EPDM composition

Abstract

Provided is a EPDM composition which is a rubber composition in which carbon black, a plasticizer, and a crosslinking agent are mixed in an ethylene-propylene-diene ternary copolymer rubber, wherein the plasticizer is a polyol ester which is a reaction product of a neopentyl-type polyol and a monocarboxylic acid, and the plasticizer weight in the composition is 5-22 wt%. This EPDM composition provides a crosslinked product that, in terms of change in harness after a heat-aging test, is equivalent to a case where the same amount of an α-olefin oligomer is mixed, and is greatly improved over a case where an aliphatic dibasic acid ester is mixed, without a loss kneadability or processability.

Description

[Technical field]

[0001] The present invention relates to an EPDM composition, and more particularly to an EPDM composition used as a molding material for automobile anti-vibration rubber and the like. [Background technology]

[0002] Anti-vibration rubber for automobiles is essential for preventing the transmission of vibrations and noise generated mainly by the engine and vibrations and noise received from the road surface while driving into the interior of the vehicle. Due to the recent trend towards more efficient and space-saving engines in automobiles, the heat-resistant environment around the engine compartment and exhaust pipes has become even more severe than before.

[0003] When anti-vibration rubber deteriorates due to heat, not only does the spring constant or elastic modulus increase, causing a decline in its vibration-isolating and vibration-damping functions, but the strength and elongation also decrease, leading to a deterioration in durability. Therefore, anti-vibration rubber is required to have high heat resistance in order to maintain the functionality of the products to which it is applied.

[0004] On the other hand, when used in the extremely low temperature environment of an automobile, the spring constant or elastic modulus of the anti-vibration rubber increases due to the rubber material approaching a glassy state, which may result in a decrease in the anti-vibration and vibration-damping functions. From this perspective, low-temperature properties are also becoming one of the important requirements for anti-vibration rubber for automobiles.

[0005] Here, EPDM is a well-balanced polymer that combines high heat resistance with excellent low-temperature properties, and generally, EPDM is used as the base polymer and, through compounding techniques for other fillers and plasticizers, the heat resistance and low-temperature properties of automotive anti-vibration rubber are improved.

[0006] Known methods for improving the low-temperature properties of EPDM include blending an α-olefin oligomer (Patent Document 1, etc.) and blending an aliphatic dibasic acid ester (Patent Document 2, etc.), but while those blended with an aliphatic dibasic acid ester have excellent low-temperature properties, they are prone to thermal degradation initiated by the abstraction of β-hydrogen atoms derived from alcohol by the oxygen atom of the carbonyl group, and tend to significantly impair the heat resistance of the rubber material. In addition, when an α-olefin oligomer is blended, although it has an excellent balance between low-temperature properties and heat resistance, there is a demand for further improvement in both of these properties due to recent demands for even higher standards. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2005 / 057045 [Patent Document 2] JP 2005-172165 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an EPDM composition which provides rubber having an excellent balance between low temperature resistance and heat resistance, for example, vibration-damping rubber for vibration-damping products for crankshafts and propeller shafts, and various mount-related products. [Means for solving the problem]

[0009] The object of the present invention is achieved by an EPDM composition in which ethylene-propylene-diene terpolymer rubber is blended with carbon black, a plasticizer, and a crosslinking agent, the plasticizer being a polyol ester which is a reaction product of a neopentyl-type polyol and a monocarboxylic acid, and the amount of the plasticizer in the composition is 5 to 22% by weight. Effect of the Invention

[0010] The EPDM composition of the present invention exhibits the excellent effect that, without impairing kneadability and processability, the crosslinked product obtained has a hardness change after a heat aging test that is equivalent to that of a crosslinked product containing the same amount of α-olefin oligomer, and is significantly improved compared to a crosslinked product containing an aliphatic dibasic acid ester.

