Method for the surface modification of products made of low-energy synthetic fibers

Abstract

The invention relates to a wet chemical method for the surface modification of products made of low-energy synthetic fibers, to the products produced by the method and to the use of the products produced by the method. The material surface is permanently provided with functional groups by contact with an aqueous polyvinylalcohol solution containing silanol(ate) groups. Depending upon the design, the materials have a high water consumption or transmission capacity or exhibit a capillary activity. The range of uses for surface-modified materials is extended by the possibility of reacting the functional groups, inter alia, with biologically active components.

Claims

1. A method for surface modification of a product made of fibres having a surface, wherein the fibres consist of low-energy synthetic fibres having a free surface energy of less than 40 mN/m, the method comprising the steps of contacting the product with an aqueous solution having a pH of between 2 and 5, the aqueous solution comprising polyvinyl alcohol having silanol(ate) groups and water as a solvent, and then removing the solvent from the products, wherein the silanol(ate) groups are reacted with each other by condensation reaction to form a functionalized fibre surface having hydroxyl groups.

2. The method according to claim 1, wherein the polyvinyl alcohol having silanol(ate) groups comprises the formula
CH(OH)CH.sub.2CH(OAc)CH.sub.2CH(Si(ONa).sub.3)CH.sub.2CH(OAc)CH.sub.2CH(OH)CH.sub.2 wherein Ac is acetyl.

3. The method according to claim 1, wherein a concentration of the polyvinyl alcohol having silanol(ate) groups in the solution ranges from 0.001% (w/v) to 40% (w/v).

4. The method according to claim 1, wherein the aqueous solution comprising polyvinyl alcohol having silanol(ate) groups contains other substances that influence at least one of surface tension and viscosity of the aqueous solution.

5. The method according to claim 1, wherein the method comprises the step of contacting all or part of the surface with the aqueous solution comprising polyvinyl alcohol having silanol(ate) groups.

6. The method according to claim 5, wherein the contact is effected manually.

7. The method according to claim 5, wherein the step of contacting takes place with the aid of machines, in-line and at production speed.

8. The method according to claim 1, wherein the step of removing the solvent from the products comprises drying.

9. The method according to claim 8, wherein the drying takes place at a temperature of between 1 C. and 130 C.

10. The method according to claim 8, wherein the drying is carried out at room temperature on a washing line.

11. The method according to claim 8, wherein the drying is carried out with the aid of mechanical aids and in-line at production speed.

12. The method according to claim 8, wherein the products have a residual moisture of between 0% and 40% after drying.

13. The method according to claim 1, wherein the low-energy synthetic fibres consist of a material selected from the group consisting of aramids, polyesters, polyamides, polyacrylates, polyacrylonitriles, polyurethanes, (per)fluorinated polyolefins, polysulfones, polyimides and polyolefins, and co- or terpolymers thereof.

14. The method according to claim 1, wherein the product is selected from the group consisting of filaments, monofilaments, multifilaments, fibres, threads, yarns, strings and rovings.

15. The method according to claim 1, wherein the product is selected from the group consisting of a filament composite material, a fibre composite material and combinations thereof.

16. The method according to claim 1, wherein the product is configured as an article selected from the group consisting of a sinkable fishing line, a means of conveyance for water, a raw material for textile fabrics, a textile fabric, a filter material for aqueous media, a blood and body fluid-absorbing wound dressing, a moisture-absorbent and permeable hygienic article, a substrate for the immobilisation of biologically active substances, a cell cultivation substrate, and substrate for non-electric metallisation.

17. The method of claim 1 wherein the step of removing the solvent comprises reacting the silanol(ate) groups with each other by condensation reaction to form a condensed molecule enveloping the fibre surface.

18. A method for surface modification of a product made of fibres having a surface, wherein the fibres consist of low-energy synthetic fibres having a free surface energy of less than 40 mN/m, the method comprising the steps of: providing an aqueous solution having a pH of between 2 and 5 and consisting essentially of polyvinyl alcohol having silanol(ate) groups and water as a solvent, and optionally one or more of aliphatic alcohols, surfactants, wetting agents, pyrogenic silicic acid and metal salts; contacting the product with the aqueous solution; and removing the solvent from the product to form a functionalized fibre surface having hydroxyl groups.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The surface-modified products made of low-energy synthetic fibres surface-modified according to the method of the present invention can be used as filament or fibre material for textile fabrics, as textile fabrics, as textile fabrics that can be dyed with water-soluble dyes, as geotextile fabrics, as filter materials, as wound dressings, as hygiene articles, as substrates for the immobilisation of biologically active substances, as cell cultivation substrates, as substrates that can be metallised, as sinkable fishing line etc.

Example 1

(2) The polyvinyl alcohol with silanol(ate) groups used is R-Polymer R-1130 from the company Kuraray in Frankfurt.

