JP4370182B2 - Rubber composition and weather strip for automobile using the rubber composition - Google Patents

Description

  The present invention relates to a rubber composition suitable as a material for a weather strip for automobiles, and more particularly, a rubber composition that can be reduced in weight without deteriorating physical properties and processability (moldability), and the rubber composition as a raw material. The present invention relates to an automobile weather strip.

  The ethylene-α-olefin-nonconjugated polyene copolymer rubber generally called EPDM is excellent in weather resistance and ozone resistance, and is widely used as a material for various sealing materials, particularly automobile weather strips. Yes.

  In recent years, in connection with the regulation of exhaust gas from automobiles, the weather strips for automobiles, which are seal parts, are also required to be reduced in light of demands for reducing the fuel consumption of automobiles and reducing the weight of vehicle bodies.

  As an automobile weather strip that meets such demands for weight reduction, for example, the one described in Patent Document 1 has been proposed.

In the technique described in Patent Document 1, crystalline polyethylene is added to suppress a decrease in physical properties due to a reduction in specific gravity (foaming), so that weight reduction is achieved so that the specific gravity is about 0.95 to 1.0. At the same time, the physical properties such as hardness, strength and elongation are made compatible so as to satisfy the required characteristics.
Japanese Patent No. 3417333 (FIG. 1)

  However, the method of adding crystalline polyethylene to the rubber composition as described in Patent Document 1 has poor processability, that is, extrudability when extruding a weather strip for automobiles having a uniform cross-sectional shape. There is concern about the instability of the extruded cross-sectional shape due to the deterioration of quantity variation and shape retention.

  In terms of physical properties, permanent distortion tends to deteriorate with the crystallization of crystalline polyethylene, and there is still room for improvement in improving the durability of the weather strip.

  In addition, when it is desired to promote further weight reduction by foaming, it becomes more difficult to stabilize the cross-sectional shape of the extrusion due to the deterioration of the extrusion discharge amount and the deterioration of foam variation due to high foaming, and the deterioration of shape retention during extrusion. There is a problem of becoming.

  The present invention has been made paying attention to such a problem, and intends to provide a rubber composition excellent in material properties while assuming the weight reduction which is an intended purpose. In particular, extrudability, which has been a problem in the past, that is, excellent discharge durability and shape retention, as well as improved permanent set, as well as durability without reducing physical properties such as elongation and stress. A rubber composition is provided.

  The invention according to claim 1 is an EPDM ethylene-propylene-nonconjugated polyene copolymer having the following formula (1) when the polymer structure index is Y and the ethylene content is T (wt /%). And an ethylene-propylene-nonconjugated polyene copolymer (A) having Y = 20 to 25 and an ethylene-propylene-nonconjugated polyene copolymer (B) having Y = 10 to 15 (A) / (B) = 1 to 40/99 to 60 (both numerical values are wt%), a rubber composition having a hardness of 55 (A) or higher obtained by foaming and crosslinking an uncrosslinked rubber composition. And

Y ≦ 1.1 (0.48T-13.19) (1)
The polymer structure index Y is a viscoelastic parameter, which is an index derived from the temperature dependence of viscosity as described later , and can be determined as shown below. First, a complex viscosity η is used under the measurement conditions of a temperature of 60 ° C.-80 ° C.-100 ° C., a frequency of 10.47 rad / s, and a distortion of 6.98% using “RPA2000 manufactured by Alpha Technologies, Inc.” as a viscoelasticity measuring device. * Measure (Pa · s). Then, the value of the complex viscosity η * obtained by the measurement is substituted into the following equation (2) to obtain X, and the polymer structure index Y is obtained by substituting the value of X into the equation (3). . Incidentally, formula (2), (3) T K in the temperature (K), R is the gas constant (8.314JK ^-1 mol ^-1).
η * = Aexp (X / RT _K ) (2)
Y = X / 1000 (3)
The ethylene content T refers to the weight ratio (wt%) of ethylene contained in the ethylene-propylene-nonconjugated polyene copolymer .

  Examples of polyene copolymers of ethylene-propylene-nonconjugated polyene copolymers include cyclic nonconjugated polyenes such as 5-ethylidene-2-norbornene, gincopentadiene, 5-vinyl-2-norbornene, norbornadiene, and methyltetrahydroindene. In addition, 1.4 hexadiene, 7-methyl-1.6-octadiene, 4-ethylidene-8-methyl-1.7-nonadiene, 4-ethylidene-1.7-undecadiene, 4.8-dimethyl-1.4 It is possible to use chain non-conjugated polyenes such as .8-decatriene.

  Of course, these non-conjugated polyenes can be used alone or in combination of two or more.

  The structural unit (non-conjugated polyene content ratio) of the non-conjugated polyene is 1 to 20 wt%, preferably 1 to 15 wt%, more preferably 5 to 11 wt%.

