Silicone rubber hose

Abstract

To provide a silicone rubber hose which is excellent in kink resistance and heat resistance, and favorable in flexibility.SOLUTION: A silicone rubber hose H1 is excellent in elongation / contraction performance, and formed by winding a reinforcing material between an inner layer 1 and an outer layer 2. The durometer A-hardness of silicone rubber constituting the inner layer 1 is 55 to 85, the durometer A-hardness of silicone rubber constituting the outer layer 2 is 35 to 65, in the silicone rubber constituting the inner layer 1 or the outer layer 2, tear strength (Sa) which is measured in conformity to JIS-K-6252 is 5 to 60 N / mm, and in the silicone rubber constituting the outer layer 2, a ratio (viscoelastic recovery rate / permanent set rate) of a viscoelastic recovery rate which is defined by the following formula (1) to a permanent set rate which is defined by the following formula (2) is equal to or lower than 2.2. The viscoelastic recovery rate={(elongation deformation amount-stress residual recovery amount-residual strain amount) / elongation deformation amount}×100 ...(1). The permanent set rate=(residual strain amount / elongation deformation amount)×100 ...(2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a silicone rubber hose having excellent kink resistance, heat resistance and good flexibility, for use in, for example, the food, beverage, medical equipment, chemical and other industries, and in particular to a milking hose. [Background technology]

[0002] Tubes and hoses used in the medical, food, and industrial parts fields require flexibility and kink resistance, and so have traditionally been made of polyvinyl chloride resin. However, in recent years, due to growing concern about environmental issues, tubes and hoses made of silicone rubber instead of polyvinyl chloride resin have been developed (Patent Document 1).

[0003] For milking purposes, flexible milking hoses are used in milking machines used in milking work to extract milk from dairy cows, etc. Milking hoses are used between the milking head attached to the udder of the dairy cow, etc., and the milking machine main body that generates suction force to collect milk, and for piping inside the milking machine main body. In order to improve workability and to avoid putting a strain on the udder when a milking hose is used between the milking head and the milking machine main body, flexibility is required for the milking hose. In addition, the milking hose is required to be kink-resistant.

[0004] As milking hoses, typically, tubes formed with a thick wall from silicone rubber or the like, or tubes formed from soft resins are known. Such tubes are solid cylindrical. For example, Patent Document 2 discloses a resin composition containing an amorphous α-olefin polymer and petroleum resins, and a tube made of the resin composition, and discloses that the tube has excellent kink resistance and heat resistance and can be used for milking purposes. Patent Document 3 discloses a multi-layer tube in which layers made of linear low-density polyethylene resins with different moduli and polyolefin elastomer layers are laminated, and discloses that the tube suppresses the elution of material components, is flexible, and can be used for milking purposes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-54052 A [Patent Document 2] JP 2004-285299 A [Patent Document 3] JP 2001-317662 A Summary of the Invention [Problem to be solved by the invention]

[0006] From the viewpoint of milking in particular, a heavy milking hose is not only difficult to handle during milking, but also places a burden on the udders of dairy cows, etc., and is therefore undesirable. That is, there is a demand for lighter milking hoses. A tubular (solid cylindrical) milking hose as described in the above patent document needs to be relatively thick-walled to prevent kinking when bent, and it is difficult to reduce the weight. Furthermore, as attempts to automate milking work are being made, if a milking hose is easily damaged, milking work becomes impossible and the health of dairy cows, etc. is easily harmed, and therefore there is a demand for milking hoses with a long life.

[0007] Furthermore, in conventional silicone reinforced hoses, if the silicone rubber of the inner and outer layers is softened to make it easier to use, when a pulling force acts in the axial direction of the silicone reinforced hose or when the entire hose expands due to a change in internal pressure, the inner and outer layers expand and contract in the axial direction, but the elasticity of the reinforcing material is significantly lower than that of silicone rubber, and in addition, silicone rubber has high releasability and lubricity, so the reinforcing material is more likely to move than other rubbers or constituent resins. Therefore, every time the silicone reinforced hose expands and contracts, the reinforcing material gradually moves from the axial end of the silicone reinforced hose, causing it to come off, and there is a problem that the pressure resistance of the missing part is significantly reduced.

[0008] Furthermore, in the connection structure of a silicone reinforced hose, the pressure resistance of the connection end arranged at the axial end of the silicone reinforced hose drops significantly as the reinforcing material falls off, so that the loss of the reinforcing material easily causes rupture between the connection end and the connection fitting, in which case the connection fitting must be discarded together with the ruptured hose, resulting in the problem of high hose replacement costs. Therefore, in order to prevent the reinforcing material from falling off, it can be considered to insert the connection end of the reinforced hose into the outer circumferential surface of the nipple and then strongly tighten it from the outside with a tightening tool to reduce the diameter, thereby pinching the reinforcing material so that it does not move.

