Rubber and waterproofing materials

Abstract

To provide water expansible rubber having a large initial water expansion rate.SOLUTION: Rubber 1 contains a rubber component, an ionic water absorption resin, and a nonionic surface active agent that is a polypropylene oxide / ethylene oxide copolymer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to rubber and waterstop materials. [Background technology]

[0002] Patent Document 1 discloses a water-swellable rubber that contains a polyalkylene oxide modified product as a nonionic water-absorbent resin and an ethylene oxide / propylene oxide copolymer as a nonionic surfactant.

[0003] Patent Document 2 discloses a water-swellable rubber that contains a vinyl alcohol-acrylic acid ester copolymer as a highly water-absorbent resin and any one of polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyethylene glycol monostearate, and polyoxyethylene lauryl ether as a surfactant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-194823 A [Patent Document 2] Japanese Patent Application Publication No. 60-258237 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional water-swellable rubber has a problem in that the initial water-swelling rate is low even up to 10 days after the rubber is immersed in water.

[0006] The present disclosure has an object to provide a water-swellable rubber having a large initial water-swelling rate. The present disclosure can be realized in the following aspects. [Means for solving the problem]

[0007] A rubber component, An ionic water-absorbing resin; A rubber comprising a nonionic surfactant which is a polypropylene oxide / ethylene oxide copolymer. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a water-swellable rubber having a large initial water swelling rate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram for explaining a usage mode of the rubber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Here, a preferred example of the present disclosure is given. The nonionic surfactant is a rubber in which the molecular weight of the polypropylene oxide portion in a polypropylene oxide / ethylene oxide copolymer is 700 or more and 4,000 or less. The nonionic surfactant contains 5 mol % or more and 85 mol % or less of ethylene oxide units, when the total of propylene oxide units and ethylene oxide units is 100 mol %. The ionic water-absorbing resin is a rubber that is a resin containing a structural unit derived from a (meth)acrylic acid monomer. -Water-stopping material comprising the above-mentioned rubber.

[0011] The present disclosure will be described in detail below. In this specification, when a numerical range is described using "-", the range includes the lower limit and the upper limit unless otherwise specified. For example, the description "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less".

[0012] 1. Rubber 1 The rubber 1 of the present embodiment contains a rubber component, an ionic water-absorbing resin, and a nonionic surfactant which is a polypropylene oxide / ethylene oxide copolymer.

[0013] (1) Composition The rubber 1 can be obtained from a composition containing, for example, an uncrosslinked rubber component, an ionic water-absorbing resin, and the above-mentioned nonionic surfactant. When the rubber 1 is a crosslinked (vulcanized) rubber, the composition may further contain a crosslinking agent (vulcanizing agent), a crosslinking accelerator (vulcanization accelerator), a crosslinking acceleration assistant (vulcanization acceleration assistant), etc., in addition to the crosslinkable rubber component. Each component of the composition will be described.

[0014] (1.1) Rubber component The rubber component is not particularly limited. The rubber component is preferably at least one selected from the group consisting of ethylene-propylene-diene rubber (EPDM), polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, fluororubber, silicon rubber, urethane rubber, polysulfide rubber, acrylic rubber, butyl rubber, epichlorohydrin rubber, and natural rubber. Among these, the rubber component is more preferably EPDM.

[0015] EPDM is a rubber obtained by copolymerization of ethylene, propylene, and dienes. EPDM is made possible to vulcanize with a vulcanizing agent by further copolymerizing dienes with an ethylene-propylene copolymer to introduce unsaturated bonds. The dienes are not particularly limited, but non-conjugated dienes are preferred, such as 5-ethylidene-2-norbornene, 1,4-hexadiene, and dicyclopentadiene. From the viewpoint of obtaining the characteristics of the present disclosure, 5-ethylidene-2-norbornene is preferred as the diene. The content of dienes in EPDM (diene content) is not particularly limited. From the viewpoints of crosslinking (vulcanization) reaction and mechanical properties, the content of dienes is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 10% by mass or less. The ethylene content in EPDM is not particularly limited, but from the viewpoint of rubber strength, the ethylene content is preferably from 40% by mass to 80% by mass, and more preferably from 50% by mass to 70% by mass. The EPDM may be used alone or in combination of two or more kinds.

