Silicone rubber hose

Abstract

[Problem] To provide a silicone rubber hose that has exceptional heat resistance and kinking resistance as well as excellent flexibility. [Solution] A silicone rubber hose H1 has exceptional elasticity and is made by wrapping a reinforcing material between an inner layer 1 and an outer layer 2. The durometer A hardness of the silicone rubber constituting the inner layer 1 is 55-85, and the durometer A hardness of the silicone rubber constituting the outer layer 2 is 35-65. The silicone rubber constituting the inner layer 1 or the outer layer 2 has a tear strength (Sa) of 5-60 N / mm measured in conformance with JIS-K-6252. The ratio of the viscoelastic recovery defined by formula (1) to the permanent strain rate defined by formula (2) (viscoelastic recovery / permanent strain rate) of the silicone rubber constituting the outer layer 2 is 2.2 or greater. Formula (1): Viscoelastic recovery rate ={(elongation deformation amount−stress residual deformation recovery amount−residual strain amount) / elongation deformation amount}×100. Formula (2): Permanent strain rate = (residual strain amount / elongation deformation amount)×100.

Description

Silicone Rubber Hose

[0001] The present invention relates to a silicone rubber hose, particularly a milking hose, which has excellent kink resistance, heat resistance and flexibility and is used in industries such as food, beverage, medical equipment, chemicals and other industries.

[0002] Tubes and hoses used in the medical, food, and industrial parts fields require flexibility and kink resistance, and 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 have been developed instead of polyvinyl chloride resin (Patent Document 1).

[0003] Furthermore, flexible milking hoses are used in milking machines used to extract milk from dairy cows and the like. Milking hoses are used between the milking head attached to the udders of dairy cows and the main body of the milking machine that generates suction and collects milk, and in the piping inside the main body of the milking machine. Flexibility is required for milking hoses to improve workability and to avoid placing a strain on the udders when used between the milking head and the main body of the milking machine. Milking hoses are also required to be kink-resistant.

[0004] Typical milking hoses include thick-walled tubes made of silicone rubber or soft resin. These tubes are solid and 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. Patent Document 3 also discloses a multilayer tube formed by laminating layers made of linear low-density polyethylene resins with different moduli and polyolefin elastomer layers, and discloses that the tube suppresses the elution of material components, is flexible, and can be used for milking.

[0005] JP 2010-54052 A JP 2004-285299 A JP 2001-317662 A

[0006] Particularly from the viewpoint of milking, a heavy milking hose is undesirable because it is not only difficult to handle during milking, but also places a burden on the udders of dairy cows, etc. In other words, there is a demand for lighter milking hoses. The tubular (solid cylindrical) milking hoses described in the above patent documents need to be formed with a relatively thick wall to prevent kinking when bent, which makes it difficult to reduce the weight. Furthermore, as attempts to automate milking operations are progressing, if a milking hose is easily damaged, milking operations become impossible and the health of dairy cows, etc. may be easily harmed, so there is a demand for milking hoses with a long life.

[0007] Furthermore, in conventional silicone-reinforced hoses, if the silicone rubber in the inner and outer layers is softened to make them easier to use, when a pulling force is applied 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 will 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.As a result, each 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 loose, resulting in a significant decrease in pressure resistance at the loosened part.

[0008] Furthermore, in the connection structure of a silicone-reinforced hose, the pressure resistance of the connection end located at the axial end of the silicone-reinforced hose drops significantly as the reinforcing material falls off, making it easy for the connection end to rupture between the connection end and the connecting fitting due to the loss of the reinforcing material, in which case the connection fitting must be discarded along with the ruptured hose, resulting in the problem of expensive hose replacement. Therefore, in order to prevent the reinforcing material from falling off, one idea is to insert the connection end of the reinforced hose into the outer peripheral surface of a nipple and then tighten it tightly from the outside with a tightening tool to reduce the diameter, thereby clamping the reinforcing material so that it does not move.

[0009] However, in this case, 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 resistance within the pipe.In addition, as a means of preventing the reinforcing material from coming loose, 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] Tubes and silicone-reinforced hoses made using conventional technology have not been fully satisfactory in terms of kink resistance and heat resistance. Under these 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, particularly a milking hose. Furthermore, the present invention aims to prevent the reinforcing material from coming loose, to increase the torsional rigidity of the silicone rubber hose to prevent the silicone rubber hose from collapsing due to torsion, and to prevent breakage of the hose connection end using a simple structure, even for a silicone rubber hose molded from a highly flexible silicone rubber.

