IE912221A1 - Recycling of thermosetting pu foam parts - Google Patents

Abstract

The invention relates to the recycling of thermoset polyurethane foam waste for the thermoforming of new structures. To this end, the waste is comminuted, mixed with an SPE/EP powder coating mixture in heated moulds or between two hot surfaces with compression at a temperature between about 70 DEG C and the decomposition temperature, is kept in this state for between about 2 seconds and 300 seconds and is subsequently demoulded. The temperature, compression and treatment time can be varied within broad limits.

Description

Dgsgurray Recycling of thermosetting TO foam part» The Invention relatea to a process for recycling comminuted thermosetting polyurethane foam parts for producing naw aeal-flnlshed products or finished articles using a binder aired with the comminuted foaa parts.

The proportion of furnishing parts consisting of plastic foams, and in particular of thermosetting polyurethane foams, used in the vehicle Industry, particularly in tbs motor vehicle industry, but also In other areas, such as for example mouldings for seats, head rests, arm rests and tbs like, is considerable and ia taken mainly to overflowing dumps as waste occurring during production end in particular during breaking up of vehicles taken out of circulation. Its disposal by means of combustion is ruled out as a possibility because of the pollutant emissions to be expected In the process.

It has therefore been an aim for sone time to reprocess plastic foam waste of thia type. While there are no great technical problems in the processing of thermoplastic plastic parts to form naw mouldings, the recycling of thermosetting portions of waste of this type fails because of the property which thermosetting plastics have of passing through a thermoplastic state which can be exploited by applying heat for moulding, and instead curing with three-dimensional cross-linking during polymerlastion, as a result of thia they can no longer be softened by heat (see for exanpla Schrdter, LautonschlAger, Bibrack, TA8CHBMBDCS DER CHEMIk’, 10th edition, 1983, Publisher Barri Deutsch, Thun and Prankfurt/Msln, page 583).

A type of recycling of thermosetting foena, in particular thermosetting polyurethane foams, la therefore practised.

In which the parts produced are initially comminuted. Tbs comminuted products, which are then mostly in the form of shreds or flakes, are than moulded together with a binder known per se, such as for example e polyurethane onecomponent adhesive, a suitable acrylate or the like, with application of bast and pressure to torn new mouldings, nets and the like. Processes of this type nay produce articles which are very useful, but the binder is a considerable cost factor. In addition, In the specialist field there Is a widely-held view that the properties of tbs naterials used In comminuted form ere changed by binders of this type. The use of parts node from recycled notarial is therefore abandoned In many cases. The difficulties arising from the considerable pollution of the environment by disposing of tbs waste are accepted.

It has now been found that there is a way for recycling thermosetting PH foam waste, which falls back completely on recycled material, for producing new parts which can optionally bs recycled and which have a wide variety of properties, by processing certain waste from the coating operation together with the thermosetting polyurethane waste.

The technical object of the invention la to show a simple and low coat-intensive way of combined recycling, in particular of thermosetting polyurethane foams on tbs one band, and wests from the coating operation regarded as specialised waste on the other hand, which leads to high quality products having « wide variety of properties.

This Object la achieved in e process of the type described in the Introduction by using a powder coating nlxturn produced as waste, consisting of portions of special polyester resins (SPB) and epoxy resins (BP) and admixed to the comminuted mass of thermosetting polyurethane foam aa binder, and by introducing the final mixture into a mould and subjecting It to the action of beat for a period of about 20 to 2S0 seconds at teaperaturee between about 80*C and a value in the region of the decomposition temperatures, preferably a value up to about 200*C, maximum about 220’C. The portion of powder coating mixture may be between about 10 I and about 40 %, based on the weight, portions between about 16 - 20 t and - 35 t. In particular between about 20 t and 30 t, being preferred. The level of the portion of powder coating mixture has thus proved to be an essential factor in influencing the properties of the materiel, in IS particular the strength properties and the surface quality of the final product.

By selecting the temperature end exposure time, it may thus ha determined whether the coating mixture remains thermoplastic or cures to form a thermo set. If a value between about 80’C and about 130*C ie selected as the exposure temperature for an exposure time between about 100 seconds and 25 seconds, the coating powder mixture uaed as binder remains thermoplastic; an exposure temperature from a value between about 160*C and about 180*C for an exposure time between about 5 seconds and 180 eecands leads to at leest partial cross-linking of the coating powder to the thermosetting form. The heating effect may he carried out in a manner known per so by heating the mould, by introducing a hot gas, for example air or steam, into the mould, or by combining both measures. However, It la also possible to heat the crude moulding initially outside the mould, for example by means of a hot gas, to an elevated temperature of, for example about 200*C, optionally also up to 22O’C, and place it in the cold or unheated mould immediately thereafter to bring it to the required shape.

