GB1572717A

GB1572717A - Hose

Info

Publication number: GB1572717A
Application number: GB47287/76A
Authority: GB
Original assignee: Polymer Corp
Current assignee: Polymer Corp
Priority date: 1975-12-10
Filing date: 1976-12-10
Publication date: 1980-07-30
Also published as: JPS5271724A; IT1064507B; SE7613809L; CA1038780A; DE2654719A1; FR2334904A1

Description

(54) HOSE (71) We, THE POLYMER CORPOR ATION, a corporation organised and existing under the laws of the State of Pennsylvania, United States of America, of 2120 Avenue, Reading, Pennsylvania 19605, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to reinforced hoses.

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 paint spray guns, hose for flexible air conditioning lines as used in vehicles, hose for flexible hydraulic lines for use in articulated machinery, both movable and stationary, and many others.

Until the 1950's, practically all high pressure hoses utilized natural or synthetic rubbers to form the tube and the cover, and high tensile 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 alkalis; gas and vapor permeability; high and low temperature characteristics, weatherability; flammability; abrasion resistance; flexibility; and physical properties such as fatigue resistance, elongation, cold flow, and creep.

The reinforcement of the hose provides dimensional stability, increased burst strength and prevents kinking. Since the reinforcement is protected from environmental chemical attack by being sandwiched between the tube and the cover, it 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 reinforcement to the tube and the cover.

Nylon and polyester fibers are among those most commonly used for the reinforcement.

Since the reinforcement material is utilized to increase the strength of the hose, it is undesirable for the high tensile reinforcement to be weakened during any bonding operation. For this reason, thermal bonding may prove unacceptable and solvents should be used sparingly. Adhesives may be used to obtain a bonded construction, but generally they result in inferior bonds which permit the cover to be peeled away from the reinforcement or the reinforcement to be peeled away from the tube.

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 is particularly severe as so many requirements are imposed. At 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 permeation rate is desired so that water will not build up in the system. Since air conditioners 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 -40 F, as can be experienced in very cold climates, to temperatures of about 250-300"F which may be reached in the engine compartment.

The present invention provides a hose comprising a nylon tube, a reinforcement as herein defined bonded to and around the tube, and a polyolefin cover bonded to and around the reinforcement, the reinforcement comprising two different chemical types of yarn or monofilament and being bonded to the tube substantially only by yarns or monofilaments of the first type and to the cover substantially only by yarns or monofilaments of the second type.

The term "reinforcement" as herein defined means one or more plies of synthetic yarn and/or monofilament that are applied in tensioned relationship, e.g. by spiral wrapping, braiding or knitting, over the tube to increase the burst strength of the tube.

The yarns or filaments of the first type preferably of nylon, those of the other type are preferably of polyolefin.

The invention also provides a method for preparing a hose comprising the steps of extruding a nylon tube, solvating the surface of the tube with resorcinol, braiding over the surface of the tube reinforcement as herein defined containing a mixture of nylon and polyolefin yarns or monofilaments, and melt-extruding a polyolefin cover over the reinforcement.

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 polypropylenes in the polyolefins, polypropylenes in particular being preferred for the cover. Particularly useful are blends of polypropylene and either EPDM rubbers or SBR rubbers.

These may be compounded together or actually result from graft polymerization.

(The EPDM rubbers are so named since they are made from ethylene propylene diene monomer and the SBR rubbers are copolymers of styrene and butadiene.) Molding grade polypropylenes. modified by EPDM rubber, are sold under several different trade names, including "Somel" by DuPont and "Profax" by Hercules. They are believed to be compounded from a major portion by weight 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" (Trade Mark) manufactured by B. F. Goorich 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 decrease the flexibility of the material.

Thus, selection of the exact percentages of the components of the cover material is somewhat of a "trade-off" and should be made with the requirements of a particular use well in mind. In all of the above cases, the adhesion of the cover to a polyolefin reinforcement component is very good.

