WO1994027738A1

WO1994027738A1 - Adhesive application system

Info

Publication number: WO1994027738A1
Application number: PCT/AU1994/000281
Authority: WO
Inventors: Donald A. Lymer; Angel Genoves
Original assignee: Tybar Engineering Pty Ltd
Priority date: 1993-05-28
Filing date: 1994-05-27
Publication date: 1994-12-08

Abstract

The invention relates to an adhesive application system for applying latex (64) to a secondary backing (52, 54, 74). The latex (64) is supplied to nozzles (62) and can be applied via direct application to backing (52) or indirectly via roller (50).

Description

ADHESIVE APPLICATION SYSTEM FIELD OF THE INVENTION The present invention relates to the application of adhesive to a continuous backing material and relates particularly, although not exclusively to, application of adhesive to the secondary backing material for manufacture of tufted carpet.

PRIOR ART Fig. 1 of the accompanying drawing shows a cross-sectional view of this method. In the manufacture of tufted carpets it is required to bond a secondary backing material (usually woven jute or polypropylene) to the tufted primary griege in order to attain the desired rigidity and adhesion necessary to produce a quality carpet. The method by which this is achieved involves passing the backing over a variable speed lick roller which is revolving in a bath of latex compound. Fig. 1 shows a bath 10 filled with latex or other suitable adhesive 12 and having a variable speed lick roller 14 rotating in bath 10. A secondary backing 16 is pulled from a roll or stack (not shown) and guided by rollers 18, 20 and 22. The latex 12 is transferred to the backing 16 in a random pattern and the roller 14 is wiped clean with the excess latex not taken up by the backing 16 falling back into bath 10 as shown at 24. The amount of latex transferred to the backing (called coat weight) is a function of the viscosity of the latex compound and the relative speed between the lick roller 14 and the backing 16. As the level in bath 10 decreases more latex is pumped in, either by the control of level detectors (not shown) or, more usually, by manually operating a pump 26. To attempt to ensure that fresh latex is presented to roller 14, and to stop crusting on the surface, it is necessary to agitate the bath. Agitation is typically achieved by a reciprocally moveable stirrer 28 which may be attached to a chain drive 30.

When using jute as the secondary backing, contamination of bath 10 occurs from fibres becoming dislodged from backing 16 and entering the bath with the excess latex, thus increasing its viscosity. This is partially eliminated by providing a beater 32 to raise lint and a vacuum extractor 34 to remove it. The whole system must be cleaned on a regular basis, as bath 10 eventually becomes contaminated with fibres and hardened latex. Cleaning periods will vary depending on production levels but would typically be once every one or two weeks with the latex remaining in the bath being discarded. Stops in production for extended periods (overnight or weekends) necessitates the stirrer 28 and the lick roller 14 to continually operate in order to prevent the latex from hardening. The achievement of accurate and consistent coat weights using this method is impossible without expensive indirect methods of measuring after application. Consequently quality will vary as conditions change and the tendency is to act on the safe side and over apply, thus wasting latex. OBJECT OF THE INVENTION

It is an object of the present invention to simplify the prior art system and to use less latex.

A further object of the invention is to provide a system which accurately controls the amount of adhesive applied and is cleaner than the prior art systems.

SUMMARY OF THE INVENTION With these objects in view the present invention provides an adhesive application system for supplying adhesive to a backing material, said system including means to continuously move said backing material in contact with a rota table transfer roller, a plurality of movable adhesive supply nozzles located above said transfer roller, said nozzles suppling adhesive either directly to said backing material on said transfer roller or to said backing material via said transfer roller.

Preferably said nozzles are reciprocally moveable in a predetermined manner across the width of said backing material. In a preferred embodiment at least two sets of aligned nozzles are provided which are independently moveable. In one preferred embodiment said backing material contacts said transfer roller below the centre of said transfer roller whereby adhesive is placed on said backing material by rotation of said transfer roller carrying said adhesive.

In a further embodiment a non-rotatable roller or guide is located parallel with said transfer roller to form a nip between said transfer roller and said non-rotatable roller or guide and said nip forming an outlet for adhesive supplied to said nip from said nozzles.

DESCRIPTION OF THE DRAWING A specific non-limitative preferred embodiment of an adhesive application system made in accordance with the invention will now be described with reference to the accompanying drawing, in which:-

Fig. 1 is a cross-sectional view of the prior art system previously described;

Fig. 2 is a cross-sectional view of an adhesive application system made in accordance with the present invention; and

Fig. 3 is a similar view to that of Fig. 2 of a further embodiment of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS In Fig. 2 there is shown a variable speed transfer roller 50 which has a secondary backing 52 located on the top of roller 50 or, as shown in broken lines, has a secondary backing 54 located under roller 50. The secondary backings 52, 54 are in contact with roller 50. Adhesive, preferably a latex compound, is pumped into a manifold 56 and has a plurality of outlets connecting to a nozzle board 58 through flexible tubing 60. Nozzles 62 allow the latex 64 to be applied to either backing material 52 or to roller 50 depending on contact of secondary backing with roller 50.