The moulding produced (In the thermoplastic range) at a temperature between about 80*C and about 13O’C for an exposure time - influenced by the temperature need between about 100 seconds and 25 seconds, is advantageously kept in the mould when the heating effect is completed until it is cooled to a temperature below about 80*C. However, it may ba advantageous to remove the moulding from the mould Immediately after completing the heating effect and cool It, in particular after treating in the thermosetting range (above about 16Q*C).

In a particular embodiment of the invention, the moulding times, that is the time during which beat has to ba supplied to the moulding in the mould, may be considerably reduced, by mixing about 2 4 to about 15 % of phenol resin powder, based on the 8FH/BP mixture, into the binder consisting of an SPB/KP powder coating mixture. A measure of this type et the same time leads to e more pronounced cross-linking of the coating mixture added aa binder.

In a particular further embodiment. Individual regions of the surface of the moulding or the entire surface may thus acquire a particularly smooth and continuous form, by bringing the walls of the mould briefly to a temperature between about 220’C and about 34O’C, preferably at the and of the heating period, all over or in the regions which are to have such a continuous surface. The temperature for the brief heating Is preferably between about 280*C and about 32O’C.

On the whole It baa proved to be advantageous if the moulding is compressed to a bulk density wblch Is at least about 5 % to 10 % above that of the polyurethane foam parte used and - depending on the required stability, the acoustic stability and/or the required weight - may ba up to 50 8 above the initial valuo. s In a farther development of the Invention, the parte produced es described above «ay be laminated on one side S or on both sides with a fleece, a knitted fabric or cloth or with a farther durably applied surface structure. This ay be carried out together with the moulding of the part by means of the heat introduced for moulding the pert to be laminated, optionally by utilising the effect of the admixed coating powder mixture, or may also take place after shaping. Likewise, joining between moulding end surface atructure(e) by eeana of e further binder known per se may take place in the mould or on the shaped part.

The following examples serve to illustrate the invention.

EXAMPLE 1 Poem waste from thermosetting polyurethane having an average bulk density of 40 kg/m* was comminuted to e flake grain else of 6 mm 0*. The SPB-SP resin was admixed as binder in an amount of 20 to 30 weight I in an aerodynamic process.

The flakes were introduced loosely into e mould heated et 180*C, compressed to a bulk density of 120 kg/m* and kept under these conditions for 2 minutes. The moulding removed later showed a thoroughly coherent surface and high elasticity While largely maintaining the pore structure.

EXAMPLE 2 The comminution product of flakes according to Example 1 treated with SPB-BP resin was compressed between two plates to form a surface structure 30 am thick and 100 kg/m* bulk density to produce a bond between the flakes· and treated in this state for 15 seconds with hot air et 200*C blown through the pile of flake*. After cooling, the plate-like structure produced was placed la a closed mould preheated et 180*C and further coatpressed to a thickness of 3 am and a weight per unit area of 3 kg/m*. The plate produced showed virtually no pore structure, its surface was continuous. The structure produced was suitable as a heavy layer for sound-insulation purposes. gXAWPLB 3 The plate produced as the end product of Bxaog>le 2 was placed in a 3D press aould and shaped at a temperature of 200*C and kept in the hot preae mould for a period of 2 minutes. A structure which can be used in vehicles for nolae-insulatlon purposes was produced.

EXAMPLE 4 The comminution product of flakes according to Kxaaple 1 treated with BPS-BP resin was placed In a mould heated at a temperature of 200*C, the base of which had previously been covered with e reticulated PBS fabric, and kept in the mould for 3 minutes after compressing to about 65 % of Its Initial volume. In the finished moulding the PBS fabric was durably bonded to the moulding.

EX&MPM 5 Foam waste from thermosetting polyurethane having an average bulk density of 40 kg/m* was comminuted to a flake grain slse of 15 u 0 end mixed with the SPB-KP resin as binder in an amount of 20 to 30 weight % in an aerodynamic process. The flakes were placed in the mould heated at 180"C and treated for 30 seconds with hot air at 250*C while compressing to a thickness of 10 am and 100 kg/m’ bulk density, the flakes being bonded to one another. The net produced was moulded together with tbs pi ate-like structure of Bxample 2 in e mould heated at 200*C to font a 3D moulding and kept at this temperature for 2 ainutes. The structure produced was an acoustically effective spring'mass system which can he used for noise10 insulation purposes in vehicles.

