GB2247411A

GB2247411A - Producing foam

Info

Publication number: GB2247411A
Application number: GB9014152A
Authority: GB
Inventors: Kenneth Wild
Original assignee: ICS Texicon Ltd
Current assignee: ICS Texicon Ltd
Priority date: 1990-06-26
Filing date: 1990-06-26
Publication date: 1992-03-04
Also published as: GB9014152D0

Abstract

Apparatus for producing a foamed, for example, flurocarbon protection medium for application to fabric surfaces, comprising a bead column (22) to which a controlled gas/liquid mixture is forced under pressure, via an injector (19), from a pressurised gas supply (10, 11) and a liquid reservoir (16) containing a foamable liquid. The tortuous path matrix provided by the bead column, (22) produces at its upper end a fine textured foam which may be applied in sheet-like form to the fabric surface to be treated via an applicator head (25) having a narrow slot opening (32). <IMAGE>

Description

APPARATUS FOR PRODUCING A FOAMED FABRIC PROTECTION MEDIUM THIS INVENTION concerns apparatus for producing a foamed protection medium such as a fluorocarbon, for application to a fabric surface. The invention has particular application in the treatment of made-up suites of furniture prior to dispatch to end users.

An example of such a fabric protector is a fluorocarbon produced and sold by Minnesota Mining and Manufacturing Corporation under their trade mark SCOTCHGARD. This treatment protects the fabric from absorption by aqueous or oily contaminants and thus renders the fabric more readily cleaned using conventional cleaning processes.

The treatment is also very well known for the protection of carpets so that if staining liquids are spilled on the carpet they may be readily removed, not being absorbed into the fibres of the carpet pile or its backing material.

This kind of treatment of furnishing fabrics has hitherto been carried out by handspraying from trichloroethylene. Typically, the contents of the canister would consist of up to 99% of the propellant and as little as 1% of the actual fluorochemical.

Whilst this method of application is very inexpensive and convenient and, being solvent-based, does ndt overwet the fabric, it nevertheless is undesirable in terms of its toxicity and environmental pollution. Indeed, it is likely that the use of such solvent repellents will be completely eliminated discontinued by legislation in the near future.

Other, more acceptable propellants are still, to a certain extent, undesirable in producing a finely dispersed aerosol of chemicals close to the operative, which also is considered a health hazard.

An object of the present invention is to provide an apparatus for producing a foamed protection medium in which the aforementioned disadvantages are substantially avoided.

According to the present invention there is provided apparatus for producing a foamed, for example, fluorocarbon protection medium for application to fabric surfaces, the apparatus comprising means for connection to a source of pressurised gas, a reservoir for containing an aqueous foamable liquid, a tortuous path matrix through which a mixture of the gas and the liquid are forced under superatmospheric pressure to generate therein a fine textured foam, an outlet duct from said matrix and an application head fed by said outlet duct and defining a restricted slot opening through which the foam may issue in a sheet-like formation for direct application to the fabric to be treated.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing which illustrates apparatus made in accordance with the invention.

The apparatus consists of a piped inlet 10 for connection to a source of compressed air such as a mains supply thereof, a compressed air cylinder with suitable reducing valves, or a portable compressor. A pressure regulating valve is indicated schematically at 11 to provide a constant working pressure of, say, 80 psig.

A main shut-off valve 12 is provided in the inlet duct 10, after which the duct is divided into separate legs 13 and 14. An operating pressure gauge 15 is provided in the leg 14.

The leg 13 is connected to the top of a pressurised liquid reservoir 16 adapted to contain a foamable aqueous chemical formulation consisting essentially of a foaming agent and the fluorochemical to be applied to the fabric.

A pair of adjustable needle valves 17 are disposed respectively in the line 14 and in the continuation of line 13 after the reservoir 16. The pressurised liquid and the compressed air are fed through the needle valves 17 in controlled proportions which will determine the density and delivery rates of the product foam. The flow rates of the liquid and air are measured via respective visual flow meters 18 after which the liquid and air mixture is fed via an injector 19, with a non-return valve 20 in the air line, through a valve 21 at the base of a tortuous path matrix in the form of a bead column 22.

The column 22 consists of a vertical tube approximately 500mm in height and 25mm in diameter.

The column is filled with glass beads approximately 2mm in diameter, through which the casual mixture of foamable liquid and air is forced upwards under pressure. The labyrinth of closely packed beads has the effect of breaking up the liquid flowing through it resulting in a considerable increase in the surface area per unit of mass. The fine droplets of liquid, mixed with the flow of air, undergo a phase inversion resulting in a fine textured foam which emerges from the top of the column.

A pressure gauge 23 upstream of the injector 19 measures the back pressure created by the resistance in the column 22. Adequate back pressure is essential for the satisfactory production of foam, and the size of beads as well as the dimensions of the column are selected to produce a back pressure during normal use within the range of 20 to 50 psig.

The foam issuing from the top of column 22 is fed via a flexible pipe 24 to an applicator head 25.

The head 25 defines a slot opening 32 in the region of 1Ocm long and about 0.8mm across. Thus, the foam issues from the slot 32 in the form of a thin sheet so that the head 25 may be drawn by hand across the surface of upholstery fabric thus impregnating the fabric with the foamed chemical formulation.

