GB1572087A

GB1572087A - Production of polymeric foam

Info

Publication number: GB1572087A
Application number: GB4035876A
Authority: GB
Original assignee: VITA INTERNATIONAL Ltd
Current assignee: VITA INTERNATIONAL Ltd
Priority date: 1977-09-28
Filing date: 1977-09-28
Publication date: 1980-07-23

Description

(54) IMPROVEMENTS IN OR RELATING TO ThE PRODUCTION OF POLYMERIC FOAM (71) We, VITA INTERNATIONAL LIMITED, a British Company of Middleton, Manchester M24 2DB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention concerns the continuous production of polymeric foam, for example polyurethane foam.

In the well known process of continuously producing polymeric foam in the form of slabstock the foaming mixture is contained within a moving conveyor in the form of an open topped channel formed by supplying, for example, kraft paper from a plurality of rolls to the end of an open topped stationary trough down which the conveyor moves.

One of the aims of users of this well known process has been to obtain slabstock with a flat top, the object being to reduce the amount of material cut to waste when the slabstock is cut up to produce sheets of the foamed material.

Many different forms of equipment have been made to achieve the aim set out above and one of the more successful apparatuses has included a means for feeding foaming mix from a container at the end of the trough to the moving conveyor. In this apparatus the foaming mix has entered the conveyor by flowing over a weir.

The present invention is based upon the appreciation that it is possible to continuously produce slabstock having any predetermined cross-section.

More particularly the invention is based upon the appreciation that slabstock of substantially circular cross-section may be formed and by so doing provide a product from which can be produced sheets of foamed material (generally these sheets will be relatively thin) by a peeling process with minimal waste. Clearly to produce relatively thin sheets by peeling from slabstock which is substantially of square section is extremely wasteful since the slabstock has first to be cut to have a generally circular cross-section.

Thus according to the present invention there is provided an apparatus for continuously producing a polymeric foam block of pre-determined cross-section including an open-topped stationary former whose crosssection from a foam inlet position to its termination changes from slightly concave to the requisite cross-sectional shape, there being means for feeding flexible movable conveyor forming sheet material onto the former in such manner as to provide an initially open topped slightly concave conveyor onto which block forming material is, in use, directly deposited, the said conveyor thereafter being caused by the former to assume a substantially completely closed section in which section in use, foaming mixture reaches the maximum height to fill the conveyor and to assume the requisite cross-section.

Preferably the former changes from slightly concave form to substantially circular crosssection.

The invention will be described further by way of example only with reference to one practical form thereof and the accompanying drawings in which: Figure 1 illustrates diagrammatically part of an apparatus made in accordance with the -invention, Figures 1A to 1D are sections taken on the lines A-A, B-B, C-C and D-D of Figure 1 respectively, and Figure 2 is a diagrammatic plan view of the apparatus of Figure 1.

Although the following description relates to a complete apparatus for the production of polymeric foam in substantially circular section, it is also possible for the present invention to be adapted to fit existing apparatus for the continuous production of polymeric foam. In the following description those parts of an apparatus for continuously producing polymeric foam that are already shown will not be described in detail.

A convenient form of known apparatus for use in conjunction with the present invention includes a mixing head (not shown) for the ingredients of the foam, an outlet from the mixing head being connected to the lower region of a trough 10, the cross-sectional area of which increases from the base 11 of the trough upwardly. The open top of the trough is located adjacent the uppermost end of a stationary angularly downwardly inclined fall plate 12. Below the fall plate is provided a carner for a reel of flexible material 13 which is used to form a movable conveyor hereinafter referred to.

