JP6744044B2 - Rubber composition for rubber foam, rubber foam and sealing material obtained by foaming the same - Google Patents

Description

The present invention relates to a rubber composition for a rubber foam, and further relates to a sealing material obtained by foaming the rubber composition for a rubber foam to form a rubber foam.

2. Description of the Related Art Conventionally, in structures such as buildings, vehicles, and electronic devices, water sealing, heat insulation, and sound absorption are performed by filling a gap between each member with a sealing material. For example, roof tile doors of houses, around sashes, around shutters, joints on outer walls, metal roof joints, automobile window dams, around sunroofs, around doors, cowl top seals, etc. Widely used for machine doors, refrigerator backs, etc. As such a sealing material, a synthetic resin or rubber foam is used. Since the foamed body has an appropriate repulsive force (compressive stress), it can follow the unevenness of the surface of the material to be sealed and adhere to it by only applying a small amount of compressive deformation, and excellent sealing properties can be achieved.

Among them, since they have excellent weather resistance, heat resistance, and sealability, a rubber component such as ethylene-α-olefin-diene copolymer rubber, a vulcanizing agent such as sulfur, and a foaming agent such as azodicarbonamide are used. A rubber foam obtained by vulcanizing and foaming the compounded rubber composition is preferably used as a sealing material (Patent Document 1).
In addition, various attempts have been made conventionally to impart flame retardancy to a rubber foam using an ethylene-α-olefin-diene copolymer rubber. That is, as a flame retardant, one or more kinds of chlorinated polyethylene, chlorinated paraffin, decabromodiphenyl ether, antimony trioxide and aluminum hydroxide have been used to flame retard a rubber foam. However, it has been pointed out that chlorine-based materials cause metal corrosion problems, decabromodiphenyl ether causes environmental problems due to the generation of dioxins, and antimony trioxide also causes environmental problems due to toxicity. As a chemical method, it has been attempted to use aluminum hydroxide and/or magnesium hydroxide (Patent Document 2).

JP 2000-313762 A JP 2001-131320 A

When the rubber composition for a rubber foam contains a large amount of aluminum hydroxide and/or magnesium hydroxide, it may affect the vulcanization characteristics and the foaming characteristics, and may adversely affect the water blocking property. Therefore, an object of the present invention is to provide a rubber composition for a rubber foam using an ethylene-propylene-non-conjugated diene copolymer, which is capable of suitably achieving both waterproofness and flame retardancy without giving such an adverse effect. It is to provide things.

As a result of extensive studies by the present inventor, it is possible to solve the above problems by incorporating expanded graphite and red phosphorus as a flame retardant in a rubber component containing an ethylene-propylene-non-conjugated diene copolymer. I found it. The present invention has been completed based on such findings.

That is, the present invention provides the following inventions [1] to [3].
[1] A rubber composition containing a rubber component containing an ethylene-propylene-non-conjugated diene copolymer, a foaming agent, a flame retardant and a vulcanizing agent, wherein the ethylene-propylene-non-conjugated diene copolymer contains The content of the non-conjugated diene is 9 to 15% by mass, the content of the foaming agent is 50 parts by mass or less with respect to 100 parts by mass of the rubber component, and the flame retardant contains expanded graphite and red phosphorus. The content of the expanded graphite is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, and the content of the red phosphorus is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. A rubber composition for a rubber foam, wherein the total content with red phosphorus is 20 parts by mass or more based on 100 parts by mass of the rubber component.
[2] A rubber foam obtained by foaming the rubber composition for a rubber foam according to [1].
[3] A sealing material using the rubber foam according to [2].

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for rubber foams which can make water stoppage and flame retardancy highly compatible can be provided.

It is a perspective view showing a U-shaped sample used for waterproofing evaluation. It is a schematic diagram showing an outline of a U-shaped test method by water stop evaluation.

