CA1038780A

CA1038780A - Reinforced thermoplastic hose

Info

Publication number: CA1038780A
Application number: CA267,412A
Authority: CA
Inventors: Stephen R. Paquette; Clayton C. Wagner (Jr.)
Original assignee: Polymer Corp
Current assignee: Polymer Corp
Priority date: 1975-12-10
Filing date: 1976-12-08
Publication date: 1978-09-19
Also published as: DE2654719A1; IT1064507B; SE7613809L; GB1572717A; JPS5271724A; FR2334904A1

Abstract

ABSTRACT OF THE DISCLOSURE
A durable three-component hose comprises a nylon tube, a reinforcement of one or more plies of synthetic yarns or monofilaments wound or braided or spirally wrapped over the tube, and a melt-extruded polyolefin cover.
Extraordinary burst strength is achieved by using a mixed reinforcement, in which some of the plies or wrappings are capable of being bonded with the nylon tube, and in which other plies or wrappings are capable of bonding with the polyolefin cover. In a typical construction the reinforcement is bonded by solvating the nylon tube surface with resorcinol so that nylon yarns of the applied reinforcement will bond therewith and the olefin cover - e.g. polypropylene to which a minor portion of EDPM or SBR rubbers has been admixed - is bonded to that portion of the reinforcement which is polyolefin, for example polypropylene yarns or monofilaments.

Description

This invention relates to high-pressure reinforced flexible hose made from synthetic polymeric materials. More par-ticularly, the invention relates -to a high-pressure hose that is particularly adapted, among a number of end uses, for service in portable air conditioning devices in automobiles.

Discussion of Hose Design Problems, and Prlor art Forms ~, .
For greater clarity in the following review of the state of the art, a number of common terms will be used, with ;~

intended meanings as set out in the definitions given below~
"Tube" as used herein designates an inner tubular component of a hose that serves as a conduit for the transmission of fluids and which is made of a synthetic polymeric material.
"Reinforcement" as used herein designates one or more ~ . . . ~ .
plies of synthetic yarns or monofilaments that are applied in , : -tensioned relationship as by spiral wrapping, braiding or knitting, ~ ~ -over the tube to increase the burst strength of the tube. -~
"Cover" as used herein designates a protective layer of polymeric material that envelopes the reinforcement.
"Hose" as used herein designates a composite structure including a tube, a reinforcement, and a cover, intended for the transmission of fluids under pressure. ;~
"Bonding" as used herein refers to methods for adhering the several components of a hose to each other as may be effected through the use of heat, solvents or adhesives.
Flexible hoses adapted to contain or transmit high-pressure fluid have found utility in a wide variety of applications. By way of example, there may be mentioned such diverse applications as brake hose, both pneumatic and hydraulic, hose for pai~ spray glms,hose for flexible air conditioning lines as used in vehicles, hose or ~lexible hydraul:ic lines for use in articulated machinery, both movable and stationary, and many others.

Until the 1930's practically all high pressure hoses ~L

utilized natural or synthetic rubbers to form the tube and the cover, and high tenslle strength fibers and wires to form the reinforcement. Since -that -time, a number of new and different types of flexible high-pressure hoses have been manufactured from thermoplastic polymeric materials. Since thermoplastic polymers as a class have a wider range of properties than do the conventional rubbers, the materials for making the hose can be selected with greater regard to the operational requirements and the environment in which the hose is intended to be used. Among other criteria that can be taken into account are resistance to chemicals, hydrocarbons, solvents, acids and al~alis; gas and vapor permeability; high and low temperature characteristics, weatherability; flammability; abrasion resistance; flexibility;
and physical properties such as fatigue resistance, elongation, cold flow, creep, and so forth.
The reinforcement of the hose provides dimensional ;-~-stability, increases burst strength, and prevents kinking.
Since the reinforcement is protected from environmental chemical ;
attack by being sandwiched between the tube and the cover, the ;~
braid material may be selected primarily for its tensile strength.
Other properties such as elongation, fatigue resistance, moisture stability, and high and low temperature characteristics, are also of importance, depending on the application. When a bonded hose construction is desired, consideration should be given to the bondability of the rein~orcement yarns to the tube and the cover.
Nylon and polyester fibers are among those most commonly used for the reinforcement.
Since the fiber reinforcement material is utilized to increase the strength of the hose, it is undesirable for the high 'censile strength yarn to be weakened during any bonding operation. For this reason thermal bonding may prove unacceptable and solvents should be used sparingly. Adhesives ma~ be used to `~

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obtain a bonded construction, but generally the~ result in inferior bonds which permit the cover to be peeled away from the braid or the braid to be peele~ away from the inner core.

