Note: Descriptions are shown in the official language in which they were submitted.
~209494
REINFORCED HOSE STRUCTURE HAVING
A TOUGH, FLEXIBLE COVER
Technical Field
The abstract is not to be taken as limiting the
invention of this application and in order to
understand the full nature and extent of the technical
disclosure of this application reference must be made
to the accompanying drawing and the following detailed
description.
The invention pertains to a reinforced hose
structure having a simplified cover and particularly to
said hose structure suitable for use in high pressure
applications such as may occur on rotary well-drilling
machines, although not limited thereto.
This invention provides a reinforced hose structure
comprising from the inside to the outside: a tube of
elastomeric material; two layers of helically extending
reinforcing members, the members of adjacent layers of
which have an opposite sense orientation relative to
the longitudinal axis of the hose, said layers being
encapsulated in elastomeric material; and a cover of
compounded carboxylated acrylonitrile-butadiene rubber
forming the radially outermost surface of the hose.
Preferably the hose has a cover of a compound that
contains carboxylated acrylonitrile-butadiene rubber
blended with polyvinyl chloride which contains 40 to
70% by weight of polyvinyl chloride. In the preferred
hose the elastomer material is characterized as having
a measured stress of at least 600 psi at 20 percent
elongation when measured to ASTM method D-412 and an
elongation at rupture of at least 15n percent when
measured according to ASTM method D-412 and a Young's
modulus of at least 2000 psi when measured according to
ASTM method D-1053;
,~.~
~2094~4
lA
Background
Hose of relatively large diameter, for example. 2
to 4 inches internal diameter, are commonly used to
transport or convey drilling fluids or muds in
well-drilling machines. This hose must be capable of
withstanding considerable internal pressure, for
example, from about 5,000 to in excess of 20,000 pounds
per square inch, and must be flexible enough to couple
the standpipe of the drilling derrick to the kelly
which moves downwardly with the drill pipe as drilling
proceeds and is raised to permit attachment of each
lS section of drill pipe. Present hose constructions for
this and other high pressure applications typically
include a radially innermost tube of elastomeric
material and one or more plies of textile fabric as a
reinforcement for the elastomeric tube. These plies
reinforce the tube to prevent the tube from being
pushed out between the main reinforcing cables of such
hose, particularly where the hose is bent to a
,f.,
1209494
re1ativelv small radius, thus causing the main cables
t~ be spread apart relative to one another along that
part of the hose wall which is most distant from the
center of curvature of the bend.
Also, in most high pressure hose the special
wrapped steel cable has at least one or more layers of
elastomeric fabric covering the cable and then at least
one ply of tie gum to get proper adhesion between the
cover ply and the main body of the hose. Generally,
the cover ply also contains fabric.
Disclosure and practice of the invention
According to the present invention, there is
provided a reinforced hose structure which is greatly
simplified when compared to known hose structures which
are able to meet the stringent requirements of rotary
drilling operations and especially is this so in the
cover ply area.
The invention is illustrated in the accompanying
drawing in which Figure 1 is a cross-sectional view of
a hose structure according to the invention which
contains an optional fiber layer.
Referring now to Figure 1, there is shown a
preferred embodiment of a hose structure io according
to the invention. Proceeding from the inside to the
outside of said hose there is provided nearest the
longitudinal axis 11 a tube 12 of elastomeric material
having properties which will be further described
herein for the more severe or special operational
conditions. Immediately radially outwardly of the tube
12 there are provided at least two layers 16 and 18 of
steel cables 15. The layers 16, 18 of cables are
embedded in elastomer material 14. Overlying the
layers 16, 18 of helically extending steel cables 15
are one or more plies 20 of rubberized textile
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material. Overlying the optional textile plies 20 is a
cover 22 of a specially compounded carboxylated
acrylonitrile butadiene rubber which forms the radially
outermost surface of the hose.
Rotary drilling hose commonly experiences high
pulsating pressures, abrasive muds, air, water and
hydrocarbon fluids. These factors must be kept in mind
in selecting the elastomer of which the tube 12 is to
be compounded. An acrylonitrile/butadiene rubber-based
elastomeric material is particularly suitable for this
application, although other elastomers, including
acrylonitrile-isoprene copolymers, styrene-butadiene
copolymers, polyisoprenes, polychloroprenes, or blends
of these may be employed, depending on the nature of
the fluid intended to be conveyed through the hose and
the chemical resistance thus required of the tube
elastomer.
The elastomeric material of the tube 12 preferably
has a tensile stress of at least 600 psi at 20 percent
elongation when measured according to ASTM method D-412
and elongation at rupture of at least 150 percent when
measured according to ASTM method D-412, and a Young's
modulus of at least 2000 psi when measured according to
ASTM method D-1053, and more preferably has a tensile
stress of at least about 1000 psi at 20 percent
elongation when measured according to ASTM method D-412
and an elongation at rupture of at least 200 percent
when measured according to ASTM method D-412, and a
Young's modulus of at least 3500 psi when measured
according to ASTM method D-1053.