[0009] In this case, however, when the fastener is tightened too much, the silicone rubber sandwiched between the fastener and the nipple is pushed out, creating a step between the inner surface of the nipple and the inner surface of the hose, causing problems such as the fluid transported through the hose remaining in the step or increasing the resistance inside the pipe. As a means of preventing the reinforcing material from coming off, it is possible to increase the adhesion between the inner and outer layers by applying a silicone rubber-based primer to the surface of the reinforcing material, but this increases the cost.

[0010] The tubes and silicone-reinforced hoses of the prior art were not fully satisfactory in terms of kink resistance and heat resistance. Under such circumstances, the problem that the present invention aims to solve is to provide a hose that is excellent in kink resistance and heat resistance and has good flexibility. A milking hose is particularly preferable. Furthermore, it is intended to prevent the reinforcing material from coming off, to increase the rigidity of the silicone rubber hose against twisting to prevent the silicone rubber hose from collapsing due to twisting, and to prevent the hose connection end from breaking with a simple structure, even for a silicone rubber hose molded from a silicone rubber with excellent flexibility. [Means for solving the problem]

[0011] As a result of intensive research, the present inventors have found that the above problems can be solved by the silicone rubber hose of the present invention. The silicone rubber hose of the present invention is manufactured using silicone rubber with excellent elasticity, and is formed by wrapping a reinforcing material between the inner layer and the outer layer, in which the silicone rubber constituting the inner layer has a durometer A hardness of 55 to 85, the silicone rubber constituting the outer layer has a durometer A hardness of 35 to 65, at least one of the silicone rubber constituting the inner layer and the silicone rubber constituting the outer layer has a tear strength (Sa) measured in accordance with JIS-K-6252 of 5 to 60 N / mm, and the silicone rubber constituting the outer layer has a ratio (viscoelastic recovery rate / permanent set rate) of 2.2 or more between the viscoelastic recovery rate defined by the following formula (1) and the permanent set rate defined by the following formula (2): Viscoelastic recovery rate = {(elongation deformation amount - stress residual deformation recovery amount - residual strain amount) / elongation deformation amount} × 100 (1) Permanent set rate = (residual set amount / elongation deformation amount) × 100 (2) Effect of the Invention

[0012] According to the present invention, it is possible to provide a silicone rubber hose that has excellent kink resistance, heat resistance, and flexibility. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a partially cutaway front view of a silicone rubber hose according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a partially cutaway front view of a silicone rubber hose according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (First embodiment) A first embodiment of the present invention will be described below with reference to Fig. 1. In the silicone rubber hose H1 (see Fig. 1) according to the first embodiment of the present invention, the silicone rubber constituting the inner layer 1 has a durometer A hardness of 55 to 85, the silicone rubber constituting the outer layer 2 has a durometer A hardness of 35 to 65, and at least one of the silicone rubber constituting the inner layer 1 and the silicone rubber constituting the outer layer 2 has a tear strength (Sa) of 5 to 60 N / mm measured in accordance with JIS-K-6252, and is manufactured using silicone rubber with excellent elasticity. The durometer A hardness of the silicone rubber was measured in accordance with JIS-K-6253 after the uncured millable silicone rubber was cured in an environment of 200°C for 2 hours.

[0015] By setting the silicone rubber hardness within this range, it is possible to obtain a silicone hose H1 that has high kink resistance and does not significantly deteriorate in flexibility. If the lower limit of the durometer A hardness of the silicone rubber constituting the inner layer 1 is less than 55, the kink resistance is low, and if the upper limit of the durometer A hardness of the silicone rubber constituting the outer layer 2 exceeds 65, the required bending load is large, and in either case, a flexible silicone rubber hose H1 cannot be realized. If the lower limit of the durometer A hardness of the silicone rubber constituting the outer layer 2 is less than 35, the flexibility is good but the hose is prone to kinking, and if the upper limit of the durometer A hardness of the silicone rubber constituting the inner layer 1 exceeds 85, the hardness increases and the usability becomes poor like that of a metal flexible piping.

[0016] Furthermore, the silicone rubber constituting the outer layer 2 of the silicone rubber hose H1 of this embodiment has a ratio of viscoelastic recovery defined by the following formula (1) to the permanent set defined by the following formula (2) (viscoelastic recovery / permanent set) of 2.2 or more, preferably 2.25 or more, more preferably 2.3 or more, and even more preferably 2.5 or more. If this value is too low, the kink resistance of the silicone rubber may deteriorate. Viscoelastic recovery rate = {(elongation deformation amount - stress residual deformation recovery amount - residual strain amount) / elongation deformation amount} × 100 (1) Permanent set rate = (residual set amount / elongation deformation amount) × 100 (2)

[0017] In addition, in one aspect, the silicone rubber hose H1 of this embodiment is firmly tightened with a tightening tool to reduce its diameter and then connected to a fitting. However, if the ratio of the viscoelastic recovery rate defined by the above-mentioned formula (1) below to the permanent set rate defined by the following formula (2) is too low, the silicone rubber will have a weak recovery force from deformation when connected to a fitting in this manner, and the fixing strength of the reinforcing material will be poor, which may result in the reinforcing material coming loose.