Hereinafter, the present invention will be described in detail.
In addition, in this invention, description of "AB" showing numerical limitation means the numerical range containing A and B which are end points.
Moreover, a mass part and mass% are synonymous with a weight part and weight%, respectively.
Furthermore, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

<Rubber composition for rubber foam>
Hereinafter, the rubber composition for a rubber foam of the present invention will be described.
The rubber composition for a rubber foam of the present invention is a rubber composition containing a rubber component containing an ethylene-propylene-non-conjugated diene copolymer, a foaming agent, a flame retardant and a vulcanizing agent, wherein the ethylene-propylene -The content of the non-conjugated diene in the non-conjugated diene copolymer is 9 to 15% by mass, the content of the foaming agent is 50 parts by mass or less based on 100 parts by mass of the rubber component, and the flame retardant is Expanded graphite and red phosphorus are contained, the content of the expanded graphite is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, and the content of the red phosphorus is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. Parts, and the total content of the expanded graphite and the red phosphorus is 20 parts by mass or more with respect to 100 parts by mass of the rubber component.
When the content of the non-conjugated diene in the ethylene-propylene-non-conjugated diene copolymer is less than 9% by mass, the number of cross-linking points is small, so that cracks due to foaming gas are likely to occur and the content is 15% by mass. If it exceeds the above range, the number of cross-linking points is large, so that the foam does not swell sufficiently and none of the objects of the present invention can be achieved. From these viewpoints, the content of the non-conjugated diene in the ethylene-propylene-non-conjugated diene copolymer is preferably 9 to 14% by mass, more preferably 9 to 13% by mass, and 9 to 9% by mass. It is particularly preferably 12% by mass.
When the content of the foaming agent exceeds 50 parts by mass with respect to 100 parts by mass of the rubber component, the vulcanization characteristics are adversely affected, and the foaming gas amount becomes excessive, so that a good foam cannot be obtained, and the content of the expanded graphite. Is less than 5 parts by mass with respect to 100 parts by mass of the rubber component, sufficient flame retardancy cannot be obtained, and if the content of red phosphorus is less than 5 parts by mass with respect to 100 parts by mass of the rubber component, The balance of vulcanization/foaming is poor, it does not swell sufficiently due to outgassing, and if the content of red phosphorus exceeds 30 parts by mass with respect to 100 parts by mass of the rubber component, the unvulcanized rubber composition is adversely affected in processability and foamability. If the total content of expanded graphite and red phosphorus is less than 20 parts by mass with respect to 100 parts by mass of the rubber component, sufficient flame retardancy cannot be obtained, and any of the objects of the present invention can be achieved. It cannot be achieved.

[Ethylene-Propylene-Nonconjugated Diene Copolymer]
Examples of the non-conjugated diene used in the ethylene-propylene-non-conjugated diene copolymer according to the present invention include 1,4-hexadiene, 1,6-octadiene, 1,7-octadiene, 1,8-nonadiene and 1,9. -Decadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-hexadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinyl-2- Norbornene (vinyl norbornene), 5-ethylidene-2-norbornene, 5-methylene-2-norbornene and the like can be mentioned. In particular, it is preferable to contain 5-ethylidene-2-norbornene because the effects of the present invention can be obtained well.

[Rubber component]
In the present invention, the rubber component needs to contain an ethylene-propylene-non-conjugated diene copolymer, and the rubber component may contain 80 to 100 mass% of the ethylene-propylene-non-conjugated diene copolymer. From the viewpoint of weather resistance and heat resistance, it is more preferably contained in an amount of 85 to 100% by mass, further preferably 90 to 100% by mass.
As the rubber component in the present invention, other rubber component may be secondarily used in addition to the ethylene-propylene-non-conjugated diene copolymer. Other rubber components include ethylene-propylene rubber (EPM), butyl rubber (IIR), isoprene rubber (IR), natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), 1, Examples thereof include 2-polybutadiene (RB), acrylic rubber (ACM, ANM), chlorosulfonated polyethylene (CSM), chloroprene rubber (CR), and silicone rubber. Among them, at least one selected from the group consisting of EPM and IIR is preferable.

