U.S. patent application number 15/763847 was filed with the patent office on 2018-09-27 for rubber and hydraulic hose comprising a inner tube made of the rubber material.
The applicant listed for this patent is Eaton Intelligent Power Limited. Invention is credited to Juergen Schmidt, Dipak Gopal Singh.
Application Number | 20180273721 15/763847 |
Document ID | / |
Family ID | 55132677 |
Filed Date | 2018-09-27 |
United States Patent
Application |
20180273721 |
Kind Code |
A1 |
Singh; Dipak Gopal ; et
al. |
September 27, 2018 |
RUBBER AND HYDRAULIC HOSE COMPRISING A INNER TUBE MADE OF THE
RUBBER MATERIAL
Abstract
A curing composition for rubber includes: a metallic co-agent
selected from the group consisting of zinc diacrylate and zinc
methacrylate; organic peroxide; sulfur; and a hydrotalcite
compound. The curing composition and a rubber matrix can be used to
make an uncured rubber composition. A cured rubber is obtainable by
curing the uncured rubber composition.
Inventors: |
Singh; Dipak Gopal; (Pune,
IN) ; Schmidt; Juergen; (Rastatt, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eaton Intelligent Power Limited |
Dublin 4 |
|
IE |
|
|
Family ID: |
55132677 |
Appl. No.: |
15/763847 |
Filed: |
September 22, 2016 |
PCT Filed: |
September 22, 2016 |
PCT NO: |
PCT/EP2016/072574 |
371 Date: |
March 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/22 20130101; C08K
13/02 20130101; C08L 9/02 20130101; C08K 3/06 20130101; C08L 7/00
20130101; C08K 5/14 20130101; B32B 25/14 20130101; C08K 5/098
20130101; B32B 2255/20 20130101; B32B 25/16 20130101; B32B 2264/108
20130101; B32B 2255/10 20130101; F16L 11/10 20130101; B32B 2307/306
20130101; B32B 25/00 20130101; B32B 2255/02 20130101; B32B 2307/712
20130101; B32B 2307/5825 20130101; B32B 15/06 20130101; B32B 25/02
20130101; B32B 25/10 20130101; B32B 15/14 20130101; B32B 2262/103
20130101; B32B 2307/54 20130101; B32B 5/02 20130101; B32B 2597/00
20130101; B32B 2307/7265 20130101; C08K 2003/2227 20130101; B32B
2250/03 20130101; B32B 2270/00 20130101; B32B 2264/102 20130101;
B32B 2307/40 20130101; B32B 2307/714 20130101; C08K 2003/222
20130101; B32B 15/18 20130101; B32B 2307/554 20130101; B32B
2255/205 20130101; B32B 1/08 20130101; C08K 3/26 20130101; C08L
21/00 20130101; C08K 5/14 20130101; C08L 9/02 20130101; C08K 3/26
20130101; C08L 9/02 20130101; C08K 3/06 20130101; C08L 9/02
20130101; C08K 5/098 20130101; C08L 9/02 20130101; C08K 13/02
20130101; C08L 9/02 20130101 |
International
Class: |
C08K 3/22 20060101
C08K003/22; C08L 7/00 20060101 C08L007/00; C08L 9/02 20060101
C08L009/02; B32B 1/08 20060101 B32B001/08; B32B 5/02 20060101
B32B005/02; B32B 25/10 20060101 B32B025/10; B32B 25/02 20060101
B32B025/02; B32B 25/16 20060101 B32B025/16; F16L 11/10 20060101
F16L011/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2015 |
IN |
3143/DEL/2015 |
Nov 12, 2015 |
GB |
1519958.1 |
Claims
1. A curing composition for rubber, comprising: a metallic co-agent
selected from the group consisting of zinc diacrylate and zinc
methacrylate; organic peroxide; sulfur; and a hydrotalcite
compound.
2. An uncured rubber composition comprising a rubber matrix and the
curing composition of claim 1.
3. The uncured rubber composition according to claim 2, wherein the
rubber matrix is selected from the group consisting of
Acrylonitrile butadiene rubber, hydrogenated nitrile butadiene
rubber, chlorosulphonated polyethylene, styrene-butadiene rubber,
or mixtures thereof.
4. The uncured rubber composition according to claim 2, wherein the
organic peroxide is present in 2 to 15 parts per hundred parts of
rubber.