  As is clear from the above, the present inventors blended the special copolymer (A) and the copolymer (B) at a specific ratio, so that the conventional problems described above can be performed at once. I found that it can be solved.

  The hardness after foaming and crosslinking is more preferably 55 to 85.

  Moreover, the blend ratio of the copolymer (A) and the copolymer (B) is also (A) / (B) = 1 to 35/99 to 65 (all numerical values are wt). %) Is more desirable to limit the range.

  Further, considering that the main purpose is weight reduction, as described in claim 3, it is more desirable that the specific gravity is 1.1 or less.

  As described in claim 4, such a rubber composition is extremely suitable as a material for automobile weather strips that are particularly required to have weather resistance.

  In addition, as an application example of the weather strip assumed here, for example, in addition to a door glass run, a welt portion of a weather strip for a trunk lid, the same welt portion of a welt body side, a hood seal, and the like are conventionally used. It shall be applied to the part that was made of rubber.

  The polymer structure index Y described above is an index derived from the temperature dependence of viscosity. Therefore, it is verified that when the polymer structure index Y is different, the chemical structure of EPDM (ethylene weight ratio, arrangement of each repeating unit in the polymer chain, average molecular weight of the polymer chain, molecular weight distribution, etc.) is also different.

  In the extrusion process in an extrusion process of an automobile weather strip or the like, the material is transported by a screw in the process of moving from the feed zone → the cylinder → the head → the base. In the process, various temperature histories are received from the charging of the material to the discharging.

  In the case of a material whose viscosity of compounded rubber is easily affected by temperature changes (that is, when the polymer structure index Y of the rubber component is large), the fluidity of the rubber tends to change, so the extrusion fluidity varies due to slight differences in the extrusion environment. Cheap.

  A large polymer structure index Y means that the temperature dependence of the EPDM material itself is high. In other words, the polymer chain contains many components having high temperature dependence (crystallization components). It is nothing but a trend. It has been verified that a compound containing EPDM having a large temperature dependency is greatly influenced by the temperature dependency of the EPDM itself, the dispersion of the extrusion discharge amount is large, and the permanent distortion tends to deteriorate due to the influence of the crystallization component. ing. For this reason, the polymer structure index Y of EPDM itself is desired to be relatively small.

  In addition, as a characteristic of EPDM, the higher the ethylene weight ratio, the higher the tendency to show stress. On the other hand, the higher the ethylene weight ratio, the easier it is to crystallize and the polymer structure index Y increases.

  For this reason, the present inventor assumes that the EPDM having a chemical structure in which the polymer structure index Y is a relatively small value even when the ethylene weight ratio in the polymer chain of the EPDM is large is used. The condition was found to be Y ≦ 1.1 (0.48T-13.19) in the above formula (1).

  In addition, as described above, the copolymer (A) with Y = 20-25 greatly contributes to the improvement of stress, hardness and elongation, while the copolymer (B) with Y = 10-15 ) Significantly contributes to the improvement of so-called extrudability, such as stability of the extrusion discharge amount and shape retention, in addition to permanent distortion.

  That is, in the invention described in claim 1, the copolymer (A) having Y = 20 to 25 is used as a component for positively improving the hardness, stress and elongation. Compared with crystalline polyethylene, which has been used for the same purpose, this component is not crystallized in the entire polymer chain, and only produces partial crystals within the molecule. As a result, it is considered that it can contribute to the improvement of hardness and elongation without deteriorating the extrudability, and can suppress the deterioration of permanent distortion.

  On the other hand, in the copolymer (B) where Y = 10 to 15, the ethylene component is randomly arranged as compared with that of the copolymer (A), and particularly functions as a component for improving permanent set and extrudability. To do.

  Then, an uncrosslinked rubber composition obtained by blending the copolymers (A) and (B) at a ratio of (A) / (B) = 1 to 40/99 to 60 (both numerical values are wt%). A rubber composition having a hardness of 55 (A) or more is obtained by foaming and crosslinking.

  Here, as described above, the copolymer (B) is a main component that determines the permanent distortion of the rubber composition and the stability of the extrusion discharge amount. In addition, by satisfying the condition that the hardness is 55 or more, it is possible to obtain a lightweight rubber composition having physical properties suitable particularly as a weather strip that is a sealing material for automobiles.

  That is, by satisfying all the conditions of claim 1, the required properties such as permanent strain and stress, which are the main physical properties of the rubber composition, can be satisfied, and at the same time, variations in extrusion discharge amount can be eliminated as extrusion processability. In addition to stabilizing the extrusion discharge amount, the shape retainability, which is also extrusion processability, is excellent.

  More specifically, when the relationship of Y ≦ 1.1 (0.48T-13.19) in the above-described formula (1) is not satisfied, the permanent distortion and the extrudability as the rubber composition are high. Extremely worse.