[Foaming agent]
The foaming agent in the present invention is used not only for generating gas for foaming but also for controlling vulcanization of the rubber component. Examples of the foaming agent include organic foaming agents and inorganic foaming agents.
Examples of the organic foaming agents include azodicarbonamide (ADCA), barium azodicarboxylate, azobisisobutyronitrile (AIBN), azocyclohexyl nitrile, azodiaminobenzene, and other azo foaming agents, such as N, N'-nitroso-based foaming agents such as N'-dinitrosopentamethylenetetramine (DPT), N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trinitrosotrimethyltriamine, for example 4,4'-oxybis (Benzenesulfonyl hydrazide) (OBSH), paratoluenesulfonyl hydrazide, diphenylsulfone-3,3'-disulfonylhydrazide (OBSH), 2,4-toluenedisulfonylhydrazide, p,p-bis(benzenesulfonylhydrazide)ether, Hydrazide-based blowing agents such as benzene-1,3-disulfonylhydrazide and allylbis(sulfonylhydrazide), for example, semicarbazide-based blowing agents such as p-toluylenesulfonyl semicarbazide and 4,4′-oxybis (benzenesulfonylsemicarbazide), for example , Trichloromonofluoromethane, dichloromonofluoromethane, and other fluorinated alkane-based foaming agents, for example, 5-morpholyl-1,2,3,4-thiatriazole and other triazole-based foaming agents, and other known organic foaming agents. Can be mentioned. Examples of the organic foaming agent include heat-expandable fine particles in which a heat-expandable substance is encapsulated in microcapsules. Examples of such heat-expandable fine particles include, for example, Microsphere (trade name, Matsumoto). Commercially available products such as Yushi Co., Ltd. can be mentioned.
As the inorganic foaming agent, for example, sodium hydrogen carbonate, hydrogen carbonate such as ammonium hydrogen carbonate, for example, sodium carbonate, carbonate such as ammonium carbonate, for example, sodium nitrite, nitrite such as ammonium nitrite, for example, hydrogen. Examples thereof include borohydride salts such as sodium borohydride, for example, azides, and other known inorganic foaming agents.
The foaming agent is preferably an organic foaming agent, more preferably an azo foaming agent. These foaming agents may be used alone or in combination of two or more.
In particular, azodicarbonamide (ADCA) is preferable in terms of good foamability, safety, and nontoxicity.

In the present invention, the foaming agent is preferably contained in a larger amount than usual in order to reduce the density of the rubber foam. However, if the content is too large, the rubber foam may be cracked, so the content of the foaming agent needs to be 50 parts by mass or less with respect to 100 parts by mass of the rubber component. In addition, the content of the foaming agent is preferably 18 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 25 parts by mass or more, with respect to 100 parts by mass of the rubber component, from the viewpoint of improving the waterproofness. More preferably, it is 30 parts by mass or more. The content of the foaming agent is preferably 45 parts by mass or less, and particularly preferably 35 parts by mass or less with respect to 100 parts by mass of the rubber component. Further, from the viewpoint of simultaneously improving the water blocking resistance and preventing the rubber foam from cracking, 18 to 35 parts by mass is preferable, and 30 to 35 parts by mass is more preferable, relative to 100 parts by mass of the rubber component.

[Foaming aid]
In the present invention, in the rubber composition for rubber foam, a urea-based, salicylic acid-based, or benzoic acid-based foaming aid is used as a foaming aid.
Examples of the foaming aid include urea-based foaming aids, salicylic acid-based foaming aids, benzoic acid-based foaming aids, and metal oxides (eg, zinc oxide). Preferred are urea foaming aids and metal oxides. These foaming aids may be used alone or in combination of two or more. Urea is mentioned as a preferable urea type foaming auxiliary agent.
The content ratio of the foaming aid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. Below the section.

