CA1043717A - Composite reinforced hose - Google Patents

Abstract

COMPOSITE REINFORCED HOSE

Abstract of the Disclosure A composite reinforced hose for conveying fluids under pressure is provided with a core tube simultaneously coextruded from at least two thermoplastic synthetic resins having different physical properties and melt fused together in layers relative to each other to provide maximum benefit from the more desirable properties of each of the resins, a fibrous reinforcing material about the core tube and a pro-tective synthetic resinous sheath over the fibrous material.
Examples of thermoplastic synthetic resins suitable for making the inner layer of the core tube are a co-segmented polyester, a thermoplastic aromatic polyester or mixtures thereof, mix-tures of a segmented co-polyester and a thermoplastic poly-urethane, mixtures of an aromatic polyester and a polyurethane and mixtures of a polyacetal and a polyurethane. Examples of resins suitable for the outer layer are polyvinyl chloride, co-segmented polyester and thermoplastic polyurethane.

Description

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This invention relates generally to composite rein-forced hose adapted to convey fluids under pressure and more particularly to an improved hose of this type of construction which has certain advantageous physical properties for use in a particular application without substantial compromise of other desirable physical properties.
Composite hoses are used extensively to conduct fluids under pressure. The conventional flexible hydraulic hose has a core tube extruded from a single synthetic resin, a fibrous rein~orcing material about the core tube to support it against radial expansion and elongation and a synthetic resinous pro-tective sheath covering the fibrous material. Composite hoses of this type are disclosed, for example, in U.S. Patents -3,062,241; 3,332,447; 3,334,165; 3,251,381; 3,116,760 and ~ ~
3,722,550. Such composite hoses shoul~ be flexible, sub- ~ -stantially kink resistant and also have a burst strength which permits their use ~ith fluids under relatively hi~h pressure.
Moreover, the hose should be substantially resistant to chemical attack by the fluid carried thereby. As indicated by the dis-closures in the above patents, ~arious kinds of synthetic resins have been proposed for making the different components of the hose. The choice of synthetic resin used for making the core tube, for example~ may vary from one hose to another depending upon the relative importance of the physical properties. For example, it may be desirable to select a resin like nylon 11 for the core tube where resistance to chemical attack by the fluid carried by the hose is essential. Unfortunately, hoses having a nylon 11 core tube are not as flexible as hoses .

3~17 having a core tube madP from another resin such as poly-urethane. However, polyurethane is not as resistant to attack by some fluids as nylon. So in deciding between a nylon and polyurethane for a core tube, it is necessary to ~ -compromise one property in favor of another. In some hoses it is desirable to bond the core tube to the fibrous rein-forcing material. Polyurethane is advantageous for the core tube of the bonded hose because it can be treated with a solvent to soften the surface of the core tube to form an adhesive which bonds the fibrous strands to the core tube. ~ -The polyurethane core tube can be used only in those hoses, however, where the polyurethane provides sufficient chemical resistance to permit the hose to carry the fluid involved.
Hence, with the prior art hoses it has been the practice to select a core tube which has the most necessary properties and to tolerate a compromise in other somewhat less important properties. Such a procedure of cou:rse can not provide a hose having optimum properties for many industrial applications.
It is therefore an object of this invention to provide an improved composite reinforced hose for conveying fluids under pressure which has those properties most necessary for proper functioning without a major sacrifice in some of its other properties. A more specific object of the invention is to provide a composite reinforced hose adapted to convey fluids under pressure having a structure which permits a greater lati- ~-tude i~ selecting the various components of the hose to meet the various conditions to which the hose is likely to be sub~
jected. Still another object of the invention is to provide a

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composite hose which combines optimum flexibility, kink resistance, resistance to chemical attack and other desir-able properties. A still further object of the invention is to provide a composite reinforced hose having a core tube which has the better properties of a plurality of thermoplastic synthetic resins without substantial compro~
mise of other properties of the tube. A more specific object of the invention is to provide improvements over the hydraulic hoses of the prior art.
Other objects will become apparent from the following description with reference to the accompanying drawing wherein Figure l is a fragmentary side elevation, partially -~
cut away, of one embodiment of the invention; and Figure 2 is a cross-section taken along the line 2-2 of Figure l.
The invention described in our aforesaid Canadian Application Serial No. 217,401 provides a composite reinforced hose having a core tube shaped from at least two layers of synthetic thermoplastic resin which have different physical properties melt fused directly together at an inter- ~ -face into a wall which acts as a unitary structure, one or more layers of a fibrous reinforcing material disposed about ;~
the core tube and a protective synthetic resinous sheath dis-posed about the fibrous reinforcing material.
The invention broadly contemplates composite reinforced hose having a core tube of two or more layers of synthetic resin having different physical properties fused together into .. `':

~7~7 a single wall which will not separate into layers under the conditions to which the hose is subjected while functioniny as a hydraulic hose, an~ suitable fibrous reinforcing material about the core tube and an external protective sheath.
The inventiGn described in our aforesaid Canadian Application Serial No. 217,401 and the invention newly des-cribed herein permit the manufacture of a composite reinforced hose having some particularly desirable property without sub-stantial compromi~e of other desirable properties. For exam-ple, a substantially chemically resistant polymer such as nylon may be chosen for the inside layer of the core tube wall and a layer of a more flexible polymer such as an elas-tomeric polyurethane may be fused thereto as the outer sur-face to provide improved flexibility and kink resistance.
The outer layer may be shaped from a resin from which an adhe-sive can be made with a polar solvent to adhesively bond the core tube to the reinforcing material and to improve the strength of the hose. In such a hose, the relative thickness of the nylon and polyurethane may be varied to further modify the properties of the hose. In another embodiment of the in~
vention the inner layer of the core tube wall may be a solvent resistant thermoplastic polymer fused to an outer layer which forms the external surface of the core tube and has particles of a conductive material such as carbon black dispersed there-in to provide a hose for use in an airless high pressure paint spray system. Hoses in which the core tube has a substantially non-porous inner portion fused to a foam plastic or porous outer portion may also be provided in accordance with the in-vention.

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The core tube may be fabricated by any suitable pro-cess which will produce melt fusion of two different layers of synthetic thexmoplastic resins together to the extent that the two layers will not separate at the interface under elon- -gation and other conditions to which the hose will be exposed.
The most practical method of making the core tube is to supply two different synthetic thermoplastic resins or two different types of the same thermoplastic resin to a single extrusion head from different extruders operating under conditions whereby the resin which will be the inner portion of the core tube is still molten when the molten resin for the other por-tion of the core tube wall is applied thereover and the two molten synthetic resins are extruded through the same extru-sion die.
It has been found that two layers of selected thermo-plastic synthetic resin will melt fuse together along the in-terface and become so firmly bonded together that the core tube will not delaminate in a hose used to convey fluids under high pressures even if the physical properties of the two layers are significantly different. For example, nylon 11 and a the~moplastic polyurethane will melt ~use together in accor-dance with the process of the invention. Hence, the invention - -contemplates a hose having a core tube with a layer of nylon 11 melt fused to a layer of thermoplastic substantially non- -porous polyurethane. Usually, the nylon 11 layer will be the innermost layer because of its chemical resistance. The polyurethane layer imparts flexibility to the hose and may also be used for making an adhesive to bond the core tube to 37~

the fibrous reinforcing layer so it is usually disposed on the outside of the core tube.
Nylon 12 and thermoplastic polyurethane layers will also melt fuse together. Because of its chemical resistance -the nylon 12 layer may be used as the inner layer of a core tube with a thermoplastic polyurethane outer layer.
The invention also provides composite reinforced hoses having a core tube of two or more layers of synthetic resin of the same general chemical composition but modified to provide different physical properties. For example, a relatively hard thermoplastic polyurethane having a hardness of Shore D 50 to 60 and a relatively soft thermoplastic poly-urethane having a hardness of Shore A 80 to 95 may be co-extruded to form a core tube. The harder thermoplastic poly- ~-urethane has better chemical resistance than the softer one so the harder one is usually the inner layer of the core tube.
The pres~nce of the layer of softer polyurethane improves the flexibility o~ the hose. -Still another hose provided by the invention has a -~-core tube in which the innermost layer is a segmented co-polyester such as "Hytrel" having a haraness of about Shore D
55 and an outer layer of segmented co-polyester such as "Hytrel"
having a hardness of about Shore A 90. Such a hose has advan-tageous physical properties at elevated temperatures.
In another embodiment of the invention, a breathing hose which must not only be 1exible and kink resistant but must also be capable of carrying a ~luid without contamination by the core tube is provided with a core tube having a layer 37~L~
of unplasticized nylon 11 on its inside and a layer of plasti-cized nylon 11 on its outside.
~ hose suitable for conducting paint under high pres-sure may be provided in accordance with the invention with a core tube having an inner layer of nylon 11 or nylon 12 and a layer of thermoplastic polyurethane containing carbon blac]c particles melt fused to the nylon 11 or 12 layer. The nylon layer provides solvent resistance for conveying the paint in the core tube and the polyurethane containing carbon black particles is a semi-conductor for conducting static electric charges to ground. In a variation of a hose of this type the inner layer may be nylon 11 and the outer layer nylon 11 having carbon black dispersed therein.
The core tube may be adhesively bonded to the surface of the reinforcing material by the application of an adhesive material or by activating the surface of the core tube with a `~
solvent or softenin~ agent to form an adhesive in situ from the resin on the outer surface of the core tube. For example, -`
a polyurethane surface of a core tube may be activated by wetting it with a suitable polar solven~ such as, for example, ~ `
N-methyl pyrrolidone or the like. The rein~orcing fibrous material is then applied under tenslon about the wet core tube whereby the strands of reinforcing material become em~
bedded and partially encapsulated by the softened core tube material. In this way, the fibrous reinforcing layer becomes bonded to the core tube and the strength of the hose is improved.

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~ ~3 4 37 1 7 "Hytrel" is a synthetic resin sold by E.I. duPont de Nemours and Company. "Hytrel" is a segmented co-polyester and is described n U.S. Patent 3,766,146.
It has been found that simultaneously coextruded pro-perly selected synthetic thermoplastic resins of different physical properties will become bonded together by melt fusion and that an intermediate adhesive is not necessary. For ex-ample, nylon will fuse to a thermoplastic elastomeric poly-urethane if the two molten synthetic resins are fed separately to an extrusion head and coextruded one over the other while still molten. In those instances where one layer of the core tube is difficult to melt fuse to another layer an intermediate layer of a third synthetic resin which will melt fuse to both layers may be interposed therebetween.
It has been unexpectedly discovered that the core tube having two or more layers of synthetic thermoplastic resins of different physical properties has an elongation at break which is about equal to that of the more flexible resin in-stead of an average of the two elongations or near that of the resin having the lower elongation. In other words, the melt fused layers remain melt fused together and break to- ;
gether at the break point of the resin having the greater elongation. For example, a core tube was prepared by extrud-ing a layer of nylon ll, 0.020 inch thick and while the nylon 11 was still molten, extruding a layer of thermoplastic -polyurethane 0.025 inch think over the nylon ll layer. The two layers were melt fused together.

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With the same apparatus, a core tube of a single layer of the same nylon 11 having a wall-thickness of 0.020 inch was extruded and another core tube having a wall-thick-ness of 0.025 inch was extruded from the same polyurethane as used to make the dual extruded tube.
Test samples were cut from all three samples and the elongation at break was determined. Surprisingly, the elonga-tion at break of the laminated core tube was comparable to that of the polyurethane core tube. The following experimen-tal results were obtained: -n = number of samples tested X = average elongation, percent S = standard deviation of population, percent CI = 95 percent confidence interval, percent ~ -Polyurethane Nylon 11Composite Tube ;
n 9 10 10 ~ ~
X 419 351 423 ~-S 14 30 19 -~

The confidence interval tells us that there is only one chance in twenty that the total population average lies outside this range. The confidence interval for the composite tube elonga- `~
tion is substantially higher than the range for the all-nylon tube, while it overlaps the range for the all-urethane tube.
The elongation at break of the composite tube is at least 9.9 --percent (and probably 20.5 percent) better than the elongation of the all-nylon 11 tube extruded under the same conditions.

Other combinations of synthetic resins which may be simultaneously co-axially extruded to form a core tube having two or more layers melt fused together are segmented co-poly-esters such as "Hytrel" and polyvinyl chloride compound and a segmented co-polyester and a substantially non-porous thermo-plastic polyurethane, and a mechanical mixture of an aromatic polyester such as poly(tetramethylene terephthalate) and a segmented co-polyester as one layer and polyvinyl chloride polymer as the outer layer. The laminated core tubes com-bining a layer of "Hytrel" or a mixture of a segmented co-polyester and an aromatic polyester and a layer of polyv.inyl chloride compound or polyurethane will usually have the layer containing the segmented co-polyestex on the inside. A mech-anical mixture of segmented co-polyester and polyurethane may also be used for one of the layers, usually the outer layer.
The inner layer of the core tube may be a mixture containing from about 5 to about 95% by weight polyurethane and 95 to 5% by weight aromatic polyester in combination with any of the outer layers disclosed herein. The inner layer may also be a mixture of polyacetal and polyurethane in combination ~ -~
with any of the outer layers.
Examples of suitable thermoplastic aromatic polyesters are "Valox", aromatic polyester sold by the General Electric Co., "~enite", aromatic polyester sold by Eastman Kodak Co.
and "Celanex", aromatic polyester sold by Celenese Plastics Co.
Any suitable relative proportions of aromatic poly-ester such as "Valox'i and segmented co-polyester such as ~LV'~3ri' ;~L7 "Hytrel" may be used in the mixtures thereof extruded to form a layer of the core tube. For example, from about 5~
to about ~0~ by weight aromatic polyester such as "Valox" may be used. Any suitable mixture of polyurethane and co-segmented polyester may be used, but it is preferred to use from about 99% to about 50~ thermoplastic polyurethane and 1% to about 50% by weight co-segmented polyester.
Referring now to the drawing, a composite hose 10 is illustrated in Figures 1 and 2. The composite hose 10 has a core tube 17 formed by the simultaneous coextrusion of a layer of nylon 11 about 0.020 inch thick and a thermoplastic ~ ;
elastomeric polyurethane 12 such as "Pellethane" 90 A outer layer about 0.025 inch thick. The two synthetic resins be-come fused together at the interface to form a core tube which will not delaminate when the hose 10 is used or conveying a fluid under pressure. The outer surface of polyurethane of core tube 17 is wet with N-methyl pyrrolidone to form ln situ a gel-like material 13 on the surface thereof. A reinforcing layer 14 of poly(ethylene terephthalate) ester filaments is braided under tension around the core tube while the surface of coxe tube 17 is activated by the solvent. The filaments becoma embedded and partially encapsulated in the surace of `
the core tube 17 forming an elastomeric bond of the fibrous reinforcing material with the core tube. A second reinforcing layer 15 may be applied over layer 14. A protective poly-urethane sheath is applied over fibrous reinforcing layer 15 by extrusion of a thermoplastic elastomeric polyurethane there-over.

1~3717 Any of the other core tubes disclosed as suitable herein may be substituted in the foregoing embodiment of the invention for core tube 17 and the core tube 17 may or may not be bonded to the reinforcing layer depending upGn the particu-lar requirements of the hose. For example, in some embodiments of the invention the innermost layer of core tube 17 may be a segmented co-polyester such as "Hytrel" and an outermost layer of polyvinyl chloride polymer. Alternately, a mechanical mix-ture of a thermoplastic aromatic polyester such as "Valox 310"
and a segmented co-polyester may be extruded as the innermost layer and polyvinyl chloride polymer simultaneously coextruded to form the outermost layer of core tube 17~ The mixture of thermoplastic aromatic polyester and segmented co-polyester ~ -may also be used as the innermost layer of core tube 17 with a polyurethane or segmented co-polyester outer layer or two mixtures of aromatic polyester and s~egmented co-polyester having di~erent proportions of the components may be coex-truded to ~orm the inner and outer layers.
The polyurethane sheath 16 and the polyurethane 12 of core tube 17 may be extruded from any suitable thermo- -plastic polyurethane such as the one sGld under the trademark "PELLETHANE" by the Upjohn Company. The thermoplastic poly-urethane disclosed in U.S. Patents, 3,116,760 and 3,722,550 and disclosed in the book by Saunders and Frisch, entitled "Polyurethanes: Chemistry and Technology", published by Interscience Publishers, copyright 1964, may also be used.
Reaction products of poly(tetrameth~lene ether) ~lycol, suitable chain extender such as 1,4 butane diol, and 4,4' :, , :

