GB1594471A

GB1594471A - Production of beads from molten or thermoplastic material

Info

Publication number: GB1594471A
Application number: GB432377A
Authority: GB
Original assignee: Bland R B; Mason & Co Ltd Vaughan
Current assignee: Bland R B; Mason & Co Ltd Vaughan
Priority date: 1978-04-24
Filing date: 1978-04-24
Publication date: 1981-07-30

Description

(54) IMPROVEMENTS IN THE PRODUCTION OF BEADS FROM MOLTEN OR THERMOPLASTIC MATERIAL (71) We, ROGER PERCIVAL BLAND, of 41, Paddock Wood, Prudhoe Niorthumlberlend, NE42 5BJ, a British Sub jeot, and VAUGHAN MASON & COM PANY LIMITED, of Factory Road, Blaydonon-Tyne, Tyne and Wear, a British company, 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 descnibed in and by the following statement: The present invention relates to a method and apparatus fcr producing beads from mel- ten or thermoplastic material.

It is known to drop molten wax on a stainless steel belt, where it solidifies, but such a method is disadvantageous because the beads are not spherical.

According to a first aspect of the present invention there is provided a method of producing beads from molten or thermoplastic material inoluding the steps of: releasing discrete droplets of said material within a body of a denser liquid; maintaining the liquid in the zone of release of the material at a tem- perature equal to or higher than the melting point of the material; coaling the liquid in the upper zones of said body so that as the droplets of material rise they are cooled to form beads; and removing the beads from the surface of the liquid.

The beads are usually generally spherical, and may be between 0.001 to 10 mm in diameter.

According to a second aspect of the present invention there is provided apparatus for the production of beads from molten or thermoplastic material including: a container for holding a liquid; an inlet in said container for conveying said material for release within the liquid; at least one bead-forming nozzle in a lower zone of said container connected to said inlet; means for maintaining a tam- perature gradient within said liquid such that the temperature of the liquid adjacent the nozzle exceeds the temperature at the surface; and means for removing beads from the surface of the liquid.

Preferably said material is wax and said liquid is water.

Preferably there is a heater within the container. Preferably said means for removing beads, comprises: means for bleeding off said beads and a portion of said liquid; means for separating said beads and the bled off liquid; and means for drying said beads.

The present invention will now be des cribbed in greater detail by way of example with reference to the accompanying drawing wherein: Fig. 1 is a section through a beadiferming apparatus; Fig. 2 is a section through the same apparatus taken along the line A-A of Fig. 1; and Fig. 3 is a section through one ob the nozzles.

The apparatus shown in Fig. 1 has an inlet 1 for the supply of molten wax to a reservoir 2. The rate of flow of the wax through the inlet 1 is controlled by a tap 3, the wax passing from the inlet 1 to nozzles 4 via the reservoir 2. The shape of the nozzles 4 is shown in greater detail in Fig. 3, and is such that there is water below the point of formation of the bead and the nozzle is provided with a chamfered edge. Droplets 21 are formed by the nozzles 4 within the bcdy of water 19 contained by a tank 5.

The diameter of these droplets 21 is dependent on the diameter od the nozzles 4, and can be from 0.001 to 10 mm. The water 19 adjacent the nozzles 4 is maintained at a temperature above the melting point of the wax by means of a steam coil 6 (see Fig. 2) having an inlet 15 and an outlet 16, the steam coil 6 passing up through the centre of a concentric tube 25 carrying the wax from the inlet 1 to the top of the wax reservoir 2. As shown, the steam aoil 6 having passed up through the centre of the tube 25 makes three turns 6a inside the circular row of nozzles 4 and one turn 6b outside the cir calor row of nozzles 4, before passing down through the wax reservoir 2 near the wall thereof to the outlet 16.

Due to the fact that the tube 25 is designed to surround the upward rising steam inlet pipe, the hot steam inlet does not come into oontact with any water which may be in the wax reservoir 2. Without this coaxial arrangement of the tubes, any water in the wax reservoir would begin to boil and disrupt the steady flow of wax through the nozzles 4.

A water drain outlet p.ipe 26 and a tap 27 is provided at the bottom of the wax reservoir 2 to drain off any water which has accumulated therein. Water penetration into the wax reservoir 2 may arise if wax is not flowing upwards through the nozzles 4.

