CA1147637A

CA1147637A - Method of making a reinforced tubular article by completely impregnating a reinforced inner liner

Info

Publication number: CA1147637A
Application number: CA000355568A
Authority: CA
Inventors: Brian J. Holden
Original assignee: Dunlop Ltd
Current assignee: HIFLEX FLUIDHANDLING GROUP Ltd
Priority date: 1979-07-17
Filing date: 1980-07-07
Publication date: 1983-06-07
Also published as: ZA803980B; JPS5619723A; SE8005176L; FR2461569B1; DK307380A; FR2461569A1; JPH0125698B2; BE884321A; DE3027150A1; NL8003877A

Abstract

A B S T R A C T
A method of making a reinforced tubular article such as a hose comprises applying to a polymeric inner liner (e.g. of rubber or plastics) at least one reinforcement layer (e.g. of metal braid) and then immersing the resulting reinforced tube in liquid elastomer-forming reaction mixture to impregnate fully the layers or layer by fillng the interstices thereof.
The method is suitable for the production of hydraulic hose.

Description

1, REINFORCED T~BULAR ARTICLES
This invention relates -to an improved method for making a rein~orced tubular articles such as a hose~
According to the present invention, a method of making a reinforced tubular article comprises applying to a -tube of polymeric material which wil:l form the inner liner of the article at least one layer of material to provide reinforcement in the article and then fully impregnating the layer or layers wi-th a liquid elas-tomer-forming reaction mixture~
The me-thod of -the present inven-tion is particularly applicable where an inner liner is provided with a plurali-ty (at least two) of reinforcement layers and these reinforce-ment layers are then impregna-ted in a single operation~
"Fully-impregnating" means -that the in-ters-tices of the reinforcement are subs-tantially filled with impregnant and "fully impregnated" is to be construed accordingly.
One application of the method is in the manufacture of substantially flexible heavy duty hose, e g hydraulic hose, which may have a burst pressure of 10.3L~1 MN/m2 (1500 psi) or higher~ {Ref: Society of Automotive Engineers publica-tion "Tube5 Pipe, Hose and Lubrication Fittings - Standards, Recommended Practices, Informa-tion Reports.", Handbook Supplement HS 150, 1977 Edi-tion)~ In such a cons-truction -the densi-ty of -the reinforcement is usually relatively high, e g at least 60% and preferably, at least 75/0 coverage. Previously known methods of making this type of hose where a plurality of reinforcement 6~7

