Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-08-14
2003-11-18
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S126000
Reexamination Certificate
active
06649696
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to rubber mixtures based on uncrosslinked rubbers and crosslinked rubber particles (so-called rubber gels) and to multifunctional isocyanates based on polyuret. The rubber mixtures according to the present invention are suitable for producing rubber vulcanizates, which exhibit an advantageous combination of mechanical properties, such as modulus at 300% elongation, elongation at break, tear strength and abrasion resistance. The vulcanizates produced from the rubber mixtures according to the present invention also have a lower density and this has a positive effect on the weight of the rubber molded articles produced from the vulcanizates, in particular tires or tire parts.
BACKGROUND OF THE INVENTION
It is known that rubber mixtures composed of uncrosslinked rubbers and crosslinked rubber particles (rubber gels) as fillers produce vulcanizates which have low rebound resilience at ambient temperature (good skid resistance in the wet) and high rebound resilience at 70° C. (low rolling resistance) during vulcanization with conventional vulcanizing agents (for example sulfur vulcanization).
Reference is made by way of example in this context to U.S. Pat. No. 5,124,408, U.S. Pat. No. 5,395,891, DE-A 197 01 488, DE-A 197 01 487, DE-A 199 29 347, DE-A 199 39 865, DE-A 199 42 620.
The reinforcing effect of the microgels in vulcanizates (modulus at 300% elongation —S
300
-, elongation at break —D-, tear strength and abrasion) can be improved for industrial use. This is demonstrated, in particular, by the fact that large quantities of gel must be used to adjust industrially relevant S
300
values.
Overfilling of the mixtures results from these large quantities of gel and consequently the tear strengths and the elongations at break of the vulcanizates decrease. The object is therefore to find measures to increase the modulus of lowfilled gel-containing rubber vulcanizates. The object is also to reduce the DIN abrasion.
It is also known to vulcanize natural rubber with carbon black as filler with diisocyanates. The vulcanizates obtained in this way do not, however, have satisfactory mechanical properties. In addition, the vulcanizates adhere very strongly to the metal parts of the vulcanizing molds used (O. Bayer, Angewandte Chemie, edition A, year 59, No. 9, p. 257-288, September 1947).
SUMMARY OF THE INVENTION
According to the present invention, rubber mixtures will now be provided which allow production of vulcanizates with improved mechanical properties (product of modulus at 300% elongation and elongation at break) and a lower vulcanizate density, and this is desirable, for example, in tires or individual tire components.
The present invention, therefore, provides rubber mixtures containing uncrosslinked, double bond-containing rubbers (A), crosslinked rubber particles (B) and multifunctional isocyanates based on biuret (C), wherein, based on 100 parts by weight (phr) of the rubber components (A) respectively, the component (B) content in the mixture is 1 to 150 parts by weight and the multifunctional isocyanate content based on biuret (component C) is 1 to 100 parts by weight.
DETAILED DESCRIPTION OF THE INVENTION
Preferred rubber mixtures according to the present invention are those which, based on 100 parts by weight of the rubber component (A) respectively, have 5 to 100 parts by weight of crosslinked rubber particles (component B) and 3 to 50 parts by weight of multifunctional isocyanates based on biuret (component C).
Double bond-containing rubbers are taken to mean those rubbers which are designated R-rubbers in accordance with DIN/ISO 1629. These rubbers have a double bond in the main chain. They include, for example:
NR:
natural rubber
SBR:
styrene/butadiene rubber
BR:
polybutadiene rubber
NBR:
nitrile butadiene rubber
IIR:
butyl rubber
BIIR:
brominated isobutylene/isoprene copolymers with bromine
contents of 0.1 to 10 percent by weight
CIIR:
chlorinated isobutylene/isoprene copolymers with bromine
contents of 0.1 to 10 percent by weight
HNBR:
hydrogenated or partially hydrogenated nitrile butadiene rubber
SNBR:
styrene/butadiene/acrylonitrile rubber
CR:
polychloroprene
ENR:
epoxidized natural rubber or mixtures thereof
X-NBR:
carboxylated nitrile butadiene rubbers
X-SBR:
carboxylated styrene butadiene copolymers.
Double bond-containing rubbers should also, however, be taken to mean those rubbers which are called M-rubbers in accordance with DIN/ISO 1629 and, in addition to the saturated main chain, have double bonds in the side chain. These include, for example, EPDM.
The double bond-containing rubbers of the above-mentioned type to be used in the rubber mixtures according to the present invention can, of course, be modified by functional groups which can react with the functional isocyanates based on polyuret to be used and, as will be described below, can improve a coupling of the crosslinked rubber particles to the surrounding rubber matrix in the vulcanized state.
Uncrosslinked rubbers which are functionalized by hydroxyl, carboxyl, amino and/or amide groups are particularly preferred. The functional groups can be introduced directly during polymerization, by copolymerization with suitable comonomers, or after polymerization, by polymer modification.
The introduction of such functional groups by polymer modification is known and described for example in M. L. Hallensleben “Chemisch modifizierte Polymere” in Houben-Weyl Methoden der Organischen Chemie, 4th Edition, “Makromolekulare Stoffe”, part 1 to 3; Georg Thieme Verlag Stuttgart, New York, 1987; pages 1994 to 2042, DE-A 2 653 144, EP-A 464 478, EP-A 806 452 and German Patent Application No. 198 32 459.6.
The quantity of functional groups in the rubbers is conventionally 0.05 to 25 wt. %, preferably 0.1 to 10 wt. %.
Crosslinked rubber particles known as rubber gels, in particular those obtained by appropriate crosslinking of the following rubbers:
BR:
polybutadiene,
ABR:
butadiene/acrylic acid-C1-4 alkyl ester copolymers,
IR:
polyisoprene,
SBR:
styrene butadiene copolymers with styrene contents of 1 to
60, preferably 5 to 50 percent by weight,
X-SBR:
carboxylated styrene butadiene copolymers,
FKM:
fluorinated rubber,
ACM:
acrylate butadiene rubber,
NBR:
polybutadiene acrylonitrile copolymers with acrylonitrile
contents of 5 to 60, preferably 10 to 50 percent by weight,
X-NBR:
carboxylated nitrile butadiene rubbers,
CR:
polychloroprene,
IIR:
isobutylene/isoprene copolymers with isoprene contents of
0.5 to 10 percent by weight,
BIIR:
brominated isobutylene/isoprene copolymers with bromine
contents of 0.1 to 10 weight percent,
CIIR:
chlorinated isobutylene/isoprene copolymers with bromine
contents of 0.1 to 10 weight percent,
HNBR:
partially and fully hydrogenated nitrile butadiene rubbers,
EPDM:
ethylene propylene diene copolymers,
EAM:
ethylene/acrylate copolymers,
EVM:
ethylene/vinyl acetate copolymers,
CO & ECO:
epichlorohydrin rubbers,
Q:
silicone rubbers,
AU:
polyester urethane polymers,
EU:
polyurethane polymers
are used in the mixtures according to the present invention as crosslinked rubber particles.
The rubber particles to be used according to the present invention conventionally have particle diameters of 5 to 1,000 nm, preferably 10 to 600 nm (diameters to DIN 53 206). They are insoluble owing to crosslinking and may be swollen in solvents, for example toluene. The swelling indices of the rubber particles (Q
i
) in toluene are approximately 1 to 15, preferably 1 to 10. The swelling index is calculated from the weight of the solvent-containing gel (after centrifugation at 20,000 rpm) and the weight of the dry gel, wherein Q
i
=wet weight of the gel/dry weight of the gel. The gel content of the rubber particles according to the present invention is conventionally 80 to 100 wt. %, preferably 90 to 100 wt. %.
Production of the crosslinked rubber particles (rubber gels) to be used from the basic rubbers of the above-mentioned type, is known in principle and described, for example, in U.S. Pat. No. 5 395 891 and EP-A 98 100 049.0.
In addition it is possi
Mezger Martin
Obrecht Werner
Sumner Anthony
Bayer Aktiengesellschaft
Cheung Noland J.
Gil Joseph C.
Seng Jennifer R.
Short Patricia A.
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