JP2009242624A - Sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material having an excellent water-stopping property even under a high pressure or in an environment containing a surfactant.
The sealing material of the present invention is a rubber-based resin closed-cell foamed sheet containing a rubber-based resin and having an apparent density of 20 to 100 kg / m ³ in accordance with JIS K7222, and has a skin layer on at least one surface. And the skin layer has a surface roughness Ra of 100 or less, and therefore has excellent water-stopping properties even under high pressure and in an environment containing a surfactant.
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Description

  The present invention relates to a sealing material that maintains excellent water stoppage.

  Currently, foam is widely used as a sealing material in various fields such as architecture, civil engineering, electricity, electronics, and vehicles. Examples of the foam used for such a sealing material include a thermoplastic resin foam made of polyethylene resin, polypropylene resin, etc., a rubber foam made of synthetic rubber or natural rubber, and the like.

  Recently, high performance products such as a sealing property against water under high water pressure and a sealing property against a surfactant such as a detergent have been demanded. In addition, a material having a repulsive force smaller than the ease of assembly is required, and the flexibility of the material is required, or a sealing material having a low compression rate during use is desired.

  In order to use the sealing material in a state where the compression rate is small, the thickness accuracy of the sealing material is required. In such a case, a polyurethane foam, a rubber foam made of synthetic rubber or natural rubber is often used.

  Patent Document 1 is characterized in that the foam coating is made of a foam structure having both closed cells and open cells, and the bubble film is water-swellable, and the number of bubbles per 1 cm length is 8 or more. A fixed seal material has been proposed.

  However, open-cell foam cannot be used in areas where high-performance sealability is required, and even foams that are exposed to air without a skin layer on the surface are surface active. The agent easily enters and cannot be used.

JP 09-111899 A

  The present invention provides a sealing material having excellent water-stopping properties even under high pressure or in an environment containing a surfactant.

The sealing material of the present invention is a rubber-based resin closed-cell foamed sheet containing a rubber-based resin and having an apparent density of 20 to 100 kg / m ³ in accordance with JIS K7222, having a skin layer on at least one surface; The skin layer has a surface roughness Ra of 100 or less.

  The rubber resin is not particularly limited as long as it has rubber elasticity at room temperature. For example, chloroprene rubber (CR), isoprene rubber (IR), butyl rubber (IIR), nitrile rubber (nitrile) -Butadiene rubber) (NBR), natural rubber, styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), urethane rubber, fluorine rubber, acrylic rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer Polymer rubber, urethane rubber, silicone rubber, etc. are mentioned, and since the cushioning property and durability of the rubber-based resin closed cell foam sheet are excellent, nitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR) ), Butyl rubber (IIR), and chloroprene rubber (CR) are preferred. Nitrile - butadiene rubber (NBR) is preferred. Nitrile-butadiene rubber (NBR) is also called nitrile rubber or acrylonitrile-butadiene copolymer rubber, and styrene-butadiene copolymer rubber (SBR) is also called styrene rubber. Copolymer rubber of butadiene and styrene. It is.

  When the content of the nitrile-butadiene rubber in the rubber-based resin is small, the adhesion to an acrylic plate or a steel plate is lowered and the water-stopping property of the sealing material may be lowered. Therefore, 30% by weight or more is preferable. 50 to 100% by weight is more preferable.

  Since the sealing material of the present invention includes a rubber-based resin closed-cell foamed sheet containing a rubber-based resin, it has excellent repulsive force during compression and exhibits excellent sealing properties. If the closed cell ratio of the rubber-based resin closed cell foamed sheet is small, the water blocking property of the sealing material may be lowered, and therefore 80 to 100% is preferable, and 85 to 100% is more preferable.

Here, the closed cell ratio of the rubber-based resin closed cell foam sheet is measured in the following manner. First, a test piece having a flat square shape with a side of 5 cm and a constant thickness is cut out from the rubber-based resin closed cell foam sheet. Then, the thickness of the test piece is measured to calculate the apparent volume V ₁ of the test piece, and the weight W _{1 of the} test piece is measured.

Next, the apparent volume V ₂ occupied by the bubbles is calculated based on the following formula. The density of the resin constituting the test piece is 1 g / cm ³ .
Apparent volume occupied by bubbles V ₂ = V ₁ −W ₁

Subsequently, the test piece is submerged in distilled water at 23 ° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa is applied to the test piece over 3 minutes. After that, the test piece is taken out of the water, the water adhering to the surface of the test piece is removed, the weight W _{2 of the} test piece is measured, and the open cell rate F ₁ and the closed cell rate F ₂ are calculated based on the following formulas. To do.
Open cell ratio F ₁ (%) = 100 × (W ₂ −W ₁ ) / V ₂
Closed cell ratio F ₂ (%) = 100−F ₁

If the apparent density in accordance with JIS K7222 of the rubber-based resin closed cell foam sheet is small, the rubber-based resin closed cell foam sheet becomes brittle and the strength cannot be maintained, and the water-stopping property is maintained for a long period of time. On the other hand, if it is large, the rubber-based resin closed cell foam sheet becomes hard and the compression flexibility is lowered or the repulsive force at the time of compression is increased, the sealed member is deformed, and the sealed member is deformed by the deformation of the sealed member. The gap is enlarged and the sealing performance is lowered, so that it is limited to 20 to 100 kg / m ³ .