2~

layers has been use~ have necessitated a non-porous polymeric insula-tion layer between the layers of reinforcement, mainly to prevent cha~ing~ The need for such an insulation layer may be obvia-ted i~ -the method of the present invention is adopted since the comple-te impregnation of the inters-tices may substantially reduce or even prevent this chafingv One way -to make a cheaper hose could be to reduce the wall thickness of -the inner liner to a minimum~
Unfortunately, in hoses produced by known methods -there is often air in -the interstices of the reinforcement and i~
the inner lineris too thin the hose may ~ail due -to the inner liner expanding into these interstices~ This disadvan-tage may be overcome by use o~ the method of the present invention in that, because full impre~lation can be achieved, it is ~easible to reduce the thickness o~
the inner liner~
The inner liner is impervious -to -the impregnant and may be o~ an elastomeric ma-terial (e g a vulcanised rubber such as nitrile rubber, chlorinated polyethylene rubber or silicone rubber, or a thermoplastic rubber such as a polar elastoplastic linear block copolymer containin~t d k r~ e m~r J
polyester and polyether blocks available as 7Hytrel~ from Du pont) or a thermoplas-tic plastics material (e g a nylon such as Nylon ll)~(tr~e ~f k) The reinforcement may be of a tex-tile material such as nylon, a homo- or co-polymer o~ propylene, rayon, an aromatic polyamide (e g as available under the trade ~ffl~
Kevlar) or a polyester, or o~ glass or o~ a metal such as r~ 3~7 brass-coated s-teel wire~ The reinforcemen-t may comprise axial and spiral components which may be layered, woven9 knit-ted or braided to produce a balanced cons-truc-tionO
Alternatively, -the reinforcement may be applied by spiral winding.
If desiredg a material e g a textile scrim, permeable to -the liquid elastomer-forming impregnant used may be provided be-tween layers of reinforcemen-t and/or between -the inner liner and -the reinforcement layer or layers~
The impregnant is an elas-tomer~forming reaction mix-ture which is liquid at the temperature of impregnation and comprises ingredients which will chemically react and set to form an elastomer~ The impregnant may be one which will produce a polyure-thane elas-tomer or a silicone rubber or it may be a functional-group tipped liquid polymer e g an amine-tipped butadiene/acryloni-trile copolymer rubber ~e g as available ~mder the trade r~e Hycar from B F
Goodrich) in combination wi-th a suitable co-reactant such as an epoxy resin. The impregnant may contain o-ther additives e g at least one additive selected from plasticisers, extenders, pigments and surface -tension modifiers. An example of a polyurethane-forming reac-tion mixture is one comprising a relatively high m~lecular ~eight polyol, a rela-tively low molecular weight diol, an isocyana-te and optionally a catalys-t~
which will react -to form a polyurethane e g those quick-cure polyurethane forming compositions described in the specification of our British Patent No. 158546~ which comprise a liquid poly(propylene glycol) polyol having a molecular weight of more than 400, a liquid low molecular weigh-t diol having a molecular weight less than 250, a liquid di(isocyanatophenyl) methane and a catalyst selected from stannous sal-ts of carboxylic or mineral acids that are either in liquid form or are soluble in the polyols. The viscosity of the impregnant at the temperature of impregnation should not be too high, otherwise a substantially complete impregnation will prove difficult to achieve. Preferably the viscosity will be less than 10 Ns/m2 (10,000 centipoise), more preferably less than 5 Ns/m2 and advantageously less than 1 Ns/m2, at the impregnating temperature. In determining a sui-table viscosity for the impregnant the texture of the reinforcement will usually be taken into account as an open-textured reinforcement will obviously accept an impregnant of higher viscosity than will a close-textured one. One advantage of the method of the present invention is that it is not usually necessary to apply external pressure (e.g. by evacuating the vessel containing the impregnated article), other than any pressure due to the presence of the impregnant itself, in order to ensure complete impregnation.
After application to the reinforcement material, the liquid impregnant reacts and acts, this will usually be aided by the application of heat. Heat may be applied before, during and/or after the impregnation. If desired a fur-ther reinPorcement layer can then be applied -to the assemhly and the impregnation repeated~
Pre~erably the impregnation is carried out by passing the inner liner/reinPorcemen-t assembly through an impregnation vessel~ One way to obtain the desi.red degree oP impregnation oP the reinPorcement material is to apply at leas-t one reinforcement material layer~ e g as a braid3 to a tube oP inner liner material and -then to pass -the resulting -tubular ar-ticle vertically down through an impregnation vessel and out through an ~ri~ice in -the vessel beneath the impregnant level, which may also serve to remove excess impregnant ~rom the assembly~ If desired the impregnant can be set and then the assembly passed up through -the impregna-tion vessel so as -to apply a coating either of the same or oP a diPPerent material to the impregnant.
The inner liner/reinPorcement assembly may be substantially selP~upportingi e will subs-tantially re-tain its cross sectional shape during impregnation without the use oP a mandrel~ Alternatively it may be desirable to use a mandrel or to pressurise the article Prom within in order to support it e g where the end product may be a "lay Plat" hose.
One embodiment oP the present inv.ention will now be described by way o~ example only with rePerence to the accompanying Figure which is an elevational cross-section oP the impregna-tion oP an inner liner/reinPorcement assembly~