[0018] In the above formulas (1) and (2), the elongation deformation amount, stress residual deformation recovery amount, and residual strain amount are values ​​determined from an elastic hysteresis test of the resin composition, and the elongation deformation amount represents the deformed length of the silicone rubber when it is elongated to a predetermined length (state A). The stress residual deformation recovery amount represents the change in the deformed length of the silicone rubber from state A to state B when the tensile load is gradually reduced from state A to zero (state B). The residual strain represents the deformed length of the silicone rubber when it is left to stand in a free state for a certain period of time after state B (state C).

[0019] The elastic hysteresis test of silicone rubber is carried out by the following method. (1) Before curing, millable silicone rubber is press molded at 160°C and then cured for 2 hours in an environment of 200°C to produce a sheet with a thickness of 0.5 mm. (2) From the sheet, a dumbbell-shaped No. 1 test piece (gauge length = 40 mm) is prepared in accordance with JIS-K-6251. (3) The test piece is subjected to the following operations (i) to (iv) at a temperature of 23° C. using a tensile tester (Strograph R, manufactured by Toyo Seiki Seisaku-sho, Ltd.). (4)(i) The test piece is stretched to a stretch deformation rate of 100% (gauge length 80 mm) at a crosshead speed of 500 mm / min (stretch deformation amount = 40 mm). (5)(ii) Immediately after extension, the test piece is contracted at a crosshead speed of 500 mm / min until the tensile stress becomes zero. (6)(iii) Measure the gauge length when the tensile stress becomes zero, and calculate the difference between that length and the gauge length of 80 mm when the elongation deformation rate is 100%, and use this value as the stress residual deformation recovery amount. (7)(iv) Immediately after the tensile stress of the test piece becomes zero, leave the test piece at rest in a free state at 23°C for 5 minutes, and measure the gauge length. The difference between the gauge length and the gauge length of 40 mm before the test is calculated, and this value is regarded as the amount of residual strain.

[0020] The silicone rubber hose H1 of this embodiment has excellent heat resistance and kink resistance, and can be used for various molded products.

[0021] The silicone rubber used for the inner layer 1 or the outer layer 2 to manufacture the silicone rubber hose H1 of this embodiment has a tear strength (measured according to JIS-K-6252) of 5 to 60 N / mm, preferably 15 to 60 N / mm, obtained by press-molding uncured millable silicone rubber at 160°C and then curing it in an environment of 200°C for 2 hours. If the tear strength is less than 5 N / mm, the deformation does not return when the hose is bent or stretched, causing dimensional deviation, which causes the wall thickness to change and makes it difficult to handle, and there is a concern that the wall thickness may change and cause a tear to occur from the point where the wall thickness has changed, which is undesirable. Furthermore, if the tear strength is greater than 60 N / mm, the hose is difficult to deform and difficult to handle, and the resilience when bent and used is large, which reduces workability, which is undesirable.

[0022] Furthermore, the silicone rubber used to manufacture the silicone rubber hose H1 of this embodiment has better flexibility and kink resistance when it satisfies the following formula (3). When the durometer A hardness of the silicone rubber constituting the inner layer 1 is greater than the durometer A hardness of the silicone rubber constituting the outer layer 2, the inner layer 1, which has a relatively higher hardness, retains the shape of the silicone rubber hose H1 while the outer layer 2, which has a lower hardness, flexibly deforms when the silicone rubber hose H1 is bent for use, improving the flexibility and kink resistance of the silicone rubber hose H1. Preferably, the durometer A hardness of the silicone rubber constituting the inner layer 1 is greater than the durometer A hardness of the silicone rubber constituting the outer layer 2 by 10 or more, and more preferably by 15 or more. Durometer A hardness of the silicone rubber constituting the inner layer - Durometer A hardness of the silicone rubber constituting the outer layer ≧ 10 (3)

[0023] In the silicone rubber hose H1 of this embodiment, the inner layer 1 and outer layer 2, made from silicone rubber satisfying a specific range of physical properties, expand and contract in the axial direction of the hose, and the tubular knitted braid (reinforcement) 3 also expands and contracts in the same direction. Furthermore, when the entire hose is twisted in the circumferential direction, the forces acting on the intersecting braid rows in the two intersecting directions are balanced, and the hose maintains its tubular shape.

[0024] As shown in Fig. 1, silicone rubber hose H1 is formed by integrating inner layer 1 and outer layer 2 by knitting braid 3 between them into a cylindrical shape to form layers. The inner layer 1 and outer layer 2 are made mainly from silicone rubber, which has excellent flexibility, and after first extruding the inner layer 1 using a known extrusion molding device, braid 3, which will be described later, is woven along its outer circumferential surface using a knitting machine (not shown), and further extruding and laminating the outer layer 2 on the outside of braid 3.