[0016] As the EPDM, it is preferable to use a high molecular weight EPDM from the viewpoint of improving the strength of the rubber. When using a high molecular weight EPDM, it is preferable to use an oil-extended EPDM from the viewpoint of kneadability. As the high molecular weight EPDM, for example, a Mooney viscosity ML 1+4 EPDM with a hardness of 40 or more and 100 or less (100℃) can be used. As the oil-extended EPDM, various oil-extended EPDMs can be used, which are obtained by extending the raw EPDM with any extender oil at any ratio. Examples of the extender oil include paraffin-based oil. The amount of the extender oil is not particularly limited, but is preferably 70 parts by mass or more and 150 parts by mass or less per 100 parts by mass of EPDM. In this specification, Mooney viscosity is the viscosity ML measured according to JIS K6300-1-2013 using an L-shaped rotor, with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100°C. 1+4 (100℃). For commercially available products, the catalog value may be used.

[0017] As the EPDM, the above-mentioned high molecular weight EPDM (also referred to as EPDM-1) may be used in combination with an EPDM having a lower molecular weight than the high molecular weight EPDM (also referred to as EPDM-2). As the EPDM-2, for example, a Mooney viscosity ML 1+4 It is possible to use EPDM having a thermal expansion coefficient (100° C.) of 20 to 100. The blending ratio of EPDM-1 to EPDM-2 (EPDM-1 / EPDM-2) is preferably 10 / 90-100 / 0 (mass ratio), and more preferably 25 / 75-75 / 25 (mass ratio).

[0018] (1.2) Ionic water-absorbing resin The ionic water-absorbing resin is a polymer having a three-dimensional network structure and a property of swelling by absorbing water into the resin. From the viewpoint of water absorption, the ionic water-absorbing resin is preferably a resin containing a structural unit derived from a (meth)acrylic acid monomer. Examples of the (meth)acrylic acid monomer include acrylic acid, alkali metal salts or ammonium salts of acrylic acid, methacrylic acid, and alkali metal salts or ammonium salts of methacrylic acid. One or more monomers may be selected from these. Examples of the resin containing a structural unit derived from a (meth)acrylic acid monomer include polyacrylate resins, sulfoalkyl acrylate-acrylic acid copolymer crosslinked products, and the like. Specific examples of the ionic water-absorbing resin include "Sunfresh" (manufactured by Sanyo Chemical Industries, Ltd.), "Aqualic CA" (manufactured by Nippon Shokubai Co., Ltd.), and salt-resistant "Aqualic CS" (manufactured by Nippon Shokubai Co., Ltd.). The ionic water-absorbing resin may be used alone or in combination of two or more kinds.

[0019] The water absorption ratio of the ionic water absorbent resin is not particularly limited. The water absorption ratio of the ionic water absorbent resin to deionized water is preferably 10 times or more, more preferably 50 times or more, and even more preferably 100 times or more. The water absorption ratio of the ionic water absorbent resin to deionized water may be, for example, 1000 times or less, 600 times or less, or 200 times or less. The water absorption ratio of the ionic water absorbent resin to artificial seawater (3.5% sodium chloride aqueous solution) is preferably 10 times or more, more preferably 15 times or more, and even more preferably 20 times or more. The water absorption ratio of the ionic water absorbent resin to artificial seawater may be, for example, 100 times or less, 60 times or less, or 30 times or less. The water absorption ratio of the ionic water absorbent resin can be measured, for example, in accordance with JIS K7223. The average particle diameter of the ionic water-absorbing resin is not particularly limited, and is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 100 μm or less.

[0020] The content of the ionic water-absorbing resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 40 parts by mass or more, or 80 parts by mass or more, when the total rubber component is 100 parts by mass, from the viewpoint of improving the water expansion ratio of the rubber 1. The content of the ionic water-absorbing resin is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, or 110 parts by mass or less, from the viewpoint of moldability of the rubber 1. From these viewpoints, the content of the ionic water-absorbing resin is preferably 5 parts by mass or more and 200 parts by mass or less, more preferably 10 parts by mass or more and 150 parts by mass or less, and even more preferably 40 parts by mass or more and 130 parts by mass or less, or 80 parts by mass or more and 110 parts by mass or less.