An impregna-tlon vessel 1 has an orifice 2 provided wi-th a rubber seal 3 sized so as to allow passage of a tubular assembly 4 whilst preventing escape of impregnant 5 ~rom the vessel, The tubular assembly 4 comprises an inner liner 6 enoased in one or more rein~orcemen-t layers 7O In use, the tubular assembly ~ is pulled down through the impregnant and out of the vessel 1 through -the seal 3 whi.ch also serves -to remove excess impregnant ~rom -the assembly 4, I~ desired the assembly 4 may be provided with a coating or coatings either o~ the same or dif~erent ma-terial to the impregnant e g by pulling the assembly vertically up through the impregnation vessel 1, The impregnant may be hea-t-set by means of` hot air applied to the assembly be~ore 7 during and/or a~ter impregnationu ~fter impregna-tion o~ the rein~orcemen-t and ei-ther be~ore or after the setting o~ the impregnan-t an outer cover~ e g o~ an elastomeric material, may be applied to the assembly e g by the technique o~ the preceding paragraph or by -the extrusion technique~
~ne aspect of the present invention is illust:rated by the following Examples in which the impregnation was carried out in the apparatus shown in the accompanying Figure, EXAMPLE I
A nylon tube having an internal diame-ter o~ 6,3 mm and external diame-ter o~ 9.4 m~l was covered with two layers o~ braided brass-plated steel wire to give an assembly having an internal diameter o~ 5.5 mm. The wire, 7~ 7 which has a diameter of 0~305 mm~ was applied from a conven-tional kraiding machine~
A 1~3 m leng-th of this product was washed by immersion in dichloromethane and, after drying, was threaded through a rubber seal in the bottom of an open-topped 300 ml capacity metal container so that 40 mm protruded below the seal ! The temperature of -the tube was raised to 40 4sc by passing hot air -through it~
The following polyurethane-forming composition was mixed andpouredinto the container, around the braided nylon tube~ c~e ~afk~
Propylan D-2122 (ex Lankro)2~ /e ~c!~k~ 75O0 g Ethane diol1 9~3 Anhydrous stannous chloride1 0075 Pigment dispersion 3373 ex Chemical Products (Cheshire) Ltd 3 Q O
Liquid silicone (available as Silicone DC 200~ 50 centistokes from Dow Corning) 0~3 Isonate 143L (ex Upjohn)3 60.0 1. The stannous chloride was dissolved in the ethane diol before mixing with the other ingredientsO
2. Ethylene oxide-tipped poly(propylene glycol) diol of molecular weight 20000

3~ Liquid mixture of pure MQD.IQ and a carbodiimide adduct of M~D.I.
This composition has an initial viscosity of 0~239 Ns/m2 at 21C measured with a Brookfield viscome-ter, Model LV~, using Spindle No 1 at 12 r,p:~mO None of the ingredients were dried and therefore the Propylan and ethane diol would ~k C~ucle mqr~

3~7 8.

be expected -to contain a small proportlon of water~
The hose was then pulled down, through the seal, at a speed of abou-t 14~2 mm/sec while the mix-ture was being stirred, until only approximately 150 mm remained above the seal~ After 20 minutes the liquid composi-tion had reacted and set to a solid elastomer and -the container and residue were cut away from -the hose~
This process was repeated but in -the reverse direction, i e pulling the hose upwards, to apply a further thin coat of polyurethane on the outside o~ the construction~ This coating procedure was repeated twice more to build up a coating thickness of approximately 0~5 mm~
Af-ter being lef`t to stand for 7 days, suitable connections were fitted to sections of the resul-ting hose~
A sample was subJected to impulse -testing using a square wave impulse pressure of 43,98 MN/m2 at a frequency of' 60 impulses/minute with hydraulic fluid at 93Co The sample had not failed after 333,300 impulse cycles and had a burst pressure of 227.5 MN/m20 EXAMPLE II
A braided nylon tube as described in Example I was washed by immersion in dichloromethane, dried~ and then threaded through a rubber seal in the bottom of an open topped 1-litre container so that about a 40 mm length protruded below the seal~ The temperature of the tube was raised to about 50C by the passage of hot air through it.

The following 3-par-t composition was prepared and the three components were then mixed -together a-t 60Co Component A ( Epoxy resin (available 100 g ) mixed as ~p.. ikote 815~ rom Shell) ) a-t 120C
~ 2,2-di(L~-hydroxy-phenyl) 2L~ g ~ cOole~
~ propane (av~ilable as ~ at 60C
Bisphenol-A~rom ~DH
~ Chemicals Ltd) Component B ( di-iso-octyl sebaca-te 100 g ~ mixed amine-termina-ted butadiene/ 3 g ~ heat acrylonitrile copolymer ~ to 60dC
(available as Hycar 1 300X16 ~ from B F Goodrich) Component C silicone liquid (av,ailable Co8 g as Silicone DC 200~50 Centistokes from Dow Corning The mix-ture (which had a viscosity at 60C of abou-t 5Ns/m2 measured on a Brookefield viscome-ter, model L~F, spindle ~L7 speed 60 r.pOm~) was p-oured in-to -the 1-litre con-tainer, around the braided nylon tubeO The -tube was pulled down through the seal at a speed of about 80 3 mm/sec ~m-til approximately 150 mm remained above -the seala The temperature of the assembly was maintained at about 50~
for a further 1~ hoursO When the hose was examined after this~ the braid was found to be substantially fully impregnatedO

rade ~c~rk)

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. A method of making a reinforced tubular article comprising, i) providing a tube of polymeric material, which will form the inner liner of the article, ii) applying at least one high density layer of a reinforcement material over the surface of said tube, said high density layer of reinforcement providing at least 60 coverage of said inner liner, and then iii) immersing the reinforcement in liquid elasto-mer forming reaction mixture to impregnate fully the reinforcement by filling the interstices thereof.

