WO2009000274A2

WO2009000274A2 - A method of treating a polymer item, and a vessel for performing the method

Info

Publication number: WO2009000274A2
Application number: PCT/DK2008/050150
Authority: WO
Inventors: Jan Damgaard; Mikkel Petersen; Anne Marie Jensen
Original assignee: Nanon A/S
Priority date: 2007-06-22
Filing date: 2008-06-17
Publication date: 2008-12-31
Also published as: WO2009000274A3

Abstract

The invention relates to a method of treating at least one polymer item comprising treating said at least one item by liquid CO2 in a vessel comprising a rotary basket. The method comprises - providing at least one polymer item, - applying the item(s) in a container, - fixing the container non-concentrically in the rotary basket, - closing the vessel and treating the polymer item(s) with liquid CO2 under at least partial rotation of the basket with a rotation axis which is substantially horizontal or up to about 45 degree from a horizontal plane for a predetermined time. By the method a very homogenous extraction of residuals can be obtained.

Description

A METHOD OF TREATING A POLYMER ITEM, AND A VESSEL FOR PERFORMING THE METHOD

BACKGROUND OF THE INVENTION

The present invention relates to a method of treating an item of a polymer comprising liquid and other residuals, such as a silicone rubber item, such as a medical item or other polymer items where high quality is desired.

Silicone rubber has been used in a variety of fields as medical instruments, building materials, electric and electronic parts, automotive parts, and business machine parts because of its superior properties including physiological inertness (non-toxicity), weather resistance, durability, release properties, and heat resistance.

Silicone rubber item may today be produced in many ways using various starting materials and tempering systems. US 5519082 discloses a silicone rubber composition that cures through hydrosilylation. This reaction type is known as the addition tempering type. US 5973030 discloses production of liquid silicone rubber compositions. EP 384 609 and US 6020449 disclose single-component silicone rubber mixtures (RTV1 ) which readily cure simply by heating, leading to a very high production yield. Two component silicon rubbers are also very popular.

WO 03/068846 and WO 06/045320 owned by applicant describe methods for treating silicone items by subjecting them to CO2 in liquid and or supercritical form.

As described therein the treatment may beneficial be performed in a rotating drum.

US 2003/0205510 discloses a method for treating a substrate by compressed CO2 in a rotating drum, where the drum may be oriented between the horizontal and vertical planes for improved process capability. The publication describes a tumbling method where substrates are mixing bi-directionally under predominantly gravitational force, and are sliding over one another, predominantly in a segmented upper layer, as the barrel rotates slowly about a central axis in a rotatable drum in the horizontal plane. The rotational velocity is maintained purposefully slow to prevent the substrates from damaging one another during mixing within the barrel compartment, but allows the dense fluid to flow freely at lower fluid shearing velocity around and through the substrates. The Dense Fluid Tumbling process described creates only one dense fluid zone — (1 ) a semi- turbulent cleaning zone located below the centre of the barrel compartment to the lower half of the barrel.

In order to reduce cost it is desired to use CO2 in liquid state, which generally means that the treatment reactor can operate at pressures not exceeding 50 bars. It has however been found that a liquid CO2 treatment of polymer items may result in an uneven treatment, which may result in a prolonged treatment time to ensure that all item surfaces have been treated sufficiently.

The object of the invention is to provide a method which results in an improved liquid CO2 treatment of polymer items.

DESCRIPTION OF THE INVENTION

The method of the invention is as defined in the claims and as described herein below, and includes treating by liquid CO2 a polymer item in a non-vertically arranged rotating basket where the polymer item is placed in a container which is non-concentrically fixed to the rotary basket.

According to the invention it has thus been found that by treating one or more polymer items according to the present invention an even extraction of liquid residuals and other residuals may be obtained even when several polymer items are treated simultaneously.

Also it has surprisingly been found that by fixing the polymer item containing container non-concentrically to the rotary basket the homogeneity in extraction may result in a total cleaning effect which is improved compared to when loosely placing the polymer item in the rotary basket. Furthermore it has been found that the amount of polymer item treated in the same rotary basket may be increased without decreasing the cleaning effect.