  On the other hand, when the polymer index Y of the copolymer (A) exceeds 25, permanent distortion and extrusion processability deteriorate, and conversely, when the polymer index Y is less than 20, hardness, stress and elongation deteriorate.

  Similarly, when the polymer index Y of the copolymer (B) exceeds 15, permanent set and extrudability are extremely deteriorated. Conversely, when the polymer index Y is less than 10, hardness, stress and elongation are deteriorated. become.

  Furthermore, if the blend ratio of the copolymer (A) is less than 1 wt%, sufficient hardness, stress and elongation as the rubber composition cannot be maintained, and conversely if it exceeds 40 wt%, the permanent strain will be deteriorated. .

  And as described in claim 2, the blend ratio of the copolymer (A) and the copolymer (B) is (A) / (B) = 1 to 35/99 to 65 (all numerical values are wt %), It is possible to obtain a high-quality rubber composition that can satisfy the required characteristics of hardness, stress, elongation, permanent set and extrudability.

  According to the first to third aspects of the invention, while achieving weight reduction, improving the extrudability such as discharge amount variation and shape retention during extrusion, along with the extrudability, permanent distortion, It becomes possible to satisfy all of the required characteristics for physical properties such as elongation, stress, and hardness.

  Further, according to the invention described in claim 4, it is possible to provide a lightweight weather strip which is excellent in extrusion processability and material physical properties.

  In Tables 1 to 4, samples A to W were actually extruded as examples and comparative examples as any one of the formulations 1 to 6 described later, and material properties and extrudability (extrusion moldability) The result of having been evaluated is shown.

  Here, samples A to M that satisfy the conditions of the present invention are used as examples, and samples N to W that do not satisfy the conditions of the present invention are used as comparative examples. Moreover, about sample S-1, S-2 which is an Example of Table 4, and U-1, U-2 and W-1, W-2 which are comparative examples, mixing | blending itself is sample S, U, and W. This is a case where only the temperature conditions immediately after extrusion are made different from each other, which will be described later.

  Basically, in any of the blends 1 to 6, an ethylene-propylene-5-ethylidene-2-norbornene copolymer (A) (hereinafter referred to as an ethylene-propylene-nonconjugated polyene copolymer (EPDM)) And EPDM (A)) and ethylene-propylene-5-ethylidene-2-norbornene copolymer (B) (hereinafter referred to as EPDM (B)) having specific properties shown in Tables 1 to 3 And a mixture of these EPDM (A) and EPDM (B) at the specific blend ratios shown in Tables 1 to 3, and carbon black, softener, foaming agent, inorganic vulcanization aid. An agent, a processing aid, an inorganic filler, a vulcanization accelerator, a vulcanization acceleration aid, a vulcanizing agent and the like are used.

  As the polyene copolymer of ethylene-propylene-nonconjugated polyene copolymer (EPDM) in each of the above formulations 1 to 6, 5-ethylidene-2-norbornene, gincopentadiene, 5-vinyl-2-norbornene, norbornadiene, In addition to cyclic non-conjugated polyenes such as methyltetrahydroindene, 1.4 hexadiene, 7-methyl-1.6-octadiene, 4-ethylidene-8-methyl-1.7-nonadiene, 4-ethylidene-1.7- As described above, it is possible to use a linear non-conjugated polyene such as undecadiene and 4.8-dimethyl-1.4.8-decatriene. These non-conjugated polyenes can be used alone or in combination of two or more.

  The structural unit (non-conjugated polyene content ratio) of the non-conjugated polyene is 1 to 20 wt%, preferably 1 to 15 wt%, more preferably 5 to 11 wt%.

  As the carbon black, for example, FEF, MAF, GPF, SRF, etc. can be used, and those alone or in a mixture of two or more can also be used preferably. The addition amount is about 80 to 190 phr.

  Softeners include process oil, paraffinic oil, lubricating oil, liquid paraffin, petroleum aspart, petroleum jelly and other petroleum softeners, coal tar, coal tar pitch and other coal tar softeners, castor oil, linseed Fatty oil-based softeners such as oil, rapeseed oil and coconut oil can be used. Desirably a petroleum softener, more desirably a paraffinic oil. The preferable addition amount in that case shall be 30-90 phr.

  Examples of the foaming agent include 4.4-oxybisbenzansulfonyl hydrazide (OBSH), azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), azobisisobutylnitrile (AZDN), azobisisobutyritol. In addition to foaming types such as (AIBN), paratoluenesulfonyl hydrazide (TSH), hydrazodicarbonamide (HDCA), and barium azocarboxylate, expansion types such as thermal expansion microcapsules containing low-boiling hydrocarbons are used. can do.

  Since the average foamed cell diameter of the rubber composition in the present invention is about 250 μm or less, preferably 200 μm or less, it is desirable to use a fine powder type foaming agent.

  The thermal expansion microcapsule described above has a microcapsule shell wall made of an acrylonitrile-based copolymer (foaming start temperature of 100 to 150 ° C.), and the low-boiling hydrocarbons encapsulated are isopentane, isobutane, and n-hexane. Etc. are used.

  This thermal expansion microcapsule has a particle diameter of 1 to 40 μm, and the expanded low boiling point hydrocarbon expands at the vulcanization temperature, so that the foam cell is controlled to about 30 to 150 μm by the shell wall. There is. A microcapsule in a more specific formulation example described later is Microsphere H770D manufactured by Dainichi Seika Kogyo Co., Ltd., but other than this, the same type of microcapsule can be used. The addition amount is 1 to 15 phr, preferably 3 to 10 phr.

  These foaming agents (including thermal expansion type) are used alone or in combination of two or more. Examples of two kinds of combinations include, for example, a combination of 4.4-oxybisbenzan sulfonyl hydrazide (OBSH) and thermal expansion microcapsules, or 4.4-oxybisbenzan sulfonyl hydrazide (OBSH) and azobizdiformamide. (ADCA).

  In addition, these foaming agents (including those of thermal expansion type) are used for elastomers, thermoplastic resins, softeners, inorganic fillers in order to prevent scattering or improve dispersibility when added to a rubber composition. It may be used after pre-blending with any one or more. In this case, the blending ratio of the foaming agent is 10 to 99 wt%, preferably 50 to 90 wt%.

  In addition, you may use a foaming adjuvant together with said foaming agent as needed. For example, urea derivatives, salicylic acid, phthalic acid, stearic acid and the like can be used as foaming aids.

  As the vulcanization acceleration aid, zinc oxide (zinc white), zinc carbonate, magnesium oxide, calcium hydroxide, zinc monoxide, or the like can be used, and zinc oxide or magnesium oxide is preferably used. If too much is added, bloom tends to occur, so the amount added is, for example, about 5 phr at most.

  As the inorganic filler, calcium carbonate, clay, silica, calcium silicate, magnesium carbonate, magnesium hydroxide, aluminum oxide, kaolin, mica, zeolite and the like can be used. In addition to using any of them alone, it is also possible to use a blend of two or more types. If the amount of the inorganic filler added is too large, the material specific gravity increases, so the amount added is about 0 to 100 phr, preferably 50 phr or less.

  Processing aids include compounds used in normal rubber processing, such as higher fatty acids such as stearic acid, ricinoleic acid, palmitic acid and lauric acid, salts of higher fatty acids such as calcium stearate, or ricinoleic acid, stearin Esters of higher fatty acids such as acid, palmitic acid and lauric acid can be used. The amount added is about 5 phr, preferably 3 phr or less.

  As the vulcanization accelerator, it is possible to use thiazole-based, thyrium-based, sulfenamide-based, guanidine-based, and thiourea-based dithiocarbamic acid-based ones. In addition to using any of them alone, it is also possible to use a blend of two or more types. If the addition amount is too small, the progress of vulcanization becomes slow, and if the addition amount is too large, bloom tends to occur and the appearance of the product deteriorates, so the addition amount is about 2 to 8 phr.

  As a vulcanizing agent, about 0.5 to 2 phr of general sulfur is added. When the addition amount is too small, the progress of vulcanization becomes slow, and when the addition amount is too large, bloom is likely to occur and the appearance appearance of the product is deteriorated.

  Moreover, it is also possible to mix | blend the component according to various objectives in the range which does not impair the intended objective as needed. The components according to various purposes include, for example, antioxidants, anti-aging agents, heat stabilizers, light stabilizers, UV absorbers, neutralizers, lubricants, anti-fogging agents, anti-blocking agents, slip agents, dispersants, Flame retardants, antistatic agents, conductivity-imparting agents, tackifiers, cross-linking agents, cross-linking aids, metal deactivators, molecular weight regulators, antibacterial / antifungal agents, fluorescent whitening agents, slidability improvers, Colorant such as titanium oxide, metal powder such as ferrite, inorganic fiber such as glass fiber and metal fiber, organic fiber such as carbon fiber and aramid fiber, composite fiber, glass balloon, glass flake, graphite, carbon nanotube, fullerene, sulfuric acid Barium, fluororesin, fillers such as polymer beads, polyolefin wax, cellulose powder, rubber powder, recycled rubber and the like.

(A) Formulation 1
-Polymer obtained by mixing EPDM (A) and EPDM (B) described above at blend ratios shown in Tables 1 to 3: 100 phr.

  Carbon black (Asahi # 50HG manufactured by Asahi Carbon Co.): 170 phr.

  Softener (Process oil P-300 manufactured by JOMO): 60 phr.

  Inorganic vulcanization aid (active zinc white): 1 phr.

  Processing aid (stearic acid): 1 phr.

  Processing aid (polyethylene glycol): 1 phr.

  Inorganic filler (calcium carbonate): 20 phr.