[0011] After extensive research, the present inventors have found that the above-mentioned 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 comprises an inner layer and an outer layer with a reinforcing material wound between them, wherein 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 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 strain amount / elongation deformation amount)×100 (2)

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

[0013] 1A and 1B are partially cutaway front views of a silicone rubber hose according to a first embodiment of the present invention, and a partially cutaway front view of a silicone rubber hose according to a second embodiment of the present invention.

[0014] First Embodiment A first embodiment of the present invention will be described below with reference to Figure 1. A silicone rubber hose H1 (see Figure 1) according to the first embodiment of the present invention is manufactured using silicone rubber having a durometer A hardness of 55 to 85 for the inner layer 1 and a durometer A hardness of 35 to 65 for the outer layer 2. 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 as measured in accordance with JIS-K-6252, demonstrating excellent elasticity. The durometer A hardness of the silicone rubber was measured in accordance with JIS-K-6253 after curing uncured millable silicone rubber for two hours at 200°C.

[0015] By setting the silicone rubber hardness within this range, it is possible to achieve high kink resistance and flexibility that is not significantly impaired. If the lower limit of the durometer A hardness of the silicone rubber constituting the inner layer 1 is less than 55, kink resistance will be poor, and if the upper limit of the durometer A hardness of the silicone rubber constituting the outer layer 2 is above 65, the required bending load will be large, and in either case, a flexible silicone rubber hose H1 will not be achieved. Furthermore, if the lower limit of the durometer A hardness of the silicone rubber constituting the outer layer 2 is less than 35, flexibility will be good but the hose will be prone to kinking, and if the upper limit of the durometer A hardness of the silicone rubber constituting the inner layer 1 is above 85, the hose will be too hard and will be less user-friendly than 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={(elongation deformation amount-stress residual deformation recovery amount-residual strain amount) / elongation deformation amount}×100 (1) Permanent set=(residual strain amount / elongation deformation amount)×100 (2)

[0017] In one aspect, the silicone rubber hose H1 of this embodiment is tightly fastened with a fastener 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, when the hose is connected to a fitting in this manner, the silicone rubber will have a weak recovery force from deformation, which will result in a poor fixing strength of the reinforcing material, and the reinforcing material may come 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 deformation 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 deformation 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 deformation 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 for silicone rubber is performed as follows. (1) Pre-cured Millable silicone rubber is press-molded at 160°C, followed by a curing reaction in an environment of 200°C for 2 hours to produce a sheet with a thickness of 0.5 mm. (2) From this sheet, a dumbbell-shaped No. 1 test specimen (gauge length = 40 mm) is prepared in accordance with JIS-K-6251. (3) The test specimen 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 specimen is stretched at a crosshead speed of 500 mm / min to an elongation deformation rate of 100% (gauge length 80 mm). (Elongation deformation amount = 40 mm) (5) (ii) Immediately after stretching, the test specimen is contracted at a crosshead speed of 500 mm / min until the tensile stress becomes zero. (6) (iii) The gauge length is measured when the tensile stress becomes zero, and the difference between this distance and the gauge length of 80 mm when the elongation deformation rate is 100% is calculated, and this value is the stress residual deformation recovery amount. (7) (iv) The test piece whose tensile stress has become zero is immediately left to stand at a temperature of 23°C in a free state for 5 minutes after the tensile stress becomes zero, and the gauge length is measured. The difference between this distance and the gauge length of 40 mm before the test is calculated, and this value is the residual strain amount.

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

[0021] Furthermore, the silicone rubber used for the inner layer 1 or outer layer 2 to manufacture the silicone rubber hose H1 of this embodiment has a tear strength (measured in accordance with JIS-K-6252) of 5 to 60 N / mm, preferably 15 to 60 N / mm, after pre-cured millable silicone rubber is press-molded at 160°C and then cured for two hours in a 200°C environment. A tear strength of less than 5 N / mm is undesirable because the hose does not recover its original shape when bent or stretched, resulting in dimensional deviation, which can lead to changes in wall thickness and difficulty in handling, as well as the risk of tearing originating from the change in wall thickness. Furthermore, a tear strength greater than 60 N / mm is undesirable because the hose is difficult to deform and handle, and has high resilience when bent and used, reducing workability.

