JP2003003025A - High specific gravity epdm composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve strength, weatherability and hot moisture resistance of a high specific gravity EPDM composition which has a high specific gravity, is soft and restrains blooming. SOLUTION: The rubber composition composed mainly of EPDM is obtained by impregnating 100 vol.% of rubber with 30-150 vol.% of nickel powder or cupric oxide powder to attain the specific gravity >=3.0 and <=6.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high specific gravity EPDM composition, and more particularly to an EPDM composition having high specific gravity as well as excellent weather resistance, flexibility and moldability.

[0002]

2. Description of the Related Art Heretofore, metallic materials such as lead have been mainly used for products having a high specific gravity and a certain degree of flexibility, represented by weight members and balance weights of sports goods. . However, in recent years, polymer materials obtained by filling various polymers with high specific gravity metals or the like have been proposed as the high specific gravity materials as described above because they are safe for the environment, excellent in corrosion resistance, and easy to process. , Used in various fields.

Conventionally, most of the above-mentioned polymer materials having a high specific gravity use thermoplastic resins and thermoplastic elastomers. For example, Japanese Patent Application Laid-Open No. 2000-154323 proposes a tungsten-containing high specific gravity composition in which tungsten powder is dispersed in a thermoplastic elastomer or a thermoplastic resin. In addition, JP-A-10-158507
In the publication, a high specific gravity resin composition containing a polyamide resin, in which tungsten powder is dispersed in a polyamide resin, as a main component is proposed. Further, JP-A 2000-129036 proposes a composition for a sound insulating sheet in which a styrene-based thermoplastic elastomer is mixed with a high specific gravity inorganic filler. Further, Japanese Patent Laid-Open No. 2000-256569 proposes a high specific gravity thermoplastic resin composition obtained by mixing a powdery and granular heavy metal and a thermoplastic resin.

On the other hand, a polymer material having a high specific gravity using rubber is also mentioned, and it is disclosed in JP-A-10-153687.
In the issue, vulcanized fluororubber in which tungsten is dispersed and EP
In addition to the DM rubber proposed, a radiation shielding material in which tungsten is dispersed in chloroprene rubber has also been proposed.

[0005]

However, the above-mentioned Japanese Patent Laid-Open Nos. 2000-154323 and 10-158.
507, JP 2000-129036 A, JP 200
The high specific gravity resin material of No. 0-256569 has a high specific gravity because it is dispersed with metal powder, and also has rubber elasticity and flexibility because it contains a thermoplastic resin, a thermosetting resin, a thermoplastic elastomer as a main component. However, it has a problem that it cannot be used under conditions of high temperature because of its low melting point.

It is also possible to use nylon, polyethylene or the like having a high melting point, but since these are hard substances, there is a problem that the composition cannot be made flexible.

Further, in Japanese Patent Laid-Open No. 10-153687, there is a problem that it is difficult to process fluororubber in combination with other materials because of poor adhesion. EPDM rubber generally has rubber elasticity, is superior in strength and weather resistance, and is superior in adhesiveness to fluororubber, so that it can be processed with adhesives and other materials, but it disperses high specific gravity metal powders. When this is done, there is a problem in moldability and the workability and weather resistance are insufficient. In particular, when exposed to a very harsh environment such as used outdoors in the summer or in seawater, additives may bleed into the rubber surface and blooming may occur, resulting in insufficient heat and humidity resistance. .

As a high specific gravity composition used for weight members, balance weights, vibration-damping and sound-insulating sheets, sound-insulating members, etc. of sporting goods, a material having high specific gravity and softness is desired, and when used outdoors. Is required to have the above heat resistance and humidity resistance. In particular, if it is left in a high temperature in a car, it will be in a high temperature and high humidity state, blooming will occur, and the surface of the composition will become sticky, so that the user may feel discomfort when touching the composition during use, which is a problem. There is.
Furthermore, when it is used for various balance weights, weight members for sports, etc., it is likely to come into contact with the human body, so it needs to be softer and can be dropped.
It is desired to have a material having a certain degree of strength so as not to be broken by hitting.