[0025] The braid 3 thus knitted is made of reinforcing threads or fibers such as polyester, nylon, or aramid fiber, and is made of warp knit rows 3a extending in the axial direction of the silicone rubber hose H1 and weft knit rows 3b intersecting the warp knit rows 3a and extending in the circumferential direction of the silicone rubber hose H1, knitted in an elastic manner. The warp knit rows 3a and weft knit rows 3b are knitted in such a way that the warp knit rows 3a are parallel to the axial direction of the silicone rubber hose H1 and the weft knit rows 3b are perpendicular to the warp knit rows 3a, or, as shown in Fig. 1, they are wound in a spiral shape at a predetermined angle inclined from the axial direction of the silicone rubber hose H1 so that the forces acting on the warp knit rows 3a and weft knit rows 3b are balanced with respect to the twist of the silicone rubber hose H1. The crossing angle of the warp knit rows 3a and weft knit rows 3b may be inclined at any angle other than the approximately right angle shown in the figure.

[0026] In addition, the silicone rubber hose H1 of this embodiment may be provided with other layers such as a third layer and a second reinforcing layer in addition to the reinforcing layers consisting of the inner layer 1, the outer layer 2, and the braid 3. As a connecting means for connecting the silicone rubber hose H1 to another device, a joint that holds the hose by fitting the connecting end of the silicone rubber hose H1 onto the outer circumferential surface of a nipple portion and tightening it from the outside with a tightening tool such as a crimped pipe, a hose clamp, a cap nut, or a split holder to reduce the diameter can be considered, but the present invention is not limited to this. The joint is made of hard synthetic resin, metal, etc., and has a nipple portion formed on its axial tip side and a connecting means for connecting to another device provided on its base end side, making it possible to connect to other devices for various purposes.

[0027] Because the silicone rubber hose H1 of this embodiment has the configuration and features as described above, the inner layer 1 and outer layer 2 of the silicone rubber hose H1 of this embodiment have a strong ability to recover from deformation when a pulling force acts in the axial direction of the silicone rubber hose H1 or when the entire hose expands due to a change in internal pressure, because the viscoelastic recovery rate and permanent set rate of the silicone rubber constituting the outer layer 2 of the silicone rubber hose H1 are within a predetermined range. As a result, the reinforcing material is firmly held in place by the reduction in diameter of the silicone rubber hose H1 due to tightening with a tightening tool, preventing the reinforcing material from coming loose.

[0028] In particular, when knitted braid 3 is used as the reinforcing material, as shown in Figure 1, braid 3 (reinforcing threads, reinforcing fibers) is woven in alternating vertical and horizontal directions, which significantly reduces thread loss compared to a spirally wound braid. Furthermore, even if the entire silicone rubber hose H1 is twisted in the circumferential direction, the forces acting on the reinforcing material are balanced and the silicone rubber hose H1 maintains its cylindrical shape. As a result, the torsional rigidity of the silicone rubber hose H1 is increased, and it is possible to prevent the silicone rubber hose H1 from collapsing due to twisting.

[0029] In addition, by reducing the diameter of the silicone rubber hose H1 with the liner sandwiched between the outer periphery of the connection end and the fastener, the fastener is protected from direct contact with the outer periphery of the connection end. As a result, even if the hose is made of silicone rubber with excellent flexibility, the connection end can be prevented from breaking with a simple structure. The material of the liner can be thermoplastic resin, rubber, metal, etc., but when used in food machinery or medical equipment, it is preferable to use a material that is safe from the viewpoint of food hygiene and has excellent heat resistance, such as hard or semi-hard silicone rubber, fluororesin, or nylon resin.

[0030] The silicone rubber of this embodiment may contain other resins, rubber / elastomer components, additives, etc., as necessary. Examples of other resins include polyethylene resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene (LLDPE), ethylene copolymer resins such as ethylene-vinyl acetate copolymer resin, ethylene-acrylate copolymer resin, ethylene-methacrylate copolymer resin, and ethylene-styrene copolymer resin, homopolypropylene resin, block polypropylene resin, polybutene resin, poly-4-methyl-pentene-1 resin, polystyrene resin, polyester resin, polyamide resin, polyphenylene ether resin, polyacetal resin, and polycarbonate resin. Examples of rubber / elastomer components include natural rubber; polybutadiene; liquid polybutadiene; polyacrylonitrile rubber; acrylonitrile-butadiene copolymer rubber; partially hydrogenated acrylonitrile-butadiene copolymer rubber; ethylene-based rubbers with an ethylene unit content of 70 mol% or more, such as ethylene-propylene rubber, ethylene-butene rubber, ethylene-hexene rubber, and ethylene-octene rubber; fluororubber; urethane rubber; isobutylene-isoprene copolymer rubber; non-crosslinked olefin-based thermoplastic elastomers, partially crosslinked olefin-based thermoplastic elastomers, and fully crosslinked olefin-based thermoplastic elastomers.

