WO1990006340A1

WO1990006340A1 - Method and apparatus for impregnation of foam material and products resulting therefrom

Info

Publication number: WO1990006340A1
Application number: PCT/GB1989/001453
Authority: WO
Inventors: Peter Jeffrey
Original assignee: Nucleus Enterprise Limited
Priority date: 1988-12-09
Filing date: 1989-12-05
Publication date: 1990-06-14
Also published as: GB8828804D0; EP0447481A1; GB2225738A; ZA899411B; ES2024082A6; GB8927476D0; AU4741490A; CA2004927A1

Abstract

A method and apparatus for the economical production of such like as a cleaning or scouring product based on application of a substance to a foam material in which the substance is appllied to the material whilst it is compressed (between rollers B, C) with application being first to one of the rollers and then transferred to the material, and thereafter cured/dryed. The resulting foam material having a surface which is uneven and presenting recesses at incomplete cell-sites open at that surface with the application and penetration of said substance or a material borne by said substance causing the surface to have the desired cleaning or scouring properties.

Description

METHOD AND APPARATUS FOR IMPREGNATION OF FOAM MATERIAL AND PRODUCTS RESULTING THEREFROM

DESCRIPTION

The present invention relates to the modification of compressible materials, preferably foamed synthetic plastics material, but not limited to such, called "foam material" herein, which modification involves coating and/or impregnating, hereinafter referred to as "impregnation coating", said foam material with at least one substance compatible therewith. More especially the invention relates to method and/or apparatus for impregnation coating said foam material and to useful products resulting therefrom including manufacture of cleaning, scouring etc. products. In relation to foam material we are particularly concerned with open cell type having sponge-like properties.

Hitherto, we are aware of two distinct approaches to making such products. One involves securing a of body of foam material a thinner sheet of other material having desired cleaning, scouring, etc. properties with adherence between the two generally determined by contact area as related to relative cell sizes. The other is to apply to a body of foam material an intentionally distinct layer of spreadable material having desired cleaning, scouring etc. properties which distinct layer tends to seal the surface of the foam material whether applied by blade, roller or spray.

It is one aim of this invention to provide another and advantageous approach to making such products and in achieving that aim there has evolved method and apparatus for making products for scouring, cleaning and with other useful characteristics.

In. arriving at this invention, it has been noted that sheets of foam material from which the aforesaid bodies are cut are generally characterised by having an uneven surface, essentially with varying sizes and depths of depressions corresponding to cell-like voids in the foas material. That is true when the foam material is of at least partially open-cell type or normally wholly closed/cell type, at least where sheets of the latter are cut from a block, as is usual. For the secured-on sheet or spread-layer types of products referred to above, the former requires covering of and securing to the aforementioned uneven surface and the latter tends to fill the depressions, in both case relying only on the applied sheet or layer to afford the desired cleaning, scouring etc. properties of itself at its own exposed surface. It is a particular aim of one aspect of this invention to make direct use of the structure of the foam material , such as the inevitable uneveness of the surfaces of bodies of foam material, in attaining desired cleaning, scouring etc. properties by modification of that structure.

According to one aspect of this invention then, a surface of a body of foam material , which surface is uneven in presenting recesses at incomplete cell-sites open at that surface, has applied thereto, and is penetrated at least into said recesses by, a substance compatible with the foam material .in the sense that such substance does not readily strip off subsequently, and which substance, or material borne by such substance, causes said surface to have desired scouring, cleaning etc. properties with its said recesses continuing to contribute uneveness to said surface after application of said substance.

It will be apparent from the above then that said substance incompletely fills the cell sites of the foam material. At least at said surface and preferably where there is penetration of the open cell sites beyond said surface, similar internal coating of the cell structure but without filling the voids of the cell structure occurs. The characteristics of the resulting product and hence the application is determined by the nature of the substance applied to the foam material. That material may cure to vary the hardness of the foam material, may contain abrasion modifiers, may itself be a foaming material (preferably foaming without filling the cells within the foam material) and/or being of a hydrophilic nature. In applying the substance to the foam material control can be exercised over the application to regulate the depth of the internal coating by degree of penetration from said surface, as well as the thickness of the internal coating to the open cell surface. Penetration may be from one layer of cells upto one hundred percent penetration of foam material thickness.

One embodiment provides a body of open cell foam material for use in scouring, cleaning etc. in which said substances, comprises such as a prepolymer giving desired hardness with or without the addition of further such abrasion modifiers.

