CA1049424A - Semi-conductive paint hose - Google Patents
Semi-conductive paint hoseInfo
- Publication number
- CA1049424A CA1049424A CA262,745A CA262745A CA1049424A CA 1049424 A CA1049424 A CA 1049424A CA 262745 A CA262745 A CA 262745A CA 1049424 A CA1049424 A CA 1049424A
- Authority
- CA
- Canada
- Prior art keywords
- core tube
- layer
- hose
- polyurethane
- polyester
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L11/00—Hoses, i.e. flexible pipes
- F16L11/04—Hoses, i.e. flexible pipes made of rubber or flexible plastics
- F16L11/08—Hoses, i.e. flexible pipes made of rubber or flexible plastics with reinforcements embedded in the wall
- F16L11/085—Hoses, i.e. flexible pipes made of rubber or flexible plastics with reinforcements embedded in the wall comprising one or more braided layers
- F16L11/086—Hoses, i.e. flexible pipes made of rubber or flexible plastics with reinforcements embedded in the wall comprising one or more braided layers two layers
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04C—BRAIDING OR MANUFACTURE OF LACE, INCLUDING BOBBIN-NET OR CARBONISED LACE; BRAIDING MACHINES; BRAID; LACE
- D04C1/00—Braid or lace, e.g. pillow-lace; Processes for the manufacture thereof
- D04C1/06—Braid or lace serving particular purposes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L11/00—Hoses, i.e. flexible pipes
- F16L11/04—Hoses, i.e. flexible pipes made of rubber or flexible plastics
- F16L11/12—Hoses, i.e. flexible pipes made of rubber or flexible plastics with arrangements for particular purposes, e.g. specially profiled, with protecting layer, heated, electrically conducting
- F16L11/127—Hoses, i.e. flexible pipes made of rubber or flexible plastics with arrangements for particular purposes, e.g. specially profiled, with protecting layer, heated, electrically conducting electrically conducting
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Textile Engineering (AREA)
- Rigid Pipes And Flexible Pipes (AREA)
- Laminated Bodies (AREA)
Abstract
SEMI-CONDUCTIVE PAINT HOSE
Abstract of the Disclosure A composite reinforced hose for conveying paint under pressure is provided with a core tube simultaneously coextruded from two or more thermo-plastic synthetic polymers which are in intimate contact with each other. The inner layer of the core tube is nylon or other chemical. resistant polymer which is substantially non-conductive and the outer layer is electrically conductive. The conductive polymer layer serves as a ground for static electricity.
Abstract of the Disclosure A composite reinforced hose for conveying paint under pressure is provided with a core tube simultaneously coextruded from two or more thermo-plastic synthetic polymers which are in intimate contact with each other. The inner layer of the core tube is nylon or other chemical. resistant polymer which is substantially non-conductive and the outer layer is electrically conductive. The conductive polymer layer serves as a ground for static electricity.
Description
This invention relates generally to composite tubing and more particularly to a hose fox transmitting fluids under pressure in a spraying apparatus such as a paint spray.
Apparatus ~or spraying liquids such as paint is provided with a pump and hose assembly for transmitting liquid under pressure from a supply tank to a spray gun nozzle. An electrically conductive ground wire is usually -included throughout the length of the hose to drain off any static electricity developed at the spray nozzle of the hose to prevent sparking when it approaches a conductor ~
such as a steel beam or the like. A hose having a flexible j~ `
polymeric core tube, fibrous reinforcing material wound about the core tube and a protective sheath is used to ~;~
convey the li~uid at a pressure which is sufficiently high to produce a spray. The hose must be capable of expanding -~
radially under the pulsation of the pump in order to act as an accumulator which attentuates the pulses so as to minimize .
pulsating at the nozzle and thereby produce a relatively smooth ~ `
and uniform spray of li~uid. On electric motor operated paint :
spray systems, the accumulator action also retards the rate of pressure change affecting the motor controlling pressure switch, thereby reducing the number of stops and starts of the motor controlling the fluid pump.
It has been proposed heretofore to wind a ground wire about the core tube as one of the braids of the ' . .
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reinforcing layer. However, the wire fre~uently broke under pressure and the abrasion of the braid by the wire sometimes resulted in bursting of the hose.
It is proposed in U.S. Patents 3,~45,583, 3,~43,803 and 3,780,208 to provide hoses for transmitting liquids from a pulsating source with a grounding wire helically wound about the core tube and enclosed within a rupture resistant sleeve. ~ :
While the disclosed hoses have been found to be adapted for successfully transmitting paints under most conditions, the inclusion of a grounding wire enclosed in a plastic sleeve introduces additional steps in the manufacture of the hose and it has been found in practice that the ground wire sometimes ruptures and the fragments are not confined sufficiently to maintain continuity of the static discharge system. Also, the fragments may penetrate the core or sheath causing a :' premature failure of the hose.
It is therefore an object of this invention to provide an improved composite hose having a means for static discharge. Another object of the invention is to provide a composite hose for use with a paint spray-ing apparatus or the like which is adapted for transmission . of pulsating fluids and has a static discharge means which is conveniently incorporated in the hose and effectively discharges static electricity throughout the life of the hose. A further object of the invention is to provide a `' composite hose with a grounding means coextensive with the length of the hose which is not ruptured or otherwise broken by the pulsating action of the hose.