[Flame retardants]
The flame retardant in the present invention contains expanded graphite and red phosphorus. Expanded graphite mainly has a function of preventing a bond between a combustion substance and oxygen to prevent formation of an oxidation reaction field in a combustion cycle, and when the content of expanded graphite is small, such an action effect is sufficiently exerted. However, the flame is likely to rise and combustion is likely to spread. Therefore, from this viewpoint, the content of the expanded graphite needs to be 5 parts by mass or more, preferably 6 parts by mass or more, more preferably 8 parts by mass or more, and more preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. The above is more preferable. On the other hand, when the content of the expanded graphite is too large, the expanded graphite expands too much and adversely affects the processability and foamability of the unvulcanized rubber composition. From the viewpoint of preventing this, 100 parts by mass of the rubber component is used. On the other hand, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and further preferably 22 parts by mass or less. The content of the expanded graphite is particularly preferably 10 to 20 parts by mass with respect to 100 parts by mass of the rubber component.
Further, the content of red phosphorus needs to be 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and from the viewpoint of improving flame retardancy, it is preferably 10 to 30 parts by mass, and 15 to 30 parts by mass. It is more preferable that the amount is not more than parts by mass.
From the viewpoint of improving flame retardancy, the total content of expanded graphite and red phosphorus needs to be 20 parts by mass or more, preferably 25 parts by mass or more, with respect to 100 parts by mass of the rubber component. More preferably, it is at least part by mass. The total content of expanded graphite and red phosphorus is preferably 60 parts by mass or less, and 55 parts by mass or less with respect to 100 parts by mass of the rubber component in order to avoid the content of the expanded graphite being too large. Is more preferable, and even more preferably 50 parts by mass or less.

The mass ratio of the content of red phosphorus to the content of the foaming agent in the present invention (content of red phosphorus/content of the foaming agent) is 0.28 to 10 from the viewpoint of adjusting the density by the balance of vulcanization and foaming. It is preferably 0.86, and more preferably 0.43 to 0.86.

[Vulcanizing agent]
The vulcanizing agent in the present invention is not particularly limited, but examples thereof include sulfur and sulfur compounds, organic peroxides, polyamines, oximes, and nitroso compounds. These can be used alone or in combination of two or more. The vulcanizing agent preferably contains sulfur from the viewpoint that the vulcanized and foamed state of the obtained rubber foam is good. The content of the vulcanizing agent is preferably 0.5 to 30 parts by mass, particularly 1.0 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

In the present invention, “vulcanization” is used synonymously with “crosslinking” without being limited to crosslinking with sulfur.

[Reinforcement material]
In the present invention, the rubber composition for rubber foam may contain a reinforcing material. The reinforcing material is not particularly limited, but for example, carbon black or an inorganic reinforcing material (particularly silica) is preferably used. The content is not particularly limited and can be used within a range that does not impair the effects of the present invention. However, the rubber composition for a rubber foam of the present invention is used for 100 parts by mass of the rubber component from the viewpoint of improving water blocking performance. The reinforcing material is contained in an amount of 10 to 100 parts by mass, preferably 15 to 80 parts by mass, more preferably 20 to 80 parts by mass.

[Filling material]
In the present invention, the rubber composition for rubber foam may contain a filler other than the reinforcing material. The filler is not particularly limited, for example, calcium carbonate or magnesium carbonate, silicic acid or its salts or talc, clay or mica powder, bentonite, aluminum hydroxide or magnesium hydroxide, alumina or aluminum silicate, Acetylene black, aluminum powder, ceramics, glass fiber, wood powder, fiber waste, etc. can be used. The content is not particularly limited, and it can be used within a range that does not impair the effects of the present invention on the waterproofness and flame retardancy.

[Other]
In the present invention, the rubber composition for a rubber foam may further contain other additives depending on the purpose. For example, in order to accelerate vulcanization, thiazole-based, dithiocarbamate-based, thiourea-based, dithiophosphite-based, thiuram-based vulcanization accelerators; vulcanization accelerating aids such as zinc oxide (active zinc white), foaming A foam control agent containing a fatty acid such as stearic acid or a fatty acid metal salt such as zinc stearate or calcium stearate for controlling the diameter of bubbles generated by; process oils such as paraffin oil and naphthene oil, blow asphalt, polybutene, rosin and rosin Resin softeners such as esters; resins such as polyethylene, polypropylene and ethylene-vinyl acetate copolymers; mechanical strength improvers such as calcium oxide; antioxidants and antioxidants, pigments and colorants, antifungal agents, etc. Used. One or two or more of these additives can be added as required. There is no particular limitation on the amount added, and it can be used within a range that does not impair the effects of the present invention in terms of waterproofness and flame retardancy.

