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
2001-10-16
2004-05-18
Buttner, David J. (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...
C525S137000, C525S139000, C525S141000, C525S154000, C525S155000, C524S089000, C524S091000, C524S110000, C524S323000, C524S343000, C524S346000, C524S352000, C524S353000
Reexamination Certificate
active
06737478
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns rubber compounds which, in addition to the conventional compound components, contain crosslinked rubber particles (known as rubber gels), phenolic resin adducts or phenol/aldehyde condensation products and which are characterized in the uncrosslinked state by good processability (compound viscosity—ML 1+4/100° C.≦60 ME) and in the vulcanized state by Shore-A hardness values/23° C.≧60, moduli at 100% elongation (S
100
)≧3.0 Mpa and by high impact resilience values at 70° C. (E70° C.>60%). Moreover, the vulcanizates produced from the rubber compounds according to the present invention have a low density, which has an advantageous effect on the weight of molded rubber articles manufactured from the vulcanizates, particularly in the case of tires or tire components.
BACKGROUND OF THE INVENTION
It is known that rubber compounds consisting of uncrosslinked rubbers and crosslinked rubber particles (rubber gels) display a low specific weight and low compound viscosities and when vulcanized with conventional vulcanizing agents (e.g. sulfur vulcanization) produce vulcanizates that demonstrate good impact resilience values at 70° C. and therefore, low damping under operating conditions.
Reference is made in this connection by way of example to U.S. Pat. No. 5,124,408, U.S. Pat. No. 5,395,891, DE-A 197 01 488.7, DE-A 197 01 487.9, DE-A 199 29 347.3, DE-A 199 39 865.8, DE-A 199 42 620.1 and DE-A 19701487.1.
The mechanical properties of gel-containing rubber vulcanizates are not adequate for industrial use, particularly by reason of a poor reinforcing effect on the part of the microgels. The modulus at 100% elongation (S
100
), the elongation at break (D) and the tear strength (F) need to be improved.
These improvements need to be made without impairing the advantageous compound viscosities in the unvulcanized rubber compounds.
The use of phenolic resin adducts such as resorcinol and formaldehyde donors such as hexamethylene tetramine for the production of so-called adhesive compounds is known. With the aid of these adhesive systems, the rubber compound can be bonded to reinforcing materials such as metal cord, glass fabric, polyamide or polyester fabrics (Kautschukhandbuch für die Gummuiindustrie, Bayer AG, 1991, p. 499-531). However, the use of phenolic resin adducts and of condensed phenolic resins to improve the mechanical properties (modulus, elongation at break, tear strength) without impairing the processability (compound viscosity) of rubber compounds containing rubber gels is not taught in the published literature.
SUMMARY OF THE INVENTION
Therefore, there was a technical need to find measures to increase the level of mechanical values in gel-containing rubber vulcanizates, particularly the product of modulus at 100% elongation and elongation at break (S
100
×D), whereby the compound viscosity of the unvulcanized compounds and the tear strength of the vulcanizates should not be impaired by these measures.
DETAILED DESCRIPTION OF THE INVENTION
The present invention, therefore, provides rubber compounds containing uncrosslinked, double bond-containing rubbers (A), crosslinked rubber particles (B) and phenolic resin adducts or condensed phenolic resins (C), whereby the double bond-containing rubbers (A) are present in quantities of 100 parts by weight, the crosslinked rubber particles (B) in quantities of 10 to 150 parts by weight, preferably 20 to 120 parts by weight, and the quantity of phenolic resin adducts or condensed phenolic resins (C) in quantities of 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight.
The rubbers according to the present invention can naturally also contain additional fillers and rubber auxiliary substances that are known.