[0022] Furthermore, the silicone rubber used to manufacture the silicone rubber hose H1 of this embodiment will have better flexibility and kink resistance if it satisfies the following formula (3): 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, so that when the silicone rubber hose H1 is bent for use, the inner layer 1, which has a relatively higher hardness, maintains the shape of the silicone rubber hose H1 while the outer layer 2, which has a lower hardness, flexibly deforms, thereby 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 Figure 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 primarily from silicone rubber, which has excellent flexibility, and after first extruding and molding the inner layer 1 using a known extrusion molding device, braid 3, which will be described later, is woven along its outer periphery using a knitting machine (not shown), and then outer layer 2 is extruded and laminated around the outside of braid 3.

[0025] The braid 3 thus knitted is made of reinforcing yarns or fibers such as polyester, nylon, or aramid fiber, and is stretchably knitted with 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 circumferentially of the silicone rubber hose H1. The warp knit rows 3a and weft knit rows 3b are woven so 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. Alternatively, as shown in Figure 1, the braid is spirally wound at a predetermined angle 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 in response to the torsion of the silicone rubber hose H1. The intersecting angle between the warp knit rows 3a and weft knit rows 3b may be any angle other than the approximately right angle shown.

[0026] Furthermore, the silicone rubber hose H1 of this embodiment may be provided with additional layers, such as a third layer or a second reinforcing layer, in addition to the reinforcing layers consisting of the inner layer 1, the outer layer 2, and the braid 3. A possible connection means for connecting the silicone rubber hose H1 to other devices is a coupling that holds the hose by inserting the connection end of the silicone rubber hose H1 onto the outer surface of a nipple portion and tightening it from the outside with a fastener such as a crimped pipe, hose clamp, cap nut, or split holder, thereby reducing the diameter, but the present invention is not limited to this. The coupling is made of a hard synthetic resin or metal, and has a nipple portion formed at its axial tip end and a connection means for connecting to other devices at its base end, allowing connection to other devices for a variety of applications.

[0027] Because the silicone rubber hose H1 of this embodiment has the above-mentioned configuration and characteristics, 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 tensile force is applied 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 predetermined ranges. As a result, the reinforcing material is firmly held in place when the silicone rubber hose H1 contracts in diameter due to tightening with a tightening tool, preventing the reinforcing material from coming loose.

[0028] In particular, when a knitted braid 3 is used as the reinforcing material, as shown in Figure 1, the 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, allowing the silicone rubber hose H1 to maintain its cylindrical shape. As a result, the torsional rigidity of the silicone rubber hose H1 is increased, preventing the silicone rubber hose H1 from collapsing due to twisting.

[0029] Furthermore, 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 a hose made of highly flexible silicone rubber can be prevented from breaking at the connection end with a simple structure. While possible liner materials include thermoplastic resin, rubber, and metal, when used in food processing machinery or medical equipment, it is preferable to use a material that is safe from a food hygiene perspective 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, as necessary, other resins, rubber / elastomer components, additives, etc. Examples of other resins include polyethylene-based resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene (LLDPE), ethylene-based 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-based resin, poly-4-methyl-pentene-1-based resin, polystyrene-based resin, polyester-based resin, polyamide-based resin, polyphenylene ether-based resin, polyacetal-based resin, and polycarbonate-based 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 having 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, antiozonants, 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, carboxylic acid ester, phosphate 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 alcohols include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, oleyl alcohol, erucyl alcohol, and 12-hydroxystearyl alcohol.

[0035] Examples of the fatty acids 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 diethanolamide.

[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 hydroxycarboxylic 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 carboxylic acid esters include glycerin monooleate, glycerin dioleate, polyethylene glycol monostearate, and citrate distearate.

[0039] Examples of the above 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 whose main units are structural units derived from acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and other acrylic acid esters, and structural units derived from methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and other methacrylic acid esters. 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 metal sulfonate include sodium stearyl sulfonate, sodium lauryl sulfonate, sodium dodecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate, potassium stearyl sulfonate, potassium lauryl sulfonate, dibutyl sodium sulfosuccinate, di-2-ethylhexyl sodium sulfosuccinate, disodium lauryl sulfosuccinate, and polyoxyethylene 2-sodium lauryl sulfosuccinate.

