JP2001270957A - Rubber composition for sponge and sponge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a sponge having good sealing performances well balanced with processability, and to provide the sponge manufactured from it having good processability. SOLUTION: The rubber composition for a sponge comprises 100 pts.wt. of an ethylene/α-olefin/diolefin copolymer satisfying conditions below and a softening agent in the ratio of 80-200 pts.wt. based on the copolymer. The sponge is manufactured from the composition having a Money viscosity in a specified range and has a specific gravity having a specific relation with it 100% modulus. An intrinsic viscosity [η] measured in a decalin solvent at 135 deg.C is within the range of 2.8-5.2 dl/g. The weight ratio of the ethylene component to the α-olefin component (ethylene/α-olefin) is within the range of 75/25 to 50/50. The content of the diolefin component is within the range of 10-50 in iodine value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a sponge which provides a sponge having excellent sealing performance and has excellent processability, and a sponge produced from the composition having excellent sealing performance.

[0002]

2. Description of the Related Art Most of sponges used for automobiles and construction use ethylene-α-olefin copolymer rubber having excellent performance in heat resistance, weather resistance, workability and cost. Particularly, as a material indispensable for door seals, trunk seals, and wind seals for automobiles, its penetration rate is remarkable.

However, as the performance of automobiles has become higher, the sealing performance required for these sponges has also been improved, and it is difficult for conventional technologies to sufficiently satisfy all the advanced performance requirements. It has become In other words, engine noise during high-speed driving of the car, wind noise around the door,
Problems such as tire squeaking noise and the like leaking into the room and rain leaking largely depend on the sealing performance around the door, and the demand for the sealing performance on the sponge has become more severe. When the door is closed, the door seal sponge is used as a sealing material between the door and the body while being compressed for a long period of time. As a means for quantifying the compression set, a compression set can be used, and a seal sponge having a small value is required.

On the other hand, as the speed of an automobile increases, the vibration frequency of the door also increases. Therefore, it is desirable that the seal sponge sufficiently follows the vibration of the door. If the sponge for sealing does not follow the vibration of the door poorly, a space is created between the door and the body, so that the above-described various noises leak into the room. A hysteresis loss is generally used as a means for grasping the following performance, and a sponge with a small hysteresis loss is required. Further, it is important that the door is opened and closed smoothly even in a wide temperature range from high temperature to low temperature. Therefore, the sponge needs to maintain sufficient softness in a wide temperature range.

[0005] In addition to the performance required of the sponge described above, the rubber composition for producing a sponge is required to have sufficiently excellent processing characteristics such as kneading processability, extrusion processability, and shape retention.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a sponge in which the obtained sponge has a high level of sealing performance and workability. Another object of the present invention is to provide a sponge which has no problem in workability in a manufacturing process and has excellent sealing performance.

According to the present invention, a rubber composition for sponge and a sponge having the following constitutions are provided, and the above object of the present invention is achieved. 1. An ethylene-α-olefin-diolefin copolymer rubber and a softener satisfying the following (a) to (c) are contained at a weight ratio of 80 to 200 parts by weight of the softener to 100 parts by weight of the copolymer rubber. A rubber composition for a sponge, comprising: (A) The intrinsic viscosity [η] measured at 135 ° C. in a decalin solvent is in the range of 2.8 to 5.2 dl / g. (B) The weight ratio between the ethylene component and the α-olefin component (ethylene / α-olefin) is in the range of 75/25 to 50/50. (C) The content of the diolefin component is 10 to 5 in terms of iodine value.
Be in the range of 0. 2. Carbon black was added in an amount of 0.1 parts by weight per 1 part by weight of the softener.
2. The sponge rubber composition as described in 1 above, which is contained in a weight ratio of 2 to 1.0 part by weight. 3. Mooney viscosity (ML1 + 4, 125 ° C) 20-50
Wherein the specific gravity (X) of the sponge is in the range of 0.4 to 0.9 and the 100% modulus (Y ) Is in the range of 0.2 to 1 MPa / m ² , and the 100% modulus (Y) satisfies the following formula (1).

[0008]

## EQU00002 ## 1.59X-0.75≤Y≤1.59X-0.2 Equation (1)

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The ethylene-α-olefin-diene copolymer rubber (hereinafter, also simply referred to as “copolymer rubber”) contained in the rubber composition for a sponge of the present invention (hereinafter, also simply referred to as “rubber composition”) has the following conditions (a). Satisfies (c) to (c). (A) The intrinsic viscosity [η] measured at 135 ° C. in a decalin solvent is 2.8 to 5.2 dl / g, preferably 3.5 to 5.2 dl / g.
Must be in the range of 4.5 dl / g. (B) the weight ratio of ethylene component to α-olefin component (ethylene / α-olefin) is 75/25 to 50/50,
Preferably, it is in the range of 65/35 to 55/45. (C) The content of the diolefin component is 10 to 5 in terms of iodine value.
0, preferably in the range of 20-40.

