EPDM composition

Abstract

An EPDM composition, which is a rubber composition prepared by compounding carbon black, a plasticizer and a crosslinking agent in ethylene-propylene-diene terpolymer rubber. Among them, the plasticizer is 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. This EPDM composition does not impair the kneadability and processability, and the hardness change of the obtained crosslinked product after the heat aging test is at the same level as that in the case of compounding the same number of parts of α-olefin oligomer, and is greatly improved compared with the case of compounding an aliphatic dibasic acid ester.

Description

Technical Field

[0001] The present invention relates to an EPDM composition. More specifically, it relates to an EPDM composition that can be used as a molding material such as automotive vibration isolation rubber. Background Art

[0002] Automotive vibration isolation rubber is indispensable mainly for preventing vibrations and noises generated from the engine and vibrations and noises received from the road surface during driving from being transmitted into the vehicle interior. Recently, due to the trend of higher engine efficiency and space saving in automobiles, the heat-resistant environment near the engine compartment or around the exhaust pipe has become more severe than before.

[0003] When the vibration isolation rubber undergoes thermal deterioration, not only does the vibration isolation function and vibration damping function decrease due to an increase in the spring constant or elastic modulus, but also the durability deteriorates due to a decrease in strength and elongation. Therefore, in order to maintain the functions of the applicable products, high heat resistance is required for the vibration isolation rubber.

[0004] On the other hand, during the use of an automobile in an extremely low temperature environment, since the rubber material approaches the glass state, sometimes the spring constant or elastic modulus of the vibration isolation rubber increases, and the vibration isolation function and vibration damping function decrease. From this viewpoint, low temperature performance has also become one of the important requirements for vibration isolation rubber for automobiles.

[0005] Here, EPDM is a polymer with a good balance of high heat resistance and excellent low temperature performance. Usually, based on EPDM as the base polymer, through the compounding technology of other fillers and plasticizers, the heat resistance and low temperature performance of the automotive vibration isolation rubber are optimized.

[0006] As a method for improving the low temperature performance of EPDM, a method of compounding an α-olefin oligomer (Patent Document 1, etc.) and a method of compounding an aliphatic dicarboxylic acid ester (Patent Document 2, etc.) are known. However, in the method of compounding an aliphatic dicarboxylic acid ester, although it is very excellent in low temperature performance, the oxygen atom of the carbonyl group abstracts the β-hydrogen atom from the alcohol, resulting in easy thermal deterioration and a tendency to significantly damage the heat resistance of the rubber material. In addition, in the case of compounding an α-olefin oligomer, although the balance between low temperature performance and heat resistance is excellent, according to the recent higher standard requirements, further improvement of these two properties is sought.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: WO2005 / 057045

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2005-172165 Summary of the Invention

[0011] Technical problem to be solved by the invention

[0012] The object of the present invention is to provide an EPDM composition which can produce a rubber with well-balanced low-temperature performance and heat resistance, such as vibration damping products for crankshafts and drive shafts, and vibration-proof rubbers for various assembled products.

[0013] Solution to the problem

[0014] The above object of the present invention is achieved by an EPDM composition, which is a rubber composition prepared by compounding carbon black, a plasticizer, and a crosslinking agent in ethylene-propylene-diene terpolymer rubber. Among them, the plasticizer is 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% by weight to 22% by weight.

[0015] Advantages of the invention

[0016] The EPDM composition of the present invention exhibits the following excellent effects: without impairing the kneadability and processability, the hardness change of the obtained crosslinked product after the heat aging test is at the same level as that in the case of compounding the same amount of α-olefin oligomer, and is greatly improved compared with the case of compounding an aliphatic dicarboxylic acid ester.

[0017] Furthermore, as shown in the following examples and comparative examples, in the test of the temperature dependence of the viscoelastic modulus, for the ratio of the elastic modulus E' at -30°C to the elastic modulus E' at 60°C, i.e., E'(-30°C / 60°C), although it is not as good as the case of compounding an aliphatic dicarboxylic acid ester, it has excellent low-temperature performance compared with the case of compounding an α-olefin oligomer.

[0018] The reason for these effects is that the reaction product of the neopentyl-type polyol and the monocarboxylic acid, i.e., the polyol ester, is compatible with EPDM, thereby improving the molecular mobility in the rubber material and the low-temperature performance. At the same time, since the polyol ester has a structure that is not easily thermally deteriorated, it does not hinder the heat resistance of the material. Detailed implementation mode

[0019] As the ethylene-propylene-diene terpolymer rubber (EPDM), a rubber in which various diene components are copolymerized in a small amount in ethylene and propylene can be arbitrarily used. In fact, various commercially available EPDMs can be directly used, such as the EP series products of JSR Corporation and the Keltan series products of ARLANXEO Corporation.