The present invention has been made in view of the above problems, and has a high specific gravity E having a high specific gravity, softness, excellent weather resistance and heat and humidity resistance, and sufficient strength.
It is an object to provide a PDM composition.

[0010]

In order to solve the above-mentioned problems, the present invention comprises EPDM as a main component, and 3 parts of nickel powder or cupric oxide II powder to 100% by volume of rubber.
It is contained in a proportion of 0% by volume to 150% by volume,
A high specific gravity EPDM composition having a specific gravity of 3.0 or more and 6.0 or less is provided.

As a result of earnest research, the present inventor has dispersed nickel powder or cupric oxide II powder in EPDM having rubber elasticity and excellent weather resistance, and defines the volume% of the powder with respect to rubber as described above. Thus, it was found that the additives and the like do not bloom from the surface of the composition even under the condition of high heat and high temperature. In order to obtain a composition having a higher specific gravity, it is necessary to disperse a larger amount of metal powder, but there is a limit to the volume of metal that can be contained in a sheet or various shapes to maintain strength. Therefore, the present inventor
Through repeated experiments, it was found that it was optimal to include the above-mentioned metal powder in EPDM in the above-specified volume%. By using the above-mentioned composition, a high specific gravity EPDM composition having a high specific gravity, softness, excellent weather resistance and heat and humidity resistance, and sufficient strength can be obtained.

In the high specific gravity EPDM composition of the present invention, the nickel powder or the cupric oxide II powder is 30% by volume or more and 150% by volume or less, preferably 60% by volume or more and 120% by volume or less with respect to 100% by volume of the rubber. , And more preferably 77% by volume or more and 119% by volume or less. The reason for setting the above range is that the specific gravity becomes too small when the content is less than 30% by volume, and therefore the volume must be increased in order to add the weight necessary as a weight for sports equipment and the like. On the other hand, if it is more than 150% by volume, the surface of the nickel powder or the cupric oxide II powder cannot be covered with EPDM, resulting in a decrease in strength and difficulty in forming into a sheet or the like. Thus, by using nickel or cupric oxide II as the metal powder, it is possible to improve weather resistance and heat and humidity resistance.

The high specific gravity EPDM composition of the present invention has a specific gravity of 3.0 or more and 6.0 or less, preferably 4.
The range is 0 or more and 5.0 or less. The reason why the above range is set is that when the specific gravity is less than 3.0, the volume is large when used as a weight for sports equipment or the like, which may hinder the use. On the other hand, if the specific gravity is more than 6.0, it is necessary to add a large amount of nickel powder or cupric oxide II powder, which makes processing difficult.

Nickel powder or oxide II in EPDM
In order to disperse the copper powder well and increase the strength, the average particle size of the powder is preferably 50 μm or less. More preferably, it is 20 μm or less. In addition, by using a combination of a small particle size and a large particle size, for example,
The fluidity and moldability can be improved by using a material having a particle size of m or less and a material having a particle size of 27 μm or more in combination.

The EPDM is preferably vulcanized with peroxide. To improve the strength and weather resistance of a high specific gravity EPDM composition by carrying out peroxide vulcanization instead of sulfur vulcanization when vulcanizing nickel powder or cupric oxide II powder dispersed in EPDM. You can

The above-mentioned peroxides include dicumyl peroxide and 1,1-bis (t-butylperoxy).
3,3,5-Trimethylcyclohexane, bis (t-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5- Di (t-butylperoxy) hexyne-3 and the like can be mentioned. Among them, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and dicumyl peroxide are preferable because they have excellent weather resistance. In particular, it is preferable to use 2,5-dimethyl-2,5-di (t-butylperoxy) hexane because the tensile strength is improved.