Furthermore, the rubber-based resin closed-cell foamed sheet has a skin layer on at least one surface, and the surface roughness Ra of this skin layer is limited to 100 μm or less, preferably 80 μm or less. As described above, since the surface roughness Ra of the skin layer is 100 μm or less, the surface property is excellent and the adhesiveness to the member to be sealed is excellent, and the sealing material of the present invention exhibits excellent water blocking properties. The skin layer refers to a layer having a density of 0.9 g / cm ³ or more that does not have a cell cross section on its surface.

  The surface roughness Ra of the skin layer of the rubber-based resin closed cell foam sheet is measured in the following manner. The surface roughness of the skin layer of the rubber-based resin closed cell foam sheet may be taken as data using a non-contact type laser microscope and the surface roughness may be calculated in accordance with JIS B0601.

  The surface roughness Ra of the skin layer of the rubber-based resin closed cell foam sheet is, for example, a VK shape analysis device commercially available from Keyence Corporation, a laser microscope with a trade name of “VK-8500”, and analysis software thereof. (Trade name “VK-PC”) can be used in the following procedure.

  First, a test piece is cut out from the rubber-based resin closed cell foam sheet, and this test piece is arranged and fixed on a smooth metal plate. Focus on the skin layer of the specimen. Note that the measurement range is larger than a square having a side of 2 mm.

  Next, after setting the upper and lower limits of the laser beam, the skin layer of the test piece is irradiated with the laser beam, and the surface height of the skin layer is scanned with the laser. Then, the image data is taken into analysis software, and the surface roughness Ra of the skin layer may be analyzed according to JIS B0601.

  Next, the manufacturing procedure of the sealing material will be described. As a method for producing a rubber-based resin closed cell foam sheet, a cooling member having a cooling surface having a surface roughness Ra of 5 μm or less is prepared, and the cooling surface of this cooling member is a By pressing the surface and rapidly cooling the surface of the rubber-based resin closed cell foam sheet, a rubber-based resin closed cell foam sheet having a skin layer with a surface roughness Ra of 100 μm or less can be obtained. In addition, since the measuring method of surface roughness Ra of the cooling surface of a cooling member is the same as the measuring method of surface roughness Ra of the skin layer mentioned above, the description is abbreviate | omitted.

  And as a cooling member, it is not specifically limited, The metal roll which made the surface whose surface roughness Ra is 5 micrometers or less a cooling surface, the cooling roll which used the surrounding surface whose surface roughness Ra is 5 micrometers or less as a cooling surface, etc. Is mentioned.

  When the temperature of the cooling surface of the cooling member is low, the shrinkage of the foamed sheet is large and easily fluctuates, so the thickness accuracy of the foamed sheet may be reduced, and when the temperature is high, the surface roughness Ra of the skin layer is increased. Therefore, 0 to 40 ° C is preferable, and 10 to 20 ° C is more preferable.

  In addition, the point which foams and manufactures a rubber-type resin closed cell foam sheet uses a conventionally well-known method, for example, a filler etc. are added to a rubber-type resin, a crosslinking agent, and a thermal decomposition type foaming agent as needed. The foamable raw material composition added is kneaded with a kneader such as a Banbury mixer or a pressure kneader as necessary, and then continuously kneaded with a calendar, an extruder, a conveyor belt casting or the like to obtain a foamable sheet. A method for producing a rubber-based resin closed-cell foamed sheet by heating and crosslinking this uncrosslinked foamable sheet while heating or after crosslinking, a rubber-based resin and a thermally decomposable foaming agent, if necessary. The foamable raw material composition to which fillers and the like are added is kneaded by a kneader such as a Banbury mixer or a pressure kneader as necessary, and then calendered, extruder, conveyor belt caster. A foamable sheet is produced by continuously kneading with foaming, etc., and the foamable sheet is irradiated with ionizing radiation to crosslink the foamable sheet. Examples include a method for producing a foamed foam sheet.

