METHOD AND APPARATUS FOR DENSIFYING FOAM PARTICLES

The present invention relates to a method for

recover waste [...] thermoplastic.

In the method, the foam is provided, particulate, on a cooled surface that, vibrating, [...] is capable of the particles away from the site of application. The particles are subjected, while they are located in the vicinity of the vibrating surface, by applying radiant heat sufficient _AOE296A0AO> to cause them to, collapse and their coalescence, the material is removed and collapsed of the vibrating surface, cooled below its temperature of thermoplasticity and is reduced to the size of desired particle.

The contemplated method is characterized in that the aforementioned surface tapers this end d * inlet at its outlet end.

The invention also concerns an apparatus for

densify waste synthetic thermoplastic resin foam. The apparatus includes a supply of foam synthetic resin particulate, a vibrating chute which tapers from its inlet end to its outlet end and has a conveyor surface facing 'the top, a radiant heat source disposed in the vicinity of the surface' transport and capable of providing a [...] radiation sufficient to cause at least partial coalescence and collapse the foam particles situated on said surface * The feeding device is

_AOE280A2AO> [...] disposed at the inlet end of the [...] a cooling arrangement, , near its outlet end, is able to cool the. thermoplastic resin discharged via the discharge end, by being associated with the chute to allow maintaining the conveying surface temperature below which there is no significant cling [...] the material.

Other features and advantages of the invention will be better understood from the description that will follow facing the appended schematic drawings.

Figure 1 represents one embodiment of the invention.-

Figure 2 shows a vibrating chute useful in the practice of the invention.

Figure 1 illustrates an apparatus 10 according to1 * invention which comprises a roller or reducing supply 11 capable of receiving waste from synthetic thermoplastic resin foam and milling the desired caliper. There is that a hammer mill gives highly satisfaction, together with other grinding devices well known.

Mill 11 The device is combined with a storage hopper serving as a source of synthetic resin particles 1 2. [...] The source receives the ' [...]11 of the mill typically by pneumatic conveying, the excess gas and dust is discharged by a clearance lj 5. The source 12 comprises a discharge device14 which, advantageously, is a valve delivering by rotating star well determined amounts of foam particles to an outflow pipe 16 having a discharge end 17 disposed in the vicinity of a vibrating chute 18.

The vibrating chute 18 presented an inlet end 19 and an outlet end 21. It provides a conveying surface 22 which, upwardly facing, receives the [...] particles of the discharge 17 of the conduit 16 and conveys materialits end d 'I9. input at its end' of '" output 21.

Chute 18 communicates with a cooled cooling arrangement 23, such as a source of water or of pulsed air. A. radiant heater is opposite and near the surface 22 facing the top of the corridor 18 and provides enough heat to cause the synthetic resin particles to be subjected to at least partially collapse and coalescence and to form thereby. a bonded foam 26.

11 is good that the bonded foam 26 passes between a pair of pinch rollers 28 which receive while it is still hot plasticized and the further densified.

A cooling device 29, which can advantageously be nozzles-opposite, supplied with pressurized air, cools the densified resin which then passes to a grinding device 31, such as a hammer mill, impact, etc., which will the sheet densified particles desired caliper and discharge in a hopper 32 of where it is of benefit to the route to a machine for producing hot 33, for example an extruder.

Cocky Figure 2, is schematically illustrated a vibrating chute 35 which is highly suitable for implementing the invention. Chute 35 comprises a conveyor pan 36, jacketed and vibrators coupled to members 37 and 38. The trough 36 has an inlet end 39 and an outlet end 4 l. Sa vibration is in a general along the axis of the members 37 and 38 which, advantageously, may be pneumatic or electric. L * trough 36 has a conveyor surface 42 capable of receiving synthetic resin particles. The trough has a gap ' inner 43 which has, from the group, the same dimensions. that the ^ surface 2 and may send a refrigerant coolant such as water or air. -45 A refrigerant inlet is. Located in the vicinity of the end 39 and a refrigerant outlet 46 near the output end 4 1. The transport surface 42 is substantially wider at the inlet end than at the outlet end.

For most synthetic thermoplastic resin foams or other materials in low apparent density particles that * desired. densify, the ratio of the width of the inlet end of the trough and its. conveying surface ' than son_AOE296A0AO> outlet end is advantageously 1,5:1 to 5:1 "according to the nature of the product and, preferably" 1,75:1 to 2,5 :1 [...] More the bulk density is low, more this ratio must be large. A ratio of about 2:1 is very satisfactory when the density of the material to be treated increases by a factor of about 20. The surface of the trough is advantageously of metal polished such [...], for example; steel, aluminum or stainless steel. Adhesion significant amount of the material to the conveying surface can be adjusted by the temperature of the radial [...] Heating or by the distance between these members and the trough. Various release agents, lubricants or analogs are not particularly advantageous if the the apparatus is used to continuously densified a synthetic resin, because frequently applied the lubricant is quite impractical; satisfactory operation are easily provided with a constant power and a constant temperature. The method requires little or no intervention.

A small adhesion of the resin material may occur ;, however, generally the material is quickly dislodged by the vibrations of the trough and flow of the densified material thereon.

The following examples will well understand how the invention may be practiced..

Example 1.

A trough jacket [...], tapered 3 m long, of 36 cm of [...] its inlet end and 20 cm wide at its outlet end (decay being symmetrically) and to sides of 7 cm high (internal dimensions); the trough is carried by A vibrator capable of applying vibration of 3 cycles per second, and for advancing the material from its wide end input output its narrow end. A bank of heaters infrared quartz tubes is disposed opposite the conveying surface of the trough.