The wet pick-up achieved on the fabric can be adjusted by initially selecting the settings of valves 17 and thus the proportions of air-to-liquid fed to the injector 19, and by varying the rate at which the applicator head is drawn over the fabric. The latter is established by experience.

An off/off valve 26 fitted in the pipe 24 enables the supply of foam to the applicator head to be shut off when an operator trigger is released. If the foam supply is shut off for more than a few seconds, as for example when transferring from one workpiece to another, the resultant back pressure in the bead column 22 is adapted to actuate the valve 21 shutting off both the liquid and the air flow to the bead column which then remains on "standby" until the applicator trigger valve 26 is again opened whereupon the back pressure will reduce causing the valve 21 to open once again and continue the production of foam.

When the liquid reservoir 16 requires refilling, the main shut off valve 12 is closed in order to depressurise the entire system so that the reservoir may be opened and recharged with foamable chemical.

At the end of a processing sequence the system is depressurised by closing valve 12 so that the reservoir 16 may be emptied via a valve 27 to a drain outlet 28. Similarly, a further valve 29 in a line 30 connected to the base of bead column 22, may be opened to drain the column to an outlet 31. Subsequently, the reservoir 16 may be filled with clean water and valves 27 and 29 closed and valve 12 opened in order to pressurise the system and force clean water through the pipework, injectors, bead column and applicator head.

The foamable liquid to be contained in reservoir 16 is essentially a fluorocarbon formulation specially developed for this purpose. The formulation must be such that the contained surfactant or foaming agent must be capable of self-destruction or otherwise being rendered inactive during normal air drying at room temperature so that the fabric protection which relies on a high level of oil and water repellency, is ensured. Clearly, the presence of a permanent surfactant or wetting agent on the treated fabric would be extremely undesirable.

Furthermore, the foam stability must be adjusted such that the foam survives to the point of application to the fabric but thereafter collapses into the fabric very rapidly.

The apparatus is intended to be entirely portable having a maximum weight in the region of 30 kg, and its dimensions should be no greater than 0.5 cubic metres. The automatic foam cut-off feature of the applicator head is provided by a so-called "dead man's handle" so that the operator may leave the system unattended without concern.

The foam production within the bead column should establish expansion ratios as great as 1:50 or more, and preferably valves 17 should be preset during manufacture to provide the correct foam characteristics.

Claims

1. Apparatus for producing a foamed, for example, fluorocarbon protection medium for application to fabric surfaces, the apparatus comprising means for connection to a source of pressurised gas, a reservoir for containing an aqueous foamable liquid, a tortuous path matrix through which a mixture of the gas and the liquid are forced under superatmospheric pressure to generate therein a fine textured foam, an outlet duct from said matrix and an applicator head fed by said outlet duct and defining a restricted slot opening through which the foam may issue in a sheet-like form for direct application to the fabric to be treated.

2. Apparatus according to Claim 1, including means for supplying said pressurised gas and said aqueous foamable liquid simultaneously to said tortuous path matrix.

3. Apparatus according to Claim 2, wherein said simultaneous supply means comprises a pair of adjustable valves whereby the flow rates of the gas and liquid may be measured and adjusted.

4. Apparatus according to any preceding claim, wherein said tortuous path matrix comprises a tube adapted to be disposed vertically in use, and filled with glass beads to provide a labyrinth to break up liquid flowing through the tube such that fine droplets of liquid mixed with the flow of gas may undergo a phase inversion resulting in a fine textured foam which emerges from the top of the tube.

5. Apparatus according to any preceding claim including means to measure back-pressure created by resistance within the tortuous path matrix.

6. Apparatus according to Claim 4, wherein the vertical tube measures approximately 500mm in height and 25mm in diameter.

7. Apparatus according to Claim 4, wherein the size of the glass beads is approximately 2mm in diameter and the size of the vertical tube is selected in relation to the bead size so as to produce a back pressure during normal use within the range of 20-50 psig.

8. Apparatus according to any preceding claim wherein the applicator head defines a slot opening in the region of 10cm long and approximately 0.8mm across.

9. Apparatus according to any preceding claim including shut-off valves to enable the system to be de-pressurised for refilling said reservoir and/or for draining down the apparatus.

10. Apparatus according to any preceding claim including an on/off valve associated with said applicator head, whereby the supply of foam may be shut-off temporarily by an operator.

11. Apparatus according to any preceding claim including a valve adapted to be responsive to a buildup of back pressure in the tortuous path matrix, and adapted consequently to shut-off the liquid and gas flows to the latter until said back pressure is relieved.

12. Apparatus according to any preceding claim having an overall weight not greater than 30 kg. and dimensions of not greater than 0.5 cubic metres, thus to be entirely portable in use.

13. Apparatus according to any preceding claim wherein said tortuous path matrix is such as to provide an expansion ratio therein of 1:50.

14. Apparatus according to any preceding claim including visual flow meters to assist the operator in adjusting the relative flow rates of the liquid and gas to the tortuous path matrix.

15. Apparatus for producing a foamed, for example, flurocarbon protection medium for application to fabric surfaces, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing,