WO2009000275A2

WO2009000275A2 - A method of treating a polymer item

Info

Publication number: WO2009000275A2
Application number: PCT/DK2008/050151
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: WO2009000275A3

Abstract

The invention relates to a method of treating at least one polymer item comprising treating the item(s) by liquid CO2 at a pressure of up to about 50 bars in a vessel, wherein the polymer item(s) is packed in a closed container during the treatment. The closed container comprises a wall wherein at least 10 % of the area thereof is porous wall section which is permeable to liquid CO2. The porous wall section has a pore size of up to about 500 μm. By the method polymer items can be treated by liquid CO2 in packed or pre-packed condition. Thereby the item(s) will be protected against recontamination.

Description

A METHOD OF TREATING A POLYMER ITEM

BACKGROUND OF THE INVENTION

The present invention relates to a method of treating an item of a polymer comprising undesired residuals which are dissolvable in CO2, 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 items 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 beneficially be performed in a rotating drum. WO 06/045320 describes a method where a plurality of substrates war treated in a nylon bag for simply handling. After the treatment the treated substrates are packed in a packing material for avoiding re-contamination. The CO2 treatment is in general a relatively clean process and as described in WO 06/045320, it has further been found that the CO2 treatment may have a sterilizing effect on the treated items.

CO2 is primarily used for cleaning processes at high pressure about 73 bars and above where the CO2 is in its supercritical state or near supercritical state (when the temperature is below the supercritical temperature about 32 ⁰C.

CO2 in its supercritical state or near supercritical state is generally known as an effective cleaning solvent in particular when pulsed or when energized e.g. by a simultaneously treatment e.g. as described in US 5,344,493. However, it is well known that the properties of CO2 is highly dependant on its state and that CO2 in liquid state both in physical and in chemical aspects is incomparable to CO2 in its supercritical state or near supercritical state.

However, since it is very expensive to use CO2 in its supercritical state or near supercritical state, in particular due to the high requirements to the equipment, the inventor has found it desirable to develop methods for a effective treatment using liquid CO₂.

The inventors of the present invention have accordingly found new improvements which result in a liquid CO₂ treatment process which results in even more clean items.

The object of the invention is thus 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. According to the invention it has thus been found that by treating one or more polymer items according to the present invention very clean items can be obtained in a very simple way.

The method of the invention for treating at least one polymer item comprises treating the at least one item by liquid CO2 at a pressure of up to about 50 bars in a vessel, wherein the at least one polymer item is packed in a closed container during the treatment, where the container comprises a wall wherein at least 10 % of the area of said wall is a porous wall section which is permeable to liquid CO2, said porous wall section having a pore size up to about 500 μm.

Generally it is desired that the treatment is performed below the critical temperature of CO2. Preferably the treatment is kept below about 30 ⁰C.

All pore sizes mentioned herein may preferably be measured using by Bubble Point and Mean Flow Pore Test e.g. according to ASMT Method F316, for example F316-03 Standard "Test Methods for Pore Size Characteristics of Membrane Filters by Bubble Point and Mean Flow Pore Test", e.g. Test Method A and/or Test Method B.

Often the vessel 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 vessel. 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 several polymer items may be packed in individual containers or several items may be applied in one container.

The part of the wall which constitutes the porous wall section may in principle be the whole wall or any smaller parts thereof. The porous wall section may be provided in one segment of the wall or in two or more segments. For practical reasons it will often be desired that the porous wall section is in one continuous section.

In one embodiment the porous wall section constitutes at least 10 % by wall area of the total wall of the container. Preferably at least 20 %, such as at least 30 %, such as at least 40 %, such as at least 50 %, such as at least 60 %, such as at least 70 %, such as at least 80 %, such as at least 90 %, such as at least 95 %, such as essentially all of said wall is a porous wall section.

In practice it is most simple to provide the container such that the whole wall is the wall section, i.e. the container is made from one material sheet which is folded and fastened to form the container. The material sheet may for example comprise 1 , 2, 3 or more layers to provide the desired porosity.

In one embodiment the porous wall section has a pore size of up to about 400 μm, such as of up to about 300 μm, such as of up to about 200 μm, such as of up to about 150 μm, such as of up to about 100 μm, such as of up to about 50 μm, such as of up to about 10 μm, such as of up to about 1 μm.

