US3449156A

US3449156A - Apparatus for and a method of saturating non-woven fabrics

Info

Publication number: US3449156A
Application number: US383676A
Authority: US
Inventors: Peter Brown
Original assignee: Revertex Ltd
Current assignee: Revertex Ltd
Priority date: 1963-07-18
Filing date: 1964-07-20
Publication date: 1969-06-10
Anticipated expiration: 1986-06-10
Also published as: FR1401083A; GB1026304A

Description

June 10, 1969 P. BROWN 3,449,156

APPARATUS FOR AND A METHOD OF SATURATING NON-WOVEN FABRICS Filed July 20, 1964 Sheet of 3 /N\/ENTOR PETER BROWN MM l m w,

P. BROWN 3,449,156 APPARATUS FOR AND A METHOD OF SATURATING NON-WOVEN FABRICS June 10, 1969 Filed July 20, 1964 Z of5 Sheet IN-VENTOR PETER BROWN MAW/W W June 10, 1969 P. BROWN 3,449,156

APPARATUS FOR AND A METHOD OF SATURATING NON-WOVEN FABRICS Filed July 20, 1964 I Sheet ,3 of 3 17 \Z V FIG.7

INVENTOR PETER BROWN United States Patent US. Cl. 117-102 6 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for carrying out the method for impregnating non-woven fibrous stock which comprises conveying a preformed sheet of non-woven fibrous stock to a bath of a bonding agent, passing the sheet through said bath, moving the sheet between a nip of a pair of squeeze rollers, at least one of which has a resiliently deformable peripheral layer and projection means made of material harder than said layer, e.g., a plurality of metallic projections, said means being so arranged on the peripheral layer that improved expression of excess binder and improved release of the stock material are obtained, and subsequently drying the sheet.

This invention relates to apparatus for and a method of impregnating fibrous webs to form non-woven fabrics and similar non-woven materials. Non-woven fabrics are made without the many processes of spinning and Weaving by bonding fibres together to form a fabric. A fibrous web is given substance through the application of a bonding agent. There are several methods of applying the bonding agent such as saturation or spraying but this invention is particularly concerned with the most commonly used method that of impregnation of a web of fibres with the bonding agent and the subsequent expression of the bonding agent. Such bonding agents are usually, but not necessarily, aqueous dispersions or latices of resinous or elastomeric polymers.

Apparatus for the impregnation of webs vary but in general the loose web of fibres is fed on a conveyor until it is sandwiched between two stainless steel screens of woven wire which convey the web through the impregnation bath. Since impregnated webs are sometimes liable to split and distort if they are in direct contact with rollers the mesh carriers also pass through the nip of squeeze rollers between which the web passes.

The surface covering of the squeeze rollers is of a fairly soft nature to assist expression of excess binder from the impregnated web.

Stainless steel screens have a high initial and replacement cost and the labour costs involved for maintenance to ensure trouble free production are also high. Furthermore, wire mesh can distort in use and thus reduce its effective width. It is necessary to remove, clean and replace the screens from time to time and any dried bonding agent left on the screens has to be removed for example by burning with the flame from a blow lamp which burning is time consuming.

Moreover, the use of screens can result in insufiicient wetting of the fibres at production speeds and may necessitate the provision of a guiding mechanism so that the screens will not track in directions transverse to theiir direction of movement.

Moreover the bonding agent is retained in the screen interstices while passing through the squeeze rollers with the result that the best possible expression is not obtained.

It is an object of the present invention to overcome the above disadvantages and dispense wtih screens altogether.

According to the present invention there is provided a squeeze roller for use in combination with another roller in the expression of fluid from a fibrous material comprising a peripheral layer of a resiliently deformable material and, on the deformablle material, projections of a material which is harder than the deformable material, the arrangement being such that the projections will sink into the deformable material under pressure at the nip between a pair of rollers.

Preferably the resiliently deformable material is a natural or synthetic rubber and the material which is harder than the deformable material is metal.

Conveniently the material which is harder than the deformable material is wire which is wound spirally round the deformable material, although the material could be in the form of a mesh or in the form of a series of discrete inserts, such as pegs, studs or discs.

The deformable material may be mounted on a lower substrate which is harder than the deformable material. Furthermore, both the rollers of a pair of squeeze rollers may be as above described.

According to another aspect of the present invention there is provided a method of impregnating fibrous stock comprising the steps of conveying a preformed sheet of fibres to a bath of a bonding agent, passing the sheet through the bonding agent, moving the sheet between the nip of a pair of squeeze rollers, at least one of which is as above described and subsequently drying the sheet.

Preferably the sheet is passed between the nip of at least one pair of rollers whilst being passed through the bonding agent. This ensures eflicient impregnation, particularly in cases where the sheet is comparatively thick, although where the sheet is compartively thin mere immersion of the sheet in the bonding agent is sufi'icient.