Since the wax in the reservoir 2 is less dense than the water in the water contained in the tank 5, the droplets 21 rise in the tank 5. As they get further away from the steam coil 6 the temperature of the surrounding water 19 decreases, and eventually the droplets solidify to form spherical beads 20. The beads 20 and some of the, water 19 are bled off by means of a trough 7. The bleeding operation is performed by a flow of water along the trough or by a fine water jet or a jet of air and water issuing from nozzles 22, which firstly move the beads away from the top of the column and secondly over the edge od a weir 23 at the far end of the trough 7. Furthermore the jets of water or water/air provide additional cooling for the beads. After passing over the weir 23, the beads fall into' a separator 8, between the left- hand wall thereof as seen in Fig. 1, and a baffle 9. The water 19 can flow under the baffle 9 and out through an outlet 10. However, the beads 20, being lighter float on the surface of the water 19 and are trapped.

They spill over down a ramp 11 into a drying tube 12. They flow or roll down a perforated screen 13, being dried meanwhile, by means of air flowing up through the screen 13 from an air inlet 14. They are collected as they emerge from the drying tube 12.

The bottom of the wax reservoir 2 extends as a flange 28 at the lower end of the tank 5. The reservoir 2 is clamped to the tank 5 by means of an annular metal ring 29 which is held by bolts 30, the ring 29 having a chamfered edge which engages with an asbestos ring 31 carried on a protruding flange at the bottom of the tank 5.

When not in use the apparatus may be drained of water via the outlet pipe 26 except for any water that is at a lower lever than the wax nozzles 4 which cannot pass into the wax reservoir 2.

Various factors influence the sphericity of the beads 20 formed: - (a) the temperature of the molten wax.

(b) the size of the apertures of the nozzles, 4 which determine droplet size.

(c) the shape of the nozzles 4 which affects the release of the droplets 21.

(d) the temperature of the water surrounding the nozzles which affects the release of the droplets 21.

(e) the temperature gradient in the water 19 through which the droplets 21 pass, and thus, indirectly, the depth of the water 19.

(f) the rate at which wax flows through the nozzles 4.

In the embodiment illustrated the preferred temperature of the molten wax is 530C.

A useful range od teinperatures would be from the melting point of the wax up to 1200,C. A desired range of operation would lie between 100,C to 400C higher than the melting point of the wax.

A useful range for the size of the apertures of the nozzles 4 would be between 0.8 to 6.4 m.m. and the desired range would be 0.8 to 4.0 m.m.

The temperature of the water in the neighbourhood of the nozzles would have a useful range of between OOC to 200C higher than the melting point of the wax, with an upper limit of 970 C. A preferred value would be 50C higher than the melting point of the wax. The temperature gradient between the top and bottom ob the tank 5 would be pre ferably approximately 200C over a length of 3 metres.

A useful range for the rate of flow of the wax through each nozzle would be between 2 and 6 kilogrammes/lhoulr.

The manner in which the beads 20 are removed from the surface of the water 19 is also critical in that it must be a method which does not adversely affiect the temperature gradient of the column of water 19 in the tank 5. The method employed must not, for instance, result in cooling of the water surrounding the wax nozzles at the bottom of the water column.

WHAT WE CLAIM .IS:-- 1. A method of producing beads from molten or thermoplastic material including the steps of: releasing discrete droplets of said material within a body of a denser liquid; maintaining the liquid in the zone of release of the material at a temperature equal to or higher than the melting point of the material; cooling the liquid in the upper zones of said body so that as the droplets of material rise they are cooled to form beads; and removing the beads from the surface of the liquid.

2. The method according to claim 1, wherein the step of cooling the beads addi tionaily includes conveying the beads, once they have risen to the surface of the liquid, along a horizontally extending stretch of the liquid.

3. The method according to claim 2, wherein the beads are removed from said horizontal stretch of liquid by causing them to be lifted over weir means provided at the end of said horizontal stretoh of liquid.