In hose suited for high pressure rotary drilling
apparatus, the tube 12 should have a thickness of at
least 3/16 inch as measured along a radius of the hose
10 proceeding from the longitudinal axis 11.
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The requisite physical properties as herein
described for the elastomeric material of the tube 12
may be obtained with compounds based on elastomers
selected from the group given hereinbefore in
combination with a reactive resin system capable of
polymerizing in situ within the compounds. These resin
systems will be further described herein.
For use in rotary drilling applications, an
elastomeric compound of the following general
formulation exhibits the requisite physical properties
for use in the tube 12 of a hose according to the
present invention: 75 to 100 parts by weight of
acrylonitrile-butadiene copolymer of acrylonitrile-
isoprene copolymer having a minimum of 20 percent by
weight of acrylonitrile content and 25 to 0 parts by
weight of an elastomer selected from the group
consisting of styrene-butadiene copolymer,
polychloroprene or polyisoprene; and per each 100
weight parts of total elastomer, from about 10 to 50
weight parts and, more preferably, from about 25 to 35
weight parts of adhesive-treated cellulosic fibers
having a length range of from about 1 to 3 mm. and a
length-to-diameter ratio of from about 100 to 200, an
example of such fibers being SantowebTM K fibers
available from Monsanto Company; from about 10 to 50
weight parts and more preferably from about 20 to 30
weight parts of a reactive phenol formaldehyde resin
capable of polymerizing with hexamethylene tetramine,
an example of such a resin being DurezrM 12686 resin
available from Hooker Chemical Corporation; from about
0.5 to 5.0 weight parts and, more preferably, from
about 1.6 to 2.4 weight parts of hexamethylene
tetramine, from about 25 to 100 parts and, more
preferably, from about 40 to 75 weight parts of a
reinforcing filler, for example, AS~I N-330 carbon
~Z09494
black and/or hydrated silica; from about 0.5 to 2.0
weigh~ parts of an antioxidant, for example,
polymeriæed 2,2,4-trimethyl-1,2-dihydroquinoline; from
about 3 to 10 weight parts of zinc oxide; from about
0.5 to 2.0 weight parts stearic acid; from about 10 to
40 weight parts of rubber plasticizer for example,
dioctylphthalate; and a typical sulfur cure and
accelerator system such as from about 0.5 to 3.0 weight
parts sulfur and from about 0.5 to 2.0 weight parts
sulfenamide accelerator, for example N-oxydiethylene-
2-benzothiazylsulfenamide.
Other well-known rubber plasticizers can be used,
for example, polyethers, adipates, and azelates,
depending upon the elastomer or elastomer blends
selected. The choice of plasticizer and-the level of
plasticizer are matters well known to those skilled in
the art of elastomer compounding.
Reactive phenolic resins are those capable of
polymerizing with a methylene donor, for example,
hexamethylene tetramine, tetraethylene tetramine,
hexamethoxymethylmelamine.
Reactive phenolic resins suitable for the
elastomeric material of the tube 12, preferably either
contain hexamethylene tetramine, or the hexamethylene
tetramine is added to the compound. The resins should
have a melting or softening point below 250 degress F.
Commercial sources include "Arofene"lM resins from
Ashland Chemicals, Division of Ashland Oil Company,
"Durez"TM resins from Hooker Chemical Corporation,
"Alnovol"rM resins from American Hoechst Corporation,
Industrial Chemicals Division.
While reactive phenolic resin systems are
preferred because of their compatibility with
sulfur-base curing systems, other reactive resin
systems t~reactive~ meaning capable of polymerizing)
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m~v be usl~(l in place of the phenolic resins, for
ex~lmplc:
shellac plus zinc oxide;
resorcinol aldehyde resins plus a methylene
donor such as hexamethylene tetramine;
catechol aldehyde resins plus a methylene
donor such as hexamethylene tetramine;
monomers containing isocyanurates plus
organic peroxides;
monomers containing acrylates plus organic
peroxides;
monomers containing allylic double bonds plus
organic peroxides.
Representative examples of monomers useful in the
practice of the present invention include:
allyl methacrylate
di allyl fumarate
triethylene glycol dimethacrylate
1,3-butylene glycol diacrylate
1,6-hexane diol dimethacrylate -
pentaerythritol tetra acrylate
ethoxylated bis phenol A dimethacrylate
trimethylol propane trimethacrylate
tri allyl cyanurate
tri allyl isocyanurate
tri allyl trimellitate
di allyl phthalate
Representative examples of organic peroxides
useful in the practice of the present invention
include:
dicumyl'peroxide
di-t-butyl peroxide
2,4 pentane dione peroxide
2,5-dimethyl-2,5-bis(benzoyl peroxy) hexane
n-butyl-4,4-bis(t-butylperoxy) valerate
~%09494
1,1-di-t-butylperoxy-3,3,5-trimethyl cyclohexane
All of the above-listed resin systems are believed
to be capable of providing adequate reinforcement of
elastomers for use in a hose including a tube 12
according tc the invention, although the range given
for the reactive resin system in the beforementioned
general formulation may not be the range required when
other elastomer or resin systems are selected.