The above condition (a) means that a high molecular weight copolymer rubber is used. In the present invention, the balance of processability, sponge flexibility and sponge sealing properties is maintained at a high level by using such a high molecular weight copolymer rubber and blending a specific amount of a softener. When [η] is less than 2.8 dl / g, when a large amount of a softening agent is added to impart flexibility, the rubber composition of the present invention tends to relax the stress, and the shape can be reduced in a short time after processing into a predetermined shape. Changing machining problems are likely to occur. Also,
If [η] exceeds 5.2 dl / g and becomes too high in molecular weight, the extruded product tends to shrink more, the surface is wavy, and the appearance of the sponge is deteriorated.

By satisfying the range of the weight ratio between the ethylene component and the α-olefin component under the above condition (b), the rubber composition and the low-temperature properties of the rubber composition become appropriate.
The weight ratio of the ethylene component to the α-olefin component is 75/2
If it exceeds 5, the compression set of the sponge rubber at low temperature is deteriorated, the recoverability of the sponge rubber is extremely poor, and the sponge rubber is unsuitable as a sealing material. The weight ratio is 50/50
If the amount is less than the above range, problems such as a decrease in productivity of the copolymer rubber and an increase in cost occur.

The above condition (c) is a measure of the content of the diolefin component. If the iodine value is less than 10, crosslinking becomes insufficient and the compression set of the sponge rubber deteriorates. When the iodine value exceeds 50, gelation tends to occur at the time of kneading, and troubles such as occurrence of bumps in the extrusion step are likely to occur.

The α-olefin to be copolymerized with ethylene is preferably an α-olefin having 3 to 8 carbon atoms, and specifically, propylene, 1-hexene, 1-butene, 1-
Hexene, 1-pentene, 1-octene, 1-decene and the like. The α-olefin can be used alone or in combination of two or more. Non-conjugated dienes are preferred as conjugated dienes, and specific examples include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene, ethylidene norbornene, 7-methyl-1,6-octadiene, and the like. It is also possible to give a branched structure to the ethylene-based random copolymer by a known method. Preferred examples of the diene for imparting a branched structure include 1,9-decadiene and norbornadiene. One or two or more of these non-conjugated dienes may be used.

As the softening agent to be added to the rubber composition of the present invention, a softening agent usually used for rubber is used. Specifically, process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petrolatum, coal tar pitch, castor oil, linseed oil, sub, beeswax, ricinoleic acid, palmitic acid, barium stearate, calcium stearate, laurin Examples include zinc acid, atactic polypropylene, and coumarone indene resin. Among them, process oil is preferably used. These softeners are used in an amount of 80 to 200 parts by weight, preferably 100 to 150 parts by weight, based on 100 parts by weight of the copolymer rubber. By using the softener in the above range, a sponge rubber excellent in sealing performance can be obtained without impairing workability such as operability and shape retention during kneading.

The rubber composition for a sponge of the present invention is appropriately compounded with various compounding agents such as a filler, a foaming agent, a vulcanizing agent, a vulcanization accelerator and a vulcanization aid.

The filler which can be used in the present invention includes carbon black, finely divided silica, glass powder, glass beads, mica, calcium carbonate, potassium titanate whisker, talc, clay, barium sulfate, glass flake, fluorine Resins and the like can be mentioned. Among them, carbon black is preferably used in terms of improving the strength of the sponge and reducing the cost of the sponge. Carbon black includes SRF, GPF, FEF, HAF, I
There are types such as SAF, SAF, FT, and MT, and any of them can be used. Among them, SRF, FEF, G
The use of PF is preferred. As for the amount of carbon black to be added, it is preferable from the viewpoint of imparting flexibility that the amount of carbon black to be added is in the range of 0.2 to 1, particularly 0.4 to 0.9, relative to the amount of the softener.

The vulcanizing agent blended in the rubber composition of the present invention is sulfur; sulfur compounds such as sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, and selenium dimethyldithiocarbamate. Dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-
Organic peroxides such as 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, di-tert-butyl peroxide, di-tert-butyloxy-3,3,5-trimethylcyclohexane, and tert-butyl hydroperoxide Oxides and the like can be mentioned. Of these, sulfur, dicumyl peroxide, ditertiary butyl peroxide, ditertiary butylperoxy-3,3,5-trimethylcyclohexane are preferred.