[0020] As the carbon black, furnace black commonly used as a reinforcing agent can be used, and it is preferably used with a nitrogen adsorption specific surface area of 20 m 2 / g to 240 m 2Carbon black with a DBP oil absorption of 40 ml / 100 g to 180 ml / 100 g, such as HAF carbon black, FEF carbon black, etc. The carbon black is used in the EPDM composition in a proportion of about 20% to 40% by weight, preferably about 25% to 40% by weight. When the carbon black is used in a proportion less than the above range, the reinforcing property becomes smaller and it becomes difficult to meet the basic physical properties of the rubber material. On the other hand, when used in a proportion more than the above range, the aggregation of the carbon black sometimes has an adverse effect on the physical properties of the rubber material, so it is not preferred.

[0021] As the plasticizer, a polyol ester composed of a neopentyl-type polyol and a monocarboxylic acid (from the viewpoint of low-temperature properties, preferably a polyol ester which is a reaction product of a trivalent neopentyl-type polyol such as trimethylolpropane and a linear monocarboxylic acid having 5 to 15 carbon atoms, more preferably 5 to 12 carbon atoms) is compounded in the EPDM composition in a proportion of about 5% to 22% by weight (for example, 8 parts to 40 parts by weight relative to 100 parts by weight of EPDM), preferably in a proportion of 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 from the alcohol in its molecular structure, so it is not easily thermally deteriorated and has excellent heat resistance and low-temperature properties. In fact, commercially available products such as Nippon Oil & Fats Co., Ltd. products Unister H-327R, H-334R, etc. can be directly used.

[0022] Here, as the composition that is the basis for calculating the weight ratio of the plasticizer, etc., it is a composition that contains an acid acceptor, a lubricant, an anti-aging agent, and a co-crosslinking agent in addition to carbon black, a plasticizer, and a crosslinking agent in ethylene-propylene-diene terpolymer rubber. Even when other compounding agents are compounded, these other compounding agents are not included in the total weight of the composition that is the basis for calculating the weight ratio of the plasticizer, etc. When the compounding amount of the polyol ester in the composition is less than 5% by weight, the effect of improving low-temperature properties is small. On the other hand, when it exceeds 22% by weight, the productivity and processability of the rubber material deteriorate, and the polyol ester precipitates from the crosslinked product.

[0023] As the organic peroxide crosslinking agent, for example, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)3-hexyne, etc., which are commonly used in the crosslinking of EPDM, are used in the EPDM composition in a proportion of about 0.5% to 2.5% by weight, preferably about 1.0% to 1.8% by weight.

[0024] Preferably, together with an organic peroxide crosslinking agent, multifunctional unsaturated compounds such as commonly used triallyl isocyanurate, triallyl cyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N,N'-m-phenylene maleimide, or 1,2-polybutadiene, etc. are used. These co-crosslinking agents are used in a proportion of about 1.0 to 5.0 parts by weight per 100 parts by weight of EPDM.

[0025] In addition, oxides or hydroxides of divalent metals, acid acceptors such as hydrotalcite, lubricants such as stearic acid, and commonly used anti-aging agents for EPDM are used in proportions 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.

[0026] In addition, in the EPDM composition where the above components are essential components, various compounding agents widely used so far can be arbitrarily added within the range that does not impair the object of the present invention.

[0027] The EPDM composition can be prepared by kneading using a kneader, rolls, etc. The kneaded product is usually crosslinked and molded into a desired shape by pressure vulcanization at about 170°C to 190°C for about 2 to 6 minutes, and then, if necessary, oven vulcanization is carried out at about 150°C to 180°C for about 1 to 5 hours (secondary crosslinking).

[0028] Examples

[0029] Next, the present invention will be described with reference to examples.

[0030] Example 1

[0031]

[0032]

[0033] After kneading the components other than the crosslinking agent in the above components using a closed kneader, the mixture was transferred to an open roll, the crosslinking agent was added thereto, and after further kneading, pressure vulcanization was carried out at 180°C for 6 minutes and oven vulcanization was carried out at 150°C for 5 hours to obtain a crosslinked product. During kneading, it was confirmed whether kneading was possible and whether there was plasticizer precipitation. In the case where kneading was confirmed to be impossible or plasticizer precipitation occurred, it was judged as ×. At the same time, the normal physical properties, heat aging resistance, and temperature dependence of the elastic modulus of the obtained crosslinked product were measured. It should be noted that for heat aging resistance and temperature dependence of the elastic modulus, evaluations were also carried out when the plasticizer content was 5.5% by weight and 18.7% by weight.