With the foregoing considerations in mind, materials for constructing a hose particularly adapted for use in automotive air conditioners can be selected. This hose application i8 ; :
particularly severe because so many requirements are imposed. ~T
the outset, if the hose is to be of any value, it must be capable of containing a refrigerant without substantial diffusion through the hose. Further, a low moisture penetration rate is desired so that water will not build up in the system. Since air condi- -tioners for automobiles are mounted under the hood in the engine compartment, the hose must be resistant to attack by gasoline, oil, and battery acid. Lastly, the hose must retain its flexibility over a wide temperature range of from about -40C as is likely to i be experienced in very cold climates, to temperatures of about 120-150C, which may be reached in the engine compartment.

SUMMARY STATEMENT OF THE INVENTION
The present invention has among its objectives the provision o a high-pressure hose that is particularly suitable or use with automotive air conditioners. The high-pressure hose which has been innovated for this service is effective to retain a refrigerant, is resistant to attack by hydrocarbons and battery acid, and is able to retain its strength and flexibility over a wide range of temperatures. The present invention also extends to the method for carrying out the manufacture of the improved hose in which the cover is bonded to the reinforcement, and the reinforcement is bonded to the tube.

The invention may be carried into effect by fabricating an improved high-pressure hose, the constituents of which are specifically selected to employ a nylon resin as tube forming material,to employ a polyolefin resin as cover forming material, ~93~
and to employ a mixed yarn (or monofi:Lament) reinforcement which includes a hlgh tensile strength nylon yarn that is bondable to the nylon tube and a polyolefin yarn to which the cover may be bonded.

Nylon is selected for the tube since nylons are flexible over a moderately wide temperature range and are superior to many other synthetic and natural polymers in respect to their ability to retain refrigerants.

The selection of a proper cover material is somewhat more complex and the materials that have heretofore been utilized have ~`
not always met desired performance specifications. It has now been found that a combination of properties including flexibility over a wide temperature range, acid- and hydrocarbon-resistance, and ~ -~, :
low rate of moisture permeation can be found in some of the poly-olefins. Particularly useful are blends of polypropylene and either EPDM rubbers or SB~ rubbers ti.e., rubbers made from ethylene propylene diene monomer, and rubbers made as copolymers of styrene and butadiene). These may be compounded together or actually result from graft polymerization. ~olding grade poly- ;-propylenes, modified by EPDM rubber, are sold under several different trade names, including "Somel" offered by DuPont and "Profax" offered by Hercules. They are believed to be compounded from a major portion of polypropylene and a minor portion, e.g., up to 45% by weight, of EPDM rubbers.
The polypropylenes modified by SBR rubbers, such as "Telcar"
manufactured by B. F. Goodrich and "Kraton G" manufactured by Shell Chemical, are also very useful as a cover material for this type of hose.
The properties of the cover material as purchased from the above suppliers may be further modified where desirable by the addition of either polypropylene or polyethylene molding resins. These additions enhance the hardness of the cover but ~3~7~
decreases the flexibility of the material. Thus, selection o ~
the exact percentages of the components of the cover material i5 " ''.
somewhat o a 'trade-off' and should be made with the require-ments of a particular use well in mind. In all of the abo~e cases, the adhesion of the cover to the olefin yarn component is very good~
Nylon yarns, or monofilaments, are available that have high tensile strength and are preferred as the major component of the reinforcement yarns to give the hose a high burst strength. ;-~
Nylon yarns can readily be bonded to the nylon tube by solvents, but it is difficult to establish good bonds between nylon yarns and a polyolefin cover. For this reason, it is most desirable to -- :
include a minor portion of polyolefin yarns - or monofilaments in thereinforcement yarn so that the reinforcement can be melt-:! bonded to an extruded polyolefin cover.
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~}, The weight ratio of the mixed nylon/polyolefin reinforce-ment material is established by the respective denier of the , yarns selected. There is no criticallty to this weight ratio. It -can be understood that as the percentage of the polyolefin yarns `
is increased, bondability to the polyolefin cover will correspond-ingly increase, but on the other hand, the burst strength of the hose will be decreased. It follows that an optimum condition ~or any given hose will usually be achieved when the polyolefin ; yarns are present in the minimum amount necessary to obtain the ' desired adhesion with the cover so that burst strength will not ~, ~ be materially afected. As a general rule, this condition is ,- achieved through the use of about 20-45 weight percent polyolefin yarns - or monofilaments - and about 80-55 weight percent nylon yarn~ ~ or monofilaments. Percentages outside of these ranges can be utilized, but in such instances, either a loss in adhesion to the cover or a loss in burst strength of the hose must be accepted.