Determination of the proper amount of reactive resin
system is believed to be well within the capability of
one skilled in the art of elastomer compounding. Also,
as will be revealed in other exemplary formulations
provided herein, the use of short discrete fibers is
not believed to be requisite although their use is
preferred in rotary drilling hose since they provide an
extra margin of safety through a different reinforcing
mechanism.
The following are examples of compounds which
produce the requisite physical properties described
hereinbefore. All recipes are given by weight ratios
in parts per 100 parts of elastomer.
Example 1
100 acrylonitrile/butadiene copolyer (32 weight
percent acrylonitrile content)
50 ASTM N-330 carbon black
10 hydrated silica
0 di octyl phthalate
1 antioxidant
5 zinc oxide
1 stearic acid
30 adhesive treated cellulosic fibers
( Santoweb~MK)
25 phenol formc~ldehyde resin (Durez~ 12686)
2 hexamethylene tetramine
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1.5 sulfur
l s~ enamide accelerator
~ hen the above ingredients were compounded and
vulcanized 60 minutes at 145C., the following physical
properties were observed.
Test
Test Designation Procedure Value
Tensile stress at 20% elongation D-412 1000 psi
Elongation at rupture D-412 290%
Young's modulus D-1053 3700 psi
Example 2
The following compound is not recommended for use
in the tube of a rotary drilling hose due to low
resistance to petroleum base drilling fluids; however,
it could be used in a high pressure water hose.
100 styrene-butadiene copolymer (23 weight percent
styrene)
85 ASTM N-330 carbon black
15 aromatic petroleum base oil
3 antioxidant
3 zinc oxide
l stearic acid
20 phenolic resin (~lnovolrM VPN-16 from Hoechst)
1.6 hexamethylene tetramine
1.8 sulfur
1.2 sulfenamide accelerator
When the above ingredients were compounded and
vulcanized 60 minutes at 145C., the following physical
properties were observed.
Test
Test Designation Procedure Value
Tensile stress at 20% elongation D-412 750 psi
Elongation at rupture D-412 260%
Young's modulus D-1053 6900 psi
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Example 3
100 acrylonitrile-butadiene copolymer (39 weight
% acrylonitrile)
5 zinc oxide
1 stearic acid
40 ASTM N-550 carbon black
20 trimethylol propane trimethacrylate
4.40 weight percent dicumyl peroxide on an inert
iller (Di-CupTM40C, available from
l~ercules, Inc.)
When the above ingredients were compounded and
vulcanized 30 minutes at 155C., the following physical
properties were observed.
Test
15 Test Designation Procedure Value
Tensile stress at 20% elongation D-412 800 psi
Elongation at rupture D-412 160%
Young's modulus D-1053 2500 psi
When manufacture of rotary drilling hose or the
like is contemplated, an acrylonitrile containing
elastomer is highly desirable for the tube. The
acrylonitrile content of the elastomer may vary from 17
to 50 percent by weight, depending on the degree of
?5 chemical resistance desired, with an acrylonitrile
content of at least 20 percent being preferred.
The layer 14 of elastomer in which the steel
cables 15 are embedded is chosen to promote adhesion to
the steel cables and to the radially inwardly located
tube 12 of elastomeric material and the radially
outwardly located rubberized textile plies 20.
Suitable compositions for this application are well
known to one skilled in this art and will not be
further described here.
~209~94
1(~
The o~lter cover 22 of special elastomeric material
is prefcrably 1/~" (.38 cm) to 3/16" (1,14 cm) thick to
provide suitable protection to underlying hose body.
Example 4
A cover stock was prepared by compounding on a
mill 85 parts of polyvinylchloride, 92.4 parts of a
carboxylated acrylonitrile butadiene rubber, AC9N64
made by Polysar Chemical Co., with a mixture of 10
parts of carboxylated acrylonitrile butadiene rubber,
2.0 parts stearic acid, 50 parts carbon black, 2.00
parts internal lubricant, 5.00 parts furfural alcohol,
1.50 parts of furfural-butadiene oily adduct
and 0.50 parts of tetramethyl thuram monosulfide, and
extruding as a ply about 0.6 centimeters thick on the
hose body and then curing preferably about 60 to 90
minutes at 160C.
Example 5
Another cover stack was prepared according to the
teachings of Example 4, except 70 parts of polyvinyl
chloride and 231 parts of carboxylated acrylonitrile
butadiene was used. This covers stock had a Shore of
hardness of 72 whereas the one of Example 4 had a Shore
hardness of 74, but the Taber abrasion was slightly
higher. The better tear values as measured by the ASTM
Die C method are obtained where the cover stock
contains about 40 to 70% polyvinyl chloride in the
carboxylated acrylonitrile butadiene. Thus, these
compositions have very desirable ASTM Die C tear
resistance and are highly preferred, other blends may
be used too.
While certain representative embodiments and
details have been shown for the purpose of illustrating
the invention it will be apparent to those skilled in
~0949~
the art that various changes and modifications may be
made therein without departing from the scope of the
invention.
