Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to composite rein-
forced hose adapted to convey fluids under pressure and more
particularly to an improved hose of this type of construction
which has certain advantageous physical properties for use in
a particular application without substantial compromise of
other desirable physical properties.
Composite hoses are used extensively to conduct fluids
under pressure. The conventional flexible hydraulic hose has
a core tube extruded from a single synthetic resin, a fibrous
rein~orcing material about the core tube to support it against
radial expansion and elongation and a synthetic resinous pro-
tective sheath covering the fibrous material. Composite hoses
of this type are disclosed, for example, in U.S. Patents -
3,062,241; 3,332,447; 3,334,165; 3,251,381; 3,116,760 and ~ ~
3,722,550. Such composite hoses shoul~ be flexible, sub- ~ -
stantially kink resistant and also have a burst strength which
permits their use ~ith fluids under relatively hi~h pressure.
Moreover, the hose should be substantially resistant to chemical
attack by the fluid carried thereby. As indicated by the dis-
closures in the above patents, ~arious kinds of synthetic resins
have been proposed for making the different components of the
hose. The choice of synthetic resin used for making the core
tube, for example~ may vary from one hose to another depending
upon the relative importance of the physical properties. For
example, it may be desirable to select a resin like nylon 11
for the core tube where resistance to chemical attack by the
fluid carried by the hose is essential. Unfortunately, hoses
having a nylon 11 core tube are not as flexible as hoses
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3~17
having a core tube madP from another resin such as poly-
urethane. However, polyurethane is not as resistant to
attack by some fluids as nylon. So in deciding between a
nylon and polyurethane for a core tube, it is necessary to ~ -
compromise one property in favor of another. In some hoses
it is desirable to bond the core tube to the fibrous rein-
forcing material. Polyurethane is advantageous for the core
tube of the bonded hose because it can be treated with a
solvent to soften the surface of the core tube to form an
adhesive which bonds the fibrous strands to the core tube. ~ -
The polyurethane core tube can be used only in those hoses,
however, where the polyurethane provides sufficient chemical
resistance to permit the hose to carry the fluid involved.
Hence, with the prior art hoses it has been the practice to
select a core tube which has the most necessary properties
and to tolerate a compromise in other somewhat less important
properties. Such a procedure of cou:rse can not provide a hose
having optimum properties for many industrial applications.
It is therefore an object of this invention to provide
an improved composite reinforced hose for conveying fluids
under pressure which has those properties most necessary for
proper functioning without a major sacrifice in some of its
other properties. A more specific object of the invention is
to provide a composite reinforced hose adapted to convey fluids
under pressure having a structure which permits a greater lati- ~-
tude i~ selecting the various components of the hose to meet
the various conditions to which the hose is likely to be sub~
jected. Still another object of the invention is to provide a
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composite hose which combines optimum flexibility, kink
resistance, resistance to chemical attack and other desir-
able properties. A still further object of the invention
is to provide a composite reinforced hose having a core
tube which has the better properties of a plurality of
thermoplastic synthetic resins without substantial compro~
mise of other properties of the tube. A more specific object
of the invention is to provide improvements over the hydraulic
hoses of the prior art.
Other objects will become apparent from the following
description with reference to the accompanying drawing wherein
Figure l is a fragmentary side elevation, partially -~
cut away, of one embodiment of the invention; and
Figure 2 is a cross-section taken along the line 2-2
of Figure l.
The invention described in our aforesaid Canadian
Application Serial No. 217,401 provides a composite
reinforced hose having a core tube shaped from at least two
layers of synthetic thermoplastic resin which have different
physical properties melt fused directly together at an inter- ~ -
face into a wall which acts as a unitary structure, one or
more layers of a fibrous reinforcing material disposed about ;~
the core tube and a protective synthetic resinous sheath dis-
posed about the fibrous reinforcing material.
The invention broadly contemplates composite reinforced
hose having a core tube of two or more layers of synthetic
resin having different physical properties fused together into
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a single wall which will not separate into layers under the
conditions to which the hose is subjected while functioniny
as a hydraulic hose, an~ suitable fibrous reinforcing material
about the core tube and an external protective sheath.