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Several different methods may be used to form the reinforcement Erom the several yarns - or monofilaments. One simple way, in the case of a braided reinforcement, is merely to use alternate bobbins of diEferent yarn. However, this does not provide for a very uniform distribution of the several yarns throughout the braid and therefore it is preferred to wind both yarns onto a common bobbin for use on a braiding machine. By this means, a more uniform distribution of the several yarns is `
achieved throughout the reinforcement.

The invention therefore, in its primary aspect, provides ;
a hose comprising a nylon tube, a textile reinforcement which is solvent-bonded to the tube, and a polyolefin cover which is melt-bonded to the reinforcement.
From yet another aspect the invention is to be understood to provide, as the reinforcement, two different types of yarns or monofilaments, one of these being selected for its high tensile strength, the other being chosen for its capability of bonding to the cover.
Preferably, the invention as outlined contemplates that the high tensile strength yarn or monofilament be nylon, and that the yarn or monofilament chosen for its bondability is a polyolefin.

From another aspect, the polyolefin is polypropylene, and this may be a rubbery polypropylene, for example wherein the polypropylene has been modified by a minor amount of EPDM rubber.
~ s an alternative the invention contemplates that the modifying material for the polypropylene is SBR rubber.
In yet a further aspect the invention will be seen to utilise a reinforcement containing between about 80~ and 55 by weight of nylon, and about 20 and 45 by weight of polyolefin.

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From another aspect the invention will be seen to provide a new method for making a hose, which me-thod employs the sequence o steps wherein a nylon tube is extruded, the surface of the tube is solvated with resorcinol, a reinforcement is brai~s~ over the surface of the tube containing a mixture of nylon and polyolefin yarns or monofilaments, and a polyolefin cover is finally melt-extruded over the reinforcement.
The invention contemplates that in the practice of the method as outlined, the polyolefin is a rubbery polypropylene which may be polypropylene modified with an EPDM rubher or with an SBR rubber.

The invention may further be shown to provide for the -pressing of the polyolefin cover material into intimate contact ^~
with the reinforcement during the melt-extruding.

The invention in a further aspect provides a hose consisting of a nylon tube, a braided reinforcement of nylon and polyolefin yarns or filaments solvent-bonded to the nylon tube, and having a polyolefin cover melt-bonded to the reinforcement.

The invention further contemplates that the hose above set forth will utilise as the polyolefin a major amount of polypropylene and a minor amount of EDPM rubber, or alternatively a minor amount of SBR rubber.

It is also contemplated that the hose product of the invention will utilise a reinforcement containing between 55% and 80% by weight of nylon.

The invention further contemplates that in the hose product above set forth, the polyolefin of the reinforcement will be pol~propylene.

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DESCRIPTION OF PREFERRED EMBODIMENTS

The construction of the improved hose is depicted in the -single Figure oE the drawing, which is an elevation partly in section of a composite hose 1 made in accordance with this invention. The hose includes a tube 2, a braided reinforcement 3 braided over the tube 2, and a protective cover 4 surrounding the reinforcement 3. The reinforcement 3 is bonded to the tube 2 and the cover 4 is bonded to the reinforcement 3.