At a position spaced from the uppermost end of the fall plate 12 is located a former 14 which has a substantially circular crosssection as shown in Figure 1D. The former 14 changes in cross-sectional shape along its length from its end nearest the uppermost end of the fall plate 12 to its termination at a position beyond the lowermost end of the fall plate 12, and at a point above a horizontal endless conveyor 22. As is shown in Figures 1A 1B 1C and 1D and as can be seen its vertical height H increases and its radius R decreases, thus at its end adjacent the uppermost end of the fall plate 12 there is presented a slightly bowed form which changes continuously to merge into the substantially circular form shown in Figure 1D. In the region of the section of the former shown in Figures 1A 1B and 1C there is provided a means, in the form of a pair of arcuate supports 15, for internally supporting the flexible material 13 as it is folded to form the substantially circular cross-sectioned movable conveyor. To assist in the folding of the flexible material 13 into the requisite shape there are provided two pairs of gripper rollers 16 intermediate the ends of the arcuate supports 15. The edge regions of the flexible material 13 are held between the rollers 16 and drawn upwardly and towards each other over the supports 15. The supports 15 are mounted on carrier frames indicated by the broken lines 17 (see Figure 1C and Figure 2). Extending along the length of the substantially circular cross-sectioned portion of the former 14 and above its upper face 18 are two endless conveyor bands 19 between which the edges of the flexible material 13 are gripped. Mounting and drive rollers 20 are provided for the conveyor bands 19.

To produce a substantially circular sectioned foamed block, flexible material 13 from the supply reel below the fall plate 12 is fed to the inlet end of the former 14 in such a manner that the flexible material 13 overlies the former 14. The shape of the former 14 is, as described above, such that the two lateral edges of the material 13 are brought together as it moves along the former 14. The single piece of flexible material thus forms a completely closed movable conveyor. At the point where the material 13 assumes a substantially circular section in the former 14 the lateral edges of the material 13 are held between the gripping and suspension conveyors 19 to ensure complete closure of the material 13 for the duration of the process.

Foamable material 21 is fed from the mixing head into the trough 10 and thus onto the moving sheet of flexible material 13 fed from below the fall plate 12. By the time the foaming mixture has reached the substantially circular cross-section region of the former 14 it has substantially reached its full foaming capacity and will thus substantially fill the former. By correctly feeding the foaming mixture foaming will, in fact, be completed before the mixture reaches the outlet end of the former 14, thus the mixture will substantially or completely fill the substantially circular shape defined by the conveyor and will preferably extend marginally above the upper edge of the former 14 in an arcuate manner, being contained by the flexible material conveyor and thus be retained in its substantially circular form.

The flexible material 13 can be a release medium and whilst it is possible to use as the flexible material the well-known kraft paper it is advantageous to use a thin flexible spunbonded sheet since this material possesses greater strength and flexibility and porosity than kraft paper and thus does not have the same tendency to resist formation into substantially circular shape and produce creases which would, of course, adversely affect the final form of the foamed material.

It should be appreciated that slabstock having a cross-sectional shape other than circular can be produced by providing a former which in its substantially closed region at least has a shape other than circular.

WHAT WE CLAIM IS: 1. An apparatus for continuously producing a polymeric foam block of pre-determined cross-section including an open-topped stationary former whose cross-section from a foam inlet position to its termination changes from slightly concave to the requisite crosssectional shape, there being means for feeding flexible movable conveyor forming sheet material onto the former in such manner as to provide an initially open topped slightly concave conveyor onto which block forming material is, in use, directly deposited, the said conveyor thereafter being caused by the former to assume a substantially completely closed section in which section, in use, foaming mixture reaches its maximum height to fill the conveyor and to assume the requisite cross-section.