[0011] Furthermore, as shown in the Examples and Comparative Examples described later, in a test of the temperature dependence of viscoelastic modulus, the ratio E' (-30 / 60°C) of the elastic modulus E' at -30°C to the elastic modulus E' at 60°C was superior in low temperature properties to the case where an aliphatic dibasic acid ester was added, although it was not as good as the case where an aliphatic dibasic acid ester was added.

[0012] These effects are due to the fact that polyol ester, a reaction product of neopentyl-type polyol and monocarboxylic acid, is compatible with EPDM, improving molecular mobility in the rubber material and improving low-temperature properties, and because the polyol ester has a structure that is resistant to thermal degradation, it does not impair the heat resistance of the material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As ethylene-propylene-diene terpolymer rubber (EPDM), any of the ethylene and propylene copolymerized with small amounts of various diene components can be used. In practice, various commercially available EPDMs, such as the EP series made by JSR and the Keltan series made by ARLANXEO, can be used as they are.

[0014] As the carbon black, furnace black, which is generally used as a reinforcing agent, can be used. Preferably, the carbon black has a nitrogen adsorption specific surface area of ​​20 to 240 m. 2 / g and DBP oil absorption of 40 to 180 ml / 100 g, such as HAF carbon black and FEF carbon black, is used. Carbon black is used in an EPDM composition in a ratio of about 20 to 40% by weight, preferably about 25 to 40% by weight. If carbon black is used in a ratio less than this, the reinforcing effect is reduced and it becomes difficult to satisfy the basic physical properties of the rubber material, while if carbon black is used in a ratio greater than this, the aggregation of carbon black may adversely affect the physical properties of the rubber material, which is not preferable.

[0015] As the plasticizer, a polyol ester composed of a neopentyl type polyol and a monocarboxylic acid, preferably a polyol ester which is a reaction product of a trivalent neopentyl type polyol such as trimethylolpropane and a straight-chain monocarboxylic acid having 5 to 15 carbon atoms, more preferably 5 to 12 carbon atoms, is blended in the EPDM composition at a ratio of about 5 to 22% by weight (for example, 8 to 40 parts by weight per 100 parts by weight of EPDM), preferably about 5 to 19% by weight. The polyol ester composed of a neopentyl type polyol and a monocarboxylic acid does not have a β-hydrogen atom derived from alcohol in the molecular structure, so it is resistant to thermal deterioration and has excellent heat resistance and low temperature properties, and in practice, commercially available products such as Nippon Oil & Fats' products Unistar H-327R and H-334R are used as they are.

[0016] Here, the composition used as the basis for calculating the weight percentage of plasticizers, etc. includes ethylene-propylene-diene terpolymer rubber, carbon black, plasticizers, crosslinking agents, as well as acid acceptors, lubricants, antioxidants, and co-crosslinking agents, and even if other compounding agents are added, they are not included in the total weight of the composition used as the basis for calculating the weight percentage of plasticizers, etc. If the amount of polyol ester in the composition is less than 5% by weight, the effect of improving low-temperature properties is small, while if it exceeds 22% by weight, the productivity and processability of the rubber material will deteriorate, and polyol ester will precipitate from the crosslinked product.

[0017] As the organic peroxide crosslinking agent, for example, organic peroxides generally used in EPDM crosslinking, such as dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, are used in an amount of about 0.5 to 2.5% by weight, preferably about 1.0 to 1.8% by weight, in the EPDM composition.

[0018] It is preferable to use together with the organic peroxide crosslinking agent a polyfunctional unsaturated compound such as triallyl isocyanurate, triallyl cyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N,N'-m-phenylenemaleimide, or 1,2-polybutadiene, as is commonly used, and these co-crosslinking agents are used in a ratio of about 1.0 to 5.0 parts by weight per 100 parts by weight of EPDM.

[0019] Furthermore, divalent metal oxides or hydroxides, acid acceptors such as hydrotalcite, lubricants such as stearic acid, and commonly used EPDM antioxidants are used in amounts of about 3.0 to 5.0 parts by weight, about 0.5 to 3.0 parts by weight, and about 0.5 to 3.0 parts by weight, per 100 parts by weight of EPDM, respectively.