5. The uncured rubber composition according to claim 2, wherein the
metallic coagent is present in 2 to 15 parts per hundred parts of
rubber.
6. The uncured rubber composition according to claim 2, wherein the
sulfur is present in 0.5 to 2.0 parts per hundred parts of
rubber.
7. The uncured rubber composition according to claim 2, wherein the
hydrocalcite compound is present in 2 to 20 parts per hundred parts
of rubber.
8. The uncured rubber composition according to claim 2, wherein
hydrogenated nitrile butadiene rubber is present in 5 to 20 parts
per hundred parts of rubber.
9. A cured rubber obtainable by curing the uncured rubber
composition according to claim 2.
10. A hydraulic hose comprising a tube comprising the cured rubber
according to claim 9; and a reinforcement layer.
11. The hydraulic hose according to claim 10, wherein the
reinforcement layer comprises brass-coated steel and directly
contacts an innermost layer.
12. The hydraulic hose according to claim 10, wherein the
reinforcement layer comprises spiral or braid wire
reinforcements.
13. A method for producing a cured rubber, comprising: providing
the uncured rubber composition according to claim 2; and heat
treating the uncured rubber composition.
Description
CROSS-REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a U.S. National Phase application under
35 U.S.C. .sctn. 371 of International Application No.
PCT/EP2016/072574, filed on Sep. 22, 2016, and claims benefit to
Indian Patent Application No. 3143/DEL/2015, filed on Sep. 30,
2015, and British Patent Application No. 1519958.1, filed on Nov.
12, 2015. The International Application was published in English on
Apr. 6, 2017 as WO 2017/055168 under PCT Article 21(2).
FIELD
[0002] The present patent application relates to a curing
composition, an uncured rubber composition comprising the curing
composition, a cured rubber obtainable by curing the uncured rubber
composition, and a method for curing the uncured rubber
composition. Finally, it relates to a hydraulic hose comprising a
inner tube made of the cured rubber.
BACKGROUND
[0003] A hydraulic hose transfers fluids under pressure from one
place to another. In general, hoses are made from one or a
combination of many different materials. The material of the hose
being used largely depends on the application and the performance
needed from the hose. Some of the common materials include nylon,
polyurethane, polyethylene, PVC or synthetic or natural rubbers. In
order to achieve a better pressure resistance, hoses can be
reinforced with fibers or stainless steel wires. Some of the
commonly used reinforcement methods include braiding, spiraling,
knitting and wrapping. Variations in hose can be due to its size,
rated temperature, weight, numbers of reinforcement layers, type of
reinforcement layers, rated working pressure, flexibility and
economics.
[0004] Typically, a hydraulic hose can be described as a composite
structure primarily made of alternate layers of rubber and steel.
For example, a hose can consist primarily of three layers namely:
Tube, Reinforcement and Cover.
[0005] Hydraulic hoses are used in a variety of industries like oil
and gas drilling, agricultural, construction, mining equipment,
heavy-machinery, household appliances, etc. Hydraulic hoses fail
due to various factors like pulling, abrasion, twisting of wire
layers due to multi plane bending, operating conditions, etc. The
operating conditions of the hose determine its service life. For
instance, extremes in temperature accelerate aging, frequent and
extreme pressure fluctuations accelerate fatigue life of hose.
[0006] Uptime/downtime plays, for example, a major role in the
mining segment. A typical hose assembly in mining lasts about from
3000 hours until 8000 hours, than the inner tube becomes brittle
and does no longer function. That means for the application 1 to 2
years, but with a big variance, meaning the hose could fail
sometimes even earlier, meaning down time on an open pit excavator.
If an open pit excavator goes down the whole mine stands still.
[0007] One approach for enhancing the maximal use time of hoses in
the above application fields has been to make the inner layer of
hydrogenated nitrile butadiene rubber (HNBR) which has both
physical strength and retention of properties after long-term
exposure to heat, oil and chemicals.
[0008] However, HNBR possesses a high tendency to creep. In
addition HNBR is very expensive.
[0009] Hence, there is the need to provide improved rubber
compositions for hydraulic hose applications.
SUMMARY
[0010] In an embodiment, the present invention provides a curing
composition for rubber, comprising: a metallic co-agent selected
from the group consisting of zinc diacrylate and zinc methacrylate;
organic peroxide; sulfur; and a hydrotalcite compound.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be described in even greater
detail below based on the exemplary figures. The invention is not
limited to the exemplary embodiments. Other features and advantages
of various embodiments of the present invention will become
apparent by reading the following detailed description with
reference to the attached drawings which illustrate the
following:
[0012] FIG. 1 shows a covalent bond caused by curing with an
organic peroxide in rubber.