[0021] (1.3) Nonionic surfactants As the nonionic surfactant, a polypropylene oxide / ethylene oxide copolymer is used. As the polypropylene oxide / ethylene oxide copolymer, for example, a copolymer containing propylene oxide units and ethylene oxide units represented by the following formula (I) is suitable. The copolymer represented by formula (I) can be obtained, for example, as an adduct of ethylene oxide added to polypropylene glycol. The polypropylene oxide portion (portion composed of propylene oxide units) has the properties of a hydrophobic group. The ethylene oxide portion (portion composed of ethylene oxide units) has the properties of a hydrophilic group. [ka] (In formula (I), a, b, and c represent integers.)

[0022] Here, b represents the average number of moles of propylene oxide units added. b is, for example, a number from 12 to 80. a+c represents the average number of moles of ethylene oxide units added. a+c is, for example, a number not greater than 300, preferably a number from 2 to 100. The weight average molecular weight of the nonionic surfactant is, for example, 1,000 or more and 18,000 or less.

[0023] Specific examples of nonionic surfactants include "ADEKA PLURONIC L" or "ADEKA PLURONIC F" (manufactured by ADEKA CORPORATION), "EPAN" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Pluronic" (manufactured by BASF Japan Ltd.), "Newpol PE" (manufactured by Sanyo Chemical Industries, Ltd.), and "Pronon" (manufactured by NOF Corporation). The nonionic surfactant may be used alone or in combination of two or more kinds.

[0024] The molecular weight of the polypropylene oxide portion in the polypropylene oxide / ethylene oxide copolymer is not particularly limited. From the viewpoint of improving the initial water swelling rate, the molecular weight of the polypropylene oxide portion is preferably 700 or more, more preferably 900 or more, even more preferably 1250 or more, even more preferably 1500 or more, and even more preferably 2000 or more. From the viewpoint of easy availability, the molecular weight of the polypropylene oxide portion is preferably 4000 or less, more preferably 3500 or less, and even more preferably 3300 or less. From these viewpoints, the molecular weight of the polypropylene oxide portion is preferably 700 or more and 4000 or less, more preferably 1250 or more and 3300 or less, and can be within a range that appropriately combines the above lower limit and upper limit.

[0025] The content of the propylene oxide unit and the ethylene oxide unit is not particularly limited. When the total of the propylene oxide unit and the ethylene oxide unit is 100 mol%, the content of the ethylene oxide unit is preferably 5 mol% or more, more preferably 10 mol% or more, from the viewpoint of ensuring hydrophilicity. The content of the ethylene oxide unit is preferably 85 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less, 50 mol% or less, 40 mol% or less, or 35 mol% or less, from the viewpoint of improving the initial water expansion rate. From these viewpoints, the content of the ethylene oxide unit is preferably 5 mol% or more and 85 mol% or less, more preferably 5 mol% or more and 75 mol% or less, and can be a range that appropriately combines the above lower limit and upper limit.

[0026] The content of the nonionic surfactant is more than 0 parts by mass, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more, when the total rubber component is taken as 100 parts by mass, from the viewpoint of improving the initial water expansion rate. The content of the nonionic surfactant is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and 10 parts by mass or less, from the viewpoint of moldability. From these viewpoints, the content of the nonionic surfactant is preferably more than 0 parts by mass, 50 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, even more preferably 1 part by mass or more and 20 parts by mass or less, and 3 parts by mass or more and 10 parts by mass or less.

[0027] (1.4) Crosslinking agents, crosslinking accelerators, and crosslinking accelerator assistants The crosslinking agent is not particularly limited. For example, known crosslinking agents such as sulfur, sulfur compounds, selenium, magnesium oxide, peroxide-based crosslinking agents, and p-quinone dioxime-based crosslinking agents can be used. The crosslinking agent may be used alone or in combination of two or more. The amount of the crosslinking agent is preferably 0.5 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the rubber components.

[0028] Examples of the crosslinking accelerator include benzothiazyl disulfide, 2-mercaptobenzothiazole, dipentamethylene thiraum tetrasulfide, tetramethylthiraum disulfide, etc. The total amount of the crosslinking accelerator is preferably, for example, 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the rubber components in total. Examples of the crosslinking promoter include zinc oxide, stearic acid, etc. The total amount of the crosslinking promoter is preferably, for example, 2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber components in total.

