GB2075375A - Foam application of resin to textiles - Google Patents

Abstract

Resin is applied to textile fabric from the interior of a hollow cylindrical rotatable screen (1) with a squeegee (8) of a type which rolls on the interior of the screen. The textile fabric (6) is pressed against the exterior of the screen adjacent the squeegee by a roll (5). Position of roll (5) is maintained by magnet (9) within roll (5). An amount of resin in the range 0.5% to 25% by weight of resin solids based on weight of textile fabric may be applied to a textile fabric by this process. <IMAGE>

Description

SPECIFICATION Improvements in or relating to textile finishing This invention is concerned with textile finishing, and more particularly to the application of a finishing resin to a textile fabric.

Such resins are commonly used in the textile trade to import desired properties to the fabric, for example, crease resistance, dimensional stability.

In the usual methods of application of resin to textile fabric a water soluble resin is used, and is dissolved in a substantial amount of water to enable a uniform distribution of resin on the fabric to be attained. A snag of this method is that the water then has to be dried off the fabric, which requires a substantial energy input.

It has therefore been proposed to apply the resin to the fabric as a foam in order to obtain a uniform distribution of a small amount of resin without the accompanying water. This has the advantage that less drying of the fabric is required but gives rise to a need for different techniques to apply the resin to the fabric since foam cannot be applied by the usual techniques used for solutions e.g. padding.

One approach to applying the foam is to apply a relatively stable foam to the fabric as a layer whose thickness can be controlled to control the amount of foam applied. The "relatively stable" foam is thus a foam which does not break down immediately upon contacting the fabric. The foam layer is then broken down to cause the resin to enter the fabric.

Examples of this approach are to be seen in UK Patent No. 1,430,184 and US Patent No. 4,118,526, but control of the foam layer thickness is difficult in practice, and depends upon a very uniform foam being produced.

Another approach is to apply to the fabric a relatively unstable foam, i.e. one which completely decomposes immediately upon hitting the fabric. In this case the flow rate of the foam application is used to control the amount applied to the fabric. This method is exemplified by US Patent No. 4,099,913 but requires a relatively sophisticated (and thus expensive) apparatus.

The present invention provides an alternative method of applying foamed resin to textile fabric.

According to the present invention a process for applying a resin to a textile fabric comprises forming from said resin a relatively stable foam (as hereinbefore defined), feeding said foam into the interior of a hollow cylindrical rotatable screen, rotating said screen and contacting said screen with the textile fabric, urging foam into the appertures of the screen at a location adjacent the contact area with said fabric by means of a squeegee of a type which rolls on the interior surface of the screen and pressing the fabric against the screen whereby resin from said foam is deposited on the fabric.

Preferably the foam is broken down at the screen by the combined effects of urging the foam into the screen with the rolling squeegee and the fabric withdrawing liquid foam the other side of the screen, and the gas used to make the foam is air.

The apparatus used in the process can conveniently be a rotating screen coating or printing machine, the resin foam being supplied into the centre of the screen from a foam generator through a hollow stationary core about which the screen rotates.

The foam is urged into the apertures in the screen by the operation of a squeegee in combination with the movement of the screen carrying foam towards the squeegee. The squeegee system is preferably of the type which consists of a free rolling metal rod held in correct location by magnetic means.

The foam generator may, for example, be a chamber packed with balls into which resin containing surfactant and, if appropriate, water is metered.

Compressed air is injected into the chamberthrough another inlet, foams the resin during its passage between the balls and delivers foam from a suitably positioned outlet into the screen at a rate which balances the rate at which foam is being broken and passed through the screen.

The rate at which resin is passed through the screen onto the fabric depends upon several factors e.g. the fabric composition, the density of the foam, the mesh size of the screen, the configuration of the squeegee and the location ofthe squeegee in relation to the point at which the fabric is pressed against the screen.

For instance the rate will be increased by increas- ing the screen mesh size, increasing the foam density and, where pressure is applied to the fabric by a roller pressing the fabric against the screen, locating the squeegee behind the centre of said pressure roller.

The resin to be applied may be a liquid resin, or a resin solution in water. The resin will contain a surfactant and may also contain auxiliary additives such as catalyst, softener, stiffeners, water repellants, oil repellants, optical brighteners, lubricants, fire retardant and moth proofers.

The type of resin may be any of the usual finishing resins, such as can be made with aminoformaldehyde and/or reactant resins for example, urea-formaldehyde resins and their derivatives, melamine-formaldehyde resins and their derivatives, and reactant types of resins such as dimethylol dihydroxy ethylene urea, or dimethylol iron and its derivatives.

