JP2001253983A - Rubber composition having low elastic modulus, and sealing material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition of a low elastic modulus, using an ethylene-propylene-diene rubber as a main material and useful as a sealing material for communication cable closure, etc. SOLUTION: This rubber composition having a low elasticity comprises 100 pts.wt. ethylene-propylene-diene rubber, >=200 pts.wt. process oil having <=-35 deg.C pour point and >=20 pts.wt. carbon black having <=80 μm average particle diameter. The rubber composition is characterized in that the ethylene- propylene-diene rubber is vulcanized and hardness specified by JIS K6253 (type A durometer) is <=20. The rubber composition can be utilized as a sealing material having flexibility and high adhesion and has satisfactory strength characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition having a low elastic modulus. More specifically, the present invention relates to a low elastic modulus rubber composition containing ethylene-propylene-diene rubber (EPDM), excellent in flexibility, small in compression set and self-adhesiveness, and a communication cable closure using the same. The present invention relates to a sealing material.

[0002]

2. Description of the Related Art Conventionally, a hard rubber member has been used as a sealing material such as a closure used for branching and connecting electric wires and optical cables. These conventional rubber members have a hardness of about 40 or more when represented by the hardness specified by JIS K6253 (Type A durometer). When such a rubber member having a high hardness is used as a sealing material, it is necessary to wrap the cable with a sealing tape or the like to fill the gap between the sealing material and the cable during work because of poor adhesion to the cable. Conventionally, as a kind of rubber, epichlorohydrin rubber has been mainly used because it is hard to be hardened at low temperature.

[0003] The closure is a container for branching and connecting electric wires and optical fibers.

[0004]

However, when a sealing tape is used, the working process becomes very troublesome,
It takes a long working time. Further, the sealing tape is usually made of unvulcanized rubber, and when the sealing material is removed from the cable, the unvulcanized rubber adheres to the cable and cannot be peeled off properly. Therefore, there arises a problem that reassembly is difficult. Until now, epichlorohydrin rubber has been mainly used as the rubber material, but since the material cost is high, utilization of a cheaper rubber material is desired.

[0005]

Means for Solving the Problems and Effects of the Invention In order to solve the above problems, the present inventors have conducted various studies to develop a sealing material composition using EPDM as a rubber material, and as a result, completed the present invention. It was done. That is, the present invention provides: 1) 100 parts by weight of ethylene-propylene-diene rubber,
A composition containing 200 parts by weight or more of process oil having a pour point of -35 ° C. or less and 20 parts by weight or more of carbon black having an average particle diameter of 80 μm or less, wherein the ethylene-propylene-diene rubber is added. A low-modulus rubber composition, which is sulfurized and has a hardness of 20 or less as measured by a method specified in JIS K6253 (using a type A durometer);
And 2) a sealing material for communication cable closures, wherein the rubber composition according to claim 1 is used.

The low modulus rubber composition of the present invention has a hardness of JIS K6253 (using a type A durometer).
Is adjusted to be 20 or less when expressed by, and has flexibility. This hardness is preferably 15 or less,
More preferably, it is set to 10 or less. Due to such high flexibility, when used as a sealing material for a communication cable closure, the adhesiveness to the cable is high, the sealing property is improved, and the attachment is easy. Conventional rubber members have a high hardness and do not adhere to the cable, so a sealing tape has been used in combination.However, when the low elastic modulus rubber composition of the present invention is used as a sealing material, such a combination is not necessary, and the sealing is not required. Work becomes very easy. In addition, it has the necessary strength as a sealing material, and can be easily separated from the cable, so that it can be reassembled. In addition, EPDM as rubber material
Since it is used, it has weather resistance and aging resistance,
Moreover, it has low compression set even at low temperatures.

Therefore, the low elastic modulus rubber composition of the present invention
It can be used very advantageously as a sealing material.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the low elastic modulus rubber composition of the present invention, the rubber material is E
A PDM is used, but a known one can be used. EPDM here is composed of three components of ethylene, propylene and diene. The Mooney viscosity of EPDM is an index of its molecular weight. The higher the molecular weight, the higher the viscosity, and conversely, the lower the molecular weight, the lower the viscosity. In the present invention, an EPD having a Mooney viscosity at 125 ° C. of 90 to 130, preferably 70 or more in a non-oil extended state.
M is used. When the molecular weight of EPDM is high, there is an advantage that the strength is high.