[Rubber foam]
The rubber foam of the present invention is produced by vulcanizing and foaming the composition for a rubber foam of the present invention. In the rubber foam of the present invention, the average cell diameter is preferably 20 to 150, and more preferably 20 to 120 as the average number of cells existing in an area of 1 square inch {(inch) ² }. If the average cell diameter is 20 or more, it is preferable from the viewpoint of improving waterproofness, and if the average cell diameter is 150 or less, the compression hardness of the rubber foam does not become too high, which is preferable. The average cell diameter is obtained by observing the test piece with a stereoscopic microscope and measuring the number of cells present in an area of 1 square inch {(inch) ² } 20 times, and averaging the measured values.
The rubber foam of the present invention has a compression hardness of 0.5 kPa or more, which is preferable from the viewpoint of improving waterproofness, and a compression hardness of 150 kPa or less makes assembly and ease of assembly as a sealing material easier. It is preferable from the viewpoint of suppressing the deformation of the attached component. The compression hardness is a value obtained by measuring the compression hardness (kPa) of a rubber foam by compressing 50% of the initial thickness according to JIS K 6767:1999. The compression hardness is more preferably 0.5 to 120 kPa, further preferably 0.5 to 100 kPa.
In addition, the rubber foam having a closed cell structure preferably has a tensile strength at elongation break of 35 to 100 kPa in the longitudinal direction, and more preferably 50 to 90 kPa. The tensile strength is a value measured according to JIS K 6767:1999.

[Method for producing rubber foam and sealing material]
The rubber foam of the present invention can be specifically carried out, for example, in the following steps.
First, materials excluding a foaming agent, a vulcanizing agent, a vulcanization accelerator used as necessary, a foam control agent and the like (including stearic acid, zinc stearate, calcium stearate and calcium oxide) are mixed and kneaded. The kneading can be performed using a closed mixer such as a Banbury mixer, a kneader, or an intermix. The kneading is preferably performed at a temperature of 80 to 170° C., particularly 90 to 140° C. for 2 to 20 minutes. After that, a foaming agent, a vulcanization aid, a vulcanizing agent, a bubble size control agent and calcium oxide are added to the kneaded product and kneaded. This kneading is preferably carried out at 40 to 90° C., particularly 50 to 90° C. for 5 to 30 minutes. The kneaded product thus obtained is molded into a desired shape such as a sheet by a calender molding machine, an extrusion molding machine or the like.

The kneaded product is molded into a desired shape, then introduced into a vulcanization apparatus, and heated at 130 to 270° C., particularly 140 to 200° C. for 1 to 60 minutes to be vulcanized and foamed (vulcanized foaming). Process). As a result, a rubber foam having a closed cell structure is obtained. As a heating method in the vulcanization tank, heating means such as a hot air vulcanization tank (HAV), a fluidized bed of glass beads, a microwave vulcanizer (UHF), and steam can be used. The vulcanization and foaming may be performed simultaneously or sequentially under different temperature conditions.

When the sealing material of the present invention is produced, it is preferable to further perform a foam breaking treatment step after the vulcanization and foaming step of the sealing material composition. The sealing material of the present invention has good defoaming property and does not crack, break, or deform during the defoaming process. Therefore, by the foam breaking treatment, it is possible to obtain a sealing material having higher dimensional stability and flexibility and improved sealing performance such as waterproofness.

