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United States Patent [i9] Russell mi 4,196,464 {45] Apr. 1,1980 [54] SEMI-CONDUCTIVE LAYER-CONTAINING REINFORCED PRESSURE HOSE AND METHOD OF MAKING SAME [75] Inventor: David D. Russell, Ravenna, Ohio [73] Assignee: Eaton Corporation, Cleveland, Ohio [21] Appl. No.: 880,718 [22] Filed: Feb. 23,1978 [51] Iat CU......................... B32B 1/08; B32B 1/10; F16L 11/12 [52] UJS. CL.................................. 361/215; 138/103; 138/109; 138/125; 138/130; 138/137; 138/140; 138/141; 138/177; 156/149; 156/172; 156/244.13; 174/47; 174/98; 174/102 SC; 174/102 C; 264/173; 264/176 R; 428/36 [58] Field of Search.............. 138/124, 125, 137, 140, 138/141, 177, 145, 146, 130, 103, 109; 264/173, 176 R; 174/102 SC, 102 C, 47, 98; 428/36; 156/149, 172, 244; 361/215 [56] References Cited U.S. PATENT DOCUMENTS 3,042,737 3,166,688 3,290,426 3,405,398 3,473,087 3,828,112 7/1962 1/1965 12/1966 9/1975 10/1969 8/1974 Bnunbach et al................... 174/47 Rowand et al............ ....... 138/103 Barrentine................ ....... 138/103 Johansen et al........... ....... 138/140 Slade et al................ ......... 174/47 Johansen et al........... ....... 156/172 3,845,186 3,963,856 3,988,188 4,059,847 10/1974 Shaw.................................. 174/47 6/1976 Carlson et al........................ 174/47 10/1976 Johansen et al.................... 156/195 11/1977 Phillips et al......................... 174/47 FOREIGN PATENT DOCUMENTS 2103394 4/1972 Fed. Rep. of Germany ......... 138/103 45-32633 10/1970 Japan ................................... 174/47 Primary Examiner--James C. Cannon Attorney, Agent, or Firm--R. J. McCloskey; A. Chrow [57] ABSTRACT A fibrous reinforced flexible hose for conveying fluids such as paint under pressure is provided with a compos ite core tube preferably simultaneously co-extruded from two or more synthetic polymers which are in intimate contact with each other. The inner layer of the composite core tube is nylon or other chemical resistant polymer which may or may not be cross-linked and the outer layer is a cross-linked electrically semi-conductive synthetic polymer layer which serves as a ground for static electricity. In the process of making the hose, the semi-conductive layer is preferably cross-linked by irradiation as a means of improving its higher tempera ture performance capabilities and to minimize changes in the electrical resistance of the semi-conductive layer that might arise from dynamic use of the hose. 30 Claims, 2 Drawing Figures 16 10 CEL-1329 U.S. Patent Apr. 1, 1980 4,196,464 FIG. 2 4.196.464 12 electricity therebetween. The referenced hose differs SEMI-CONDUCTIVE LAYER-CONTAINING from that of the present invention in that it requires a REINFORCED PRESSURE HOSE AND METHOD highly electrically insulative layer to be disposed be OF MAKING SAME tween the fluid being conveyed and the semi-conduc- 5 five outer layer and further requires a metallic electrical This invention relates generally to composite tubing conductor wound in electrical contact about the semi- and more particularly to a hose for transmitting fluids conductive layer to drain off static electricity. under pressure in a spraying apparatus such as a paint It is therefore an object of this invention to provide spray. A portion of the subject matter of this application an improved flexible composite hose having a means is related in part to our co-pending application Ser. No. 10 incorporated therein for dissipating static electricity. 469,611 filed May 13, 1974 and Ser. No. 598,537 filed Another object of the invention is to provide a flexible July 23, 1975, and now abandoned, and is an improve composite hose for use with a paint spraying apparatus ment over our application Ser. No. 620,189 filed Oct. 6, or the like which is adapted for transmission of pulsat 1975. ing fluids and has a static discharge means which is Apparatus for spraying liquids such as paint is pro 15 conveniently incorporated in the hose and effectively vided with a pump and hose assembly for transmitting discharges static electricity throughout the life of the liquid under pressure from a supply tank to a spray gun hose. A further object of the invention is to provide a nozzle. An electrically conductive ground wire is usu flexible composite hose with a grounding means coex ally included throughout the length of the hose to drain tensive with the length of the hose which is not rup- off any static electricity developed at the spray nozzle 20 tured or otherwise broken by the pulsating and/or me of the hose to prevent sparking when it approaches a chanical action of the hose. A still further object of the conductor such as a steel beam or