[0031] Examples of additives include antioxidants, antioxidants, antiozone deterioration agents, stabilizers such as ultraviolet absorbers and light stabilizers, lubricants, fillers, flame retardants, high-frequency processing aids, antistatic agents, internal release agents, colorants, dispersants, antiblocking agents, and antifogging agents.

[0032] Examples of the lubricant include wax, higher alcohol, fatty acid, fatty acid metal salt, fatty acid amide, carboxylate, phosphoric acid ester, sulfonic acid metal salt, acid ester metal salt, acrylic resin, fluorine-containing resin, and silicone. Two or more of these may be used in combination.

[0033] Examples of the wax include petroleum waxes such as paraffin wax and microcrystalline wax; vegetable waxes such as rice wax; mineral waxes such as montan wax; and synthetic waxes such as polyethylene wax and low molecular weight polypropylene.

[0034] Examples of the higher alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, oleyl alcohol, erucyl alcohol, and 12-hydroxystearyl alcohol.

[0035] Examples of the fatty acid include lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, linoleic acid and ricinoleic acid.

[0036] Examples of the fatty acid metal salts include salts of fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, linoleic acid, and ricinoleic acid with metals such as Li, Na, Mg, Al, K, Ca, Zn, Ba, and Pb.Specific examples of the fatty acid metal salts include lithium stearate, sodium stearate, calcium stearate, and zinc stearate.

[0037] Examples of the fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, and stearyl diethanol amide.

[0038] Examples of the carboxylic acid esters include esters of carboxylic acids such as aliphatic carboxylic acids (acrylic acid, crotonic acid, isocrotonic acid, fumaric acid, maleic acid, succinic acid, aconitic acid, etc.), fatty acids (lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, linoleic acid, ricinoleic acid, etc.), and oxycarboxylic acids (lactic acid, malic acid, tartaric acid, citric acid, etc.) with alcohols such as aliphatic alcohols (myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, 12-hydroxystearyl alcohol, etc.), aromatic alcohols (benzyl alcohol, β-phenylethyl alcohol, phthalyl alcohol, etc.), and polyhydric alcohols (glycerin, diglycerin, polyglycerin, sorbitan, sorbitol, propylene glycol, polypropylene glycol, polyethylene glycol, pentaerythritol, trimethylolpropane, etc.). Specific examples of carboxylates include glycerin monooleate, glycerin dioleate, polyethylene glycol monostearate, and citrate distearate.

[0039] Examples of the phosphoric acid ester include monoalkyl esters, dialkyl esters and trialkyl esters of phosphoric acid and higher alcohols.

[0040] Examples of the acrylic resin include polymers mainly composed of structural units derived from acrylic acid esters such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and structural units derived from methacrylic acid esters such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate.Specific examples of the acrylic resin include an acrylic resin manufactured by Mitsubishi Chemical under the trade name Metablen, and an acrylic resin manufactured by Kaneka under the trade name Kane Ace.

[0041] Examples of the above-mentioned metal sulfonates include sodium stearyl sulfonate, sodium lauryl sulfonate, sodium dodecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate, potassium stearylsulfonate, potassium lauryl sulfonate, dibutyl sodium sulfosuccinate, di-2-ethylhexyl sodium sulfosuccinate, disodium lauryl sulfosuccinate, and 2-sodium lauryl polyoxyethylene sulfosuccinate.

[0042] Examples of the acid ester metal salts include sulfates such as sodium lauryl sulfate and potassium lauryl sulfate; and phosphates such as sodium lauryl phosphate and potassium lauryl phosphate.

[0043] Examples of the above-mentioned fluorine-containing resins include fluorine-containing olefins such as tetrafluoroethylene, hexafluoropropylene, fluoroalkylethylene and perfluoroalkylvinylether; fluorine-containing alkyl acrylates such as perfluoroalkyleneacrylate and perfluoromethalkyleneacrylate; and polymers having as their main unit a structural unit derived from a fluorine-containing compound such as fluorine-containing alkyl methacrylate.Specific examples of the fluorine-containing resins include polytetrafluoroethylene and perfluoro(polyoxypropylene ethyl ether).

[0044] The silicone rubber hose H1 of the present embodiment can be used as piping for oil, various chemicals, air, various gases, water, etc. in the fields of various industrial vehicles, such as automobiles, construction machinery, agricultural machinery, and railway cars; various industrial and mining machinery, such as machine tools, construction machinery, agricultural machinery, mining machinery, industrial robots, chemical plants, coating machines, chemical transfer machines, food industry machinery, and hydraulic tools; and ships.

