KR20040000852A - Rubber Compound for engine mount - Google Patents

Abstract

PURPOSE: A rubber composition for an engine mount is provided, to improve heat resistance and durability and to reduce the deterioration of physical properties after aging for preventing the deterioration of an engine room due to a high temperature. CONSTITUTION: The rubber composition comprises 100 parts by weight of ethylene propylene diene rubber containing 6-9 wt% of ethylidene norbornene and 50-70 wt% of ethylene; 0.5-2.0 wt% of a vulcanizing agent; 0.3-2.5 wt% of an accelerator; and 30-60 parts by weight of a filler. Preferably the vulcanizing agent is sulfur; the accelerator is N-cyclohexyl-2-benzothiazylsulfenamide, tetramethyl thiuram disulfide or their mixture; and the filler is carbon black with a particle size of 27-70 micrometers.

Description

Rubber compound for engine mounts {Rubber Compound for engine mount}

The present invention relates to a rubber composition for an engine mount, and more particularly, to a vulcanizing agent in ethylene propylene diene rubber (EPDM) having 6-9 wt% of ENB (ethylidene norbornene) content and 50-70 wt% of ethylene content. The present invention relates to a rubber composition containing a specific amount of accelerators, fillers and other additives. The rubber composition has excellent heat resistance, deterioration in physical properties and durability after aging compared to natural rubber, and is suitable for use in an engine mount of an automobile. Proper response to high temperatures in the room, as well as improving the vehicle's marketability in high temperature areas, ensure long-term durability.

Anti-vibration rubber, which supports the engine of the vehicle and suppresses the transmission of vibration generated from the engine to the rider, is an important element in the development of the vehicle's N.V.H.

Among them, the engine mount is a part that must have high static stiffness and low dynamic stiffness at the same time in order to support the weight of the engine and the transmission. In addition, since the repetitive heavy load is input while driving the vehicle, the durability of the rubber to withstand it is required at the same time. In order to perform these conflicting complex elements, natural rubber (hereinafter referred to as NR) is used as a raw material, and a product using a compound containing a filler and a vulcanizing agent is manufactured.

At this time, the physical properties such as the durability and heat resistance of the compound is changed according to the purity of the rubber used and the type of filler and vulcanizing agent is the key to set the mixing conditions according to the intended purpose.

Since the anti-vibration rubber is located in a high temperature engine room, it is required to improve its heat resistance and to secure a certain mechanical property to support the repeated mechanical load. In order to solve this problem, based on NR having excellent mechanical properties, the heat resistance is improved by changing the mixing conditions. However, NR has a problem in that its use range does not exceed 100 ° C. because it has a double bond that is susceptible to heat in the rubber molecules.

Recently, due to the high performance of the vehicle and the advancement of technology according to the regulation of the exhaust environment, the temperature of the engine room is increasing more and more. It was confirmed that aging is occurring.

Basically, the development of engine mounts using chloroprene rubber and EPDM rubber, which are resistant to heat, has been developed. However, application to engine mounts has been difficult due to weak mechanical properties and deterioration of dynamic performance at low temperatures. .

Accordingly, the present inventors have tried to develop a rubber composition suitable for engine mounting because of excellent heat resistance and long-term durability, and as a result, an ENB content of 6 to 9 wt% and an ethylene content of 50 to 70 wt% are EPDM (ethylene propylene diene rubber). In order to overcome the physical properties of the conventional EPDM, a specific content of additives was selected to prepare a rubber composition, and the obtained composition had better heat resistance, lowered physical properties after aging and durability compared to natural rubber, so The present invention has been completed by finding out that it is suitably applicable.

An object of the present invention is to provide a rubber composition excellent in heat resistance, deterioration in physical properties after aging and durability.

Still another object of the present invention is to provide a rubber composition having improved durability to satisfy the performance required for an engine mount for an automobile.

The above object and another advantage is that the ethylene propylene diene rubber (EPDM) having an ENB content of 6 to 9% by weight and an ethylene content of 50 to 70% by weight includes vulcanizing agents, accelerators, fillers and other additives in specific contents. By providing a rubber composition.

The present invention is based on 100 parts by weight of EPDM (ethylene propylene diene rubber) having an ENB content of 6 to 9% by weight and an ethylene content of 50 to 70% by weight,

0.5 to 2.0 parts by weight of a vulcanizing agent; 0.3 to 2.5 parts by weight of accelerator; Provided is a rubber composition containing 30 to 60 parts by weight of a filler.