the like. A hose hav invention is to provide an improved flexible reinforced ing a flexible polymeric core tube, fibrous reinforcing pressure hose having a composite core tube having a material wound about the core tube and a protective semi-conductive material as its outer layer that is coex- sheath is used to convey the liquid at a pressure which 25 tensive with the length of the hose and which has been is sufficiently high to produce a spray. The hose must be cross-linked for improvement of its higher temperature capable of expanding radially under the pulsation of the performance capabilities and to minimize changes in the pump in order to act as an accumulator which attenu electrical resistance that might arise from dynamic use ates the pulses so as to minimize pulsating at the nozzle of the hose. Another object of the invention is to pro- and thereby produce a relatively smooth and uniform 30 vide a method of making an improved flexible rein spray of liquid. On electrical motor operated paint forced pressure hose having a composite core tube hav spray systems, the accumulator action also retards the ing a semi-conductive material as its outer layer that is rate of pressure change affecting the motor controlling coextensive with the length of the hose and which has pressure switch, thereby reducing the number of stops been cross-linked for improvement of its higher temper- and starts of the motor controlling the fluid pump. 35 ature performance capabilities and to minimize changes It has been proposed heretofore to wind a metallic in the electrical resistance that might arise from dy ground wire about the core tube as one of the braids of namic use of the hose. the reinforcing layer. However, the wire frequently Other objects will become apparent from the follow deteriorated under pressure and mechanical action and ing description with reference to the accompanying the abrasion of the braid by the wire sometimes resulted 40 drawing wherein in bursting of the hose. Additionally, such deterioration FIG. 1 is a cut-away side elevation, partially in sec of the ground wire resulted in large increases in its tion, of one embodiment of the invention; and electrical resistance or interrupted its electrical continu FIG. 2 is a cross-section taken along the line 2--2 of ity resulting in deminished or loss of ability of the hose FIG. 1. to dissipate static electrical charge. 45 The foregoing objects and others are accomplished in It is proposed in U.S. Pat. Nos. 3,445,583, 3,543,803 accordance with this invention, generally speaking, by and 3,780,208 to provide improved hoses for transmit providing a composite reinforced hose having a core ting liquids from a pulsating source with a metallic tube shaped from two layers of synthetic resinous mate grounding wire helically wound about the core tube rial which are in intimate contact with each other with and enclosed within a rupture resistant sleeve. While 50 the outer layer of the tube wall being a semi-conductive the disclosed hoses have been found to be adapted for cross-linked material, one or more layers of a fibrous successfully transmitting paints under most conditions, reinforcing material disposed about the core tube and a the inclusion of a grounding wire enclosed in a plastic protective synthetic resinous sheath disposed about the sleeve introduces additional steps in the manufacture of fibrous reinforcing material. The composite core tube the hose and it has been found in practice that the 55 has an inner layer made from a material (which may or ground wire still sometimes ruptures and the fragments may not be cross-linkable) adapted to resist chemical are not always confined sufficiently to maintain conti attack by the fluid conveyed by the hose and to provide nuity of the static discharge system. Also, the fragments electrical connection between the fluid contained may penetrate the core or sheath causing a premature within the core tube and an outer semi-conductive layer failure of the hose. 60 disposed about and coextensive with the outer surface It has also been proposed in U.S. Pat. No. 3,828,112 to of the inner layer. The coextensive cross-linked semi- provide a composite hose for the conveyance of paint conductive outer layer of the core tube serves as a having an electrical charge of generally more than 25 means for conducting static electricity generated on the kilovolts. The disclosed hose requires a combination of inner surface of the core tube inner layer by flow of the metallic reinforcement; semi-conductive layer; and a 65 fluid along the length of the hose to a suitable ground. highly insulative layer disposed between the semi-con The semi-conductive outer layer of the core tube also ductive