A crosslinking aid is preferably blended with the above-mentioned peroxide. By adding a crosslinking aid such as triallyl isocyanurate or a polyfunctional methacrylate monomer, the tensile strength and tear strength of the high specific gravity EPDM composition can be improved.

Although there are some types of EPDM having different properties depending on the molecular weight, the amount of diene and the amount of ethylene, by using the EPDM having the amount of diene, the amount of ethylene and the Mooney viscosity defined in the above ranges, weather resistance, moldability and strength can be improved. It is possible to obtain a high specific gravity EPDM composition which is excellent in surface and soft.

The amount of diene in EPDM is in the range of 4.5% by weight or less (% by weight of the diene component in the entire EPDM raw material), preferably 3.5% by weight or less. When EPDM with a large amount of diene is used, nickel powder or cupric oxide II powder and additives are easily bloomed in the outdoor exposure test (sunlight), the sunshine weatherometer test exposed to ultraviolet rays, and the xenon test.
By reducing the amount of the diene in M to 4.5% by weight or less, the occurrence of blooming can be suppressed and the weather resistance can be improved.

In order to mold the high specific gravity EPDM rubber with a required strength, it is particularly important to optimize the range of the amount of ethylene in EPDM and the value of Mooney viscosity. The amount of ethylene is large and the Mooney viscosity is high. It is preferred to use EPDM.

Therefore, the weight% of the ethylene component in the whole EPDM raw material is in the range of 58% by weight or more and 80% by weight or less, preferably 64% by weight or more and 80% by weight or less,
More preferably, it is 64% by weight or more and 70% by weight or less, and the optimum range is 64% by weight or more and 66% by weight or less. The amount of ethylene is within the above range because the EPD is less than 58% by weight.
Since M has a lower strength, when the nickel powder or the cupric oxide II powder is dispersed and then formed into a sheet, the formability is lowered. On the other hand, 8
When EPDM is larger than 0% by weight, it becomes harder, which makes it difficult to uniformly mix and disperse nickel powder or cupric oxide II powder. When molding into a thin sheet,
This is because the moldability is likely to be lowered, and the high specific gravity material after molding becomes harder and easily hits the human body when used as sports equipment and the like.

The Mooney viscosity at 125 ° C. of EPDM: ML _{1 + 4} (125 ° C.) is in the range of 50 to 170, preferably 100 to 170, and more preferably 150 to 165. Here, the Mooney viscosity is measured by a method defined in JIS K6300 and used as an index showing the viscosity.
In ML _{1 + 4} , M means Mooney's M, L means rotor shape L, and (1 + 4) means 1 minute of preheating time and 4 minutes of rotation time of rotor. The above range is defined as EPD having a Mooney viscosity of less than 50 at 125 ° C.
In M, since the strength becomes smaller, the moldability after dispersing the nickel powder or the cupric oxide II powder is likely to be lowered. On the other hand, in EPDM having a Mooney viscosity of greater than 170 at 125 ° C., it becomes harder and it becomes more difficult to uniformly mix and disperse nickel powder or cupric oxide II powder, and the moldability in molding into a thin sheet is reduced. This is because the high specific gravity material after molding becomes harder and easily hits the human body.
The molecular weight of EPDM can be determined to some extent by the Mooney viscosity. The higher the Mooney viscosity, the higher the molecular weight. When the Mooney viscosity is 50, the molecular weight is 300,000 to 400,000, and the Mooney is Viscosity 17
When it is 0, the molecular weight is about 600,000.

The softening agent is added in an amount of 150 parts by weight or less, preferably 50 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the above rubber. It is particularly useful when it is used in a product or the like that can improve the property and may come into contact with the human body. The above range is based on 100 parts by weight of rubber and 150 parts by weight of the softening agent.
This is because blooming is likely to occur in a weather resistance test or the like when the amount is more than the weight part.