Hereinafter, the present invention will be described in more detail.

The rubber composition of the present invention has a feature that the durability is improved to maximize the heat resistance of EPDM and to satisfy the performance required in the engine mount for automobiles.

In the present invention, since the rubber used in the engine mount is a copolymer of ethylene and propylene represented by the following formula (1), and the main chain has no double bond, the stability is high, so EPDM is selected as a material having excellent ozone resistance and heat resistance.

As shown in the above formula, since EPDM has no double bond in the main chain, it does not form a vulcanized structure on its own and a third component called ethylidene norbornene (ENB) is introduced. EPDM used in this study has high ENB content, high molecular weight and narrow molecular weight distribution, which is suitable for achieving the excellent mechanical properties required for vehicle anti-vibration rubber. In addition, it was selected as the raw material rubber because it is a grade (Grade) to improve the low-temperature performance by adjusting the content ratio of ethylene and propylene.

Until now, the use of EPDM rubber has been mainly used for weather strips requiring light resistance, and has not been applied to engine mounts requiring dynamic damping performance and durability against heavy loads. Therefore, it is important to select the appropriate raw material grade and adjust the mixing conditions. The overall characteristics of EPDM rubber are its excellent ozone resistance and excellent weather resistance without the use of ozone-preventing agents and good heat resistance, so it can be used at temperatures up to 150 ℃. Its low-temperature performance is superior to heat-resistant rubbers such as CR. In addition, it has good advantages such as good resistance to polar solvents and high compatibility with carbon black.

However, EPDM can control various physical properties and processability according to polymerization ratio of ethylene and propylene, ENB content, oil content, etc., and therefore, appropriate grade should be selected according to the purpose of use.

In the present invention, an ENB content of 6 to 9% by weight and an ethylene content of 50 to 70% by weight of EPDM (ethylene propylene diene rubber) were used. When the content of ENB is less than 6% by weight, it is difficult to obtain the physical properties required for the engine mount because there are few reaction sites for vulcanization of rubber, and when it is included in more than 9% by weight, the viscosity of the raw material rubber is high, which makes processing difficult. . In addition, when the ethylene content is 50 wt% or less, the orientation of the molecular structure is difficult when less than or equal to the physical property, and thus, mechanical properties are degraded. When the ethylene content is 70 wt% or more, the problem of lowering the dynamic performance at low temperature is not preferable.

According to a preferred embodiment of the present invention, a rubber containing ENB content of 7.8 wt% and 75 wt% oil was used as Keltan 7441 of DSM as EPDM.

On the other hand, the EPDM has a problem that the vulcanization is slow and the durability is lowered compared to the existing NR, and the dynamic characteristics are increased, and various additives are used to solve this problem.

Sulfur and accelerators are added to effect crosslinking with sulfur of the EPDM. However, the crosslinking system is the most important factor affecting the determination of the heat resistance of the rubber, and the use of sulfur is improved, the heat resistance is improved, but the durability is lowered, so the compounding ratio with the accelerator must be properly adjusted. In addition, the carbon black used as the filler has a great influence on the initial performance of the rubber and its aging characteristics depending on the type and the amount of the compounding thereof, so the selection thereof is an important technical factor.

Sulfur was added in an amount of 0.5 to 2.0 parts by weight based on 100 parts by weight of EPDM to form the vulcanizing system of the present invention. As the accelerator, all promoters commonly used in this field may be used, for example, CBS (N-Cyclohexyl-2). -benzothiazyl-sulfenamide) and TT (Tetra methylthiuramdisulfide) were adjusted to 0.3 to 2.5 parts by weight of the mixture.

In this case, when the amount of sulfur used is 0.5 parts by weight or less, the durability of the rubber is lowered to satisfy the required level, and when blended to 2.0 parts by weight or more, the heat resistance to the required use limit temperature is not satisfied. Accelerator should be blended properly according to the vulcanization speed. If the vulcanization rate is over 2.5 parts by weight, the vulcanization speed is too fast. Therefore, the product is defective due to scorch generation during the production process. This slows down the production speed and raises the manufacturing cost.