Often the rotary basket has a volume which is much larger than the size of the polymer item, and naturally for cost reasons it is desired to treat several items, such as 5 or more, such as 10 or more, such as 100 or more polymer items simultaneously in the same rotary basket. According to the invention the method may thus comprise treating such several items simultaneously. The several polymer items treated simultaneously may have the same shape and/or size or they may differ in size and shape from each other.

The method of the invention comprises treating said at least one item by liquid CO₂ in a vessel comprising a rotary basket.

The treatment by liquid CO2 should preferably be provided to obtain an extraction of liquid residuals and other residuals from the polymer item(s). In principle the liquid CO2 may be at any pressure and any temperature provided that during the treatment it is in liquid state. The pressure and/or the temperature may be regulated and/or changed during the treatment e.g. by pulsating the pressure such as it is known from the prior art. Further information about the desired conditions during the treatment which may be used in combination with the present invention are described in WO 03/068846 and WO 06/045320.

As also described in WO 03/068846 and WO 06/045320 the polymer items may also be treated with other components simultaneously with the treatment with CO2, such at other solvent(s), and surfactants as well as impregnating compounds such as pigments and other.

In one embodiment the method of the invention may comprise subjecting the polymer item(s) to an extraction treatment using carbon dioxide comprising a solvent at a pressure between 10 and 50 bars, wherein the item has an initial temperature below 60 °C in the extraction treatment, and in at least a part of the extraction time the item has a temperature below 25 °C and a pressure so that the carbon dioxide is in its liquid state.

In one embodiment the method of the invention may comprise feeding the polymer item(s) into the rotary basket according to the invention, and subjecting the injection moulded item to an extraction treatment using carbon dioxide containing solvent at a pressure between 10 and 50 bars, wherein the item has an initial temperature below 60 °C in the extraction step, and in at least a part of the extraction time the item has a temperature below 25 °C and a pressure between 10 and 50 bars so that the carbon dioxide is in its liquid state.

The vessel should preferably be essentially closed during the treatment except for feeding lines and draining lines which can be closed and/or opened to provide the desired treatment conditions in the rotary basket. The vessel should further have an opening for introducing and withdrawing the polymer item(s) to be treated e.g. in their container(s). The opening comprises a closable element such as a door.

The rotary basket may preferably comprise an annular wall which is perforated by one or more openings. The openings should preferably be sufficiently large for allowing an essentially free passage of the CO2 e.g. in liquid form. In one embodiment the openings may have a size which is between 0.1 μm² and 5 cm², such as between 1 μm² and 1 cm². The annular wall may preferably have a plurality of openings, such as 20 or more, such as 50 or more, such as 100 or more. The openings may preferably be evenly distributed e.g. in a periodic pattern.

The rotary basket may preferably comprise an annular wall with an inner side (referred to as the inner annular wall) and an outer side (referred to as the outer annular wall). The rotary basket may preferably have a rotation axis which - at least for a predetermined rotation time - is substantially horizontal or up to about 45 degree from a horizontal plane. The rotation axis may be varied so that the rotation axis in one embodiment comprises one or more of the rotation axisvertical, horizontal and angled in any angle there between. In one preferred embodiment the rotary basket has an essentially horizontal rotation axis during at least a part of the treatment. In one preferred embodiment the rotary basket has an essentially horizontal rotation axis during the whole treatment.

The rotary basket may be of any material which has the necessary physical and chemical strength to withstand the method. In one embodiment the rotary basket is a metal basket, preferably made from steel, such as duplex steel.

In one embodiment the rotary basket comprises an annular wall, which annular wall is angular. The angularity may be provided on the inner annular wall, on the outer annular wall or on both of the inner and the outer annular walls. The angularity may preferably be in the form of at least one angle line (e.g. forming an edge) extending essentially parallel to the rotation axis. The at least one angle line preferably extends in essentially the whole length of the annular wall, where the length is measured in the direction parallel to the rotation axis.

In one embodiment the rotary basket comprises an annular wall comprising at least four angles, such as at least six angles, such as at least eight angles, such as at least ten angles, such as at least twelve angles along its inner annular periphery, the at least four angles preferably being in the form of angle lines extending essentially parallel to the rotation axis.