The oil used as the softening agent is not particularly limited, but paraffin oil or naphthene oil having high compatibility with EPDM is preferable. In particular, paraffinic oil is preferable because it has low volatility and is easy to handle, and a quantified amount can be surely added. In addition, for example, a synthetic oil known per se composed of an aromatic mineral oil or a hydrocarbon oligomer, or a process oil can be used. As the synthetic oil, for example, an oligomer of α-olefin, an oligomer of butene, ethylene and α
-Amorphous oligomers with olefins are preferred.

EPDM includes non-oil-extended EPDM consisting only of a rubber component and oil-extended EPDM containing an oil together with a rubber component, but any type can be used. However, oil-extended EPDM
The added weight of the oil therein is treated as the added weight (oil amount) of the softening agent.

In the high specific gravity EPDM composition of the present invention, the surface hardness after vulcanization of the high specific gravity EPDM composition measured by the method specified in JIS K-6253 (testing machine durometer type A) is 95. The following is preferable. This is because if the hardness is greater than 95, the hardness is too high and it becomes difficult to perform integral molding with other members. It should be noted that the smaller the value of the hardness, the better if the other required characteristics are satisfied.

Further, in the high specific gravity EPDM composition of the present invention, its tensile strength is preferably 1.5 MPa or more. This is because if the tensile strength is less than 1.5 MPa, cracking and breakage easily occur during molding and use. If other required characteristics are satisfied, 1.5 MPa
The larger the above, the better.

The main chain of EPDM is composed of saturated hydrocarbon,
Since the main chain does not contain double bonds, high concentration ozone atmosphere,
Even if exposed to an environment such as light irradiation for a long period of time, molecular main chain scission hardly occurs, and weather resistance can be enhanced. In addition,
Some EPDMs have different types of diene components, but the types are not particularly limited.

The rubber component in the high specific gravity EPDM composition of the present invention is EPDM100 from the viewpoint of weather resistance as described above.
%, But it is also possible to appropriately mix one or more other rubber components in addition to EPDM. When EPDM is blended with another rubber component, the proportion of EPDM in the total rubber component in the high specific gravity EPDM composition is preferably 80% by weight or more, and more preferably 90% by weight or more. Note that some EPDMs have different types of diene components (third component) and the like, but the types are not particularly limited.

Rubber components other than EPDM rubber include ethylene propylene rubber (EPR), natural rubber (NR),
Butadiene rubber (BR), styrene butadiene rubber (S
BR), isoprene rubber (IR), acrylonitrile-
Butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR), acrylic rubber (ACM, AN)
M), urethane rubber (U), silicone rubber (Si) and the like can be used, and one kind or two or more kinds selected from the above rubber components can be mixed and used.

In order to improve the mechanical strength of the EPDM composition having a high specific gravity, a filler may be compounded, if necessary, within a range that does not reduce the flexibility of the rubber. As the filler, for example, silica, carbon black, clay,
Powders such as talc can be mentioned. By adding a filler, the tensile strength and tear strength of rubber can be improved.

In addition to the above-mentioned compounding agents, an antiaging agent, wax and the like can be compounded in the high specific gravity EPDM composition, if necessary. Examples of the antiaging agent include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine and N, N-di-.
Examples include amines such as β-naphthyl-p-phenylenediamine and N-phenyl-N′-isopropyl-p-phenylenediamine.

The high specific gravity EPDM composition of the present invention also comprises
In addition to the above-mentioned peroxide, it is also possible to vulcanize with powdered sulfur or the like. When using powdered sulfur, it is preferable to add a vulcanization accelerator, such as slaked lime and magnesia (Mg
Inorganic accelerators such as O) and litharge (PbO), and organic accelerators described below can be used. Examples of the organic accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, thiazoles such as N-cyclohexyl-2-benzothiazolesulfene, and aliphatic primary amines such as n-butylamine, tert-butylamine, and propylamine. -Condensation product of 2-mercapto-benzothiazole, dicyclohexylamine, pyrrolidine, piperidine and other aliphatic secondary amines with 2-mercapto-benzothiazole, alicyclic primary amine and 2-
Sulfenamide compounds such as oxidative condensation products with mercapto-benzothiazole, oxidative condensation products with morpholin-based compounds and 2-mercapto-benzothiazole, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, dipentamethylene It is preferable to appropriately combine thiuram compounds such as thiuram tetrasulfide and dithiocarbamate compounds such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate and tellurium diethyldithiocarbamate.