layer and the electrically charged paint which is serves as a means for conducting static electricity gen capable of substantially preventing leakage of static erated at the spray nozzle head as a result of increased 4,196,464 34 flow of the fluid and to conduct it axially along the able for use in conveying paint having some particularly length of the hose to ground. The invention thus pro desirable physical property without substantial compro vides a flexible hose, particularly suitable for use in the mise of other desirable properties combined with a conveyance of paint, fuels, solvents, and the like, having means for effectively draining static electricity from the a synthetic resinous core tube, a fibrous reinforcing 5 hose. For example, a substantially chemically resistant layer about the core tube, a protective sheath about the polymer such as nylon may be chosen for the inside fibrous reinforcement layer and a grounding means layer of the core tube wall and a layer of a more flexible forming a part of the wall of the core tube. Although polymer such as an elastomeric polyurethane composi the composite core tube may be formed by covering the tion having electrically conductive particles dispersed inner layer with a non-metallic semi-conductive tape or 10 therein and which will cross-link by exposure to radia by spraying the inner layer with a conductive coating or tion may be fused thereto as the outer layer to provide by dipping the inner layer in a conductive resin, the improved flexibility, kink resistance and means for pre core tube is preferably formed by coaxially extruding venting sparking of static electricity at the nozzle of the two different extrudable synthetic polymers to provide hose. It has been found that cross-linking of the conduc a flexible tube having a wall of two synthetic resinous 15 tive outer layer of the composite core tube increases by layers. The two layers may be extruded in two separate 25 degrees Fahrenheit or more the temperature at extrusion steps or they may be simultaneously coex which hose embodiments of the invention can be used truded so that the layers are melt fused together. The and that changes in the electrical resistivity resulting conductive layer extends throughout the entire length from pressure pulsation and flexing during dynamic use of the hose and is in electrical contact with the fluid 20 of the hose appear to be minimized as a result of cross- being conveyed through the hose and with a grounded linking the outer semi-conductive layer of the compos hose fitting connected to the hose. The grounding layer ite core tube. is a synthetic polymer which is semi-conductive, i.e., it The core tube may be fabricated by any suitable si exhibits a volume resistivity of 109 ohm-cm or less. multaneous coaxial extrusion process which will pro In airless paint spraying processes, it is undesirable to 25 duce melt fusion of two different layers of synthetic accumulate more than 1400 static volts at the spray resins together to the extent that the two layers will not head of the spraying apparatus because of the danger of separate at the interface under elongation and other igniting the air-solvent mixture about the spray gun. conditions to which the hose will be exposed. The most Preferably a safety factor of 4:1 should be maintained practical method of making the core tube is to supply which means that the static voltage on the spray end of JO two different types of the same resin to a single extru the hose should not exceed 350 volts. The hose pro sion head from different extruders operating under con vided by this invention has a ground which is a cross- ditions whereby the resin which will be the inner por linked semi-conductive layer of polymer which will tion of the core tube is still molten when the molten drain off the static potential so a frightening or danger resin for the other portion of the core tube wall is ap ous electrical-arc between the spray gun and ground is 35 plied thereover and the two molten synthetic resins are avoided. extruded through the same extrusion die. Any suitable conductive synthetic polymer which It has been found that two layers of selected synthetic can be cross-linked after processing may be used. Pref resin with one being electrically conductive will melt erably, the semi-conductive synthetic polymer is one fuse together along the interface and became so firmly which will melt fuse to the polymer of the first layer 40 bonded together that the core tube will not delaminate when the two polymers are coaxially extruded. The in a hose used to convey fluids under high pressure even conductive polymer must have the required electrical if the physical properties of the two layers are