METHOD AND PLANT FOR PRODUCING PRODUCTS OF SYNTHETIC FOAM

Abstract: By a method and a plant for producing polyurethane foam products foaming reagents (12) are fed to a mould lined with paper (3, 4) which is movable by means of a conveyor belt (2), said paper linings (3, 4) being unrolled from rolls (5, 11). The reagents are mixed in a mixer and fed through a pipe (10) and inlet pipes (8, 9) to a nozzle (7) having a vertical slit the length of which substantially corresponds to the desired height of the finished product. The reagents will thus be fed to the mould spread over its height so that the reagents will immediately adhere to the side paper (4), and will not be required to move vertically upwards from the bottom (3) of the mould so that the finished product gets a quite plane surface without cracks or other defects due to tensions between the side paper (4) and the foaming reagents (12).

Description: METHOD AND PLANT FOR PRODUCING PRODUCTS OF SYNTHETIC FOAM. The invention relates to a method for producing products of polyurethane or the like by feeding foaming reagents in one end of a mould, which may be continuously movable, and a plant for per¬ forming the method. Polyurethane foam has many different applications and can be produced to be stiff, semi-stiff and flexible. Production thereof is by mixing and curing foaming reagents in a mould. The reagents will generate a gas making the reagents foam, or a foaming gas may be added to the mixed reagents. By the foaming the foam will expand and it gradually polymerizes and cures to a polyurethane product shaped by the mould. Such products are for example used for mattresses and cushioned seats. The mould may be an ordinary mould open at the top but often movable moulds are used. This is to be understood in such a manner that a movable mould typically comprises a conveyor belt forming a movable bottom in the mould and a pair of oppo¬ sitely arranged side walls which may be fixed or movable with the bottom. Often the sides and the bottom are lined with eg. kraft paper or polyethylene film which is drawn from rolls and is moved at the same rate as the bottom conveyor belt. The moulding itself it carried out by feeding foaming reagents on the bottom of the mould, the conveying of bottom and sides preventing fresh reagents from being fed onto the previous ones. Should this happen, the finished product will get an uneven surface and an uneven density. For producing comparatively high products it is moreover known to design the front part of the mould V-shaped so that when expanding the reagents are forced towards the top side of the mould. All the known methods and plants have one substan¬ tial drawback, namely that the finished products in the mould open at the top will have an arched surface. This is due to the fact that the reagents by the sides of the mould will adhere to the paper linings so that the product will become higher in the middle than by the sides. Such arched por¬ tions can normally not be used and must be cut off. This represents a waste of raw material as well as an increase in product costs. Furthermore, during the expansion tensions between the side walls and the partly foamed reagents may occur which may result in cracks and other defects in the finished product. It is the object of the invention to provide a method where the finished products have a substan¬ tially plane surface without being acted on by pressing or the like and where the above drawbacks are moreover eliminated. This is achieved according to the invention by feeding the reagents over substantially the entire desired height of the finished product. By such distributed feed where the amount of re¬ agents must naturally match the height of the product as well as the moulding rate, the reagents are not required during the expansion to work themselves up in the mould, but will immediately adhere to its sides over the entire height. The result is a plane surface on the finished product which will not either show cracks or other defects. A method according to the invention can as disclosed in claim 2 be characteristic in that the reagents are fed simultaneously over the mentioned entire height so that reagents are fed over the entire height with substantially the same foaming degree. If the reagents are pre-mixed before being fed to the mould, it is important that the material being simultaneously fed eg. at the top and the bottom of the mould has the same foaming degree as otherwise it will not be possible to obtain a uniform product. The foaming degree is highly dependent of the time passing from the moment of mixing and to the feeding of the reagents in the mould. It is advantageous if as disclosed in claim 3 the reagents are fed through a nozzle with a sub- stantially vertical slit the length of which prefer¬ ably corresponds to the height of the finished product. Such feeding will ensure good control of the feeding and a uniform product. - B U EA OMPI If, as disclosed in claim 4, the reagents are fed through a number of inlets distributed over the height of the nozzle, it is ensured that when being fed the reagents have the same foaming degree since they are not introduced into the nozzle at one end thereof and then carried through the nozzle. The object of the invention is furthermore to provide a plant for a continuous production of polyurethane foam products by performing the method according to the invention, and according to the invention said plant is characteristic in that the plant comprises a feed means for foaming re- agents said means being adapted to feed the reagents into the mould over a height substantially -corre¬ sponding to the desired height of the finished product. By such a plant the foaming reagents will be fed to the mould in such a manner that the finished product will have an even and uniform surface since the reagents are not fed at the bottom of the mould. The reagents will therefore not be required to expand upwards along the sides of the mould. A plant according to the invention can as disclosed in claim 6 be characteristic in having a nozzle with a vertical slit the length of which substantia¬ lly corresponding to the desired height of the finished product. Such a nozzle is simple in manu¬ facture and affords goods control of the feeding of the reagents. A very simple form of nozzle - B URE OMPI may be a pipe with a cut-out slit. It is advantageous if the nozzle is connected with a number of inlets as disclosed in claim 7 thus ensuring that the reagents fed to the mould have the same foaming degree. Surprisingly it has been found that it is possible to obtain an excellent quality of the finished product if two inlet pipes arranged as disclosed in claim 8 are used. If in a plant which moreover comprises a mould having a part being funnel-shaped in the horizontal plane between the front section of the funnel- shaped part and the slit of the nozzle there is arranged an area where the mould has substantially parallel side walls, a further good quality of the finished product is obtained. This is probably due to the fact that the reagents obtain good adhesion to the side walls before the final expan¬ sion takes place. The invention will be further described in the following with reference to the drawing wherein Fig. 1 is a section through a plant according to the invention seen in the direction of the arrows along the line I-I in Fig. 2, and Fig. 2 is a top view of a plant according to the invention. • fUREA OMPI Figs. 1 and 2 show a plant according to the inven¬ tion which plant is referred to by reference numeral 1. By the underside of the plant 1 there is arranged a conveyor belt 2 forming a bottom in plant 1 and on which there is arranged a paper lining 3 moving along together with the conveyor belt 2 and unrolling from a roll 11. The side walls of the mould itself consist of paper linings 4 engaging guides 15, 16, hinged plates 13, and parallel side plates 17, 18. The linings for the side walls are unrolled from rolls 5,6. The plant comprises a nozzle 7 having a slit the height of which corresponds to the height of the moulded product 12. The nozzle 7 is provided with two inlet pipes 8, 9 ending in the nozzle in such a manner that the reagents leaving the nozzle through ths slit will be more or less equally foamed. The reagents are mixed in a not shown mixer and carried to the inlets 8, 9 through a central distribution pipe 10. Fig. 2 shows how the mould is provided with first a short part with parallel side walls and then a V-shaped part extending in a further part with parallel side walls. The most important expansion of the materials occur in the V-shaped part of the mould where same is bounded by hinged plates 13 mounted on suspensions 14 being movable in the plane of the bottom. The dashed lines in Fig. 2 show an alternative position of the plates 13. The plates 13 are followed by parallel side walls REA OMPI 17 , 18 . By means of the hinged plates 13 and the movable suspensions 14 it is possible to change the shape of the V-shaped part in such a manner that it can be adapted to the actual moulding process and the actual product. The guides 15 are also movable so that the V-shaped part may be arranged so as to begin at the slit of the nozzle 7. It is obvious to a person skilled in the art that the V-shaped part must be so long that the expansion is substantially terminated when the product leaves same. It is moreover obvious that a plant for performing the method according to the invention may be designed in many different ways when only the foaming reagents are fed in such a manner that the reagents are not to move vertically in the mould so that the inconveniences in connection with such movement are avoided. The method according to the invention can of course also be performed in moulding plants where the reagents move by themselves through the mould said mould being designed with a suitable inclina- tion. Finally, it is worth mentioning that the part of the mould being bounded by the parallel walls 17, 18 must be so long that the finished product is suitably cured during its passage through this area. At their lower edge the plates 13 can be sealed in relation to the bottom by means of generally known lip packings made of teflon or the like. By the invention according to the application OMPI the reagents will adhere to the side paper in its full extent and the above-mentioned tension between side paper and product will be fully elimi¬ nated as will the risk of crack formation. Moreover, an undesired loss of gas from the reagents will substantially avoided just as the product's general skin formation consisting of more or less foamed reagents will be highly reduced. It is obvious to a person skilled in the art that the method according to the invention can be used in connection with any type of synthetic foam and not only polyurethane foam. The foaming reagents can be mixed in the nozzle itself or before same in a mixer or the like thus ensuring a very homoge¬ nous foam. It is moreover possible to use the guides 15 for completely shutting off the foam by carrying the guides against each other. This will in a simple manner afford control of the foam feeding. UREA OMPI