The inventiGn described in our aforesaid Canadian
Application Serial No. 217,401 and the invention newly des-
cribed herein permit the manufacture of a composite reinforced
hose having some particularly desirable property without sub-
stantial compromi~e of other desirable properties. For exam-
ple, 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 elas-
tomeric polyurethane may be fused thereto as the outer sur-
face to provide improved flexibility and kink resistance.
The outer layer may be shaped from a resin from which an adhe-
sive can be made with a polar solvent to adhesively bond the
core tube to the reinforcing material and to improve the
strength of the hose. In such a hose, the relative thickness
of the nylon and polyurethane may be varied to further modify
the properties of the hose. In another embodiment of the in~
vention the inner layer of the core tube wall may be a solvent
resistant thermoplastic polymer fused to an outer layer which
forms the external surface of the core tube and has particles
of a conductive material such as carbon black dispersed there-
in to provide a hose for use in an airless high pressure paint
spray system. Hoses in which the core tube has a substantially
non-porous inner portion fused to a foam plastic or porous
outer portion may also be provided in accordance with the in-
vention.
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The core tube may be fabricated by any suitable pro-
cess which will produce melt fusion of two different layers
of synthetic thexmoplastic resins together to the extent that
the two layers will not separate at the interface under elon- -
gation 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 thermoplastic 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 por-
tion of the core tube wall is applied thereover and the two
molten synthetic resins are extruded through the same extru-
sion die.
It has been found that two layers of selected thermo-
plastic synthetic resin will melt fuse together along the in-
terface and become so firmly bonded together that the core
tube will not delaminate in a hose used to convey fluids under
high pressures even if the physical properties of the two layers
are significantly different. For example, nylon 11 and a
the~moplastic polyurethane will melt ~use together in accor-
dance with the process of the invention. Hence, the invention - -
contemplates a hose having a core tube with a layer of nylon
11 melt fused to a layer of thermoplastic substantially non- -
porous polyurethane. Usually, the nylon 11 layer will be
the innermost layer because of its chemical resistance. The
polyurethane layer imparts flexibility to the hose and may
also be used for making an adhesive to bond the core tube to
37~
the fibrous reinforcing layer so it is usually disposed on
the outside of the core tube.
Nylon 12 and thermoplastic polyurethane layers will
also melt fuse together. Because of its chemical resistance -
the nylon 12 layer may be used as the inner layer of a core
tube with a thermoplastic polyurethane outer layer.
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 poly-
urethane having a hardness of Shore A 80 to 95 may be co-
extruded to form a core tube. The harder thermoplastic poly- ~-
urethane has better chemical resistance than the softer one
so the harder one is usually the inner layer of the core tube.
The pres~nce of the layer of softer polyurethane improves the
flexibility o~ the hose. -
Still another hose provided by the invention has a -~-
core tube in which the innermost layer is a segmented co-
polyester such as "Hytrel" having a haraness of about Shore D
55 and an outer layer of segmented co-polyester such as "Hytrel"
having a hardness of about Shore A 90. Such a hose has advan-
tageous physical properties at elevated temperatures.
In another embodiment of the invention, a breathing
hose which must not only be 1exible and kink resistant but
must also be capable of carrying a ~luid without contamination
by the core tube is provided with a core tube having a layer
37~L~
of unplasticized nylon 11 on its inside and a layer of plasti-
cized nylon 11 on its outside.
~ hose suitable for conducting paint under high pres-
sure may be provided in accordance with the invention with
a core tube having an inner layer of nylon 11 or nylon 12
and a layer of thermoplastic polyurethane containing carbon
blac]c particles melt fused to the nylon 11 or 12 layer. The
nylon layer provides solvent resistance for conveying the
paint in the core tube and the polyurethane containing carbon
black particles is a semi-conductor for conducting static
electric charges to ground. In a variation of a hose of this
type the inner layer may be nylon 11 and the outer layer nylon
11 having carbon black dispersed therein.