  ・ Vulcanization accelerator (thiuram, thiazole, sulfenamide, dithiocarbamine sun salt) 5 phr.

  -Vulcanizing agent (sulfur): 1 phr.

  In addition, about the foaming agent, any of the foaming agents 1-3 shown below was selectively used. The types of foaming agents used are as shown in Tables 1-3.

  -Foaming agent 1 (Neoselbon N # 1000M manufactured by Eiwa Kasei Kogyo Co., Ltd.): 1 phr.

  -Foaming agent 2 (Microsphere H770D manufactured by Dainichi Seika Kogyo Co., Ltd.): 4 phr.

  Foaming agent 3: The above neoselbon N # 1000M: 0.5 phr and the above Icro F Fair H770D: 2 phr in combination.

(B) Formulation 2
The amount of carbon black in formulation 1 was changed to 170 phr, and the amount of softening agent was changed to 45 phr (otherwise, the same as in formulation 1).

(C) Formula 3
The amount of carbon black in formulation 1 was changed to 170 phr, and the amount of softening agent was changed to 90 phr (otherwise, the same as in formulation 1).

(D) Formula 4
10 phr of low density polyethylene (Sumikasen G804 manufactured by Sumitomo Chemical Co., Ltd.) (described in Table 3) was added to 90 phr of EPDM (B) in Formulation 1 (otherwise, the same as Formulation 1).

(E) Formula 5
25 phr of low density polyethylene (Sumikasen G804 manufactured by Sumitomo Chemical Co., Ltd.) (described in Table 3) was added to 75 phr of EPDM (B) in Formulation 1 (otherwise, the same as Formulation 1).

(F) Formulation 6
The polymer in Formulation 1 was changed to PX049PE (Mitsui Chemicals) 108 phr (described in Table 3). At the same time, the softener (process oil P-300 manufactured by JOMO) was changed to 62 phr (otherwise it was the same as Formulation 1).

  The above-mentioned PX049PE is a blend obtained by microdispersing crystalline polyethylene 20 phr in a molten state in advance in oil-extended EPDM 110 phr (EPDM component: 100 phr).

  For sample preparation, the polymer is put into a closed mixer (in the case of Formulas 4 and 5, low-density polyethylene is also added) and then kneaded, and then each formulation excluding the vulcanization accelerator, vulcanizing agent and foaming agent The materials were charged, further kneaded and then discharged. The discharged compound was wound around a roll, blended by adding a vulcanization accelerator, a vulcanizing agent, and a foaming agent, and then dispensed into a ribbon shape. This was extruded with an extruder having a diameter of 75 mm, for example, after the extrusion conditions were set such that the temperature of the rubber composition immediately after extrusion was 50 to 150 ° C, preferably in the range of 80 to 130 ° C, for example 100 ° C.

  After the extrusion, vulcanization was performed in a continuous hot air vulcanizing tank under conditions of, for example, 150 to 280 ° C. × 1 to 60 minutes, more preferably 230 ° C. × 10 minutes.

  The extruded sample was prepared after adjusting the die shape and the screw rotation speed of the extruder so that the cross-sectional shape was 30 mm × 2 mm.

  In addition to sample S-1 as an example in Table 4, samples U-1 and W-1 as comparative examples are samples only in that the temperature of the rubber composition immediately after extrusion is adjusted to 115 ° C. It is different from S, U, and W. Similarly, in the sample U-2 and W-2 as comparative examples in addition to the sample S-2 as an example, the temperature of the rubber composition immediately after extrusion is 130 ° C. It differs from the samples S, U and W only in the point adjusted to.

  In addition to using various types of hermetic kneaders such as tangential type mixers, meshing type mixers, and kneaders, the above sample adjustment uses a kneading type twin screw extruder, open roll, or the like. Of course it is possible.

  Similarly, as the continuous vulcanization means, in addition to the above-described continuous hot air vulcanization tank (HAV), a high-frequency vulcanizer (UHF), a molten salt tank (LCM), a PCM (Powder Curing Method), etc. may be used. It is possible to use a combination of a continuous hot air vulcanizing tank and a high-frequency vulcanizer.

  In the columns of EPDM (A) and EPDM (B) in Tables 1 to 4, 1.1 (0.48T-13.3) is used as a criterion for determining whether or not the following formula (1) is satisfied. Along with the value of 19), the ethylene content ratio T (wt%) as the ethylene content and the value of the polymer structure index Y are shown. In the column of physical properties after cross-linking and foaming, the evaluation results of specific gravity, hardness (A), modulus (MPa), elongation (maximum elongation) (%) and permanent strain rate (%) are the extrudability (extrusion). In the column of formability, evaluation results of extrusion discharge amount variation (extrusion discharge amount variation rate) (%) and shape retention property (%) are shown.

