US2639966A

US2639966A - Process for coating cotton fabrics

Info

Publication number: US2639966A
Application number: US190688A
Authority: US
Inventors: William R Stanton
Original assignee: Textuff Ltd
Current assignee: Textuff Ltd
Priority date: 1949-01-18
Filing date: 1950-10-18
Publication date: 1953-05-26
Anticipated expiration: 1970-05-26
Also published as: GB664157A

Description

y 1953 w. R. STANTON 2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 3 Sheets-Sheet l 3 (Own.

' I /m/em0r l/W/mm FF. Sfanfon By his altorneys y 26, 1953 w. R. STANTON 2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 s Shets-Sheet 2 //7 Van for l V/ll/am R Sfcmfon By his attorneys y 6, 1953 w. R. STANTON 2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 v '3 Sheets-Sheet 5 //7 van for W/Y/Iam R. Sfanfon By his attorneys Patented May 26, 1953 UNITED STATES PATENT OFFICE PROCESS FOR COATING COTTON FABRICS William R. Stanton, Penn, Wolverhampton, England; assignor to 'Textuffi' Limited, London, England, a British company Application. \October 18, 1950,.Serial1No. 191L688 In Great Britain January 18, 1.949-

4' Claims.

It is known to pass a textile fabric, which may be wovenv or knitted, through an aqueous bath of cellulose derivative, for. example viscose, so that the fabric becomes coated with viscose, and then to treat the coated fabric with a coagulating agent which. regenerates the cellulose in the viscose so that. a fabric coated with cellulose is obtained. Cellulose derivatives such as viscose which can be treated to obtain cellulose are hereinafter referred to as regeneratable cellulose derivatives. It is also known to treat the fabric before the coating operation with a View to reducing, the amount of air absorbed by the fabric; thus in. British specification No. 306,586, it is proposed to remove the air in. the fabric before the fabric reaches the.coating liquid, by passing the fabric through a vacuum chamber immediately above the surface of the liquid.

British specification No. 611,275 describes and claims a process for coating a knitted or woven fabric with cellulose by passing the fabric through an aqueous bath of regeneratable cellulose derivative and then treating it with a coagulating agent, wherein the fabric is treated with live steamimmediately prior to its immersion in the coating bath in order to eliminate or to reduce to a minimum absorbed air and hence the oc currence of air bubbles or pin-holes in the final product.

In. carryin out the process according to the said British specification No. 611,275 it. is found that pin-holes may still sometimes result from incomplete wetting of the fabric in the viscose bath when gases arising from the decomposition of the viscose lead to the formationof. bubbles or pin-holes in. the final product. Furthermore, there; is a marked. tendency for minute blisters or: protuberances, as distinctfrom pin-holes, to be=formed on the product.

It is the object of the. present invention to eliminate these further imperfections.

Thepresent invention comprises a process for (CL. SE -18) coating. a knitted. orwoven fabric with cellulose by treating the fabric with live steam in order to eliminate or reduce to a minimum. absorbed air in the fabric, treating the steamed fabric in an aqueous bath, preferably a hot aqueous bath, so that the fabric is uniformly wetted out, passing the fabric through a. bath of a regeneratable cellulose derivative, treating the coated fabric with a coagulating agent and, during the coating operation, continuously withdrawing part of the bath of regeneratable cellulose derivative, passing the withdrawrr baththroughat'least one filter and continuously returning the filtered bath to the coating-bath. The treatment of the steamed fabric with the aqueousbath may conveniently be effected by passing the fabric through a hotwater bath with the aid of guide rollers suitably placed for guidingthe fabric. through the bath; after withdrawal from the bath, the fabric may; be placed between squeeze rollers to remove excess water and to smooth the fabric' which is then passed directly into abath of a regeneratable cellulosederivative. The treatment of the fabric with live steam followed? by thewetting out: treatment serves to. eliminate substantially completelythe formation of pin-holes in the final product.

