U.S. patent application number 09/862149 was filed with the patent office on 2002-01-03 for rubber mixtures for producing highly reinforced vulcanisates with low damping behaviour.
Invention is credited to Scholl, Thomas.
Application Number | 20020000280 09/862149 |
Document ID | / |
Family ID | 7643323 |
Filed Date | 2002-01-03 |
United States Patent
Application |
20020000280 |
Kind Code |
A1 |
Scholl, Thomas |
January 3, 2002 |
Rubber mixtures for producing highly reinforced vulcanisates with
low damping behaviour
Abstract
The rubber mixtures according to the invention consisting of a
rubber, a filler and a specific sulphurized mineral oil are
suitable for producing shaped vulcanizates, in particular for
producing tires with reduced rolling resistance and high resistance
to wet skidding, and tires with particularly reinforced side walls
("run flat tires").
Inventors: |
Scholl, Thomas; (Bergisch
Gladbach, DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7643323 |
Appl. No.: |
09/862149 |
Filed: |
May 22, 2001 |
Current U.S.
Class: |
152/519 ;
585/5 |
Current CPC
Class: |
B60C 17/0009 20130101;
C08K 5/36 20130101; Y02T 10/86 20130101; C08K 5/01 20130101; B60C
1/0025 20130101; Y02T 10/862 20130101; B60C 1/0016 20130101; C08K
5/01 20130101; C08L 21/00 20130101; C08K 5/36 20130101; C08L 21/00
20130101 |
Class at
Publication: |
152/519 ;
585/5 |
International
Class: |
C10L 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2000 |
DE |
10025625.2 |
Claims
1. Rubber mixtures consisting of a rubber, a filler and 0.1 to 75
parts by weight, based on 100 parts by weight of rubber, of a
sulphurised mineral oil, wherein the sulphurised mineral oil is
obtained by reacting an aromatic-containing mineral oil with
sulphur.
2. Rubber mixtures according to claim 1, characterised in that the
sulphurised mineral oil has a bound sulphur content of 2.5 to 12.5
wt. %, a glass transition temperature of -25 to -65.degree. C. and
a density of 0.85 to 1.1 g/cm.sup.3.
3. Use of the rubber mixtures according to the invention and
according to claim 1 for producing shaped vulcanisates, in
particular for producing tires with reduced rolling resistance and
high resistance to wet skidding and tires with particularly
reinforced lateral walls ("run flat tires").
Description
[0001] The present patent application relates to rubber mixtures
consisting of rubber, filler and a specific sulphurised mineral
oil. Vulcanisates with surprisingly good reinforcement- and
temperature-dependent dynamic damping behaviour which are
particularly suitable for producing tires with low-damping treads
with a high resistance to wet skidding and for producing tires with
low-damping highly reinforced lateral walls can be produced from
the rubber mixtures according to the invention.
[0002] Mineral oils are often added to rubbers and rubber mixtures
to improve the processing properties. The differing content of
paraffinic, naphthenic and aromatic contents in the mineral oils is
known to have a corresponding effect on the damping properties of
the rubber vulcanisates produced, wherein, disadvantageously, it is
not possible to improve both the rolling resistance and the
resistance to wet skidding together in tires by altering the
mineral oil composition, but only one of the two properties at the
cost of the other. In this regard, see Kautschuk, Gummi,
Kunststoffe 44, 1991, page 528 to 536.
[0003] Therefore, it was an object of the present invention to
provide rubber mixtures containing a specific mineral oil which do
not have these disadvantages in the damping behaviour of the
vulcanisates.
[0004] Many methods of producing vehicle tires with low-damping
tire treads and low-damping highly reinforced lateral walls have
been investigated. U.S. Pat. No. 5,227,425 thus describes the
production of tire treads with low rolling resistance and with high
resistance to wet skidding made of solution SBR rubber, silica,
conventional aromatic mineral oil and a polysulphide-containing
silyl ether. The mineral oil certainly improves the flowability and
processibility of the rubber mixtures, but simultaneously reduces
the reinforcement level. To obtain acceptable reinforcement
properties, large quantities of an expensive
polysulphide-containing silyl ether are therefore required.
[0005] Therefore, a further object of the present invention was to
provide mineral oil-containing rubber mixtures and vulcanisates
with improved reinforcement behaviour.
[0006] JP-B 47 008 135 describes reaction products of aromatic
mineral oils with sulphur monochloride for improving the processing
behaviour of rubber mixtures. The modified mineral oils are
produced by a method which predominantly leads to mono- and
disulphide bridges due to the chemical nature of sulphur
monochloride. Moreover, the sulphur monochloride used leads to an
undesirable residue of bound chlorine in the end product.