In another embodiment, said substances comprise a foaming material with or without modification to give enhanced hydrophilic properties. Any substance which starts off as liquid and which cures to a hard solid will suffice for envisaged scouring, cleaning, abrasive applications. Suitable said subtance is an adhesive or binder, in connection with which a substance successful in trials is a prepolymer of moisture-activated type which enables controlled impregnation coating prior to curing. Other suitable binders are of heat curing type and/or of moisture activated and solvent-retarded type which is applicable as liquid that will cure after the solvent has evaporated, although the latter type is less preferred.

A suitable way of securing penentration of said surface of the body of foam material is with compression of that material at least as it meets said substance, thereby presenting interior surfaces of its depressions to that substance and assisting that said substance in being drawn into the depressions as the body of foam material relaxes from its said compression, i.e. essentially mechanically.

Assist materials for particular purposes, say abrasive particles for scouring, (such as aluminium oxide) or polishing beads for non-scratch cleaning or polishing, (such as polymer or waxy beads) may be as inclusions in said substance, preferably as a thoroughly mixed distribution thereof through that substance rather than as a layer of or underlying said substance. Surprisingly, it has been found that assist materials when constituted as discrete particles in the substance to be ^' applied do not penetrate the foam material in the same way as the substance, but accumulate at the first layers, thus maximising their effect just where required and minimising actual amount to be added to the substance. Assist materials can also include cleaning agents, fragrances etc such as a "preload" into said substances.. →

The structure has the advantage of providing a flexible mounting for the grit and furthermore, because the open cell structure is not destroyed, hydraulic action can be utilised to give "self cleaning" properties to the abrasive material be it for industrial or domestic applications.

An adhesive or binder can, of itself and alone, achieve a considerable effective hardening of the surface concerned, including a depth therebelow corresponding to penetration, and can thus produce useful cleaning, scouring etc. products. However, inclusion of specific assist materials is likely to be employed for easy attainment of specified particular desired operating properties. Progressive strengthening of the foam material is achieved (seemingly with a greater dissipation of energy into the material enabling the material to sustain greater applied forces than might otherwise be the case). More importantly though, this strengthening permits the use

of a lower density foam for equivalent mechanical performace after modification using a prepolymer, the ratio of polyol to isocyanate consituting the prepolymer can be varied to readily produce desired hardness.

The physical action of separating the foam surface, particularly after relaxation of compression at least adjacent thereto, from a carrier for said substance is found to have a beneficial effect in concentrating hardening of the surface and/or location of assist materials at high points of the surface.

The above description has made mention of particular application to making cleaning, scouring products with reference to creating a surface with the desired degree of abrasiveness.

Accordingly, the invention provides a method of impregnation coating foam material with a desired substance comprising feeding the foam material to an application station, applying the ^'substance to the material, preferably whilst compressing the material, releasing the material from compression and passing the material through a curing and/or drying station ready for processing into suitable sized product. The invention also provides apparatus for impregnation coating foam material with a desired substance comprising a compression station, and means for applying the substance to the foam material whilst compressed.

Economic and effective manufacture is envisaged by way of a pair of rollers which are adjustable relative to one another to control compression of the foam sheet, and preferably one carries said substance as a coating, say so that the foam^" sheet and the substance meet at a nip between the respective rollers whereat the foam sheet is compressed. The degree of compression is adjustable, as is the -quantity of substance applied to the foam material. However, any manufacturing method may be used that produces satisfactory results, for example roller or other foam sheet translation means located or movable to cause temporary compression thereof in a tray or other container for said substance, and at least relaxation thereof at removal from the tray or other container, if not pulling of the foam material away therefrom at that time. Alternatively of course, foam material, may be successively "stamped" into or onto said substance with compression.

The desired substance is applied to the surface of that roller and an advantageous result is obtained if a band of the substance to be applied to the material is applied to one roller through a nozzle, with the thickness of the substance controlled by a gate, preferably to be applied to an upper surface of the material. By this means any of the substance remaining on the roller after application to the material can be doctored off before curing on the roller and thereby avoiding build up of material on the application roller. The rollers are conveniently orientated with their axes horizontal, and preferably one above the other for the foam material to pass through aligned in a generally horizontal plane.

Alternatively the rollers may be dispaced side by side for emergence of foam material therefrom vertically, with input aligned therewith or or angled relative thereto. Vertical orientation is envisaged but not limited to the case where an impregation coating of the same or different substances is to be applied to both faces of the of foam material, i.e. each rollers serves as an application roller and have associated therewith suitable apparatus for coating the roller with the substance to be applied.

After application of the substance, the foam material is passed to a drying/curing station. Depending on the nature of the substance being applied the drying stage may utilise application of dry heat or moist, such as steam or a .water mist followed by dry heat. An infeed conveyor mechanism may be used for introducing the foam material, in suitable lengths, into the compression and application station, and cut lengths of material may be used.

