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
2000-06-20
2002-06-04
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S192000, C525S194000, C525S195000, C525S208000, C525S213000, C525S221000, C525S232000, C525S233000, C525S235000, C525S236000, C525S237000, C525S238000, C525S240000, C525S241000
Reexamination Certificate
active
06399706
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the addition of sulfur-containing organosilicon compounds to microgel-containing rubber compounds and to vulcanized materials which are produced therefrom. The addition of sulfur-containing organosilicon compounds to microgel-containing rubber compounds results in an improvement in mechanical properties and in an improvement of the relationship between the rolling resistance and the resistance to wet slip of tread compounds.
BACKGROUND OF THE INVENTION
The production and use of sulfur-containing organosilicon compounds is described in following patents and patent applications, amongst others: DE 2,141,159, U.S. Pat. No. 3,873,489, U.S. Pat. No. 5,110,969, U.S. Pat. No. 4,709,065 and U.S. Pat. No. 5,227,425, which demonstrate the positive effect of sulfur-containing organosilicon compounds on the mechanical properties of silica-filled vulcanized materials. These publications, however, do not teach the use of sulfur-containing organosilicon compounds for improving the level of mechanical properties of microgel-containing rubber compounds without impairing the hysteresis properties thereof.
The use of microgels in rubber compounds is described in the following patent applications or patents: EP 405 216, DE 4,220,563, GB 1,078,400 and DE 19 701 489. In EP 405,216, DE 4,220,563, and in GB 1,078,400, the use is claimed of CR, BR and NBR microgels for compounds comprising rubbers which contain double bonds and for the production of the corresponding vulcanized materials. These vulcanized materials are particularly suitable for the production of tire treads, since at 70° C. they exhibit a high rebound resilience and thus, exhibit a low rolling resistance, and at 23° C. they exhibit low rebound resilience and thus, exhibit a high resistance to wet slip. In particular, the difference between the rebound resiliences at 70° C. and 23° C. is characteristic of microgel-containing vulcanized materials. However, the mechanical properties of microgel-containing vulcanized materials are not satisfactory for commercial use in tire treads. In particular, deficiencies exist in the level of mechanical properties of these vulcanized materials. There is a need here to improve the product of the tensile stress at 300 % strain and the elongation at break, as well as the abrasion-resistance.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention was to improve the level of mechanical properties (tensile stress/300%×elongation at break) as well as the abrasion-resistance of microgel-containing vulcanized rubber materials, without adversely affecting the difference between the rebound resiliences at 70° C. and 23° C.
It has now been found that the level of mechanical properties (tensile stress/300%×elongation at break) of microgel-containing vulcanized rubber materials can be improved, without adversely affecting the difference between the rebound resiliences at 70° C and 23° C., by the addition of sulfur-containing organosilicon compounds to microgel-containing rubber compounds.
DETAILED DESCRIPTION OF THE INVENTION
Therefore, the present invention relates to rubber compounds which comprise at least one rubber (A) which contains double bonds, at least one rubber gel (B), and at least one sulfur-containing organosilicon compound (C), wherein the proportion of rubber (A) which contains double bonds is 100 parts by weight, the proportion of rubber gel (B) is 1 to 150 parts by weight and the proportion of sulfur-containing organosilicon compound (C) is 0.2 to 20 parts by weight, preferably 1 to 10 parts by weight and which also, optionally, comprise rubber adjuvant substances and optionally comprise other fillers.
A rubber (A) which contains double bonds is to be understood to comprise rubbers which have practically no gel content and which are denoted as R rubbers according to DIN/ISO 1629. These rubbers have a double bond in their main chain. Examples thereof include:
NR: natural rubber
SBR: styrene/butadiene rubber
BR: polybutadiene rubber
NBR: nitrile rubber
IIR: butyl rubber
HNBR: hydrogenated nitrile rubber
SNBR:styrene/butadiene/acrylonitrile rubber
CR: polychloroprene
XSBR:carboxylated styrene/butadiene rubber
XNBR: carboxylated butadiene/acrylonitrile rubber
ENR: epoxidized natural rubber.
ESBR: epoxidized styrene/butadiene rubber.
Rubbers which contain double bonds are also to be understood, however, as rubbers which are M rubbers according to DIN/ISO 1629 and which apart from their saturated main chain contain double bonds in side chains. These rubbers include EPDM for example.
NR, BR, SBR, IIR and EPDM are preferred.
Rubber gels (B) are to be understood as rubber particles (microgels) which are obtained by crosslinking the following rubbers:
BR: polybutadiene,
ABR: copolymers of butadiene/acrylic acid C
1-4
alkyl esters,
IR: polyisoprene,
SBR: styrene-butadiene copolymers with styrene contents of 1-60, preferably 2-50 percent by weight,
X-SBR: carboxylated styrene-butadiene copolymers
FKM: fluorinated rubber,
ACM: acrylate rubber,
NBR: polybutadiene-acrylonitrile copolymers with acrylonitrile contents of 5-60, preferably 10-50 percent by weight,
X-NB R: carboxylated nitrile rubbers,
CR: polychloroprene,
IIR: isobutylene/isoprene copolymers with isoprene contents of 0.5-10 percent by weight,
BIIR: brominated isobutylene/isoprene copolymers with bromine contents of 0.1-10 percent by weight,
CIIR: chlorinated isobutylene/isoprene copolymers with chlorine contents of 0.1-10 percent by weight,
HNBR: partially and completely hydrogenated nitrile rubbers,
EPDM: ethylene-propylene-diene copolymers,
EAM: ethylene/acrylate copolymers
EVM: ethylene/vinyl acetate copolymers,
ECO: epichlorohydrin rubbers,
Q: silicone rubbers,
AU: polyester urethane polymers,
EU: polyether urethane polymers,
ENR: epoxidized natural rubber or mixtures thereof.
Gels based on NR, BR, SBR, CR and NBR are preferred.
Rubber gels (B) can also, of course, contain hydroxyl and/or carboxyl groups. Rubber gels, which contain hydroxyl groups, are preferably used in the rubber compounds according to the present invention.
The microgels have particle diameters of 5-1000 nm, preferably 20-600 nm (DVN value according to DIN 53206). Because they are crosslinked, they are insoluble, and can be swollen in suitable swelling agents such as toluene. The swelling indices of the microgels (Q) in toluene range from 1-15, preferably from 1-10. 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: Q
i
=moist weight of gel/dry weight of gel.
To determine the swelling index, 250 mg gel are allowed to swell in 25 ml toluene for 24 hours with shaking. The gel is centrifuged off and weighed, and is subsequently dried to constant weight at 70° C. and weighed again.
The uncrosslinked rubber starting materials can be produced in the known manner by emulsion polymerization or by solution polymerization.
Naturally occurring latices such as natural rubber latex can also be used.
The following monomers, which can be polymerized by a radical mechanism, are used for the production of microgels by emulsion polymerization: butadiene, styrene, acrylonitrile, isoprene, esters of acrylic and methacrylic acid, tetrafluoroethylene, vinylidene fluoride, hexafluoropropene, 2-chlorobutadiene and 2,3-dichlorobutadiene, as well as carboxylic acids which contain double bonds, such as acrylic acid, methacrylic acid, maleic acid and itaconic acid for example, hydroxy compounds which contain double bonds, such as hydroxyethyl methacrylate, hydroxyethyl acrylate and hydroxybutyl methacrylate, or epoxides which contain double bonds, such as glycidyl methacrylate or glycidyl acrylate for example. Crosslinking of the rubber gels can be effected directly during emulsion polymerization, by copolymerization with multi-functional compounds which have a crosslinking effect. The preferred multi-functional comonomers are compounds which comprise least two, preferably 2 to 4 copolymerizable C═C double bonds, such
Jeske Winfried
Obrecht Werner
Bayer Aktiengesellschaft
Cheung Noland J.
Gil Joseph C.
Nutter Nathan M.
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