Claims: PATENT CLAIMS 1. Method for producing polyurethane foam products or the like by feeding foaming reagents in one end of a mould which may be continuously movable, c h a r a c t e r i s e d i n that the reagents are fed over substantially the entire desired height of the finished product. 2. Method according to claim 1, c h a r a c t e r¬ i s e d i n that the reagents are fed simulta¬ neously over the said entire height so that the reagents are fed over the entire height with sub¬ stantially the same foaming degree. 3. Method according to claims 1-2, c h a r a c¬ t e r i s e d i n that the reagents are fed through a nozzle (7) with a substantially vertical slit the length of which preferably corresponds to the height of the finished product. 4. Method according to claim 3, c h a r a c t e r¬ i s e d i n that the reagents are fed to the nozzle (7) through a number of inlets (8,9) distrib- uted over the height of the nozzle (7). 5. Plant for continuously producing polyurethane foam products or the like, said plant comprising a mould which may be continuously movable and in one end of which foaming reagents are fed, c h a r a c t e r i s e d i n that the plant comprises a feed means for the foaming reagents said means being adapted to feed the reagents in the mould over a height substantially correspond- 1-U EA OMPI ing to the desired height of the finished product. 6. Plant according to claim 5, c h a r a c t e r¬ i s e d i n that the feed means is a nozzle (7) with a vertical slit for feeding the reagents and that the length of the slit substantially corresponds to the desired height of the finished product. 7. Plant according to claim 6, c h a r a c t e r¬ i s e d i n that the nozzle (7) is connected with a number of inlet pipes (8,9) and that these pipes are distributed over the length of the nozzle (7). 8. Plant according to claim 7, c h a r a c t e r¬ i s e d i n that the nozzle (7) has two inlet pipes (8,9) and that these pipes are connected with the nozzle (7) in areas which are respectively one quarter of the length of the slit from each of the ends of the slit. 9. Plant according to claims 5-8 and where the mould comprises a part being funnel-shaped in the horizontal plane and followed by a part with substantially parallel sides, c h a r a c t e r¬ i s e d i n that between the front section of the funnel-shaped part and the slit of the nozzle (7) there is an area where the mould has substan- tially parallel side walls. BU I I OMPI

Inventors: HYLDIG JENS MARTIN HOVMOELLER, HYLDIG, JENS, MARTIN, HOVMOELLER
Applicants: HYMA ENGINEERING APS
Application year: 1984
Main classification: B29D27
IPC codes: B29C44