Investigations which I have carried out: have shown that the blisters. in the final; product are. due to fibrils ofi' the cotton or other material of the fabric; viscose tends to coagulate on these fibrils and the aggregated viscose adheres to the fabric and; appears in thefi-nal productas-minute protuberances or blisters. I have found that theseblisters may be: eliminated. or. considerably reduced by continuously circulating part" of the viscose bath through. one or more filters during thecoating operation, the filters serving to remove the fibrils of cotton and: the like. Filters consisting of? metal screens or fabrics having 15 to- 25- holes per' inchare=.particularly suitable for use in thefiltering operation.

The fabric, after the treatment with. a: hot

aqueous bath in accordance with the invention:

may becooled, by passing it-throughthe air for a distance of" say six feet, and so allowing some of the water toevaporate, or by subjecting it to a cold water spray, and then passed into the bath of viscose or otherregeneratable cellulose derivative; The coating bath is preferably divided by suitably placed vertical grids into three or more compartments in which the grids help to restrain physically any bubbles, fibrils, aggregated fluff from the fabric or coagulated particles formed in the bath and so keep them away from the jet through which the fabric leaves the bath. The bath is preferably withdrawn from the compartment nearest the jet and, after" filtering; returned to the same compart- 11181117. The viscosebath may be cooled for example by means of water at ordinary temperature (15 to 25 centigra-de) or by cooled brine circulating in pipes submerged in the bath. (3001- ing the viscose in this way tends to limit the aging. of the, viscose which otherwise results from the heating of the" viscose by the heated fabric passing through the' bath.

The aqueous bath preferably contains a wetting agent such as a sulphonated long chain fatty alcohol in order to improve the wetting out of the fabric.

The aqueous bath may also contain a dyestuff which is substantive to the material of the fabric so that the fabric is coloured after the steaming treatment. In this case the viscose or other regeneratable cellulose derivative bath may be pigmented preferably so that the coating will have the same colour as the fabric; examples of dyes suitable for use with cotton are the water-soluble dyes which are resistant to both alkali and acid and are so unaffected by either the caustic soda in the viscose or the acid used as the coagulating agent. Chlorazol Sky Blue FF (Colour Index No. 518) and Diphenyl Red '7 BL (Colour Index No. 278) are specific examples of such dyes. The aqueous bath may conveniently contain from 0.1 to 0.2 per cent by weight of the dye.

The viscose used in the present invention is preferably a normal viscose 'as used for threadmaking, that is -viscose containing about '7 to 8 per cent of cellulose and about 6 to '7 per cent of caustic soda.

The knitted or woven fabric used in carrying out the present invention may be made from natural fibre such as cotton fibres or from synthetic fibres such as regenerated cellulose fibres, particularly viscose rayon fibres.

The present invention is illustrated by way of example in the accompanying drawings in which Figure 1 is a schematic representation of the steps in the process for producing a cellulosecoated fabric,

Figure 2 is a vertical section through the steam chamber wetting out bath and viscose coating bath of the apparatus shown in Figure 1 but on a larger scale,

Figure 3 is a vertical section through the filtering apparatus for circulating the viscose bath, also on a larger scale, and

Figure 4 is a section on the line 4-4 of Figure 3 but with only one of the tubes sectioned.

Referring to Figure 1, a fabric I is first passed through a steam chamber 2 into a bath 3 containing a wetting-out solution 4 and the wet fabric is then led into a bath 5 containing viscose or other regeneratable cellulose solution 6. The solution 4 may contain a dyestuff for the fabric I and the cellulose solution 6 may contain a pigment. The coated fabric leaves the bath 5 through an adjustable slot I and is passed by means of a stenter 8 through an acid coagulant bath 9. It is then washed free from acid in a water bath I and passed on a second stenter I I through a drier I2. Knives I3 then cut off the selvedges and the finished fabric is collected as a roll I4. Throughout the operation, part of the solution is continuously circulated by a pump I5 first through a screen filter I6, then through a cloth filter I! and finally back to the bath 5.