[0020] Furthermore, various compounding agents that have been widely and generally used in the past can be added arbitrarily to the EPDM composition containing the above-mentioned components as essential components, within the limits that do not impair the object of the present invention.

[0021] The EPDM composition is prepared by kneading using a kneader, rolls, etc., and the kneaded product is generally press-vulcanized at about 170 to 190°C for about 2 to 6 minutes to be crosslinked and molded into a desired shape, and may further be oven-vulcanized (secondary crosslinking) at about 150 to 180°C for about 1 to 5 hours as necessary. EXAMPLES

[0022] The present invention will now be described with reference to examples.

[0023] Example 1 EPDM (JSR product EP22) 100 parts by weight HAF carbon black 56.6 〃 Polyol ester plasticizer 24.4 〃 (Japan Oil Products Unistar H-327R) [Plasticizer content: 12.6% by weight] Zinc oxide 5 〃 Stearic acid 0.5 〃 Anti-aging agent 0.5 〃 Co-crosslinking agent 5.0 Same Crosslinking agent 2.3 Same The above components, except for the crosslinking agent, were mixed in an internal mixer, then transferred to an open roll, where the crosslinking agent was added, and further mixed. After that, the mixture was press-vulcanized at 180°C for 6 minutes and oven-vulcanized at 150°C for 5 hours to obtain a crosslinked product. During mixing, the possibility of mixing and the presence or absence of plasticizer precipitation were confirmed, and those that could not be mixed or had plasticizer precipitation were judged as ×, and the normal physical properties, heat aging resistance, and temperature dependency of elastic modulus were measured using the obtained crosslinked product. The heat aging resistance and temperature dependency of elastic modulus were also evaluated when the plasticizer amount was 5.5% by weight and 18.7% by weight. Normal state physical properties: Compliant with JIS K6253 corresponding to ISO 48-4:2018; Compliant with JIS K6251, which corresponds to ISO 37:2011 Heat aging resistance: Change in hardness Hs was measured after 70 hours of heat aging at 120℃ or 150℃ Plasticizer ratio (5.5 wt%, 12.6 wt%, and 18.7 wt% or more) The evaluation criteria are divided according to the above criteria and evaluated as follows: [120℃, 70 hours] 5.5% by weight 12.6% by weight 18.7% by weight or more ◎ ±0~+1 ±0~+2 ±0~+3 ○ +2~+3 +3~+4 +4~+5 △ +3~+5 +5~+6 +6~+7 × +6 or more +7 or more +8 or more [150℃, 70 hours] 5.5% by weight 12.6% by weight 18.7% by weight or more ◎ ±0~+3 ±0~+5 ±0~+7 ○ +4~+5 +6~+7 +8~+9 △ +6~+7 +8~+9 +10~+11 × +8 or more +10 or more +12 or more Temperature dependence of elastic modulus: In the temperature range of -30℃ to 60℃, it increases by 2℃ / Measure E' at a heating rate of 1 min and calculate E'(-30℃) / E' Calculate the value of (60℃) Evaluated according to the plasticizer ratio as follows: 5.5% by weight 12.6% by weight 18.7% by weight or more ◎ Less than 4.8 Less than 4.0 Less than 3.7 ○ 4.8 or more but less than 5.2 4.0 or more but less than 4.3 3.7 or more but less than 4.0 △ 5.2 or more but less than 5.7 4.3 or more but less than 4.8 4.0 or more but less than 4.5 × 5.7 or higher 4.8 or higher 4.5 or higher

[0024] Example 2 In Example 1, the amount of plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0025] Example 3 In Example 1, the amount of plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0026] Comparative Example 1 In Example 1, no plasticizer was used.

[0027] Comparative Example 2 In Example 1, the amount of plasticizer was changed to 5.2 parts by weight (3.0% by weight).

[0028] Comparative Example 3 In Example 1, the amount of plasticizer was changed to 58.6 parts by weight (25.6% by weight).