4. The method according to any one of the preceding claims, wherein the material is wax and the liquid is water.

5. The method according to any one of

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. wax reservoir 2. Without this coaxial arrangement of the tubes, any water in the wax reservoir would begin to boil and disrupt the steady flow of wax through the nozzles 4. A water drain outlet p.ipe 26 and a tap 27 is provided at the bottom of the wax reservoir 2 to drain off any water which has accumulated therein. Water penetration into the wax reservoir 2 may arise if wax is not flowing upwards through the nozzles 4. Since the wax in the reservoir 2 is less dense than the water in the water contained in the tank 5, the droplets 21 rise in the tank 5. As they get further away from the steam coil 6 the temperature of the surrounding water 19 decreases, and eventually the droplets solidify to form spherical beads 20. The beads 20 and some of the, water 19 are bled off by means of a trough 7. The bleeding operation is performed by a flow of water along the trough or by a fine water jet or a jet of air and water issuing from nozzles 22, which firstly move the beads away from the top of the column and secondly over the edge od a weir 23 at the far end of the trough 7. Furthermore the jets of water or water/air provide additional cooling for the beads. After passing over the weir 23, the beads fall into' a separator 8, between the left- hand wall thereof as seen in Fig. 1, and a baffle 9. The water 19 can flow under the baffle 9 and out through an outlet 10. However, the beads 20, being lighter float on the surface of the water 19 and are trapped. They spill over down a ramp 11 into a drying tube 12. They flow or roll down a perforated screen 13, being dried meanwhile, by means of air flowing up through the screen 13 from an air inlet 14. They are collected as they emerge from the drying tube 12. The bottom of the wax reservoir 2 extends as a flange 28 at the lower end of the tank 5. The reservoir 2 is clamped to the tank 5 by means of an annular metal ring 29 which is held by bolts 30, the ring 29 having a chamfered edge which engages with an asbestos ring 31 carried on a protruding flange at the bottom of the tank 5. When not in use the apparatus may be drained of water via the outlet pipe 26 except for any water that is at a lower lever than the wax nozzles 4 which cannot pass into the wax reservoir 2. Various factors influence the sphericity of the beads 20 formed: - (a) the temperature of the molten wax. (b) the size of the apertures of the nozzles, 4 which determine droplet size. (c) the shape of the nozzles 4 which affects the release of the droplets 21. (d) the temperature of the water surrounding the nozzles which affects the release of the droplets 21. (e) the temperature gradient in the water 19 through which the droplets 21 pass, and thus, indirectly, the depth of the water 19. (f) the rate at which wax flows through the nozzles 4. In the embodiment illustrated the preferred temperature of the molten wax is 530C. A useful range od teinperatures would be from the melting point of the wax up to 1200,C. A desired range of operation would lie between 100,C to 400C higher than the melting point of the wax. A useful range for the size of the apertures of the nozzles 4 would be between 0.8 to 6.4 m.m. and the desired range would be 0.8 to 4.0 m.m. The temperature of the water in the neighbourhood of the nozzles would have a useful range of between OOC to 200C higher than the melting point of the wax, with an upper limit of 970 C. A preferred value would be 50C higher than the melting point of the wax. The temperature gradient between the top and bottom ob the tank 5 would be pre ferably approximately 200C over a length of 3 metres. A useful range for the rate of flow of the wax through each nozzle would be between 2 and 6 kilogrammes/lhoulr. The manner in which the beads 20 are removed from the surface of the water 19 is also critical in that it must be a method which does not adversely affiect the temperature gradient of the column of water 19 in the tank 5. The method employed must not, for instance, result in cooling of the water surrounding the wax nozzles at the bottom of the water column. WHAT WE CLAIM .IS:--

1. A method of producing beads from molten or thermoplastic material including the steps of: releasing discrete droplets of said material within a body of a denser liquid; maintaining the liquid in the zone of release of the material at a temperature equal to or higher than the melting point of the material; cooling the liquid in the upper zones of said body so that as the droplets of material rise they are cooled to form beads; and removing the beads from the surface of the liquid.

5. The method according to any one of

the preceding claims, wherein the beads are generally spherical and are between 0.001 and 10 mm in diameter.

6. Apparatus for the production of beads from molten or thermoplastic material including: a container for holding a liquid; an inlet in said container for conveying said material for release within the liquid; at least one belad-forming nozzle in a lower zone of said container connected to said inlet; means for maintaining a temperature gradient within said liquid such that the temperature of the liquid adjacent the nozzle exceeds the temperature at the surface; and means for removing beads from the surface of the liquid.

7. Apparatus according to claim 6, wherein a heater is provided within the container, ad jacent said nozzle.

8. Apparatus according to claim 7, wherein said heater is a steam ooil.

9. Apparatus according to any one of claims 6 to 8, wherein the means for removing beads, comprises: means for bleeding off said beads and a portion of slaid liquid; means for separating said beads and the bled off liquid; and means for drying said beads.

10. Apparatus according to claim 9, wherein said means for bleeding off slaid beads comprises a trough having a weir at one end, and nozzle means for issuing a fluid jet to drive the beads over the edge of the weir.

11. Apparatus according to claim 9 or 10, wherein the means for separating said beads from the bled off liquid comprises a separator having a baffle extending down into the separator, the beads being held on one side of the baffle, whilst the excess liquid is extracted from an cutlet on the other side of the baffle.

12. Apparatus according to any one of claims 9 to 11, wherein the means for drying said beads comprises an inclined tube having a perforated screen down which the beads roll, and means for passing air up through the perforations in the screen.

13. Apparatus according to any one ob claims 6 to 12, wherein the material is wax and the liquid is water.

14. The method of producing beads from molten or thermoplastic material a.s claimed in claim 1 substantially as herein described with reference to the accompanying drawing.

15. Apparatus for the production of beads from molten or thermoplastic material constructed substantially as herein described with reference to and as illustrated in the acc3mpanying drawing.