The sulfur or sulfur-based compound is generally used in a proportion of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the copolymer rubber. The organic peroxide is usually used in an amount of 0.1 to 100 parts by weight of the copolymer.
To 15 parts by weight, preferably 0.5 to 8 parts by weight. When sulfur or a sulfur-based compound is used as a vulcanizing agent, a vulcanization accelerator and a vulcanization aid are used in combination, if necessary.

Examples of the vulcanization accelerator include N-cyclohexyl-2-benzothiazole-sulfenamide, N-oxydiethylene-2-benzothiazole-sulfenamide, N, N-diisopropyl-2-benzothiazolesulfenamide, 2-mercapto Benzothiazole, 2
-(2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole, dibenzothiazyl-disulphide; diphenylguanidine, triphenylguanidine,
Diorthotolylguanidine, orthotolylbiguanide, diphenylguanidine phthalate; acetaldehyde-aniline reactant, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde ammonia; 2-mercaptoimidazoline; thiocarbanilide, diethylthiourea, dibutylthiourea , Trimethylthiourea, diortho tolyl thiourea; tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulphide, tetrabutylthiuram disulfide, pentamethylenethiuram tetrasulfide, zinc dimethyldithiocarbamate,
Zinc diethylthiocarbamate, zinc di-n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate;
Zinc dibutylxanthogenate and the like can be mentioned. These vulcanization accelerators are usually 0.1 to 20 parts by weight, preferably 0.2 to 1 part by weight, based on 100 parts by weight of the copolymer rubber.
Used in a proportion of 0 parts by weight.

Examples of the vulcanization aid include metal oxides such as magnesium oxide and zinc white, and the use of zinc white is preferred. These vulcanization aids are copolymer 100
It is usually used in an amount of 3 to 20 parts by weight with respect to parts by weight.

When vulcanizing with a peroxide, quinone dioximes such as sulfur and P-quinone dioxime,
Crosslinking aids such as polyethylene glycol dimethacrylate, diallyl phthalate, triallyl cyanurate, and divinylbenzene may be used.

The foaming agent to be blended in the rubber composition of the present invention includes sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite,
N, N′-dimethyl N, N′-dinitrone terephthalamide, N, N′-dinitrone pentamethylenetetramine,
Azodicarbonamide, azobisisobutyronitrile,
Azocyclohexylnitrile, azodiaminonenezen,
Barium azodicarboxylate, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, P, P'-
Oxybis (benzenesulfonyl hydrazide), diphenylsulfone-3,3'-disulfonylhydrazide, calcium azide, 4,4'-diphenyldisulfonyl azide, valatoluene malonyl azide can be mentioned. The foaming agent is used in an amount of 0.5 to 100 parts by weight of the copolymer rubber.
-30 parts by weight, preferably 1-15 parts by weight. If necessary, a foaming aid may be used in combination with a foaming agent.

As the rubber component of the rubber composition for sponge, other types of rubber or other ethylene-α-olefin-diolefin copolymer may be used together with the above-mentioned copolymer rubber within a range not to impair the achievement of the object of the present invention. It does not matter even if polymer rubber is mixed and used.

The rubber composition of the present invention can be prepared by kneading the components using a conventionally known kneader. That is, the above-mentioned components are added to the copolymer rubber, and the mixture is kneaded using an open roll mill, a Banbury mixer, a kneader, or the like to obtain a sponge rubber composition of the present invention.

The rubber composition for a sponge of the present invention is preferably prepared so that the Mooney viscosity (ML1 + 4, 125 ° C.) is in the range of 20 to 50.

Thereafter, the sponge is formed by molding the rubber composition for sponge into a desired shape using an extruder or a mold, and then vulcanizing and foaming with a heating device such as a high-frequency heating device, an air oven, PCM, or LCM. it can. Alternatively, a sponge may be produced by a method of molding and vulcanizing and foaming in a mold using a vulcanizing and foaming apparatus known per se.

The rubber composition for a sponge of the present invention can perform the above-mentioned kneading process smoothly, and can be prepared as a uniform composition. Also, the molding process can be performed without any problem. Since the rubber composition of the present invention hardly relieves stress, the molded product is not substantially deformed in a short time or deformed by its own weight during vulcanization and foaming by heating. Thus, the rubber composition for a sponge of the present invention is excellent in processability.

