JP2009298949A - Heat resistant vibration-insulating rubber composition and heat resistant vibration-insulating rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat resistant vibration-insulating rubber composition which can provide a cured rubber having not only excellent fracture properties and vibration insulating performance (low dynamic-to-static modulus ratio) but also heat resistance and durability even when used in high-temperature environments including an engine room of an automobile, and a heat resistant vibration-insulating rubber obtained by curing the rubber composition. <P>SOLUTION: The heat resistant vibration-insulating rubber composition includes natural rubber (NR) and ethylene-propylene-diene rubber (EPDM) as rubber components in a mass ratio: NR/EPDM=70/30 to 45/55, only a peroxide as a vulcanizer, and zinc acrylate represented by structural formula (1) as a cocrosslinker. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat and vibration proof rubber composition that can be suitably used in a high temperature environment, and a heat and vibration proof rubber obtained by curing the composition. In particular, the present invention relates to a heat-resistant and vibration-proof rubber composition and a heat-resistant and vibration-proof rubber that can be suitably used at high temperature sites such as automobile torsional dampers, engine mounts, and muffler hangers.

  Conventionally, in various vehicles such as automobiles, in order to improve the comfort of passengers, various anti-vibration materials have been arranged at sites that are sources of vibration and noise to reduce the intrusion of vibration and noise into the room. Attempts have been made. For example, for engines that are the main source of vibration and noise, vibrations during engine drive are absorbed by using anti-vibration rubber for components such as torsional dampers, engine mounts, and muffler hangers. Reduces the intrusion of vibration and noise and the spread of noise to the surrounding environment.

  As a basic characteristic of such an anti-vibration rubber, a strength characteristic that supports a heavy object such as an engine and an anti-vibration performance that absorbs and suppresses the vibration are required. Furthermore, when used in a high-temperature environment such as an engine room, it is required to have excellent heat resistance and ozone resistance as well as excellent strength characteristics, low dynamic magnification, and excellent anti-vibration performance. . In particular, in recent years, the temperature in the engine room has been rising due to higher engine output and space saving in the engine room due to expansion of the indoor space, etc. It has become tough.

  Until now, natural rubber (NR), which has excellent physical properties such as fracture characteristics, has been often used as the rubber component of the vibration-proof rubber. However, although NR is excellent in destructive properties and the like, heat resistance and ozone resistance are inferior to that of synthetic rubber, so that heat resistance and ozone resistance are insufficient when used in a high temperature environment.

  Under such circumstances, in order to improve the heat resistance and ozone resistance characteristics of the anti-vibration rubber, part or all of the NR is replaced with ethylene / propylene / diene rubber (EPDM) and peroxide crosslinking is performed. ing. For example, JP-A-4-246448 (Patent Document 1) discloses a technique for improving heat resistance by adding unsaturated fatty acid zinc to EPDM alone, and JP-A-7-268147 (Patent Document 2). ) And JP-A-7-268148 (Patent Document 3) describe a rubber composition for heat- and vibration-proof rubber that provides a heat-and-vibration-proof rubber with improved durability by subjecting specific EPDM to peroxide crosslinking. Proposed. However, with these methods, there is a risk that the rubber properties such as tensile strength (room temperature, high temperature) and tearing properties and durability will be significantly reduced. Furthermore, the dynamic magnification, which is an important characteristic of the vibration-proof rubber, is increased, and the obtained cured product is often inferior in performance.

  On the other hand, as a vibration-proof rubber whose performance has been improved by other methods, a rubber molded product with high hardness and low dynamic ratio, which is based on a specific chloroprene-based rubber and contains a specific amount of carbon black and a softening agent. Heat-resistant and dynamic vulcanized with a peroxide using a rubber composition (Japanese Patent Laid-Open No. 8-127673: Patent Document 4) and an ethylene-α-olefin copolymer rubber containing no conjugated diene Anti-vibration rubber (Japanese Patent Laid-Open No. 1-299806: Patent Document 5) having excellent sag properties has been proposed, but further improvement is desired.