In one embodiment the rotary basket is essentially cylindrical.

The rotary basket may in one embodiment consist essentially of the annular wall without any end sections. In one embodiment the rotary basket comprises a back end wall. In one embodiment the rotary basket comprises a front end wall. The front end wall comprises an opening for introducing and withdrawing the polymer item(s) to be treated. The opening comprises a closable element such as a door. In one embodiment the rotary basket comprises an annular wall and a first and a second end wall wherein the second end wall comprises an opening for inserting and withdrawing the container.

The container may in principle be any kind of container which can be penetrated by the liquid CO2 under the treatment and which can be fixed to the rotary basket. The container should preferably be fixed directly to the inner side or elements placed on the inner side of the rotary basket, but in principle any other fixing arrangement may be applied e.g. fixing by straps or similar extending outside the rotary basket volume.

In one embodiment the rotary basket comprises an annular wall, the method comprising fixing the container or containers to the annular wall of the rotary basket, preferably fixing the container(s) to the inner side of the annular wall of the rotary basket.

The container may for example be fixed directly to the annular wall of the rotary basket or the container may be fixed via one or more holding elements, such as a bar or a lug mounted onto the inner side of the annular wall of the rotary basket or other how fixed to the inner side of the annular wall of the rotary basket. In one embodiment the container may be fixed via one or more holding elements including a hook and/or a snap element such as a carbine hook.

In one embodiment the container is fixed to a holding element which is fixed to the annular wall of the rotary basket.

In one embodiment two or more containers are fixed to the same holding element.

The container may be any kind of container which can contain the polymer item(s) and which can be penetrated by the liquid CO2.

In one embodiment the container is a cage, preferably having relatively stiff walls. Such cage with relative stiff walls may be simple to handle and simple to stack. Furthermore the cage may be provided for specific polymer items to thereby make it simple to load and unload.

The cage with relatively stiff walls may also be simple to load and fix to the rotary basket. In one embodiment the cage has a length which is longer than half of the length of the rotary basket and shorter or equal to the length of the rotary basket, where the length of the rotary basket is the maximal inner dimension of the rotary basket measured parallel to its rotation axis. Where the length of the rotary basket is relatively large e.g. 1 m or more, it may be difficult to fix the basket in the part of the rotary basket which is further away from the opening into the rotary basket.

This will, however, be more simple when the cage has a length which is not too short e.g. as described above.

The container may in one embodiment be a bag preferably having essentially flexible walls. In principle any type and any size of bag may be used. The bag should preferably be sufficiently locked e.g. by a flap, a zipper by a Velcro lock or lock to avoid polymer item falling out of the bag.

The container may in one embodiment be a net. The net may preferably be fixed to the rotary basket at 2 or more locations, preferably 3 or more locations, such as

4 or more locations to thereby provide a sufficient fixing of the container to be non- concentrically arranged in the rotary basket. For simple handling the net may be prefixed to the inner side of the rotary basket at 2 or more locations prior to application of the polymer item(s). The polymer items may be applied e.g. by stretching the net, where after, if necessary, the net may be fixed to the rotary basket at one or more additional locations.

In one embodiment the polymer item(s) are applied in a first container e.g. a bag where after it is fixed to the rotary basket by a second container e.g. in the form of a net. The container may in principle have any volume provided that it is arranged non- concentrically in the rotary basket. In other words, the volume of the container should preferably be significantly less than the volume of the rotary basket.

In one embodiment the container has a volume which is up to about 50 % of the volume of the basket, such as between 1 and 40 % of the volume, such as 2 to 30 % of the volume, such as between 5 and 25 % of the volume of the basket.

In one embodiment the container has a plurality of apertures which apertures have an average area of from 0.1 μm² to 100 cm², such as from 1 μm² to 10 cm², such as from 10 μm² to 5 cm², such as from 0.1 mm² to 1 cm², such as from 1 - 5 mm². The area of the various apertures may be essentially equal or they may differ.

In one embodiment the container has a mesh size of A x B, wherein A and B individually of each other are from 0.1 μm to 100 cm, such as from 1 μm to 10 cm, such as from 10 μm to 5 cm, such as from 0.1 mm to 2 cm, such as from 1 - 10 mm.