Y ≦ 1.1 (0.48T-13.19) (1)
Y: Polymer structure index T: Ethylene weight ratio (wt%)
The ethylene weight ratio T in Tables 1 to 4 was calculated according to ASTM D-6047.

  On the other hand, since the polymer structure index Y is an index derived from the temperature dependence of the viscosity as described above, “RPA2000 manufactured by Alpha Technologies Co., Ltd.” is used as a viscoelasticity measuring machine under the following conditions. The complex viscosity η * (Pa · s) was measured.

Measurement conditions Temperature: 60 ° C-80 ° C-100 ° C
Frequency: 10.47 rad / s
Distortion rate: 6.98%
Then, the value obtained by the measurement was substituted into the following equation (2) to obtain X, and the value of X was substituted into equation (3) to obtain the polymer structure index Y.

η * = Aexp (X / R T _K ) (2)
Y = X / 1000 (3)
However,
η *: Complex viscosity (Pa · s)
Y: Polymer structure index
T _K : Temperature (K)
R: Gas constant (8.314 JK ⁻¹ mol ⁻¹ )
And

  Regarding the specific gravity in Tables 1 to 4, a test piece having a thickness t of 2 mm and a size of 20 × 20 mm was prepared from each sample, and the surface was wiped with alcohol to remove dirt. Thereafter, the specific gravity was calculated from the mass difference between air and pure water using an automatic hydrometer (manufactured by Toyo Seiki Seisakusho) in an atmosphere at 25 ° C. The automatic hydrometer is compliant with JIS K6220.

  The hardness (durometer A hardness), modulus, and elongation were determined in accordance with JIS K6253.

  Permanent distortion was determined by preparing a test piece of dumbbell No. 1 type (thickness t is 2 mm) as defined in JIS, and when stretched by 20% under heating conditions of 80 ° C. × 48 hours (after heating, left at room temperature for 3 hours) ) Was measured.

  Moreover, the extrusion discharge amount dispersion | variation (extrusion discharge amount variation rate (%)) of Tables 1-4 uses the screw | thread rotation speed of 20 rpm and the die which has the extrusion port 1a of a shape as shown in FIG. The weight variation of the discharge weight (number of samples n = 100) for 1 minute when each sample A to W was extruded using was calculated by the following formula (5).

Extrusion discharge amount variation rate (%) = {(maximum discharge amount (g) −minimum discharge amount (g)) / average discharge amount (g)} × 100 (5)
In addition, the dimension of each part of the extrusion shape in FIG. 1 is a = 6mm, b = 2mm, c = 11mm, d = 11mm, e = 3mm, f = 7mm, g = 7mm, h = 4mm.

On the other hand, for shape retention, sample A to W were used to prepare cylindrical test pieces (height 12.7 ± 0.13 mm, diameter 29.0 mm) each made of unvulcanized rubber, and the temperature was 100. Under an atmosphere of ° C., a load of 1 kg was applied to one end surface of the test piece over 5 minutes, and the height of the test piece h ₁ after the load release was measured. And the rate of change (%) in height calculated by the following formula (6) was defined as shape retention (%). Incidentally, h ₀ in Equation (6) shows a height of the test piece before applying a load.

Height change rate (%) = {(h ₀ −h ₁ ) / h ₀ } × 100 (6)
The target values in the right column in Tables 1 to 4 indicate target values that are functionally required when molding a so-called conventional solid rubber equivalent part in an automobile weather strip. In particular, the target value for permanent distortion (indicated as permanent distortion rate (%) in Tables 1 to 4) is 40 or less, but the above target value must be satisfied in order to maintain the function of the weather strip over a long period of time. is important.

  In addition, the variation in extrusion discharge amount (which is described as variation in extrusion discharge amount (%) in Tables 1 to 4) is set to 3% or less, but if it exceeds 3%, the cross section of the extruded product Variations in dimensions or in the longitudinal direction become remarkable, which is not preferable.

  Furthermore, for shape retention (%), the target value is 15% or less, but if it exceeds 15%, shape deformation immediately after extrusion becomes significant, and deformation in the vulcanization process, which is a subsequent process, is ignored. become unable.

  As is clear from Tables 1 to 4, the samples A to M as examples are of a predetermined relationship using the ethylene content ratio T and the polymer structure index Y as parameters, that is, Y ≦ 1.1 shown in the formula (1). Since the condition of (0.48T-13.19) is satisfied, the overall judgment is “OK”, which indicates that the material is extremely suitable as a material for an automobile weather strip. In other words, the samples A to M all have a specific gravity of 1.1 or less, and the weight reduction thereof is achieved. In addition, the samples have excellent permanent distortion rate and elongation, and are extrusion processable extruding amounts. It turns out that it is excellent also in terms of variation and shape retention.

  As apparent from Table 1, all of the samples A to M are those of Formulation 1 described above, and only one of the foaming agents 1 to 3 exemplified above is used properly.