[0013] FIG. 2 shows mono- or poly sulfide bonds in rubber.
[0014] FIG. 3 shows ionic bonds in rubber caused by the combination
of metallic coagent with organic peroxide.
[0015] FIGS. 4 and 5 show the tensile strength and elongation at
break tests of a tube made of the inventive rubber composition
versus two tubes made of rubber of different market compositions
after heating at 121.degree. C. in air.
[0016] FIGS. 6 and 7 show the tensile strength and elongation at
break tests of a tube made of the inventive rubber composition
versus two tubes made of rubber of different market compositions
after heating at 121.degree. C. in oil.
[0017] FIG. 8 show the compression set of a tube made of the
inventive rubber composition versus two tubes made of rubber of
different market compositions after heating at 100.degree. C. in
air.
DETAILED DESCRIPTION
[0018] According to a first aspect of the present invention a
curing composition for rubber is provided comprising: [0019] a
metallic co-agent selected from the group consisting of zinc
diacrylate and zinc methacrylate and mixtures thereof [0020] an
organic peroxide-sulfur [0021] a hydrotalcite compound.
[0022] The above curing composition is a hybrid system comprising
the above metallic coagent together with an organic peroxide and
sulfur. This combination brings about two different kinds of bonds
in the rubber matrix resulting in improved physical characteristics
of the cured rubber composition. This allows, for example, to
produce a new NBR (Acrylonitrile Butadiene rubber) inner tube which
is suitable for a hydraulic hose that has reasonable cost and
performs extremely well at high pressure and high temperature
condition in impulse tests. The combination of these curing agents
in the curing composition according to the present invention gives
the optimum properties required for a hydraulic hose in demanding
applications.
[0023] It is noted that crosslinking with an organic peroxide alone
would result in the formation of a covalent bond as shown in FIG.
1. This carbon-carbon bond is quite rigid and stable and accounts
for the lower tensile and tear strength of peroxide cured stocks
compared with sulfur vulcanizates. The good heat stability of this
covalent bond also explains the superior heat aged characteristics
of peroxide cured systems. In contrast, (poly) sulfide crosslinks
as shown in FIG. 2 formed in sulfur cure are thermally weak but are
mobile under stress and can slip along the hydrocarbon chain. This
mobility has been used to explain the superior tensile and tear
strength in sulfur cured stocks. However, sulfur cured rubber is
liable to degrade when exposed to heat.
[0024] In contrast thereto, without being bound to a specific
theory, it is believed that the metallic coagent-peroxide crosslink
bond is "ionic" as shown in FIG. 3. This ionic bond exhibits both
good heat aged stability and the ability to slip along the
hydrocarbon chain and reform.
[0025] Thus, this system embodies the characteristics of both the
peroxide and sulfur crosslink systems, giving high tensile and tear
strength and excellent heat aged properties.
[0026] Organic peroxides normally used in the rubber or plastic
industry may be used as the organic peroxide in the curing
composition of the first aspect of the present invention.
Generally, the organic peroxide is selected from the group
consisting of dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl
peroxide, cumene hydroperoxide, benzoyl peroxide,
2,4-dichlorobenzoyl peroxide,
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,1,1-di(t-butylperoxy)-3,3,5-tr-
imethylcyclohexane, t-butyl peroxybenzoate,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane and
1,3-di(t-butylperoxyisopropyl)benzene and mixtures thereof.
Preferably dicumyl peroxide, benzoyl peroxide or mixtures thereof
are used. Most preferred is dicumyl peroxide because of its
reasonable price and availability.
[0027] The metallic co-agent is selected from the group consisting
of zinc diacrylate and zinc methacrylate and mixtures thereof.
These metallic coagents create extremely strong adhesive bonds
between a variety of rubbers and untreated metal substrates. The
metallic coagents are readily compounded into the rubber stock
where they crosslink into the rubber when cured with peroxides.
Thus, they function as adhesion promoters as well as crosslinkers
to enhance both the adhesive and mechanical properties of the cured
rubber. Zinc diacrylate is the best coagent for adhesion, but zinc
methacrylate is a good alternative when further improved abrasion
resistance and tear strength is needed in addition to adhesion.