Are ground polystyrene foam having a flame retardant and a colorant, to produce waste particulate [...] Irregularly of 0, [...] to 1.9 cm, to bulk specific gravity of g/l 34. The foam polymer has a solution viscosity of from 9.1 centipoise (solution viscosity 1 C $in toluene at 25 e^C). The waste material into particles arrive continuously to the trough vibrating average flow rate of about 1 kg/min. The tees Heating infrared [...] on an input power of 12.2 kilovolts-amperes.

The foamed polystyrene which is located on the trough appears to collapse and forms masses approximately coherent have the appearance of a web of lace, that is passed between two compression rollers cooled having a temperature of about 38^{e C}. The polystyrene outputs compression rollers sheet and it is subjected to a ;) and of air at ambient temperature, passes with a grinder and emerges as a densified pelleted [...] does which has a bulk specific gravity of 490 g/l and a solution viscosity of 8.91 [...]" [...]. The method described hard 6 hours without requiring intervention. A polystyrene first quality extrusion, in the form of nodules to generally cylindrical about 576 g/l ^ [...] point.

Example 2.

The procedure of example 1 is repeated, except that the flow rate supply means in continuous operation over 6 hours is 1.47 kg/min and. ranges from 1.1 to 1.5 lg/min. A sample, representative of the product has a bulk density of 46,0 g/l and a solution viscosity of 8.71 [...].

Example 3"

The example 1 is repeated, except that the flow rate

means supply is 1.1 kg/min and that a total 1.550 kg of waste is densified continuously over a period of 21 hours. A representative sample indicates a bulk density of 435 g/l and a. solution viscosity of 8.89 [...].' Example 4.

4 θ8 kg polystyrene foam containing particles a green pigment and free-d ' flame retardant are processed as described in the example 1.

The foam densified has' a solution viscosity of from 11.6 centipoise and a bulk density of 500 g/l. The material is densified to a_{H [...]}[...][...] grade extrusion in an amount sufficient for the densified waste 23 $constitute the total weight; the mixture is then extruded to form a polystyrene foam density g/l - 25 and solution viscosity of 11.6 [...]. By contrast, , the same type of heavyweight is produced by use of # 23 of regenerated by. foam compression and recycling in an extruder and the device overcomes the volatiles. A foam which is obtained has a density of 25 g/l and a solution viscosity of from 11 [...], indicating a substantial degradation of the polymer obtainable by the process of re..

Example 5.

A polystyrene foam comprising a delayed agent-' engine of inflammation is. [...] to produce waste material into particles having a bulk density of about 57*6 g/l and a solution viscosity of about 9 * ^ 6 [...]. A part of the waste, densified according to the example 1, gives a product which has a bulk density of 493 g/l and a solution viscosity of 8.70 [...]. The densified a remaining portion of the shredded waste using an extruder as in the example 4 and results in a product with bulk density of 592 g/l and solution viscosity of 8.1 [...].

Example 6.

Foam cellular plastic material constituted by a copolymer including about 94.5 $about 5.5 $of styrene and butadiene is ground to produce foam waste bulk density of about 24 g/l and solution viscosity of 10.9 centipoise. With the procedure example 1. of the and a feed rate of 1.07 kg/min, the granulated product obtained has a bulk density of 480 g/l[...] and in solution of about 10.7 centipoise.

Example 7.

The densified by the process of the example 1

waste ground polyethylene. The no physical properties. Note that it takes a delivery

kg-heat greater than that which is required with polystyrene.

Example 8.

Foam plastic material made of poly-ortho-chlorostyrene to solution viscosity of from 5.3 centipoise (solution viscosity 10 $by weight in the methyl ethyl ketone at 25 °C), has an apparent density of about 52 g/l. With the conditions of the example 1, a granulated product is [...] to bulk density of 424 g/l and solution viscosity of from 4.8 centipoise.

Example 9.

A ' polymer consisting of 75 about 25 $$ of styrene and acrylonitrile in weight, having a solution viscosity of 13.2 $(solution to 10 $in methyl ethyl ketone), is sent in an extruder for producing foam where it is flame-sprayed and mixed with a volatile propellant.

The resulting foam is then milled to produce waste into particles which have a bulk density of 52 g/l and a solution viscosity of from 10.1 centipoise. The waste of foam are then processed as in the example 1 to provide a granulated product at bulk density of 224 g/l and solution viscosity of 9.55 [...] (solution to 10 $in methyl ethyl ketone).

Example 10.

Similarly to 1' example 9, a foam is prepared from a copolymer of styrene and 75 $25 $maleic anhydride.. The polymer has a viscosity of. 4,4 centipoise (solution # 10 in the [...] ). The extruded foam is ground to produce waste having a particle size of 0.08 to 2.0 cm, a bulk density of- 35 g/L and a solution viscosity of from 4.10 centipoise.

The shredded waste obtained are treated as in the example 1 to provide a granulated product at bulk density of 380 g/l and solution viscosity of from 3.9 centipoise (solution # 10 in the [...] ).

j Similar to the previous examples, other foams of thermoplastic resins are.-easily extrudable densified into nodules by the method and with the apparatus according to the present [...]. Identification polymers of thermoplastic resins, that are suitable for use in implementing I of the invention is easily by exposing a part of polymer foam such as ground particles to heat radiation in an amount sufficient [...] the molecules; foam to at least partially collapse without decomposition vi sib the j [...]. gold s from exposure to the radiant heat-, 20 that depression is not obvious or occurrence markedly decomposition, .the material is not suitable.