signifi properties. While a semi-conductive polymer having a cantly different For example, nylon and semi-conduc volume resistivity after application and other process tive thermoplastic polyurethane composition having ing of as high as 100,000 ohm-cm at ambient tempera 45 particles of carbon black uniformly dispersed therein ture may be used, usually the volume resistivity will not and which will cross-link by exposure to radiation will be more than about 2000 ohm-cm. It is preferred to use melt fuse together in accordance with the process of the one having a calculated volume resistivity of not more invention. Hence, the invention contemplates a semi- than about 500 ohm-cm. In fact, best results have been conductive hose particularly useful for conveying paint obtained so far with a polymer having a volume resistiv 50 having a core tube with a layer of nylon melt fused to a ity of 40 or less ohm-cm. The volume resistivity may be layer thermoplastic substantially non-porous polyure calculated by the method described in "NFPA Journal thane composition which is subsequently cross-linked No. 77, Stadc Electricity, 1972". Examples of suitable by radiation. Usually, the nylon layer will be the inner polymers are ethylene-ethyl acrylate, ethylene-vinyl most layer because of its chemical resistance and its acrylate and thermoplastic rubber having the desired 55 ability to permit electrical interconnection between the volume resistivity but it is preferred to use a polyure fluid being conveyed through the hose and the semi- thane of the desired volume resistivity in hoses having a conductive outer layer disposed about the outer surface nylon inner layer where kink resistance is desirable of the core tube inner layer. because the polyurethane bonds well to the nylon and The invention also provides composite reinforced can be bonded to the reinforcing material. 60 hoses having a core tube of two or more layers of syn The semi-conductive polymer may have carbon par thetic resin of the same general chemical composition ticles, graphite particles, silver particles, copper parti but modified to provide different physical properties. cles or mixtures thereof or other suitable electrically For example, a relatively hard thermoplastic polyure conductive particles dispersed substantially uniformly thane having a hardness of Shore D 50 to 60 and a therein to provide the polymer with a volume resistivity 65 relatively soft thermoplastic polyurethane having a within the requirements of the hose. hardness of Shore A 80 to 95 may be coextruded to The invention permits the manufacture of a compos form a core tube. The harder thermoplastic polyure ite reinforced serai-conductive hose particularly suit thane has better chemical resistance than the softer one 4,196,464 56 so the harder one is usually the inner layer of the core ture and chemical resistance required; (3) is not electri tube while the softer one contains particles of an electri cally insulative to the extent that it prevents flow of cal conductor and is the outer layer. The presence of static electricity between its inner and outer surface the layer of softer polyurethane improves the flexibility and; (4) which may or may hot be cross-linked in the of the hose as well as providing a semi-conductor for 5 process of making the hose. static electricity. The core tube, if desired, may be adhesively bonded Other combinations of synthetic resins which may be to the surface of the reinforcing material by any suitable coaxially extruded simutaneously or in tandem to form means. Dependent upon the degree of cross-linking, a core tube having two or more layers are those dis hereinafter described, the reinforcing material may be closed in our application Ser. No. 598,537. For example, 10 bonded to the core tube by activating the outer surface segmented co-polyesters such as "Hytrel" as one layer of the semi-conductive layer with a solvating or soften and a polyvinyl chloride compound for the conductive ing agent to form an adhesive in situ from the resin on layer. A segmented co-polyester may be used for one the outer surface of the irradiated semi-conductive layer and a conductive substantially non-porous ther layer. For example, a polyurethane surface of a core moplastic polyurethane as the other layer. A mechani 15 tube may (dependent upon the degree of cross-linking) cal mixture of an aromatic polyester such as poly(tet- be activated by wetting it with a suitable polar solvent ramethylene terephthalate) and a segmented co-polyes- such as, for example, N-methyl pyrrolidone or the like. ter may be used as one layer and a conductive polyvinyl However, it is preferred to apply an adhesive material chloride polymer as the outer