However, it is possible to effect impregnation by transfer of the bonding agent from a roller which dips into the bonding agent during its rotation:

According to yet another aspect of the present invention there is provided apparatus for impregnating fibrous stock comprising a bath adapted to contain a bonding agent, means for feeding the fibrous stock through bonding agent in the bath and to a pair of squeeze rollers positioned so that the nip between them is above the level of the bonding agent in the bath, at least one squeeze roller being as above described.

Preferably the means for feeding the fibrous stock through any bondng agent in the bath includes at least one pair of impregnation rollers of which the nip between them is beneath the level of any bonding agent in the bath.

Conveniently the squeeze rollers comprise a first and second roller and the impregnation rollers comprise said first roller and a third roller, at least the first roller being of the type above described.

Alternatively the apparatus may comprise two baths adapted to contain the bonding agent and in which the squeeze rollers are positioned so as to depend into any bonding agent within their respective baths and said means for feeding the fibrous stock feeds the stock directly to the nip between the squeeze rollers.

In order that the invention may be more clearly understood reference is made to the accompanying drawings, which illustrate, by way of example, various embodiments thereof and in which:

FIGURE 1 is a side view in section of one embodiment of impregnating apparatus;

FIGURE 2 is a perspective view of one of the rollers shown in FIGURE 1;

FIGURE 3 is a side view in section of the roller shown in FIGURE 2;

FIGURE 4 is a perspective view of another embodiment of roller;

FIGURE 5 is a side view, partly in section, of yet another embodiment of roller;

FIGURE 6 is a side view in section of another embodiment of impregnating apparatus; and

FIGURE 7 is a side view in section of yet another embodiment of impregnating apparatus.

Referring to FIGURE 1 an impregnation bath containing a bonding agent 2 has immersed therein a first roller 3 having a surface covered with wire as hereinafter described with reference to FIGURES 2 and 3, and also four cooperating secondary rollers 4 immersed within the bonding agent and butting the first roller. Also butting the first roller at opposite sides are two rollers, one of which (the feed roller 5) will be so positioned as to readily receive a sheet or web of fibres and pass it between the first roller 3 and the secondary rollers 4, the other (the squeeze roller 6) will together with the first roller 3 form a pair of squeeze rollers.

Referring to FIGURES 2 and 3, the roller 3 comprises a substrate 7 carried on a spindle 8. The substrate is rubber of 40 Shore hardness and is covered with a winding of stainless steel wire 9.

Instead of being wound spirally the wire 9 could be woven into a mesh and then applied as a covering to the substrate 7. Alternatively the rollers, hereinafter described with reference to FIGURE 4 or 5, could be employed.

The rollers in contact with the first roller 3 may also be covered with wire.

A conveyor may be provided for feeding the web between the first roller 3 and the feed roller 5. The squeeze rollers may be relatively movable so that the pressure applied between them may be controlled.

In operation a web of fibres to be impregnated is fed into the impregnation bath of bonding agent 2 and carried around the first roller 3 by means of the secondary rollers 4 in contact with it. The padding action obtained in this way ensures rapid Wetting of the web fibres. The impregnated web then passes between the nip of the squeeze rollers where the pressure will force the wire 9 into the soft substrate 7 of the roller(s). In the nip, therefore, there should be an almost plain surface which will permit good expression of excess binder. On leaving the nip the resilient substrate 7 will spring the wire 9 back to its former position carrying the fibres with it, thus allowing the web to be carried away for further processing without adhering to the squeeze rollers and hence avoiding splitting or distortion.

Referring to FIGURE 4 there is shown another embodiment of roller which comprises a soft resilient peripheral substrate 7a and a harder under substrate 7b carried on a spindle 8. A number of inserts 10 are held by the soft resilient substrate 7a and project outwardly therefrom in such a manner that when pressure is applied to the roller, as in the nip between the squeeze rollers 3 and 6 of FIGURE 1, the inserts are forced into the substrate 7a. However, in a manner similar to the wire 9 of the roller shown in FIGURES 2 and 3, the inserts spring back to their initial positions on leaving the nip.

The inserts can be in the form of studs, pegs or discs.

Referring to FIGURE 5 there is shown another embodiment of roller which comprises a series of annular rubber discs 70 which are formed with two cut out portions to receive metal inserts 10a. The discs are displaced at 90 to their adjacent discs and thereby form a roller having four inserts spaced at ninety degrees to each other for each pair of discs.

Naturally there are a variety of materials which may be used for the resilient substrate and its covering and in selecting them the physical properties and dimensions of the materials used and the size of the rollers should be considered.

By using as squeeze rollers at least one roller constructed in accordance with the invention the high expression of excess bonding agent associated with plain rollers is obtained whilst retaining release properties of wire mesh screens.

I have found that this invention provides improved impregnation of the web of fibres by virtue of the additional padding action within the bonding agent and also since the expression of excess bonding agent is improved, the web of fibres can be passed through the machine faster than hitherto and so increase the rate of production.