  On the other hand, the sample N as a comparative example does not satisfy the relationship of Y ≦ 1.1 (0.48T-13.19), and in particular, in addition to the permanent distortion rate, the extrusion discharge amount variation and shape retention which are extrusion processability The evaluation numerical value regarding the property is inferior to the samples A to M, and the overall judgment is “NG”. This is presumed that the chemical structure of EPDM is not appropriate and the block copolymerization of the ethylene component in the polymer chain is high. Therefore, since the crystallization component of ethylene in the molecule becomes too large, it is predicted that the permanent distortion rate and the extrudability deteriorate significantly.

  In addition, the sample O which is a comparative example does not satisfy the relationship of Y ≦ 1.1 (0.48T-13.19), and P satisfies the condition of the polymer structure index Y itself by the blended EPDM (B). Since the permanent distortion rate and the extrusion processability are thereby deteriorated, the comprehensive judgment is “NG”. This is because, when the polymer structure index Y of EPDM (A) or EPDM (B) is too large, an EPDM component having high temperature dependence of viscosity, that is, an ethylene-propylene-5-ethylidene-2-norbornene copolymer is mixed. This is probably because the fluidity of the compound in the extruder is not stable.

  Sample R, which is also a comparative example, is not blended with EPDM (A), as is clear from Table 2, and therefore the hardness and elongation, which are physical properties, are extremely deteriorated, and the overall judgment is “NG”. It has become.

  Sample S, which is a comparative example, is of type 2 as shown in Table 3, and the amount of softener added is significantly reduced compared to that of formula 1 as described above. I'm allowed. In this sample S, since the elongation and the extrusion discharge amount variation are particularly deteriorated, the comprehensive judgment is “NG”. This is presumably because when the unvulcanized compound is extruded, a so-called slip stick phenomenon occurs on the wall surface inside the extruder, and the extrusion discharge amount is not stable.

  However, if only focusing on improving the extrusion discharge amount for this sample S, the temperature of the rubber composition immediately after extrusion is set higher as shown in Samples S-1 and S-2 in Table 4 above. The slip stick phenomenon as described above is suppressed, and the variation in extrusion discharge amount is improved. Sample S-1 and sample S-2 will be described later.

  Samples U and V, which are comparative examples in Table 3, are cases where crystalline polyethylene is added on the premise of Formulation 3 or Formulation 4, as in the case of the prior art and exemplified. As is apparent from Table 3, the variation in the extrusion discharge amount is also worsened along with the extreme deterioration of the permanent distortion rate, and as a result, the overall judgment is “NG”. The above-mentioned crystalline polyethylene has been added as a component to improve the hardness and elongation of rubber compositions based on the premise of weight reduction, but is added so as to satisfy required properties such as hardness, stress, and elongation. When the amount is adjusted, the result is that the permanent distortion rate and extrusion processability are extremely deteriorated, the productivity is low for use as a material for an automobile weather strip, and the product performance over a long period cannot be maintained. It turns out that it is unsuitable as a means for achieving both physical properties and extrusion processability while achieving weight reduction.

  Sample W in Table 3 is based on Formulation Example 6 described above, and is an example in which a blended product in which crystalline polyethylene is microdispersed in a molten state in advance in an EPDM component is blended. As is apparent from Table 3, in addition to the extreme deterioration of the permanent set rate, it can be seen that the extrusion discharge amount variation and the shape retention, which are extrusion processability, are extremely deteriorated.

  Table 4 shows the case where only the samples S, U, and W, which are comparative examples, are extracted from Table 3, and only the temperature conditions immediately after the extrusion are changed for the samples S, U, and W. The evaluation results of Examples S-1 and S-2 and Comparative Examples U-1, U-2 and W1-1, W1-2 are shown.

  That is, Samples S, U, and W are cases where the temperature immediately after extrusion is set to 100 ° C. as in the other Examples and Comparative Examples in Tables 1 to 3, whereas Example S in Table 4 is used. -1 and Comparative Examples U-1 and W-1 are cases where the temperature immediately after extrusion was set to 115 ° C, respectively. Similarly, Example S-2 and Comparative Examples U-2 and W-2 were temperatures immediately after extrusion. Are set at 130 ° C., and other conditions are not different from those of the samples S, U, and W.

  As described above, the sample S is a remarkable example in which the variation in the extrusion discharge amount is extremely deteriorated. However, if only focusing on improving the extrusion discharge amount with respect to this sample S, the embodiment of Table 4 will be described. As shown in Samples S-1 and S-2, by setting or adjusting the temperature of the rubber composition immediately after extrusion to a higher value, the sample S suppresses a significant slip stick phenomenon and improves extrusion discharge variation. At the same time, the hardness is remarkably good like the sample S. That is, as described above, the sample S which is a comparative example is a case where the temperature immediately after extrusion is set to 100 ° C., whereas the samples S-1 and S-2 which are examples are immediately after extrusion. Table 4 is different from Sample S only in that the temperature of each is set to 115 ° C. and 130 ° C., and the comprehensive judgment is as shown in Table 4 with the main aim of achieving both physical properties excluding elongation and extrudability. “OK”. As a result, this indicates that the evaluation of physical properties and extrudability in the present invention using the polymer structure index Y that depends on temperature as a parameter is appropriate.