  As said crosslinking agent, an organic peroxide, sulfur, a sulfur compound etc. are mentioned, for example, An organic peroxide is preferable. Examples of ionizing radiation include light, γ-rays, and electron beams. Examples of the organic peroxide include diisopropylbenzene hydroperoxide, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, t-butyl perbenzoate, cumyl hydroperoxide, t-butyl hydroperoxide, 1, 1-di (t-butylperoxy) -3,3,5-trimethylhexane, n-butyl-4,4-di (t-butylperoxy) valerate, α, α′-bis (t-butylperoxy) Isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, t-butylperoxycumene and the like. Examples of the sulfur compound include tetramethylthiuram disulfide, Tetramethylthiuram monosulfide, zinc dimethyldithiocarbamate, 2-mercapto Examples include benzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, sulfur monochloride, sulfur dichloride and the like.

  Further, if the content of the crosslinking agent in the foamable raw material composition is small, the gel fraction (crosslinking degree) of the foamable raw material composition does not become suitable for foaming and bubbles are broken. While a resin foam sheet may not be obtained, on the other hand, if the amount is too high, the gel fraction (crosslinking degree) of the foamable raw material composition is excessively increased and the foamable raw material composition may not be foamed. 0.05-10 weight part is preferable with respect to weight part, and 0.1-7 weight part is more preferable.

  The pyrolytic foaming agent refers to those that decompose by heating to generate foaming gas. Such pyrolytic foaming agent is not particularly limited, and examples thereof include azodicarbonamide, benzenesulfonylhydrazide, and dinitroso. Examples include pentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide), and the like. These thermal decomposition type foaming agents may be used independently and 2 or more types may be used together. As for the compounding quantity of the thermal decomposition type foaming agent in the said foamable raw material composition, 1-30 weight part is preferable with respect to 100 weight part of rubber-type resins.

  If the content of the thermally decomposable foaming agent in the foamable raw material composition is small, the foaming ratio of the rubber-based resin foamed sheet does not increase and the apparent density increases, and the repulsive force of the rubber-based resin foamed sheet is high. On the other hand, if it is large, the apparent density of the rubber-based resin foam sheet will be low, the compression set will be large, the shape recoverability of the rubber-based resin closed cell foam sheet will be reduced, and it will stop for a long time. Since it may not be possible to maintain aqueous properties, 3 to 25 parts by weight is preferable and 5 to 20 parts by weight is more preferable with respect to 100 parts by weight of the rubber-based resin.

  Moreover, what is necessary is just to adjust suitably according to the characteristic of rubber-type resin as an irradiation amount of ionizing radiation, 0.5-10 Mrad is preferable and 0.7-5.0 Mrad is more preferable.

The sealing material of the present invention is a rubber-based resin closed-cell foamed sheet containing a rubber-based resin and having an apparent density of 20 to 100 kg / m ³ in accordance with JIS K7222, having a skin layer on at least one surface; Since the skin layer has a surface roughness Ra of 100 or less, the skin layer has excellent water-stopping property even under high pressure and in an environment containing a surfactant.

Example 1
100 parts by weight of acrylonitrile-butadiene rubber (NBR, density: 960 kg / m ³ ), 13 parts by weight of azodicarbonamide (trade name “SO-L” manufactured by Otsuka Chemical Co., Ltd.) and a phenolic antioxidant (trade name “manufactured by Adekastab Co., Ltd.) Adeka Stub AO-60 ") 0.5 parts by weight was supplied to an extruder, melted and kneaded and extruded from the extruder to obtain a foamable rubber-based resin sheet having a thickness of 1.7 mm.

  The foamable rubber-based resin sheet was crosslinked by irradiating the resulting foamable rubber-based resin sheet with 1.8 Mrad of an electron beam at an acceleration voltage of 500 keV. Thereafter, the foamable rubber-based resin sheet was supplied into a foaming furnace and heated to 240 ° C. to foam the foamable rubber-based resin sheet to produce a rubber-based resin closed-cell foamed sheet.

On the other hand, a pair of cooling mirror plates was prepared with the surface being chrome plated and having a surface roughness Ra of 0.05 μm as the cooling surface. The surface of the rubber-based resin closed cell foam sheet having a thickness of 4.2 mm immediately after foaming was maintained at 15 ° C. so that the cooling surface of the pair of cooling mirror plates was on the rubber-based resin closed cell foam sheet side. A sealing material made of a rubber-based resin closed cell foam sheet having an apparent density of 66 kg / m ³ and a thickness of 4 mm was obtained by being sandwiched between a pair of cooling mirror plates and rapidly cooled for 5 minutes.

  Skin layers were formed on both surfaces of the rubber-based resin closed cell foam sheet constituting the sealing material, and the surface roughness Ra of these skin layers was 45 μm.

(Example 2)
100 parts by weight of acrylonitrile-butadiene rubber (NBR, density: 960 kg / m ³ ), 15 parts by weight of azodicarbonamide (trade name “SO-L” manufactured by Otsuka Chemical Co., Ltd.) and a phenolic antioxidant (trade name “manufactured by Adekastab Co., Ltd.) Adeka Stub AO-60 ") 0.5 parts by weight was supplied to an extruder, melt-kneaded, and extruded from the extruder to obtain a foamable rubber-based resin sheet having a thickness of 1.6 mm.

