Note: Descriptions are shown in the official language in which they were submitted.
37~6
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
reinforcing 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 3,06~,241;
3,33~,447; 3,334,165; 3,251,381; 3,116,760 and 3,722,550. Such ~;
composite hoses sho~ld be flexible, substantially kink resistant
and also have a burst strength which permits their use with fluids
under relatively high pressure. Moreover, the hose should be sub-
stantially resistant to chemical attack by the fluid carried there-
by. As indicated by the disclosures in the above patents, various
kinds of synthetic resins have been proposed for making the dif-
ferent 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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having a core tube made from another resin such as polyurethane.
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 reinforcing 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 ad- -
hesive 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 compro-
mise in other somewhat less important properties. Such a procedure
of course can not provide a hose having optimum properties ~or
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 ~or proper
functioning without a major sacrifice in some of its other proper-
ties. A more specific object of the invention is to provide a
composite reinforced hose adapted to convey fluids under pressure ~ -
having a structure which parmits a greater latitude in selecting
the various components of the hose to meet the various conditions
to which the hose is li~ely to be subjected. Still another object
of the invention is to provide a composite hose which combines -
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optimum flexibility~ kink resistance, resistance to chemical
attack and other desirable 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 compromise :
of other properties of the tube.
Other objects will become apparent from the following
description with reference to the accompanying drawing wherein
Fig~re 1 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 1.
The foregoing ob~ects and others are accomplished
in accordance with this invention, generally speaking, by pro-
viding 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 interface 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 sheathdisposed 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 a single
wall which will not separate into layers under the conditions to ~.
which the hose is subjected while functioning as a hydraulic hose,
any suitable fibrous reinforcing material abo~t the core tube and
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an external protective sheath of any suikable thermoplastic
polymer.
The invention permits the manufacture of a composite
reinforced hose having some particularly desirable property -
without substantial compromise of other desirable properties.
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 elasto-
meric polyurethane may be fused thereto as the outer surface to
provide improved flexibility and kink resistance. The outer
layer may be shaped from a resin from which an adhesive can be
made with a polar solvent to adhesively bond the core tube to the
reinforciny 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 invention 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 therein 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 accord-
ance with the invention.
The core tube may be fabricated by any suitable pro- ;
cess which will produce melt fusion of two different layers of
synthetic thermoplastic resins together to the extent that the
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~37~
two layers will not separate at the interface under elongation
and other conditions to which the hose will be exposed. The most
practical method of ma~ing the core tube is to supply two dif-
ferent synthetic thermoplastic resins or two different types o~
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 portion of the core tube wall
is applied thereover and the two molten synthetic resins are ex~
truded through the same extrusion die.
It has been found that two layers ofse~eGte~hermoplastic
synthetic resin will melt fuse together along the interface 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 ll and a thermoplastic polyurethane ~;
will melt fuse to~ether in accordance with the process of the in~
vention. ~Ience, the invention contemplates a hose having a core
tube with a layer of nylon ll 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 the
fibrous reinforcing layer so it is usually disposed on the out-
side 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.
lV~37~6
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
dif~erent 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 h~rdness
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. The presence of the layer of softer polyurethane
improves the flexibility of the hose.
Still another hose provided by the invention has a
core tube in which the innermost layer is Hytrel having a hardness
of about Shore D 55 and an outer layer of Hytrel having a hardness
of about Shore A 90. Such a hose has advantageous physical proper-
ties at elevated temperatures.
In another embodiment of the invention, a breathing hose
which must not only be flexible and kink resistant but must also
be capable of carrying a fluid without contamination by the core ~-
tube is provided with a core tube having a layer of unplasticized
nylon 11 on its inside and a layer of plasticized nylon ll on its ` -~
outside.
A hose suitable for conducting paint under high pressure
may bs 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 black particles
melt fused to the nylon 11 or 12 layer. The nylon layer provides
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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 ~ith a `
solvent or softening agent to form an adhesive ln 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 solvent such as, for example, N-methyl
pyrrolidone or the like. The reinforcing fibrous material is
then applied under tension about the wet core tube whereby the
strands of reinforcing material become embedded 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.