The mesh size A x B is measured as the distance between two adjacent first parallel wires or threads (A) x the distance between two adjacent second parallel wires or threads (B), where the first wires or threads cross the second wires or threads.

The polymer items may be any kind of polymer items. The method is in particular beneficial for treating polymer items of polymer comprising residuals, such as liquid residuals, such as polymer item(s) of a polymer selected from silicone rubber, such as functionalized silicone rubber, such as RTV- 1 silicone rubbers, RTV-2 silicone rubbers and HTV silicone rubbers.

The method may, however, also be highly beneficial for removing dust polymer item(s), for impregnating polymer item(s) and/or for sterilization or semi sterilization of polymer item(s). The method is highly beneficial for treating polymer silicon rubber item(s) made from a precursor silicon mixture comprising one or more silicone components, preferably said precursor silicon mixture comprises one or more of the silicone components selected from the group consisting of dialkylsilicone elastomers wherein alkyl means hydrocarbon side groups of 1-12 carbon atoms such as methyl, ethyl, hexyl, and octyl; vinyl silicone elastomers; phenyl silicone elastomers; nitrile silicone elastomers; fluorosilicone elastomers, room temperature vulcanising (RTV) silicone elastomers; liquid silicone elastomers (LSR); borosilicone elastomers; the precursor silicon mixture preferably comprises dimethyl silicone elastomers.

The polymer item(s) may be shaped by any means such as by moulding, such as compression moulding, transfer moulding or injection moulding; extrusion, blowing or combinations thereof.

In one embodiment the silicone rubber being cross-linked, preferably by a method from the group of condensation reaction, addition reaction, peroxide assisted reaction and mixtures thereof.

The method of the invention comprises fixing one or more containers non- concentrically in the rotary basket. The term non-concentrically means that the container should not be placed concentrically with the centre in the rotation axis of the rotary basket. Preferably the container is fixed such that the container does not extend to the rotation axis of the container.

It has been found that the fixing of the polymer item(s) in one or more container also result in less damage of the respective items.

In one embodiment the one or more containers is/are fixed non-concentrically in the rotary basket such that it/they is/are in a distance from the rotation axis, preferably a distance rotation axis of 1 cm or more, such as 5 cm or more, such as 10 cm or more.

In one embodiment the one or more containers is/are fixed non-concentrically in the rotary basket such that it/they is/are lying directly adjacent to the inner wall of the rotary basket.

The treatment is performed under at least partial rotation of the basket for a predetermined time.

The predetermined time may be e.g. as described in WO 03/068846 and WO 06/045320.

According to the method of the invention the said polymer item(s) may preferably be treated with liquid CO2 under full rotation of the rotary basket for a predetermined time. The basket preferably rotates with a frequency of between 1 and 300 rotations/minutes, such as between 5 and 100, such as preferably up to 50, e.g. from 10 to 20.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other stated features, integers, steps, components or groups thereof.

The invention also relates to a vessel for treating at least one polymer item by liquid CO2. The vessel of the invention comprises a rotary basket with a rotation axis which is substantially horizontal or up to about 45 degree from a horizontal plane, and comprising an annular wall which is perforated, preferably by a plurality of openings, and at least one holding element preferably in the form of bar or a lug fixed to said annular wall of the rotary basket.

The vessel may further be as described above. BRIEF DESCRIPTION OF DRAWINGS

The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

FIG. 1 is a picture of the front of a vessel with a rotary basket.

FIG. 2 is a picture of the front of the vessel of fig. 1 with a first container.

FIG. 3 is a picture of the front of the vessel of fig. 1 with a second container.

FIG. 4 is a picture of the front of the vessel of fig. 1 with a third container.

FIG. 5 is a picture of the front of another vessel with a rotary basket and several containers.

Fig. 1 shows the front of a vessel 1 with a rotary basket 2. The rotary basket 2 has an annular wall 3 with a back end wall 4. Both the annular wall 3 and the back end wall 4 are perforated by openings 5. Onto the inner side of the annular wall are fixed holding elements 6, in the form of bars 6. The rotary basket 2 is also equipped with another type of holding elements 7 in the form of lugs 7 fixed to the inner side of the annular wall 3 of the rotary basket 2.