, 31 0~9~2~ ~
Other objects will become apparent from the following description with reference to the accom-panying drawing wherein Figure 1 is a cut-away side elevation, partially in section, of one embodiment of the invention; and Figure 2 is a cross-section ta]~en along the line 2-2 of Figure 1.
The foregoing objects and others are accom- ;
plished in accordance with this invention, generally speaking, by providing a composite reinforced paint hose having a core tube shaped from two layers of synthetic thermoplastic resin which are in intimate contact with each other with the outer layer of the tube wall being a semi-conductive material, one or more layers of a fibrous reinforcing material disposed about the core tube -and a protective synthetic resinous sheath disposed about the fibrous reinforcing material. The composite core tube has an inner wall adapted to resist chemical attack by the fluid conveyed by the hose while the coextensive outer layer o~ the core tube serves as a means for conducting any static electricity along the length of the hose to a suitable ground wire. The invention thus provides a flexible paint hose having a synthetic resinous core tube, a fibrous reinforcing layer about the core tube, a protective sheath about the fibrous layer and a grounding means forming an integral part of the wall of the core tube.
Although the laminated core tube may be formed by spraying the inner layer with a conductive coating or by dipping the inner layer in a conductive resin, the core tube is preferably formed by coaxially extruding--t~70 di~ferent ~, 3 . .
1~9194Z~ ~
extrudable synthetic polymers to provide a flexible tube having a wall of two synthetic resinous layers. The two layers may be extruded in two separate extrusion steps or they may be simultaneously coextruded so that the layers are melt fused together. The conductive layer extends throughout the entire length of the hose and is in electrical contact with a grounded hose fittinq. The grounding layer is a synthetic polymer which is semi-con-ductive, i.e., i-t exhibits a volume resistivity of 10 ohm-cm or less.
In airless paint spraying processes, it is un-desirable to accumulate more than 1400 static volts at the spray gun of the spraying apparatus because of the danger of igniting the air-solvent mixture about the spray gun.
Preferably, a safety factor of ~:1 should be maintained which means that the static voltage on the spray end of the hose should not exceed 350 volts. The hose provided by this invention has a ground which is a semi-conductive .. .... .
layer of polymer which will drain off the static potential so a frightening or dangerous electrical-arc between the spray gun and ground is avoided.
Any suitable conductive synthetic polymer may be used. Preferably/ the conductive synthetic polymer is one which will melt fuse to the polymer of the first layer when the two polymers are coa~ially extruded. The conductive polymer must have the required electrical properties. While a semi-conductive polymer having a volume resistivity after application and other processing of as high as 100,000 ohm-cm at ambient temperature may be used, usually the volume resistivity will no-t be more . . :
than about 2000 ohm-cm. It is preferred to use one ~
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having a calculated volume resistivity of not more than about 500 ohm-cm. In fact, best results have been obtained so far with a polymer having a volume resistivity of 40 or less ohm-cm. The volume resis-tivity may be calculated by the method described in "NFPA Journal No. 77, Static Electricity, 1972."
Examples of suitable polymers are ethylene-ethyl acrylate, ethylene-vinyl acrylate and thermoplastic rubber having the desired volume resistivity but it is preferred to use a polyurethane of the desired volume resistivity in hoses having a nylon inner layer where kink resistance is desirable because the polyurethane bonds well to the nylon and can be bonded to the reinforcing material.
The semi-conductive polymer may have carbon particles including graphite particles, silver particles, copper particles or other suitable electrically conductive particles dispersed substantially uniformly therein to provide the polymer with a volume resistivity within the requirements of the hose.
The invention permits the manufacture of a com-posite reinforced semi-conductive paint hose having some particularly desirable physical property without substantial compromise of other desirable properties combined with ~ a means for effectively draining static electricity ; from the hose. For example, 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 elastomeric polyurethane having electrically conductive particles dispersed therein ~: :
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may be fused thereto as the outer surface to provide improved flexibility, kink resistance and means for preventing sparking of static electricity at the nozzle of the hose. The outer layer containing electrically conductive particles may be shaped from a resin such as a polyurethane which can be solvated with a polar solvent to adhesively bond the core tube to the adjacent layer of reinforcing material and to improve the strength of the hose. In such a hose, the ; 10 relative thickness of the nylon and conductive polyure-thane layers may be varied to further modify the properties of the hose.
The core tube may be fabricated by any suitable simultaneous coaxial extrusion procesæ which will produce melt fusion of two different layers of synthetic thermo-plastic resins together to the extent that the two layers will not separate at the interface under elonga-tion 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 thermo~plastic 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 portion of the core tube wall is applied thereover and the two molten synthetic resins are extruded through the same extrusion die.
i It has been found that two layers of selected thermoplastic synthetic resin with one being electrically conductive will melt fuse together along the interface :::
.
':' , ' .
;.. , , . .. . . . ~ ., ., .. ., : .. .. . - - . . .