[0029] Comparative Example 4 In Example 1, the amount of plasticizer was changed to 87.9 parts by weight (34.1% by weight).

[0030] The results obtained in the above Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1 below. Table 1 Measurement and evaluation items Fruit 1 Fruit 2 Fruit 3 ratio 1 ratio 2 ratio 3 ratio 4 Mixability and moldability Mixing possible Yes Yes Yes Yes Yes Yes No Plasticizer Precipitation No No No No No Yes - Judgment ○ ○ ○ ○ ○ × × Normal physical properties Hardness (JIS A) 61 69 52 74 71 40 - Tensile strength (MPa) 13.7 18.3 13.6 19.4 18.4 5.9 - Growth (%) 358 297 453 226 261 473 - 100% Modulus (MPa) 1.6 2.8 1.2 4.5 3.6 0.7 - Specific gravity 1.068 1.080 1.061 1.084 1.082 1.052 - Heat aging resistance (120℃, 70 hours) Hardness change (points) ±0 ±0 +1 +1 ±0 +3 - Tensile strength change rate (%) +13 -5 -9 +8 +2 -7 - Elongation change rate (%) +5 -9 -4 +1 -5 -1 - Judgment ◎ ◎ ◎ - ◎ ◎ - Heat aging resistance (150℃, 70 hours) Hardness change (points) +5 +4 +7 +4 +4 +11 - Tensile strength change rate (%) +6 -10 -9 -21 -10 -1 - Elongation change rate (%) -7 -18 -11 -23 -17 -8 - Judgment: ◎ 〇 ◎ - ◎ △ - Elastic modulus temperature dependence E'(-30 / 60℃) 3.89 4.63 3.37 6.51 5.59 3.36 - Judgment ◎ ◎ ◎ × △ ◎ -

[0031] Example 4 In Example 1, the same amount (25 parts by weight; 12.6% by weight) of polyol ester (UNISTAR H-334R, a product of Nippon Oil & Fats) was used as a plasticizer.

[0032] Example 5 In Example 4, the amount of plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0033] Example 6 In Example 4, the amount of plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0034] Comparative Example 5 In Example 4, the amount of plasticizer was changed to 58.6 parts by weight (25.6% by weight).

[0035] Comparative Example 6 In Example 4, the amount of plasticizer was changed to 87.9 parts by weight (34.1% by weight).

[0036] The results obtained in the above Examples 4 to 6 and Comparative Examples 5 to 6 are shown in Table 2 below. Table 2 Measurement and evaluation items Real 4 Real 5 Fruit 6 ratio 5 ratio 6 Mixability and moldability Mixing possible Yes Yes Yes Yes No Plasticizer Precipitation No No No Yes - Judgment ○ ○ ○ × × Normal physical properties Hardness (JIS A) 61 69 51 41 - Tensile strength (MPa) 14.0 18.1 13.6 7.3 - Elongation (%) 354 276 457 499 - 100% Modulus (MPa) 1.6 3.0 1.1 0.8 - Specific gravity 1.068 1.080 1.062 1.053 - Heat aging resistance (120℃, 70 hours) Hardness change (points) ±0 ±0 +1 +1 - Tensile strength change rate (%) -2 +1 -5 -3 - Elongation change rate (%) -3 +3 -3 ±0 - Judgment ◎ ◎ ◎ ◎ - Heat aging resistance (150℃, 70 hours) Hardness change (points) +5 +4 +7 +11 - Tensile strength change rate (%) +11 +1 -4 +3 - Elongation change rate (%) -2 -3 -9 -9 - Judgment ◎ ○ ◎ △ - Elastic modulus temperature dependence E'(-30 / 60℃) 3.87 4.61 3.56 3.45 - Judgment ◎ ◎ ◎ ◎ -

[0037] Comparative Example 7 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of poly-α-olefin (Durasyn 170, product of INEOS Oligomers) was used as a plasticizer.