layer. The laminated core such as a hot melt or solvated type such as a solution of tubes combining a layer of "Hytrel" or a mixture of a 20 polyurethane between the outer surface of outer semi- segmented co-polyester and an aromatic polyester and a conductive layer and adjacent layer of fibrous reinforc layer of polyvinyl chloride compound or polyurethane ing material because of the cross-linking effect of radia will usually have the layer containing the segmented tion and because the use of a solvating agent to solvate co-polyester on the inside as the non-conductive layer. the outer surface of the semi-conductive layer may A mechanical mixture of segmented co-polyester and 25 disturb the uniformity of the distribution of electrically polyurethane may also be used for one of the layers, conductive particles and affect the electrical conductiv usually the outer layer. The inner layer of the core tube ity of the semi-conductive polymer layer. The adhesive may be a mixture containing from about 5 to about 95% may itself be of a type that can be cross-linked as part of by weight polyurethane and 95 to 5% by weight aro the process of making an embodiment of the hose of the matic polyester in combination with any of the outer 30 invention and as such contribute to its higher tempera layers disclosed herein. The inner layer may also be a ture resistance capabilities. mixture of polyacetal and polyurethane in combination It has been found that simultaneously coextruded with any of the outer layers. In these embodiments, as properly selected synthetic thermoplastic polymers will with all embodiments of the invention, the outer layer become bonded together by melt fusion even though contains particles which are electrically conductive and 35 one of the polymers contains particles of electrically the inner layer is such that it provides suitable chemical conductive material and that an intermediate adhesive is resistance in combination with an ability to permit the not necessary. For example, nylon will fuse to a radia flow of static electricity (originating from static poten tion cross-linkable thermoplastic elastomeric polyure tials generated on the inner surface of the inner layer as thane composition containing carbon black particles if a result of fluid flow therethrough) radially outwardly 40 the two molten synthetic polymers are fed separately to to the outer semi-conductive layer and thence axially an extrusion head and coextruded one over the other along the length of hose through the semi-conductive while still molten. In those instances where one layer of outer layer to ground. the core tube is difficult to melt fuse to another layer, an Examples of suitable thermoplastic aromatic polyes intermediate layer of a third synthetic resin which will ters are "Valox", aromatic polyester sold by the Gen 45 melt fuse to both layers and which will not interfere eral Electric Co., "Tenite", aromatic polyester sold by with the hereinbefore described flow of static electric Eastman Kodak Co. and "Celanex", aromatic polyester ity may be interposed therebetween but it is preferred to sold by Celenese Plastics Co. melt fuse the semi-conductive layer directly to the inner Any suitable relative proportions of aromatic polyes layer of the core tube. ter such as "Valox" and segmented co-polyester such as 50 Referring now to the drawing, a semi-conductive "Hytrel" may be used in the mixtures thereof extruded pressure hose 10 having a core tube I.D. of 0.25 inch is to form a layer of the core tube. For example, from illustrated in FIGS. 1 and 2. Hose 10 has a core tube 17 about 5% to about 60% by weight aromatic polyester formed by the simultaneous coaxial extrusion of layer such as "Valox" and 95% to about 40% by weight 11 of Nylon about 0.025 inch thick and an irradiation segmented co-polyester such as "Hytrel" may be used. 55 cross-linked semi-conductive thermoplastic elastomeric Any suitable mixture ofpolyurethane and co-segmented polyurethane composition outer layer 12 about 0.015 polyester may be used, but it is preferred to use from inch thick and containing carbon particles and having a about 99% to about 50% thermoplastic polyurethane volume resistivity at room temperature (about 20* C.) of and 1% to about 50% by weight co-segmented polyes about 20 ohm-cm. The two synthetic resins become ter. 60 fused together at the interface to form a core tube 17 Although it is preferred that hoses made in accor which will not delaminate when the hose 10 is used for dance with the invention utilize a composite core tube conveying a point under pulsating pressure. The outer having an extruded inner nylon layer whose outer sur surface of polyurethane of core tube 17 is wet with an face is