[0028] The curing composition according to the present invention
additionally contains sulfur. By adding sulfur, the tensile and
tear strength of the cured rubber is enhanced. In addition, the
adhesion with untreated metallic surfaces is improved. Wire
adhesion is extremely important as it leads to ease of assembly and
many theories also suggest it helps in achieving an effective load
transfer when applying impulses. This is especially true for brass
coated steel wire. Without being bound to a specific theory, it is
believed that the latter technical effect is due to entanglements
of sulfur bonds of the cured rubber with a CuS layer formed on top
of the brass (CuZn) coated steel. Thus, the cured rubber obtainable
by using the curing composition according to the first aspect of
the present invention is very suitable for producing hydraulic
hoses wherein the innermost layer made of rubber cured by the
curing composition according to the first aspect of the present
invention directly contacts a reinforcement layer made of brass
coated steel. As a result, such a hydraulic hose shows very little
creeping and the longevity is enhanced.
[0029] Finally, the curing composition according to the first
aspect of the present invention comprises also a hydrotalcite
compound for irreversible acid scavenging. In its naturally
occurring form, hydrotalcite is mined in small quantities in Russia
and Norway. Synthetic forms produced in commercial quantities may
generally be described by the formula (I)
g(1-x)Al.sub.x(OH).sub.2(C0.sub.3).sub.x/2n H.sub.20;
0.25<x<0.33. (I)
[0030] Thus, synthetic hydrotalcite as described by formula (I) may
include a mixture of various compounds within the given range of x.
Synthetic forms of hydrotalcite are available from several sources,
including DHT-4A2.RTM. and Alcamizer.RTM. from Kyowa Chemical
Industry Co., Ltd., Sorbacid.RTM. 911 from Sud-Chemie AG,
Hycite.RTM. 713 from Ciba Specialty Chemicals, and Hysafe.RTM. from
Huber. Preferably, a dehydrated hydrocalcite compound, such as
DHT-4A2-2.RTM. from Kyowa, is used due to its enhanced thermal
stability.
[0031] According to a second aspect of the present invention an
uncured rubber composition comprising a rubber matrix and the
curing composition as described in the curing composition of the
first aspect of the present invention is provided.
[0032] In a preferred embodiment of the present invention the
rubber matrix is selected from the group consisting of Acrylo
nitrile butadiene rubber, hydrogenated nitrile butadiene rubber,
chlorosulphonated polyethylene, styrene-butadiene rubber, or
mixtures thereof. Preferably, the matrix comprises Acrylonitrile
butadiene rubber. Acrylonitrile butadiene rubber (NBR) is a family
of unsaturated copolymers of 2-propenenitrile and various butadiene
monomers (1,2-butadiene and 1,3-butadiene). Although its physical
and chemical properties vary depending on the polymer's composition
of nitrile, this form of synthetic rubber is unusual in being
generally resistant to oil, fuel, and other chemicals (the more
nitrile within the polymer, the higher the resistance to oils but
the lower the flexibility of the material). More preferably, the
Acrylonitrile butadiene rubber is blended with a rubber selected
from the group consisting of chlorosulphonated polyethylene,
styrene-butadiene rubber, hydrogenated nitrile and mixtures
thereof.
[0033] Preferably, the uncured rubber composition according to the
second aspect of the present invention comprises 2 to 15 parts of
metallic co-agent per hundred parts of rubber.
[0034] Preferably, the uncured rubber composition according to the
second aspect of the present invention comprises 2 to 15 parts of
organic peroxide per hundred parts of rubber.
[0035] Preferably, the uncured rubber composition according to the
second aspect of the present invention comprises 0.5 to 2.0 parts
sulfur per hundred parts of rubber.
[0036] Preferably, the uncured rubber composition according to the
second aspect of the present invention comprises 2 to 20 parts
hydrocalcite compound per hundred parts of rubber.
[0037] Preferably, the uncured rubber composition according to the
second aspect of the present invention comprises 5 to 20 parts
hydrogenated nitrile butadiene rubber per hundred parts of
rubber
[0038] The uncured rubber composition according to the second
aspect of the present invention preferably comprises an
antiozonant. As antiozonant any compound with the ability to
decompose ozone on its surface into oxygen may be used. For
example, alumina effectively functions as an antiozonant for
polymers such as rubbers. This is called catalytic decomposition of
ozone, and this reaction generally occurs at temperatures lower
than that of thermal decomposition. Thus, by using an antiozonent,
the generation and growth of cracks and rubber chipping resulting
from ozone deterioration can be suppressed.