(3) Solution: For the surface-modification of low-energy materials, a 1% (w/v) aqueous R-1130 solution is used, which is produced as follows: 10 g of R-Polymer is added to 1,000 ml of de-ionized water at room temperature and then heated up to 90 C. with constant stirring until the polymer is fully dissolved. The pH is adjusted to 3 with diluted acetic acid.

(4) Material: fibre composite material: polypropylene spunbond with 10, 20 and 30 g/m2 area density from the company Fiberweb Corovin, Peine.

(5) Contact: ca. 5 A4-sized sheets of spunbond are placed on top of each other in a suitable tray and approx. 100 ml of the abovementioned R-Polymer solution is poured over them. Due to the hydrophobic nature of the spunbond material, the solution does not penetrate it, but beads off. A thorough, bubble-free penetration of the polymer solution is only possible with the aid of a squeezer (equivalent to the foulard in an industrial application).

(6) Drying: the dripping wet spunbond sheets are hung on a washing line and dried at room temperature.

(7) Result: compared with untreated non-wovens, the spunbond can be soaked with water again and again even after repeated drying. The dried sheets feel substantially stiffer at the bottom than at the top where they were fixed to the washing line with clothes pegs. This difference in the grip is much more pronounced in the 35 g/m2 spunbond than in the others, and is even retained after several washes.

(8) There is a significant dyeing with Simplicol which is not washed out (Simplicol: dye for dyeing cotton from the company Brauns-Heitmann, Warburg, Germany)untreated control samples do not take the dye.

Example 2

(9) Solution: as in Example 1 but with additional 2% (v/v) 2-propanol

(10) Material: fibre composite material: A4-sized needle felt sheets of polypropylene, Sawatex 11311Di52 25 g/m2 from the company Sandler, Schwarzenbach.

(11) Contact: manual, similar to Example 1 but without the squeezer as the material is immediately completely wet through due to the added 2-propanol.

(12) Drying: as Example 1.

(13) Result (WSP test method, always compared with the untreated control sample): maximum water absorption: 1,200 vs. 485 permeation time, 3 cycles (repeated strike through): always <4 seconds vs. >40 seconds.

(14) Readily dyed with Simplicol, untreated control sample does not take the dye.

Example 3

(15) Solution: as Example 1 with the addition of 0.25% (v/v) Silastan RN Neu (a wetting agent from the company Schill and Seilacher, Bblingen).

(16) Material: fibre composite material: a non-woven material with an area density of 45 g/m2 and 900 mm width produced on the pilot plant of the company Trtzschler, Egelsbach by water jet linking of staple fibres of polypropylene. The production of the non-woven fabric and its contact with polymer solution and drying took place at varying speeds of the plant between 30 and 100 m/min.

(17) Contact: in-line, immediately after production of the non-woven material using a spraying system from the company Weko Biel AG, CH-Biel.

(18) Drying: in-line, immediately after the contact by means of an industrial drying oven at a drying temperature of 110 C.

(19) Result: on contact with water, the non-woven material is immediately saturated and sinks in the water. After repeated washing with water followed by drying, the water absorption slows down but is retained.

(20) The bonded hydroxyl (OH) groups can always be detected by dyeing with Simplicol, whereby materials produced at lower machine speeds are more intensively dyed.

(21) The material can be readily dyed with the cationic dye pyronin G. This is attributed to the fact that silanol groups which did not participate in the condensation are now, on being dyed at pH 7, anionic silanolate (Si(O3)) groups which bind the cationic dye ionogenically.

(22) The hydroxyl (OH) groups were esterified with betaine (=contacting the material overnight with a 2.5% (w/v) aqueous betaine solution, pH 3). Then anionic compounds such as copper(II) phthalocyanine-tetrasulfonic acid tetrasodium salt link from the aqueous phase with the unbounded cationic trimethyl ammonium groups of the betaine.

Example 4

(23) Solution: as in Example 3.

(24) Material: essentially 1-dimensional synthetic fibre: 722 filaments of polypropylene with 2.7 dtex and a length in the kilometer range, produced on the pilot plant of the company Fibervisions, DK-Varde by melt spinning.

(25) Contact: immediately after leaving the spinneret, the 722 filaments are led continuously at production speed through a bath containing the solution, and then joined to form a small tow and wound.

(26) Drying: wound as small tow, at room temperature, drying time: several days

(27) Results: Positive dyeing with Simplicol.

(28) Significant capillary effect: one end of a small tow immersed in (dyed) water draws the water over a distance of around 300 mm vertically upwards within 24 hours.

Example 5

(29) Solution: as in Example 2.

(30) Material: filament composite material: T-shirt made of polyethylene terephthalate

(31) Contact: manual, bubble-free fulling of the solution

(32) Drying: manual wringing and hung on clothes line at room temperature Results: compared with the untreated control sample, the T-shirt dries much more slowly even after repeated washing.