melt-fused to the inner surface of an extruded adhesive solution 13 of a solvated polyurethane. A rein outer layer of polyurethane that is subsequently cross- 65 forcing layer 14 of nylon filaments is braided under linked, it is to be understood that the inner layer may be tension around the core tube while the adhesive on the made from any synthetic polymer which: (1) can be surface of core tube 17 is wet. The filaments become extruded into a tubular shape; (2) provides a tempera bonded to the surface of the core tube 17 forming an 4,196,464 78 elastomeric bond of the fibrous reinforcing material high energy electrons and the synthetic polymer of the with the core tube. A second reinforcing layer IS of outer layer contains sufficient radiation sensitizer to poly(ethylene terephthalate) ester is braided over layer effectively cross-link both the inner and outer layers of 14. A protective polyurethane sheath 16 about 0.025 the composite core tube during exposure to high energy inch thick is extruded over fibrous reinforcing layer 15 5 electron radiation. Any suitable source of high energy by extrusion of a thermoplastic elastomeric polyure electrons, such as an insulating core transformer, a reso thane thereover. Sheath 16 may be adhesively bonded nant transformer or linear accelerator may be used to to the surface of layer 15. provide the high energy electrons. Preferably, the en Any other core tube similar to those disclosed as ergy of the electrons should be at least 100,000 electron suitable herein may be substituted in the foregoing em 10 volts and seldom will more than 15 million electron bodiment of the invention for core tube 17 and the core volts be required. It is preferred that the required dos tube 17 may or may not be bonded to the reinforcing age to effectively cross-link either the outer layer or layer and successive reinforcing layers may or may not both inner and outer layers of the composite core tube be bonded together depending upon the particular re be effected in one exposure, but repeated exposures can quirements of the hose. 15 be made until the entire total dosage has been obtained. The polyurethane layer 12 of core tube 17 may be Although it is preferred to irradiate the composite core extruded from any suitable thermoplastic polyurethane tube prior to the placement of one or more layers of such as the one sold under the trademark "Pellethane" reinforcement and outer protective sheath thereabout, by the Upjohn Company or of the type disclosed and the composite core tube may be irradiated after it has claimed in U.S. Pat. No. 4,010,146 assigned to the as 20 been reinforced or protective sheath has been placed signee of the present invention. The polyurethane dis thereabout. closed in U.S. Pat. Nos. 3,116,760 and 3,722,550 and Although the protective sheath may be made from disclosed in the book by Saunders and Frisch, entitled any suitable flexible material resistant to conductance of "Polyurethanes.: Chemistry and Technology", published electrical current, it is preferred that the sheath be made by Interscience Publishers, copyright 1964 may also be 25 from a polymeric material which provides suitable flexi used. Reaction products of poly(tetramethylene ether)- bility in combination with suitable resistance to electri glycol, suitable chain extender such as 4,4'-diphenylme- cal conductance, abrasion, chemicals, cut through and thane diisocyanate and polyurethane prepared by react temperature. Although the protective sheath may be ing an inner ester such as poly(e-caprolactone)ester and made from a synthetic polymeric material such as, for a suitable chain extender such as 1,4 butane diol with an 30 example, nylon, thermoplastic rubber, rubber, thermo aromatic diisocyanate such as 4,4'-diphenylmethane plastic polyester, polyvinyl chloride, and the like, it is diisocyanate are preferred. The sheath 16 may also be preferred to make the outer protective sheath from a extruded from any other suitable synthetic resin such as, polyurethane such as hereinbefore described. The outer for example, nylon in some embodiments of the inven protective sheath may or may not be cross-linked. In tion. 35 cases where it is desired to cross-link by exposure to In accordance with the present invention, synthetic high energy electron radiation in the manner hereinbe polymers found suitable for use as the outer layer of the fore described. composite core tube are compounded to include suffi The fibrous reinforcing material may be formed by cient amounts of electrically conductive particles and braiding filaments or by helically winding strands of cross-linking agents and may or may not include addi 40 filaments of any suitable synthetic resinous material, tional