JP5231845B2 - Rubber-based resin closed cell foam sheet and method for producing the same - Google Patents

Description

The present invention relates to a method for producing a rubber-based resin closed-cell foamed sheet used as a waterstop / watertight seal material.

  Currently, foam is widely used as a sealing material in various fields such as civil engineering / architecture, 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, and the like, and a rubber foam made of synthetic rubber or natural rubber.

  Among the above-mentioned sealing materials, a water-stop / water-tight sealing material is used to fill a gap between various structures such as buildings, electrical equipment, and vehicles to prevent water from entering. The water-stop / water-tight seal material is arranged on the sealed portion in a compressed state, and is configured to closely contact the interface of the sealed portion without a gap due to repulsive stress that attempts to recover the shape from the compressed state. .

  Here, when the compressibility flexibility of the water-stop / water-tight seal material is low, the repelling stress of the water-stop / water-tight seal material becomes too strong, causing a problem that the sealed portion is deformed. In addition, the gap between the structures is expanded due to the deformation of the sealed portion, and the adhesion (hereinafter referred to as “sealability”) of the waterproof / watertight sealing material to the sealed portion is reduced. There was also a problem of inadequate performance.

  Therefore, an open-cell foam excellent in compression flexibility is used as the waterstop / watertight sealant. However, the open-cell foam has a problem in that it is inferior in water-stopping and water-tightness because the bubbles communicate with each other and water easily permeates through the foam. In addition, when the open-cell foam is water-swelled by contact with water and the sealing performance is improved, the open-cell foam is inferior in sealing performance until it sufficiently absorbs water, and the sealing performance is sufficient. In some cases, water was allowed to permeate before being exhibited.

  In addition, as the water-stop / water-tight seal material, a foam having both closed cells contributing to improvement of water-stop and water-tightness and open cells contributing to improvement of compression flexibility is used, for example, Patent Document 1 describes a fixed sealing material characterized in that a foamed film having both a closed cell and an open cell is made to have a water-swelling property, and the number of cells per 1 cm length is 8 or more. Is disclosed.

  However, the above-mentioned fixed sealing material has a problem in that the rebound stress is reduced by long-term use, so that the sealing performance is lowered and the water stop / water tightness becomes insufficient.

  Therefore, Patent Document 2 discloses a rubber-based resin closed cell foam sheet having a foam structure having closed cells and excellent in interfacial adhesion with a member to be sealed, and a high-performance water- and water-tight seal material using the same. However, there is a demand for higher water and water tightness.

JP-A-9-111899 WO2007 / 072885

The present invention provides a method for producing a rubber-based resin closed-cell foamed sheet that is not easily deteriorated in sealing properties even after long-term use and has excellent water and water tightness.

The method for producing a rubber-based resin closed-cell foamed sheet according to the present invention is obtained by irradiating a foamable resin sheet containing a rubber-based resin containing 33.5 to 50% by weight of an acrylonitrile component and a foaming agent with ionizing radiation. After the crosslinkable resin sheet, the foamable resin sheet is heated and foamed.

As the rubber-based resin, it is necessary to have rubber elasticity at room temperature, and among them, acrylonitrile-butadiene rubber is used.

Shi Lumpur resistance, compression flexibility, from the viewpoint of rubber resin closed cell foam sheet having excellent durability and oil resistance can be obtained, acrylonitrile - butadiene rubber (NBR) is used.

If the content of the acrylonitrile component in the acrylonitrile- butadiene rubber is small, the sealing performance may be lowered when the rubber-based resin closed-cell foamed sheet is used as a water- and water-tight sealing material. It is limited to 35% by weight and is more preferably 35-50% by weight.

  Further, the rubber-based resin may contain a liquid rubber-based resin (hereinafter referred to as “liquid rubber-based resin”) at room temperature. This is because the kneading load of the foamable resin composition described later can be reduced by including a liquid rubber-based resin in the foamable resin composition.

  The liquid rubber-based resin refers to a rubber-based resin having fluidity at room temperature. For example, liquid acrylonitrile-butadiene rubber (liquid NBR), liquid hydrogenated acrylonitrile-butadiene rubber (liquid HNBR), liquid Carboxylated acrylonitrile-butadiene rubber (liquid XNBR), liquid acrylonitrile-butadiene-isoprene rubber (liquid NBIR), liquid acrylonitrile-isoprene rubber (liquid NIR), and functional monomers having acrylonitrile, butadiene and anti-aging functions Liquid acrylonitrile rubbers such as liquid terpolymers; liquid isoprene rubber (liquid IR), etc., and rubber-based resin closed cell foam sheets with excellent sealing properties, compression flexibility, durability and oil resistance. From the point obtained, liquid acryloni Lil rubber are preferable, liquid acrylonitrile - butadiene rubber (liquid NBR) is preferred. In addition, the said liquid rubber-type resin may be used independently, or 2 or more types may be used together.