[0038] Comparative Example 8 In Comparative Example 7, the amount of plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0039] Comparative Example 9 In Comparative Example 7, the amount of plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0040] Comparative Example 10 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of poly-α-olefin (Durasyn 164, a product of INEOS Oligomers) was used as a plasticizer.

[0041] Comparative Example 11 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of dioctyl sebacate (DOS, a product of Taoka Chemical Industries, Ltd.) was used as the plasticizer.

[0042] Comparative Example 12 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of diisodecyl adipate (DIDA, a product of Taoka Chemical Industries) was used as the plasticizer.

[0043] Comparative Example 13 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of paraffin-based process oil (Idemitsu Kosan product Diana Process Oil PW-90) was used as a plasticizer.

[0044] Comparative Example 14 In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of paraffin-based process oil (Idemitsu Kosan product Diana Process Oil PW-32) was used as a plasticizer.

[0045] The results obtained in the above Comparative Examples 7 to 14 are shown in Table 3 below. Table 3 Measurement and evaluation items ratio 7 ratio 8 ratio 9 ratio 10 ratio 11 ratio 12 ratio 13 ratio 14 Mixability and moldability Can be mixed Yes Yes Yes Yes Yes Yes Yes Yes Yes Presence or absence of plasticizer precipitation None None None None None None None None Judgment ○ ○ ○ ○ ○ ○ ○ ○ Normal physical properties Hardness (JIS A) 60 68 53 60 61 61 61 63 Tensile strength (MPa) 13.7 17.0 11.2 13.4 14.1 17.2 11.9 14.0 Elongation (%) 323 264 381 308 359 399 312 343 100% Modulus (MPa) 1.8 3.0 1.2 1.9 1.6 1.8 1.7 1.7 Specific gravity 1.049 1.071 1.029 1.058 1.066 1.072 1.053 1.058 Heat aging resistance (120℃, 70 hours) Hardness change (points) ±0 ±0 +2 +3 +4 +5 +1 +2 Tensile strength change rate (%) -2 +3 -4 +11 +2 +8 +11 +6 Elongation change rate (%) -2 ±0 -2 +3 -1 +3 +3 -2 Judgment ◎ ◎ ◎ 〇 〇 △ ◎ ◎ Heat aging resistance (150℃, 70 hours) Hardness change (points) +2 +2 +5 +10 +14 +14 +6 +9 Tensile strength change rate (%) -4 -4 -6 +14 +9 -8 +2 -4 Elongation change rate (%) -9 -12 -8 -5 -12 -23 -8 -16 Judgment ◎ ◎ ◎ × × × 〇 △ Elastic modulus temperature dependence E'(-30 / 60℃) 4.46 5.53 4.30 3.81 3.40 3.51 5.09 4.37 Judgment △ △ △ ◎ ◎ ◎ × △ [Industrial Applicability]

[0046] The cross-linked product of the EPDM composition of the present invention has an excellent balance of low temperature performance and heat resistance, and is therefore effectively used as a molding material for automobile vibration-proof rubber used in severe hot environments or cold regions, such as vibration-damping products for crankshafts and propeller shafts, and various mount products.

Claims

1. An EPDM composition in which an ethylene-propylene-diene terpolymer rubber is blended with carbon black, a plasticizer, and a crosslinking agent, the plasticizer being a polyol ester which is a reaction product of a neopentyl-type polyol and a monocarboxylic acid, and the amount of the plasticizer in the composition is 5 to 22% by weight.

2. 2. The EPDM composition of claim 1, wherein the polyol ester is a polyol ester which is a reaction product of a trivalent neopentyl-type polyol and a linear carboxylic acid having 5 to 15 carbon atoms.

3. 3. The EPDM composition according to claim 2, wherein the trivalent neopentyl type polyol is trimethylolpropane.

4. A crosslinked molded product of the EPDM composition according to claim 1.

5. A rubber vibration isolator comprising the cross-linked molding according to claim 4.