99~2 L~
and become so firmly bonded together that the core tube will not delaminate in a hose used to convey fluids under high pressure even if the physical prop-erties of the two layers are significantly different.
For example, nylon and a semi-conductive thermoplastic polyurethane having particles of carbon black uniformly dispersed therein will melt fuse together in accordance with the process of the invention. Hence, the invention contemplates a semi-conductive paint hose having a core ]0 tube with a layer of nylon melt fused to a layer of thermoplastic substantially non-porous polyurethane.
Usually, the nylon layer will be the innermost layer because of its chemical resistance. The semi-conductive polyurethane layer imparts flexibility to the hose and may also be used ~or making an adhesive to bond the core tube to the fibrous reinforcing layer so it is usually disposed on the outside of the core tube.
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 polyurethane having a hardness of Shore A 80 to 95 may be coextruded to form a core tube.
~, The harder thermoplastic polyurethane has better chemical , resistance than the softer one so the harder one is usually the inner layer of the core tube while the softer one contains particles of an electrical conductor and :
is the outer layer. The presence of the layer of softer .
:, .
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polyurethane improves the flexibility of the hose as well as providing a semi-conductor for static electricity.
Other combinations of synthe-tic resins whic~
may be co-axially extruded simultaneously or in tandem -to form a core tube having two or more layers are those dis-closed in our Canadian Pat. Appl. No. 248,9~0~ filed M~rch 29/76. For example,segmented co-polyesters such as "Hytrel" as one layer and a polyvinyl chloride compound for the conductive layer.
A segmented co-polyester may be used for one layer and a conductive substantially non-porous thermoplastic poly-urethane as the other layer. A mechanical mixture of an aromatic polyester such as poly(tetramethylene terephthalate) and a segmented co-polyester may be used as one layer and a conductive polyvinyl chloride polymer as the outer layer.
The laminated core tubes combining a layer of "~ytrel" or a mixture of a segmented co-polyester and an aromatic polyester and a layer of polyvinyl chloride compound or polyurethane will usually have the layer containing the segmented co-polyester on the inside as the non-conductive layer. A mechanical mixture of segmented co-polyester and polyurethane may also be used for one of the layers, usually the outer layer~ The inner layer of tlle core tube may be a mixture containing from about 5 to about 95% by weight polyurethane and 95 to S% 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.
In these embodiments, the outer layer contains particles which are electrically conductive.
~: ' 1~494~
Examples of suitable thermoplastic aromatic polyesters are "Valox", aromatic polyester sold bv the General Electric Co., "Tenite", aromatic polyester sold by Eastman Kodak Co. and "Celanex", aromatic polyester sold by Celenese Plastics Co.
Any suitable relative proportions of aromatic polyester such as "Valox" and seomented co-polyester such as "Hytrel" may be used in the mixtures thereof extruded to form a layer of the core tube. For example, from about 5~ to about 60% by weight aromatic polyester such as "Valox" and 95~ to about 40~ by weight segmented co-polyester such as "Hytrel" may be used. Any suitable mix-ture of polyurethane and co-segmented polyester may be used, but it is preferred to use from abou~ 99~ to about 50% thermo-plastic polyurethane and 1% to about 50% by weight co-seg-mented polyester.
Best results have been obtained so far with a hose having a core tube with an inner nylon surface and a semi-conductive polyurethane surface so such a core tube is preferred. However, other polymers which are resistant to chemical action by the paint may be used for the inner layer such as a segmented co-polyester such as "Hytrel" sold by E.I. duPont de Nemours of Wilmington, Delaware.
The core tube may be adhesively honded to the surface of the reinforcing material by the application of an adhesive material or by activating the surface of -the ~ core tube wi-th a solvating or softening agent to form an - adhesive in situ from the resin on the other surface of the core tube. For example, a polyurethane surface of a core tube may be activated by wetting it with a suitable ';
9 _ :' ~LID49~2~L
polar solvent such as, for example, N-methyl pyrrolidone or the like. However, it is preferred to apply an adhesive material such as a solution of polyurethane between the surface of the core tube and aLdjacent layer of fibrous reinforcing material because the use of a solvating agent to solvate the surface disturbs the uniformity of the distribution of electrically conductive particles and affects the electrical conductivity of the semi-conductive polymer layer. The reinforcin~ fibrous material is then applied under tension about the adhesively wet core tube whereby the strands of reinforcing material become embedded and partially encapsulated by the adhesive.
In this way, the fibrous reinforcing layer becomes bonded -to the core tube and the strength of the hose is improved.
It has been found that simultaneously coextruded properly selected synthetic thermoplastic polymers will become bonded together by melt fusion even though one of the polymers contains particles of electrically conductive material and that an intermediate adhesive is not necessary.
For example, nylon will fuse to a thermoplastic elastomeric polyurethane containing carbon black particles if the two molten synthetic polymers are fed separately to an extrusion head and coextruded one over the other while still molten.
I 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 but it is preferred to melt fuse the semi-conductive layer directly i to the inner layer of the core tube.
., ;~. .
Referring now to the drawing, a semi-conductive ~ paint hose 10 having a core tube I.D. of 0.25 inch is :. .