The foam-breaking treatment step is performed in order to impart a continuous-cell structure to the rubber foam by breaking at least some of the closed cells to make them open. The defoaming process is performed using a normal method, such as a method of pressing the rubber foam between a pair of rotating rolls (roll crush method), a method of placing the rubber foam under vacuum and compressing it (vacuum crush method). ), a method of punching with an infinite number of needles using a needle punch (needle punching method), a method of pressing a rubber foam between a pair of flat plates (flat plate pressing method), and the like. Among them, the roll crush method is preferably used because it can surely perform the bubble breaking process.

Specifically, the roll crush method is performed by compressing and deforming a rubber foam having a closed cell structure in the thickness direction by a pair of rotating rolls. To promote continuous formation of air bubbles by providing an infinite number of small needles on the surface of the rotating roll or arranging a roll or a needle punch having an infinite number of small needles before and/or after a pair of rotating rolls. You can

At this time, the rubber foam having a closed cell structure is preferably compressed so that the thickness thereof becomes 1/10 to 1/2, particularly 1/5 to 1/2. The pair of rotating rolls may be used in plurality to perform the foam breaking process of the rubber foam multiple times, and at this time, the distance between the pair of rotating rolls may be different from each other. The diameter of each of the pair of rotating rolls is preferably 5 cm or more. The rotation speed of the rotating roll is preferably 3 to 70 m/min, and particularly preferably 25 to 50 m/min. In order to improve the efficiency of the wave bubble treatment, the rotation speed of at least one of the pair of rotating rolls may be changed.

The closed cell content of the sealing material to which the open cell structure is imparted by the foam breaking treatment is 20% or less, particularly 1 to 10%, and it is preferable that the sealing material has a high open cell content. The closed cell rate is a value measured according to the method specified in ASTM D2856.

Apparent density of the sealing material obtained by the process of the present invention (weight / volume) is not particularly limited, preferably at 200 kg / ^{m 3} or less, more preferably 180 kg / ^{m 3} or less, in particular 170 kg / ^{m 3} or less is there. The apparent density of the sealing material is preferably 20 kg/m ³ or more, more preferably 30 kg/m ³ or more. If the density is in such a range, it can be said that the sealing material has a sufficiently low density. This density is not related to the presence or absence of the foam breaking treatment step, but is preferably an apparent density in such a range after the foam breaking treatment. The apparent density is a value measured according to the method defined in JIS K 6767:1999.

The sealing material of the present invention is, for example, a vehicle such as a window dam; an electric equipment such as an air conditioner, a washing machine, a refrigerator, a vending machine; an audio equipment; an outer wall joint, sashes, a roof material joint, etc.; a kitchen equipment, a unit. It is used to seal the gap between members in housing equipment such as buses and water heaters; in structures, joints of roads and bridges, and civil engineering such as waterway joints. Further, the sealing material is used as a dustproof material, a heat insulating material, a soundproof material, a vibrationproof material, a cushioning material, a watertight material and an airtight material. You can also

The sealing material preferably has a sheet-like shape, and may be subjected to a treatment such as applying an adhesive or a double-sided tape on at least one surface and attaching a release paper. The thickness of the sealing material may be determined according to the application, but it is preferably 20 to 100 mm.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, parts and% mean parts by mass and% by mass, respectively, unless otherwise specified.