[0042] Examples of the metal salt of an acid ester 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 fluorine-containing resins include polymers having as their main unit a structural unit derived from a fluorine-containing compound such as tetrafluoroethylene, hexafluoropropylene, fluoroalkylethylene, and perfluoroalkylvinylether; fluorine-containing alkylacrylates such as perfluoroalkyleneacrylate and perfluoromethalkyleneacrylate; and fluorine-containing alkylmethacrylate. 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 vehicles; various construction 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 automotive 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 machinery, hoses for beverage-related machinery, and hoses for chemical plants. Examples of suitable hoses include hoses for various industrial machinery and vehicles, such as hoses for scientific equipment, spinning machines, packing machines, printing machines, transmission machines, water treatment equipment, fluid elements, industrial robots, industrial vehicles, agricultural machinery, construction machinery, machine tools, injection molding machines, labor-saving machines, air tools such as air drivers and air hammers, moving parts, pneumatic / electrical signal hoses, pneumatic / signal hoses, hoses for equipment requiring heat resistance, high insulation, and high frequency characteristics, spot welding equipment hoses, 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; and hoses for medical equipment, such as various infusion hoses and intake / exhaust hoses. Milking hoses are particularly preferred.

[0046] The silicone rubber hose H1 according to the present embodiment described above can achieve the following effects. That is, the silicone rubber hose H1 according to the present embodiment firmly holds the reinforcing material when the diameter of the silicone rubber hose H1 is reduced by tightening the fastener, preventing the reinforcing material from coming loose. Therefore, compared to conventional hoses in which the reinforcing material is prone to coming loose, the pressure resistance of the entire hose can be maintained at a high level, preventing rupture, and reducing manufacturing costs compared to hoses in which the adhesion between the inner and outer layers is improved by applying a silicone rubber 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 hose's rigidity against twisting and preventing it from collapsing due to twisting. It also has high durability against chemical cleaning during milking, ensuring a long life. When used in industries that require chemical cleaning, not just milking, the product can be used with a much longer lifespan 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 formed by spirally winding a wire 4 as a reinforcing material between an inner layer 1 and an outer layer 2 to form a coil, thereby integrating the two layers. The rest of the configuration is the same as that of the first embodiment, and therefore 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 guiding it from a coil forming machine or 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 from 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 force of the coiled reinforcing material is 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.

[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 the viscoelastic recovery rate to the permanent set rate (viscoelastic recovery rate / permanent set rate) of the silicone rubber constituting the silicone rubber hose was determined by the following procedures (i) to (iv): determining the amount of elongation deformation, the amount of recovery from stress residual deformation, and the amount of residual strain; and then calculating the viscoelastic recovery rate and the permanent set rate using the following formulas (1) and (2). (i) The silicone rubber was press-molded at 160°C and then subjected to a curing reaction in an environment of 200°C for 2 hours 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) according to JIS-K-6251 was produced. (iii) The produced test piece was subjected to the following procedures using a tensile tester (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 stretching deformation rate of 100% (gauge length = 80 mm) (stretching deformation amount = 40 mm). (b) Immediately after stretching the test piece, the test piece was retracted at a crosshead speed of 500 mm / min until the tensile stress reached zero. (c) The gauge length when the tensile stress of the test piece reached zero was measured, and the difference between the measured gauge length and the gauge length of 80 mm when the stretching deformation rate reached 100% was calculated, and this value was used as the stress residual deformation recovery. (iv) The test piece whose tensile stress reached zero was immediately left at a temperature of 23°C in a free state for 5 minutes after the tensile stress reached 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 used as the 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 strain amount / elongation deformation amount)×100 (2)

[0054] 2. Hardness Before curing, Millable 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 2 mm. The durometer hardness (Duro-A) of the sheet was measured in accordance with JIS-K-6253.

[0055] 3. Kink Resistance A 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 the kink resistance was evaluated according to the following criteria.

[0056] 4. Presence or absence of loosening 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 closed by tightening with a band. Air was continuously supplied into the hose from the other end, and the state of the reinforcing material when the hose burst due to pressure from inside the hose was confirmed and evaluated according to the following criteria.