  The rubber-based resin closed cell foam sheet of the present invention does not need to be all closed cells, and may include open cells in a part of the bubbles, specifically, rubber-based resin closed cell foam. If the closed cell ratio of the sheet is low, the bubbles of the rubber-based resin closed cell foam sheet communicate with each other and water can easily permeate, and the water-stop and water-tightness of the rubber-based resin closed cell foam sheet may decrease. Therefore, 80 to 100% is preferable, and 85 to 100% is more preferable.

In addition, as a method for measuring the closed cell ratio of the rubber-based resin closed cell foam sheet, 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. Subsequently, the weight W ₁ of the test piece is measured, and the thickness of the test piece is further measured to calculate the apparent volume V ₁ of the test piece.

Next, the value obtained as described above is substituted into the following equation (1) to calculate the apparent volume V ₂ occupied by the bubbles. The density of the resin constituting the test piece is ρg / cm ³ .
Apparent volume occupied by bubbles V ₂ = V ₁ −W ₁ / ρ Formula (1)

Subsequently, the test piece is submerged in distilled water at 23 ° C. so that the distance from the upper surface of the test piece to the water surface is 100 mm, and a pressure of 15 kPa is applied to the test piece for 3 minutes. After that, the test piece is taken out from the distilled 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 ratio F ₁ is calculated based on the following formula (2). Thus, the closed cell rate F ₂ is obtained from the open cell rate F ₁ .
Open cell ratio F ₁ (%) = 100 × (W ₂ −W ₁ ) / V ₂ Formula (2)
Closed cell ratio F ₂ (%) = 100−F ₁ Formula (3)

  If the peel strength (hereinafter referred to as “initial peel strength”) of the rubber-based resin closed cell foam sheet immediately after production is low, the sealing property of the rubber-based resin closed cell foam sheet may be insufficient. Therefore, 20 kPa or more is preferable, but if it is too high, it may be difficult to peel off the rubber-based resin closed-cell foamed sheet when it is necessary to perform a re-sticking operation due to a sticking failure or the like. More preferred.

  The initial peel strength of the rubber-based resin closed cell foamed sheet is measured by preparing a rubber-based resin closed cell foamed sheet immediately after preparation having a width of 25 mm, a length of 12.5 mm, and a thickness of 3.0 mm. An acrylic resin plate (width 25 mm × length 100 mm) is laminated on both surfaces of the resin closed cell foam sheet to produce a laminate, and after placing this laminate on a horizontal surface, 500 g of the laminate is placed on the center of the upper surface of the laminate. A test body in which an acrylic resin plate is laminated and integrated on each of both surfaces of a rubber-based resin closed cell foam sheet is prepared by placing a weight and pressing the laminate in the thickness direction for 15 minutes. In accordance with JIS K6850, the peel strength (kPa) when peeled at a tensile speed of 50 mm / min is measured.

  Further, the rubber-based resin closed cell foam sheet may contain an additive. Examples of such additives include flame retardants, antioxidants, fillers, pigments, colorants, fungicides, foaming aids, flame retardant aids, and the like.

  The flame retardant is not particularly limited. For example, in addition to metal hydroxides such as aluminum hydroxide and magnesium hydroxide, brominated flame retardants such as decabromodiphenyl ether, and phosphorus-based flame retardants such as ammonium polyphosphate. A flame retardant etc. are mentioned, Even if it uses independently, 2 or more types may be used together. The flame retardant is commercially available from Albemarle under the trade name “SAYTEX8010”.

  The antioxidant is not particularly limited, and examples thereof include phenol-based antioxidants and sulfur-based antioxidants. Specifically, trade names “IRGANOX 1010” from Ciba Specialty Chemicals are used. And phenolic antioxidants that are commercially available. In addition, an antioxidant may be used independently or 2 or more types may be used together.

  Further, the filler is not particularly limited, and examples thereof include talc, calcium carbonate, bentonite, carbon black, fumed silica, aluminum silicate, acetylene black, aluminum powder, and the like. More than one species may be used in combination.