Nylon yarns (or monofilaments) are available that have high tensile strength and are preferred as the major component by weight (e.g. 55 to 80 wt.%) 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 by weight (e.g. 20 to 45 wt.%) of polyolefin yarns (or monofilaments) in the reinforcement yarn so that the reinforcement can be melt-bonded to an extruded polyolefin cover.

The weight ratio of the mixed nylon polyolefin reinforcement material is established by the respective denier of the yarns selected. There is no criticality to this weight ratio. It can be understood that as the percentage of the polyolefin yarns is increased, bondability to the polyolfin cover will correspondingly increase, but on the other hand, the burst strength of the hose will be decreased. It follow that an optimum condition for 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 affected. As a general rule, this condition is achieved through the use of 20-45 wt.% polyolefin yarns (or monofilaments) and 80-55 wt. % nylon yarns (or monofilaments). Percentages outside of these ranges can be utilized, but in such instance, either a loss in adhesion to the cover or a loss in burst strength of the hose may have to be accepted.

Several different methods may be used to form the reinforcement from the several yarns (or monofilaments). One simple way, in the case of a braided reinforcement, is merely to use alternate bobbins of different 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 single Figure of the accompanying drawing is an elevation, partially in section, of a composite hose 1 made in accordance with this invention. The hose includes a tube 2, a braided reinforcement 3 of two types of yarn or monofilament braided over the tube 2, and a protective cover 4 surrounding the reinforcement 3. The reinforcement 3 is bonded to the tube 2 by one of the said types and the cover 4 is bonded to the reinforcement 3 by the other.

Example 1 A Nylon tube was extruded from a nylon that was a mixture of 6 and 6/6 nylon and a small percent by weight of plasticizer (sold under the trade designation "Zytel 91A" by DuPont). This tube had an I.D. of 0.320" and an O.D. of 0.380". "Zytel" is a Trade Mark.

Bobbins were wound using one end of a nylon multifilament yarn having a denier of 2520 and a polypropylene 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 disclosed, for example, in U. S. Patent Specification No. 2,977,839.

The reinforced tube was then run through a conventional cross-head extruder without any surface pretreatment. The extruder was charged with polypropylene molding powder modified with about 40% EPDM rubber (sold under the trade name "Profax" by Hercules). The extrusion die was maintained at a temperature of about 440"F 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 a 5/16" I.D., had a burst strength of 5800 p.s.i., and had sufficient flexibility for use as automotive air conditioning hose. It had low permeation to "Freon" (Trade Mark) refrigerant, low moisture permeation. excellent resistance to attack by 35% sulfuric acid solution, moderate resistance to attack by oil and gasoline, and retained its strength and flexibility over a range of from about -40 F to about 250"F.

Example 2 A hose was prepared as in Example 1 except that the tube had an I.D. of 0.645" and an O.D. of 0.705" and the reinforcement which was wound on the bobbins had two strands of 2520 denier polypropylene yarn and one strand of 7560 denier nylon yarn. The completed hose has an I.D. of 5/8" and a burst strength of 6400 p.s.i.

WHAT WE CLAIM IS: 1. A hose comprising a nylon tube, a reinforcement as herein defined bonded to and around the tube, and a polyolefin cover bonded to and around the reinforcement, the reinforcement comprising two different chemical types of yarn or monofilament and being bonded to the tube substantially only by yarns or monofilaments of the first type and to the cover substantially only by yarns or monofilaments of the second type.

2. A hose according to claim 1 wherein the polyolefin of the cover comprises polypropylene.

3. A hose according to claim 2 wherein the polypropylene of the cover is one modified by a minor portion by weight of EPDM rubber.

4. A hose according to claim 2 wherein the polypropylene of the cover is one modified by a minor portion by weight of SBR rubber.

5. A hose according to any preceding claim wherein the yarns or monofilaments of the first type are of nylon.

6. A hose according to any preceding claim wherein the yarns or monofilaments of the second type are of polyolefin.

7. A hose according to claims 5 and 6 wherein the reinforcement is a braided reinforcement of the nylon and polyolefin yarns or monofilaments solvent-bonded to the nylon tube by way of the nylon yarns or monofilaments and melt-bonded to the polyolefin cover by way of the polyolefin yarns or monofilaments.

