JP2001064429A - Rubber-based foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber-based foam hardly generating a sublimable substance and hardly causing fogging even at a high temperature without reducing sealing performances, etc. SOLUTION: This rubber-based foam comprises a vulcanized foam of a mixture composed of an ethylene/propylene-based rubber, an organic peroxide, azodicarbonamide, an zinc-based blowing auxiliary and 0.1-5 wt.% based on azodicarbonamide of a urea-based blowing auxiliary at least as components and has <=0.2 g/cm3 density, <=10 haze value of a glass plate used as a cover by the following testing conditions using and <=2 mg deposit of sublimable substance on the glass place. The testing condition comprises setting a foam having 100 mm length, 50 mm width and 10 mm thickness in a glass bottle having 40 mm inner diameter of an opening part, 70 mm inner diameter of bottom part and 160 mm height, immersing the glass bottle in an oil bath (110 mm oil depth) at 100 deg.C, covering the opening of the glass bottle with the glass plate, placing a weight of iron plate and allowing the glass plate for 20 hours.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber foam which is less likely to generate sublimates even at high temperatures, has excellent fogging resistance, and is suitable as a sealing material for various purposes.

[0002]

2. Description of the Related Art Conventionally, ethylene foam
It has been known that a propylene-based rubber is foamed with an azodicarbonamide and a urea-based foaming aid. 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, the above-mentioned rubber-based foam is used as a sealing material in the vicinity of various glass plates, for example, around the front, rear and windows of automobiles, around composite glass windows for houses, around plasma displays, around solar cell panels, and the like. When used as such, there is a problem that fogging due to a rise in temperature causes fogging of a glass plate or the like.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a rubber-based foam which is less likely to generate sublimates and cause fogging even at high temperatures without deteriorating sealing performance and the like.

[0005]

The present invention relates to an ethylene / propylene rubber, an organic peroxide, an azodicarbonamide, a zinc-based foaming aid and 0.1 to 5 parts by mass of the azodicarbonamide.
It comprises a vulcanized foam of an admixture containing at least a urea-based foaming aid at least as a component and has a density of 0.2 g / cm ³ or less and a haze value of a glass plate used for a lid under the following test conditions. It is intended to provide a rubber-based foam characterized in that the amount is 10 or less and the amount of sublimated matter attached to the glass plate is 2 mg or less. Note that the test conditions were 10
0 mm, 50 mm wide, 10 mm thick foam with an opening inside diameter of 40
mm, bottom inside diameter 70mm, height 160mm in a glass bottle, put in 100 ℃ oil bath (oil depth 110mm),
Cover the opening with a glass plate and put a weight of iron plate on top.
It is to leave for a while.

[0006]

According to the present invention, the decomposition temperature of azodicarbonamide is reduced by using a zinc-based foaming auxiliary in combination with the use of a urea-based foaming auxiliary, thereby achieving high expansion ratio (low density). A rubber type that can be vulcanized, shows high sealing performance due to good cushioning and compressibility of ethylene-propylene rubber foam, and does not easily generate contaminants due to volatilization and sublimation even at high temperatures and does not easily cause fogging A foam can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber foam according to the present invention comprises 0.1 to 5% by weight of ethylene / propylene rubber, organic peroxide, azodicarbonamide, zinc-based foaming aid and the azodicarbonamide. It consists of a vulcanized foam of an admixture containing at least a urea-based foaming aid and having a density of 0.
2 g / cm ³ or less, 100 mm long, 50 mm wide,
Foam with a thickness of 10 mm is formed by opening an inner diameter of 40 mm and a lower inner diameter of 70 mm.
In a glass bottle having a height of 160 mm and a height of 160 mm, put in an oil bath (oil depth 110 mm) at 100 ° C., cover the opening with a glass plate, put an iron plate weight on it, and let it stand for 20 hours. The haze value of the glass plate used for the lid is 10
Below and the amount of sublimation deposits on the glass plate is 2 mg
It consists of:

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.