"Hytrel'i is a synthetic resin sold by E.I. duPont de
Nemours and Company. "Hytrel" is a segmented co-polyester and
is described in U.S. Patent 3,766,1~6.
It has been found that simultaneously coextruded
prop~rly selected synthetic thermoplastic resins of different
physical properties will become bonded together by melt fusion
and that an intermediate adhesive is not necessary. For example,
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nylon will fuse to a thermoplastic elastomeric polyurethane
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 la~ers of synthetic thermoplastic
resins of different physical properties has an elongation at
break which is about equal to that of the more flexible resin
instead 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 together
at the break point of the resin having the greater elongation.
For example, a core tube was prepared by extruding a layer of
nylon 11 0.020 inch thick and while the nylon 11 was still
molten extruding a layer of thermoplastic polyurethane 0.025 ~ `
inch thick over the nylon 11 layer. The two layers were melt ~ -
20 fused together. -~-
With the same apparatus, a core tube of a single
layer of the same nylon 11 havin~ a wall-thickness of 0.020
inch was extruded and another core tube having a wall-thickness
of 0.025 inch was extruded from the same polyurethane as used to
make the dual ext~uded tube.
Test samples were cut from all three samples and the
elongation at b~eak was determined. Surprisingly, the elongation
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at break of the laminated core tube was comparable to that of the
polyuretha~e core tube. The following experimental results were
obtained: -
n = number of samples tested
X = average elongation, percent
S = standard deviation of population, percent
CI = 95 percent con~idence interval, percent
Composite
Polyurethane Nylon 11 Tube
1011 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 composi~.e 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.
Referring now to the drawing, a composite hose 10 is ;
illustrated in Figures 1 and 2. Compasite 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 become fused together at
the interface to form a core tube which will not delaminate
when the hose 10 is used for conveying a fluid under pressure. ;
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The outer surface of polyurethane o~ core tube 17 is wet with
N-methyl pyrrolidone to form in 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 core tube 17 is activated
by the solvent. The filaments become embedded and partially
encapsulated in 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 may be applied over
layer 14. A protective polyurethane sheath is applied over
fibrous reinforcing layer 15 by extrusion of a thermoplastic
elastomeric polyurethane thereover.
Any of the other core tubes disclosed as suitable
herein may be substituted in the foregoiny embodiment of the ;
invention for core tube 17 and the core tube 17 may or may not -~
be bonded to the reinforcing layer dep~nding upon the particular
requirements of the hose.
The polyurethane sheath 16 and the polyurethane 12
of core tube 17 may be extruded from any suitable thermoplastic
polyurethane such as the old one sold under the trademark "Pelle-
thane" by the Up~ohn 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' diphenylmethane diisocyanate and polyurethanes prepared
by reacting an inner ester such as poly (s-caprolactone) ester
and a suitable chai~ extender such as 1,4 butane diol with an
aromatic diisocyanate such as
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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 or by helically winding filaments of any suitable
synthetic resinous material, such as, for example, a poly
(alkylene terephthlate)ester or nylon, such as nylon 6 or
nylon 66. Suitable nylon fibrous reinforcin~ material is dis- ~
10 closed 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 have a tenacity at room
temperature 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 with a
reinforcing layer of braided or helically wound filaments having
a tenacity at room temperature of at least 12 grams per denier
and up to about 2S grams per denier and an elongation at break
of from about 29~ to about 7%. An aromatic polyamide fiber
20 marketed by E.I. 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. Suitable reinforcing material ;~
containing synthetic aromatic polyamide filaments is disclosed
in our copending application No. 217,239 filed January 2, 1975.
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 ~or
feeding each synthetic thermoplastic resin to a single extrusion
head.
It is apparent from the foregoin~ that the composite
reinforced 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.
10 For example, the synthetic resin for the inner layer of the core -
tube may be chosen for its chemical resistance or to provide
the hose with both chemical resistance 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 conductivity 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 sur~ace
of the core tube where it is needed. It is also possible to pro- ~ ;
vide a substantially non-porous synthetic resin layer in combina-
tion 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 to provide for kink resistance
in combination with a reinforcing material bonded to the sheath. ;
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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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