The high specific gravity EPDM composition of the present invention is molded into various shapes such as a sheet shape, a block shape, a spherical shape, and a square shape to obtain a weight member for sports equipment (tennis,
It can be suitably used as a weight member such as golf, a training article), a balance weight, and various other weights, a vibration damping and sound insulating sheet, a soundproofing member, and the like, which have high specific gravity and are soft and which are required to have weather resistance.

[0035]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. High specific gravity EP of the first embodiment of the present invention
In the DM composition, EPDM having a diene amount of 4.0% by weight, an ethylene amount of 66% by weight, and a Mooney viscosity of 165 at 125 ° C. is used as a rubber component.

The EPDM is an oil-extended EPDM, and EP
100 parts by weight of oil is oil-extended with respect to 100 parts by weight of DM. In addition, carbon, an antioxidant and a cross-linking auxiliary agent are mixed in required amounts, kneaded with a closed type kneader, and added with 2,5-dimethyl-2,5-di (t-butylperoxy) hexane which is a peroxide. Sulfurized to obtain the base material.

Further, nickel (Ni) powder having an average particle diameter of 17.1 μm and a specific gravity of 8.91 was added to the above base material and kneaded with a closed type kneader to obtain an EPDM composition having a high specific gravity. In the high specific gravity EPDM composition, nickel powder is contained at a ratio of 80% by volume to 100% by volume of EPDM. The high specific gravity EPDM composition has a specific gravity of 4.5.

The high specific gravity EPDM composition has a surface hardness after vulcanization of 70 and a tensile strength of 6.2 MPa as measured by the method specified in JIS K-6253 (testing machine durometer type A).

High specific gravity EP prepared with the above composition
The DM composition is moderately soft, has no problem in strength, is excellent in weather resistance and heat / humidification resistance without blooming, and can be used in high temperature and high humidity environments. It can be suitably used as a material for a weight member of sports equipment used in, for example.

Hereinafter, Examples 1 to 12 and Comparative Example 1 of the high specific gravity EPDM composition of the present invention will be described in detail.

First, each component such as EPDM and other additives was set to each part by weight shown in Table 1 below, and three base compounds (base A, base B, base C) having different vulcanization methods were prepared. It was mixed. Base A is 2,5-dimethyl-2,
Peroxide vulcanization with 5-di (t-butylperoxy) hexane, base B was peroxide vulcanization with dicumyl peroxide, and base C was sulfur vulcanization. The rubber component was EPDM only.

[0042]

[Table 1]

Each of the base formulations shown in Table 1 was kneaded into a base material using a small closed type kneading machine (MixLab SW, manufactured by Moriyama Co., Ltd.). Each base composition (base A, base B,
Nickel powder or cupric oxide II powder was added to the base material kneaded in the base C) and kneaded in a closed type kneader, and as shown in Table 2 below, high specific gravity EPDM compositions for each example and comparative example were prepared. Got The above high specific gravity EPDM composition was charged into a mold and pressed at 170 ° C. for 20 minutes to give a thickness of 0.
A 6 mm sheet was created.