additives such as, for example, heat stabilizers, such as, for example, a poly(alkylene terephthalate)es- processing oils, stabilizers, fillers and the like. Although ter, nylon, aromatic polyamide or the like or combina the cross-linking agents may be of the heat activating tions thereof. Suitable nylon fibrous reinforcing mate type such as used in a vulcanization process, it is pre rial is disclosed in U.S. Pat No. 3,334,164 while suitable ferred to use radiation sensitizers in the compositions so 45 poly(alkylene terephthalate)ester fibrous reinforcing that the semi-conductive outer layer of the composite material is disclosed in U.S. Pat. No. 3,062,241. Such core tube can be cross-linked by irradiation during the fibers have a tenacity of about 7 to about 11 grams per process of making the hose rather than use vulcaniza denier and an elongation at break of about 9% to about tion as the means of cross-linking. Although it is pre 17%. In one embodiment of the invention, the hose may ferred to extrude the inner layer of the composite core 50 be provided with a reinforcing layer of braided of heli tube from a thermoplastic polymer that is not cross-link cally wound filaments having a tenacity of at least 13 able the polymer of the inner layer may also include grams per denier and up to about 25 grams per denier cross-linking agents and other additives as iong as such and an elongation at break of from about 2% to about agents and additives do not interfere with the hereinbe 7% such as the aromatic polyamide fiber marketed by fore described characteristics required of the inner 55 E. I. dePont de Nemours & Co. under the trademark layer. If, for certain embodiments of the hose of the "Kevlar". Suitable reinforcing material containing syn invention, it is determined that the inner layer should be thetic aromatic polyamide filaments is disclosed in U.S. cross-linked, it is preferred to incorporate a suitable Pat. No. 3,905,398, issued on Sept. 16, 1975. A fibrous amount of a radiation sensitizer into both the inner layer reinforcing material of aromatic polyamide fibers may and the outer semi-conductive layer so that both can be 60 be used to advantage in composite hoses having a high cross-linked by exposure to radiation during the process burst strength. of making the hose. The composite core tube can be shaped by extrusion The presently preferred method of cross-linking the with any suitable extrusion apparatus having a separate semi-conductive outer layer of the composite core tube extruder for feeding each synthetic thermoplastic resin is similar to the method of making a flexible dimension- 65 to a single extrusion head. ally stable, hydraulic hose disclosed in our U.S. Pat. No. Although the invention has been described in detail 3,988,188. In the present invention, the composite core for the purpose of illustration, it is to be understood that tube is exposed to radiation preferably in the form of such detail is solely for that purpose and that variations 4,196,464 10 can be made therein by those skilled in the art without 16. The flexible hose of claim 1 wherein the poly departing from the spirit and scope of the invention. meric material of the inner layer is a cross-linked mate What is claimed is: rial. 1. A flexible hose for conveying and spraying a fluid 17. The flexible hose of claim 16 wherein the cross- which comprises 5 linked polymeric material of the inner layer is a radia a core tube through which the fluid flows under pres tion cross-linked material. sure, said core tube having a laminated wall with a first extruded lamina of a synthetic polymer adja 18. The flexible hose of claim 17 wherein the crosslinked polymeric material of the inner layer is a high cent to the fluid which resists chemical attack by energy electron cross-linked material. the fluid and which conducts static electricity radi- 10 19. In a method of making a flexible reinforced hose ally outwardly from the fluid and a second lamina for conveying fluids under pressure comprising a com disposed radially outwardly about the first lamina, posite core tube, one or more layers of fibrous reinforc said second lamina being a semi-conductive poly ing material disposed about the core tube and a substan mer which is in electrical contact with the first tially electrically non-conductive polymeric protective lamina, said semi-conductive polymer being a IS sheath disposed about the reinforcement material, said cross-linked polymer, said laminae being co-exten- core tube having a laminated wall with a first extruded sive throughout the length of the hose, lamina of a synthetic polymer adjacent to the fluid at least one layer of fibrous material disposed about the core tube and reinforcing it against bursting under pressure from the fluid, a substantially non-electrical conducting synthetic polymer sheath about the said fibrous material, and a spray nozzle on one end of the hose in electrical conducting contact with said semi-conductive lam ina and electrically connected to ground. 