[0045] Specific examples of the silicone rubber hose H1 of this embodiment include automobile hoses such as filler hoses, evaporation hoses, fuel hoses, vapor emission hoses, in-tank fuel hoses, power steering hoses, air conditioning hoses, radiator hoses, heater hoses, transmission oil cooler hoses, engine oil cooler hoses, brake hoses, turbocharger drain hoses, fuel injection hoses, air conditioning hoses, air duct hoses, air intake hoses, vacuum control hoses, and air pollution control hoses; hoses for hydraulic machines, hoses for pneumatic machines, hoses for centralized lubrication equipment, hoses for painting equipment, hoses for chemical plants, hoses for transferring solvents and chemical liquids, hoses for transferring various liquefied gases, hoses for food-related machines, hoses for beverage-related machines, hoses for chemical plants, and the like. Examples of the hoses include hoses for various industrial machines and vehicles such as hoses for academic equipment, hoses for spinning machines, hoses for packing machines, hoses for printing machines, hoses for transmission machines, hoses for water treatment devices, hoses for fluid elements, hoses for industrial robots, hoses for industrial vehicles, hoses for agricultural machines, hoses for construction machines, hoses for machine tools, hoses for injection molding machines, hoses for labor-saving machines, hoses for air tools such as air drivers and air hammers, hoses for moving parts, hoses for air pressure / electrical signals, hoses for air pressure / signals, hoses for equipment that require heat resistance, high insulation, and high frequency characteristics, hoses for spot welding equipment, steam hoses, agricultural spray hoses, brewing hoses, diving hoses, bandless oil hoses, gas tubing hoses, air brake hoses, gas station hoses, tanker hoses, rotary hoses, and fire extinguisher hoses; hoses for medical equipment such as various infusion hoses and intake and exhaust hoses. In particular, the hoses are preferable as milking hoses.

[0046] The silicone rubber hose H1 according to the present embodiment described above can provide the following effects. That is, the silicone rubber hose H1 of the present embodiment firmly holds the reinforcing material by reducing the diameter of the silicone rubber hose H1 by tightening with a tightening tool, and can prevent the reinforcing material from falling out. Therefore, compared to conventional hoses in which the reinforcing material easily falls out, the pressure resistance of the entire hose can be maintained high and rupture can be prevented, and manufacturing costs can be reduced compared to hoses in which the adhesion between the inner layer and outer layer is increased by applying a silicone rubber-based primer to the surface of the reinforcing material, for example.

[0047] Furthermore, when the entire hose is twisted in the circumferential direction, the forces acting on the reinforcing material are balanced and the hose maintains its cylindrical shape, increasing the rigidity of the hose against twisting and preventing the hose from collapsing due to twisting. It also has high durability against cleaning with chemicals used in milking, and has a long life. Not only for milking, but when used in industries that use cleaning with chemicals, it can be used with a much longer life than conventional products.

[0048] Second embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 2. A silicone rubber hose H2 (see Fig. 2) according to the second embodiment of the present invention is integrated by spirally winding a wire 4 as a reinforcing material between an inner layer 1 and an outer layer 2 to form a coil shape. Other configurations are the same as those of the first embodiment, so description thereof will be omitted.

[0049] This wire 4 is a hard wire made of a hard fiber such as a rust-resistant metal wire such as stainless steel or a monofilament made of a single synthetic resin fiber, or a hard synthetic resin, and is formed by leading it from a coil forming machine or a coil storage section and winding it around the outer periphery of the inner layer in a stationary state.

[0050] In the silicone rubber hose H2 of this embodiment, the inner and outer layers made of silicone rubber satisfying a specific range of physical properties expand and contract in the axial direction of the hose, and the coiled reinforcing material also expands and contracts in the same direction. Furthermore, when the entire hose is twisted in the circumferential direction, the repulsive forces of the coiled reinforcing material are balanced, and the hose maintains its cylindrical shape.

[0051] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. EXAMPLES

[0052] The present invention will be described in more detail below with reference to examples and comparative examples. In the examples and comparative examples, the physical properties of the silicone rubber hose were measured by the following methods.

[0053] 1. Viscoelastic recovery rate / permanent set rate In the examples and comparative examples, the ratio of viscoelastic recovery to permanent set of the silicone rubber constituting the silicone rubber hose (viscoelastic recovery / permanent set) was determined by determining the elongation deformation amount, stress residual deformation recovery amount, and residual strain amount according to the following procedures (i) to (iv), and then calculating the viscoelastic recovery and permanent set according to the following formulas (1) and (2). (i) Silicone rubber was press-molded at 160°C, and then cured for 2 hours at 200°C to produce a sheet with a thickness of 0.5 mm. (ii) From the produced sheet, a dumbbell-shaped No. 1 test piece (gauge length = 40 mm) as specified in JIS-K-6251 was prepared. (iii) The prepared test pieces were subjected to the following operations using a tensile testing machine (Strograph R, manufactured by Toyo Seiki Seisaku-Sho, Ltd.). (a) The test piece was stretched at a crosshead speed of 500 mm / min to a stretch deformation rate of 100% (gauge length = 80 mm) (stretch deformation amount = 40 mm). (b) Immediately after the test piece was stretched, it was contracted at a crosshead speed of 500 mm / min until the tensile stress reached zero. (c) The gauge length was measured when the tensile stress of the test piece became zero, and the difference between the measured gauge length and the gauge length of 80 mm when the elongation deformation rate was 100% was calculated. This value was regarded as the stress residual deformation recovery amount. (iv) The test piece whose tensile stress had become zero was immediately allowed to stand for 5 minutes in a free state at a temperature of 23°C after the tensile stress had become zero, and the gauge length was measured. The difference between the measured gauge length and the gauge length of 40 mm before the test was calculated, and this value was regarded as the amount of residual strain. Viscoelastic recovery rate = {(elongation deformation amount - stress residual deformation recovery amount - residual strain amount) / elongation deformation amount} × 100 (1) Permanent set rate = (residual set amount / elongation deformation amount) × 100 (2)

