Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-01-20
1999-11-02
Yoon, Tae
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523440, 524541, 528503, C08J 322, C08J 324, C08L 6106
Patent
active
059772140
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for producing molding compounds which comprise as the bonding agent resins or mixtures of resin and curing agent, which cure above an onset temperature above their melting points. The most important such bonding agent is a mixture of novolak and hexamethylene tetramine.
For corresponding phenolic resin molding compounds currently three production processes exist which differ in principle (cf. Kunststoff-Handbuch, Vol. 10, Duroplaste, 2nd Edition, Hanser Verlag 1988, pp. 211-213): the liquid-resin process in which the fillers are impregnated with resin solution and the moist substances obtained in this way are dried and further condensed to the desired degree of condensation. Working with corresponding moist substances is undesirable in operational practice since their clean handling is difficult and drying represents an additional high-energy operation.
In the turbomixer process the components of the molding compound are homogenized in high-speed mixers with short mixing times. A high input of energy through the mixer results can only be poorly regulated and is distributed unevenly. Consequently, problems in reproducibility result. In particular, the degree of condensation of the precondensed substances is not uniform. Such problems are fewer in the so-called fused mass process. Here premixtures are produced from ground solid resin, curing agent as well as filler and additive substances, which are subsequently further processed on rollers or in kneaders. Through the input of energy due to the friction the resin melts, impregnates the filler substances and is largely precondensed to the desired degree. The product produced in this way is cooled and the brittle substance obtained is ground. In the process, high dust components are generated and the curable molding compounds must additionally be screened and sorted to size.
It is therefore the task of the invention to avoid these disadvantages, i.e. to describe an economic process for producing duroplastic molding compounds in which, requiring few operational steps with minimum energy input, a uniformly condensed and readily reproducible product is obtained which is ground or granulated to a desired grain size without high dust fractions being generated.
Solving the task takes place through processes according to claims 1 to 10.
It was found that a very simple production process for molding compounds can comprise that the at least partially melted resin is added to a premixed mixture comprising filler substances and/or fibers, additive substances and, as far as necessary, added to the curing agent and thoroughly mixed with it. Good wetting and impregnation of the filler substances and fibers results as well as high homogeneous mixing. The introduced frictional energy is very low since the temperature increase of the mixture results essentially from the cooling of the resin melt. This is especially favorable if the melt resulting in the production of the resins is used directly.
But, surprisingly, in this process no pasting together and no brittle chunks are formed but rather a free-flowing, small-grain product is obtained which can be reduced to the desired grain size without significant dust formation. Thus, through this simple process several operational steps are saved. Since the mixing process is gentler than the previously described processes, in particular long fibers are less detrimentally affected, i.e. from the molding compounds produced according to the invention molded bodies can be produced with have improved resistance to impact and notched-bar strength.
In the simple embodiment of the present invention the mixing process is controlled such that the temperature in the mixing apparatus, i.e. accordingly also the temperature of the produced molding compound, remains below the onset temperature of the curing reaction.
Within prior art it is customary in the production of molding compounds, in particular such based on phenolic resins, to adjust the resins to a desired higher degree of curing in order to adapt the fl
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Patent Abstract of Japan, vol. 096,No. 006 Jun. 1996 & JP 08 034858 A Shin Etsu Chem. Co., Ltd. Feb. 1996 (1 pg).
Patent Abstracts of Japan, No. 63161018, Jul. 4, 1988 & No. 61307721, Dec. 25, 1986, Nagase Rihei, (1 page).
Adolphs Peter
Hermann Michael
Knorr Herbert
Muller Bernhard
Nolte Werner
Bakelite AG
Yoon Tae
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