[0039] The uncured rubber composition according to the second
aspect of the present invention preferably comprises an
antioxidant. Examples of the antioxidant include, but are not
limited to, amine derivatives such as diphenylamine antioxidants,
p-phenylenediamine antioxidants, and naphthylamine antioxidants;
quinoline derivatives; hydroquinone derivatives; phenols
(monophenols, bisphenols, trisphenols, hindered phenols,
polyphenols, thiobisphenols); benzimidazoles; thioureas;
phosphites; and organic thioates.
[0040] Examples of the diphenylamine antioxidants include
p-isopropoxydiphenylamine, p-(p-toluenesulfonyl
amide)diphenylamine, N,N-diphenylethylenediamine, and octylated
diphenylamine.
[0041] Examples of the p-phenylenediamine antioxidants include:
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine,
N-isopropyl-N'-phenyl-p-phenylenediamine,
N,N'-diphenyl-p-phenylenediamine,
N,N'-di-2-naphthyl-p-phenylenediamine,
N-cyclohexyl-N'-phenyl-p-phenylenediamine,
N,N'-bis(1-methylheptyl)-p-phenylenediamine,
N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine,
N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine,
N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine,
N,N'-diaryl-p-phenylenediamines, hindered
diaryl-p-phenylenediamines, phenyl-hexyl-p-phenylenediamine, and
phenyl-octyl-p-phenylenediamine.
[0042] Examples of the naphthylamine antioxidants include
phenyl-a-naphthylamine, phenyl-p-naphthylamine, and
aldol-a-trimethyl 1,2-naphthylamine.
[0043] Examples of the quinoline antioxidants (quinoline
derivatives) include 2,2,4-trimethyl-1,2-dihydroquinoline polymer
and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline.
[0044] Examples of the hydroquinone antioxidants (hydroquinone
derivatives) include 2,5-di-(tert-amyl) hydroquinone and
2,5-di-tert-butylhydroquinone.
[0045] As for the phenol antioxidants (phenols), examples of the
monophenol antioxidants include 2,6-di-tert-butyl-4-methylphenol,
2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butylphenol,
1-oxy-3-methyl-4-isopropylbenzene, butylated hydroxyanisole,
2,4-dimethyl-6-tert-butylphenol,
n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl) propionate,
and styrenated phenol. Examples of the bisphenol, trisphenol, and
polyphenol antioxidants include
2,2'-methylene-bis(4-methyl-6-tert-butylphenol),
2,2'-methylene-bis(4-ethyl-6-tert-butylphenol),
4,4'-butylidene-bis(3-methyl-6-tert-butylphenol),
1,1'-bis(4-hydroxyphenyl)-cyclohexane, and
tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]met-
hane. Examples of the thiobisphenol antioxidants include
4,4'-thiobis-(6-tert-butyl-3-methylphenol), and
2,2'-thiobis-(6-tert-butyl-4-methylphenol).
[0046] Examples of the benzimidazole antioxidants (benzimidazoles)
include 2-mercaptomethyl benzimidazole. Examples of the thiourea
antioxidants (thioureas) include tributylthiourea. Examples of the
phosphite antioxidants (phosphites) include
tris(nonylphenyl)phosphite. Examples of the organic thioate
antioxidants (organic thioates) include dilauryl
thiodipropionate.
[0047] Among these, in terms of remarkably improving ozone
resistance, p-phenylenediamine antioxidants are preferred, and
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine is more
preferred.
[0048] In the uncured rubber composition according to the second
aspect of the present invention, the total combined amount of the
antiozonant for polymers and the antioxidant to be added per 100
parts by mass of the rubber component is preferably 1.5 parts by
mass or more, and more preferably 2.2 parts by mass or more. If the
total combined amount is less than 1.5 parts by mass, the effect of
preventing ozone deterioration may not be obtained sufficiently.
Also, the total combined amount is preferably 25 parts by mass or
less, and more preferably 23 parts by mass or less. If the total
combined amount is more than 25 parts by mass, the tensile
parameters may be reduced and brown discoloration may be
caused.