[0054] 2.Hardness Before curing, the millable silicone rubber was press molded at 160° C. and then cured for 2 hours in an environment of 200° C. to produce a sheet having a thickness of 2 mm. The durometer hardness (Duro-A) of the sheet was measured according to JIS-K-6253.

[0055] 3. Kink resistance The molded silicone rubber hose (inner diameter 25.4 mm, outer diameter 35.5 mm) was wound around a 50 mm cylinder in an atmosphere of 23° C. and evaluated according to the following criteria.

[0056] 4. Presence or absence of holes A pressure-resistant nipple was inserted into one end of a molded silicone rubber hose (inner diameter 25.4 mm, outer diameter 35.5 mm) and the end was sealed off with a band. Air was continuously supplied into the hose from the other end. When the hose burst due to pressure from inside the hose, the condition of the reinforcing material was confirmed and evaluated according to the following criteria.

[0057] 5.Tear strength Before curing, Millable silicone rubber was press molded at 160°C, and then cured for 2 hours in an environment of 200°C. Measurements were then carried out according to JIS-K-6251.

[0058] (Measurement results) Each of the silicone rubber hoses of Examples 1 to 6 and Comparative Examples 1 to 4 shown in Table 1 below was installed in actual milking equipment at multiple dairy farms (Dairy Farm A to Dairy Farm D) and monitored and evaluated during daily milking operations. These milking hoses were loaned for monitoring purposes without disclosing composition information, etc., and all were collected after the monitoring period. Note that "hardness" in Table 1 refers to durometer A hardness. "Hose properties" in Table 1 refers to the ratio of viscoelastic recovery rate to permanent set rate (the above-mentioned formula (1) / formula (2)).

[0059] In Examples 1 to 6, the silicone rubber hose constituting the inner layer has a "hardness" of 60 to 81 and a "tear strength" of 10 to 35 N / mm, the silicone rubber hose constituting the outer layer has a "hardness" of 38 to 63 and a "tear strength" of 34 to 56 N / mm, and the "hose characteristics" of the silicone rubber hose are 2.2 to 2.8. In Comparative Example 1, the silicone rubber hose constituting the inner layer has a "tear strength" of less than 5. In Comparative Example 2, the silicone rubber hose constituting the outer layer has a "hardness" of less than 35 and a "hose characteristics" of less than 2.2. In Comparative Example 3, the silicone rubber hose constituting the inner layer has a "hardness" of less than 55.

[0060] Regarding the "reinforcement method" in Table 1, "1" is a silicone rubber hose manufactured using the reinforcement method shown in the first embodiment, and "2" is a silicone rubber hose manufactured using the reinforcement method shown in the second embodiment. Comparative Example 4 is a silicone rubber tube made of a single layer of silicone rubber and not equipped with a reinforcing material.

[0061] [Table 1]

[0062] According to the monitor evaluation, the silicone rubber hoses of Examples 1 to 6 were rated as being lighter and easier to handle than conventional thick-walled hoses / tube-shaped milking hoses in terms of flexibility and lightness, which are related to the ease of handling of the milking equipment.

[0063] Table 2 below shows the evaluation results of the life span of the silicone rubber hoses of Examples 1-6 and the silicone rubber hoses / tubes of Comparative Examples 1-4.

[0064] The "kink resistance" in Table 2 was evaluated according to the following criteria. ○: The outer diameter of the hose wrapped around the cylindrical body is 50% or more of the original outer diameter. △: The outer diameter of the hose wrapped around the cylindrical body is between 30% and 50% smaller than the original outer diameter. ×: The outer diameter of the hose wrapped around the cylinder is less than 30% of the original outer diameter.