8. A hose according to claim 5, 6 or 7 wherein the reinforcement contains from 80% to 55% by weight nylon.

9. A hose according to claim 6, 7 or 8 wherein the reinforcement contains from 20% to 45% by weight polyolefin.

10. A method for preparing a hose comprising the steps of extruding a nylon tube, solvating the surface of the tube with resorcinol, braiding over the surface of the tube a reinforcement as herein defined containing a mixture of nylon and polyolefin yarns or monofilaments, and melt-extruding a polyolfin cover over the reinforcement.

11. A method according to claim 10 wherein the polyolefin of the cover comprises polypropylene.

12. A method according to claim 11 wherein the polypropylene of the cover is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. yarns (or monofilaments). One simple way, in the case of a braided reinforcement, is merely to use alternate bobbins of different 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 single Figure of the accompanying drawing is an elevation, partially in section, of a composite hose 1 made in accordance with this invention. The hose includes a tube 2, a braided reinforcement 3 of two types of yarn or monofilament braided over the tube 2, and a protective cover 4 surrounding the reinforcement 3. The reinforcement 3 is bonded to the tube 2 by one of the said types and the cover 4 is bonded to the reinforcement 3 by the other. Example 1 A Nylon tube was extruded from a nylon that was a mixture of 6 and 6/6 nylon and a small percent by weight of plasticizer (sold under the trade designation "Zytel 91A" by DuPont). This tube had an I.D. of 0.320" and an O.D. of 0.380". "Zytel" is a Trade Mark. Bobbins were wound using one end of a nylon multifilament yarn having a denier of 2520 and a polypropylene 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 disclosed, for example, in U. S. Patent Specification No. 2,977,839. The reinforced tube was then run through a conventional cross-head extruder without any surface pretreatment. The extruder was charged with polypropylene molding powder modified with about 40% EPDM rubber (sold under the trade name "Profax" by Hercules). The extrusion die was maintained at a temperature of about 440"F 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 a 5/16" I.D., had a burst strength of 5800 p.s.i., and had sufficient flexibility for use as automotive air conditioning hose. It had low permeation to "Freon" (Trade Mark) refrigerant, low moisture permeation. excellent resistance to attack by 35% sulfuric acid solution, moderate resistance to attack by oil and gasoline, and retained its strength and flexibility over a range of from about -40 F to about 250"F. Example 2 A hose was prepared as in Example 1 except that the tube had an I.D. of 0.645" and an O.D. of 0.705" and the reinforcement which was wound on the bobbins had two strands of 2520 denier polypropylene yarn and one strand of 7560 denier nylon yarn. The completed hose has an I.D. of 5/8" and a burst strength of 6400 p.s.i. WHAT WE CLAIM IS:

1. A hose comprising a nylon tube, a reinforcement as herein defined bonded to and around the tube, and a polyolefin cover bonded to and around the reinforcement, the reinforcement comprising two different chemical types of yarn or monofilament and being bonded to the tube substantially only by yarns or monofilaments of the first type and to the cover substantially only by yarns or monofilaments of the second type.

12. A method according to claim 11 wherein the polypropylene of the cover is

one modified by a minor portion by weight of EPDM rubber.

13. A method according to claim 11 wherein the polypropylene of the cover is one modified by a minor portion by weight of SBR rubber.

14. A method according to any of claims 10 to 13 wherein the polyolefin cover material is pressed into intimate contact with the reinforcement during the meltextruding.

15. A hose substantially as hereinbefore described with reference to the accompanying drawing.

16. A hose substantially as hereinbefore described in Example 1 or Example 2.

17. A method of making a hose, the method being substantially as hereinbefore described in Example 1 or 2.

18. A hose obtained by a method according to any of claims 10 to 14.