  The foamable rubber-based resin sheet was crosslinked by irradiating the resulting foamable rubber-based resin sheet with 1.8 Mrad of an electron beam at an acceleration voltage of 500 keV. Thereafter, the foamable rubber-based resin sheet was supplied into a foaming furnace and heated to 240 ° C. to foam the foamable rubber-based resin sheet to produce a rubber-based resin closed-cell foamed sheet.

On the other hand, a cooling roll having a peripheral surface with a surface roughness Ra of 0.05 μm and a peripheral surface as a cooling surface was prepared. The surface of the rubber-based resin closed cell foam sheet immediately after foaming is rapidly cooled on the surface of the rubber-based resin closed cell foam sheet by rolling a cooling roll whose surface temperature is maintained at 17 ° C., and the apparent density is 50 kg. A sealing material made of a rubber-based resin closed cell foam sheet having a thickness of 4 mm / m ³ was obtained.

  Skin layers were formed on one surface of the rubber-based resin closed-cell foamed sheet constituting the sealing material, and the surface roughness Ra of these skin layers was 75 μm.

(Comparative Example 1)
A rubber-based resin closed cell with an apparent density of 66 kg / m ³ and a thickness of 4 mm, in the same manner as in Example 1, except that the rubber-based resin closed cell foam sheet immediately after foaming was not cooled by the cooling mirror plate. A sealing material made of a foam sheet was obtained. Skin layers were formed on one surface of the rubber-based resin closed cell foam sheet constituting the sealing material, and the surface roughness Ra of these skin layers was 120 μm.

(Comparative Example 2)
A foamed sheet made of ethylene-propylene-diene-methylene rubber (EPDM) having no skin layer on its surface (trade name “E-4088”, apparent density: 133 kg / m ³ , thickness: 4 mm, manufactured by INOAC) Used as a sealing material. The surface roughness Ra of the foamed sheet was 45 μm.

(Comparative Example 3)
A polyurethane open cell foam sheet (trade name “HP” manufactured by NHK Spring Co., Ltd., apparent density: 40 kg / m ³ , thickness: 4 mm, closed cell ratio: 3%) was used as a sealing material. The surface roughness Ra of the polyurethane open-cell foamed sheet was 35 μm.

  The closed cell ratio of the obtained sealing material was measured in the above-described manner, and the water blocking property was measured in the following manner, and the results are shown in Table 1.

(Waterproof)
After sticking a double-sided adhesive tape on the entire surface of the thermoplastic resin foam sheet of the sealing material, a test piece is obtained by punching from the sealing material into a ring shape having an outer diameter of 60 mm and an inner diameter of 40 mm over the entire thickness of the sealing material. It was. In the sealing materials of Comparative Examples 2 and 3, a double-sided adhesive tape was affixed to any one surface.

  The test piece is sandwiched between two parallel acrylic resin plates so that the compression rate of the test piece is 25%, that is, the thickness after compression of the test piece is 25% of the thickness before compression. The test piece was compressed with two acrylic resin plates in the thickness direction.

  One acrylic resin plate of the two acrylic resin plates has a through hole for water filling and pressure application in a portion corresponding to the center portion of the test piece. From this through hole, Fill the space surrounded by the facing surfaces of the two acrylic resin plates and the test piece with tap water, and then apply a 5 kPa pressure at 23 ° C. for 1 hour to conduct a water leak test and perform water leak test. The presence or absence was visually observed. If a leak is found even with a single drop, “×” is indicated in the column of “Tap water (5 kPa)” in Table 1 as “No” indicating no leakage, and “No” is indicated as no leakage if no leakage is found. did. In the case where water leakage occurred, the elapsed time from when the pressure of 5 kPa was applied until the water leakage started is shown in Table 1.

  Furthermore, it is the same as in the case of the above tap water except that a commercially available car cleaning liquid detergent diluted 10 times is used instead of tap water, and the pressure is set to 1 kPa instead of 5 kPa. The water leakage test was conducted in the manner described above, and the presence or absence of water leakage was visually observed, and evaluated according to the same criteria, and listed in the column of “Surfactant (1 kPa)” in Table 1. When water leakage occurred, the elapsed time from application of a pressure of 1 kPa to the start of water leakage is shown in Table 1.

Claims (2)

A rubber-based resin closed-cell foamed sheet containing a rubber-based resin and having an apparent density of 20 to 100 kg / m ³ according to JIS K7222, having a skin layer on at least one surface, and the surface roughness of the skin layer Ra is 100 micrometers or less, The sealing material characterized by the above-mentioned. The sealing material according to claim 1, wherein the rubber-based resin contains 30% by weight or more of nitrile-butadiene rubber.