Fillers Also, all fillers usable in this field may be used and are not particularly limited in the present invention. For example, in the embodiment of the present invention, carbon black was used. The filler is an important factor influencing the mechanical properties of the rubber is different depending on the size of the particles and the degree of development of the structure. The rubber composition used for the engine mount should be designed in the direction of increasing mechanical properties and reducing heat, and in particular, in the case of EPDM rubber, the mechanical properties of the raw material rubber itself should be low, and a filling system that can reinforce it as much as possible should be determined. .

Therefore, in the present invention, carbon black is added to obtain a certain level of mechanical properties, and General Purpose Furnace Black (GPF), High Abration Furnace Black (HAF), and Semi-reinforcing Furnace Black (SRF) are mixed alone or in an appropriate ratio. Can be used. Carbon black of N-330-765 (27 micrometers-70 micrometers) was used according to the classification method of carbon black. When using carbon black of 330 or less, it has a small particle, so even if the same amount is added, the number of particles increases, so that a large amount of heat is generated between carbon blacks, which causes a problem of the occurrence of CRACK of rubber. On the other hand, when using 765 large particles or more, the reinforcing effect on the rubber is lowered, so its use is not preferred.

In addition, the filling amount of the filler was blended in an amount of 30 to 60 parts by weight based on 100 parts by weight of the EPDM resin composition as a factor closely related to the mechanical properties of the rubber. When the amount of the filler used is too small, deterioration of mechanical properties occurs, and when too much amount is added, there is a problem that the flexibility of the rubber is lowered and the dynamic performance at low temperature is deteriorated.

In addition, additives which may be added in the present invention are conventional ones, for example, active agents, vulcanizing aids and active agents, etc., which may be added within an appropriate content range. Zinc oxide may be used as the active agent, stearic acid may be used as a vulcanizing aid, and polyethylene glycol (PEG) may be used as the active agent.

In addition, the EPDM resin composition of the present invention will not be described separately herein, the production method can be prepared according to the manufacturing method commonly used in this field. For example, it is possible to manufacture by a conventional mechanical kneading method.

As described above, the rubber composition of the present invention can produce an EPDM engine mount with significantly improved heat resistance compared to an engine mount using a conventional NR. Therefore, the engine mount according to the present invention can contribute to the appropriate response to the high temperature of the engine room according to the development of the vehicle, the improvement of the merchandise and the long-term durability quality of the vehicle used in the high temperature region.

Although this invention is demonstrated based on an Example, this invention is not limited by an Example.

In order to prepare a rubber composition for engine mounts with improved heat resistance, the rubber was mixed as shown in Table 1 to prepare a specimen, and the results were compared and evaluated.

(Parts by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Raw material rubber NR - - - - - - 100 EPDM 100 100 100 100 100 100 - Crosslinking agent S 0.5 2 0.5 0.5 0.5 0.5 0.75 Vulcanization Stearic acid 2 2 2 2 2 2 2 accelerant CBS One 1.2 One One One One 1.2 TT 2 0.3 2 2 2 2 0.3 Filler SRF 40 40 - - 30 60 40 HAF - - 40 - - - - ZPF - - - 40 - - - Active agent ZnO 2.5 2.5 2.5 2.5 2.5 2.5 2.5 PEG 0.5 0.5 0.5 0.5 0.5 0.5 - Anti-aging RD - - - - - 1.5 3C - - - - - - One ZnO: Zinc OxidePEG: Poly Ethylene GlycolRD: Polymerized 2,2,4-trimethyl-1,2 dihydroquinoline3C: N-Phenyl-N'-isopropyl-p-phenylenediamine SRF: Semi-Reinforced Furnace BlackHAF: High Abrasion Furnace BlackGPF: General Purpose Furnace BlackCBS: N-cyclohexyl-2-benzothiazyl-sulfenamideTT: Tetra methylthiuramdisulfide

# Preparation of the rubber composition

Comparative Example 1

The natural rubber was kneaded for 2 minutes with 40 parts by weight of carbon black after 2 minutes using a Bunbury mixer (BANBURY MIXER, KOBE STEEL.CO). Thereafter, stearic acid, zinc oxide and an anti-aging agent were mixed and kneaded for 2 minutes to prepare a carbon master batch (CMB). The vulcanizing agent was dispersed and mixed in the CMB prepared by using a roll mixer.

<Example 1>

The raw rubber was blended using EPDM, 0.5 parts by weight of sulfur was added and SRF was mixed with the filler.