  Therefore, the development of anti-vibration rubber that not only has excellent fracture characteristics and anti-vibration performance (low dynamic magnification) but also exhibits excellent heat resistance and durability even in high-temperature environments such as engine rooms of automobiles is desired. It is rare.

JP-A-4-246448 JP 7-268147 A JP 7-268148 A JP-A-8-127673 Japanese Patent Laid-Open No. 1-299806

  The present invention has been made in view of the above circumstances, and when used in a high temperature environment such as an engine room of an automobile, it has not only excellent fracture characteristics and vibration isolation performance (low dynamic magnification) but also heat resistance. Another object of the present invention is to provide a heat and vibration proof rubber composition from which a rubber cured product having excellent durability can be obtained, and a heat and vibration proof rubber obtained by curing the rubber composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have formulated a rubber component containing NR and EPDM at a specific ratio, and peroxide and zinc acrylate. The present inventors have found that a rubber cured product having excellent heat resistance and vibration-proof performance can be obtained without deteriorating characteristics and fatigue characteristics, and have reached the present invention.

That is, the present invention includes natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) as a rubber component in a mass ratio of NR / EPDM = 70/30 to 45/55 and an excess as a vulcanizing agent. A heat and vibration-insulating rubber composition containing only an oxide and containing zinc acrylate represented by the following structural formula (1) as a co-crosslinking agent, and heat resistance and prevention obtained by curing the rubber composition Providing vibration rubber.

  As described above, the present invention has excellent fracture characteristics, heat resistance, durability, and dynamic magnification (vibration isolation performance), and can be suitably used in a high temperature environment such as an automobile engine room. A rubber can be obtained.

  The heat and vibration proof rubber composition of the present invention contains natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) in a predetermined ratio as rubber components, contains only peroxide as a vulcanizing agent, and co-crosslinks. It comprises zinc acrylate as an agent.

  The rubber component includes NR and EPDM. At that time, the blending ratio of NR and EPDM is usually in the range of NR / EPDM = 70/30 to 45/55 in terms of mass ratio. If the ratio of EPDM is less than the above range, ozone resistance and heat resistance may be lowered, and if it is too much, dynamic magnification may be increased. The NR and EPDM may be appropriately selected from known ones and are not particularly limited.

  Further, in the present invention, the rubber component containing NR and EPDM is used as described above. However, as long as it does not deviate from the purpose, other rubbers such as a known synthetic rubber are used in addition to the rubber component as necessary. May be used in combination. Specific examples include butadiene rubber, styrene / butadiene rubber, isoprene rubber, butyl rubber, halogenated butyl rubber, chloroprene rubber, isobutylene / isoprene rubber, acrylonitrile / butadiene rubber, silicone rubber, acrylic rubber, epoxidized natural rubber, and acrylate butadiene rubber. Synthetic rubbers such as these and those in which the molecular chain ends of these synthetic rubbers or natural rubbers are modified, and one or more of them may be appropriately selected and used. When the amount of the rubber is compounded, it is preferably 20% by mass or less (0 to 20% by mass) based on the total amount of the rubber components.