, - 1 0 - ~ ' ~ 9fl~2~ :
illustrated in Figures 1 and 2. Composite hose 10 has a core tube 17 formed by the simultaneous coaxial extrusion of a layer of nylon 11 about 0.025 inch thick and a semi-conductive thermoplastic elastomeric polyurethane outer layer 12 about 0.015 inch thick and containing carbon particles and having a volume resistivity at room temperature (about 20C.~ of about 100 ohm-cm. The two synthetic resins become fused together at the interface to form a core tube 17 which will not delaminate when the hose 10 is used for conveying a paint under pulsating pressure. The outer surface of polyurethane of core tube 17 is wet with an adhesive solution 13 of a polyurethane in N-methyl pyrrolidone.
A reinorcing layer 14 of nylon filaments is braided under tension around the core tube while the adhesive `
on the surface of core tube 17 is wet. The filaments become bonded to the surface of the core tube 17 forming an elastomeric bond of the fibrous reinforcing material with the core tube. A second reinforcing layer 15 of poly(ethylene -terephthalate)ester is braided over layer 1~. A protective p~lyurethane sheath 16 about 0.025 inch thick is e~truded over fibrous reinforcing layer 15 by extrusion of a thermoplastic elastomeric polyurethane thereover. Sheath 16 may be adhesively bonded to the surface of layer 15.
Any other core tube similar to those disclosed as suitable herein may be substituted in the foregoing embodiment of the invention for core tube 17 and the core tube I7 may or may not be bonded to the reinorcing layer ,, ~
l 30 depending upon the particular requirements of the hose.
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The polyurethane layer 12 of core tube 17 may be extruded from any suitable thermoplastic polyurethane such as the one sold under the trademark "Pellethane"
by the Upjohn Company. The polyurethane 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(tetramethylene ether)glycol, suitable chain extender such as 1,4 butane diol, and 4,4'-diphe--nylmethane diisocyanate and polyurethanes prepared by reacting an inner ester such as poly~e-caprolactone~ester ; and a suitable chain extender such as 1,4 butane diol with an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate are preferred. The sheath 16 may also be extruded from any other suitable synthetic resin such as, for example, nylon in some embodiments of the invention.
The fibrous reinforcing material may be formed by braiding filaments or by helically winding strands of filaments of any sultable synthetic resinous material, such as, for example, a poly(alkylene terephthalate)ester, nylon, aromatic polyamide or the like or combinations thereof. Suitable nylon fibrous reinforcing material is disclosed in U.S. Patent 3,334,164 while suitable poly-(alkylene terephthalate)ester fibrous reinforcing material is disclosed in U.S. Patent 3,062,241. Such fibers h~ve a tenacity of about 7 to about 11 grams per denier and an elongation at break of about 9% to ,:
~ , . .
l~g~
about 17%. In one embodiment of the invention, the hose may be provided with a relnforcing layer of braided or helically wound filaments having a tenacity of at least 13 grams per denier and up to about 25 grams per denier and an elongation at break of ~rom about 2% to about 7% such as the aromatic polyamide fiber marketed by E.I. duPont de Nemours & Co. under the trademark "Kevlar". Suitable reinforcing material containing synthetic aromatic polyamide filaments is disclosed in U.S. Patent No. 3,905,398 issued September 16, 1975. A
fibrous reinforcing material of aromatic polyamide fibers may be used to advantage in composite hoses having a high burst strength.
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 extrusion head.
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 departing from the spirit and scope I of the invention except as it may be limited by the claims.
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Apparatus ~or spraying liquids such as paint is provided with a pump and hose assembly for transmitting liquid under pressure from a supply tank to a spray gun nozzle. An electrically conductive ground wire is usually -included throughout the length of the hose to drain off any static electricity developed at the spray nozzle of the hose to prevent sparking when it approaches a conductor ~
such as a steel beam or the like. A hose having a flexible j~ `
polymeric core tube, fibrous reinforcing material wound about the core tube and a protective sheath is used to ~;~
convey the li~uid at a pressure which is sufficiently high to produce a spray. The hose must be capable of expanding -~
radially under the pulsation of the pump in order to act as an accumulator which attentuates the pulses so as to minimize .
pulsating at the nozzle and thereby produce a relatively smooth ~ `
and uniform spray of li~uid. On electric motor operated paint :
spray systems, the accumulator action also retards the rate of pressure change affecting the motor controlling pressure switch, thereby reducing the number of stops and starts of the motor controlling the fluid pump.
It has been proposed heretofore to wind a ground wire about the core tube as one of the braids of the ' . .
.~`
: ~ ' 9429~
reinforcing layer. However, the wire fre~uently broke under pressure and the abrasion of the braid by the wire sometimes resulted in bursting of the hose.
It is proposed in U.S. Patents 3,~45,583, 3,~43,803 and 3,780,208 to provide hoses for transmitting liquids from a pulsating source with a grounding wire helically wound about the core tube and enclosed within a rupture resistant sleeve. ~ :
While the disclosed hoses have been found to be adapted for successfully transmitting paints under most conditions, the inclusion of a grounding wire enclosed in a plastic sleeve introduces additional steps in the manufacture of the hose and it has been found in practice that the ground wire sometimes ruptures and the fragments are not confined sufficiently to maintain continuity of the static discharge system. Also, the fragments may penetrate the core or sheath causing a :' premature failure of the hose.