Desired additions to the substance being applied can be easily introduced.

The present invention will now be described further by way of example only with reference to the accompanying drawings; in which:

Figure 1 is a schematic side view of apparatus for impregnation coating of "foam material"; according to one embodiment;

Figure la is a schematic side view of apparatus for impregnation coating according to a preferred embodiment; Figure lb is a detail of the blade applicator of Figure la;

Figure 2a illustrates in section what cut foam looks like, whilst Figure 2b is a diagrammatic representation of that foam in section; and Figures 3a and 3b illustrate that foam diagmatically after impregnation coating, that of Figure 3b showing incorporation of discrete assist materials.

Referring firstly to the drawing of Figure 1, here there is shown apparatus comprising an infeed conveyor, shown partially at A as comprising endless bands 1, 3 entrained around end rollers 5, 7 presenting mutually adjacent faces for gripping and transporting foam material horizontally in sheet form with length and width greater than its depth. The foam material is presented to opposed parallel rollers B, C which are mounted on a suitable framework for rotational movement as shown by arrows 9 and for movement towards and away from one another as shown by arrow 10, actually shown for the uppermost roller to be adjustably mounted to control the space/nip between the two rollers. The rollers B and C are both rotationally driven at the same speed from a suitable drive motor by way of a suitable transmission.

Roller C dips into a bath E which is filled with the substance to be applied to the foam material. That substance is conveniently fed from a mixing tank F provided with stirring means illustrated diagrammatically by way of rotor 15. Material picked up by the surface of the roller C as at 17 is doctored to the required quantity as at 19 by an adjustable doctor blade D.

Also illustrated at G is a curing chamber at which a water mist or steam equipment is established, if only momentarily, to ensure initiation of

then followed by application of dry heat to dry off the foam material. The foam material is reorientated to pass upwardly through the curing/drying chamber such as by turning through 90 degrees either as it comes out of the compression roller (as illustrated) or some way afterwards by turning round a separate roller (not illustrated) .

After passing through the- curing/drying chamber the foam material passes to a cutting station to be cut into desired product sizes and then packaged as required.

Referring now to the drawing of Figure la, here there is shown preferred apparatus comprising an infeed conveyor, shown partially at A as comprising endless bands 1, 3 entrained around end rollers 5, 7 presenting mutually adjacent faces for gripping and transporting foam material horizontally in cut sheet form with its length and usually its width greater than its depth. The foam material is presented to opposed parallel rollers B, C which are mounted on a suitable framework for rotational movement as shown by arrows 9 and for movement towards and away from one another as shown by arrow 10, actually preferred as shown for the lowermost roller to be adjustably mounted to control the space/nip between the two rollers. The rollers B and C are both rotationally driven at the same speed from a suitable drive motor by way of a suitable transmission. Roller C has a band of the substance to be applied to the material applied to it through fan nozzle F. That substance is conveniently fed from a mixing tank H provided with stirring means illustrated diagram atically by way of rotor 14 and a low pressure dry nitrogen feed is provided to replace the volume of the substance discharged to prevent atmospheric moisture coming into contact with the remaining substance. The band is of a precise width commensurate with the width of material being used at the time. The thickness of the band is controlled by a gate 11 (illustrated in further detail in Figure 1b) which is pivoted about point 13 and which may be moved as indicated by arrows 12. Adjusting means such as a screw device, is employed to set the position of the gate and thereby the thickness of substance- The gate may also be closed completely so as to stop the flow of the substance. A valve arrangement G restricts the flow of the substance from mixing tank H so as to prevent the reduction in head pressure as the substance is used from effecting the discharge rate at nozzle F. This delivery arrangement eliminates contact with atmospheric moisture by the substance until such time as it is immediately to be applied to the material, so eliminating premature curing of the substance and making cleaning procedures very simple and easy. A scraper D is provided to remove from the roller C any small quantities of the substance which have not been transferred to the material. This scrap substance is disposited in tray E so as to prevent its falling onto the coated material.

In practice the mixing tank H is the drum in which the substance is supplied. The delivery tube L connecting the mixing tank H to the fan nozzle F is a disposable plastic tube. The valve arrangement G is a constricting clamp which partially or fully flattens the tube L. The scraper D is a disposable steel blade. The tray E is lined with paper. Thus the only parts requiring to be cleaned after a production run are the roller C which is easily wiped clean with a εolent soaked rag, the fan nozzle F which may be immersed in solvent and the εtrirrer 14 which may be attached to a drum of solvent and activated for a short time to remove the substance left on it. Immediately after impregnation coating the strip of coated material is sprayed with low pressure steam (hot water vapour) at J to activate the curing of the substance. The preferred substance is a highly catalysed moisture cure prepolymer polyurethane which cross links and through cures quickly in the presence of water molecules and heat.