[0044]

[Table 2]

(Example 1) The base composition was base A,
As EPDM, Esplen 67 manufactured by Sumitomo Chemical Co., Ltd.
0F (oil extended EPDM) was used. The amount of diene was 4.0% by weight, the amount of ethylene was 66% by weight, and the Mooney viscosity at 125 ° C. was 165. In addition, Esplen 670F
100 parts by weight of oil was added to 100 parts by weight of EPDM. High specific gravity EP by adding nickel (Ni) powder with an average particle size of 17.1 μm and a specific gravity of 8.91
In the DM composition, 80% by volume of nickel powder was contained with respect to 100% by volume of EPDM. Specific gravity is 4.5
And

(Example 2) Paraffin oil PW380
(Manufactured by Idemitsu Kosan Co., Ltd.) was added in an amount of 50 parts by weight to 100 parts by weight of EPDM to make the total amount of oil 150 parts by weight.
The specific gravity was 4.4. Others were the same as in Example 1.

Example 3 Nickel powder was contained in a proportion of 140 vol% with respect to 100 vol% of EPDM.
The specific gravity was 5.6. Others were the same as in Example 1.

(Example 4) 33% by volume of nickel powder was contained in 100% by volume of EPDM. The specific gravity was 3.0. Others were the same as in Example 1.

Example 5 Base B was used as the base formulation. 71% nickel powder based on 100% by volume of EPDM
It was contained in a volume percentage. Specific gravity is the same as in Example 1.
It was set to 5. Others were the same as in Example 1.

(Example 6) Base C was used as the base C. The specific gravity was 4.5. Others were the same as in Example 1.

Example 7 Copper II oxide (CuO) powder having an average particle diameter of 7.3 μm and a specific gravity of 6.4 was added. EPD
The copper (II) oxide (CuO) powder was contained in a proportion of 81% by volume based on 100% by volume of M. The specific gravity was 3.4.
Others were the same as in Example 1.

(Example 8) 150% by volume of cupric oxide II (CuO) powder was contained in 100% by volume of EPDM. The specific gravity was 4.2. Others were the same as in Example 7.

Example 9 Base B was used as the base formulation. The specific gravity was 4.1. Others were the same as in Example 7.

Example 10 Base C was used as the base formulation. The specific gravity was 3.4. Others were the same as in Example 7.

(Example 11) Paraffin oil PW380 (Idemitsu Kosan Co., Ltd.) was used with respect to 100 parts by weight of EPDM.
100% by weight, and the total amount of oil is E
The amount was 200 parts by weight based on 100 parts by weight of PDM. The specific gravity was 4.4. Others were the same as in Example 1.

Example 12 As the EPDM, non-oil-extended Esplen 532 (manufactured by Sumitomo Chemical Co., Ltd.) was used. The amount of ethylene in Esplen 532 was 51% by weight. Paraffin oil PW380 (manufactured by Idemitsu Kosan Co., Ltd.) was contained at a ratio of 100 parts by weight with respect to 100 parts by weight of EPDM. The specific gravity was 4.5. Others were the same as in Example 1.

Comparative Example 1 Nickel powder was contained in a proportion of 205% by volume with respect to 100% by volume of EPDM.
The specific gravity was 6.3. Others were the same as in Example 1.

Of the above Examples 1 to 12 and Comparative Example 1,
The hardness (standard A) was measured and the tensile strength was measured by the tensile test for the examples and comparative examples in which the sheet could be prepared. In addition, a weather resistance test was performed to evaluate the presence or absence of blooming. For each test and evaluation method,
It will be described later. The evaluation results are shown in Table 2 above.

(Hardness measurement) By the method specified in JIS K-6253 (testing machine durometer type A),
The surface hardness of the high specific gravity EPDM composition after vulcanization was measured.

(Tensile test) A tensile test was carried out with a JIS No. 3 dumbbell shape under the condition of a tensile speed of 500 mm / min to measure the strength (MPa) at break.

(Weather resistance test) A weather resistance test was carried out with a super xenon weather meter (SX75, manufactured by Suga Test Instruments Co., Ltd.) to confirm the presence or absence of blooming after 1 week and 2 weeks.