In the following examples and comparative examples, the average cell diameter, compression hardness, foam shape, apparent density, water blocking property, and flame retardancy were measured by the following methods.
1. Average cell diameter {Average number/(inch) ² }
The average cell diameter was determined by observing the test piece with a stereoscopic microscope and measuring the number of cells present in an area of 1 square inch {(inch) ² } 20 times, and averaging the measured values.
2. Compression hardness (kPa)
According to JIS K 6767:1999, the compression hardness (kPa) of the rubber foam was measured by compressing only 50% of the initial thickness.
3. Foamed shape The outer appearance of the rubber foam was visually observed. Neither crack nor surface shrinkage was observed, and a good appearance was confirmed as "○", surface shrinkage and swelling were "△", cracking occurred, and foaming was defective. Some of them and those out of gas were evaluated by "x".
4. Apparent density (kg/m ³ )
The apparent density (kg/m ³ ) of the rubber foam was measured according to the method specified in JIS K 6767:1999.
5. As shown in FIG. 1, the sealing material after the water-stopping and defoaming treatment is U-shaped with a thickness (a) of 10 mm, a width (e) of 10 mm, a height (f) of 130 mm, and an interval (g) between both ends of 45 mm. Sample S1 is punched out into a shape, and is compressed by 70% or 80% in the thickness direction with two acrylic plates 2 and 3 as shown in FIG. 2, and a height (h2) of 100 mm is formed in the U shape. Water was added up to and the time (H) until the water leaked was measured.
A: No water leakage was observed for 24 hours or more.
◯: Water leakage was observed after 24 hours.
Δ: Water leakage was observed after 1 hour.
×: Water leakage was observed in less than 1 hour.
6. Flame retardancy The flame retardancy of the rubber foam was measured according to the flammability UL94 standard shown below.
Test method: A gas burner flame is contacted with the lower end of the sample (rubber foam) held vertically for 10 seconds. If the combustion stops within 30 seconds, indirect flame for another 10 seconds.
Judgment criteria:
V-0: There is no sample (rubber foam) that continues burning for 10 seconds or more after any flame contact.
The total burn time for 10 flame contacts for 5 samples (rubber foam) does not exceed 50 seconds.
There is no sample (rubber foam) that burns to the position of the fixing clamp.
Ignite absorbent cotton placed below the sample (rubber foam) There is no sample (rubber foam) that drops burning particles.
After the second flame contact, there is no sample (rubber foam) that keeps glowing for 30 seconds or more.
Those satisfying the above V-0 criterion were rated as ◯ (good), and those not satisfying were rated as x (poor).

Examples 1-8 and Comparative Examples 1-14
Of the rubber foam raw materials shown in Table 1, the rubber component, the filler, the softening agent, the reinforcing material and the flame retardant were put into a kneader, and the mixture was kneaded at 140° C. for 10 minutes and then cooled to a surface temperature of 25° C. A mixture of different types was obtained. Then, each of the obtained 22 kinds of kneaded materials and other materials (foaming agent, foaming aid, vulcanizing agent, vulcanization accelerator, vulcanization accelerating aid (active zinc white, zinc white, etc.) and vulcanization acceleration The activator (stearic acid or the like)} was put into a kneader and kneaded at 90° C. for 7 minutes to obtain 22 kinds of rubber compositions for rubber foams. Then, the obtained 22 types of rubber compositions for a rubber foam were molded into a sheet by an extruder for rubber, put into a heating furnace, and vulcanized and foamed at 170° C. for 60 minutes to form a closed cell structure. 22 kinds of rubber foams were obtained.
Next, a rubber foam having a closed cell structure is continuously supplied between a pair of rotating rolls (diameter: 15 cm, roll rotation speed: 10 m/min, distance between rolls: 20 mm) and compressed in the thickness direction. Was used for defoaming treatment. As a result, 22 types of sealing materials made of rubber foam having an open cell structure were obtained. Table 1 shows the results of the above evaluations of the obtained rubber foams and sealing materials.

Details of the raw materials used in Table 1 are as follows.
EPDM (1): ethylene-propylene-non-conjugated diene copolymer, manufactured by Mitsui Chemicals, Inc., trade name "EPT8030M", non-conjugated diene amount 9.5% by mass.
EPDM (2): ethylene-propylene-non-conjugated diene copolymer, manufactured by Sumitomo Chemical Co., Ltd., trade name "Esprene 501A", non-conjugated diene amount 4.0% by mass
Filler: calcium carbonate, manufactured by Nitto Koka Kogyo Co., Ltd., product name "NS#200"
Process oil: Idemitsu Kosan Co., Ltd., trade name "PW380"
Carbon black (1): Asahi Carbon Co., Ltd., trade name "Asahi #50"
Carbon black (2): Tokai Carbon Co., Ltd., trade name "Shiast 119"
Zinc flower: Activated zinc flower, manufactured by Shodo Kagaku Co., Ltd., trade name "Activated zinc flower AZO"
Stearic acid (1): Product name “Stearic acid 50S” manufactured by Shin Nippon Rika Co., Ltd.
Vulcanization accelerator (1): 2-mercaptobenzothiazole, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "NOXCELLER M"
Vulcanization accelerator (2): N,N'-diethylthiourea, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "NOXCELLER EUR"
Vulcanizing agent: Powdered sulfur Stearic acid (2): Product name “Powdered stearic acid 300” manufactured by Shin Nippon Rika Co., Ltd.
Foaming aid: Urea, manufactured by Wako Pure Chemical Industries, Ltd. Foaming agent: ADCA (azodicarbonamide), manufactured by Sankyo Kasei Co., Ltd. Flame retardant (1): Expanded graphite, manufactured by Sanyo Trading Co., Ltd., product name "SYZR 502FP"
Flame retardant (2): Red phosphorus, manufactured by Nippon Kagaku Kogyo Co., Ltd., trade name "Hishiguard LP-F"
Flame retardant (3): Phosphate ester

