ML 1 + 4 (100 ° C)
5 second ethylene propylene rubber 50 to 10% by weight
Wherein the compounding amount of the conductivity-imparting component is 20 to 60 parts by weight based on 100 parts by weight of the base rubber, and a process oil in a proportion of 6% by weight or less based on the whole composition A conductive rubber composition comprising: