Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1997-07-22
1999-05-18
Mayekar, Kishor
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
204164, 204165, H05F3/00
Patent
active
059048174
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the chemical modification of thermoplastics that contain alkyl groups and to chemically modified thermoplastics that contain alkyl groups.
It is known that thermoplastics that contain alkyl groups, for example polyolefins and copolymers of polyolefins, can be used in many fields. If shaped parts or sheets are produced from the thermoplastics that contain alkyl groups, and if the intention is for them subsequently, for example, to be painted, coated, printed on or adhesively bonded, then it is necessary to pretreat the shaped parts and sheets. This pretreatment consists, for example, in a flame treatment, a corona treatment or a plasma treatment. This being the case, further to the poor selectivity and variability of known treatment processes, other disadvantages are that provision of the treatment devices requires increased technical outlay, and differing geometry of the shaped parts and sheets makes it necessary to have treatment devices of relatively large volume.
"Kunststoff-Taschenbuch", 25th edition, pages 248 to 259 discloses a process for the after-treatment of solids that contain alkyl groups. In this case, the surface of the solid that contains alkyl groups, for example a PE surface, is treated using a high-voltage plasma, in order to achieve local chemical modification. The effect achieved as a result of this local surface treatment, for example in the case of shaped parts, is an improvement in the paintability or printability. However, a disadvantage in this case is that an additional after-treatment must take place, application of which is possible only under certain circumstances, owing to the need to provide a high-voltage plasma system for the finished product.
The object of the invention is therefore to provide a process of the generic type, with which chemical modification of thermoplastics that contain alkyl groups can be carried out in simple and cost-effective fashion.
According to the invention, this object is achieved in that the thermoplastics that contain alkyl groups are granulated and subjected to a plasma treatment in a frequency range of from 10 kHz to 10 GHz. It has surprisingly been found that, by converting the thermoplastics that contain alkyl groups into a granulate form, and by plasma-treating them, a deliberate alteration of material properties can be brought about within the thermoplastics that contain alkyl groups. High-quality and high-quantity chemical modification can be achieved as a result of the conversion into granulate form. In particular, the plasma treatment of the granulated thermoplastics can be used to obtain chemical specialty products which can be used in a wide variety of ways, without a further expensive after-treatment being needed. In particular, shaped articles and sheets produced from the treated thermoplastics can, without additional prior after-treatment, for example be painted, coated, printed on, adhesively bonded, etc. A simple and preferable way of grading the chemical modification of the thermoplastics that contain alkyl groups is to set a particle size for the granulate and/or parameters in the plasma treatment.
In an advantageous configuration of the invention, provision is made for the plasma treatment to be carried out with varying frequencies, preferably with combinations of varying frequencies of different value. It is thus possible, very advantageously, to carry out the plasma treatment with frequencies which can be switched on sequentially, with frequencies of different value which can be switched on alternately, with at least two frequencies of different value which can be switched on simultaneously, and frequency-switching combinations resulting from these. By means of this, the chemical modification can very advantageously be tailored to the different chemical structure of the thermoplastics that contain alkyl groups which are used, and their intended use after the chemical modification.
In a further advantageous configuration of the invention, provision is made for the plasma treatment to be
REFERENCES:
patent: 4626473 (1986-12-01), Loh et al.
patent: 5234723 (1993-08-01), Babacz
patent: 5283086 (1994-02-01), Kodama et al.
patent: 5549795 (1996-08-01), Gregoire et al.
Arplas Gesellschaft Fur Plasmatechnologie mbH
Mayekar Kishor
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