[0009] The iodine value of EPDM is an index of the amount of diene component in the rubber of the present invention. When the iodine value is large, it indicates that the diene component is large. As the iodine value increases, the reactivity increases and vulcanization becomes easier, but deterioration of aging resistance and weather resistance due to the diene component also easily occurs. In the present invention, the iodine value is 2 in consideration of aging resistance and weather resistance.
EPDM that is 0 or less is preferably selected. Also, E
The diene constituting the PDM is not particularly limited, but ethylidene norbornene (ENB), which has a high degree of vulcanization, is preferable.

[0010] Next, the process oil in the low elastic modulus rubber composition of the present invention needs to have a pour point of -35 ° C or less, and is contained in an amount of 200 parts by weight or more based on 100 parts by weight of EPDM. The content of the process oil is preferably at least 250 parts by weight, while the upper limit is not particularly limited as long as it does not impair flexibility and strength suitable as a sealing material, but is generally possible up to about 700 parts by weight,
Preferably it is up to 500 parts by weight.

For the purpose of exhibiting a function as a sealing material or the like even at a low temperature, the process oil used has a pour point of −35 ° C. or less according to the measurement standard of JIS K2269. In addition, a material having good compatibility with EPDM was selected. For that purpose, SP (Solubility Parame
ter) The value is preferably about 6 to 8. Preferred examples of the process oil include paraffin oil,
Examples thereof include naphthenic oil having almost no aroma and a large amount of paraffin components, and a low molecular weight liquid ethylene-propylene copolymer or oligomer having an SP (Solubility Parameter) value of about 6 to 8. As a specific example,
In the low elastic modulus rubber composition of the present invention, such as Diana Process PX-90 (manufactured by Idemitsu Kosan Co., Ltd., pour point -45 ° C.), the average is based on 100 parts by weight of EPDM in order to impart not only flexibility but also strength. Particle size 80 μm
20 parts by weight or more of the following carbon black is contained. The amount of the carbon black is more preferably at least 30 parts by weight. When the amount is less than 20 parts by weight, no reinforcing effect can be expected. On the other hand, the upper limit is not particularly limited as long as the intended function of the composition of the present invention is not impaired. Up to about 200 parts by weight per part by weight. In addition, the average particle diameter is 8
If it exceeds 0 μm, the reinforcing effect is reduced.

The type of the carbon black is S
AF (Super Abrasion Furnace), ISAF (Intermedi
ate Super Abrasion Furnace), HAF (High Abrasion
Furnace), FEF (Fast Extrusion Furnace) or GPF (General Purpose Furnace).
In addition, when expressed by the ASTM standard, N-220, N-
Grades such as 330 and N-660 are preferred. The low elastic modulus rubber composition of the present invention needs to have EPDM vulcanized for the purpose of reducing compression set and increasing flexibility. Vulcanization can be carried out by a conventional method by adding a vulcanizing agent and, if necessary, a vulcanization accelerator and a vulcanization activator.
For vulcanization, sulfur vulcanization, peroxide vulcanization, or a combination of these vulcanizations can be employed.Specifically, if conditions and combinations are appropriately selected so that the vulcanization temperature is low and can be completed in a short time. Good. In general, good compression set can be obtained by peroxide vulcanization, but this is in the high temperature range, and in the low temperature range, on the contrary, flexible sulfur vulcanization with molecular motion is more preferably applied.

As the peroxide, benzoyl peroxide, 1,1-bis-t-butylperoxy-3,
A peroxide having a relatively low half-life of 1 minute, such as 3,5-trimethylcyclohexane or 1-bis (t-butylperoxy) cyclododecane, may be used. In the case of other peroxides, the crosslinking agent can be crosslinked at a lower temperature by using a crosslinking assistant as compared with the case where no peroxide is used. In the case of sulfur vulcanization, EPDM10
0.5 to 3 parts by weight (in terms of sulfur) is added to 0 parts by weight.

As the vulcanization activator, zinc white, stearic acid and the like can be used. Usually, a total amount of 3 to 20 parts by weight may be used.
In the case of peroxide vulcanization, it is preferable to use a crosslinking assistant suitable for the vulcanization. For example, it is a polyfunctional monomer, a polyfunctional polymer, a sulfur compound and the like, and specifically, triallyl isocyanurate, quinone dioxime and the like can be used. Examples of the vulcanization accelerator include thiazoles [eg, 2-mercapto benzothiazole (M)], thiurams [eg, tetramethyl thiuram disulfide (TET)],
A dithiocarbamate type (eg, zinc dibutyl dithiocarbamate (BZ), tellurium diethyl dithiocarbamate (TTTE)) or a sulfenamide type can be used in about 2 to 20 parts by weight.