The organic peroxide is used as a vulcanizing agent for an ethylene / propylene rubber, and has a density of 0.2 g.
/ Cm ³ or less, high foaming ratio and corrosion resistance. The type of the organic peroxide to be used is not particularly limited. 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-butylperoxy) hexine-3, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, di-t-butylperoxy-
Appropriate ones such as 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, an appropriate vulcanization aid such as ethylene dimethacrylate, ethylene glycol acrylate, triallyl isocyanurate, trimethylolpropane trimethacrylate, or N, N'-m-phenylenebismaleimide may be used in combination. it can.

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 50 parts by weight, preferably 3 to 50 parts by weight, per 100 parts by weight of the ethylene / propylene rubber.
30 parts by weight, especially 5 to 20 parts by weight are used.

On the other hand, in the present invention, a foaming aid is used for the purpose of lowering the decomposition temperature of ADCA.
A urea-based foaming aid of weight% is used in combination. With such a combination, the decomposition temperature of ADCA can be effectively lowered with a small amount of the urea-based foaming aid to achieve a vulcanization-foaming treatment with a high expansion ratio, and the generation of urea based on the urea-based foaming aid can be suppressed. It can be prevented that it volatilizes and sublimates as the temperature rises and becomes a causative substance of fogging.

When the amount of the urea foaming aid relative to ADCA is less than 0.1% by weight, the effect of lowering the decomposition temperature of ADCA is poor, and when it exceeds 5% by weight, the haze value and the amount of volatile sublimation substances generated increase. And poor fogging resistance. From the viewpoint of fogging resistance and the like, the preferred amount of the urea-based foaming aid to ADCA is 0.2 to 4% by weight, preferably 0.3 to 3% by weight.

As the zinc-based foaming auxiliary, for example, one or more kinds of appropriate ones such as zinc benzenesulfonate, zinc stearate and zinc acetate can be used. Can be appropriately determined according to the physical properties of the material. Generally 1 to 20 for ADCA
0% by weight, especially 3 to 100% by weight, especially 5 to 50% by weight
Is used.

The blend is prepared by blending components such as ethylene / propylene rubber, organic peroxide, ADCA, zinc foaming aid, and urea foaming aid through a kneader such as a kneader or a mixing roll. The mixing can be performed by an appropriate method such as a mixing method. At this time, a mixing method in which the temperature is raised to such an extent that vulcanization proceeds is not preferable.

In preparing the admixture, an appropriate compounding agent according to the related art may be used, if necessary, for the purpose of adjusting the moldability, viscosity and vulcanizability, and adjusting the physical properties such as the strength of the obtained foam. One or two or more can be added.

Incidentally, a softening agent may be blended for the purpose of controlling moldability, etc., but in the present invention, in order to prevent volatile sublimation at high temperatures, for example, a high molecular weight paraffin having a flash point of 260 ° C. or higher is used. A heat-resistant oil-based softening agent such as a system oil is preferably used. The amount of the softening agent can be appropriately determined according to the moldability such as sheet processability, but is generally 1 to 100 parts by weight, preferably 5 to 80 parts by weight, per 100 parts by weight of the ethylene / propylene rubber, Especially 10
50 parts by weight.

The admixture includes calcium carbonate and magnesium carbonate, silicic acid and salts thereof, calcium oxide and talc, clay and mica powder, zinc white and bentonite, carbon black and silica, aluminum hydroxide and magnesium hydroxide, alumina And fillers such as aluminum, aluminum silicate, acetylene black and aluminum powder, stearic acid and esters thereof, an antioxidant, an antioxidant, a pigment and a coloring agent, and a fungicide.

The above-mentioned calcium oxide is useful as a hygroscopic agent, zinc white 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.

In addition, one or more rubber-based polymers other than non-rubber-based polymers and ethylene / propylene-based rubbers are blended with the mixture for the purpose of controlling physical properties such as strength of the obtained foam. You can also. 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 50% of the ethylene-propylene-based rubber in view of maintaining the rubber-like properties of the foamed ethylene-propylene-based rubber. % By weight, preferably 30% by weight or less, particularly preferably 15% by weight or less. In addition, it is preferable that the compounding agent to be added to the above-mentioned admixture as required is one that is hard to volatilize and sublimate, particularly one that is hard to volatilize and sublimate at high temperature.