2. An apparatus as claimed in Claim 1 in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. those parts of an apparatus for continuously producing polymeric foam that are already shown will not be described in detail. A convenient form of known apparatus for use in conjunction with the present invention includes a mixing head (not shown) for the ingredients of the foam, an outlet from the mixing head being connected to the lower region of a trough 10, the cross-sectional area of which increases from the base 11 of the trough upwardly. The open top of the trough is located adjacent the uppermost end of a stationary angularly downwardly inclined fall plate 12. Below the fall plate is provided a carner for a reel of flexible material 13 which is used to form a movable conveyor hereinafter referred to. At a position spaced from the uppermost end of the fall plate 12 is located a former 14 which has a substantially circular crosssection as shown in Figure 1D. The former 14 changes in cross-sectional shape along its length from its end nearest the uppermost end of the fall plate 12 to its termination at a position beyond the lowermost end of the fall plate 12, and at a point above a horizontal endless conveyor 22. As is shown in Figures 1A 1B 1C and 1D and as can be seen its vertical height H increases and its radius R decreases, thus at its end adjacent the uppermost end of the fall plate 12 there is presented a slightly bowed form which changes continuously to merge into the substantially circular form shown in Figure 1D. In the region of the section of the former shown in Figures 1A 1B and 1C there is provided a means, in the form of a pair of arcuate supports 15, for internally supporting the flexible material 13 as it is folded to form the substantially circular cross-sectioned movable conveyor. To assist in the folding of the flexible material 13 into the requisite shape there are provided two pairs of gripper rollers 16 intermediate the ends of the arcuate supports 15. The edge regions of the flexible material 13 are held between the rollers 16 and drawn upwardly and towards each other over the supports 15. The supports 15 are mounted on carrier frames indicated by the broken lines 17 (see Figure 1C and Figure 2). Extending along the length of the substantially circular cross-sectioned portion of the former 14 and above its upper face 18 are two endless conveyor bands 19 between which the edges of the flexible material 13 are gripped. Mounting and drive rollers 20 are provided for the conveyor bands 19. To produce a substantially circular sectioned foamed block, flexible material 13 from the supply reel below the fall plate 12 is fed to the inlet end of the former 14 in such a manner that the flexible material 13 overlies the former 14. The shape of the former 14 is, as described above, such that the two lateral edges of the material 13 are brought together as it moves along the former 14. The single piece of flexible material thus forms a completely closed movable conveyor. At the point where the material 13 assumes a substantially circular section in the former 14 the lateral edges of the material 13 are held between the gripping and suspension conveyors 19 to ensure complete closure of the material 13 for the duration of the process. Foamable material 21 is fed from the mixing head into the trough 10 and thus onto the moving sheet of flexible material 13 fed from below the fall plate 12. By the time the foaming mixture has reached the substantially circular cross-section region of the former 14 it has substantially reached its full foaming capacity and will thus substantially fill the former. By correctly feeding the foaming mixture foaming will, in fact, be completed before the mixture reaches the outlet end of the former 14, thus the mixture will substantially or completely fill the substantially circular shape defined by the conveyor and will preferably extend marginally above the upper edge of the former 14 in an arcuate manner, being contained by the flexible material conveyor and thus be retained in its substantially circular form. The flexible material 13 can be a release medium and whilst it is possible to use as the flexible material the well-known kraft paper it is advantageous to use a thin flexible spunbonded sheet since this material possesses greater strength and flexibility and porosity than kraft paper and thus does not have the same tendency to resist formation into substantially circular shape and produce creases which would, of course, adversely affect the final form of the foamed material. It should be appreciated that slabstock having a cross-sectional shape other than circular can be produced by providing a former which in its substantially closed region at least has a shape other than circular. WHAT WE CLAIM IS:

1. An apparatus for continuously producing a polymeric foam block of pre-determined cross-section including an open-topped stationary former whose cross-section from a foam inlet position to its termination changes from slightly concave to the requisite crosssectional shape, there being means for feeding flexible movable conveyor forming sheet material onto the former in such manner as to provide an initially open topped slightly concave conveyor onto which block forming material is, in use, directly deposited, the said conveyor thereafter being caused by the former to assume a substantially completely closed section in which section, in use, foaming mixture reaches its maximum height to fill the conveyor and to assume the requisite cross-section.

2. An apparatus as claimed in Claim 1 in

which the former changes from slightly concave to substantially circular crosssection.

3. An apparatus as claimed in Claim 1 or 2 in which flexible conveyor material supporting means is provided at that region of the former in which the conveyor material approaches the requisite form.

4. An apparatus as claimed in Claim 3 in which flexible material gripping and transporting means is provided intermediate the ends of the material supporting means.

5. An apparatus as claimed in any one of the preceding claims in which flexible material closing, gripping and transporting means is provided above substantially the whole of the length of the former over which it is of the requisite cross-section.

6. An apparatus as claimed in Claim 5 in which the closing, gripping and transporting means is in the form of a pair of endless band conveyors adapted to grip therebetween the lateral edges of the flexible material.

7. An apparatus for continuously producing a polymeric foam block of substantially circular cross-section substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.