EXAMPLE

A nylon tube was extruded from a melt of nylon mixture comprising nylon 6 and nylon 6/6 and a small percentage of plasticizer. The plasticizer was "ZYTEL 91A", the trade designation by which the substance is offered for sale by DuPont.
This tube had an I.D. of 0.320 inch and an O.D. of o.380 inch (8.13mm and 9.65mm). Bobbins were wound using one strand of a i nylon multi-filament yarn having a denier of 2520 and a poly-propylene yarn having a denier of 1680.

The bobbins so wound were used to apply a reinforcement in the form of a braid over the tube after the tube had first received a treatment of resorcinol to solvate its surface. Such surface treatment and braiding operations are well known in the art, as fully described, for example, in United States patent No. 2977839.

'rhe reinforced tube was then run through a conventional i . .. , ~, ; ~

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cross-head extruder without any surface pretreatment. The extruder was chaxged with polypropylene molding powders as modified with about 40% EPDM rubber (sold under the trade name "Profax" by Hercules). The extrusion die was maintained at a temperature of about 226C (440F) and the molten cover, as it passed through the die, was forced into intimate contact with the upper surface of the braided reinforcement.
The hose so produced had an I~D. of 7.94mm (0.3125 inch~, a buxst strength of 408 Kg/cm2 (5800 pounds per square inch) and had sufficient flexibility for use as an automotive air condition-~ 2~
ing hose. It had low permeation to ~r~ refrigerant, low A moisture permeation, excellent resistance to attack by 35~ sulfuric ~;
acid solution, moderate resistance to attack by oil and gasoline, and it retained its strength and flexibility over a range of from about -40C to about ~120C.

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A hose was prepared as in Examp:Le 1 except that the tube had an I.D. of 16.4mm and an O.D. of 17.9mm (0.645 inch and 0.705 inch) and the reinforcement which was wound on the bobbins had two strands of 2520 denier polypropylene yarn and one strand o~
7560 denier nylon yarn. The completed hose had an I.D. o~ 15.8mm (0.625 inch) and a burst strength of 450 Kg./cm2 (6400 pounds per square inch).

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Claims

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

1. A method for preparing a hose comprising the steps of extruding a nylon tube, solvating the surface of the tube with resorcinol, braiding a reinforcement comprised of a mixture of nylon and polyolefin yarns or monofilaments over the tube, and melt-extruding a rubbery polypropylene cover over the reinforcement, whereby the nylon component of the reinforcement is solvent-bonded to the hose and the polyolefin component of the reinforcement is heat-fused to the cover.

2. A method according to Claim 1 wherein the polypropylene is modified with an EPDM or SBR rubber.

3. A method according to Claim 1 or Claim 2 wherein the polyolefin cover material is pressed into intimate contact with the reinforcement during the melt-extruding step.

4. A hose comprising a nylon tube, a textile reinforcement bonded to the tube, and a polyolefin cover bonded to the reinforcement.

5. A hose according to Claim 4 wherein the textile reinforcement is a mixture of nylon and polyolefin yarns or monofilaments, wherein the tube is solvent-bonded to the nylon component of the reinforcement, and wherein the cover is heat-fused to the polyolefin component of the reinforcement.

6. A hose according to Claim 5 wherein the cover is a rubbery polyolefin.

7. A hose according to Claim 6 wherein the cover is polypropylene modified with an EPDM or SBR rubber.

8. A hose according to Claim 7 wherein the textile reinforcement contains between about 55% to 80% by weight of nylon.

9. A hose comprising a nylon tube, a braided reinforcement of nylon and polyolefin yarns or filaments solvent-bonded to the nylon tube, and a polyolefin cover melt-bonded to the reinforcement.

10. A hose according to Claim 9 wherein the polyolefin contains a major weight proportion of polypropylene and a minor weight proportion of EDPM rubber.

11. A hose according to Claim 9 wherein the polyolefin contains a major weight proportion of polypropylene and a minor weight proportion of SBR rubber.

12. A hose according to Claim 9, Claim 10, or Claim 11 wherein the reinforcement contains between 55% and 80% by weight of nylon.

13. A hose according to Claim 9, Claim 10, or Claim 11 wherein the polyolefin of the reinforcement is polypropylene.