[0029] (1.5) Other ingredients In addition to the above components, the composition may further contain additives such as softeners, fillers, processing aids, and the like.

[0030] Examples of the softener include mineral oils such as paraffinic, naphthenic and aromatic oils, and vegetable oils such as lauric acid, ricinoleic acid, baltimic acid, cottonseed oil, soybean oil, castor oil and palm oil. The amount of the softener is preferably 70 parts by mass or more and 130 parts by mass or less per 100 parts by mass of the total rubber components.

[0031] Examples of the filler include inorganic fillers such as carbon black, clay, calcium carbonate, talc, magnesium hydroxide, mica, aluminum hydroxide, barium sulfate, silicic acid, titanium oxide, bentonite, mica, glass fiber, wood flour, etc. The amount of the filler is preferably 50 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the total rubber components. The processing aid may be a mixture of a fatty acid ester and an inorganic filler, etc. The amount of the processing aid is preferably 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total rubber components.

[0032] (1.6) Manufacturing method of rubber 1 There is no particular limitation on the manufacturing method of the rubber 1. The rubber 1 can be manufactured by kneading raw materials such as a rubber component, an ionic water-absorbing resin, and a nonionic surfactant with a twin-screw kneader such as a mixer, and molding the mixture with a molding machine.

[0033] 2. Properties and uses of rubber 1 The rubber 1 may be a crosslinked rubber or a non-crosslinked rubber. From the viewpoint of mechanical properties, the rubber 1 is preferably a crosslinked rubber. The rubber 1 may be a non-foamed rubber or a foamed rubber. From the viewpoint of water stopping properties, the rubber 1 is preferably a non-foamed rubber.

[0034] (1) Water expansion ratio There is no particular limitation on the water expansion ratio of the rubber 1. When calculated by the following test method, the water expansion ratio of the rubber 1 is preferably 1.5 times or more, more preferably 2.6 times or more, 3 times or more, 4 times or more, 5 times or more, 6 times or more, 7 times or more, or 8 times or more. There is no particular limitation on the upper limit of the water expansion ratio of the rubber 1, but it is usually 20 times or less, and may be 10 times or less. <Measurement method> Prepare a 30mm x 30mm x 2mm test piece from rubber 1 before it comes into contact with water (unexpanded). Immerse the test piece in tap water at room temperature (23°C) for 10 days. Measure the volume of the test piece after immersion and calculate the water expansion ratio according to the following formula. Water expansion ratio [times] = (volume of test piece after immersion) / (volume of test piece before immersion)

[0035] (2) Hardness There is no particular limitation on the hardness of the rubber 1. The hardness of the rubber 1 measured using a type A durometer based on JIS K6253 is preferably 35 or more and 70 or less, and more preferably 40 or more and 60 or less. The hardness of the rubber 1 is measured on the unexpanded rubber 1.

[0036] (3) Tensile strength The tensile strength of the rubber 1 is not particularly limited. The tensile strength of the rubber 1 measured based on JIS K6251 is preferably 0.9 MPa or more, more preferably 2.5 MPa or more, and further preferably 5 MPa or more. The upper limit of the tensile strength of the rubber 1 is not particularly limited. The tensile strength of the rubber 1 is measured on the unexpanded rubber 1.

[0037] (4) Elongation The elongation of the rubber 1 is not particularly limited. The elongation of the rubber 1 measured based on JIS K6251 is preferably 300% or more, more preferably 500% or more, and even more preferably 600% or more. The upper limit of the elongation of the rubber 1 is not particularly limited, but is usually 3000% or less. The elongation of the rubber 1 is measured on the unexpanded rubber 1.

[0038] (5) Density The density of the rubber 1 is not particularly limited. The density of the rubber 1 measured based on JIS K6268 is preferably 0.8 Mg / m 3 More than 1.8Mg / m 3 More preferably, it is 1.0 Mg / m or less. 3 More than 1.6Mg / m 3 The density of rubber 1 is measured using unexpanded rubber 1.