Fig. 2 shows the front of the same vessel 1 into which a container 11 , in the form of a net 11 , has been fixed by the help of not shown additional holding elements, which have been fixed to the bars 6. As it can be seen, the net 11 further comprises additional holding elements 12 for fixing to the lugs 7 mounted within the rotary basket. In the shown picture the net 11 is empty, but when used according to the method of the invention the polymer item(s) should be filled into the space formed between the inner side of the annular wall 3 of the rotary basket 2 and the net 11 , preferably prior to fixing the additional holding elements 12 to the lugs 7. Fig. 3 shows the front of the same vessel 1 into which a container 21 , in the form of a cage 21 , has been fixed to the lugs 7 which cannot bee seen in this picture. The cage 21 has a length which is almost the length of the rotary basket measured parallel to the rotation axis of the rotary basket 2.

Fig. 4 shows the front of the same vessel 1 into which a container 31 , in the form of a bag 31 , has been fixed by the help of additional holding elements 32 in the form of carbine hooks 32. In the shown picture the bag 31 is empty, but when used according to the method of the invention the polymer item(s) should be filled into the bag 31 preferably prior to mounting it in the rotary basket 2.

Fig. 5 shows the front of another vessel 40 having a rotary basket 42 into which 4 containers 41 in the form of nets 41 , have been fixed by the help of not shown holding elements. The rotary basket 42 has a back end wall 44 which is perforated by openings 45. Additional containers in the form of bags 43 have been fixed in the space formed between the inner side of the annular wall of the rotary basket 42 and the respective nets 41. The not shown polymer items are applied in the bags 43.

The figures are schematic and simplified for clarity, and they just show details which are essential to the understanding of the invention, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts.

Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims.

Claims

1. A method of treating at least one polymer item comprising treating said at least one item by liquid CO2 in a vessel comprising a rotary basket, said method comprising providing said at least one polymer item, applying said at least one item in a container, fixing said container non-concentrically in said rotary basket, closing the vessel and treating said polymer item(s) with liquid CO2 under at least partial rotation of said basket with a rotation axis which is substantially horizontal or up to about 45 degree from a horizontal plane for a predetermined time.

2. A method as claimed in claim 1 wherein the rotary basket comprises an annular wall which is perforated, preferably by a plurality of openings.

3. A method as claimed in any one of claims 1 and 2 wherein the rotary basket comprises an annular wall which annular wall is angular and comprises preferably at least four angles along its inner annular periphery.

4. A method as claimed in any one of claims 1 and 2 wherein the rotary basket is essentially cylindrical.

5. A method as claimed in any one of the preceding claims wherein the rotary basket comprises an annular wall and a first and a second end wall wherein the second end wall comprises an opening for inserting and withdrawing the container.

6. A method as claimed in any one of the preceding claims wherein the rotary basket is a metal basket, preferably made from steel, such as duplex steel.

7. A method as claimed in any one of the preceding claims wherein the rotary basket has an essentially horizontal rotation axis.

8. A method as claimed in any one of the preceding claims wherein the container is a cage, preferably having relatively stiff walls.

5 9. A method as claimed in claim 8 wherein the cage has a length which is longer than half of the length of the rotary basket and shorter or equal to the length of the rotary basket, where the length of the rotary basket is the maximal inner dimension of the rotary basket measured parallel to its rotation axis.

10 10. A method as claimed in any one of the preceding claims 1-8 wherein the container is a bag, preferably having essentially flexible walls.

11. A method as claimed in any one of the preceding claims 1-8 wherein the container is a net, the net preferably being fixed to the basket at 2 or more

15 locations, such as preferably 3 or more locations.

12. A method as claimed in any one of the preceding claims wherein the container has a volume which is up to about 50 % of the volume of the basket, such as between 1 and 40 % of the volume, such as 2 to 30 % of the volume,

20 such as between 5 and 25 % of the volume of the basket.