[0057] 5. Tear Strength Uncured millable silicone rubber was press molded at 160°C, and then cured for 2 hours in an environment of 200°C, after which the tear strength was measured in accordance with 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 several dairy farms (Dairy Farms A to D) and monitored and evaluated during routine milking operations. These milking hoses were loaned for monitoring purposes without disclosing information such as their composition, and all were collected after the monitoring period. Note that "hardness" in Table 1 refers to durometer A hardness. "Hose properties" in Table 1 refer to the ratio of viscoelastic recovery to permanent set (the above-mentioned formula (1) / formula (2)).

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

[0060] Regarding the "reinforcement method" in Table 1, "1" indicates a silicone rubber hose manufactured using the reinforcing method shown in the first embodiment, and "2" indicates a silicone rubber hose manufactured using the reinforcing 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]

[0062] According to the monitor evaluation, the silicone rubber hoses of Examples 1 to 6 were evaluated 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 device.

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

[0064] The "kink resistance" in Table 2 was evaluated according to the following criteria: ◯: The outer diameter of the hose wound around the cylindrical body was 50% or more of the original outer diameter. △: The outer diameter of the hose wound around the cylindrical body was 30% or more but less than 50% of the original outer diameter. ×: The outer diameter of the hose wound around the cylindrical body was 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. If a portion of the hose wall hardened or deformed, causing problems in use, the hose wall broke and began to leak, or cracks became noticeable in the hose wall, the hose was deemed to have reached the end of its life and was rated as x. If no cracks or other defects were observed and the hose was still usable as a hose, but if some hardening or deformation was observed in the hose, the hose was rated as △. If no such notable findings were observed and the hose was the same as the original hose, the hose was rated as ○. Naturally, some hoses deteriorated before the four months had passed.

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

[0067]

[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 each Comparative Example produced samples rated △, and samples that had reached the end of their life and were rated × in one 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 × during the four-month monitoring period.

[0069] As shown in Table 2, it was found that the silicone rubber hoses of each Example had superior kink resistance and a longer lifespan than the hoses of Comparative Examples 1 to 4. Furthermore, the silicone rubber hoses of each Example were more resistant to rupture than the hose of Comparative Example 2, with no loss of reinforcing material, and could be used for milking operations for a long period of time, making them highly economical.

[0070] When the silicone rubber hoses of the examples are used as milking hoses, deterioration occurs in relation to their use during cleaning. Milking hoses are frequently cleaned internally after use to prevent the growth of dirt and bacteria. This internal cleaning process uses a high-temperature (60-80°C) cleaning solution containing acid or alkali. To improve cleaning efficiency, the cleaning solution is not only continuously circulated during cleaning, but also intermittently pumped into the hose in a powerful, spray-like fashion using the negative pressure of the milking machine. During this cleaning process, the silicone rubber hose assumes a bent position. While the high-temperature cleaning solution that flows into the hose in a powerful, spray-like fashion rarely impacts the hose walls in straight sections, it impacts violently in curved sections. This results in specific areas of the silicone rubber hose being severely exposed to the high-temperature cleaning solution. Therefore, the bent portions of the silicone rubber hose are prone to deterioration during cleaning.

[0071] 1 Inner layer 2 Outer layer 3 Braid 3a Warp knitting row 3b Weft knitting row 4 Wire H1, H2 Silicone rubber hose

Claims

1. A silicone rubber hose manufactured using silicone rubber with excellent elasticity, with a reinforcing material wound between an inner layer and an outer layer, wherein 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 set amount) / elongation deformation amount}×100...(1) Permanent set rate=(residual set amount / elongation deformation amount)×100...(2) 2. The silicone rubber hose according to claim 1, which satisfies the following formula (3): Durometer A hardness of the silicone rubber constituting the inner layer - Durometer A hardness of the silicone rubber constituting the outer layer ≧ 10 ... (3) 3. A silicone rubber hose as described in claim 2, in which 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 knit rows of the knitted reinforcing material are wound in a spiral shape at a predetermined angle from the axial direction of the silicone rubber hose, and the weft knit rows are wound in a spiral shape so as to be perpendicular to the warp knit rows.

4. The silicone rubber hose according to claim 2, which 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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