JP2001106847A - Ep rubber based composition and its foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an EP rubber based composition capable of giving an EP rubber based foam at a high expansion ratio (low density) which exhibits high sealing performance by good cushioning properties, compressive properties, and the like, which an ethylene/propylene based rubber foam possesses and having no tacky surface and excellent surface smoothness with a good production efficiency because of no need to provide dusting powder and with an excellent degree of freedom in its producible shape, and an EP rubber based foam obtained therefrom. SOLUTION: This EP rubber based composition comprises an admixture having at least an ethylene/propylene based rubber, an organic peroxide, azodicarbonamide, and 5-200 wt.%, based on the azodicarbonamide, borax as the components. An EP rubber based foam is composed of a vulcanized foam of the composition and has a density of 0.05-0.6 g/cm3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention efficiently forms an EP rubber foam which can be crosslinked and foamed without surface stickiness and has good surface smoothness and is suitable as a sealing material for various purposes against liquids, gases and sounds. Compositions that can be used.

[0002]

2. Description of the Related Art Heretofore, as an EP rubber-based foam, a foam obtained by subjecting an ethylene / propylene rubber to a crosslinking and foaming treatment with an organic peroxide and azodicarbonamide has been known. Such foams are based on their excellent light weight, flexibility, cushioning properties, compressibility, etc., and are used as cushioning materials and pad materials, sealing materials such as airtightness and water stoppage, heat insulation materials, soundproofing materials, etc. It is used in various fields such as outdoor articles such as automobiles and buildings such as houses.

However, in the case of the conventional EP rubber foam, stickiness (adhesion) is generated due to inhibition of cross-linking of the surface layer by oxygen during the cross-linking and foaming treatment, and the surface is roughened. After performing cross-linking and foaming treatment in a state where the powder is applied to the surface by a method such as the above method, it is necessary to wash and remove the powder, resulting in poor production efficiency.

[0004]

The present invention relates to a composition capable of obtaining an EP rubber-based foam having no stickiness on its surface and excellent in surface smoothness by performing a cross-linking and foaming treatment without the need for prior powdering. Development is an issue.

[0005]

The present invention relates to an ethylene-propylene rubber, an organic peroxide, an azodicarbonamide, and an admixture containing at least 5-200% by weight of borax based on the azodicarbonamide. An EP rubber-based composition characterized by comprising a vulcanized foam of the composition and a density of 0.05 to 0.6 g / cm ^3. .

[0006]

According to the present invention, it is possible to perform cross-linking and foaming treatment with good surface smoothness and low surface tackiness while reducing the decomposition temperature of azodicarbonamide with borax, and the ethylene-propylene-based rubber foam is excellent. An EP rubber foam having a high foaming ratio (low density) exhibiting high sealing performance due to cushioning property, compressibility and the like can be obtained. Therefore, it is possible to avoid the necessity of applying the powder before the heat foaming treatment and washing and removing the powder after the treatment, thereby obtaining a high-quality EP rubber-based foam with high production efficiency. It can be molded into a mold and subjected to a cross-linking and foaming treatment, so that the degree of freedom of the shape of the foam that can be produced is excellent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The EP rubber composition according to the present invention comprises
5 to ethylene-propylene rubber, organic peroxide, azodicarbonamide and the azodicarbonamide
The EP rubber foam comprises a vulcanized foam having a density of 0.05 to 0.6 g / cm ³ obtained by vulcanizing and foaming the composition.

As the ethylene / propylene rubber, one or more suitable rubbers such as ethylene / propylene / diene rubber (EPDM), ethylene / propylene rubber, and ethylene / propylene terpolymer can be used. There is no. EPDM, especially those having a Mooney viscosity of 5 to 100 (ML _{1 + 4} , 100 ° C, the same applies hereinafter) 5 to 100, particularly 10 to 70 can be preferably used from the viewpoint of practicality such as vulcanization / foamability and sealing performance.

[0009] Organic peroxide is used as a vulcanizing agent for ethylene / propylene rubber, whereby high expansion ratio and corrosion resistance can be achieved. There is no particular limitation on the type of organic peroxide used, for example, di-t-
Butyl peroxide, dicumyl peroxide, α, α '
-Bis (t-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butyl Peroxy) hexyne-3, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane,
Appropriate ones such as di-t-butylperoxy-3,3,5-trimethylcyclohexane and t-butyl hydroperoxide may be used alone or in combination of two or more.

The amount of the organic peroxide to be used can be appropriately determined according to the effective concentration, the physical properties of the desired foam, and the like.
Generally, 50 parts by weight or less, preferably 1 to 40 parts by weight, particularly 5 to 3 parts by weight, per 100 parts by weight of ethylene / propylene rubber
0 parts by weight. In the vulcanization treatment, for example, ethylene di (meth) acrylate, ethylene glycol (meth) acrylate, triallyl isocyanurate, trimethylolpropane tri (meth) acrylate (T
MPTA), N, N'-m-phenylenebismaleimide and the like may be used alone or in combination of two or more.