[0034] Normal physical properties: Based on JIS K6253 corresponding to ISO 48-4:2018,

[0035] Based on JIS K6251 corresponding to ISO 37:2011

[0036] Heat aging resistance: The change in hardness Hs after heat aging at 120 °C or 150 °C for 70 hours was measured, and the judgment criteria were divided according to the plasticizer ratio (5.5 wt%, 12.6 wt%, and 18.7 wt% or more), and the evaluation was carried out as follows

[0037] [[120 °C, 70 hours]]

[0038]

[0039] [[150 °C, 70 hours]]

[0040]

[0041] Temperature dependence of elastic modulus: In the temperature range of -30 °C to 60 °C, E’ was measured from -30 °C at a heating rate of 2 °C / min, and the value of E’(-30 °C) / E’(60 °C) was calculated, and the evaluation was carried out according to the plasticizer ratio as follows

[0042]

[0043] Example 2

[0044] In Example 1, the amount of plasticizer was changed to 9.8 parts by weight (5.5 wt%) and used

[0045] Example 3

[0046] In Example 1, the amount of plasticizer was changed to 39.1 parts by weight (18.7 wt%) and used

[0047] Comparative Example 1

[0048] In Example 1, no plasticizer was used

[0049] Comparative Example 2

[0050] In Example 1, the amount of plasticizer was changed to 5.2 parts by weight (3.0 wt%) and used

[0051] Comparative Example 3

[0052] In Example 1, the amount of plasticizer was changed to 58.6 parts by weight (25.6 wt%) and used

[0053] Comparative Example 4

[0054] In Example 1, the amount of plasticizer was changed to 87.9 parts by weight (34.1 wt%) and used

[0055] The results obtained in Examples 1 to 3 and Comparative Examples 1 to 4 above are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] Example 4

[0059] In Example 1, as the plasticizer, the same amount (25 parts by weight; 12.6% by weight) of polyol ester (Nippon Oil & Fats Co., Ltd. product UNISTER H-334R) was used.

[0060] Example 5

[0061] In Example 4, the amount of the plasticizer was changed to 9.8 parts by weight (5.5% by weight) and used.

[0062] Example 6

[0063] In Example 4, the amount of the plasticizer was changed to 39.1 parts by weight (18.7% by weight) and used.

[0064] Comparative Example 5

[0065] In Example 4, the amount of the plasticizer was changed to 58.6 parts by weight (25.6% by weight) and used.

[0066] Comparative Example 6

[0067] In Example 4, the amount of the plasticizer was changed to 87.9 parts by weight (34.1% by weight) and used. The results obtained in Examples 4 to 6 and Comparative Examples 5 to 6 above are shown in Table 2 below.

[0068] Table 2

[0069]

[0070] Comparative Example 7

[0071] In Example 1, as the plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of polyalphaolefin (INEOS Oligomers product Durasyn 170) was used.

[0072] Comparative Example 8

[0073] In Comparative Example 7, the amount of the plasticizer was changed to 9.8 parts by weight (5.5% by weight) and used.

[0074] Comparative Example 9

[0075] In Comparative Example 7, the amount of the plasticizer was changed to 39.1 parts by weight (18.7% by weight) and used.

[0076] Comparative Example 10

[0077] In Example 1, as the plasticizer, 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.

[0078] Comparative Example 11

[0079] In Example 1, as the plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of dioctyl sebacate (DOS, a product of Taoka Chemical Industry) was used.

[0080] Comparative Example 12

[0081] In Example 1, as the plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of diisodecyl adipate (DIDA, a product of Taoka Chemical Industry) was used.

[0082] Comparative Example 13

[0083] In Example 1, as the plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of paraffinic processing oil (Diana Process Oil PW-90, a product of Idemitsu Kosan) was used.

[0084] Comparative Example 14

[0085] In Example 1, as the plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of paraffinic processing oil (Diana Process Oil PW-32, a product of Idemitsu Kosan) was used.

[0086] The results obtained in Comparative Examples 7 to 14 above are shown in Table 3 below.

[0087] Table 3

[0088]

[0089] Industrial Applicability

[0090] The crosslinked product of the EPDM composition of the present invention has an excellent balance between low-temperature properties and heat resistance, and thus can be effectively used as a molding material for vibration-proof rubber for automobiles used in severe heat environments and cold regions, such as vibration-damping products for crankshafts and drive shafts, and various assembled products.

Claims

1. An EPDM composition, characterized in that, The EPDM composition is a rubber composition in which carbon black, a plasticizer, and a crosslinking agent are compounded in ethylene-propylene-diene terpolymer rubber. The plasticizer is a polyol ester, which is a reaction product of a neopentyl-type polyol and a monocarboxylic acid. Moreover, the amount of the plasticizer in the composition is 5 wt% to 22 wt%.

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

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

4. A crosslinked molded article, which is a crosslinked molded article of the EPDM composition according to claim 1.

5. A vibration-proof rubber, which is composed of the crosslinked molded article according to claim 4.

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