EXAMPLE 6 The comminution product frost flakes according to Bxaeple IS 1 treated with SPB-EP resin powder wee mixed with 30 4 of fibre waste, placed in a 3D mould heated at 200*C without admixing further binders, and kept in the mould for 2 minutes after compressing to shout 60 % of the initial hulk density. The moulding showed good bonding between flakes and fibres which clearly improves the strength properties.

BXAMPLB 7 Foam wests from thermosetting polyurethane having a grain slke of 10 - 15 mm 0 and an average bulk density of 40 kg/m* was treated with various SPB-EP resin portions between 10 and 40 weight * in several tests. Each of the mixtures was moulded to form plates according to Example 2 end treated in 3D moulds according to Bxaeple 3.

The strength properties of the mouldings taken from the mould were dependent to a considerable extant on the percentage amount of admixed BPE-EP resin powder, wherein the moulding having 10 4 resin mixture showed a relatively poorly solidified surface, whereas the moulding having 40 4 of resin powder mixture showed considerable elasticity and beading strength with a smooth, continuous surface.

Claims (15)

1. S 1. Process for recycling comminuted thermosetting polyurethane foam parts for producing new ssml-flnlshed products or finished articles using a binder mixed with tbe comminuted foam parts, characterised in that a powder coating mixture consisting of SPE and BP portions and 10 admixed to the conmlnnted mass of thermosetting polyurethane foam ie used as hinder, end in that the final mixture is introduced into a mould and subjected to the action of heat for a period of about 3 seconds up to about 120 seconds at temperatures between about BO’C and a 15 value in the region of the decomposition temperatures, preferably a maximum value of about 200 to 220*C.

2. Process according to claim 1, characterised in that a value between about 80*C and about 130”C is selected as 20 tbe exposure temperature for an exposure time between about 100 seconds and 25 seconds.

3. Process according to claim 1, characterised in that a value between about 160*c and about 180*C is selected as 25 the exposure temperature for an exposure time between about 5 seconds and 45 seconds.

4. Process according to one of the preceding claims, characterised in that the moulding ia kept in the mould 30 after completing the heating effect until it has cooled to a temperature below about 80’C.

5. Process according to one of oleins 1 to 3, characterised in that the moulding is removed from the 35 mould immediately after completing the heating effect.

6. Process according to claim 1 In conjunction with one of claims 2 to 5, characterised ia that the crude > moulding Is heated mt about 200*C to 220*C end immediately thereafter pieced io a cold mould for aoulding. and after 9 e period of about 25 seconds to 100 seconds is shaped.

7. Process according to one of the preceding claims, in particular according to claim 3, characterised la that about 2 t to about 10 t of phenol resin powder, based on the SPS/KP mixture, is mixed into the binder consisting of aa 8PK/KP powder coating mixture.

8. Process according to oaa of the preceding elaima, characterised in that textile or other fibre-like 15 components are mixed into the coaminuted mass of thermosetting polyurethane foea, preferably before the addition of the powder coating mixture, to increase the mechanical strength. 30 9. Process according to ooe of the preceding claims, character!aed in that the mouldings are heated by heating the aould and/or by introducing · hot gas. ID. Process according to one of the preceding claims, 35 characterised in that the walls of the aould are brought briefly to a temperature between shoot 220*C end about 34O’C. preferably et the end of the besting period, ell over or in the regions where the moulding is to have e particularly smooth, continuous sortace. U. Process according to elals 10, characterised la that the temperature for brief heating ie fixed between about 280*C and shoot 32O’C.

9. 12. Process according to one of the preceding cl aims, characterised in that the compression of the filling introduced into the aould ie carried out to a hoik density which is at least shoot 5 % to 10 % above that of the polyurethane foea parts used.

10. 13· Process according to one of the preceding claims. characterised in that a fleece, a knitted fabric or cloth or another surface structure is applied to one aide or both sides of the moulding produced from polyurethane foam flakes treated with an EPE-EP powder coating mixture and le durably bonded to the pert.

11. 14. Process according to claim 13, characterised in that the application and bonding is carried out witb moulding.

12. 15· Process according to claim 13, characterised in that the application and banding le carried out subsequent to the shaping. lb. Process according to one of claims 13 to 15 , characterised in that bonding between moulding and surface etructure(s) is carried out by means of the 8PEEP coating powder portion and the beat Introduced for moulding the part to be laminated.

13. 17 , Process according to one of claims 13 to 15, characterised in that a binder known per se la used for producing the bond between moulding end surface structure(s).

14. 18. A process according to claim 1 for recycling comminuted thermosetting polyurethane foam parts, substantially as hereinbefore described and exemplified.

15. 19. A semi-finished product or finished article, whenever obtained by a process claimed in a preceding claim.