2. A method according to Claim 1 in which a plurality of layers of material to provide reinforcement in the article is applied to the tube of polymeric material and the layers are then impregnated in a single operation.

3. A method according to Claim 1 in which the liquid elastomer-forming reaction mixture comprises ingredients which will react and set to form a polyurethane.

4. A method according to Claim 1 or 2 in which the liquid elastomer-forming reaction mixture comprises a 11.
functional group-tipped liquid butadiene/acrylonitrile copolymer rubber and an epoxy resin.

5. A method according to Claim 1, 2 or 3 in which the viscosity of the liquid elastomer-forming reaction mixture is less than 10 Ns/m2 at the impregnating temperature.

6. A method according to Claim 1, 2 or 3 in which the viscosity of the liquid elastomer-forming reaction mixture is less than 5 Ns/m2 at the impregnating temperature.

7. A method according to Claim 1, 2 or 3 in which the viscosity of the liquid elastomer-forming reaction mixture is less than 1 Ns/m2 at the impregnating temperature.

12.

8. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer comprises metal.

9. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer comprises an aromatic polyamide.

10. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer comprises a braid.

11. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer is spirally wound onto the inner liner.

12. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer has an at least 60%

13.
coverage.

13. A method according to Claim 1, 2 or 3 in which the or each reinforcement layer has an at least 75%
coverage.

14. A method according to Claim 1, 2 or 3 in which there is a plurality of reinforcement layers and no non-porous polymeric insulation is applied between them.

15, A method according to Claim 1, 2 or 3 in which a material permeable to the liquid elastomer forming reaction mixture is provided between the inner liner and the reinforcement layer or layers and/or, where there is a plurality of reinforcement layers, between the reinforcement layers.

16. A method according to claim 1, 2 or 3 in which no external pressure is applied to the reinforced tubular ar-ticle during the impregnating step.

17. A method according to claim 1, 2 or 3 in which the reaction and set of the reaction mixture is aided by the application of heat.

18. A method according to claim 1, 2 or 3 in which the inner liner/reinforcement layer or layers assembly is passed down through an impregnating vessel containing the liquid elas-tomer-forming reaction mixture.

19. A hose comprising a core tube of polymeric material surrounded by and in contact with a reinforcement layer having at least 75% coverage, the interstices of said reinforce-ment layer being completely filled with an elastomer.

20. A method of making a reinforced tubular article comprising applying to a tube or polymeric material which will form the inner liner of the article a plurality of layers of metal braid having at least 75% coverage to provide reinforce-ment in the article and then fully impregnating the layers with a liquid polyurethane elastomer-forming reaction mixture hav-ing a viscosity of less than 10 Ns/m2 at the impregnating tem-perature.

21. A method according to claim 1, 2 or 3 in which the reaction mixture is substantially free of volatile diluent.

22. A method according to claim 3 in which the reaction mixture comprises a one-shot polyurethane-orming com-position.

23. A method according to claim 1, 2 or 3 in which impregnation of the inner liner/reinforcement layer or layers assembly is achieved by immersing it in a vessel containing the reaction mixture.

24. A method according to claim 1, 2 or 3 in which the inner liner/reinforcement layer or layers assembly is passed substantially vertically down through the liquid elastomer-forming reaction mixture.

25. A method according to claim 1, 2 or 3 in which the reaction mixture is capable of setting to a solid within 20 minutes of being applied to the reinforcement.

26. A method according to claim 1,2 or 3 in which there is substantially no expansion of the inner liner into the interstices of the reinforcement prior to setting of the reaction mixture.

27. A method according to claim ], 2 or 3 in which the inner liner/reinforcement layer or layers assembly is ad-vanced through the reaction mixture to achieve impregnation.

28. A method according to claim 1, 2, or 3 in which the inner liner/reinforcement assembly is substantially self-supporting, that is it is capable of substantially retain-ing its cross-sectional shape during impregnation in the ab-sence of a mandrel and in the absence of being pressurized from within.