The core tube may be adhesively bonded to the surface
of the reinforcing material by the application of an adhesive
material or by activating the surface of the core tube with a `~
solvent or softenin~ agent to form an adhesive in situ from
the resin on the outer surface of the core tube. For example, -`
a polyurethane surface of a core tube may be activated by
wetting it with a suitable polar solven~ such as, for example, ~ `
N-methyl pyrrolidone or the like. The rein~orcing fibrous
material is then applied under tenslon about the wet core
tube whereby the strands of reinforcing material become em~
bedded and partially encapsulated by the softened core tube
material. In this way, the fibrous reinforcing layer becomes
bonded to the core tube and the strength of the hose is
improved.
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"Hytrel" is a synthetic resin sold by E.I. duPont de
Nemours and Company. "Hytrel" is a segmented co-polyester
and is described n U.S. Patent 3,766,146.
It has been found that simultaneously coextruded pro-
perly selected synthetic thermoplastic resins of different
physical properties will become bonded together by melt fusion
and that an intermediate adhesive is not necessary. For ex-
ample, nylon will fuse to a thermoplastic elastomeric poly-
urethane if the two molten synthetic resins are fed separately
to an extrusion head and coextruded one over the other while
still molten. 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.
It has been unexpectedly discovered that the core tube
having two or more layers of synthetic thermoplastic resins
of different physical properties has an elongation at break
which is about equal to that of the more flexible resin in-
stead of an average of the two elongations or near that of
the resin having the lower elongation. In other words, the
melt fused layers remain melt fused together and break to- ;
gether at the break point of the resin having the greater
elongation. For example, a core tube was prepared by extrud-
ing a layer of nylon ll, 0.020 inch thick and while the nylon
11 was still molten, extruding a layer of thermoplastic -
polyurethane 0.025 inch think over the nylon ll layer. The
two layers were melt fused together.
* Trademark
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With the same apparatus, a core tube of a single
layer of the same nylon 11 having a wall-thickness of 0.020
inch was extruded and another core tube having a wall-thick-
ness of 0.025 inch was extruded from the same polyurethane
as used to make the dual extruded tube.
Test samples were cut from all three samples and the
elongation at break was determined. Surprisingly, the elonga-
tion at break of the laminated core tube was comparable to
that of the polyurethane core tube. The following experimen-
tal results were obtained: -
n = number of samples tested
X = average elongation, percent
S = standard deviation of population, percent
CI = 95 percent confidence interval, percent ~ -
Polyurethane Nylon 11Composite Tube ;
n 9 10 10 ~ ~
X 419 351 423 ~-
S 14 30 19 -~
CI 408-430 330-372 409-437
The confidence interval tells us that there is only one chance
in twenty that the total population average lies outside this
range. The confidence interval for the composite tube elonga- `~
tion is substantially higher than the range for the all-nylon
tube, while it overlaps the range for the all-urethane tube.
The elongation at break of the composite tube is at least 9.9 --
percent (and probably 20.5 percent) better than the elongation
of the all-nylon 11 tube extruded under the same conditions.
Other combinations of synthetic resins which may be
simultaneously co-axially extruded to form a core tube having
two or more layers melt fused together are segmented co-poly-
esters such as "Hytrel" and polyvinyl chloride compound and
a segmented co-polyester and a substantially non-porous thermo-
plastic polyurethane, and a mechanical mixture of an aromatic
polyester such as poly(tetramethylene terephthalate) and a
segmented co-polyester as one layer and polyvinyl chloride
polymer as the outer layer. The laminated core tubes com-
bining a layer of "Hytrel" or a mixture of a segmented co-
polyester and an aromatic polyester and a layer of polyv.inyl
chloride compound or polyurethane will usually have the layer
containing the segmented co-polyestex on the inside. A mech-
anical mixture of segmented co-polyester and polyurethane may
also be used for one of the layers, usually the outer layer.
The inner layer of the core tube may be a mixture containing
from about 5 to about 95% by weight polyurethane and 95 to
5% 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.
Examples of suitable thermoplastic aromatic polyesters
are "Valox", aromatic polyester sold by the General Electric
Co., "~enite", aromatic polyester sold by Eastman Kodak Co.
and "Celanex", aromatic polyester sold by Celenese Plastics
Co.