  As the vulcanizing agent, only peroxide is used in the present invention. In the present invention, by peroxide-crosslinking the rubber component using only a peroxide as a vulcanizing agent, heat resistance and creep resistance at high temperatures are excellent as compared with the case of crosslinking using sulfur. Therefore, the heat resistance and durability of the anti-vibration rubber can be improved. As the peroxide, those normally used in this field can be blended, and specific examples thereof include dicumyl peroxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) -3, 5,5-trimethylcyclohexane, diisobutyryl peroxide, cumylperoxyneodecanoate, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di-sec-butylperoxydicarbonate, 1,1, 3,3-tetramethylbutylperoxyneodecanoate, di (4-t-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-hexylperoxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxy Oxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di (3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3- Tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexa Noate, di (4-methylbenzoyl) peroxide, t-butylperoxy-2-ethylhexanoate, di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, dibenzoyl peroxide 1,1-di (t-butylperoxy) -2-methylcyclohexa 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di (t-butylperoxy) cyclohexane 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl) propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3 , 5,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 2,5-di -Methyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate 2,2-di- (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl 4,4-di- (t-butylperoxy) valerate, di (2-t-butylperoxyisopropyl) ) Benzene, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydro Peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide , T-butyl hydroperoxide, and the like. In the present invention, di (2-t-butylperoxy Propyl) benzene, can be suitably used dicumyl peroxide. These can be used individually by 1 type or in mixture of 2 or more types. The compounding amount of these vulcanizing agents is usually 1 to 10 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount exceeds 10 parts by mass, the rubber is excessively cured, which may cause a decrease in elongation at break and a decrease in durability. If it is less than 1 part by mass, the crosslinking density decreases and There is a risk of lowering, deterioration of dynamic magnification, deterioration of compression set, deterioration of durability, and the like.

  In addition, in the range which does not deviate from the objective of this invention, sulfur can also be mix | blended as a crosslinking adjuvant. When mix | blending this crosslinking adjuvant, it is preferable to make the compounding quantity into the range of 0.1-0.5 mass part with respect to 100 mass parts of rubber components.

なお、メタクリル酸亜鉛は、防振ゴムとして重要な特性である圧縮永久歪みが上がってしまうため、本発明には適さない。上記アクリル酸亜鉛の配合量は、上記ゴム成分１００質量部に対し、通常２〜６質量部、好ましくは３〜５質量部である。配合量が６質量部を超えると、ゴムが硬化しすぎ、破断伸びの低下等を招くおそれがあり、２質量部未満になると、ゴムの架橋が十分になされず、破断強力の低下、動倍率の上昇、圧縮永久歪みの上昇等を招くおそれがある。 The co-crosslinking agent itself has no ability to generate crosslinking points, but is an additive that causes a crosslinking reaction in the rubber when used in combination with the above-described peroxide. It is preferable to use zinc acrylate represented by the formula (1).

Zinc methacrylate is not suitable for the present invention because compression set, which is an important characteristic as a vibration-proof rubber, is increased. The compounding quantity of the said zinc acrylate is 2-6 mass parts normally with respect to 100 mass parts of said rubber components, Preferably it is 3-5 mass parts. If the blending amount exceeds 6 parts by mass, the rubber may be excessively cured, resulting in a decrease in elongation at break. If it is less than 2 parts by mass, the rubber is not sufficiently crosslinked, resulting in a decrease in breaking strength and dynamic magnification. May increase, compression set may increase.

  In the present invention, the fatty acid ester is blended with the zinc acrylate together with the rubber component, thereby improving the dispersibility of the zinc acrylate with respect to the rubber component during kneading and improving the mechanical properties of the rubber after vulcanization. Can be made. Here, the fatty acid and alcohol constituting the fatty acid ester may both have a linear structure or a branched structure, may be either saturated or unsaturated, and the number of carbon atoms is not particularly limited. . In the present invention, a known fatty acid ester composed of a fatty acid having a chain length of 1 to 30 carbon atoms and an alcohol having a chain length of 1 to 30 carbon atoms can be used. May be ethyl stearate, propyl stearate, butyl stearate, ethyl palmitate, propyl palmitate, butyl palmitate and the like. These can be used alone or in combination of two or more. The compounding quantity of the said fatty acid ester is 0.02-1.2 mass part normally with respect to 100 mass parts of said rubber components, Preferably it is 0.2-0.6 mass part. If the blending amount exceeds 1.2 parts by mass, the rubber may be softened, the workability may be deteriorated, and the dynamic magnification may be deteriorated. If the blending amount is less than 0.02 parts by mass, the dispersibility improvement effect may not be obtained. is there.