[0007] It has now been found that rubber vulcanisates with
exceptionally favourable dynamic damping behaviour and an
exceptionally high reinforcement level can be obtained from rubber
mixtures containing certain sulphurised mineral oils and that
rubber mixtures of this type are suitable, in particular, for
producing tires which are resistant to wet skidding with
particularly low rolling resistance and for producing tires with
low damping with highly reinforced lateral walls ("run flat
tires").
[0008] The present invention therefore relates to rubber mixtures
consisting of a rubber, a fillet and optionally further rubber
auxiliaries and cross-linking agents and 0.1 to 75 parts by weight,
based on 100 parts by weight of rubber, of a specific sulphurised
mineral oil, the sulphurised mineral oil having been obtained by
reacting an aromatic-containing mineral oil with sulphur.
[0009] The sulphurised mineral oil used was produced according to
the invention in that an aromatic-containing mineral oil with an
aromatic content according to ASTM D 2140 of 5 to 50 wt. % and a
viscosity-density constant VDK of 0.82 to 1.05 was reacted with 2.5
to 40 parts by weight of sulphur per 100 parts by weight of mineral
oil at temperatures of 130 to 250.degree. C., optionally in the
presence of catalysts.
[0010] The sulphurised mineral oils according to the invention have
a bound sulphur content of 2.5 to 12.5 wt. %, preferably 4 to 10
wt. %, and a glass transition temperature (determined by DSC) of
-25 to -65.degree. C., preferably -35 to -55.degree. C., and a
density of 0.85 to 1.1 g/cm.sup.3, preferably 0.92 to 1.03
g/cm.sup.3 (at 20.degree. C.).
[0011] The viscosities are 0.3 to 100 Pa.sec, particularly
preferably 0.8 to 20 Pa.sec at 20.degree. C. (plate and cone
viscometer, 20 rpm).
[0012] The starting products for producing the sulphurised mineral
oils used according to the invention are aromatic-containing
mineral oils with an aromatic content (according to ASTM D 2140) of
5 to 50%, preferably 15 to 40%, a viscosity-density constant VDK
(according to ASTM D 2501) of 0.82 to 1.05, preferably 0.84 to 1.0.
Preferred aromatic-containing mineral oils moreover have a density
of 0.85 to 1.03 g/cm.sup.3 (at 15.degree. C.), preferably 0.9 to
1.0 g/cm.sup.3 and a pour point (according to ASTM D 97) between
-20.degree. C. and +30.degree. C., particularly preferably between
-15.degree. C. and +20.degree. C., and contain less than 0.1 wt. %,
preferably less than 0.005 wt. %, of polycyclic aromatic
hydrocarbons and/or a DMSO-extract according to IP 346<3 wt. %.
Mineral oil products of this type are commercially available;
suitable products are, for example, Enerthene.RTM. 1849-1 (BP) and
Catenex Oil SNR.RTM. (Shell). In this regard see Kautschuk, Gummi,
Kunststoffe, 45 (1992), pages 24-29.
[0013] The reaction of aromatic-containing mineral oils with
sulphur is preferably carried out with 5 to 20 parts by weight of
sulphur per 100 parts by weight of aromatic-containing mineral oils
at temperatures of preferably 160 to 220.degree. C., particularly
preferably 180 to 210.degree. C., for a time period of a few
minutes (5 min) up to several hours (10 hours), optionally in the
presence of catalysts. Suitable catalysts are acidic or basic
catalysts, such as zinc chloride, aluminium chloride, tin chloride,
hydrogen sulphide and/or alkyl amines, such as dodecylamine or
octadecylamine. Suitable quantities of catalysts are 0.01 to 3
parts by weight based on aromatic-containing mineral oil. However,
the reaction is preferably carried out without a catalyst.
[0014] Following the reaction, residues of hydrogen sulphide and
volatile mercaptans can be removed, for example, by applying a
vacuum or blowing out with nitrogen or by chemical methods, such as
oxidising agents (for example atmospheric oxygen or peroxides).
Unreacted sulphur can be removed by filtering off, for example.