Azodicarbonamide (ADCA) is used as a foaming agent, which can achieve safety and non-toxicity due to self-extinguishing properties. The amount of ADCA to be used can be appropriately determined depending on the physical properties of the target foam, such as the expansion ratio, and is generally 1 to 80 parts by weight, preferably 3 to 80 parts by weight, per 100 parts by weight of the ethylene / propylene rubber.
60 parts by weight, especially 5 to 40 parts by weight are used.

Borax (Na ₂ B ₄ O ₇ ) is used as a foaming aid for ADCA, whereby the decomposition temperature of ADCA can be effectively lowered to achieve a vulcanization and foaming treatment with a high foaming ratio and oxygen. Even when contact is made, the inhibition of cross-linking due to this can be prevented, the surface is tacky and stickiness can be avoided, and the smoothness of the surface can be improved.

The amount of borax used is 5 to 200% of ADCA.
% By weight. If the amount used is less than 5% by weight, ADC
The effect of lowering the decomposition temperature of A, the effect of avoiding stickiness, and the effect of smoothing the surface are poor, and if it exceeds 200% by weight, it is disadvantageous for lowering the density due to a high expansion ratio. The amount of borax to be used for ADCA is preferably 8 to 150% by weight, more preferably 10 to 120% by weight, from the viewpoints of lowering the decomposition temperature, avoiding stickiness, smoothing the surface and reducing the density.

The EP rubber composition is prepared by an appropriate method such as a method of mixing components such as ethylene / propylene rubber, organic peroxide, ADCA and borax through a kneader such as a kneader or a mixing roll. This can be done by mixing in a manner to form a blend of the ingredients. At this time, a mixing method in which the temperature is raised to such an extent that vulcanization proceeds is not preferable.

In the above-mentioned preparation, if necessary, an appropriate compounding agent according to the prior art may be added for the purpose of adjusting the viscosity, vulcanizability and moldability, and adjusting the physical properties such as the strength of the obtained foam.
Seeds or two or more kinds can be added. Examples include calcium carbonate and magnesium carbonate, silicic acid and its salts, calcium oxide and talc, clay and mica powder, zinc oxide and bentonite, carbon black and silica, aluminum hydroxide and magnesium hydroxide, alumina and aluminum silicate. Fillers such as acetylene black and aluminum powder, aluminum powder, stearic acid and esters thereof, polyethylene glycol, antioxidants, antioxidants and pigments, coloring agents and fungicides.

The above-mentioned calcium oxide is useful as a moisture absorbent, zinc oxide is useful as a stabilizer, carbon black is useful as a reinforcing agent, and stearic acid and its esters are also useful as lubricants. Examples of the components that may also contain a reinforcing agent and a lubricant are given. Further, a softener such as paraffin oil or process oil can be blended for the purpose of adjusting the formability such as sheet processability.

In addition, one or two types of rubber-based polymers other than non-rubber-based polymers and ethylene / propylene-based rubbers are added to the EP rubber-based composition for the purpose of controlling physical properties such as the strength of the obtained foam. The above can also be blended. As the non-rubber-based polymer or rubber-based polymer, an appropriate one can be used, and there is no particular limitation.

Examples of the non-rubber-based polymer include acrylic polymers such as poly (meth) acrylate, polyvinyl chloride, polyethylene and polypropylene, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyamide. And polyester, chlorinated polyethylene and urethane-based polymers, styrene-based polymers and silicone-based polymers, and epoxy-based resins.

Examples of the rubber-based polymer include a rubber-based copolymer containing a cyclic or non-cyclic polyene having a non-conjugated double bond such as α-olefin-dicyclopentadiene such as butene-1 or ethylidene norbornene. Polymer, silicone rubber, fluorine rubber, acrylic rubber, polyurethane rubber, polyamide rubber, natural rubber, polyisobutylene, polyisoprene, chloroprene rubber, butyl rubber, nitrile butyl rubber, styrene / butadiene rubber, styrene / butadiene / styrene Rubber, styrene / isoprene / styrene rubber, styrene / ethylene / butadiene rubber, styrene / ethylene / butylene /
Examples include styrene rubber, styrene / isoprene / propylene / styrene rubber, and chlorosulfonated polyethylene.

The amount of the rubber-based polymer other than the above-mentioned non-rubber-based polymer and ethylene-propylene-based rubber is set to 100% of the ethylene-propylene-based rubber in view of maintaining the rubber-like properties of the foamed ethylene-propylene rubber.
% By weight, preferably 70% by weight or less, particularly preferably 50% by weight or less.

The EP rubber foam can be formed by heating the EP rubber composition and subjecting it to vulcanization and foaming treatment. And vulcanized foam can be obtained by subjecting the molded body to heat treatment. In that case, the molded body may be formed into an arbitrary form by an appropriate method, and the form is not particularly limited.

Therefore, the object of the vulcanization / foaming treatment may be an EP rubber-based composition formed into a sheet or other form by an appropriate method such as a mixing roll, a calender roll, or extrusion molding. Alternatively, it may be formed into a predetermined form having irregularities or the like by an appropriate method such as injection molding or press molding through a predetermined mold.