It is therefore an object of this invention to provide an improved composite hose having a means for static discharge. Another object of the invention is to provide a composite hose for use with a paint spray-ing apparatus or the like which is adapted for transmission . of pulsating fluids and has a static discharge means which is conveniently incorporated in the hose and effectively discharges static electricity throughout the life of the hose. A further object of the invention is to provide a `' composite hose with a grounding means coextensive with the length of the hose which is not ruptured or otherwise broken by the pulsating action of the hose.
, 31 0~9~2~ ~
Other objects will become apparent from the following description with reference to the accom-panying drawing wherein Figure 1 is a cut-away side elevation, partially in section, of one embodiment of the invention; and Figure 2 is a cross-section ta]~en along the line 2-2 of Figure 1.
The foregoing objects and others are accom- ;
plished in accordance with this invention, generally speaking, by providing a composite reinforced paint hose having a core tube shaped from two layers of synthetic thermoplastic resin which are in intimate contact with each other with the outer layer of the tube wall being a semi-conductive material, one or more layers of a fibrous reinforcing material disposed about the core tube -and a protective synthetic resinous sheath disposed about the fibrous reinforcing material. The composite core tube has an inner wall adapted to resist chemical attack by the fluid conveyed by the hose while the coextensive outer layer o~ the core tube serves as a means for conducting any static electricity along the length of the hose to a suitable ground wire. The invention thus provides a flexible paint hose having a synthetic resinous core tube, a fibrous reinforcing layer about the core tube, a protective sheath about the fibrous layer and a grounding means forming an integral part of the wall of the core tube.
Although the laminated core tube may be formed by spraying the inner layer with a conductive coating or by dipping the inner layer in a conductive resin, the core tube is preferably formed by coaxially extruding--t~70 di~ferent ~, 3 . .
1~9194Z~ ~
extrudable synthetic polymers to provide a flexible tube having a wall of two synthetic resinous layers. The two layers may be extruded in two separate extrusion steps or they may be simultaneously coextruded so that the layers are melt fused together. The conductive layer extends throughout the entire length of the hose and is in electrical contact with a grounded hose fittinq. The grounding layer is a synthetic polymer which is semi-con-ductive, i.e., i-t exhibits a volume resistivity of 10 ohm-cm or less.
In airless paint spraying processes, it is un-desirable to accumulate more than 1400 static volts at the spray gun of the spraying apparatus because of the danger of igniting the air-solvent mixture about the spray gun.
Preferably, a safety factor of ~:1 should be maintained which means that the static voltage on the spray end of the hose should not exceed 350 volts. The hose provided by this invention has a ground which is a semi-conductive .. .... .
layer of polymer which will drain off the static potential so a frightening or dangerous electrical-arc between the spray gun and ground is avoided.
Any suitable conductive synthetic polymer may be used. Preferably/ the conductive synthetic polymer is one which will melt fuse to the polymer of the first layer when the two polymers are coa~ially extruded. The conductive polymer must have the required electrical properties. While a semi-conductive polymer having a volume resistivity after application and other processing of as high as 100,000 ohm-cm at ambient temperature may be used, usually the volume resistivity will no-t be more . . :
than about 2000 ohm-cm. It is preferred to use one ~
_~_ ' ' 9~Z~
having a calculated volume resistivity of not more than about 500 ohm-cm. In fact, best results have been obtained so far with a polymer having a volume resistivity of 40 or less ohm-cm. The volume resis-tivity may be calculated by the method described in "NFPA Journal No. 77, Static Electricity, 1972."
Examples of suitable polymers are ethylene-ethyl acrylate, ethylene-vinyl acrylate and thermoplastic rubber having the desired volume resistivity but it is preferred to use a polyurethane of the desired volume resistivity in hoses having a nylon inner layer where kink resistance is desirable because the polyurethane bonds well to the nylon and can be bonded to the reinforcing material.
The semi-conductive polymer may have carbon particles including graphite particles, silver particles, copper particles or other suitable electrically conductive particles dispersed substantially uniformly therein to provide the polymer with a volume resistivity within the requirements of the hose.
The invention permits the manufacture of a com-posite reinforced semi-conductive paint hose having some particularly desirable physical property without substantial compromise of other desirable properties combined with ~ a means for effectively draining static electricity ; from the hose. For example, 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 elastomeric polyurethane having electrically conductive particles dispersed therein ~: :
~ .
~9a~2~L
may be fused thereto as the outer surface to provide improved flexibility, kink resistance and means for preventing sparking of static electricity at the nozzle of the hose. The outer layer containing electrically conductive particles may be shaped from a resin such as a polyurethane which can be solvated with a polar solvent to adhesively bond the core tube to the adjacent layer of reinforcing material and to improve the strength of the hose. In such a hose, the ; 10 relative thickness of the nylon and conductive polyure-thane layers may be varied to further modify the properties of the hose.