[0015] In addition to natural rubbers, synthetic rubbers are also
suitable for producing the rubber mixtures and vulcanisates
according to the invention. Preferred synthetic rubbers are
described, for example, in W. Hofmann, Kautschuktechnologie,
Gentner Verlag, Stuttgart 1980 and I. Franta, Elastomers and Rubber
Coumpounding Materials, Elsevier, Amsterdam 1989. They include
inter alia
[0016] BR--polybutadiene
[0017] ABR--butadiene acrylic acid-C1-4-alkyl ester copolymers
[0018] CR--polychloroprene
[0019] IR--polyisoprene
[0020] SBR--styrene/butadiene copolymers with styrene contents of
1-60, preferably 20-50 wt. %
[0021] IIR--isobutylene isoprene copolymers
[0022] NBR--butadiene acrylonitrile copolymers with acrylonitrile
contents of 5-60, preferably 10-40 wt. %
[0023] HNBR--partially or completely hydrogenated NBR rubber
[0024] EPDM--ethylene propylene diene copolymers
[0025] and mixtures of these rubbers. Of interest for the
production of car tires, are, in particular, natural rubber,
emulsion SBR and solution SBR rubbers with a glass transition
temperature above -50.degree. C. which can optionally be modified
with silyl ethers or other functional groups according to EP-A 447
066, polybutadiene rubber with a high 1.4-cis-content (>90%)
produced by catalysts based on Ni, Co, Ti or Nd, and polybutadiene
rubber with a vinyl content of up to 75% and mixtures thereof. Most
particularly preferred are the so-called solution SBR and
polybutadiene rubbers.
[0026] The rubber mixtures according to the invention contain the
fillers known and used in the rubber industry; these include both
the active and the inactive fillers, notably:
[0027] fine-particled silicas, produced, for example, by
precipitation of solutions of silicates or flame hydrolysis of
silicon halides with specific surface areas of 5 -1000, preferably
20-400 m.sup.2/g (BET surface area) and with primary particle sizes
of 10-400 nm. The silicas can optionally be present as mixed oxides
with other metal oxides, such as Al, Mg, Ca, Ba, Zn, Zr, Ti
oxides;
[0028] synthetic silicates, such as aluminium silicate,
alkaline-earth silicate such as magnesium silicate or calcium
silicate, with BET surface areas of 20-400 m.sup.2/g and primary
particle diameters of 10-400 nm;
[0029] natural silicates such as kaolin and other naturally
occurring silicas;
[0030] glass-fibres and glass-fibre products (mats, strands) or
glass microbeads;
[0031] metal oxides, such as zinc oxide, calcium oxide, magnesium
oxide, aluminium oxide;
[0032] metal carbonates, such as magnesium carbonate, calcium
carbonate, zinc carbonate;
[0033] metal hydroxides, such as for example, aluminium hydroxide,
magnesium hydroxide;
[0034] carbon blacks. The carbon blacks to be used in this process
are produced by the lamp black, furnace or gas black process and
have BET surface areas of 20-200 m.sup.2/g, for example, SAF, ISAF,
HAF, FEF or GPF carbon blacks;
[0035] rubber gels
[0036] rubber powder, obtained, for example, by size-reduction of
rubber vulcanisates. Preferred particle sizes are between 0.001 to
0.5 mm.
[0037] Fine-particle silicas and carbon blacks, optionally together
with rubber powder, are preferably used as fillers.
[0038] The fillers mentioned can be used alone or in a mix,
specifically in quantities of 1 to 300 parts by weight, preferably
10 to 150 parts by weight based on 100 parts by weight of rubber.
In a particularly preferred embodiment, the rubber mixtures contain
as fillers, a mixture of light fillers, such as fine-particled
silicas, and carbon blacks, the mixing ratio of light filler to
carbon blacks being 1:0.05 to 20, preferably 1:0.1 to 10.
[0039] The rubber mixtures according to the invention can obviously
also contain other rubber auxiliaries and cross-linking agents.
Sulphur or sulphur-supplying compounds or peroxides are used as
cross-linking agents. Particularly preferred are sulphur or
sulphur-supplying compounds in quantities of 0.01 to 3 parts by
weight based on rubber.
[0040] Furthermore, as mentioned, the rubber mixtures according to
the invention can contain further auxiliary agents, such as the
known reaction accelerators, anti-ageing agents, heat stabilisers,
light protection agents, ozone protection agents, process aids,
reinforcing resins, for example phenolic resins, steel cord bonding
agents, such as, for example,
silica/resorcinol/hexamethylenetetramine or cobalt-naphthenate,
plasticisers, tackifiers, blowing agents, dyes, pigments, waxes,
extenders, organic acids, retarding agents, metal oxides and
activators.
[0041] The rubber auxiliaries are used in the usual, known
quantities, the quantity used depending on the subsequent intended
purpose of the rubber mixtures. For example, normal quantities of
rubber auxiliaries are in the range of 2 to 70 parts by weight,
based on 100 parts by weight of rubber.
[0042] The use of additional filler activators is particularly
advantageous for the rubber mixtures according to the invention
which are filled with highly active silicas. Preferred filler
activators are sulphur-containing silyl ethers, in particular
bis-(trialkoxysilyl-alkyl)- -polysulphides as described in DE-A 2
141 159 and DE-A 2 255 577. Further possibilities are oligomeric
and/or polymeric sulphur-containing silyl ethers according to the
description in DE-A 4 435 311 and EP-A 670 347.
Mercapto-alkyltrialkoxysilanes, in particular
mercaptopropyltriethoxysila- ne and thiocyanatoalkylsilylethers
(see DE-A 19 544 469), amino group-containing silyl ethers, such as
for example 3-amino-propyltriethoxysilane and
N-oleyl-N-propyl-trimethoxysilane and trimethylolpropane. The
filler activators are used in the usual quantities, i.e. in
quantities of 0.1 to 15 parts by weight, based on 100 parts by
weight of rubber.
[0043] The rubber mixtures according to the invention can be
produced, for example, by mixing the rubbers with the fillers,
rubber auxiliaries and the sulphurised mineral oils in suitable
mixing apparatuses, such as kneaders, rollers or extruders, or by
mixing the rubber solutions with fillers and the sulphurised
mineral oils and removing the solvent, for example by steam
distillation.
[0044] The present invention also relates to the use of the rubber
mixtures according to the invention for producing vulcanisates
which, in turn, are used for the production of highly reinforced
rubber shaped articles, in particular for the production of
tires.
[0045] Particularly preferred is the use of the rubber mixtures for
producing tire treads with low rolling resistance and resistance to
wet skidding and for producing particularly reinforced lateral
walls for tires with emergency running properties ("run flat
tires"), as described, for example, in U.S. Pat. No. 5,368,082,
EP-A 475 258, U.S. Pat. No. 5,427,166, U.S. Pat. No. 5,511,599 and
EP-A 943 466.
EXAMPLES
Example 1
Sulphurised Mineral Oil with 5.3 wt. % of Bound Sulphur
[0046] 100 g sulphur were added to 1,000 g Enerthene 1849-1
(solvent-refined mineral oil from BP, aromatics content according
to ASTM D 2140: 24%, density 0.945 g/cm.sup.3, S content 0.9%, pour
point 0.degree. C., VDK 0.884, polycyclic aromatic compound content
<50 ppm), DMSO-extract (according to IP 346): 2.2 wt.%) and
heated for 2 hours to 200.degree. C., hydrogen sulphide being
released. A vacuum was then applied for 10 minutes at 110.degree.
C. to remove the released hydrogen sulphide. 1,045 g of a black oil
were obtained with a sulphur content of 5.3 wt.%, viscosity 5
Pa.sec (plate and cone, 20 rpm, 20.degree. C.), glass transition
temperature of -50.degree. C. (according to DSC) and density
0.97g/cm.sup.3.
Example 2
Rubber Mixtures and Vulcanisates
[0047] The following rubber mixtures were produced in a 1.51
kneader. (Mixing time: 5 minutes, speed 60 rpm). The sulphur and
accelerators were finally added on a roller at 50.degree. C.:
1 Comparison Example Example 2.1 2.A 2.B Mixed in the kneader:
L-SBR Buna VSL 5025-0 (Bayer AG) 70 70 70 Polybutadiene Buna CB 25
30 30 30 (Bayer AG) Silica Vulkasil 5 70 70 70 (Bayer AG) Aromatic
mineral oil Enerthene 1849-1 (BP) 37.5 17.5 0 Sulphurised mineral
oil, 0 20 37.5 Example 1 Zinc oxide 2.5 2.5 2.5 Stearic acid 1 1 1
Antioxidant Vulkanox 4020 (Bayer AG) 1 1 1 Silane Si 69 (Degussa
Huls) 5.6 5.6 5.6 Mixed on the roller: Sulphur 1.5 1.5 1.5
Accelerator Vulkacit CZ 1.8 1.8 1.8 (Bayer AG) Accelerator Vulkacit
D 2 2 2 (Bayer AG) Mooney-Viscosity ML 1 + 4 41 43 45 (100.degree.
C.)
[0048] The mixtures were then vulcanised for 15 minutes at
170.degree. C. The following vulcanisate properties were found:
2 Comparison Example Example 2.1 2.A 2.B Tensile modulus 100% 2.2
2.8 3.3 elongation (MPa) Tensile modulus 300% 8.4 10.8 12.5
elongation (MPa) Tensile strength (MPa) 15.7 16.1 17 Rebound at
23.degree. C. (%) 34 33 32 Rebound at 70.degree. C. (%) 53 59 60
Shore A hardness (23.degree. C.) 60 63 66 Abrasion DIN 53.516
(mm.sup.3) 109 92 93
[0049] The test results show that vulcanisates with improved
dynamic damping properties (low rebound at 23.degree. C. correlated
with high resistance to wet skidding in tires, high rebound at
70.degree. C. correlated with low rolling resistance in tires) and
low abrasion at a significantly higher reinforcement level can be
produced from the rubber mixtures with the content according to the
invention of sulphurised mineral oils (I).
* * * * *