JPS6136020B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an extrusion rubber composition made of ethylene propylene rubber with improved cold resistance. More specifically, the propylene content is 30-40% by weight.
An ethylene propylene ethylidene norbornene terpolymer (hereinafter referred to as
(referred to as EPDM) per 100 parts by weight of the rubber component.
The present invention relates to a rubber composition for extrusion with improved cold resistance, containing ~15 parts by weight of a hydrocarbon softener having a pour point of 0°C or less. In recent years, extruded rubber products for automobiles, building materials, water hoses such as radiator hoses and heater hoses, and wind gaskets called weather strips are required to have excellent weather resistance and ozone resistance. , EPDM or instead of traditional natural rubber, SBR, chloroprene rubber
Vulcanized rubber compositions having EPDM blended therein have been used. EPDM used for these extrusion applications generally has a polymer structure with a high ethylene content in order to provide entrainment properties when fed into an extruder and to enable high filler loading. However, as the ethylene content increases, the long ethylene chains cause crystallinity similar to that of polyethylene, resulting in poor cold resistance. In other words, hoses become hard during the winter, their rubber elasticity is impaired, and their rigidity increases, allowing air or water to leak from the joints of hoses, and making it difficult to assemble gaskets to windows. For these reasons, polymers with a high propylene content are sometimes used, but in this case, high loading is not effective because they have poor bite into the extruder.
The cost of the compound will rise, which will reflect on the cost of the product and make it unprofitable. The propylene content of currently manufactured EPDM is approximately 25 to 50% by weight, but the cold resistance varies greatly in this range as shown in Figure 1.
% or more, cold resistance is excellent, but if it is less than 35%, it rapidly deteriorates, and it is clear that the stiffness increases at relatively high temperatures. The present inventors have repeatedly researched the formulation of EPDM's polymer characteristics in the direction of improving low temperature properties within the range of propylene content that has excellent extrusion processability and high filling properties. It has been found that an extrusion rubber composition with excellent cold resistance can be obtained by selecting the species and the softening agent added during blending. Until now, EPDM used for extrusion applications has been selected to have a structure with a low propylene content in order to increase the extrusion speed as much as possible and fill in as much cheap filler as possible, as mentioned above, and there is a requirement for cold resistance. Currently, this problem has been solved by dry blending products with a structure with a high propylene content, but in this case, polymers with long ethylene chains still exist in proportion to the blend ratio. Although the cold resistance has been improved, the degree of improvement is not as high as expected, and in order to achieve a major improvement, it is necessary to significantly increase the proportion of polymers with a high propylene content. However, in this case, the physical properties are greatly reduced, the green strength of the unvulcanized rubber is greatly reduced, and the extrudability is impaired. The present inventors developed EPDM with various polymer structures.
As a result of extensive research, we found that by using a single copolymer and narrowing the molecular weight distribution, we were able to improve the randomness due to the propylene component and suppress crystallinity, unlike dry blending, and eliminate high molecular weight components. It has been found that cold resistance can be improved by this. Furthermore, the cold resistance differs depending on the type of the third component;
Generally, EPDM has a large number of branches, which prevents micro-Brownian motion at low temperatures, resulting in poor cold resistance, but ethylidene norbornene has relatively few branches, so it has been found that it has an advantageous effect on rubber elasticity at low temperatures. In terms of formulation, various auxiliary materials are added to vulcanized rubber in addition to rubber, but we investigated which of these has the greatest effect on cold resistance and found that it imparts processability to the rubber compound. Therefore, the added softener has the greatest effect.As a result of investigating the pour point of the softener and the low-temperature properties of the vulcanized rubber using it, it was discovered that the lower the pour point of the softener, the better the cold resistance.The present invention reached. That is, the present invention is an ethylene propylene ethylidene norbornene terpolymer having a propylene content of 30 to 40% by weight, a Q value of 3 or less, preferably 2.5 or less, and a Q value of 3 or less, preferably 2.5 or less, and a propylene content of 30 to 40% by weight. An extrusion rubber composition with improved cold resistance, containing 1 to 150 parts by weight, preferably 50 to 120 parts by weight, of a hydrocarbon softener with a pour point of 0°C or lower, preferably -15°C or lower, per 100 parts by weight of the rubber component. It is. The EPDM used in the present invention is obtained by terpolymerizing ethylene propylene and a non-conjugated diene using a catalyst well known in the technical field of the present invention, particularly a Ziegler-Natsuta catalyst, by a well-known method. Manufactured. The method for producing EPDM with a narrow molecular weight distribution, which is particularly effective in the present invention, is not limited to the present invention and can be carried out by any method commonly used by those skilled in the art. For example, it is produced by keeping the polymerization temperature as low as possible, preferably below 40°C, and using a normally used molecular weight regulator such as hydrogen in a larger amount than usual. Furthermore, the usage ratio of organic aluminum compounds and vanadium compounds, which are commonly used Ziegler-Natsuta catalysts, such as A ₂ Et ₃ Cl ₃ /VOC ₃
The ratio is maintained at 5 moles or more, preferably 10 moles or more, or a polymerization accelerator such as benzotrichloride, ethyl trichloroacetate, n-butylperchlorocrotonic acid or hexachlorocyclopentadiene is used alone or in combination during production. Addition can also be made by adding a catalyst that narrows the molecular weight distribution, such as a Lewis base such as pyridine, acetone, cyclohexanone, or ethyl acetate, either alone or in combination. The propylene content of the EPDM used in the present invention is between 3 and 40% by weight. If it is less than 30% by weight, the cold resistance is too poor, so even if the molecular weight distribution is narrowed and ethylidene norbornene is used as the third component, the cold resistance will be improved, but the increase in winter hardness will still be large, and 40% by weight In this case, the extrudability of the rubber itself is poor and the strength is low, so that the purpose of improving cold resistance is lost. Furthermore, the molecular weight distribution of EPDM used in the present invention is
The Q value measured by GPC (gel permeation chromatography) is 3 or less, preferably 2.5 or less. Regarding the relationship between molecular weight distribution and cold resistance, the lower the Q value, the better the quality, but 1.5 to 2.5 is preferred from the viewpoint of manufacturing. Moreover, if it is 3 or more, the effect of improving cold resistance is small. The hydrocarbon softener used in the present invention can be paraffinic, naphthenic, or aromatic, and has a pour point of 0°C or lower, preferably -15°C.
℃ or less, and the amount added is 1 to 150 parts by weight, preferably 50 to 120 parts by weight, in order to improve the texture of the vulcanized rubber surface during extrusion processing. If necessary, the rubber composition of the present invention may contain additives such as reinforcing agents such as carbon black, fillers, stearic acid, zinc white, sulfur vulcanization accelerators as vulcanizing agents, and anti-aging agents. can. EPDM and these auxiliary materials can be mixed using a two-roll machine, a Banbury mixer, a kneader, an explorer, or the like. Extrusion molding is carried out using a general rubber extruder, and vulcanization is carried out using a general rubber extruder.
It is possible to vulcanize UHF, PCM, LCM, HAV, etc. by a continuous vulcanization method or an extruded unvulcanized material by a direct steam vulcanization method using steam or an indirect vulcanization method. The present invention will be explained in more detail with reference to Examples below, but it goes without saying that the present invention is not limited thereto. Example 1 Ethylene-propylene non-conjugated diene terpolymer copolymers having the propylene content, molecular weight distribution (Q value), third component species, and iodine value shown in Table 1 below were used as samples. Pour point for hydrocarbon softeners. A paraffin softener at 41°C was used. Kneading was carried out using a BR type test Banbury and two rolls. For 100 parts of rubber, 55 parts of HAF black, 55 parts of FEF black, 65 parts of softener, 5 parts of zinc white, 1 part of stearic acid, 1.5 parts of sulfur, and N- 1.5 parts of cyclohexylbenzothiazolesulfenamide, 0.5 parts of tetramethylthiuram disulfide, 0.5 parts of dipentamethylenethiuram hexasulfide, and 1.0 part of zinc di-n-butyldithiocarbamate were added and kneaded. Vulcanization was carried out by press vulcanization at 160°C for 20 minutes. Cold resistance was measured by Gehman low-temperature torsion test and low-temperature compression set test, and the measurement method was based on JISK6301. In the Gehman torsion test, the T ₂ value was adopted as a physical property value that is close to the winter temperature range of particularly cold regions. In addition, as a low-temperature hardness test, the hardness difference between 25°C and -20°C was measured. The extrusion test was performed using a 40mmφ extrusion test material.
Extrusion speed and surface texture were evaluated using a 6 mmφ rod die at a screw rotation speed of 60 rpm.