Nozzles 62 are equispaced across nozzle board 58 to allow coverage across the width of backing material 52, 54 in a reciprocal movement.

Nozzle board 58 has a variable speed and pitch oscillator (not shown) and is positioned directly over the variable speed roller 50.

This arrangement provides two options for applying latex to the backing. The first option is to apply the latex in a similar pattern to the traditional method. The backing 54 is threaded underneath the transfer roller 50 and latex applied onto roller 50 which transfers it to backing 54. With this option the oscillations are set to produce an even coat onto roller 50. All the latex applied to roller 50 is transferred to backing 54 thus wiping the roller surface clean. The second option is to apply latex directly to backing 52 by threading up over roller 50. This produces a repeatable pattern the most simple being a sine wave but others could be designed by varying the method of oscillation and/or other techniques. One such technique would be to have a plurality of independently controlled nozzle boards arranged in parallel. The second option is the preferred method because there is no wastage of latex, as occurs in the numerous small specks typical of the random application. Such specks do not contribute significantly to the bond strength. The adhesion results can be maximized by designing the pattern of latex placement and a geometric pattern is more aesthetically pleasing than the random pattern. This new method lends itself to using a foamed latex compound. Air is added to the compound to increase its viscosity and volume, making handling easier so that smaller quantities of compound can be applied evenly. Thus target adhesion figures can be achieved using less latex.

With this method of application there is total control over the coat weight as latex flow rates can be monitored by flow meters and matched to line speed, thus ensuring consistency and economical control over usage of latex solving two of the biggest problems of the conventional method.

To prevent latex from solidifying in the tubes 60 and nozzles 62, and to facilitate any stopping and starting, a mechanism (not shown) is provided by which the nozzle ends can be capped to exclude air from the latex and the mechanism flushed with water in order to keep the system clean.

The advantages of the new system are numerous. The system is cleaner as there is no bath or lick roller. The omission of the bath prevents contamination of the latex by lint. As there is no bath there is no stirrer required. The lack of contamination of the latex does not require the use of a beater or lint extractor. A consistent result is always obtained with an accurate control over the coat weight being available. There is less downtime for this system and a reduction in latex usage. The embodiment shown in Fig. 3 is a variation of the embodiment shown in Fig. 2. To avoid repetition of description similar integers will be referenced identically to those shown in Fig. 2. In this embodiment a non-rotatable roller 66 is mounted parallel with transfer roller 50 forming a nip or small gap 68.

Roller 66 may be any shape and may be a simple guide plate. Latex 64 from nozzles 62 forms a small reservoir 70 of latex at nip 68. The reservoir is retained within nip 68 by the curve of the rollers and by end stops (not shown) shaped to the roller profile. Roller 66 is adjustable, as indicated, by arrows 72 and speed to vary latex flow and to allow contact with roller 50 to shut off latex flow when the system is halted.

In use, backing material 74 contacts transfer roller 50 below nip 68. Latex 64 flows from reservoir 70 and is transferred to roller 50 from nip 68. Latex is applied to backing material 74 from transfer roller 50.

It will be understood that many modifications may be made in details of design and/or construction without departing from the ambit of the invention, the nature of which is to be ascertained from the foregoing description and appended claims.

Claims

1. An adhesive application system for supplying adhesive to a backing material, said system including means to continuously move said backing material in contact with a rotatable transfer roller, a plurality of movable adhesive supply nozzles located above said transfer roller, said nozzles suppling adhesive either directly to said backing material on said transfer roller or to said backing material via said transfer roller.

2. The adhesive application system as claimed in claim 1, wherein said nozzles are reciprocally moveable in a predetermined manner across the width of said backing material.

3. The adhesive application system as claimed in claim 1 or 2, wherein least two sets of aligned nozzles are provided which are independently moveable.

4. The adhesive application system as claimed in claim 1, wherein said backing material contacts said transfer roller below the centre of said transfer roller whereby adhesive is placed on said backing material by rotation of said transfer roller carrying said adhesive.

5. The adhesive application system as claimed in claim 1, wherein a non-rotatable roller or guide is located parallel with said transfer roller to form a nip between said transfer roller and said non-rotatable roller or guide and said nip forming an outlet for adhesive supplied to said nip from said nozzles.

6. The adhesive application system as claimed in claim 5, wherein said backing material contacts said transfer roller below said nip whereby adhesive is placed on said backing material by rotation of said transfer roller carrying adhesive from said nip.