  Next, the manufacturing method of a rubber-type resin closed cell foam sheet is demonstrated. As a method for producing a rubber-based resin closed-cell foamed sheet, for example, a foamable resin sheet composed of a rubber-based resin containing a nitrile group and a foamable resin composition containing a foaming agent is irradiated with ionizing radiation to obtain foaming properties. A method for producing a rubber-based resin closed-cell foamed sheet in which a foamable resin sheet is heated and foamed after the resin sheet is crosslinked is exemplified.

  In addition, as a method for producing a foamable resin sheet, for example, the above foamable resin composition is kneaded using a kneader such as a Banbury mixer or a pressure kneader, and then continuously by an extruder, calendar, conveyor belt casting, or the like. And a method of producing a foamable resin sheet by kneading in a mechanical manner.

  And as a method of carrying out the crosslinking process of the said foamable resin sheet, it is limited to the crosslinking process by ionizing radiation. This is because, by the crosslinking treatment with ionizing radiation, a uniformly crosslinked foamable resin sheet is obtained, and by foaming the uniformly crosslinked foamable resin sheet, the foam has a small diameter and uniform bubbles. This is because a rubber-based resin closed cell foam sheet can be obtained. Such a rubber-based resin closed cell foam sheet having a uniform bubble with a small diameter has a smooth surface, a large contact area with respect to a portion to be sealed and improved adhesion, and thus has high sealing performance. Excellent water-stop and water-tightness.

  The amount of ionizing radiation applied to the foamable resin sheet during the crosslinking treatment may be appropriately adjusted depending on the properties of the rubber-based resin and the use of the rubber-based resin closed-cell foamed sheet, but is 0.5 to 10 Mrad. Is preferable, and 0.7 to 5.0 Mrad is more preferable.

  The foaming agent contained in the foamable resin composition is not particularly limited. For example, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl) Hydrazide) and the like, and azodicarbonamide is preferable. In addition, the said foaming agent may be used independently, or 2 or more types may be used together.

  And when there is little content of the foaming agent in the said foamable resin composition, while a foamable resin composition does not fully foam, the rubber-type resin closed cell foam sheet of a desired shape may not be obtained. If the amount is too large, abnormal foaming or bubble breakage may occur, making it impossible to obtain a predetermined rubber-based resin closed-cell foamed sheet. Therefore, 1 to 30 parts by weight with respect to 100 parts by weight of the rubber-based resin. preferable.

The rubber-based resin closed-cell foamed sheet of the present invention is characterized by containing acrylonitrile-butadiene rubber containing 33.5 to 50% by weight of an acrylonitrile component. When used as a material, it can be adhered in a tight contact state along the interface of the portion to be sealed. Accordingly, the rubber-based resin closed-cell foamed sheet of the present invention has high sealing properties and can be suitably used as a water / watertight sealing material having excellent water / watertightness.

  In addition, the rubber-based resin closed cell foam sheet of the present invention has the above-described configuration, and thus has excellent compression flexibility. When used as a water- and water-tight seal material, the rubber-based resin closed cell foam sheet is sealed due to its repulsive stress. There is almost no deterioration of the water and water tightness by deforming the part.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
Acrylonitrile-butadiene rubber (NBR, trade name “Nipol 1041” manufactured by Nippon Zeon Co., Ltd., density: 1.00 g / cm ³ , acrylonitrile component amount: 40.5% by weight) 100 parts by weight, azodicarbonamide (product of Otsuka Chemical Co., Ltd.) The name “SO-L”, decomposition temperature: 197 ° C.) and 15 parts by weight of a powdery phenolic antioxidant (trade name “IRGANOX 1010” manufactured by Ciba Specialty Chemicals) 0.1 parts by weight The resin composition was kneaded with a pressure kneader.

  Next, after the foamable resin composition is supplied to an extruder and melt-kneaded, a foamable resin sheet is produced by extruding the molten foamable resin composition from the extruder at an extrusion rate of 50 kg / hour. did.

  Subsequently, the foamable resin sheet was cross-linked by irradiating both surfaces of the foamable resin sheet with 1.2 Mrad of ionizing radiation at an acceleration voltage of 500 keV.

Then, the foamable resin sheet is supplied into a foaming furnace and heated at 240 ° C., thereby foaming the foamable resin sheet, and having an apparent density of 35 kg / m ³ , an independent cell ratio of 93%, and a thickness of 3.0 mm. A resin-based closed cell foam sheet was obtained.

