JPS6115892B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to sponge EPDM (ethylene-α-olefin-nonconjugated diene copolymer rubber) having excellent foaming properties and processing properties. Most of the demand for sponge rubber is for automobile applications, specifically for use around doors and trunk rooms, and to provide soundproofing and waterproofing properties to the interior and exterior of the vehicle. Conventionally, natural rubber, chloroprene rubber, styrene, butadiene copolymer rubber, etc. have been used as base materials for such sponge rubber, but EPDM has attracted attention due to its excellent weather resistance, heat resistance, and light weight, and is currently used as a base material for sponge rubber. It is in the process of being almost completely replaced by EPDM. However, when commercially available EPDM is used as the raw material rubber, it is difficult to balance the vulcanization rate and foaming rate, so current efforts are being made to improve the process by modifying compounding conditions, processing conditions, etc. . However, improvements in compounding conditions and processing conditions can only be effective within a very narrow range, and there is also the drawback that control during sponge production is difficult. As a result of intensive research to improve these shortcomings, the present inventors have found that the relationship between vulcanization rate and high foamability is influenced by the type and amount of the third component of EPDM from the viewpoint of raw material polymer. I found out. In general, the foaming phenomenon refers to the fact that a pre-blended foaming agent is raised above its decomposition temperature, and decomposed gas is generated from the foaming agent and the gas is encapsulated in the material. If the vulcanization speed of the material is slower than this foaming speed, the degree of curing of the material will be slow, and the generated gas will escape from the material and will not be incorporated into the material, resulting in a good, uniform sponge with a low specific gravity. No rubber is manufactured. On the other hand, if the vulcanization rate is too high, the degree of hardening of the material will proceed too much, and sufficient foaming will not occur, resulting in a sponge product with a high specific gravity, resulting in unsatisfactory results. Therefore, in order to manufacture the desired sponge product, it is necessary to balance the vulcanization rate and foaming rate.
It is necessary to design EPDM. Therefore, the present inventors conducted various studies regarding the type and proportion of the third component. First, we investigated ENB (ethylidene norbornene)-based EPDM by changing its ratio, but ENB-based EPDM still foams even when the ratio of ENB is reduced to a vulcanization rate that corresponds to the minimum allowable production rate. The vulcanization rate is too fast, making it impossible to obtain a good sponge product, and DCP (dicyclopentadiene)-based EPDM
Now, even if a considerable amount of DCP is introduced into the polymer, it is clear that the foaming rate is faster and the vulcanization rate cannot keep up with it.In any case, it is clear that the purpose of the present invention is not satisfied. It became. From the above points of view, the present inventors developed an ENB-based EPDM.
We continued our investigation based on the idea that EPDM, which has the features of both DCP-based EPDM and DCP-based EPDM, would give favorable results. First of all, what you can think of is ENB-based EPDM.
The aim is to achieve this goal by mechanically blending DCP-based EPDM. However, this method should be avoided if possible because of the complexity of production process control, the influence of quality variations in both polymers on the final physical properties, and the difficulty of solving problems when they occur. Therefore, the present inventors focused on an ENB-DCP-ethylene-α-olefin quaternary copolymer that uses two types of third component, and determined the total amount of the third component and
We have discovered that sponge rubber with unprecedented properties can be obtained only when the ENB/DCP ratio is limited to a specific ratio, and based on this knowledge, we have arrived at the present invention. That is, the present invention consists of an ethylene-α-olefin-dicyclopentadiene-ethylidene norbornene quaternary copolymer, the amount of unsaturation in the copolymer is 15 to 30 in terms of iodine value, and dicyclopentadiene and ethylidene norbornene are present. with an iodine value ratio of 1:1
A sponge rubber is provided by foaming and crosslinking an ethylene-α-olefin-nonconjugated diene copolymer rubber containing a ratio of 1:6 to 1:6. Examples of the α-olefin in the quaternary copolymer rubber of the present invention include propylene, 1-butene, 1-pentene, and 1-hexene, among which propylene is particularly preferred. The ratio of ethylene content to α-olefin content in the copolymer is a factor that has relatively little effect on foaming properties and can be in any range, but when the processing method of the product is taken into account, it may be in the slightly high ethylene content range. Preferably, 60 to 80 mol% ethylene, 20 to 80 mol% propylene
A range of 40 mol% is particularly preferred. The third component of the present invention is a combination of DCP and ENB, and other combinations, such as DCP and 1.4-HD (1.4-HD), which is a typical third component, are essential.
(hexadiene), a combination of ENB and 1,4-HD, etc. do not produce sufficient effects. The ratio of DCP and ENB in the copolymer rubber of the present invention is 1:1 to 1:6 as an iodine value ratio, preferably 1:1.5 to 1:5 (measured according to JIS K2543),