Referring to FIGURE 6, there is shown another embodiment of impregnating apparatus comprising a bath 11 containing a bonding agent 12 .and a first roller 13 which is partially immersed within the bonding agent. A feed roller 15 and a squeeze roller 16 also abut the first roller so as to hold the web of fibres or fibrous stock 14 against the first roller 13 as the stock passes through the apparatus in the direction of the arrow 17. The relative positions of the first roller 13 and the squeeze roller 16 can be varied to adjust the nip pressure indicated by arrows 18. The

rollers

13 and 16 are of the kind shown in FIGURES 2 and 3, FIGURE 4 or FIGURE 5.

In operation the fibrous stock 14 is fed over roller 15 until it reaches the nip between that roller and roller 13. It then follows round roller 13, passing through the bonding agent 12 until it reaches the nip between the squeeze rollers after which it passes over roller 16 as it is drawn away from the apparatus.

Referring to FIGURE 7, the apparatus therein shown comprises two baths 11a and 11b which contain bonding agent 12. Rollers 13a and 13b depend into their respeetive baths of bonding agent and are relatively movable so that the pressure indicated by arrows 18 at the nip between them can be varied. The rollers are of the kind shown in FIGURES 2 and 3, FIGURE 4 or FIG- URE 5.

In operation the fibrous stock 14 is passed upwardly between the rollers 13:: and 13b which themselves pick up sufiicient bonding agent to impregnate the stock at the nip between them. The impregnated stock is drawn away from the apparatus in the direction of arrow 17.

The embodiments of impregnating apparatus shown in FIGURES 6 and 7 are suitable for the impregnation of lightweight fibrous stock. However, with heavier stock it is advantageous to use additional rollers as in the embodiment shown in FIGURE 1.

Whilst this invention is primarily concerned with the formation of non-woven fabrics, the invention might well be useful in the paper industry.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A method for impregnating non-woven fibrous stock which comprises conveying a preformed sheet of nonwoven fibrous stock to a bath containing a bonding agent, passing the sheet through the bath, moving the sheet between a nip of a pair of squeeze rollers, at least one of which has a resiliently deformable peripheral layer and a plurality of projections made of material harder than said layer positioned on the peripheral layer, applying a pressure between the squeeze rollers which causes the projections to sink into said deformable peripheral layer thereby creating an almost plain surface on the one of said rollers at the nip between said rollers to effect improved expression of excess binder from said stock, the projections being of sufficient number to effect improved release of said fibrous stock upon return to their initial positions on said layer, and subsequently drying the impregnated sheet.

2. The method of claim 1 in which said nip is positioned within said bath and said projections are made of metal.

3. An apparatus for impregnating fibrous non-woven stock comprising a bath containing a bonding agent, means for feeding a non-woven fibrous stock through the bath, a pair of squeeze rollers for receiving the fibrous stock, at least one of said rollers having a resiliently deformable peripheral layer thereon and a plurality of projections made of a material harder than said layer positioned on said layer and means for receiving the fibrous stock from said squeeze rollers, said projections being so arranged on said layer that the pressure between the rollers causes the projections to sink into the deformable layer thereby creating an almost plain surface between said rollers whereby improved expression of excess binder is obtained and the projections being of sufficient number that, upon return to their initial positions on said layer, improved release of the fibrous stock from the layer is obtained.

4. The apparatus of claim 3 in which the nip between two squeeze rollers is arranged within said bath and the projections are made of metal.

5. An apparatus for impregnating non-woven fibrous stock comprising a bath containing a bonding agent, a first roller depending in said bath, a resiliently deformable peripheral layer on said roller and a plurality of metallic projections on said resiliently deformable peripheral layer, a second roller operatively associated with said first roller so that the nip therebetween is within said bath, a third roller operatively associated with the first roller so that the nip therebetween is outside the bath, means for feeding the fibrous stock to the nip between the first and second rollers and means for receiving the fibrous stock from the nip between the first and third rollers, said metallic projections being so arranged on said layer that the pressure between said first and second rollers causes the projections to sink into said layer thereby creating an almost plain surface on said first roller whereby improved expression of excess binder is obtained and the projections being of sufficient number that upon return to their positions on said layer an improved release of said fibrous stock is obtained.

6. An apparatus for impregnating non woven fibrous stock comprising a pair of squeeze rollers, a bonding agent bath associated with each of said squeeze rollers,

each of said squeeze rollers having a resiliently deformable peripheral layer and a plurality of metallic projections on said resiliently deformable layer, said squeeze rollers being positioned to depend into the associated baths and contacting each other to form a nip therebetween and means for feeding the fibrous stock to said nip and means for receiving the fibrous stock from said nip, the pressure exerted between the squeeze rollers causing the projections thereon to sink into said deformable layers thereby creating substantially plain surfaces of each of said rollers at the nip whereby improved expression of excess binder is obtained and the projections being of sufficient number that upon return to their positions on said layers, an improved release of said stock is obtained.

References Cited ALFRED L. LEAVITT, Primary Examiner.

CHARLES R. WILSON, Assistant Examiner.

US. Cl. X.R.