(Heat and Humidity Resistance Test) A heat and humidity resistance test was carried out for 2 weeks in an oven at 80 ° C. and 90% h to confirm the presence or absence of blooming.

The average particle diameters of the nickel (Ni) powder and the cupric oxide II (CuO) powder shown in Table 2 are assumed to be laser diffraction / scattering type particle size distribution measurement (LA-9, Horiba, Ltd.).
In 10), measurement was performed using ethanol as a solvent.

Examples 1-10 include EPDM compositions containing
Since nickel powder or cupric oxide II powder is contained in the optimum volume within the specified range with respect to 100% by volume of rubber, it is reasonably soft, has no problem in strength, and has no blooming or weathering resistance. It was confirmed that the EPDM composition had a high specific gravity excellent in heat resistance and humidity resistance. On the other hand, in Comparative Example 1, the sheet could not be prepared because the amount of the nickel powder added was too large. Examples 11 and 12 are 2
The weather resistance after a week was slightly inferior, but there was no problem until 1 week later.

In addition, Examples 1 and 5 and 6 and Examples 7 and 10 and Examples 8 and 9 having the same specific gravity except that only the base composition is different.
Comparing the respective tensile strengths with each other, the strengths of the bases A and B of the peroxide vulcanization are higher than those of the base C of the sulfur vulcanization, and particularly 2,5-dimethyl-2,5-di (t It was confirmed that vulcanization with -butylperoxy) hexane increased the strength.

From the above, nickel powder or cupric oxide II powder is contained in the EPDM composition in an optimum volume within a specified range with respect to 100% by volume of rubber to obtain a high specific gravity, and under optimum conditions. By using EPDM, adding an optimum amount of softening agent and carrying out peroxide vulcanization, it is moderately soft, has excellent moldability, has no problems in strength, and has extremely high performance and high specific gravity that does not cause blooming. It has been confirmed that can be created.

[0067]

As is apparent from the above description, according to the present invention, nickel powder or cupric oxide II powder is added to the EPDM composition in an optimum volume within the specified range with respect to 100% by volume of rubber. Since it is contained in the composition (1), it is possible to obtain a high specific gravity EPDM composition having a high specific gravity, softness, and excellent weather resistance and heat and humidity resistant characteristics without blooming.

Further, by weathering EPDM with peroxide, the weather resistance and strength can be further improved. In particular, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is added. Sulfur can further increase the strength.

Further, the amount of diene, the amount of ethylene, 125 ° C.
By specifying the amount of the softening agent using EPDM having the Mooney viscosity specified in (1), it is possible to suppress the occurrence of blooming and improve the weather resistance and heat and humidity resistance characteristics while being softer. Therefore, it can be suitably used for various products such as weight members of sports equipment which require flexibility, weight feeling and weather resistance.

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Claims (5)

[Claims] 1. Nickel powder or cupric oxide II powder to 3 parts by volume of rubber containing EPDM as a main component.
It is contained in a proportion of 0% by volume to 150% by volume,
A high specific gravity EPDM composition having a specific gravity of 3.0 or more and 6.0 or less. 2. The high specific gravity EPDM composition according to claim 1, wherein the EPDM is vulcanized with peroxide. 3. The high specific gravity EPDM composition according to claim 2, wherein 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is used as the peroxide. 4. The diene amount of the EPDM is 4.5% by weight.
Below, the amount of ethylene is 58% by weight or more and 80% by weight or less, 1
Mooney viscosity at 25 ° C: ML _{1 + 4} (125 ° C)
Is 50 or more and 170 or less, and the softening agent is added in a ratio of 150 parts by weight or less with respect to 100 parts by weight of the rubber. 4. The high specific gravity EPDM composition according to claim 1. . 5. The surface hardness measured by the method specified in JIS K6253 (testing machine durometer type A) is 95 or less, and the tensile strength is 1.5 MPa or more. The high specific gravity EPDM composition according to item 1.