Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-12-10
2004-12-07
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S212000, C523S344000, C523S351000, C523S353000, C524S492000
Reexamination Certificate
active
06828361
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for making a rubber base composition containing silicic acid. This method is carried out in two stages in separate mixers and the composition ingredients silicic acid, silane and other usual additives except vulcanization ingredients are mixed and the silicic acid reacts with the silane.
BACKGROUND OF THE INVENTION
Rubber compositions containing silicic acid are used today for making the most varied rubber products, especially, for making tires for motor vehicles. In motor vehicle tires, the silicic acid replaces for the most part the earlier conventional carbon black constituents. This is so because it has been shown that motor vehicle tires acquire improved tire characteristics with respect to wet resistance and rolling resistance because of the addition of silicic acid. For producing the rubber composition, a silicic-acid containing rubber base composition is produced first in a base mixing process in one or several mixing stages. This rubber base composition does not yet contain vulcanization ingredients (vulcanization chemicals such as sulfur, sulfur donors, accelerators or resins). In a final mixing process, the vulcanization ingredients (vulcanization chemicals) are added to the rubber base composition and the finished rubber composition (final composition) results.
In the production of the rubber base composition, coupling agents in the form of silanes are added to the rubber base composition in addition to the silicic acid in order to make possible a binding of the silicic acid to the rubber. The silanes are, inter alia, bifunctional organic silanes such as 3-mercaptopropyl triethoxy silane, 3-thiocyanato-propyl trimethoxy silane or 3,3′-bis(triethoxy silylpropyl)polysulfide with 2 to 8 sulfur atoms. In a first step, and during the base mixing, the added silane reacts with the silanol groups of the silicic acid and, in a second later step, during the vulcanization of the rubber composition, the silane reacts with the rubber, whereby the silicic acid is bonded to the rubber via the silane. The first reaction step and therefore the manufacture of the rubber base composition is very time intensive.
U.S. Pat. No. 5,804,636 discloses a method for making a silicic-acid containing rubber base composition of the kind mentioned initially herein. In a first stage of the method, the composition ingredients of rubber, silicic acid and additional additives except the vulcanization ingredients are mixed with each other at a temperature in the range of 165° C. to 170° C. in a first mixer. After mixing the composition ingredients, the composition is removed from the first mixer, cooled and transferred to a second mixer. In the second mixer, silane is added to the composition and the composition is mixed to completion at a temperature of 135° C. and the silane reacts with the silicic acid. Because of the high temperature of the composition in the first mixer, it is ensured that the composition ingredients disperse rapidly and well; whereas, a thermal decomposition of the silane is avoided by maintaining the temperature of 135° C. in the second mixer. Furthermore, by using two mixers, the advantage is provided that, at the same time, a rubber base composition without silane is mixed in the first mixer and, in the second mixer, a rubber base composition with silane can be mixed to the end. In this way, the expenditure of time for producing a rubber base composition containing silicic acid is shortened.
It is, however, noted that in the method set forth in U.S. Pat. No. 5,894,636, the silicic-acid containing rubber base composition must be cooled down in an intermediate step which leads to an additional expenditure of time and storage.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a simple method for producing a silicic-acid containing rubber base composition which can be executed with a reduced expenditure of time.
The method of the invention is for making a silicic acid containing rubber base composition. The method includes the steps of: providing composition ingredients of rubber, silicic acid, silane and additional additives except for vulcanization ingredients; providing first and second mixers separate from each other wherein the ingredients except for the vulcanization ingredients can be mixed; introducing all of the composition ingredients into the first mixer except for the vulcanization ingredients simultaneously or at time intervals; mixing the composition ingredients introduced into the first mixer to a composition in the first mixer; transferring the composition formed in the first mixer directly into the second mixer without an intermediate storage thereof; and, mixing the transferred composition formed in the first mixer at least almost to completion in the second mixer with the temperature lying in the temperature range of 130° C. to 180° C. at least over the greatest part of the dwell time of the composition in the second mixer wherein the silicic acid reacts acceleratedly with the silane.
In the first and second mixer, a rubber base composition is therefore produced and, in the second mixer, the silane reacts almost completely with the silanol groups of the silicic acid (that is, the rubber base composition is then at least mixed almost to the end). At further processing stations, the rubber base composition is processed further and, in the last processing station, the vulcanization ingredients (vulcanization chemicals) are added to the rubber base composition and the rubber base composition is there mixed to completion in a final mixing process.
In the first mixer, the usual composition ingredients are dispersed in the rubber (or in the rubbers). Here, the temperature of the composition is increased up to a maximum of 180° C. in order to substantially prevent a scorching of the composition. It is possible that the composition temperature lies below 130° C. in advance of transferring the composition from the first mixer into the second mixer. In this case, the composition temperature is increased to a temperature in the temperature range of between 130° C. and 180° C. in the second mixer before the composition is mixed to the end in the second mixer. To adjust the temperatures in the mixers, the fill level of the mixture, the rpm of the rotors of the mixers, the mixer temperature control and the plunger pressure of the mixers (insofar that the corresponding mixer includes a plunger) are matched to each other.
An advantage of the invention is especially that the method can be executed with a reduced expenditure as to both time and space because an intermediate storage and cooling of the rubber base composition after separating the same from the first mixer is unnecessary. A further advantage of the invention is that all composition ingredients of the rubber base composition are introduced into the first mixer and therefore also only stationary metering devices are needed in the region of the first mixer. Furthermore, it is ensured that the individual composition ingredients in the rubber base composition are present in the correct amounts. (At this point, it is noted that in the method known from U.S. Pat. No. 5,804,636, the above is not ensured. Accordingly, it can happen that, when separating the rubber base composition from the first mixer, composition ingredients remain in the first mixer so that the rubber base mixture in the second mixer is supplied with too much silane; on the other hand, it can be that residual amounts from previous mixture operations are separated from the first mixer with the rubber base composition so that the rubber base composition is supplied with too little silane in the second mixer.)
Compared to a method for producing a rubber base composition wherein only a single mixer is used, the invention affords the advantage that the first and the second mixers can be operated simultaneously so that the clock time is shortened in which a rubber base composition is mixed to the end. A shortening of the clock time can also be achieved in that one sets up two indi
Gross Dirk
Heidrich Winfried
Peter Julius
Sandau Heinrich
Continental Aktiengesellschaft
Ottesen Walter
Yoon Tae H.
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