  On the other hand, as is clear from Table 4, with respect to Comparative Examples U-1, U-2 and W-1, W-2, the shape retainability is extremely deteriorated as the temperature immediately after extrusion is increased. I understand.

  FIGS. 2 to 5 show specific examples of weather strips for automobiles suitable for molding using the rubber compositions of Examples S-1 and S-2 in addition to Examples A to M described above. ing.

  FIG. 2 shows an example of a so-called door glass run 3 to be fitted and held in the door sash portion 2. The glass run main body 4 having a substantially cross-sectional shape and a door projecting from the inner periphery of the glass run main body 4. A plurality of lips 5 and 6 that are in elastic contact with the glass G are integrally formed, and each of the rubber compositions described in Examples S-1 and S1-2 is extruded in addition to Examples A to M. Has been.

  FIG. 3 shows an example of a weatherstrip for a trunk lid. The weatherstrip 7 itself generally includes a cored bar 8 and has a substantially U-shaped cross section, and has a trunk room (luggage room) opening edge. It comprises a welt part 9 fitted and held in the flange part F, and a hollow seal lip 10 integral with the welt part 9, and the trunk lid 11 elastically contacts the seal lip 10 when the trunk lid is closed. . Since the seal lip 10 is formed of so-called sponge rubber, only the welt part 9 is sealed with any of the rubber compositions described in Examples S-1 and S1-2 in addition to Examples A to M. It will be co-extruded with the lip 10.

  FIG. 4 shows an example of a so-called welt body side. Like the above-described weather strip 7 for a trunk lid, the welt body side 12 itself generally includes a metal core 13 and has a substantially U-shaped cross section. And a hollow seal lip 15 integral with the welt part 14. Since the seal lip 15 is formed of so-called sponge rubber, only the welt part 14 is sealed with any of the rubber compositions described in Examples S-1 and S1-2 in addition to Examples A to M. It will be co-extruded with the lip 15.

  Further, FIG. 5 shows what is called a hood seal. This hood seal 16 is attached to the back of the front end of a rear hinge type hood (bonnet) 17 with a clip 18 or the like, and the headlamp unit is closed when the hood is closed. It serves to close the gap between the two by being in elastic contact with 19. Since the hood seal 16 has a uniform cross-sectional shape in the longitudinal direction, the hood seal 16 is extruded with any of the rubber compositions described in Examples S-1 and S1-2 in addition to Examples A to M. Will be.

  The weather strips shown in FIGS. 2 to 5 are merely examples, and it is of course possible to mold a weather strip having other equivalent functions with the rubber composition of the present invention.

Explanatory drawing which shows the extrusion port shape of a nozzle | cap | die used when evaluating the extrusion discharge amount dispersion | variation which is one of the extrusion processability of the rubber composition of this invention. It is a figure which shows an example of the weather strip for motor vehicles which uses the rubber composition of this invention as a raw material, and is sectional explanatory drawing of a door glass run. It is a figure which shows an example of the weather strip for motor vehicles which uses the rubber composition of this invention as a raw material, and is sectional explanatory drawing of the weather strip for trunk lids. It is a figure which shows an example of the weather strip for motor vehicles which uses the rubber composition of this invention as a raw material, and is sectional explanatory drawing of a welt body side. It is a figure which shows an example of the weather strip for motor vehicles made from the rubber composition of this invention, and is sectional explanatory drawing of a hood seal.

Claims (4)

The ethylene-propylene-nonconjugated polyene copolymer satisfies the relationship of the following formula (1) when the polymer structure index is Y and the ethylene content is T (wt%).
Y ≦ 1.1 (0.48T-13.19) (1)
An ethylene-propylene-nonconjugated polyene copolymer (A) with Y = 20-25 and an ethylene-propylene-nonconjugated polyene copolymer (B) with Y = 10-15 are (A) / (B) = 1. A rubber composition having a hardness of 55 (A) or more obtained by foaming and crosslinking an uncrosslinked rubber composition blended at a ratio of ˜40 / 99 to 60 (all numerical values are wt%).   The blend ratio of the ethylene-propylene-nonconjugated polyene copolymer (A) and the ethylene-propylene-nonconjugated polyene copolymer (B) is (A) / (B) = 1-35 / 99-65 The rubber composition according to claim 1, wherein the rubber composition is also wt%.   The rubber composition according to claim 1, wherein the specific gravity is 1.1 or less.   An automotive weather strip made of the rubber composition according to claim 1.

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