The pore size(s) should preferably be sufficiently small to protect the polymer items within the container from being contaminated by undesired dirt. In one embodiment the pore size(s) of the porous wall section is sufficiently small to protect the polymer items within the container from being contaminated by dust generated by the treatment external to the container. In one embodiment the pore size(s) of the porous wall section is sufficiently small to protect the polymer items within the container from being contaminated by dirt and grease from hands, during the handling of the container. In one embodiment the pore size(s) of the porous wall section is even sufficiently small to protect the polymer items within the container from being contaminated by microorganism. In one embodiment the said porous wall section has a pore size of at least about 0.01 μm, such as at least about 0.1 μm, such as at least about 1 μm, such as at least about 5 μm, such as at least about 10 μm, such as at least about 50 μm.

The container may have pores of essentially the same size or the size of the pores may vary e.g. in a desired pattern. The pores may be evenly distributed in the porous wall section or the distribution may vary.

According to an embodiment of the method of the invention it has thus been found that the polymer item(s) may be packed in the container and treated according to the invention without risk of undesired contamination under loading and unloading of the vessel, even when the loading/unloading is performed manually.

The container may have any shape. Often it may be desired to shape the container such that it is adapted to the polymer items which should be treated according to the invention.

The size of the container may also be as desired, but preferably adapted to the polymer items to be treated. Thus in one embodiment the container has a volume which is at least 1.1 times the total volume of the polymer item (s) (the total volume of all the polymer items treated therein), such as preferably at least 1.2 times, such as at least 1.5 times, such as 2 to 25 times the total volume of the polymer item (s). Thereby the cleaning has shown to be very effective. The volume of the container may be adapted to contain 1 , 2, 3, or more polymer items such as up to 10000 polymer items, which polymer items may be identical or may differ in composition and/or in shape and/or in size.

In one embodiment the container is or comprises 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. In one embodiment the container comprises a cage covered by said wall e.g. in the form of a flexible layer coated onto the cage, e.g. a relatively stiff cage.

The container may in one embodiment be a bag preferably having essentially flexible walls. In principle any type and any size of bag having a porous wall section as described above may be used. The container may e.g. be a bag of the type which today is used in autoclaves, e.g. STERIKING Sterilisation Pouches marketed by WIPAK MEDICAL. As an example of other useful steriaisation bags the following can be mentioned: Breather Bags marketed by General Econopak, Inc, USA and LUKASTERIK sterilization bags marketed by OLSANSKE PAPIRNY a. s, Czech Republic

In one embodiment the container e.g. in the form of a bag is applied in a net or a cage, e.g. a net or a cage which may be used to fix the container in a rotary basket within the vessel as described in applicants co-pending application with the same priority date. 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.

The container should be a closed container which means that the container should preferably not have any openings into the container during the treatment which are larger than the pores described above. Preferably the only openings into the container during the treatment are the pores of the porous wall section. The container may be closed by any desired means such as by adhesive, by welding, by heat sealing, by Velcro, by stitching, by zipper(s), by tying or by any combinations thereof.

As described above the porous wall section may comprise 1 , 2, 3 or more layers to provide the desired porosity.

In one embodiment the porous wall section has a single material layer. In one embodiment the porous wall section comprises two or more layers. The two or more layers may be of the same or of different material. The two or more layers may for example be laminated to each other or they may be un-bonded.

The total layer of the wall should preferably be sufficiently large to provide the container with the desired strength for handling e.g. manually and/or by machines.

In one embodiment the porous wall section has a thickness of from 1 μm to 2 mm, such as from 10 μm to 1 mm, such as from 20-200 μm.

The one or more layer of the porous wall section may preferably comprise at least one layer of a material selected from the group consisting of paper, polymer and textile, such as linen.

In one embodiment the porous wall section comprises at least one layer of a polymer, preferably selected from the group consisting of olefin, such as poly ethylene (PE); polyamide (PA); aramid such as Kevlar®; Polyimide (Pl), polyester (PE), polyacrylate (PMMA), Poly phenylene-sulphide (PPS), Thermoplastic polyether (PET/PBT).

Other materials which are not dissolvable in liquid CO2 may also be used e.g. the type of materials which have also shown to be useful in autoclave bags/sterilisation bags.

In one embodiment the porous wall section comprises at least one woven layer. In one embodiment the porous wall section comprises at least one non-woven layer.

In one embodiment the porous wall section comprises at least one woven layer and at least one non-woven layer.

The vessel used for the treatment may in principle be any type of vessel which can be used for liquid CO2 treatment. Any of the methods and the vessels (reactors) described in WO 03/068846 and WO 06/045320 may be used in combination with the present invention which adds the additional features that the polymer item(s) are packed in a bag as defined in the claims during the treatment.

In one embodiment the method of the invention comprises treating said at least one item by liquid CO2 in a vessel comprising a rotary basket. The method of the present invention may in one embodiment be combined with the method described in applicants co-pending patent application filed simultaneously with this application, which method comprises fixing the container non-concentrically in the vessel, the method preferably comprising fixing said container to an annular wall of the rotary basket.