The foam strip then passes into a curing/drying chamber K where radiant heat is applied to the coated surface of the material. An endless conveyor 120 extending through the curing/drying station and carried on pully means 122 driven from a suitable drive motor (not illustrated) may be employed to transport the material. After passing through the curing/drying chamber the foam material passes to a cutting station to be cut into desired product sizes and then packaged as required.

The foam material with which we are concerned is of open-cell type - typically open-cell foam synthetic plastics, although other material structures having interconnecting spaces and which are compressible could be used with the process.

Referring now to Figures 2a, b, 3a and 3b, Figure 2a shows the cell structure 20 of a typical open-cell foam material in its natural cured form before treatment (cut face at x) . Figure 2b shows a diagrammatic form of the structure in view of the di iculty of showing intercommunication of cells, although this is to be understood to be the case where the cells contact one another at some if not all contact points.

The cell structure 20 is compressed at the point of application of the coating substance. This is advantageous in controlling the quantity of material taken up by the foam material, and the penetration of the substance into the foam material. Adjustment of one or more of the amount of compression, the doctor gap, the viscosity and the surface tension and the structure of the foam will serve to vary the penetration. Figure 3a shows diagrammatically how the substance 22 coats the interior spaces of the cell structure 20 but without filling those spaces so that intercommunication is not blocked off, also the free edges as at 23. That has advantages in relation to products utilising such as hydraulic communication. The illustration shows penetration through the cell layers with a general reduction in coating thickness with increasing penetration. This is advantageous from the point of view of energy dissipation considerations. For example, one envisaged product comprises open-cell foam material to which a εtregthening resin is applied as an impregnation coating for use as a

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scourer/abrasive. The open cell structure permits flushing of the foam cell structure to remove accumulateά debris from the open cell surface. The structure would look like that represented diagrammatically in Figure 3s- The application of the coating substances to the foam material when it is compressed acts to avoid complete filling of the cell structure as the amount of material admitted to the cells is less than that required to fill once the foam material is allowed to relax.

Another envisaged embodiment has friction assist materials 25 incorporated in the coating substance 22, and that has been found to accumulate at the surface as represented by the large number of such sites 25 near the surface. That maximises effectiveness of the abrasive without requiring a separate application stage. Such a structure is illustrated in a representative way with reference to Figure 3b. The binder penetrates further than the friction assist materials 25.

Claims

1. A method of impregnation coating foam material with a desired substance comprising feeding the foam material to an application station (B, C), applying the substance to the material whilst compressing the material, releasing the material from compression and passing the material through a curing and/or drying station ready for processing into suitable sized products.

2. A method of impregnation coating as claimed in claim 1 comprising compressing the material by passage between opposed rollers and in which the substance to be applied is first applied to one of the rollers and transferred to the material by contact therebetween.

3. A method of impregnation coating foam material as claimed in claims 1 or 2 in which the depth of impregnation coating is controlled by varying one or more of:- a) the amount of compression; b) the quantity of the substance applied; c) the viscosity of the substance; d) the surface tension of the substance.

4. A method as claimed in claim 3 in which the amount of compression is varied by adjusting the distance between the opposed rollers.

5. Apparatus for impregnation coating foam material with a desired substance comprising a compression station (B, C) for compressing the material on passage there past and means for applying the substance to the foam material whilst compressed, and a curing/drying station (K).

6. Apparatus as claimed in claim 5 in which the compression station comprises opposed rollers (B, C) between which the material passes.

7. Apparatus as claimed in claims 5 or 6 in which the means for applying the substance comprises one of the rollers.

8. Apparatus as claimed in claim 7 in which the susbstance is deposited onto one of said rollers by means of a dispensing head having means (F) controlling the thickness and width of the substance.

9. Apparatus as claimed in any one of claims 5 to 8 further comprising means (J) applying steam or hot water vapour to the material after application of said substance.

10. A foam material having a surface which is uneven in presenting recesses at incomplete cell-sites open at that surface, and which has applied thereto and is penetrated at least into said recesses by a substance compatable with the foam material in the sense that it does not readily strip off subsequently, and which substance, or material bourne by said substance, causes said surface to have desired scouring, cleaning etc properties, its said recesses continuing to contribute uneveness to said surface after application of said substance.

11. A foam material as claimed in claim 10 having an open cell structure which is substantially maintained even after application and penetration of said substance.