Component (A) of the rubber compounds according to the present invention contains double bond-containing rubbers designated as R rubbers according to DIN/ISO 1629. These rubbers have a double bond in the main chain. They include, for example:
NR:
Natural rubber
IR:
Polyisoprene
SBR:
Styrene-butadiene rubber
BR:
Polybutadiene rubber
NBR:
Nitrile rubber
IIR:
Butyl rubber
BIIR:
Brominated isobutylene-isoprene copolymers with bromine
contents of 0.1 to 10 wt. %
CIIR:
Chlorinated isobutylene-isoprene copolymers with chlorine
contents of 0.1 to 10 wt. %
HNBR:
Hydrogenated or partially hydrogenated nitrile rubber
SNBR:
Styrene-butadiene-acrylonitrile rubber
SIBR:
Styrene-isoprene-butadiene rubber
CR:
Polychloroprene
ENR:
Epoxidized natural rubber or mixtures thereof
X-NBR:
Carboxylated nitrile rubbers
X-SBR:
Carboxylated styrene-butadiene copolymers.
Double bond-containing rubbers should also, however, be understood to include rubbers, which are designated as M rubbers according to DIN/ISO 1629 and contain double bonds in the side chain in addition to the saturated main chain. These include EPDM, for example.
The double bond-containing rubbers of the above-mentioned type for use in the rubber compounds according to the present invention can naturally be modified by functional groups that react with phenolic resin adducts or with precondensed phenolic resin adducts and—as is described below—are capable of improving the coupling of the crosslinked rubber particles to the surrounding rubber matrix in the vulcanized state.
In particular, uncrosslinked rubbers that are functionalized by hydroxyl, carboxyl, amino, amido and/or epoxy groups are more preferred. Functional groups can be introduced directly during polymerization by means of copolymerization with suitable comonomers or after polymerization by means of 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, 4
th
edition, “Makromolekulare Stoffe” part 1-3; Georg Thieme Verlag Stuttgart, New York, 1987, p. 1994-2042; DE-A 2 653 144, EP-A 464 478, EPA 806 452 and German patent application DE 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. %.
Component (B) of the rubber compounds according to the present invention comprises crosslinked rubber particles known as rubber gels or microgels, which can be obtained by appropriate crosslinking of the following rubbers:
BR:
Polybutadiene
ABR:
Butadiene-C
1-4
alkyl acrylate copolymers
IR:
Polyisoprene
SBR:
Styrene-butadiene copolymers with styrene contents of 1-60,
preferably 5-50 wt. %
X-SBR:
Carboxylated styrene-butadiene copolymers
FKM:
Fluororubber
ACM:
Acrylate rubber
NBR:
Polybutadiene-acrylonitrile copolymers with acrylonitrile
contents of 5-60, preferably 10-50 wt. %
X-NBR:
Carboxylated nitrile rubbers
ENR:
Epoxidized natural rubber
CR:
Polychloroprene
IIR:
Isobutylene-isoprene copolymers with isoprene contents of
0.5-10 wt. %
BIIR:
Brominated isobutylene-isoprene copolymers with bromine
contents of 0.1 to 10 wt. %
CIIR:
Chlorinated isobutylene-isoprene copolymers with chlorine
contents of 0.1 to 10 wt. %
HNBR:
Partially and fully hydrogenated nitrile rubbers
EPM:
Ethylene-propylene copolymers
EPDM:
Ethylene-propylene-diene terpolymers
EAM:
Ethylene-acrylate copolymers
EVM:
Ethylene-vinyl acetate copolymers
CO and
Epichlorohydrin rubbers
ECO:
Q:
Silicone rubbers
AU:
Polyester urethane polymers
EU:
Polyether urethane polymers.
The rubber particles for use according to the present invention conventionally have particle diameters from 5 to 1000 nm, preferably 10 to 600 nm (diameters stated according to DIN 53 206).
Their crosslinking makes them (almost) insoluble and in suitable precipitants, e.g. toluene, swellable. The (insoluble) gel content of the rubber particles is conventionally 80 to 100 wt. %, preferably 90 to 100 wt. %. The swelling index of the rubber particles (Q
i
) in toluene is approx. 1 to 15, preferably 1 to 10.
The swelling index Qi is defined as:
Qi
=
Wet
weight
of
the
toluene
-
containing
gel
Dry
Obrecht Werner
Sumner Anthony
Bayer Aktiengesellschaft
Buttner David J.
Cheung Noland J.
Gil Joseph C.
Seng Jennifer R.
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