The specific gravity (X) of the sponge of the present invention is appropriately selected according to its use, but is preferably 0.4 to 0.5.
9 Further, the tensile modulus (Y) of the sponge of the present invention is preferably 0.2 to 1 MPa / m ² . When the tensile modulus is within the above range, when used as an automobile door seal material, the door can be closed with a small force because the impact when opening and closing the door is small and the reaction force is small. In particular, a sponge produced from the rubber composition of the present invention, in which the specific gravity (X) and the tensile modulus (Y) of the sponge satisfy the above-mentioned formula (1), are sponges produced with good processability, and furthermore, have a seam. Excellent in properties.

The sponge of the present invention described above is used as a door seal material, a trunk seal material, a wind seal material, a bonnet seal material, and also a building material-related seal material for automobiles.

[0030]

EXAMPLES The present invention will be described below in detail with reference to examples, but the scope of the present invention is not limited by the examples. Examples A to F and Comparative Examples GI The samples in the examples were prepared by the following methods. Table 2 using a lab size Banbury mixer (internal volume 1.7 L)
The ethylene-propylene-ethylidene norbornene copolymer rubber (EPDM), carbon black, and a softener were added in predetermined amounts to calcium carbonate 2
0 parts by weight, 5 parts by weight of zinc white, 1 part by weight of stearic acid, and 1 part by weight of an activator were added to a rubber composition A, and a predetermined amount of a vulcanization accelerator described in Table 2 was added. 0.5 parts by weight of phosphorus sulfide, 1 part by weight of sulfur, 4 parts by weight of a foaming agent, and 3 parts by weight of a hygroscopic agent were added and kneaded with a 10-inch open roll to prepare a rubber composition B. Next, the above rubber composition B was extruded into a tube by a 40 mm extruder (tubular die, wall thickness: 1.4 mm, die temperature: 80 ° C., cylinder temperature: 60 to 70 ° C.).
The mixture was vulcanized and foamed in a 20 ° C. HAV tank for about 5 minutes to obtain a tubular sponge rubber.

The specific gravity of the sponge rubber was determined by calculating the volume from the weight of the sample cut into 15 mm in air and the buoyancy when immersed in water, and dividing the weight by the volume. Regarding the modulus as an index of softness, a tube-shaped sponge sample was cut open in the longitudinal direction to form a sheet, and punched out with a JIS-2 dumbbell to obtain a test piece. Since the stress relaxation is used as an index of shape retention before vulcanization, the rubber composition A after discharging the Hanbury mixer is heated to 140 ° C. using a 70 × 50 × 6 mm mold.
, And then cooled and molded. In the test, a molded product punched with a 12 mm rotary blade was used as a test piece.

Each compound used in the compounding formula is as follows. EPDM See Table 1. Carbon black Asahi Carbon Asahi 50HG Softener Idemitsu Kosan Diana Process Oil PW-380 Calcium Carbonate Shiroishi Kogyo Bigot-15 Zinc Hua Shodo Chemical Co., Ltd. Active Zinhua Azo Stearic Acid Kao Lunarc S-30 Activity Agent PEG # 4000 Vulcanization Accelerator MBT Ouchi Chemical Noxeller M Vulcanization Accelerator CMBT Ouchi Chemical Noxeller M-60-OT Vulcanization Accelerator ZnMDC Ouchi Chemical Noxeller PZ Vulcanization Accelerator ZnBDC Ouchi Chemical Noxeller EZ Vulcanization Accelerator ZnEDC Ouchi Chemical Type Noxeller BZ Vulcanization Accelerator DPTT Ouchi Chemical Noxeller TRA Vulcanization Accelerator TETD Ouchi Chemical Noxeller TET Morpholine Disulfide Ouchi Chemical Barnock R Sulfur Powder Sulfur Foaming Agent Neocellon made by Eiwa Kasei 1000SW moisture absorbent Inoue lime made Vesta PP

Various measurements in the examples are performed by the following methods.
The results are shown in Table 3. <Characteristics of unvulcanized copolymer rubber> (1) Stress relaxation test A constant load was applied to the rubber composition A, and the relaxation rate of the unvulcanized copolymer rubber was measured by a stress retention after n seconds with respect to the initial stress. However, it was used as an index of the superiority of the shape retention. Specifically, a constant strain (20% compression) is applied to the unvulcanized rubber sample at 100 ° C., and the initial stress is F (0), the stress after 1 second, the stress after 10 seconds, and the stress after 100 seconds. The stress of each is F
(N). The stress retention is represented by the following equation. Stress retention after n seconds Rτ = F (n) / F (0) Table 3 shows the stress retention after 10 seconds. <Characteristics of compounded rubber compound> (2) Mooney viscosity (ML1 + 4,
(125 ° C.) It was measured according to JIS K6301.