The rubber-based foam according to the present invention can be formed by heating and vulcanizing and foaming the above-mentioned admixture. In forming the admixture, the admixture may be formed, if necessary, into a predetermined form such as a sheet. , And then heat-treat the molded body to form a vulcanized foam. 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 to be subjected to the vulcanization and foaming treatment may be an object obtained by molding the mixture into a sheet or other form by an appropriate method such as a mixing roll, a calender roll, or extrusion molding. It may be molded into a predetermined form having irregularities or the like by an appropriate method such as injection molding or press molding through a mold.

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

Therefore, the size of the molded article is arbitrary, and can be appropriately determined according to the desired form of the vulcanized foam. In the case of a sheet or the like, the thickness is 100 mm or less,
In particular, 1 μm to 80 mm, especially 10 μm to 50 mm is common.

The above-mentioned vulcanization / foaming treatment can be carried out under appropriate conditions according to the prior art, depending on the starting temperature of vulcanization by the organic peroxide or ADCA used, the foaming temperature, and the like. The general vulcanization and foaming temperature is about 200 ° C. or less,
180 ° C. Usually, the vulcanization and foaming treatment softens the admixture and decomposes the ADCA to form 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 above, according to the present invention, a rubber foam having a density of 0.2 g / cm ³ or less is obtained by vulcanizing under a high expansion ratio. 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. The preferred density of the foam is 0.18 g / cm ³ or less, particularly 0.05 to 0.16 g / cm ³ , particularly 0.1 to 0.1 g / cm ^{3 in} view of its applicability and sealing performance.
0.15 g / 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. Further, it is possible to control the foaming structure such as independent or continuous vulcanized foam, mixing thereof, etc., by adjusting the expansion ratio.

Further, in the present invention, the admixture having the above composition is subjected to vulcanization and foaming treatment to obtain a 100 m long product.
m, width 50mm, thickness 10mm foam with opening inside diameter 40m
m, placed in a glass bottle with a bottom inner diameter of 70 mm and a height of 160 mm, and put in a 100 ° C oil bath (oil depth 110 mm)
Cover the opening with a glass plate and put a weight of iron plate on top.
When the fogging test was conducted under the condition of leaving for a period of time, the haze value of the glass plate used for the lid was 10 or less, particularly 8 or less, particularly 6 or less, and the amount of sublimation deposits on the glass plate was 2 mg or less. It is a system foam. The haze value is defined as scattered transmitted light / total transmitted light.

The rubber-based foam according to the present invention includes 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. Can be used for applications. In particular, because of excellent fogging resistance, for example, the temperature rises due to the operation of devices such as various glass plates such as windows and sealing materials around solar cell panels, plasma displays and the like in buildings such as automobiles and houses that rise in temperature due to direct sunlight. It can be preferably used as a sealing material for a rising display panel.

[0032]

EXAMPLES Example 1 70 parts of EPDM (Mooney viscosity 45, iodine value 12, the same applies hereinafter), 70 parts (parts by weight, the same applies hereinafter), low-density polyethylene 30 parts, organic peroxide (effective concentration 40%, the same applies hereinafter) 1
0 parts, ADCA 20 parts, zinc benzenesulfonate 5 parts,
About 3% by weight of ADCA urea-based foaming aid, zinc white 5
Parts, powder stearic acid 1 part, polyethylene glycol 1
Part, carbon black (SRF carbon, the same applies hereinafter) 2
0 parts, aluminum hydroxide 150 parts, antioxidant 4 parts,
5 parts of calcium oxide and 2 parts of ethylene dimethacrylate 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, which is placed in an oven at 160 ° C. for 30 minutes. After heating for 10 minutes, the foam was vulcanized and foamed, and the surface was sliced to obtain a foamed sheet having a thickness of 10 mm.