The core tube may be fabricated by any suitable simultaneous coaxial extrusion procesæ which will produce melt fusion of two different layers of synthetic thermo-plastic resins together to the extent that the two layers will not separate at the interface under elonga-tion 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 thermo~plastic 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 portion of the core tube wall is applied thereover and the two molten synthetic resins are extruded through the same extrusion die.
i It has been found that two layers of selected thermoplastic synthetic resin with one being electrically conductive will melt fuse together along the interface :::
.
':' , ' .
;.. , , . .. . . . ~ ., ., .. ., : .. .. . - - . . .
99~2 L~
and become so firmly bonded together that the core tube will not delaminate in a hose used to convey fluids under high pressure even if the physical prop-erties of the two layers are significantly different.
For example, nylon and a semi-conductive thermoplastic polyurethane having particles of carbon black uniformly dispersed therein will melt fuse together in accordance with the process of the invention. Hence, the invention contemplates a semi-conductive paint hose having a core ]0 tube with a layer of nylon melt fused to a layer of thermoplastic substantially non-porous polyurethane.
Usually, the nylon layer will be the innermost layer because of its chemical resistance. The semi-conductive polyurethane layer imparts flexibility to the hose and may also be used ~or making an adhesive to bond the core tube to the fibrous reinforcing layer so it is usually disposed on the outside of the core tube.
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 polyurethane having a hardness of Shore A 80 to 95 may be coextruded to form a core tube.
~, The harder thermoplastic polyurethane has better chemical , resistance than the softer one so the harder one is usually the inner layer of the core tube while the softer one contains particles of an electrical conductor and :
is the outer layer. The presence of the layer of softer .
:, .
~IL04~4;~9~
polyurethane improves the flexibility of the hose as well as providing a semi-conductor for static electricity.
Other combinations of synthe-tic resins whic~
may be co-axially extruded simultaneously or in tandem -to form a core tube having two or more layers are those dis-closed in our Canadian Pat. Appl. No. 248,9~0~ filed M~rch 29/76. For example,segmented co-polyesters such as "Hytrel" as one layer and a polyvinyl chloride compound for the conductive layer.
A segmented co-polyester may be used for one layer and a conductive substantially non-porous thermoplastic poly-urethane as the other layer. A mechanical mixture of an aromatic polyester such as poly(tetramethylene terephthalate) and a segmented co-polyester may be used as one layer and a conductive polyvinyl chloride polymer as the outer layer.
The laminated core tubes combining a layer of "~ytrel" or a mixture of a segmented co-polyester and an aromatic polyester and a layer of polyvinyl chloride compound or polyurethane will usually have the layer containing the segmented co-polyester on the inside as the non-conductive layer. A mechanical mixture of segmented co-polyester and polyurethane may also be used for one of the layers, usually the outer layer~ The inner layer of tlle core tube may be a mixture containing from about 5 to about 95% by weight polyurethane and 95 to S% 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.
In these embodiments, the outer layer contains particles which are electrically conductive.
~: ' 1~494~
Examples of suitable thermoplastic aromatic polyesters are "Valox", aromatic polyester sold bv the General Electric Co., "Tenite", aromatic polyester sold by Eastman Kodak Co. and "Celanex", aromatic polyester sold by Celenese Plastics Co.
Any suitable relative proportions of aromatic polyester such as "Valox" and seomented co-polyester such as "Hytrel" may be used in the mixtures thereof extruded to form a layer of the core tube. For example, from about 5~ to about 60% by weight aromatic polyester such as "Valox" and 95~ to about 40~ by weight segmented co-polyester such as "Hytrel" may be used. Any suitable mix-ture of polyurethane and co-segmented polyester may be used, but it is preferred to use from abou~ 99~ to about 50% thermo-plastic polyurethane and 1% to about 50% by weight co-seg-mented polyester.
Best results have been obtained so far with a hose having a core tube with an inner nylon surface and a semi-conductive polyurethane surface so such a core tube is preferred. However, other polymers which are resistant to chemical action by the paint may be used for the inner layer such as a segmented co-polyester such as "Hytrel" sold by E.I. duPont de Nemours of Wilmington, Delaware.
The core tube may be adhesively honded to the surface of the reinforcing material by the application of an adhesive material or by activating the surface of -the ~ core tube wi-th a solvating or softening agent to form an - adhesive in situ from the resin on the other surface of the core tube. For example, a polyurethane surface of a core tube may be activated by wetting it with a suitable ';
9 _ :' ~LID49~2~L
polar solvent such as, for example, N-methyl pyrrolidone or the like. However, it is preferred to apply an adhesive material such as a solution of polyurethane between the surface of the core tube and aLdjacent layer of fibrous reinforcing material because the use of a solvating agent to solvate the surface disturbs the uniformity of the distribution of electrically conductive particles and affects the electrical conductivity of the semi-conductive polymer layer. The reinforcin~ fibrous material is then applied under tension about the adhesively wet core tube whereby the strands of reinforcing material become embedded and partially encapsulated by the adhesive.
In this way, the fibrous reinforcing layer becomes bonded -to the core tube and the strength of the hose is improved.