Any suitable relative proportions of aromatic poly-
ester such as "Valox'i and segmented co-polyester such as
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"Hytrel" may be used in the mixtures thereof extruded to
form a layer of the core tube. For example, from about 5~
to about ~0~ by weight aromatic polyester such as "Valox" may
be used. Any suitable mixture of polyurethane and co-segmented
polyester may be used, but it is preferred to use from about
99% to about 50~ thermoplastic polyurethane and 1% to about
50% by weight co-segmented polyester.
Referring now to the drawing, a composite hose 10 is
illustrated in Figures 1 and 2. The composite hose 10 has
a core tube 17 formed by the simultaneous coextrusion of a
layer of nylon 11 about 0.020 inch thick and a thermoplastic ~ ;
elastomeric polyurethane 12 such as "Pellethane" 90 A outer
layer about 0.025 inch thick. The two synthetic resins be-
come fused together at the interface to form a core tube which
will not delaminate when the hose 10 is used or conveying a
fluid under pressure. The outer surface of polyurethane of
core tube 17 is wet with N-methyl pyrrolidone to form ln situ
a gel-like material 13 on the surface thereof. A reinforcing
layer 14 of poly(ethylene terephthalate) ester filaments is
braided under tension around the core tube while the surface
of coxe tube 17 is activated by the solvent. The filaments
becoma embedded and partially encapsulated in the surace of `
the core tube 17 forming an elastomeric bond of the fibrous
reinforcing material with the core tube. A second reinforcing
layer 15 may be applied over layer 14. A protective poly-
urethane sheath is applied over fibrous reinforcing layer 15
by extrusion of a thermoplastic elastomeric polyurethane there-
over.
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1~3717
Any of the other core tubes disclosed as suitable
herein may be substituted in the foregoing embodiment of the
invention for core tube 17 and the core tube 17 may or may not
be bonded to the reinforcing layer depending upGn the particu-
lar requirements of the hose. For example, in some embodiments
of the invention the innermost layer of core tube 17 may be a
segmented co-polyester such as "Hytrel" and an outermost layer
of polyvinyl chloride polymer. Alternately, a mechanical mix-
ture of a thermoplastic aromatic polyester such as "Valox 310"
and a segmented co-polyester may be extruded as the innermost
layer and polyvinyl chloride polymer simultaneously coextruded
to form the outermost layer of core tube 17~ The mixture of
thermoplastic aromatic polyester and segmented co-polyester ~ -
may also be used as the innermost layer of core tube 17 with
a polyurethane or segmented co-polyester outer layer or two
mixtures of aromatic polyester and s~egmented co-polyester
having di~erent proportions of the components may be coex-
truded to ~orm the inner and outer layers.
The polyurethane sheath 16 and the polyurethane 12
of core tube 17 may be extruded from any suitable thermo- -
plastic polyurethane such as the one sGld under the trademark
"PELLETHANE" by the Upjohn Company. The thermoplastic poly-
urethane 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(tetrameth~lene ether) ~lycol,
suitable chain extender such as 1,4 butane diol, and 4,4'
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i~4.~7
diphenylmethane diisocyanate and polyurethanes prepared by
reacting an inner ester such as poly te-caprolactone) ester
and a suitable chain extender such as 1,4 butane diol with
an aromatic diisocyanate such as 4,4'-diphenylmethane diiso-
cyanate are preferred. The sheath 16 may also be extruded
from any other suitable synthetic resin such as, for example,
nylon or segmented co-polyester.
The fibrous reinforcing material may be formed by
braiding or by helically winding filaments of any sui~able ~-
synthetic resinous material, such as, for example, a poly- `
(alkylene terephthalate)ester fibrous reinforcing material
is disclosed in U.S. Patent 3,062,241. Such fibers have a
tenacity of about 7 to about 11 grams per denier and an
elongation at break of about 9% to about 17%. In a preferred
embodiment of the invention, the hose is provided wlth a re-
inEorcing layer of braided or helica:Lly wound filaments having
a tenacity of at least 12 grams per denier and up to about 25
grams per denier and an elongation at break of from about 2
to about 7%. An aromatic polyamide fiber marketed by E. I.