Example 2 70 parts of EPDM, 30 parts of low density polyethylene, 4.5 parts of organic peroxide, 20 parts of ADCA, 10 parts of zinc stearate
Part, urea-based foaming aid 0.5 part, zinc white 5 parts, powdered stearic acid 1 part, polyethylene glycol 5 parts, carbon black 20 parts, calcium carbonate 150 parts, antioxidant 4
, A foamed sheet was obtained in the same manner as in Example 1, except that an admixture consisting of 5 parts of calcium oxide and 2 parts of ethylene dimethacrylate was used.

Example 3 70 parts of EPDM, 30 parts of low-density polyethylene, 10 parts of organic peroxide, 20 parts of ADCA, 3 parts of zinc acetate, 5 parts of zinc white
Parts, powder stearic acid 1 part, polyethylene glycol 1
Parts, carbon black 20 parts, calcium carbonate 150
, A foamed sheet was obtained in the same manner as in Example 1 except that an admixture consisting of 4 parts of an antioxidant, 5 parts of calcium oxide and 2 parts of ethylene dimethacrylate was used.

Comparative Example 1 70 parts of EPDM, 30 parts of low-density polyethylene, 14 parts of organic peroxide, 20 parts of ADCA, 10 parts of urea-based foaming aid,
In addition to using an admixture consisting of 5 parts of zinc white, 1 part of powdered stearic acid, 1 part of polyethylene glycol, 20 parts of carbon black, 150 parts of calcium carbonate, 4 parts of an antioxidant, 5 parts of calcium oxide and 2 parts of ethylene dimethacrylate A foamed sheet was obtained according to Example 1.

Comparative Example 2 EPDM 70 parts, low density polyethylene 30 parts, organic peroxide 20 parts, OBSH 30 parts, zinc white 5 parts, powdered stearic acid 1 part, polyethylene glycol 3 parts, carbon black 20 parts, calcium carbonate 150 parts , Anti-aging agent 4
, A foamed sheet was obtained in the same manner as in Example 1, except that an admixture consisting of 5 parts of calcium oxide and 2 parts of ethylene dimethacrylate was used.

Evaluation test: 100 mm long, 50 mm wide, and 10 mm thick obtained in Examples and Comparative Examples
mm foam sheet, opening inner diameter 40mm, bottom inner diameter 70mm,
Place it on the bottom of a 160 mm high glass bottle, put it into a 100 ° C silicone oil bath (oil depth 110 mm) with the opening up, cover the opening with a glass plate, and put iron plate weight on it. After allowing the glass plate to stand for 20 hours, the haze value of the glass plate placed in the opening and the weight of the glass plate sublimated and adhered were examined.

The results are shown in the following table. The table also shows the density of the foam sheet. Example 1 Example 2 Example 3 Example 3 Comparative Example 1 Comparative Example 2 Density (g / cm ³ ) 0.137 0.147 0.200 0.141 0.140 Haze value (%) 4.8 5.8 1.3 43.1 40.0 mg) 2.0 1.0 0.5 14 3.0

Claims (2)

[Claims] 1. An ethylene / propylene rubber, an organic peroxide, an azodicarbonamide, a zinc-based foaming aid and 0.1 to 5% by weight of a urea-based foaming aid based on the azodicarbonamide are at least components. It consists of a vulcanized foam of an admixture, has a density of 0.2 g / cm ³ or less, a haze value of a glass plate used for a lid under the following test conditions of 10 or less, and an amount of sublimated deposits on the glass plate. A rubber foam characterized by being 2 mg or less. Test conditions: A foam having a length of 100 mm, a width of 50 mm and a thickness of 10 mm is placed in a glass bottle having an opening of 40 mm, a bottom of 70 mm, and a height of 160 mm, placed in a 100 ° C oil bath (oil depth 110 mm), and the opening is made of glass. Cover with a plate, put iron plate weight on it, and leave it for 20 hours. 2. The rubber foam according to claim 1, wherein the zinc foaming auxiliary is zinc benzenesulfonate, zinc stearate or zinc acetate.