2. The flexible hose of claim 1 wherein the outer 20 25 which resists chemical attack by the fluid and which conducts static electricity radially outwardly from the fluid and a second lamina disposed radially outwardly about the first lamina, said second lamina being a semiconductive polymer which is in electrical contact with the first lamina, said semi-conductive polymer being a cross-linked polymer, said laminae being co-extensive throughout the length of the hose, the method including the steps of: (a) Extruding an inner layer of a suitable flexible semi-conductive layer is an extruded layer. synthetic polymeric material into an elongate tubu 3. The flexible hose of claim 1 wherein the extruded lar shaped form; inner layer and semi-conductive outer layer are melt (b) Forming an outer tubular shaped layer of cross- fused to provide the intimate contact therebetween. 30 linkable semi-conductive synthetic polymeric ma 4. The flexible hose of claim 1 wherein the synthetic terial coextensively about and in intimate contact polymeric material of the extruded inner layer is a nylon with the inner layer; and the cross-linked semi-conductive outer layer mate (c) Exposing the outer semi-conductive layer to an rial is a polyurethane. amount of radiation sufficient to cross-link the ma 5. The flexible hose of claim 1 wherein the semi-con- 33 terial; ductive outer layer polymeric material contains carbon (d) Disposing one or more layers of fibrous reinforce particles. ment about the outer semi-conductive layer; and 6. The flexible hose of claim 1 wherein the outer layer (e) Forming a protective sheath about the fibrous of cross-linked semi-conductive polymeric material has reinforcement material. an electrical volume resistivity at 20* C. of not more 40 20. The method of claim 19 wherein the cross-linka than about 2000 ohm-cm. ble semi-conductive outer layer is formed by extrusion. 7. The flexible hose of claim 1 wherein the polymeric 21. The method of claim 19 wherein the intimate material of the inner layer is a nylon and the outer semi- contact is provided by melt fusing the outer semi-con conductive layer is an extruded layer of a polyurethane ductive layer to the inner synthetic polymeric layer. composition containing carbon particles. 43 22. The method of claim 19 wherein the radiation is 8. The flexible hose of claim 1 wherein the fibrous provided by high energy electrons. reinforcement is bonded to the outer semi-conductive 23. The method of claim 19 wherein the outer protec polymeric layer. tive sheath is formed by extrusion. 9. The flexible hose of claim 1 having more than one 24. The method ofclaim 19 wherein the semi-conduc layer of fibrous reinforcement and the adjacent layers 30 tive outer layer is exposed to radiation after the fibrous thereof are bonded together. reinforcement has been disposed thereabout 10. The flexible hose of claim 1 wherein the poly 25. The method ofclaim 19 wherein the semi-conduc meric material is an extruded polyurethane. tive outer layer is exposed to radiation after the outer 11. The flexible hose of claim 1 wherein the poly protective sheath has been formed about the fibrous meric material of the sheath is a cross-linked polymeric 33 reinforcement. material. 26. The method of claim 19 wherein the polymeric 12. The flexible hose of claim 1 wherein the cross- material of the inner layer is a nylon. linked polymeric material of the semi-conductive outer 27. The method ofclaim 19 wherein the semi-conduc- layer is a radiation cross-linked material. tive material of the outer layer is a polyurethane. 13. The flexible hose of claim 12 wherein the radia- 0 28. The method of claim 19 wherein the outer layer of tion cross-linked semi-conductive layer is a high energy semi-conductive material has an electrical volume resis electron radiation cross-linked material. tivity at 20* C. of not more than about 2000 ohm-cm. 14. The flexible hose of claim 1 wherein the poly 29. The method of claim 19 wherein the outer layer of meric material of the sheath is an irradiation cross- semi-conductive material contains carbon particles. linked material. 63 30. The method of claim 19 wherein the fibrous rein 15. The flexible hose of claim 14 wherein the radia forcement is bonded to the semi-conductive outer layer tion cross-linked polymeric material of the sheath is a during the process of making the hose. high energy electron radiation cross-linked material.