The rubber composition of the present invention may contain, if necessary, a filler, a Nada burner, a tackifier, a pigment, a processing aid, an ultraviolet stabilizer, an antioxidant, etc., together with the above essential components. Can be. As the filler, for example, calcium carbonate, clay, magnesium carbonate and the like can be used at 0 to 300 weight parts. As the Nada fuel, for example, 0 to 100 parts by weight of aluminum hydroxide, antimony trioxide and the like can be used.

As the tackifier, for example, 0 to 200 parts by weight of a low molecular weight component such as a coumarone-indene resin, an aliphatic hydrocarbon resin, an alicyclic hydrocarbon resin, or liquid polybutene or liquid polyisoprene is used. be able to. As the pigment, any of organic and inorganic pigments can be used, and examples thereof include lithopone and titanium oxide.
As the processing aid, for example, 0 to 50 parts by weight of stearic acid, fatty acid ester and the like can be used.

The rubber composition of the present invention has a low elastic modulus
And the specific process oil and carbon black are mixed and kneaded. Here, the process oil is added in an amount of 180 parts by weight or more as described above. However, if this amount is added to the rubber component at once, other additives will not be well dispersed in the rubber. Further, there is a problem that the process oil is hard to be uniformly mixed into the rubber component, and it takes an extremely long time to complete the mixing. In order to avoid this, the rubber component is first kneaded with an additive other than the process oil and about 0 to 100 parts by weight of the process oil, whereby the additive other than the process oil is sufficiently added. Can be dispersed. Thereafter, when the remaining process oil is added at a time or divided into several times, a rubber composition having good workability and uniformity as a whole can be obtained. For kneading, an ordinary kneader can be used. The vulcanization is performed at 160 to 200 ° C. by using press or injection molding.

The low-elastic modulus rubber composition of the present invention is JIS
Hardness when measured by a method specified by K6253 (using a type A durometer) is 20 or less, preferably 1
The hardness is adjusted to be 5 or less, more preferably 10 or less, and this hardness is an essential requirement that the process oil and carbon black be contained as described above,
Further, it can be achieved by adjusting the type and amount of other additives or the degree of vulcanization. When the rubber composition has such hardness, the rubber composition exhibits a low elastic modulus, that is, flexibility.

As another hardness measurement method, when the hardness is measured using a rubber hardness meter “Asuka C2 type” manufactured by Kobunshi Keiki Co., Ltd., the low elastic modulus rubber composition of the present invention has a hardness of 60%. It is preferably at most 50, more preferably at most 50, even more preferably at most 40. The low elastic modulus rubber composition of the present invention preferably has, in addition to the hardness specified above, a compression set at 70 ° C. of 40% or less as measured by the method specified in JIS K6262, % Is more preferable.

The low elastic modulus rubber composition of the present invention has the above properties, and is therefore suitable for producing a sealing material. The production of the sealing material can be carried out in the usual manner using the above rubber composition. For example, it can be manufactured by appropriately selecting the shape of the sealing material and by molding. The low elastic modulus rubber composition described above is suitable, for example, for sealing a gap between a cable and a housing.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples along with comparative examples. In addition, the physical property of the rubber composition prepared below and the characteristic as a sealing material were measured by the following methods. [Test Method] (1) Hardness: Measured by the following two methods.

A) The hardness was measured by the method specified in JIS K6253 (using a type A durometer) (this hardness is indicated as HDA in Table 1). b) Rubber hardness tester "Asuka C2 type" manufactured by Kobunshi Keiki Co., Ltd.
(This hardness is represented as Asker C in Table 1). (2) Breaking strength (TB): Measured by a tensile test specified in JIS K6251. (3) Compression set: measured by two methods specified in the following JIS.

A) The compression set at 70 ° C. was determined according to JIS.
It was measured by the method specified in K6262. b) Determine the compression set at -20 ° C according to JIS K626.
It measured according to the method prescribed | regulated in 1. However, the strain was calculated not at the time immediately after the compression was released but at the value of the test temperature 30 minutes after the release. (4) Installation time: As shown in FIG. 1A, a cable 2 (here, φ18
mm polyethylene tube), and the casings were set in the casings 3 and 3 ′, and then the casings were strongly tightened with a band and sealed. The internal pressure was maintained at 1 kgf / cm ^{2 as} it was, and immersed in water all day and night to check whether there was any leakage and to judge the sealing performance. FIG. 1B shows a cross-sectional view (dimensions: mm) of the sealing material 1 in the axial direction and a cross-sectional view of the housing that receives the sealing material.