[0049] The uncured rubber composition according to the second
aspect of the present invention preferably includes wax leading to
an improvement in ozone resistance.
[0050] Examples of the wax include petroleum wax such as paraffin
wax, and vegetable wax such as carnauba wax, rice wax, candelilla
wax, japan wax, urushi wax, sugar cane wax, and palm wax. Among
these, petroleum wax is preferred and paraffin wax is more
preferred, because they provide excellent ozone resistance.
[0051] The amount of wax to be added per 100 parts by mass of the
rubber component is preferably 0.1 parts by mass or more, and more
preferably 0.5 parts by mass or more. If the amount is less than
0.1 parts by mass, an effective film may not be formed therefrom.
The amount is preferably 5 parts by mass or less, and more
preferably 3 parts by mass or less. If the amount is more than 5
parts by mass, discoloration on the rubber surface may not be
sufficiently suppressed.
[0052] The uncured rubber composition according to the second
aspect of the present invention preferably includes zinc oxide.
Zinc oxide effectively functions as an accelerator for the ozone
decomposition reaction of the antiozonant. The zinc oxide is not
particularly limited and may be one commonly used in the rubber
industry.
[0053] The amount of zinc oxide to be added per 100 parts by mass
of the rubber component is preferably 1 part by mass or more, and
more preferably 2 parts by mass or more. If the amount is less than
1 part by mass, then zinc oxide may not sufficiently function as
the accelerator for the ozone decomposition. The amount is
preferably 10 parts by mass or less, and more preferably 5 parts by
mass or less. If the amount is more than 10 parts by mass, then
zinc oxide is less likely to disperse and the breaking energy may
be reduced.
[0054] The ozone resistant rubber composition of the present
invention preferably includes a filler such as carbon black or
titane dioxide leading to an improvement in rubber strength.
[0055] The amount of filler to be added per 100 parts by mass of
the rubber component is preferably 10 parts by mass or more, and
more preferably 30 parts by mass or more. If the amount is less
than 10 parts by mass, the breaking energy and grip performance
tend to be reduced. The amount of filler is preferably 100 parts by
mass or less, and more preferably 70 parts by mass or less. If the
amount is more than 100 parts by mass, the dispersibility tends to
be reduced.
[0056] In addition to the above ingredients, the uncured rubber
composition according to the second aspect of the present invention
may appropriately contain a compounding agent commonly used in the
preparation of a rubber composition, such as silica, a silane
coupling agent, oil, stearic acid, and a vulcanization
accelerator.
[0057] According to the third aspect of the present invention a
cured rubber obtainable by curing the uncured rubber composition as
described in the second aspect of the present invention is
provided. Generally, the uncured rubber composition is cured by
applying heat. The curing can be performed by known methods, and is
not particularly limited. For example, the curing can be performed
by blending the uncured rubber composition, zinc oxide as a curing
agent, carbon black as a reinforcement, a curing accelerator, etc.
together, forming the resultant composition into a sheet or any
other desired shape, and carrying out a press molding thereof. The
heating conditions for curing reaction are not particularly
limited, and, for example, the curing can be effected at a
temperature for 130 to 210.degree. C. for a period for about 5 to
60 min.
[0058] According to the fourth aspect of the present invention a
hydraulic hose comprising a tube made of the cured rubber as
described in the third aspect of the present invention is
provided.
[0059] Generally, the hydraulic hose comprises three layers: the
innermost layer or tube, the reinforcement layer, and the cover
layer. Reinforcement allows the hose to handle fluid pressures and
pressure spikes, and prevents premature hose bursts when properly
used. It determines the working pressure of the hose. Hoses with
low working pressures normally use textile-fiber reinforcement,
while those handling higher pressures generally use high-strength
steel wire.
[0060] Steel-reinforced hoses, in turn, fall into two categories:
braid and spiral. Wire-braided hose handles working pressures to
6,000 psi, depending on size, with one or two braid layers. Spiral
hose, which generally handles high pressures in larger diameters,
has wire spiraled around the tube on a bias, with successive layers
laid at opposing angles. There are typically four or six layers of
steel reinforcement. In braid and spiral hose, rubber layers
separate layers of steel wrap to ensure good adhesion throughout
the hose wall.
[0061] The cover protects the tube and reinforcement from heat,
abrasion, and corrosion, as well as environmental deterioration
from heat, cold, UV light, and ozone. Covers are made from
synthetic rubber, fiber braids, or a fabric wrap, depending on the
application.