The total amount (unsaturation amount) is 15 to 30, preferably 18 to 27 in terms of iodine value. If the ratio of DCP and ENB is greater than 1:1, the specific gravity of the sponge will increase and the surface texture will deteriorate. If the ratio is less than 1:6, vulcanization will be too rapid and a good sponge will not be obtained. If the total iodine value is less than 15, the foaming rate exceeds the vulcanization rate, and if it exceeds 30, the vulcanization rate exceeds the foaming rate, and in neither case will a desirable result be obtained. Generally speaking, it is desirable that the Mooney viscosity of the quaternary EPDM of the present invention be higher in terms of extrusion characteristics during molding, mechanical properties of sponge rubber, and product shape retention.ML ¹⁰⁰ _1+
4
=70-140, preferably 90-120 gives good results. However, for Mooney viscosity,
The preferred range naturally changes depending on the formulation, and is not particularly limited to the above range. Other properties required of EPDM include the fact that excellent processing properties are required in terms of roll workability after Banbury processing, and that molecular weight distribution is the structural factor most affected by processing properties. It has also been found that the broader the molecular weight distribution, the better. The quaternary EPDM of the raw material rubber of the present invention is
It can be manufactured by a known method as shown in No. 7713. As a catalyst for producing the copolymer of the present invention, a so-called Ziegler type catalyst system can be used, but a combination of an organoaluminum compound and a vanadium compound is preferred, and the aluminum compounds include alkyl aluminum sesquichloride, trialkyl aluminum, dialkyl Aluminum monohalide and the like are preferred, and vanadium oxytrichloride, vanadium tetrachloride, vanadium trichloride, triethylvanadate and the like are preferred as vanadium compounds. The quaternary EPDM of the present invention may be used in admixture with other types of rubber, such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, butyl rubber, etc. Conventional vulcanizing agents such as sulfur and organic peroxides such as dicumyl peroxide can be used in the rubber-based sponge rubber formulations of the present invention. Further, if necessary, a common vulcanization accelerator compounded for sponge rubber can be used in combination with the vulcanizing agent. As blowing agents, inorganic blowing agents such as sodium bicarbonate, sodium carbonate, ammonium carbonate, N.
Conventional blowing agents can be used, such as nitroso compounds such as N'-dimethyl-N.N'-dinitroso terephthalamide, azo compounds such as azodicarbonamide, azobisisobutyronitrile, etc. Other usual fillers, softeners, and stabilizers can be used as necessary. Sponge rubber can be produced by known methods. That is, a method is used in which the ingredients are mixed with the rubber component using an oven roll mill, Banbury mixer, kneader, etc., and then foaming and crosslinking is carried out at a temperature that allows foaming and vulcanization. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Reference example In an autoclave reactor with a capacity of 200, n-hexane 80/hr, ENB740c.c./hr, DCP250c.c./hr and ethylaluminum sesquichloride 0.43g/hexane, vanadium oxytrichloride 0.06g as a polymerization catalyst. /・Introduce hexane and pressure 4Kg/
Continuous polymerization was carried out under the following conditions: cm ² G, temperature of 35° C., ethylene/propylene molar ratio in the gas phase of 1.3, and hydrogen concentration in the gas phase of 15% by volume. After adding a small amount of water as a reaction terminator to the polymerization liquid taken out from the reactor, the solvent was expelled from the system by steam distillation and dried in a finishing step. The rubber obtained was as follows. ML ¹⁰⁰ ₁₊₄ 98 Propylene content 26 moles Total iodine number 25.2 (ENB 20.1, DCP 5.1) This rubber was used as a sample in Experiment No. 3 of Example 1 below. The samples used in Experiment No. 2 and Experiments No. 4 to 17 were also produced in the same manner as above. Example 1 A rubber compound was prepared with the compounding ratio shown in Table 1.
The preparation method is to knead EPDM, zinc white, stearic acid, carbon black, oil, and CML #21 in a Banbury mixer, then add sulfur, vulcanization accelerator,
A blowing agent was added on a 10-inch roll machine to create a blend. This mixture was molded using an extruder and
Foam vulcanization was performed in hot air at ℃ for 6 minutes to obtain a sponge. Table 1 Compounding formula Part by weight EPDM 100 Zinc white 5 Stearic acid 1 FEF carbon black 60 SRF carbon black 60 Paraffin oil 75 CML #21 5 p・p'-oxybisbenzenesulfonylhydrazine (foaming agent) 4 Mercaptobenzothiazole 1 Di Pentamethylene lentithurum tetrasulfide
1 Zinc di-n-butyldithiocarbamate 1 Tetramethylthiuram disulfide 0.5 Tellurium diethyldithiocarbamate 0.5 Sulfur 2 The experimental conditions and results are shown in Table 2.

[Table] Comparisons were made using a total iodine value of about 25, and the examples showed high foaming properties and excellent surface texture. Example 2 A formulation was prepared using the same recipe as in Example 1, and vulcanization was performed under the same conditions to obtain a sponge. used
The total iodine value of EPDM was approximately 20. The experimental conditions and results are shown in Table 3.

[Table] Even when the total iodine number was set to 20, almost the same results as in Experimental Example 2 were obtained. Example 3 A formulation was prepared using the same formulation as in Example 1, and vulcanization was performed under the same conditions to obtain a sponge. used
The E/D iodine value ratio of EPDM was approximately 4/1.

[Table] It can be said that a range of 15 to 30 is preferable for the total iodine value.

Claims (1)

[Claims] 1 Consisting of an ethylene-α-olefin-dicyclopentadiene-ethylidene norbornene quaternary copolymer, the amount of unsaturation in the copolymer is 15 in terms of iodine value.
30 and containing dicyclopentadiene and ethylidene norbornene in an iodine value ratio of 1:1 to 1:6. Sponge rubber made by foaming and crosslinking an ethylene-α-olefin-nonconjugated diene copolymer rubber. .