Referring to Figure 2, the fabric I enters the steam chamber 2 through a slit l8 and both sides of the fabric are sprayed with steam from two parallel rows of steam jets I9, 20. The steamed fabric leaves the steam chamber 2 through a second slit 2| and is passed into the wetting-out solution 4, under

rollers

22, 23 out of the bath and between mangle rollers 24 and then down to a spreading roller 25 just above the solution 6. The spreading roller 25 is of known construction with a diameter greater in the centre and tapering away towards each end, and keeps the wet fabric from crumpling. The fabric passing from the spreading roller enters the solution 6 and is passed by means of

rollers

26, 21, 28 to the nip of a pair of

rollers

29, 30 and thence horizontally through centralising rods 3| to the exit slot 1 for further treatment as described with reference to Figure 1. The bath 5 is provided with four

wire screen

32, 33, 34, held in slots on the side of the bath 5; each screenconvenientlyhassixteen holes to the inch. The

screens

32, 33, 34, 35, divide the bath 5 into three

interconnected compartments

31, 38, 39. From the compartment 39, the solution 6 is circulated continuously through the filter I6, the pump I5 and the filter I1 and back to the compartment 39 by way of a pip 40.

The filter I6 is conveniently a wire gauze filter basket 4| (Figure 3) having sixteen holes to the inch. The filter I1 consists of an outer casing 42 with a top cover 43 in which are secured seven separate filter tubes 44 each of which communicate with a space 45 above the cover 43. The tubes 44 conveniently consist of an inner perforated tube 46, a wire gauze 41 having sixteen holes to the inch wrapped around the tube 46 and a fabric filter 48, consisting of an unbleached strainer canvas having twenty-two holes per inch, Wrapped round the gauze 41. The viscose is forced upwards through the filter tubes 44 into the space 45 and thence back via pipe 40 to the bath 5.

In order to permit the passage of slubs through the slot 1 a counter-balancing weight 49 is provided, the weight being so adjusted that while a slub in the fabric I can lift the top part 50 of the jet to enable the slub to pass through, the slot will immediately revert to the predetermined width once the slub has passed.

The solution '6 may be cooled by means of a water jacket (not shown) around the bath 5 or by passing a brine solution through pipes (not shown) within the bath 5.

The invention is illustrated by the following examples in which apparatus as described in Figures 1 and 2 was used.

Percentages are by weight.

Example 1 The wetting out solution used was a 0.15 per cent aqueous solution of Diphenyl Red '7 BL at 80 centigrade, the solution containing 0.01 per cent of a sulphonated long chain fatty alcohol as a wetting agent.

The viscose used contained 7.5 per cent of cellulose and 6.25 per cent of caustic soda, was aged to a salt figure of 4.0, was pigmented with 9 per cent of Monolite Fast Red 2 RVS (page 173 of Pigments by J. S. Remington, published by Leonard Hill, Ltd.) and 3 per cent of titanium dioxide based on the weight of the cellulose, and contained 0.15 per cent by weight, based on the weight of the cellulose, of a sulphonated long chain fatty alcohol. The temperature of the viscose bath was maintained at approximately room temperature (20 centigrade). During the coating operation, viscose was continuously circulated through a sixteen mesh basket sieve and a twenty-two mesh unbleached strainer canvas as described above with reference to the drawings.

The product was an all-red cellulose-coated fabric.

Example 2 solution containing 0.01 per cent of a sulphonated long chain fatty alcohol as a wetting agent.

The viscose used was the same as that used in Example 1 except that the Monolite Fast Red 2 RVS and titanium dioxide pigment mixture was replaced by a mixture of 4 per cent of Irgalite Blue KRV (Geigy Chemical Company) and 4 per cent of titanium dioxide based on the weight of the cellulose.

An all-blue cellulose-coated fabric was obtained.

Example 3 The solution used was a 0.15 per cent aqueous solution of Chlorazol Green GS (Colour Index No. 599:) at 80 centigrade, the solution containing 0.01 per cent of a sulphonated long chain fatty alcohol as a wetting agent.

Thelviscose used was the same as that used in Example 1 except that the mixture of pigments used contained 4 per cent of Monastral Fast Blue BVS (Journal of the Society of Dyers and Colourists, 1943, page 223), 5 per cent of Monolite Fast Yellow GNVS (Journal of the Society of Dyers and C'olourists, 1943, page 223), 8 per cent of titanium dioxide and 0.25 per cent of carbon black, based on the weight of the cellulose.

An all-green cellulose-coated fabric was obtained.

What I claim is: 1

1. A process for coating a cotton fabric with cellulose which comprises treating the fabric with live steam in order to remove absorbed air in the fabric, passing the steamed fabric through an aqueous bath containing a wetting agent suitable for wetting out cotton so that the fabric is uniformly wetted out, passing the wetted fabric through a viscose bath, treating the; viscosecoated fabric with a coagulating agent,f and, during the coating operation, continuously withdrawing part of the viscose from the bath, passing the part so removed through at least one filter to remove the fibrils of cotton in the viscose, and continuously returning the filtered viscose to the coating bath. 1

2. A process as claimed in claim 1 in which the aqueous wetting out bath is heated and the wetted fabric is cooled before it is passed into the viscose bath.

3. A process for coating a cotton fabric with cellulose which comprises treating the fabric with live steam in order to remove absorbed air in the fabric, passing the steamed fabric through an aqueous bath containing a wetting agent suitable for wetting out cotton and at least one water-soluble direct cotton dyestuff substantive to the material of the fabric, so that the fabric is uniformly wetted out and dyed in the bath, passing the wetted dyed fabric through a viscose bath containing at least one pigment, the dyestuffs and the pigments being so selected that the cellulose coating has the same colour as the dyed fabric, treating the viscose-coated fabric with a coagulating agent, and, during the coating operation, continuously withdrawing part of the viscose bath, passing it through atleast one filter to remove the fibrils of cotton the viscose and continuously returning the filtered viscose to the coating bath.

4. A process for coating a cotton fabric with cellulose which comprises treatingthe fabric with live steam in order to remove absorbed air in the fabric, passing the steamed fabric through an aqueous bath containing a sulphonated long chain fatty alcohol wetting agent so that the fabric is uniformly wetted out, passing the wetted fabric through a viscose bath, treating the viscosecoated fabric with a ccagulating'agent, and, during the coating operation continuously withdrawing part of the viscose bath, passing it through at least one filter to remove the fibrils of cotton in the viscose and continuously returning the filtered viscose to the coating bath.

WILLIAM R. STANTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,942,383 Dickhaut Jan. 2, 1934 2,378,186 Clark June 12, 1945 FOREIGN PATENTS Number Country Date 280,262 Great Britain Nov. 15, 1927 611,275 Great Britain Oct. 27, 1948

Claims

3. A PROCESS FOR COATING A COTTON FABRIC WITH CELLULOSE WHICH COMPRISES TREATING THE FABRIC WITH LIVE STREAM IN ORDER TO REMOVE ABSORBED AIR IN THE FABRIC, PASSING THE STEAMEDD FABRIC THROUGH AN AQUEOUS BOTH CONTAINING A WETTING AGENT SUITABLE FOR WETTING OUT COTTON AND AT LEAST ONE WATER-SOLUBLE DIRECT COTTON DYESTUFF SUBSTANTIVE TO THE MATERIAL OF THE FABRIC, SO THAT THE FABRIC IS UNIFORMLY WETTED OUT AND DYED IN THE BATH, PASSING THE WETTED DYED FABRIC THROUGH A VISCOSE BATH CONTAINING AT LEAST ONE PIGMENT, THE DYESTUFFS AND THE PIGMENTS BEING SO SELECTED THAT THE CELLULOSE COATING HAS THE SAME COLOUR AS THE DYED FARBIC, TREATING THE VISCOUSE-COATED FABRIC WITH A COAGULATING AGENT, AND DURING THE COATING OPERATION, CONTINUOUSLY WITHDRAWING PART OF THE VISCOSE BATH, PASSING IT THROUGH AT LEAST ONE FILTER TO REMOVE THE FIBRILS OF COTTON IN THE VISCOUS AND CONTINUOUSLY RETURNING THE FILTERED VISCOSE TO THE COATING BATH.