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(11) | EP 1 247 591 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of polymer removal, particularly for cleaning a mixing head or mixing machine |
| (57) A method of removing a polymer from an object, such as a part of a mixing device
comprises:
a) providing an aqueous solution containing a glucoside and a glycol, b) placing the solution in a chamber (15) to which air is supplied under pressure so that said solution is caused to flow along a line (33) leading to the object so as to impinge on the object, c) introducing air into the solution as it flows along said line so as to effect frothing of said solution prior to application thereof to the object, and d) continuing to supply air under pressure to said chamber after the solution has been discharged from the chamber so that, after the solution has been applied to the object, air under pressure is applied to the object to effect drying thereof. |
Field of the Invention
[0001] This invention relates to a method of polymer removal, particularly for cleaning a mixing head or mixing machine (hereinafter referred to generically as "a mixing device").
[0002] In industries where use is made of liquid polymers, there frequently arises a need to flush a mixing head of a mixing machine with a solvent. This is particularly the case in production processes in which moulds are filled in sequence by means of a mixing machine head which is flushed out following each mould filling to ensure that residual polymer containing accelerator is not left in the head with subsequent polymerisation leading to blockage.
[0003] The solvents which are currently employed are volatile organic solvents, such as ketones, which are environmentally unfriendly, expensive and hazardous.
[0004] It is accordingly an object of the present invention to provide a method of removing a polymer which is environmentally friendly.
[0005] A more specific objection of the present invention is to provide an improved method of cleaning a mixing device.
Summary of the Invention
[0006] According to the present invention there is provided a method of removing a polymer from an object, such as a part of a mixing device, the method comprising:-
a) providing an aqueous solution containing a glucoside and a glycol,
b) placing said solution in a chamber to which air is supplied under pressure so that said solution is caused to flow along a line leading to the object so as to impinge on the object,
c) introducing air into the solution as it flows along said line so as to effect frothing of said solution prior to application thereof to the object, and
d) continuing to supply air under pressure to said chamber after the solution has been discharged from the chamber so that, after the solution has been applied to the object, air under pressure is applied to the object to effect drying thereof.
[0007] The solution contained within the chamber is preferably as described in Patent Application No. WO 00/49095, to which reference should be made. Thus, the solution may contain 2.5 to 4.95% by weight of a glucoside, 0.1 to 2% by weight of a glycol compound and 0.1 to 2% by weight of a sodium compound. The advantages of using the combination of a glucoside and a glycol are explained in Patent Application No. WO 00/49095.
[0008] As applied to the cleaning of a mixing machine, a recycling system is preferably provided such that the solution used for effecting a cleaning operation is fed into a settling tank in which the catalysed resin delivered into the settling tank will become a sediment which will be retained by a filter screen whereas the filtered solution will be returned to the apparatus for re-use. The filter screen will preferably be removable from the settling tank so that the resin sediment can periodically be removed for disposal.
[0009] The aqueous solution containing the glucoside and the glycol is non-inflammable, bio-degradable and reusable thus providing substantial safety and cost-saving benefits as compared to the present methods used for removing polymers from mixing machines and the like.
Brief Description of the Drawing
[0010] The single figure of the accompanying drawing shows an apparatus which can be used for polymer removal, e.g. for cleaning a resin mixing machine.
Description of the Preferred Embodiment
[0011] The apparatus shown in the drawing includes a clean solvent container 7 within which there is an aqueous solution of a glucoside and a glycol. The aqueous solution is typically as described in PCT Application NO. WO 00/49095, to which reference should be made, and may thus contain:-
a) 2.5 to 4.95% by weight of a glucoside,
b) 0.1 to 2% by weight of a glycol, and
c) 0.1 to 2% by weight of a sodium salt.
[0012] The apparatus used for supplying the solution to the object is based on the apparatus shown in the single figure of the drawings of British Patent Specification No. 2 318 782 (to which reference should be made), but with the addition of a small air hole 9 (of the order of 1 mm. in diameter) in the delivery pipe 33 so that some of the air introduced via duct 32 passes directly into the delivery pipe 33 as opposed to being supplied to the chamber or vessel 15. As explained in British Patent Specification No. 2 318 782, a predetermined volume of liquid is delivered from the chamber or vessel 15 through the delivery pipe 33 on each cycle of operations of the apparatus. The apparatus thus includes a solvent pump 8 including a pressurisable vessel or chamber 15 immersed in the solution within the container 7.
[0013] The action of the solvent pump 8 is such that, after the predetermined volume of the cleaning solution has been delivered to the mixing device or other object to be cleaned, the operator continues to supply air under pressure along the air duct 32 and the delivery pipe 33 to the mixing device. The arrangement is thus such that, after the solution has been applied to the mixing device, air under pressure is applied to the mixing device to effect drying thereof.
[0014] The introduction of air into the solution through the air hole in the delivery pipe 33 will increase the velocity of the solution travelling along the pipe 33 so that a high speed froth is produced before it reaches the mixing device or other object to be cleaned.
[0015] The container 7 within which the vessel 15 is located contains a heater, for example, a 50 volt 50 to 100 watt heating element 10, so that the temperature of the solution can be raised to, for example, about 40° C.
[0016] A predetermined volume of the frothy solution is delivered at speed along the delivery pipe 33 to the mixing machine, or other object from which the resin or polymer is to be removed. The used volume of solution is then returned to a sediment tank 1 having a removable lid 2 with a drain fill point. The sediment tank 1 has a removable sealed base 3 and, within the sediment tank 1, there is a perforated baffle 4. The sizes of the perforations in the baffle 4 are such that any large resin particles will not be able to pass through the perforations and the large resin particles will settle to the base of the tank 1. Alongside (and spaced from) the baffle 4, there is a fine filter mesh screen 5 which serves to retain any other resin particles in the used solution and prevents the resin particles from passing to the side of the tank 1 at which there is a discharge outlet 6.
[0017] The discharge outlet 6 from the sediment tank 1 is arranged to plug into a corresponding inlet of the clean solvent container 7. Thus, when the level of the solvent in the sediment tank 1 reaches the level of the discharge outlet 6, the clean solvent, i.e. that which has passed through the fine filter mesh screen 5, will flow into the clean solvent container 7.
[0018] The sediment tank 1 will normally be removably connected to the clean solvent container 7 such that, once a predetermined amount of sediment has settled in the bottom of the tank 1, the sediment tank 1 will be replaced by a new sediment tank 1 and the sediment in the original tank 1 allowed to settle completely before any clean solvent is run off and the settled sediment is removed by detaching the base 3. The used sediment tank is then cleaned ready for reuse.
a) providing an aqueous solution containing a glucoside and a glycol,
b) placing said solution in a chamber to which air is supplied under pressure so that said solution is caused to flow along a line (33) leading to the object so as to impinge on the object,
c) introducing air into the solution as it flows along said line (33) so as to effect frothing of said solution prior to application thereof to the object, and
d) continuing to supply air under pressure to said chamber after the solution has been discharged from the chamber so that, after the solution has been applied to the object, air under pressure is applied to the object to effect drying thereof.