[0039] (6)Applications The use of the rubber 1 is not particularly limited. The rubber 1 is suitable as a water-stopping material because of its large initial water expansion rate. Specifically, the rubber 1 can be used for a wide range of applications, such as a civil engineering water-stopping material for a segment joint for a shield construction method, a building water-stopping material for a concrete joint, a manhole water-stopping material for a pipe such as a sewer pipe, a communication cable water-stopping material, a dew condensation prevention water-stopping material, and a water-shielding mat. The rubber 1 may also be used as a water-stopping material for secondary water-stopping in combination with a sealing material for primary water-stopping in a joint or the like. The rubber 1 is used as a water-stopping material for secondary water-stopping to ensure long-term water-stopping. The rubber 1 contains an ionic water-absorbing resin, and is therefore particularly effective as a water-stopping material for stopping a solution with a low ion concentration such as fresh water.

[0040] The shape of the rubber 1 is not particularly limited. The shape of the rubber 1 may be prismatic, cylindrical, tubular, annular, or sheet-like, depending on the application. FIG. 1 shows a cross-sectional view of the prismatic rubber 1. The rubber 1 is used as a water-stopping material that stops water from entering between the member 3 and the member 4. The left side of FIG. 1 shows the rubber 1 that is not yet expanded. The right side of FIG. 1 shows the rubber 1 that has absorbed water and expanded, and the arrows show water seeping in from the outside. When the gap between the member 3 and the member 4 becomes large, the rubber 1 expands with water and immediately fills the gap, thereby ensuring water-stopping between the member 3 and the member 4.

[0041] 3. Effects of this embodiment According to this embodiment, it is possible to provide a water-swelling rubber 1 having a high initial water swelling rate. Ionic water-absorbing resins generally have a higher water absorption ratio than nonionic water-absorbing resins, and can contribute to improving the initial water swelling rate of the rubber 1. On the other hand, since the rubber component has poor water permeability, the time required for water to penetrate to the ionic water-absorbing resin present inside the rubber 1 becomes an issue in improving the initial water swelling rate. The inventors of the present application have found that the initial water swelling rate can be improved by blending a nonionic surfactant that is a polypropylene oxide / ethylene oxide copolymer with the rubber component and the ionic water-absorbing resin, and have developed the rubber 1 of the present disclosure.

[0042] The reason why the initial water swelling rate of the rubber 1 can be improved is presumed to be as follows: However, the present disclosure is not to be construed in any way as being limited by this presumed reason. It is believed that the polypropylene oxide / ethylene oxide copolymer exists at the interface between the rubber component and the ionic water-absorbing resin, with the hydrophobic polypropylene oxide portion on the rubber component side and the hydrophilic ethylene oxide portion on the ionic water-absorbing resin side. In other words, it is believed that a water path is formed around the rubber component by the ethylene oxide portion connected to the ionic water-absorbing resin. The water attached to the surface of the rubber 1 penetrates through this water path by the ethylene oxide portion, and the time required for the water to penetrate to the ionic water-absorbing resin present inside the rubber 1 can be shortened. In this way, it is believed that the initial water expansion speed can be improved.

[0043] In the case of polypropylene oxide / ethylene oxide copolymer, the molecular weight of the polypropylene oxide portion and the content of ethylene oxide units can be easily adjusted depending on the number of propylene oxide units and ethylene oxide units, and therefore, compared to other surfactants, the polypropylene oxide / ethylene oxide copolymer is useful in improving the initial water swelling rate by appropriately designing the molecular weight of the hydrophobic group and the content of the hydrophilic group. For example, when the molecular weight of the polypropylene oxide portion is 700 or more and 4,000 or less, the initial water swelling speed can be further increased. Here, it is expected that the higher the content of ethylene oxide units, the more sufficient the water path to the ionic water absorbent resin can be secured, and the higher the initial water swelling speed can be. However, contrary to this expectation, when the content of ethylene oxide units is 5 mol % or more and 85 mol % or less, the initial water swelling speed can be further increased. Furthermore, when the rubber component is EPDM, there is a possibility that the initial water swelling rate can be improved due to the high affinity between the polypropylene oxide portion and the rubber component. EXAMPLES

[0044] The present invention will be described more specifically below with reference to examples.