i~4.~7 diphenylmethane diisocyanate and polyurethanes prepared by reacting an inner ester such as poly te-caprolactone) ester and a suitable chain extender such as 1,4 butane diol with an aromatic diisocyanate such as 4,4'-diphenylmethane diiso-cyanate are preferred. The sheath 16 may also be extruded from any other suitable synthetic resin such as, for example, nylon or segmented co-polyester.
The fibrous reinforcing material may be formed by braiding or by helically winding filaments of any sui~able ~-synthetic resinous material, such as, for example, a poly- `
(alkylene terephthalate)ester fibrous reinforcing material is disclosed in U.S. Patent 3,062,241. Such fibers have a tenacity of about 7 to about 11 grams per denier and an elongation at break of about 9% to about 17%. In a preferred embodiment of the invention, the hose is provided wlth a re-inEorcing layer of braided or helica:Lly wound filaments having a tenacity of at least 12 grams per denier and up to about 25 grams per denier and an elongation at break of from about 2 to about 7%. An aromatic polyamide fiber marketed by E. I.
2~ duPont de Nemours & Co. under the trademark "Kevlar" and known variously in the art as "Fiber B" and as an aramide filament may be used. A fibrous reinforcing material of aromatic polyamide fibers is preferred for composite hoses having a high burst strength.

,, ': . ; -3~7 The core tube can be shaped by extrusion with any suitable extrusion apparatus having a separate extruder for feeding each synthetic thermoplastic resin to a single extru-sion head.
In one embodiment of the invention a hose having a 3/8 inch I.D. core tube 17 has an inner layer extruded rom ~-a mixture containing about 90 parts "Hytrel" segmented co-polyester and 10 parts "Valo~ 310" poly(tetramethylene tere-phthalate)ester. Another layer about 0.010 inch thick of thermoplastic polyurethane simultaneously co-axially extruded with the "Hytrel" and "Valox" mixture is melt fused to the inner layer. A single layer 14 of braided fibers of poly-(ethylene terephthalate)ester is disposed about the core tube 17 and bonded thereto. The fibxous reinforcing layer is bonded to core tube 17 by solvating the surface of the polyurethane with N-methyl pyrrolidone and braiding the fibers on the wet core tube. A polyurethane sheath 16 about 0.025 inch is extruded over layer 14 and bonded thereto. The re-sulting hose has an O.D. of 0.65 inch, a burst strength of about 10,000 psi and can be bent to a radius of 0.75 inch without kinking. A hose having a core tube of a single layer of nylon and otherwise the same as the one just described, has a minimum bend radius without kinking of about 1.75 inch.
A load of about 12 pounds is required to bend the described embodiment of the invention having a core tube with an inner layer of "Hytrel" and "Valox" and an outer layer of polyure-thane 180 about a radius of 2 l/4 inch while 17 pounds are ~;
required to similarly bend the hose having a single layer nylon core tube.