[0062] Preferably, the hydraulic hose comprises an innermost layer
made of the cured rubber and a reinforcement layer. The
reinforcement layer preferably comprises or consists of metal,
preferably steel. More preferably, the reinforcement layer
comprises spiral or braided steel wire. It is particularly
preferred to use brass coated steel in order to enhance the
adhesion with the innermost rubber layer.
[0063] According to a fifth aspect of the present invention a
method for producing a cured rubber is provided, comprising: [0064]
providing an uncured rubber composition as described in the second
aspect of the present invention [0065] heat treating the uncured
rubber composition.
[0066] In the following, the present invention will be demonstrated
based on a working example and comparative examples.
Working Example (Sample 31449)
[0067] A rubber composition was made as follows:
[0068] 31449 is the sample code for the new inner tube and its
composition is based primary on NBR matrix and the new hybrid
curing as described in the claim section.
[0069] The 31449 is mix in internal mixture and then is used in
extruder to form the tube. Extrusion is a process used to create
objects of a fixed cross-sectional profile. A material is pushed
through a die of the desired cross-section. For making the tube of
hydraulic hose in extrusion process a continuous cylindrical tube
is extruded. This tube is used to make braided or spiral hose.
Comparative Example 1 (K4890)
[0070] K4890 which is efficient sulfur cure system was taken as
comparative example 1
Comparative Example 2 (AS2831)
[0071] AS2831 which is conventional sulfur cure system was taken as
comparative example 2
Comparative Example 3 (ML3792-1)
[0072] ML3792-1 which is similar to 31449 but without sulfur.
Tensile Test and Elongation at Break Test
[0073] Time dependent tensile & elongation change was performed
on the cured rubber (1) 31449 (2) K4890 and (3) AS2831 in Hot air
and IRM903 oil at 121.degree. C. For both Hot air and IRM903 the
31449 sample showed lesser drop in tensile and elongation compared
to K4890 and AS2831. The test were performed as per ASTM D573
(Standard Test Method for Rubber--Deterioration in an Air Oven) and
ASTM D471 (Standard Test Method for Rubber Property--Effect of
Liquids). Please refer to the FIG. 4-7. FIGS. 4 & 5 shows the
tensile and elongation change of cured rubber compounds at
121.degree. C. in Hot air and FIG. 6-7 shows the tensile and
elongation change of cured rubber compounds at 121.degree. C. in
IRM903 oil.
Compression Set Test
[0074] Time dependent compression set was performed on the cured
rubber (1) 31449 (2) K4890 and (3) AS2831 at 100.degree. C. as per
ASTM D 395 (Standard Test Methods for Rubber Property--Compression
Set). The 31449 sample showed lesser set. Please refer to FIG.
8.
Wire Adhesion Test
[0075] Comparative rubber to brass coated steel wire adhesion was
performed on the cured rubber (1) 31449 and (2) ML3792-1 as per
ASTM D 1871 (Standard Test Method for Adhesion Between Tire Bead
Wire and Rubber). 31449 adhesion showed much high adhesion at 87
lbf where the ML3792-1 was at 7.9 lbf.
[0076] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. It will be understood that changes and
modifications may be made by those of ordinary skill within the
scope of the following claims. In particular, the present invention
covers further embodiments with any combination of features from
different embodiments described above and below. Additionally,
statements made herein characterizing the invention refer to an
embodiment of the invention and not necessarily all
embodiments.
[0077] The terms used in the claims should be construed to have the
broadest reasonable interpretation consistent with the foregoing
description. For example, the use of the article "a" or "the" in
introducing an element should not be interpreted as being exclusive
of a plurality of elements. Likewise, the recitation of "or" should
be interpreted as being inclusive, such that the recitation of "A
or B" is not exclusive of "A and B," unless it is clear from the
context or the foregoing description that only one of A and B is
intended. Further, the recitation of "at least one of A, B and C"
should be interpreted as one or more of a group of elements
consisting of A, B and C, and should not be interpreted as
requiring at least one of each of the listed elements A, B and C,
regardless of whether A, B and C are related as categories or
otherwise. Moreover, the recitation of "A, B and/or C" or "at least
one of A, B or C" should be interpreted as including any singular
entity from the listed elements, e.g., A, any subset from the
listed elements, e.g., A and B, or the entire list of elements A, B
and C.
* * * * *