[0045] 1. Preparation of rubber (Experimental Example 1-9) The rubbers of Experimental Examples 1-9 were produced with the compounding ratios shown in Table 1. Experimental Examples 1-7 and 9 are working examples, and Experimental Example 8 is a comparative example. In Table 1, when an "*" is added, such as "8*", it indicates that it is a comparative example. Details of the main raw materials listed in Table 1 are shown below. EPDM-1: Oil-extended EPDM, Sumitomo Chemical's Esprene 600F, rubber content 50 parts by mass, oil content 50 parts by mass, Mooney viscosity ML 1+4 (100°C) 63, diene content 4.0% by mass, ethylene content 66% by mass EPDM-2: Non-oil extended EPDM, Mitsui Chemicals Mitsui EPT3045, Mooney viscosity ML 1+4(100°C) 40, diene content 4.7% by mass, ethylene content 56% by mass Ionic water absorbent resin: Acrylic acid polymer partially cross-linked with sodium salt, Sanyo Chemical Industries, Sanfresh ST-500MPSA Surfactant-1: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, Daiichi Kogyo Seiyaku Eban U-105, molecular weight of polypropylene oxide portion 3250, content of ethylene oxide unit 50 mol% Surfactant-2: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic L31, molecular weight of polypropylene oxide portion 950, content of ethylene oxide unit 10 mol% Surfactant-3: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic L61, molecular weight of polypropylene oxide portion: 1750, content of ethylene oxide unit: 10 mol% Surfactant-4: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic L101, molecular weight of polypropylene oxide portion 3250, content of ethylene oxide unit 10 mol% Surfactant-5: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic L64, molecular weight of polypropylene oxide portion: 1750, content of ethylene oxide unit: 40 mol% Surfactant-6: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic F68, molecular weight of polypropylene oxide portion: 1750, content of ethylene oxide unit: 80 mol% Surfactant-7: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic P-103, molecular weight of polypropylene oxide portion 3250, content of ethylene oxide unit 30 mol% Surfactant-8: Nonionic surfactant, polypropylene oxide / ethylene oxide copolymer, ADEKA Adeka Pluronic P-85, molecular weight of polypropylene oxide portion 2250, content of ethylene oxide unit 50 mol% Carbon black: Asahi Carbon Asahi #60UG White filler: Southeastern Clay Crown Clay Softener (oil): Naphthenic oil, Sun Oil Sansen 450 Processing aid: Rhein Chemie Aflax 12NS Vulcanizing agent (sulfur): Rhenogran S-80 manufactured by Rhein Chemie Vulcanization accelerator-1: Thiam-based crosslinking accelerator, Sanshin Chemical Sanmix TT-75E Vulcanization accelerator-2: Thiazole crosslinking accelerator, Sanshin Chemical Sanmix M-75E Vulcanization accelerator-1: Zinc oxide, Meta Z L-40 manufactured by Inoue Lime Industry Vulcanization accelerator-2: Stearic acid made by Nippon Oil & Fats

[0046] [Table 1]

[0047] In the table, the molecular weight of the polypropylene oxide portion is described as "molecular weight of hydrophobic group," and the content of ethylene oxide units is described as "EO unit content." The molecular weight of the polypropylene oxide portion and the content of ethylene oxide units are catalog values.

[0048] Specifically, each rubber was prepared as follows. A compound was prepared by blending the rubber components (EPDM-1, EPDM-2) with an ionic water-absorbing resin, a nonionic surfactant, carbon black, a white filler, a softener, etc. Then, this compound was kneaded with a twin-screw kneader such as a mixer under conditions of a discharge temperature of 100°C and a rotation speed of 25 rpm. A vulcanizing agent and a vulcanization accelerator were added to the kneaded compound with an 8-inch roll to prepare a composition. The composition was press-vulcanized under conditions of 170°C and 15 minutes to obtain the rubber of Experimental Example 1-9.

[0049] 3. Evaluation method The water expansion ratio (times) was measured by the method described in the embodiment. The hardness was measured using a type A durometer based on JIS K6253. The tensile strength (MPa) was measured based on JIS K6251. The elongation (%) was measured based on JIS K6251. Density (Mg / m 3 ) was measured based on JIS K6268.