The amount of resin applied to the fabric will be generally in the range 0.5% to 25% by weight of resin solids based on the total weight of fabric, more preferably 1% to 10% by weight of resin solids.

Thus for example, if, with a particular combination of fabric type and running conditions the passage of the fabric though the rotary screen machine gave a 25% increase in weight, then, to achieve a 2.5% resin solids addition to the fabric together with 0.1% addition of a softener the formulation to be used for foaming could be as follows: Dimethylol dihydroxy ethylene urea resin (50% solids) 20 parts by weight Polyethylene Emulsion Softener (50% solids) 0.8 parts by weight Resin Catalyst (30% w/w solid mg cf2) 4 parts by weight Surfactant (25% w/w solid sodium lauryl Sulphate) 4 parts by weight Water to 100 Alternatively if a foam of lower water content is used the weight pick-up required for the same resin treatment will be lower.

The foam density and stability and squeegee configuration and screen mesh size are preferably chosen in a combination which will ensure that the foam breaks as it passes into the screen and no further provision is needed on the fabric to ensure foam breakdown. This is in contrast with prior art methods where a layer of relatively stable foam is applied to the fabric and needs to be broken down thereon e.g.

by nip rollers.

The invention will now be described in more detail with reference to the accompanying drawing which is a diagrammatic sectional view of a rotary screen unit, using a rolling rod as a squeegee.

The unit shown comprises a seamless cylindrical screen 1, which is a mesh with a uniform pattern of apertures to give a uniform coating, the screen being so mounted asto be rotatable about its longitudinal axis as shown by the arrow in the drawing.

A longitudinal feed manifold 2 is located inside the screen but not being rotatable with the screen, and contains one or more slots through which foam can be fed into the interior of the screen along the whole length of the screen. Located on the interior surface of the screen is a rod 8 which functions a a rolling squeegee, the rod 8 being rotated by contact with the rotating screen, and serving to push the foam into the apertures in the screen 1. The rod is maintained in its correct position by a magnet, which is located inside a supporting roller 5 which serves to press against the screen 1 a textile fabric 6 to be resin treated which is fed between the two.The location of the contact area of the rod 8 on the interior surface of the screen is closely adjacent or coincides with the location of the roller pressing fabric against the exterior of the screen, the exact correlation between the two being adjustable to vary the amount of material being pushed through the screen onto the fabric.

In operation the textile fabric to be coated is fed between the roller 5 and screen 1 and resin foam 7 is fed into the screen from a foam generator (not shown). Rotation of the screen 1 carries the foam into the angle between the squeegee 8 and the screen 1,the foam thus being broken into the screen and pushed through it onto the textile fabric 6. There need not be excess pressure of foam inside the screen as a whole, gravity and the screen movement being relied upon to carry the foam to the squeegee rod 8. The process of this invention has the advantages that it uses an apparatus which is readily available and relatively inexpensive, yet it facilitates applying finishing resin uniformly at low water contents with attendant substantial cost savings in drying costs.

It is preferred that the supply of foam to the interior of the screen can be controlled according to the rate of fabric through the apparatus. The preferred foam generating system to be used in this invention is described in co-pending UK Patent Applications No 8106868 and 8109946.

Claims (8)

1. A process for applying a resin to a textile fabric comprises forming from said resin a relatively stable foam (as hereinbefore defined), feeding said foam into the interior of a hollow cylindrical rotatable screen, rotating said screen and contacting said screen with the textile fabric, urging foam into the apertures of the screen at a location adjacent the contact area with said fabric by means of a squeegee of a type which rolls on the interior surface of the screen and pressing the fabric against the screen whereby resin from said foam is deposited on the fabric.

2. A process according to claim 1 in which the foam is broken at the screen by the combined effects of urging the foam into the screen and the fabric withdrawing liquid from the other side of the screen.

3. A process according to claim 1 or 2 in which the resin foamed is a liquid or an aqueous solution containing up to 70% by weight of resin solids.

4. A process according to claim 1,2 or 3 in which the amount of resin applied to the fabric is in the range 0.5% to 25% by weight of resin based on the total weight of fabric.

5. A process according to claim 4 in which the amount of resin applied is in the range 1.0% to 10% by weight of resin based on the total weight of fabric.

6. A process according to any preceding claim in which the foam density and stability and screen mesh size in combination are such that the foam is broken down as it passes into the screen and no provision on the fabric is needed to ensure foam breakdown.

7. A process according to any preceding claim in which the squeegee system is of the type which consists of a free rolling metal rod held in correct location on the screen by magnetic means.

8. A process according to claim 1 substantially as described herein with reference to the accompany ing drawing.