Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-14
2002-08-13
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S261000, C524S394000, C524S442000, C524S493000, C524S495000, C524S496000, C524S430000, C524S432000
Reexamination Certificate
active
06433064
ABSTRACT:
INTRODUCTION AND BACKGROUND
The present invention relates to rubber powders which also contain, in addition to the rubber components, further constituents important for the production of the vulcanizable rubber mixture. Thus, the invention relates to rubber powder compositions, products made therefrom and process for obtaining said compositions.
If, in addition to the constituents of the basic batch, the rubber powder also contains crosslinking chemicals (accelerator, sulfur), it is known as a full compound. If the rubber powder in particular consists of the constituents of the basic batch, it is known as a “semi-compound.” Intermediate forms between these stages are also suitable. These terms are known in the art.
Numerous documents have been published relating to the aim and purpose of using rubber powders (powdered rubbers) and relating to processes for the production thereof.
The interest in pulverulent rubbers is explained by the processing methods used in the rubber industry, where rubber mixtures are produced with a considerable input of time, energy and labor. The main reason for this is that the raw material, crude rubber, is in the form of bales.
The bale is comminuted and intimately mixed during the course of several processing stages with fillers, mineral oil plasticizers and vulcanization auxiliaries in roll mills or internal mixers. The mixture is generally stored between the stages. Extruder/pelletizers or extruder/roller dies are generally arranged downstream from the internal mixers or roll mills. The only way forward from this highly complex method of rubber processing is to develop an entirely new processing technology. The use of free-flowing rubber powders has thus been discussed for some time as this approach makes it possible to process rubbers mixtures simply and rapidly in the same way as powdered thermoplastics.
German Patent 2822 148 discloses a process for the production of a pulverulent rubber containing filler.
According to this German patent, an aqueous filler emulsion is added to a rubber latex, rubber solution or the aqueous emulsion of a rubber and the desired rubber powder is precipitated. In order to avoid the particle size dependent filler contents obtained from this process, variants of this process have been filed under German patents 3723 213 and 3723 214 and are part of the prior art. According to German patent 3723 213, in a two-stage process, a quantity of ≦50% of the filler is initially incorporated into the particles of rubber powder. In the second stage, the remainder of the filler is applied onto the so-called basic rubber particle. This may be considered a variant of dusting, as no bond is created between the filler and rubber.
However, as E. T. Italiaander has pointed out (presentation 151, technical conference of the Rubber Division of the ACS, Anaheim, Calif., May, 6-9, 1997 (GAK 6/1997 (50) 456-464)), despite the bright future predicted in the Delphi Report (Delphi Report, “Künftige Herstellverfahren in der Gummiindustrie”, Rubber Journal, volume 154, no. 11, 20-34 (1972)) for pulverulent and pelletized rubbers and numerous attempts made by well-known polymer manufacturers from the mid 1970's until the early 1980's to produce pulverulent NBR, SBR/carbon black masterbatches and pelletized NR, the rubber bale remains the standard form in which polymers are supplied.
One disadvantage of known processes is firstly that a grinding operation is necessary in order to achieve a particle diameter of the filler particles of 10 (m, which is considered essential to the quality of the final product.
However, this requires not only elevated energy input but also results in damage to the filler structure which, together with the active surface area, is a significant parameter for its efficacy in rubber applications.
Secondly, the handling properties of prior art products suffer in that the particles stick together during storage.
It is accordingly, an object of the invention is to provide a pulverulent, free-flowing rubber containing filler which is easily processed, together with a process for the production thereof.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved by a finely divided, free-flowing rubber powder composition, which
a) contains a rubber matrix and additionally
b) one or more white and/or black fillers known from the rubber industry optionally modified with one or more of the organosilicon compounds of the formulae (I), (II) or (III) as hereinafter described,
c) one of more of the additives known for the production of rubber vulcanizates.
All or part of the filler may be used in premodified form or may have been modified during the present process.
Depending upon the extent of processing (nature of the added mixture components), the product may be designated a semi-compound or full compound.
The rubber powder in particular contains the organosilicon compounds in a form which has reacted with the filler if a silicate filler, in particular a precipitated silica, is used.
The particle size range of the rubber powders according to the invention is generally between 0.05 and 10 mm, in particular between 0.5 and 2 mm.
The rubber powders according to the invention exhibit a narrower size distribution which is shifted towards smaller particle sizes than is known from the prior art (Kautschuk+Gummi+Kunststoffe 7, 28 (1975) 397-402). This fact facilitates processing of the powders. Moreover, due to the production process, the filler content of the individual particles is not determined by particle size. The pulverulent rubbers contain from 20 to 250 phr, in particular from 50 to 100 phr (phr: parts per hundred parts of rubber), of filler, part or all of which has optionally been surface modified before the process according to the invention using the organosilicon compounds herein described of the formulae (I), (II) or (III) known in the rubber industry. The following, individually or as mixtures, have proved to be suitable types of rubber: natural rubber, emulsion SBR having a styrene fraction of 10 to 50%, butyl/acrylonitrile rubber, butyl rubbers, terpolymers prepared from ethylene, propylene (EPM) and unconjugated dienes (EPDM), butadiene rubbers, SBR, produced using the solution polymerization process, having styrene contents of 10 to 25%, as well as 1,2-vinyl constituent contents of 20 to 55% and isoprene rubbers, in particular 3,4-polyisoprene.
In addition to the stated rubbers, the following elastomers may be considered, individually or as mixtures: carboxyl rubbers, epoxy rubbers, trans-polypentenamer, halogenated butyl rubbers, rubbers prepared from 2-chlorobutadiene, ethylene/vinyl acetate copolymers, epichlorohydrins, optionally also chemically modified natural rubber, such as for example epoxidized grades. Fillers which are generally used are the carbon blacks known from rubber processing and white fillers of a synthetic nature, such as for example precipitated silicas or natural fillers, such as for example siliceous chalk, clays etc. are additionally used.
Carbon blacks, as are generally used in rubber processing, are particularly suitable.
Such carbon blacks include furnace blacks, gas blacks and lamp backs having an iodine absorption value of 5 to 1000 m
2
/g, a CTAB value of 15 to 600 m
2
/g, a DBP adsorption of 30 to 400 ml/100 g and a 24 M4 DBP value of 50 to 370 ml/100 g in a quantity of 5 to 250 parts, in particular of 20 to 150 parts, per 100 parts of rubber, in particular of 40 to 100 parts.
Silicate fillers of synthetic or natural origin known from the rubber sector, in particular precipitated silicas, are also suitable.
These generally have an N
2
surface area, determined using the known BET method, of 35 to 700 m
2
/g, a CTAB surface area of 30 to 500 m
2
/g, a DBP value of 150 to 400 ml/100 g. The product according to the invention contains these silicas in a quantity of 5 to 250 parts, in particular of 20 to 100 parts, relative to 100 parts of rubber. If the fillers comprise white natural fillers, such as clays or siliceous chalks having an N
2
Ernst Uwe
Görl Udo
Lauer Hartmut
Stober Reinhard
Cain Edward J.
PKU Pulverkautschuk Union GmbH
Smith , Gambrell & Russell, LLP
LandOfFree
Rubber powder compositions and process for the production... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rubber powder compositions and process for the production..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber powder compositions and process for the production... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2899801