In the formation of the foam having the uneven shape, the unvulcanized sheet is placed on a mold having unevenness and heated, and the mixture forming the unvulcanized sheet is flowed through the unevenness of the mold. It is also possible to adopt a method of vulcanizing and foaming by infiltration. Such a method has an advantage that the uneven shape can be accurately formed even in the case of a mold having a complicated deep uneven structure having a fold structure.

Accordingly, the size of the molded article is arbitrary, and can be appropriately determined according to the desired form of the vulcanized foam. By the way, in the case of a sheet etc., the thickness is 100
mm or less, especially 1 μm to 80 mm, particularly 10 μm to 50 mm.

The above-mentioned vulcanization / foaming treatment can be carried out under appropriate conditions according to the prior art, depending on the vulcanization start temperature and foaming temperature of the used organic peroxide, ADCA or the like. Typical vulcanization and foaming temperatures are about 250 ° C. or less,
220 ° C. Usually, the vulcanization and foaming treatment softens the EP rubber composition, decomposes ADCA, and forms a foamed structure, and vulcanization proceeds to form a desired vulcanized foam. The vulcanization / foaming treatment can be performed under pressure for the purpose of adjusting the expansion ratio and the like, and the conditions for the pressurization can be the same as those in the past.

In the present invention, the EP rubber-based foam, which is preferable from the viewpoint of lowering the density due to a high expansion ratio, has a density of 0.1.
It has been vulcanized and foamed so as to have a density of 0.5 to 0.6 g / cm ³ . Thereby, it is excellent in flexibility (deformability) and compressibility, and can be applied to a sealing portion for various purposes to achieve a highly accurate sealing process.

[0027] More preferred density of the foam from the viewpoint of the applicability and sealing performance, 0.5 g / cm ³ or less, especially 0.07~0.4g / cm ^3, especially 0.1 to 0. 35g /
cm ^3. The expansion ratio can be controlled by the amount of ADCA, the processing time and temperature of vulcanization and expansion, and the like. In addition, it is possible to control a foaming structure such as independent, continuous, or a mixture thereof through adjustment of the expansion ratio.

The EP rubber-based foam according to the present invention can be made of various conventional materials such as cushioning materials and padding materials, sealing materials for various purposes such as airtightness and waterproofing, heat insulating materials, and vibration reducing materials such as soundproofing and vibration suppression. It can be used for applications.

[0029]

EXAMPLES Example 1 70 parts (parts by weight, hereinafter the same) of EPDM (Mooney viscosity 45, iodine value 12), 30 parts of low density polyethylene, 5 parts of dicumyl peroxide (effective concentration 40%), 1,1-
5 parts of t-butylperoxy-3,3,5-trimethylcyclohexane (effective concentration 40%), 2 parts of TMPTA, A
DCA 25 parts, borax 3 parts, zinc oxide 5 parts, powdered stearic acid 3 parts, polyethylene glycol 1 part, carbon black (SRF carbon) 20 parts, calcium carbonate 15
0 parts, 4 parts of an antioxidant and 5 parts of calcium oxide are kneaded with a pressure kneader and a mixing roll to obtain an admixture, which is molded by an extruder to obtain an unvulcanized sheet.
Vulcanization foaming treatment by heating in a hot air oven for 40 minutes,
A foam sheet having a thickness of 10 mm was obtained.

Example 2 An admixture and a foamed sheet thereof were obtained in the same manner as in Example 1 except that the amount of borax was changed to 25 parts.

Comparative Example A mixture and a foamed sheet thereof were obtained in the same manner as in Example 1 except that borax was not added.

Evaluation Test The foamed sheets obtained in Examples and Comparative Examples were placed in an oven at 100 ° C., and their surfaces were touched with a finger to check for stickiness. Further, the cut surface of the foamed sheet was magnified 10 times with a microscope and observed, and the size of the irregularities on the surface was examined.

The results are shown in the following table. The table also shows the density of the foam sheet. Example 1 Example 2 Comparative Example Density (g / cm ³ ) 0.094 0.098 0.22 No stickiness No No Yes Surface unevenness (mm) 0.3 0.3 1.0

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/20 C08K 5/20 F term (Reference) 4F074 AA25 AC33 AG20 BA13 BB02 CA29 CC04Y CC06Y CC22X CC24X CC32Y CC34X CC42 CC46 DA02 DA32 DA35 DA39 DA47 4J002 BB151 DK008 EK016 EK036 EK046 EQ017 FD010 FD030 FD070 FD090 FD150 FD180 FD327 GJ01 GL00

Claims (2)

[Claims] An EP rubber comprising an ethylene / propylene rubber, an organic peroxide, an azodicarbonamide and a mixture containing at least 5 to 200% by weight of borax based on the azodicarbonamide. System composition. 2. Ethylene / propylene rubber, organic peracid
, Azodicarbonamide and azodicarboxylic acid
At least 5 to 200% by weight of borax based on mid
Consisting of a vulcanized foam of an admixture having a density of 0.05 to
0.6g / cm ³EP rubber foam characterized by being
body.