  This fatty acid ester exhibits an effect of improving dispersibility even when blended separately with the above zinc acrylate at the time of kneading with the rubber component, but premixed with zinc acrylate in advance before kneading with the rubber component. Thereby, the dispersibility with respect to the rubber component of zinc acrylate can further be improved.

  Moreover, with respect to the rubber component, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, carbon, zinc white (ZnO), which are usually used in the rubber industry, if necessary within a range not impairing the effects of the present invention. ), Additives such as waxes, antioxidants, fillers, foaming agents, plasticizers, oils, lubricants, tackifiers, petroleum resins, UV absorbers, dispersants, compatibilizing agents, homogenizing agents, etc. Can be blended.

  As the oil, known oils can be used, and are not particularly limited. Specifically, process oils such as aromatic oils, naphthenic oils, paraffin oils, vegetable oils such as palm oil, alkylbenzene oils, etc. Synthetic oil, castor oil, etc. can be used. In the present invention, paraffin oil can be preferably used. These can be used alone or in combination of two or more. The amount of these oils is usually 15 to 45 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount deviates from the above range, the kneading workability may be deteriorated. When oil-extended rubber is used for the rubber component, the total amount of oil contained in the rubber and oil added separately during mixing may be adjusted within the above range.

Known carbon can be used, and is not particularly limited. Examples thereof include carbon black such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, MT, In the present invention, FEF can be preferably used. Moreover, these carbon blacks may be used individually by 1 type, and may use 2 or more types together. The compounding amount of these carbon blacks is 100 parts by mass of the rubber component.
Usually, it is 15-60 mass parts, Preferably it is 20-50 mass parts. When the blending amount exceeds 60 parts by mass, workability may be deteriorated, and when it is less than 15 parts by mass, adhesion may be deteriorated.

  In the present invention, from the viewpoint of promoting vulcanization, a vulcanization acceleration aid such as zinc white (ZnO) or a fatty acid can be blended. The fatty acid may be saturated, unsaturated, linear or branched fatty acid, and is not particularly limited as the carbon number of the fatty acid. For example, the fatty acid has 1 to 30 carbon atoms, preferably 15 to 15 carbon atoms. 30 fatty acids, more specifically, cyclohexane acid (cyclohexanecarboxylic acid), naphthenic acid such as alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acid such as neodecanoic acid), Saturated fatty acids such as dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, linolenic acid, resin acids such as rosin, tall oil acid, abietic acid, etc. Is mentioned. These may be used alone or in combination of two or more. In the present invention, zinc white and stearic acid can be preferably used. The compounding amount of these vulcanization accelerators is usually 1 to 10 parts by mass, preferably 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount exceeds 10 parts by mass, workability and dynamic magnification may be degraded, and if it is less than 1 part by mass, vulcanization delay may occur.

As the anti-aging agent, known ones can be used, and are not particularly limited, and examples thereof include a phenol type anti-aging agent, an imidazole type anti-aging agent and an amine type anti-aging agent. The compounding amount of these anti-aging agents is based on 100 parts by mass of the rubber component.
Usually 2 to 10 parts by mass, preferably 3 to 7 parts by mass.

When obtaining the rubber composition of the present invention, there is no particular limitation on the blending method of each of the above components, and all the component raw materials may be blended and kneaded at once, or each component may be divided into two or three stages. You may mix | blend and knead | mix. At that time, by premixing the zinc acrylate with the fatty acid ester before kneading the rubber component, the dispersibility of the zinc acrylate in the rubber component is further improved, and the mechanical properties of the resulting rubber are further improved. Can be made.
In the kneading, a kneader such as a roll, an internal mixer, a Banbury rotor or the like can be used. Furthermore, when forming into a sheet shape or a belt shape, a known molding machine such as an extrusion molding machine or a press machine may be used.

  Moreover, there are no particular limitations on the vulcanization conditions for curing the rubber composition, but vulcanization conditions can be generally employed at 140 to 180 ° C. for 5 to 120 minutes.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example.