In Table 1, Comparative Examples 2 to 6, 13 and 14 were defective in foaming or out of gas, and therefore the apparent density, water stopping property, flame retardancy, compression hardness and average cell diameter were not measured. Further, since Comparative Examples 7 and 9 were out of gas, the water stopping property and the compression hardness were not measured. In Comparative Example 8, similarly, the water stopping property was not measured.

As is clear from Table 1, the rubber foams of Examples 1 to 8 and the sealing materials using the rubber foams were the same as the rubber foams of Comparative Examples 1 to 14 and the sealing materials using the rubber foams. By comparison, it was possible to favorably achieve both waterproofness and flame retardancy.

A rubber foam obtained from the rubber composition for a rubber foam of the present invention is used as a dustproof material, a heat insulating material, a soundproof material, a vibration damping material, a cushioning material, a filling material, a vehicle such as a window dam, an air conditioner, a washing machine. , Electrical equipment such as refrigerators and vending machines; audio equipment; exterior wall joints, sashes, roof material joints, etc.; kitchen equipment, unit baths, water heaters and other housing equipment; structures, joints of roads and bridges, It is preferably used as a sealing material in civil engineering such as waterway joints.

S1: U-shaped sample 2, 3: Acrylic plate

Claims (9)

A rubber composition containing a rubber component containing an ethylene-propylene-non-conjugated diene copolymer, a foaming agent, a flame retardant and a vulcanizing agent, the non-conjugated diene in the ethylene-propylene-non-conjugated diene copolymer. Is 9 to 15% by mass, the content of the foaming agent is 50 parts by mass or less relative to 100 parts by mass of the rubber component, the flame retardant contains expanded graphite and red phosphorus, and the expanded graphite Is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, and the content of the red phosphorus is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and the expanded graphite and the red phosphorus. The total content of the rubber composition is 20 parts by mass or more based on 100 parts by mass of the rubber component. The rubber composition for a rubber foam according to claim 1, wherein the content of the foaming agent is 18 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The rubber foam according to claim 2, wherein a mass ratio of the content of red phosphorus to the content of the foaming agent (content of the red phosphorus/content of the foaming agent) is 0.28 to 0.86. Rubber composition. Content of the said foaming agent is 30-35 mass parts with respect to 100 mass parts of rubber components, and content of the said red phosphorus is 15-30 mass parts with respect to 100 mass parts of rubber components. The rubber composition for a rubber foam according to any one of 3 above. The rubber composition for a rubber foam according to any one of claims 1 to 4, further comprising 10 to 100 parts by mass of a reinforcing material with respect to 100 parts by mass of the rubber component. A rubber foam obtained by foaming the rubber composition for a rubber foam according to claim 1. The rubber foam according to claim 6, wherein the average cell diameter is 20 to 150 as the average number of cells present in an area 1 (inch) ² . The rubber foam according to claim 6 or 7, which has a compression hardness of 0.5 to 150 kPa (measured in accordance with JIS K 6767:1999). A sealing material using the rubber foam according to any one of claims 6 to 8.