Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-07-07
2001-06-12
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S100000, C525S104000, C525S105000, C525S106000, C525S342000, C528S025000, C528S026000, C528S028000, C528S033000, C528S034000
Reexamination Certificate
active
06245834
ABSTRACT:
The area of the present invention is that of the use of a specific combination of silicone compounds as silica/elastomer coupling agent in natural or synthetic elastomer compositions comprising a siliceous material as reinforcing filler. The invention also relates to the elastomer compositions obtained by virtue of the employment of an effective amount of the said combination of silicone compounds and to the processes for the preparation of these compositions. It also relates to the articles made of elastomer(s) with a body comprising the abovementioned compositions.
The types of articles made of elastomer(s) where the invention is most useful are those subject in particular to the following stresses: high frequency loading variations and/or temperature variations under dynamic conditions; and/or a high static stress; and/or a high flexural fatigue under dynamic conditions. Types of articles are, for example: conveyor belts, power transmission belts, flexible pipes, expansion joints, seals for domestic electrical appliances, supports which act to remove engine vibrations, either with metal frameworks or with a hydraulic fluid within the elastomer, spring components situated between the rigid articulated metal components of the caterpillar track of a vehicle in contact with the ground, cables, cable sheathings, shoe soles and rollers for cableways.
The area of the invention is that of a high-performance use capable of providing elastomer compositions which in particular exhibit, in order to meet the stresses of use spoken about above, an exothermicity under dynamic conditions (tan) which is as low as possible and, if possible, excellent mechanical properties, in particular good tear strength, resistance to abrasion and compression set (CS) values. Other properties which can be improved are, for example, the properties of resistance to water and to water containing washing powder of the vulcanisates resulting from certain elastomers.
To achieve such an objective, many solutions have been provided consisting in particular in modifying, inter alia, the nature of the elastomers on completion of polymerization by means of coupling or starring or functionalization agents.
All these solutions have essentially concentrated on the use of modified polymers with carbon black as reinforcing filler with the aim of obtaining a good interaction between the modified polymer and the carbon black. It is known, generally, that in order to obtain the optimum reinforcing properties conferred by a filler, it is advisable for the latter to be present in the elastomer matrix in a final form which is both as finely divided as possible and as homogeneously distributed as possible. Now, such conditions can only be produced insofar as, on the one hand, the filler exhibits a very good ability to be incorporated in the matrix during the mixing with the elastomer and to disaggregate or to deagglomerate and to disperse homogeneously in the elastomer. The use of white reinforcing fillers, and in particular of silica, has proved to be inappropriate due to the low level of certain properties of such compositions and consequently of certain properties of the articles in which these compositions are used.
Moreover, because of mutual affinity, the silica particles have an unfortunate tendency to agglomerate with one another in the elastomer matrix. These silica/silica interactions have the harmful consequence of limiting the reinforcing properties to a level substantially lower than that which it would be theoretically possible to reach if all the silica/elastomer interactions capable of being created during the mixing operation were actually obtained.
Moreover, the use of silica raises difficulties of use due to the silica/silica interactions, which tend, in the crude state, to increase the consistency of the elastomer compositions and in any case to make their use more difficult than the use of carbon black. Finally, the interactions between the silica and the crosslinking system, when it is based on sulphur, are disadvantageous to the rate and the yield of the crosslinking.
It is known to the person skilled in the art that it is necessary to use a coupling or binding agent which reacts with the silica in order to create good interactions between the surface of the silica and the elastomer and a true network between the elastomer chains, while facilitating the dispersion of the silica.
Thus, Patent U.S. Pat. No. 3,350,345 provides for the use of rubber compositions comprising silica, a hydrolysable silane and, in particular, a mercaptosilane as elastomer/silica coupling agent. Patent Application FR-A-2,094,859 provides for the use of rubber compositions comprising silica and a mercaptosilane as coupling agent for the manufacture of tire treads, due to the improved properties exhibited by such compositions. It was rapidly demonstrated and known by the person skilled in the art that mercaptosilanes, and in particular &ggr;-mercaptopropyltrimethoxysilane and &ggr;-mercaptopropyltriethoxysilane, were capable of providing the best silica/elastomer coupling properties but that the industrial use of these coupling agents often posed a problem, due to the high reactivity of the SH functional groups resulting very rapidly, during the composition preparation in an internal mixer, in premature vulcanizations, also known as “scorch”, in very high Mooney plasticities and finally in compositions which are virtually impossible to work and to make use of industrially. For illustration of this difficulty in the industrial use of such coupling agents and the compositions containing them, mention may be made of Patent Application FR-A-2,206,330 and Patent U.S. Pat. No. 4,002,594.
To overcome this disadvantage, Patent Application FR-A-2,206,330 provides for the use, as coupling agent, of polysulphide organosilanes, including bis(3-triethoxysilylpropyl) tetrasulphide, which prove to result in the best compromise, for vulcanisates containing silica as filler, in terms of scorch safety, ease of use and reinforcing power. However, this coupling agent is very expensive and must be used in a relatively large amount, of the order of 2 to 3 times larger than the amount of &ggr;-mercaptopropyltrimethoxysilane necessary to obtain equivalent levels of coupling properties.
Consequently, it thus appears desirable from an economic viewpoint to be able industrially to develop silica-reinforced elastomer compositions comprising low levels of coupling agents which have as good a performance as mercaptosilanes but while avoiding premature vulcanizations and problems of use related to an excessively high viscosity of the compositions.
An attempt in this direction has been described in Patent U.S. Pat. No. 4,74,908, which discloses the use, as coupling agents, of the mixture of a mercaptosilane and an alkoxysilane. However, this route does not satisfactorily overcome the problem of scorch and of use.
On considering the prior state of the art, it thus appears that there exists an unfulfilled requirement, in high-performance uses, for coupling agents based on silicone compounds in elastomer compositions comprising a siliceous material as reinforcing filler.
I—This object, among others, is achieved by the present invention, which relates more specifically, in a first subject, to the use:
→ of an effective amount of a specific combination of silicone compounds comprising the combination:
of at least one functionalized polyorganosiloxane (abbreviated as POS) containing, per molecule, at least one functional siloxy unit (abbreviated as UN1) capable of binding chemically and/or physically with the hydroxylated surface sites of the silica particles,
and of at least one functionalized organosilane (abbreviated as OS) containing, per molecule, at least one functional group (abbreviated as G1) capable of binding chemically and/or physically with the UN1 units and/or the hydroxylated sites of the silica particles and at least one other functional group (abbreviated as G2) capable of binding chemically and/or physically to the elastomer chains,
→ as sili
Bomal Yves
Durel Olivier
Dawson Robert
Rhodia Chimie
Robertson Jeffrey B.
Seugnet Jean-Louis
LandOfFree
Use of a combination of silicone compounds as a coupling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Use of a combination of silicone compounds as a coupling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Use of a combination of silicone compounds as a coupling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2493452