In Comparative Example 2 to be described later, a gap was formed between the polyethylene pipe and the sealing material because the rubber composition was too hard, so that a non-crosslinked type butyl rubber was wound and the diameter was increased by 4 mm. It was set on a sealing material. Judgment criteria for sealing performance ；: good sealing performance ×: poor sealing performance (5) Reassembly test: The housing of (4) was disassembled after the test, and after one hour, it was determined whether assembly was possible again.

Criteria for reassembly A: Reassembly is easily possible. ×: Reassembly is not possible. Examples 1 to 4 EPDM 670F manufactured by Sumitomo Chemical Co., Ltd. as EPDM
(Ethylene content based on a total amount of ethylene and propylene of 100; 66% by weight, Mooney viscosity at 100 ° C;
63, diene content; 4.0% by weight, diene component; EN
(B, 100 parts by weight of paraffin oil) (200 parts by weight) and the additives shown in Table 1 were kneaded in a 3 L kneader.

The kneaded product is mixed with a paraffin-based process oil (trade name: Diana Process PX-90, manufactured by Idemitsu Kosan, pour point: -45 ° C, kinematic viscosity: 110 at 40 ° C).
cSt, SP value; 7.1) were dividedly charged and kneaded. The rubber composition thus obtained is placed in a mold at 17
Vulcanized at 0 ° C. for 20 to 40 minutes, molded into a predetermined shape,
Tested. Table 1 shows the results. Comparative Example 1 In Example 1, as the carbon black, Asahi Carbon Co., Ltd. product name: Asahi # 15 (average particle diameter 122n)
m, specific surface area 12 m ² / g, iodine adsorption amount 11 mg / g
g, oil absorption A method 41 ml / 100), except that 5 parts by weight were used to prepare a rubber composition by the same production method. Table 1 shows the amounts and the test results.

Comparative Example 2 A rubber composition was prepared in the same manner as in Example 1 except that the amount of the process oil was changed to 30 parts by weight. Table 1 shows the amounts and the test results. Comparative Example 3 A rubber composition was prepared in the same manner as in Example 1, except that a process oil having a pour point of −15 ° C. was used. Table 1 shows the amounts and the test results.

[0028]

[Table 1]

As shown in Table 1, the following was found from the results of Examples and Comparative Examples. The rubber compositions of Examples 1 to 4 have a low modulus of elasticity suitable for a sealing material, have flexibility, and are satisfactory in terms of strength. Therefore,
When used as a sealing material, installation is easy,
Excellent sealing properties. Reassembly is also very easy. On the other hand, the rubber composition of Comparative Example 1 was soft but lacked strength, the surface condition of the vulcanizate was poor, and the internal pressure was so large that it could not maintain the internal pressure. The rubber composition of Comparative Example 2 was too hard and took too much time to be used as a sealing material, causing a problem in work, and was impossible to reassemble. The rubber composition of Comparative Example 3 is excellent in mounting, sealing performance, and reassembly when used as a sealing material, but has a large compression set at −20 ° C. and a low temperature range of −20 to −30 ° C. May not be able to maintain the internal pressure.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a sealing material according to the present invention and an embodiment for sealing a gap between a cable and a housing using the sealing material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seal material 2 Cable 3 and 3 'housing 4 Valve (for air injection)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H017 AA03 AB07 AD06 AE05 4J002 BB151 BB152 DA037 EA016 EA026 FD010 FD090 GJ02 GQ00 5G375 AA08 BA27 BB03 BB19 BB24 DB23 EA08

Claims (2)

[Claims] 1. An ethylene-propylene-diene rubber 100
Parts by weight, process oil 2 having a pour point of −35 ° C. or less
A composition containing at least 00 parts by weight and at least 20 parts by weight of carbon black having an average particle diameter of 80 μm or less, wherein the composition is obtained by vulcanizing the ethylene-propylene-diene rubber and conforming to JIS K6253 (Type A). A low modulus rubber composition having a hardness of 20 or less as measured by a method specified by a durometer. 2. A sealing material for a communication cable closure, wherein the rubber composition according to claim 1 is used.