<Vulcanized Rubber Properties> (4) Sponge vulcanized rubber elongation stress (100% modulus) Test temperature 1 ... R. T. (23 ± 2 ° C) Specimen shape: JIS-2 Tensile speed: 200 mm / min, (5) Sponge compression set test The outer diameter of a tube-shaped sponge sample was measured, and the sample height (h) was defined as the following formula. Adjust the spacer based on. hh × 0.5 = 50% spacer height (s) The test method conforms to the compression set test of JIS K6301 solid rubber. Test temperature: 70 ° C Test time: 200 hrs Compressibility: 50% Test piece shape: Tube with base

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

Examples A to F were prepared by adjusting the Mooney viscosity of a rubber composition for a sponge to an area which would be good in a general rubber processing step by using an ethylene copolymer rubber within the scope of the present invention. is there. On the other hand, Comparative Examples G to I were prepared using an ethylene copolymer rubber having a viscosity lower than the viscosity range of the present invention and adjusted to a viscosity range equivalent to that of the examples. Among these, the comparison between Examples B and F and Comparative Examples G and I, and the comparison between Example C and Comparative Example H are comparisons in which the viscosity of the rubber composition for sponge was adjusted to be equal. In each of the examples, the stress relaxation retention ratio is higher than that of the comparative example having the same viscosity, and the shape retention is excellent. Basically, the examples have lower elongation stress than the comparative examples and are soft. Conversely, when a large amount of a softening agent was added to adjust the comparative example to have the same modulus as that of the example, the viscosity was significantly reduced, the stress relaxation retention ratio was further deteriorated, and the shape was reduced from molding to vulcanization. There is a risk of processing troubles such as deformation of Further, a copolymer having a viscosity exceeding the viscosity range of the present invention and having an excessively high molecular weight has a large degree of shrinkage of an extruded product, and causes deterioration of surface texture. From these comparisons, it can be seen that the rubber composition using the ethylene copolymer rubber within the scope of the present invention maintains shape retention in the viscosity region considered to be good in the processing step, and has a soft (low modulus) sponge. ) Can be given.

[0039]

According to the present invention, a sponge having good processability and excellent sealing performance can be obtained from the rubber composition for a sponge of the present invention in which a high molecular weight ethylene-α-olefin-diolefin copolymer rubber is combined with a specific amount of a softener. Can be. Also,
The present invention is manufactured from a rubber composition for a sponge having a Mooney viscosity (ML1 + 4, 125 ° C) in the range of 20 to 50, and the specific gravity (X) and the tensile modulus (Y) of the sponge satisfy the above formula (1). The sponge has no problem in workability in the manufacturing process and has excellent sealing performance.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hidetoshi Goto 2-11-24 Tsukiji, Chuo-ku, Tokyo FSR term in JSR Corporation 4F074 AA25 AC02 AG02 BA02 BA03 BA04 BA05 BA13 BA14 BA16 BA18 BB01 BB05 CA21 CC22X CC22Y DA02 DA35 4J002 AE03X AE05X AG00X BA01X BB05W BB13X BB15W BK00X DA037 EA016 EF056 EG046 FD017 FD02X FD026 FD140 FD150 FD320 GL00 GN00 4J100 AA16A11 AAQA AQA ARQA AQA AAQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQA AQ

Claims (3)

[Claims] 1. An ethylene resin satisfying the following (a) to (c):
α-olefin-diolefin copolymer rubber and a softener, the softener 80 to 100 parts by weight of the copolymer rubber,
A rubber composition for a sponge, comprising 200 parts by weight. (A) The intrinsic viscosity [η] measured at 135 ° C. in a decalin solvent is in the range of 2.8 to 5.2 dl / g. (B) The weight ratio between the ethylene component and the α-olefin component (ethylene / α-olefin) is in the range of 75/25 to 50/50. (C) The content of the diolefin component is 10 to 5 in terms of iodine value.
Be in the range of 0. 2. The sponge rubber composition according to claim 1, wherein the carbon black is contained in an amount of 0.2 to 1.0 part by weight based on 1 part by weight of the softening agent. . 3. A sponge having a Mooney viscosity (ML1 + 4, 125 ° C.) in the range of 20 to 50, obtained by vulcanizing and foaming the rubber composition for sponge according to claim 1 or 2, and the specific gravity of the sponge. (X) is in the range of 0.4 to 0.9, and 100
A sponge having a% modulus (Y) in the range of 0.2 to 1 MPa / m ² and a 100% modulus (Y) satisfying the following expression (1). 1.59X−0.75 ≦ Y ≦ 1.59X−0.2 Equation (1)