[0050] 4.Results The results are shown in Table 1. (1) Fulfillment of each requirement of Experimental Examples 1-9 The rubbers of Experimental Examples 1-7 and 9 satisfy all of the following requirements (a)-(c). Requirement (a): Contains rubber components. · Requirement (b): Contains an ionic water-absorbing resin. Requirement (c): Contains a nonionic surfactant which is a polypropylene oxide / ethylene oxide copolymer. In contrast, the rubber of Experimental Example 8 does not satisfy requirement (c).

[0051] Moreover, the rubbers of Experimental Examples 1-7 and 9 satisfy the following requirements. Requirement (d): The molecular weight of the polypropylene oxide portion is 700 or more and 4,000 or less. Among the rubbers of Experimental Examples 1-7 and 9, the rubbers of Experimental Examples 1, 3-7 and 9 satisfy the following requirements. Requirement (d-2): The molecular weight of the polypropylene oxide portion is 1,250 or more and 3,300 or less.

[0052] Moreover, the rubbers of Experimental Examples 1-7 and 9 satisfy the following requirements. Requirement (e): The content of ethylene oxide units is 5 mol % or more and 85 mol % or less. Of the rubbers of Experimental Examples 1-7 and 1-9, the rubber of Experimental Example 1-7 satisfies the following requirements. Requirement (e-2): Contains 5 mol % or more and 75 mol % or less of ethylene oxide units.

[0053] (2) Results and Discussion The rubbers of Experimental Examples 1-7 and 1-9 had a water swelling ratio of 2.6 times or more. This suggests that if all of the requirements (a) to (c) are satisfied, the initial water swelling rate can be improved.

[0054] Comparing Experimental Examples 2 to 4 (ethylene oxide unit content 10%), the initial water swelling rate increased as the molecular weight of the polypropylene oxide portion increased from 950 (Experimental Example 2), to 1750 (Experimental Example 3), to 3250 (Experimental Example 4). It was suggested that if requirement (d) is satisfied in addition to requirements (a) to (c), the initial water swelling rate can be further improved.

[0055] Comparing Experimental Examples 3, 5, and 9 (molecular weight of polypropylene oxide portion: 1750), the initial water swelling rate was higher at 40% (Experimental Example 5) and 10% (Experimental Example 3) ethylene oxide unit content than at 80% (Experimental Example 9). It was suggested that if requirement (e) is satisfied in addition to requirements (a)-(c), the initial water swelling rate can be further improved.

[0056] In Experimental Examples 4 and 6, the molecular weight of the polypropylene oxide portion was 3250, and the content of the ethylene oxide unit was 10% and 30%, respectively. In Experimental Examples 4 and 6, the water expansion ratio was 8 times or more, and the initial water expansion speed was particularly high.

[0057] 5. Effects of the embodiment According to the above-mentioned embodiment, a water-swellable rubber having a large initial water swelling rate can be provided.

[0058] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible. [Explanation of symbols]

[0059] 1...Rubber

Claims

1. A rubber component, An ionic water absorbent resin; A nonionic surfactant which is a polypropylene oxide / ethylene oxide copolymer; The nonionic surfactant is a rubber (excluding those containing thermosetting polyurethane) represented by the following formula (I). 【Chemistry 1】 (In formula (I), a, b, and c represent integers.)

2. A rubber component, An ionic water-absorbing resin; A nonionic surfactant which is a polypropylene oxide / ethylene oxide copolymer; The nonionic surfactant contains 10 mol % or more and 50 mol % or less of ethylene oxide units, where the total of the propylene oxide units and the ethylene oxide units is 100 mol %, The nonionic surfactant is a rubber represented by the following formula (I). 【Chemistry 2】 (In formula (I), a, b, and c represent integers.)

3. 3. The rubber according to claim 1 or 2, wherein the nonionic surfactant is a polypropylene oxide / ethylene oxide copolymer in which the polypropylene oxide portion has a molecular weight of 700 or more and 4,000 or less.

4. The rubber according to any one of claims 1 to 3, wherein the ionic water-absorbing resin is a resin containing a structural unit derived from a (meth)acrylic acid-based monomer.

5. A water-stopping material comprising the rubber according to any one of claims 1 to 4.

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