Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1994-04-29
1995-12-05
Edwards, N.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
428373, 525177, 162197, 2641761, 26421114, 26421115, 2642108, 264130, D02G 300
Patent
active
054727804
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a soil-repellent monofilament for paper machine wire-cloths, having a diameter from 0.2 to 0.7 mm, of at least 85% by weight of polyethylene terephthalate having a viscosity index (V.I.) of at least 96 dl/g and a copolymer, processes for production, and its use.
By "soil-repellent" properties for paper machine wire-cloths are meant the wet soiling, which also predicates hydrolysis resistance. The soil repellency is intended to lengthen the cleaning cycles of a wire-cloth, the cleaning work being done under a high-pressure water jet and if necessary under friction with a brush. Soil-repellent monofilaments which should also be hydrolysis-resistant at the same time are woven into industrial cloths and used in particular in the dryer part of a paper machine. Such drying wire-cloths are exposed to temperatures far above 100.degree. C. and moisture and, during cleaning, also to increased mechanical stress. Soil-repellent polyester monofils have failed because of their ease of hydrolysis. The addition of additives in the form of stabilizers brought about a further improvement in the hydrolysis resistance, but it is still not sufficient for paper machine wire-cloths of the dryer part. Apart from adding additives, other attempts to enhance the soil-repellent properties include using suitable spin finishes, finishing treatments on the filament, and aftertreatment on the cloth.
Similarly, monofilaments were produced from the copolymer ethylenetetrafluoroethylene, whose thermal and chemical resistance are excellent and are therefore used in chemical process technology. Paper machine dryer wire-cloths are known which carry such monofilaments at the cloth surface and which protect the polyester monofilament base fabric underneath from soiling. However, the excellent chemical properties of the fluoropolymers are coupled with their inadequate tensile strength and elongation properties. Moreover, the production and disposal of a fluoropolymer having a fluorine content of about 50% is very costly compared with a polyester. Attempts have already been made to combine the mechanical properties of a mechanically stable a filament with the desirable chemical properties of a fluoropolymer by sheathing the mechanically stable filament by coextrusion with a fluorine-containing polymer (De-A-3301270). The sheath was kept as thin as possible for economic reasons. However, the known core-sheath threads are not suitable for use as paper machine wire-cloths with repeated use and cleaning under the rough conditions in the operation of a paper mill.
SUMMARY OF THE INVENTION
The object of the invention is to provide a soil-repellent monofilament which meets the high requirements of an industrial cloth in respect of its chemical, soil-repellent, mechanical and abrasion-resistant properties and finds use in particular in the dryer part of a paper machine wire-cloth.
It is a further object of the invention to provide a process which permits the economical production of soil-repellent monofilaments.
The object is achieved according to the invention when the monofilament contains from 1.5 to 5% by weight of a polynary copolymer prepared from alkenes and perfluoroalkenes.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing a diagram of soiling index of a soil-repellent monofilament in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention a monofilament is proposed which contains 1.5 to 5% by weight of a polynary copolymer prepared from alkene and perfluoroalkines.
It is advantageous to use a polyester consisti
REFERENCES:
patent: 3562200 (1971-02-01), Jones
patent: 3723373 (1973-03-01), Lucas
patent: 4002581 (1977-01-01), Doke
patent: 4822454 (1989-04-01), Meirowitz et al.
patent: 5283110 (1994-01-01), Gardner et al.
Baris Halim
Lerch Erwin
Edwards N.
Rhone-Poulenc Viscosuisse SA
Striker Michael J.
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