[Examples 1-8, Comparative Examples 1-5]
First, zinc acrylate and a fatty acid ester were premixed at a blending ratio shown in Table 1. Next, in the formulation shown in Table 1, the rubber component, the mixture of zinc acrylate and fatty acid ester obtained above, and other additives were kneaded according to a conventional method, and the length was 120 mm × width 120 mm × thickness 2 mm. A sheet was produced. Thereafter, the sheet was vulcanized and cured under predetermined conditions to obtain an evaluation body of the heat and vibration proof rubber of the present invention. About the obtained rubber sheet, the physical property was evaluated with the following method. The evaluation results are shown in Table 2.

[Hardness (Hd)]
Conforms to JIS K 6253 (Type A) [Tensile elongation (Eb)]
JIS K 6251 compliant [Tensile strength (Tb)]
JIS K 6251 compliant [heat resistance]
In accordance with JIS K 6257, heat aging (1) is 100 ° C. for 96 hours, and heat aging (2) is 120 ° C. for 96 hours, and then the hardness (Hd) and tensile elongation ( Eb
), Tensile strength (Tb) was measured. For the hardness (Hd), the change value (degree) is expressed as the tensile elongation (
Eb) and tensile strength (Tb) indicate the rate of change (%).
[Compression set]
Conforms to JIS K 6262 [Static spring constant (Es) and dynamic magnification (Ed / Es)]
In accordance with JIS K 6385, Ed was measured at 15 Hz.
[Ozone resistance]
In accordance with JIS K 6259, the test piece was exposed to ozone under conditions of 40 ° C., 50 phr and 480 hours, and then the deterioration was evaluated by 20% static extension and 20% dynamic extension. The evaluation criteria were “good” when no cracks occurred, and “bad” when cracks occurred.

ＮＲ：天然ゴム、ＲＳＳ＃１
ＥＰＤＭ−１：ＥＮＢ含量 ３．５質量％、エチレン含量 ５９質量％
ＥＰＤＭ−２：ＥＮＢ含量 ４．５質量％、エチレン含量 ６６質量％
ＦＥＦカーボン：Ｎ５５０
老化防止剤：ＲＤ、６Ｃ
オイル：パラフィンオイル
過酸化物：ジ（２−ｔ−ブチルパーオキシイソプロピル）ベンゼン

NR: natural rubber, RSS # 1
EPDM-1: ENB content 3.5% by mass, ethylene content 59% by mass
EPDM-2: ENB content 4.5% by mass, ethylene content 66% by mass
FEF carbon: N550
Anti-aging agent: RD, 6C
Oil: Paraffin oil Peroxide: Di (2-t-butylperoxyisopropyl) benzene

Claims (7)

Natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) are contained as a rubber component in a mass ratio of NR / EPDM = 70/30 to 45/55, and only a peroxide is contained as a vulcanizing agent. And the heat-resistant vibration-proof rubber composition characterized by including the zinc acrylate shown to following Structural formula (1) as a co-crosslinking agent.

  The heat-resistant vibration-insulating rubber composition according to claim 1, comprising 2 to 6 parts by mass of the zinc acrylate with respect to 100 parts by mass of the rubber component.   The heat and vibration proof rubber composition according to claim 1 or 2, comprising a fatty acid ester.   The heat-resistant and vibration-proof rubber composition according to claim 3, wherein the zinc acrylate and the fatty acid ester are premixed and blended.   The heat and vibration-proof rubber composition according to claim 3 or 4, comprising 0.2 to 0.6 parts by mass of the fatty acid ester with respect to 100 parts by mass of the rubber component.   The heat and vibration-proof rubber composition according to any one of claims 1 to 5, comprising 15 to 45 parts by mass of oil with respect to 100 parts by mass of the rubber component.   A heat and vibration proof rubber obtained by curing the rubber composition according to any one of claims 1 to 6.