(Example 2)
Acrylonitrile-butadiene rubber (NBR, trade name “Nipol 1042” manufactured by Nippon Zeon Co., Ltd., density: 0.98 g / cm ³ , acrylonitrile component amount: 33.5% by weight) 100 parts by weight, azodicarbonamide (manufactured by Otsuka Chemical Co., Ltd.) A foamable resin comprising 15 parts by weight of a name “SO-L”, decomposition temperature: 197 ° C., and 0.1 parts by weight of a powdery phenolic antioxidant (trade name “IRGANOX 1010” manufactured by Ciba Specialty Chemicals) A rubber-based resin closed cell foam sheet having an apparent density of 36 kg / m ³ , a closed cell ratio of 91%, and a thickness of 3.0 mm was obtained in the same manner as in Example 1 except that the composition was used.

(Comparative Example 1)
Acrylonitrile-butadiene rubber (NBR, trade name “Nipol DN401LL” manufactured by Nippon Zeon Co., Ltd., density: 0.94 g / cm ³ , acrylonitrile component amount: 18.0% by weight) 100 parts by weight, azodicarbonamide (product of Otsuka Chemical Co., Ltd.) A foamable resin comprising 15 parts by weight of a name “SO-L”, decomposition temperature: 197 ° C., and 0.1 parts by weight of a powdery phenolic antioxidant (trade name “IRGANOX 1010” manufactured by Ciba Specialty Chemicals) A rubber-based resin closed cell foam sheet having an apparent density of 35 kg / m ³ , a closed cell ratio of 90%, and a thickness of 3.0 mm was obtained in the same manner as in Example 1 except that the composition was used.

(Comparative Example 2)
100 parts by weight of ethylene-propylene copolymer rubber (EPDM: density 0.87 g / cm ³ ), 15 parts by weight of azodicarbonamide (trade name “SO-L” manufactured by Otsuka Chemical Co., Ltd., decomposition temperature: 197 ° C.) and powder Apparent density in the same manner as in Example 1 except that a foamed resin composition comprising 0.1 part by weight of a phenolic antioxidant (trade name “IRGANOX 1010” manufactured by Ciba Specialty Chemicals) was used. A rubber-based resin closed cell foam sheet having a thickness of 34 kg / m ³ and a thickness of 3.0 mm was obtained.

  The initial peel strength and water stopping property of the obtained rubber-based resin closed cell foam sheet were measured in the following manner, and the results are shown in Table 1.

(Initial peel strength)
The rubber-based resin closed cell foam sheet immediately after being produced is cut out to a width of 25 mm × length of 12.5 mm, and an acrylic resin plate having a width of 25 mm × length of 100 mm is overlapped on both sides of the rubber-based resin closed cell foam sheet. The both sides of the rubber-based resin closed-cell foamed sheet are prepared by placing the laminate on a horizontal plane, placing a weight of 500 g on the center of the top surface of the laminate, and pressing the laminate in the thickness direction for 15 minutes. A test body was prepared in which an acrylic resin plate was laminated and integrated with each of the above.

  Then, the peel strength (kPa) when the rubber-based resin closed cell foam sheet was peeled from the acrylic resin plate was measured for the test specimen immediately after the production in accordance with JIS K6850 at a tensile speed of 50 mm / min.

(Water stop / water tightness)
First, the obtained rubber-based resin closed cell foam sheet was cut into an annular shape (thickness: 3.0 mm) having an outer diameter of 100 mm and an inner diameter of 80 mm to prepare a test piece. Next, this test piece is placed on the center of a flat acrylic resin plate, and on this test piece, a flat acrylic resin plate having a through hole penetrating in the center is formed. A laminate is produced by placing it on the center of a circle, and the laminate is compressed in the thickness direction of the test piece so that the distance between the opposing surfaces of the two acrylic resin plates is 2.55 mm (test piece). A test specimen having a compression ratio of 15% was obtained.

  Subsequently, distilled water was supplied from the through hole of the test body to a space surrounded by the opposing surfaces of the two acrylic resin plates and the test piece, and the space was filled with distilled water. Thereafter, a pressure of 15 kPa was applied from the through hole of the test specimen, and the time from when the pressure started to be applied until the distilled water leaked (water stop / watertight time (minutes)) was measured. In addition, the water stop / watertight time exceeding 120 minutes is described as “no water leak” in Table 1.

Claims (1)

Acrylonitrile containing acrylonitrile component 33.5 to 50 wt% - after crosslinking the foamable resin sheet is irradiated with ionizing radiation to the foamable resin sheet containing butadiene rubber and a foaming agent, the foamable resin sheet A method for producing a rubber-based resin closed-cell foamed sheet characterized by heating and foaming.