13. A method as claimed in any one of the preceding claims wherein the container has a plurality of apertures having an average area of from 0.1 μm² to 100 cm², such as from 1 μm² to 10 cm², such as from 10 μm² to 5 cm², such as

25 from 0.1 mm² to 1 cm², such as from 1 - 5 mm².

14. A method as claimed in any one of the preceding claims wherein the container has a mesh size of A x B, wherein A and B individually of each other are from 0.1 μm to 100 cm, such as from 1 μm to 10 cm, such as from 10 μm to 5 cm,

30 such as from 0.1 mm to 2 cm, such as from 1 - 10 mm.

15. A method as claimed in any one of the preceding claims wherein the rotary basket comprises an annular wall, the method comprising fixing said container to said annular wall of the rotary basket.

16. A method as claimed in claim 15 wherein said container is fixed directly to said annular wall of the rotary basket.

17. A method as claimed in claim 15 wherein said container is fixed to a holding element which being fixed to said annular wall of the rotary basket.

18. A method as claimed in claim 17 wherein two or more containers are fixed to said holding element.

19. A method as claimed in any one of claims 15-18 wherein said container is fixed such that is does not extend beyond the rotation axis of the rotary basket.

20. A method as claimed in any one of the preceding claims wherein the at least one polymer item is shaped preferably by moulding, such as compression moulding, transfer moulding or injection moulding; extrusion, blowing or combinations thereof.

21. A method as claimed in any one of the preceding claims wherein the method comprises treating a plurality of polymer items, wherein the polymer items may be identical or non-identical in shape and/or material.

22. A method as claimed in claim 21 comprising applying a plurality of polymer items in said container.

23. A method as claimed in any one of claims 21 and 22 comprising fixing a plurality of containers non-concentrically in said rotary basket.

24. A method as claimed in any one of the preceding claims wherein the at least one polymer item is of a polymer selected from silicone rubber, such as functionalized silicone rubber, such as RTV- 1 silicone rubbers, RTV-2 silicone rubbers and HTV silicone rubbers.

5

25. A method as claimed in claim 24, wherein the polymer item is of a silicon rubber item made from a precursor silicon mixture comprising one or more silicone components, preferably said precursor silicon mixture comprises one or more of the silicone components selected from the group consisting of dialkylsilicone

10 elastomers wherein alkyl means hydrocarbon side groups of 1 -12 carbon atoms such as methyl, ethyl, hexyl, and octyl; vinyl silicone elastomers; phenyl silicone elastomers; nitrile silicone elastomers; fluorosilicone elastomers, room temperature vulcanising (RTV) silicone elastomers; liquid silicone elastomers (LSR); borosilicone elastomers; the precursor silicon mixture preferably comprises

15 dimethyl silicone elastomers.

26. A method as claimed in any one of the preceding claims wherein said treatment of said polymer item(s) comprises subjecting the polymer item(s) item to an extraction treatment using carbon dioxide comprising solvent at a pressure

20 between 10 and 50 bars, wherein the item has an initial temperature below 60 °C in the extraction treatment, and in at least a part of the extraction time the item has a temperature below 25 °C and a pressure so that the carbon dioxide is in its liquid state.

25 27. A method as claimed in any one of the preceding claims comprising treating said polymer item(s) with liquid CO2 under full rotation of said basket for a predetermined time, the basket preferably rotates with a frequency of between 1 and 300 rotations/minutes, such as between 5 and 100, such as preferably up to 50, e.g. from 10 to 20.

30

28. A vessel for treating at least one polymer item by liquid CO2, said vessel comprises a rotary basket with a rotation axis which is substantially horizontal or up to about 45 degree from a horizontal plane, and comprising an annular wall which is perforated, preferably by a plurality of openings, and at least one holding element preferably in the form of a bar or a lug fixed to said annular wall of the rotary basket. 5

29. A vessel as claimed in claim 28 wherein the rotary basket comprises an annular wall which annular wall is angular and comprises preferably at least four angles along its inner annular periphery.

10 30. A vessel as claimed in any one of claims 28 and 29 wherein the rotary basket is essentially cylindrical.

31. A vessel as claimed in any one of the preceding claims wherein the rotary basket has an essentially horizontal rotation axis. 15