2~ duPont de Nemours & Co. under the trademark "Kevlar" and
known variously in the art as "Fiber B" and as an aramide
filament may be used. A fibrous reinforcing material of
aromatic polyamide fibers is preferred for composite hoses
having a high burst strength.
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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 extru-
sion head.
In one embodiment of the invention a hose having a
3/8 inch I.D. core tube 17 has an inner layer extruded rom ~-
a mixture containing about 90 parts "Hytrel" segmented co-
polyester and 10 parts "Valo~ 310" poly(tetramethylene tere-
phthalate)ester. Another layer about 0.010 inch thick of
thermoplastic polyurethane simultaneously co-axially extruded
with the "Hytrel" and "Valox" mixture is melt fused to the
inner layer. A single layer 14 of braided fibers of poly-
(ethylene terephthalate)ester is disposed about the core
tube 17 and bonded thereto. The fibxous reinforcing layer
is bonded to core tube 17 by solvating the surface of the
polyurethane with N-methyl pyrrolidone and braiding the fibers
on the wet core tube. A polyurethane sheath 16 about 0.025
inch is extruded over layer 14 and bonded thereto. The re-
sulting hose has an O.D. of 0.65 inch, a burst strength of
about 10,000 psi and can be bent to a radius of 0.75 inch
without kinking. A hose having a core tube of a single layer
of nylon and otherwise the same as the one just described,
has a minimum bend radius without kinking of about 1.75 inch.
A load of about 12 pounds is required to bend the described
embodiment of the invention having a core tube with an inner
layer of "Hytrel" and "Valox" and an outer layer of polyure-
thane 180 about a radius of 2 l/4 inch while 17 pounds are ~;
required to similarly bend the hose having a single layer
nylon core tube.
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3~7
In another embodiment of the invention, a hydraulic
hose has a core tube 17 with an I.D. o~ 1 inch. The core `~
tube 17 is formed by simultaneously co-extruding an inner
layer of a mixture of 85 parts "Hytrel" segmented co-poly-
ester and 15 parts "Valox 310" poly(tetramethylene terephtha-
late)ester 0.045 inch thick and an outer layer of polyvinyl
chloride polymer about 0.030 inch thick. A single layer 14
of poly(ethylene terephthalate)ester fibers is braided about
core tube 17 and bonded thereto with a solution of about 18
parts polyurethane dissolved in 82 parts methylene chloride `; ~ `
solvent. A polyurethane sheath 16 is extruded over the ~
fibrous reinforcing layer 14 and bonded thereto. The O.D. ~ ~-
of the hose is about 1.45 inches. The burst strength is
about 6800 psi and the minimum bend radius without kinking
is about 4 inches. The hose is more flexible than a hose
having a single layer nylon core tube as illustrated by the
fact that a load of 22 pounds will bend the hose of the inven~
tion 180 about a ~ 1/2 inch radius while a load of 31 pounds
is required to similarly bend the hose having a nylon core
tube.
It is apparent from the foregoing that the composite
reinorced hose provided by the invention has the advantage
over prior art hoses that a synthetic resin can be placed in
the core tube where its particular physical properties are
most needed without materially compromising other properties ~ ~
of the hose. For example, the synthetic resin for the inner ~ ~ -
layer of the core tube may be chosen or its chemical resis-
tance or to provide the hose with both chemical resistance
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1~37~7
and tensile strength while a more flexible synthetic resin
is chosen for the outer layer of the core tube to maintain
overall flexibility. The invention also permits variation
of the thicknesses of the layers of the core tube to provide
the hose with a particular property. The layers of the core
tube may also be chosen to provide novel combinations of
properties such as chemical resistance with electrical con-~ `
ductivity or insulation~ The cost of the hose can also be
reduced by using only a relatively thin layer of the more
costly but desirable synthetic resin only on that surface
of the core tube where it is needed. It is also possible ~ -
to provide a substantially non-porous synthetic resin layer
in combination with a foam layer such as a polyurethane foam `
layer. By proper selection of the combination of layers of
resins used in the core tube, it is also possible for kink `
xesistance in combination with a reinforcing material bonded
to the sheath.
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 de-
parting from the spirit and scope of the invention except as
it may be limited by the claims.
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