It has been found that simultaneously coextruded properly selected synthetic thermoplastic polymers will become bonded together by melt fusion even though one of the polymers contains particles of electrically conductive material and that an intermediate adhesive is not necessary.
For example, nylon will fuse to a thermoplastic elastomeric polyurethane containing carbon black particles if the two molten synthetic polymers are fed separately to an extrusion head and coextruded one over the other while still molten.
I 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 but it is preferred to melt fuse the semi-conductive layer directly i to the inner layer of the core tube.
., ;~. .
Referring now to the drawing, a semi-conductive ~ paint hose 10 having a core tube I.D. of 0.25 inch is :. .
, - 1 0 - ~ ' ~ 9fl~2~ :
illustrated in Figures 1 and 2. Composite hose 10 has a core tube 17 formed by the simultaneous coaxial extrusion of a layer of nylon 11 about 0.025 inch thick and a semi-conductive thermoplastic elastomeric polyurethane outer layer 12 about 0.015 inch thick and containing carbon particles and having a volume resistivity at room temperature (about 20C.~ of about 100 ohm-cm. The two synthetic resins become fused together at the interface to form a core tube 17 which will not delaminate when the hose 10 is used for conveying a paint under pulsating pressure. The outer surface of polyurethane of core tube 17 is wet with an adhesive solution 13 of a polyurethane in N-methyl pyrrolidone.
A reinorcing layer 14 of nylon filaments is braided under tension around the core tube while the adhesive `
on the surface of core tube 17 is wet. The filaments become bonded to the surface of the core tube 17 forming an elastomeric bond of the fibrous reinforcing material with the core tube. A second reinforcing layer 15 of poly(ethylene -terephthalate)ester is braided over layer 1~. A protective p~lyurethane sheath 16 about 0.025 inch thick is e~truded over fibrous reinforcing layer 15 by extrusion of a thermoplastic elastomeric polyurethane thereover. Sheath 16 may be adhesively bonded to the surface of layer 15.
Any other core tube similar to those disclosed as suitable herein may be substituted in the foregoing embodiment of the invention for core tube 17 and the core tube I7 may or may not be bonded to the reinorcing layer ,, ~
l 30 depending upon the particular requirements of the hose.
'' ' ~ `i ' '' - lD ~
, ,:
~9~z~
The polyurethane layer 12 of core tube 17 may be extruded from any suitable thermoplastic polyurethane such as the one sold under the trademark "Pellethane"
by the Upjohn Company. The polyurethane 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(tetramethylene ether)glycol, suitable chain extender such as 1,4 butane diol, and 4,4'-diphe--nylmethane diisocyanate and polyurethanes prepared by reacting an inner ester such as poly~e-caprolactone~ester ; and a suitable chain extender such as 1,4 butane diol with an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate are preferred. The sheath 16 may also be extruded from any other suitable synthetic resin such as, for example, nylon in some embodiments of the invention.
The fibrous reinforcing material may be formed by braiding filaments or by helically winding strands of filaments of any sultable synthetic resinous material, such as, for example, a poly(alkylene terephthalate)ester, nylon, aromatic polyamide or the like or combinations thereof. Suitable nylon fibrous reinforcing material is disclosed in U.S. Patent 3,334,164 while suitable poly-(alkylene terephthalate)ester fibrous reinforcing material is disclosed in U.S. Patent 3,062,241. Such fibers h~ve a tenacity of about 7 to about 11 grams per denier and an elongation at break of about 9% to ,:
~ , . .
l~g~
about 17%. In one embodiment of the invention, the hose may be provided with a relnforcing layer of braided or helically wound filaments having a tenacity of at least 13 grams per denier and up to about 25 grams per denier and an elongation at break of ~rom about 2% to about 7% such as the aromatic polyamide fiber marketed by E.I. duPont de Nemours & Co. under the trademark "Kevlar". Suitable reinforcing material containing synthetic aromatic polyamide filaments is disclosed in U.S. Patent No. 3,905,398 issued September 16, 1975. A
fibrous reinforcing material of aromatic polyamide fibers may be used to advantage in composite hoses having a high burst strength.
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 extrusion head.
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 departing from the spirit and scope I of the invention except as it may be limited by the claims.
;`; ~ -'' '' :
. . I .
t, : .
'~ ;' "'' '"''' :
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A flexible composite reinforced hose for conveying fluids under pressure comprising a flexible core tube, a fibrous reinforcing material about the core tube and a protective sheath over the fibrous material, said core tube having an inner substantially non-conductive thermoplastically extruded polymer layer and an electrically conductive synthetic polymer layer disposed radially out-wardly from the inner layer and in intimate contact there-with as its sole means of conducting electrical current.
2. The composite hose of Claim 1 wherein the layers are melt fused together.
3. The composite hose of Claim 2 wherein the inner layer of the core tube is nylon and the layer fused thereto is a polyurethane.
4. The composite reinforced hose of Claim 2 wherein the electrically conductive layer contains carbon particles.
5. The composite reinforced hose of Claim 3 wherein the electrically conductive layer is a polyurethane having a volume resistivity of not more than about 2000 ohm-cm.