<Example 2>

In order to evaluate the effect of the vulcanization system, a large amount of sulfur was used as an EPDM raw material.

<Example 3>

EPDM was used as a raw material, and HAF with small particles was used as a filler.

<Example 4>

EPDM was used as a raw material, and a large particle GPF was used as a filler.

Example 5

A small amount of filler was added to EPDM as a raw material to prepare a rubber composition.

<Example 6>

A rubber composition was prepared by adding a large amount of filler to EPDM.

Experimental Example

After preparing the vulcanization specimens by measuring the appropriate cure time using a rheometer (Rheometer, Monsanto R100) using a press (Toyo Seiki co. Ltd) at 210kgf / cm ² at 165 ℃ It was.

In order to evaluate the rubber specimens and products manufactured as described above, the following items were tested to compare the results.

Hardness: measured according to KS M 6784.

Tensile strength, elongation and modulus: measured with dumbbell No. 3 in accordance with KS M 6782.

-Evaluation of aging properties: Record changes in physical properties after aging at 70 ° C for 72 hours.

Flexural Crack Test: Evaluate the occurrence and growth rate of flexural cracks in accordance with KS M 6791. The growth rate, however, measures the number of times the crack reaches 5 mm.

-Heat resistance: The engine mount parts were manufactured and their heat resistance was evaluated.

Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Hardness (Hs) 44 45 44 44 42 50 45 Tensile strength (kgf / cm ² ) 175 95 130 160 135 210 300 % Elongation 700 395 405 650 750 350 630 Modulus (kgf / cm ² ) 31 44 55 39 28 59 30 Flexural crack Occur 3,000 4.2 thousand 2.8 thousand 2.5 thousand 2.2 thousand 4,000 5,000 growth 0.5 thousand 1.8 thousand 0.4 thousand 0.5 thousand 0.5 thousand Two thousand 2.5 thousand % Change after aging (120 ℃ * 96h) Hardness (Hs) 3 5 4 3 3 3 8 The tensile strength -17 -14 -9 -20 -15 -22 -85 Elongation -15 -45 -30 -25 -12 -25 -65 Modulus 28 30 40 30 25 38 32 Heat resistance cycle 350,000 200,000 280,000 300,000 260,000 420,000 100,000

According to Table 2, it was found that the rubber composition of the present invention is significantly superior in heat resistance compared to the existing natural rubber, the physical properties after aging and excellent durability. In the results of the above table, the composition of the present invention showed a slight degradation of the basic physical properties and durability, but the physical properties of the target 120 ℃ aging rather showed that the EPDM rubber of the present invention is superior. In particular, it can be seen that the product exhibits an increased performance of up to 4.2 times compared to the natural rubber of the comparative example. Therefore, it was confirmed that by developing a shape suitable for the EPDM material, it is possible to develop an engine mount that satisfies the vehicle condition.

Therefore, according to the present invention, a rubber composition containing an appropriate amount of additives was prepared in the EPDM rubber, and the obtained composition exhibited significantly superior heat resistance compared to conventional natural rubber, and significantly improved physical properties compared to conventional general EPDM. Confirmed. As a result, it can be suitably applied to the engine mount of the vehicle, thereby preventing the fatal aging of the rubber generated in the vehicle used in the high temperature room of the engine room, thereby prolonging its life.

Claims (4)

With respect to 100 parts by weight of ethylene propylene diene rubber (EPDM) having an ENB content of 6 to 9% by weight and an ethylene content of 50 to 70% by weight, 0.5 to 2.0 parts by weight of a vulcanizing agent; 0.3 to 2.5 parts by weight of accelerator; EPDM rubber composition for automobile engine mounting, characterized in that 30 to 60 parts by weight of the filler is included. The method of claim 1, wherein the vulcanizing agent is sulfur (S), the promoter is CBS (N-Cyclohexyl-2-benzothiazyl-sulfenamide) and TT (Tetra methylthiuramdisulfide) alone or a mixture thereof EPDM resin composition. 2. The EPDM rubber composition according to claim 1, wherein the filler is carbon black, wherein the carbon black has a size of N-330 to 765 (27 to 70 µm) according to ASTM classification. The EPDM rubber composition according to claim 1, wherein the composition further contains a conventional active agent or a vulcanizing aid.