Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1995-02-27
1998-06-02
Ryan, Patrick
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428394, 428395, 2642101, 2642111, 26421113, 26421114, 525446, 528 26, D02G 300
Patent
active
057596859
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for producing soil-repellent and abrasion-resistant monofilaments of a diameter of between 0.1 to 1.0 mm from linear polyethylene terephthalate/polydialkyl siloxane for producing screen fabrics, as to the monofilaments produced by the process and to methods of using the monofilaments.
"Soil-repellent" properties for screens of paper-making machines are generally understood to mean wet soiling properties, which also presupposes hydrolysis resistance. The soil repellence is intended to be used for extending the cleaning cycles of a screen, wherein cleaning is performed under a high-pressure water stream and, if required, by rubbing with a brush. Soil-repellent monofilaments are worked into industrial fabrics which are employed in the wet portion, in the pressing as well as the drying portion of a paper-making machine. Such screens are subjected to moisture and temperatures far above 100.degree. C., as well as increased mechanical stress during cleaning. Pure polyester monofilaments have disadvantages based on their tendency to soil, their susceptibility to hydrolysis and their relative brittleness. An improvement in their hydrolysis resistance was achieved by adding additives in the form of stabilizers. An increase in soil repellency was attempted, besides the addition of additives, also by suitable finishing treatments of the filament and aftertreatment of the fabric.
"Abrasion-resistant" monofilaments are understood to be those monofilaments with which no actual weight loss could be noted during fibrillation testing as well as only little or no fibrillations.
It was found that co-polyesters modified with siloxanes were excellently suited for the above-mentioned field of use, in spite of their low hydrolysis resistance, because their surface properties are easily modified to provide improved sliding properties and smaller coefficients of friction, by which the brittleness is clearly reduced and soil repellency considerably improved. The formed surfaces can be easily treated again to improve their chemical properties, such as hydrolysis resistance.
Polyester/polydimethyl siloxanes, which are available either in granulate form or are modified by additives directly prior to extrusion, have proven to be especially suitable. Polyoxysilanes of the type which constitute modified polyesters and are provided for use in accordance with the invention are known from U.S. Pat. No. 5,123,392. The known chemically modified polymers are used for producing hydrophilic staple fibers, but are also said to be usable for fabrics made of filament yarns. The hydrophilic properties make possible the rapid absorption of moisture and are therefore mainly used in a mixture with cotton or wool. In their present form yarns having the hydrophilic properties mentioned, however, are unsuited for paper-making machines or fishing lines.
Silicone-modified polyesters which are suitable for producing fibers are also known from EP-A-0 269 023. In the course of producing the polymer, the silicon units are formed in a polyester matrix. During extrusion in air and drawing, these silicon units migrate into the outer envelope of the filament. The surface obtained acts like a hydrophobic film. The chemical composition is not homogeneous in cross section.
SUMMARY OF THE INVENTION
It is the object of the invention to make available a monofilament which is simultaneously soil-repellent and abrasion-resistant and homogeneous in cross section, meets the great demands made on an industrial fabric in respect to its chemical, soil-repelling, mechanical and abrasion-resistant properties and finds its use in the paper industry in particular.
The object of the invention is attained by means of the invention in that 0.15 to 5.0 weight-% of polydialkyl siloxane are inserted into the chain of the polymer by co-condensation, i.e. in the course of the poly-condensation.
The tenacity of the monofilaments is greater than 36 cN/tex with an elongation of <44% referred to the unstretched filament, wher
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Baris Halim
Fleury Etienne
Gray J. M.
Rhone-Poulenc Viscosuisse S.A.
Ryan Patrick
Striker Michael J.
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