【table】

[Table] Example 2 As EPDM, a polymer having a propylene content of 30.3 wt%, a Q value of 2.83, and a third component of ethylidene norbornene was used. As comparison data, propylene content 30.2wt%, Q
A material with a value of 4.55 and a third component of ethylidene norbornene was used, and kneading, blending, vulcanization, and physical property measurements were performed in the same manner as in Example 1.

[Table] Example 3 EPDM with propylene content of 35.4wt% Q value
3.0 The third component used was ethylidene norbornene. Propylene content as comparison material
Using the third component dicyclopentadiene having a Q value of 3.6 wt % and a Q value of 3.5, kneading, blending, vulcanization, and physical property measurements were carried out in the same manner as in Example 1.

[Table] Example 4 The structure and various properties of EPDM are shown in Table 4. EPDM
(1) has a propylene content of 30wt% or less and has excellent extrusion properties, but has significantly poor cold resistance;
has a propylene content of 40wt or more and has excellent cold resistance, but is inferior in extrudability and mechanical strength. EPDM
(3) has a wide molecular weight distribution and poor cold resistance. of the present invention
EPDM(4) has excellent cold resistance, strength, and extrusion processability.

【table】

[Table] Example 5 EPDM has a propylene content of 32.4wt% and a Q value
2.9. The third component was a polymer of ethylidene norbornene with a pour point of -41°C as a softener, and a comparative sample with a pour point of 8°C. The other operations were the same as in Example 1.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows the results of the Gehman torsion test of ethylene propylene rubber vulcanizates, and shows the temperature at which the stiffness at room temperature doubles in the low temperature range for each propylene content.

Claims (1)

[Claims] 1 1 per 100 parts by weight of the rubber component to an ethylene-propylene-ethylidene norbornene terpolymer with a propylene content of 30 to 40% by weight and a molecular weight distribution of 3 or less in the ratio of weight average molecular weight to number average molecular weight.
A rubber composition for extrusion with improved cold resistance containing ~15 parts by weight of a hydrocarbon softener having a pour point of 0°C or less.