[0065] The "washing durability" (lifespan) in Table 2 was judged by having 10 monitored dairy farms use silicone rubber hoses / tubes for up to four months, and when parts of the hose wall hardened or deformed to the point that they could no longer be used, causing problems in use, the hose wall broke and began to leak, or cracks became noticeable in the hose wall, etc., the hose was judged to have reached the end of its life and was rated as x. A hose that was usable as a hose without any cracks, but where some hardening or deformation was felt, was rated as △. Also, hoses that showed no such particular findings and were the same as the original hose were rated as ○. Naturally, some of the hoses deteriorated before the four months had passed.

[0066] The "presence or absence of voids" in Table 2 was evaluated according to the following criteria. ○: No movement of the reinforcement end. △: The end of the reinforcement material has moved and is located between the hose connection end and the band fastening point. ×: The end of the reinforcing material has moved and is located away from the band fastening point when viewed from the hose connection end.

[0067] [Table 2]

[0068] One silicone rubber hose from each Example, a total of 60 hoses, and one silicone rubber hose / tube from each Comparative Example, a total of 40 hoses, were monitored. One month after the start of monitoring, the silicone rubber hose / tube from the Comparative Example produced samples rated △ and samples that had reached the end of their life and were rated × in any of the evaluation items. On the other hand, the silicone rubber hoses from each Example produced samples rated △ after four months, and no samples rated × were produced during the four-month monitoring period.

[0069] As shown in Table 2, it was found that the silicone rubber hoses of each Example had excellent kink resistance and a long life compared to the hoses of Comparative Examples 1 to 4. Furthermore, the silicone rubber hoses of each Example had no loss of reinforcing material compared to the hose of Comparative Example 2, and were prevented from bursting, and could be used continuously for milking operations for a long period of time, making them highly economical.

[0070] When the silicone rubber hose of each embodiment is used as a milking hose, deterioration occurs in relation to the manner of use during cleaning work. Milking hoses are frequently cleaned inside after use to prevent the growth of dirt and germs. A high-temperature (60°C to 80°C) cleaning liquid containing acid or alkali is used for this internal cleaning work. In addition, in order to increase the cleaning efficiency, not only is the cleaning liquid continuously flowed during cleaning work, but the cleaning liquid is intermittently sent into the inside of the hose in a splash-like manner together with air by utilizing the negative pressure of the milking device. In addition, during this cleaning work, the silicone rubber hose takes a bent posture. Then, the high-temperature cleaning liquid that flows into the inside of the hose in a splash-like manner does not collide much with the hose wall in the straight part of the silicone rubber hose, while the cleaning liquid collide violently with the inside of the hose wall in the curved part of the silicone rubber hose. As a result, the silicone rubber hose is exposed to the high-temperature cleaning liquid in a specific part. Therefore, the bent part of this silicone rubber hose is easily deteriorated when it is cleaned. [Explanation of symbols]

[0071] 1 Inner layer 2 Outer layer 3 braid 3a warp knit row 3b Horizontal knitting row 4 wires H1, H2 Silicone Rubber Hose

Claims

1. A silicone rubber hose manufactured using silicone rubber having excellent elasticity, the silicone rubber hose having a reinforcing material wound between the inner layer and the outer layer, The silicone rubber constituting the inner layer has a durometer A hardness of 55 to 85; The silicone rubber constituting the outer layer has a durometer A hardness of 35 to 65; At least one of the silicone rubber constituting the inner layer and the silicone rubber constituting the outer layer has a tear strength (Sa) of 5 to 60 N / mm as measured in accordance with JIS-K-6252; The silicone rubber constituting the outer layer has a ratio of viscoelastic recovery defined by the following formula (1) to permanent set defined by the following formula (2) (viscoelastic recovery / permanent set) of 2.2 or more. Viscoelastic recovery rate={(elongation deformation amount−stress residual deformation recovery amount−residual strain amount) / elongation deformation amount}×100 (1) Permanent set rate=(residual set amount / elongation deformation amount)×100 (2)

2. 2. The silicone rubber hose according to claim 1, which satisfies the following formula (3): Durometer A hardness of silicone rubber constituting the inner layer−Durometer A hardness of silicone rubber constituting the outer layer≧10 (3)

3. 3. The silicone rubber hose according to claim 2, wherein the inner layer made of silicone rubber extruded by an extrusion molding device, the reinforcing material formed in layers by knitting into a tubular shape by a knitting machine along the outer peripheral surface of the inner layer, and the outer layer made of silicone rubber extruded on the outside of the reinforcing material are laminated together, and the warp knitted rows of the knitted reinforcing material are wound spirally at an angle from the axial direction of the silicone rubber hose, and the weft knitted rows are wound spirally so as to be perpendicular to the warp knitted rows.

4. 3. The silicone rubber hose according to claim 2, wherein the silicone rubber hose is formed by laminating the following: the inner layer made of silicone rubber extruded by an extrusion molding device, the reinforcing material formed into a coil shape by being wound spirally around the outer peripheral surface of the inner layer, and the outer layer made of silicone rubber extruded around the outside of the reinforcing material.

5. The silicone rubber hose according to any one of claims 1 to 4, which is used for milking.

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