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3~7 In another embodiment of the invention, a hydraulic hose has a core tube 17 with an I.D. o~ 1 inch. The core `~
tube 17 is formed by simultaneously co-extruding an inner layer of a mixture of 85 parts "Hytrel" segmented co-poly-ester and 15 parts "Valox 310" poly(tetramethylene terephtha-late)ester 0.045 inch thick and an outer layer of polyvinyl chloride polymer about 0.030 inch thick. A single layer 14 of poly(ethylene terephthalate)ester fibers is braided about core tube 17 and bonded thereto with a solution of about 18 parts polyurethane dissolved in 82 parts methylene chloride `; ~ `
solvent. A polyurethane sheath 16 is extruded over the ~
fibrous reinforcing layer 14 and bonded thereto. The O.D. ~ ~-of the hose is about 1.45 inches. The burst strength is about 6800 psi and the minimum bend radius without kinking is about 4 inches. The hose is more flexible than a hose having a single layer nylon core tube as illustrated by the fact that a load of 22 pounds will bend the hose of the inven~
tion 180 about a ~ 1/2 inch radius while a load of 31 pounds is required to similarly bend the hose having a nylon core tube.
It is apparent from the foregoing that the composite reinorced hose provided by the invention has the advantage over prior art hoses that a synthetic resin can be placed in the core tube where its particular physical properties are most needed without materially compromising other properties ~ ~
of the hose. For example, the synthetic resin for the inner ~ ~ -layer of the core tube may be chosen or its chemical resis-tance or to provide the hose with both chemical resistance :.: : ;~. .. . :
.. - , ,.. ... ' i ., ,: ' ' ' ' ' : : '' ''~ , , 1~37~7 and tensile strength while a more flexible synthetic resin is chosen for the outer layer of the core tube to maintain overall flexibility. The invention also permits variation of the thicknesses of the layers of the core tube to provide the hose with a particular property. The layers of the core tube may also be chosen to provide novel combinations of properties such as chemical resistance with electrical con-~ `
ductivity or insulation~ The cost of the hose can also be reduced by using only a relatively thin layer of the more costly but desirable synthetic resin only on that surface of the core tube where it is needed. It is also possible ~ -to provide a substantially non-porous synthetic resin layer in combination with a foam layer such as a polyurethane foam `
layer. By proper selection of the combination of layers of resins used in the core tube, it is also possible for kink `
xesistance in combination with a reinforcing material bonded to the sheath.
Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without de-parting from the spirit and scope of the invention except as it may be limited by the claims.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composite reinforced hose for conveying fluids under pressure comprising a core tube, a fibrous reinforcing material about the core tube and a protective sheath over the fibrous material, said core tube having been simultaneously coextruded from at least two thermoplastic synthetic resins having different properties to form two layers melt fused directly together, said hose having (1) a core tube comprising an inner layer of segmented co-polyester and an outer layer of polyvinyl chloride compound, or (2) a core tube having an inner layer of a mixture of segmented co-polyester and a thermoplastic aromatic poly-ester and an outer layer of polyvinyl chloride compound, segmented co-polyester, polyurethane or a mixture of seg-mented co-polyester and polyurethane, or (3) a core tube having an inner layer of a mixture of polyurethane and a segmented co-polyester and an outer polyurethane layer, or (4) a core tube having an inner layer of a mixture of a thermoplastic aromatic polyester and polyurethane and an outer layer of polyvinyl chloride compound, segmented co-polyester, polyurethane or a mixture of segmented co-polyester and polyurethane, or (5) a core tube having an inner layer of a mixture of polyacetal and polyurethane and an outer layer of polyvinyl chloride compound, segmented co-polyester, polyurethane or a mixture of segmented co-polyester and poly-urethane.

2. The composite reinforced hose of Claim 1 wherein the inner layer of the core tube is a segmented co-polyester and the outer layer is polyvinyl chloride compound.

3. The composite reinforced hose of Claim 1 wherein the inner layer of the core tube is a mixture of a segmented co-polyester and a thermoplastic aromatic polyester and the outer layer is polyvinyl chloride com-pound, segmented co-polyester, polyurethane or a mixture of segmented co-polyester and polyurethane.

4. The composite reinforced hose of Claim 1 wherein the core tube has an innermost layer of a mixture of segmented co-polyester and polyurethane and an outer layer of polyurethane.

5. The composite reinforced hose of Claim 1 wherein the outermost layer of the core tube has particles of electroconductive material distributed therein.

6. The composite reinforced hose of Claim 1 wherein the core tube is one having an inner layer of a mixture of a thermoplastic aromatic polyester and poly-urethane and an outer layer of polyvinyl chloride compound, segmented co-polyester, polyurethane or a mixture of seg-mented co-polyester and polyurethane.

7. The composite reinforced hose of Claim 1 wherein the core tube is one having an inner layer of a mixture of polyacetal and polyurethane and an outer layer of polyvinyl chloride compound, segmented co-polyester, polyurethane or a mixture of segmented co-polyester and polyurethane.

8. The hose of Claim 1 wherein the reinforcing material is bonded to the outer layer of the core tube.

9. The hose of Claim 1 wherein the sheath is bonded to the reinforcing material.

10. The hose of Claim 8 wherein the sheath is bonded to the reinforcing material.