6. The composite reinforced hose of Claim 2 wherein the electrically conductive layer of the core tube has particles of electroconductive material distributed therein and a volume resistivity of not more than about 2000 ohm-cm.
7. The composite reinforced hose of Claim 2 wherein the core tube has only two layers and the inner layer is nylon and the outer layer is polyurethane having carbon particles distributed therein and the outer layer is bonded to the fibrous reinforcing material.
8. The composite reinforced hose of Claim 2 wherein the fibrous reinforcing material is nylon, poly (alkylene terephthalate)ester or an aromatic polyamide.
9. The composite hose of Claim 2 wherein the sheath is a thermoplastic polyurethane.
10. The composite hose of Claim 2 wherein the sheath is bonded to the fibrous reinforcing material.
11. The composite reinforced hose of Claim 1 wherein said core tube is (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 polyester and an outer layer of polyvinyl chloride compound, segmented co-polyester, poly-urethane or a mixture of segmented co-polyester and poly-urethane, 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, poly-urethane or a mixture of segmented co-polyester and poly-urethane and said outer layer contains electrically conductive particles.
12. The hose of Claim 11 wherein the inner and outer layers are melt fused together.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62018975A | 1975-10-06 | 1975-10-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1049424A true CA1049424A (en) | 1979-02-27 |
Family
ID=24484951
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA262,745A Expired CA1049424A (en) | 1975-10-06 | 1976-10-05 | Semi-conductive paint hose |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5246516A (en) |
| BE (1) | BE846234A (en) |
| CA (1) | CA1049424A (en) |
| DE (1) | DE2642442C2 (en) |
| FR (1) | FR2327479A1 (en) |
| GB (1) | GB1562435A (en) |
| ZA (1) | ZA765953B (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5444409U (en) * | 1977-09-02 | 1979-03-27 | ||
| ZA803980B (en) * | 1979-07-17 | 1981-08-26 | Dunlop Ltd | Reinforced tubular articles |
| JPS6338943Y2 (en) * | 1980-07-04 | 1988-10-13 | ||
| JPS5790992U (en) * | 1980-11-26 | 1982-06-04 | ||
| JPS6034591A (en) * | 1983-08-04 | 1985-02-22 | 矢崎総業株式会社 | Flexible pipe |
| FR2556094B1 (en) * | 1983-12-05 | 1986-06-20 | Commissariat Energie Atomique | NON-POLLUTANT LIQUID SAMPLING PUMP IN METAL ELEMENTS |
| DE4025301C2 (en) * | 1990-08-09 | 1998-04-30 | Inventa Ag | Antistatic fuel line |
| DE9208780U1 (en) * | 1992-07-01 | 1992-09-10 | REHAU AG + Co, 8673 Rehau | High-pressure hose made of polymeric active ingredients |
| EP0975909A1 (en) * | 1997-04-15 | 2000-02-02 | Nordson Corporation | Apparatus for use in applying electrostatically charged coating material |
| DE19724038C1 (en) * | 1997-06-06 | 1999-01-14 | Contitech Schlauch Gmbh | Electrically conductive hose |
| JP2002168379A (en) * | 2000-11-29 | 2002-06-14 | Bridgestone Flowtech Corp | Gas hose for medical purpose |
| US7123826B2 (en) * | 2003-07-16 | 2006-10-17 | Wellstream International Ltd. | Temperature controlled pipe and method of manufacturing same |
| US7694695B2 (en) * | 2008-02-26 | 2010-04-13 | The Gates Corporation | Controlled expansion hose |
| JP2009236258A (en) * | 2008-03-28 | 2009-10-15 | Bridgestone Corp | Anti-static hose |
| DE202010004707U1 (en) * | 2010-04-08 | 2011-09-02 | Rehau Ag + Co. | Hose, in particular electrode suction hose, and electrode suction |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE947127C (en) * | 1952-04-19 | 1956-08-09 | Muendener Gummiwarenfabrik Geb | Especially for petrol stations, electrically conductive hose |
| DE1722682U (en) * | 1953-10-30 | 1956-05-17 | Dynamit Actien Ges Vorm Alfred | PLASTIC PIPE MADE FROM HARDENED PLASTICS. |
-
1976
- 1976-09-15 BE BE170660A patent/BE846234A/en unknown
- 1976-09-21 DE DE2642442A patent/DE2642442C2/en not_active Expired
- 1976-10-05 GB GB41321/76A patent/GB1562435A/en not_active Expired
- 1976-10-05 CA CA262,745A patent/CA1049424A/en not_active Expired
- 1976-10-05 ZA ZA765953A patent/ZA765953B/en unknown
- 1976-10-05 FR FR7629917A patent/FR2327479A1/en active Granted
- 1976-10-05 JP JP51119803A patent/JPS5246516A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1562435A (en) | 1980-03-12 |
| BE846234A (en) | 1976-12-31 |
| JPS5246516A (en) | 1977-04-13 |
| DE2642442C2 (en) | 1983-05-26 |
| DE2642442A1 (en) | 1977-04-21 |
| ZA765953B (en) | 1977-09-28 |
| FR2327479B1 (en) | 1983-07-29 |
| FR2327479A1 (en) | 1977-05-06 |
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