The polymer items may be any kind of polymer items. The method is in particular beneficial for treating polymer items of polymer comprising liquid residuals or solid residuals dissolvable in liquid CO2, 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 is cross-linked, preferably by a method from the group of condensation reaction, addition reaction, peroxide assisted reaction and mixtures thereof.

In one embodiment the method of the invention comprises

• providing at least one polymer item,

• providing the container

• applying the at least one polymer item in the container and sealing said container, • applying said container in said vessel and treating said polymer item(s) with liquid CO2 for a predetermined time, and

• withdrawing the container from said vessel.

According to the invention a method has been provided where the polymer item can be packed in the container during the whole CO2 treatment so that the polymer item(s) are packed in the container(s) while they are loaded into the vessel and while they are un-loaded from the vessel. In practice the polymer item(s) may be packed in the container(s) immediately after shaping or any time thereafter until immediately prior to loading into the vessel.

In one embodiment the item(s) are packed in said container within 24 hours after shaping, preferably within 12 hours, such as within 8 hours, such as within 4 hours, such as within 2 hours such as within 1 hour after shaping.

In one embodiment the item(s) are produced at a production site and packed in said container at said production site where they were shaped. This embodiment provides a highly beneficial method because very often the step of CO2 treating polymer items is provided by an external supplier. The factory producing the polymer item(s) can then assure that the polymer items are returned after the CO2 treatment in the same closed container(s). The packed polymer item(s) may then be transported to the CO2 treatment supplier, who treats the packed polymer item(s) and returns them still in packed condition.

Thus in one preferred embodiment the polymer item(s) are transferred from the production site to a remote location where the container(s) are applied in the vessel and the polymer item(s) are treated with liquid CO2. The container(s) may there after preferably be withdrawn from the vessel and transferred to a remote location in said sealed container(s).

The method of treating the polymer item(s) may for example be as described in WO 03/068846 and WO 06/045320 with the provision that the polymer item(s) are packed in a container as described herein. Other methods of CO2 treatment may also be used.

In one embodiment the treatment of said polymer item(s) comprises 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 treatment of the polymer item(s) exclude any simultaneously microwave treatment.

In one embodiment the treatment of the polymer item(s) exclude any simultaneously electromagnetic energy treatment. EXAMPLE

30 Moulded silicone items weighing approximately 3 grams were produced.

The items were split into three groups. Group A (10 items) put in a commercial sterilisable bag (name: steriking). Group B (10 items) used as first reference items. Group C (10 items) used as second reference items.

Groups A and B were applied in a rotary basket of a vessel and treated by CO2 Treatment parameters:

Pressure 42-50 bars

Temperature 8-15°C

Treatment time 35 minutes

Rotation 15 rotations/minutes

Result (volatile content measured according to EN 14350-2) - all results %w/w

Group C - not treated: average: 1.14% std. dev. 0.03% Group B - not in sterilisable bag: Average: 0.22% std. dev 0.01 % Group A - inside sterilisable bag: average: 0.23% std. dev. 0.01 %

As it can clearly be seen, the extraction of residuals due to the CO2 treatment is not affected by the packing of the polymer items as according to the method of the invention.

Claims

1. A method of treating at least one polymer item comprising treating said at least one item by liquid CO2 at a pressure of up to about 50 bars in a vessel, wherein said at least one polymer item is packed in a closed container during the treatment, where the container comprises a wall wherein at least 10 % of the area of said wall is a porous wall section which is permeable to liquid CO2, said porous wall section having a pore size of up to about 500 μm.

2. A method as claimed in claim 1 wherein at least 20 %, such as at least 30 %, such as at least 40 %, such as at least 50 %, such as at least 60 %, such as at least 70 %, such as at least 80 %, such as at least 90 %, such as at least 95 %, such as essentially all of said wall is a porous wall section.

3. A method as claimed in any one of claims 1 and 2 wherein said porous wall section has a pore size of up to about 400 μm, such as of up to about 300 μm, such as of up to about 200 μm, such as of up to about 150 μm, such as of up to about 100 μm, such as of up to about 50 μm, such as of up to about 10 μm, such as of up to about 1 μm.

4. A method as claimed in any one of claims 1 , 2 and 3 wherein said porous wall section has a pore size of at least about 0.01 μm, such as at least about 0.1 μm, such as at least about 1 μm, such as at least about 5 μm, such as at least about 10 μm, such as at least about 50 μm.

5. A method as claimed in any one of the preceding claims wherein the container comprises a cage covered by said wall, said cage preferably being relatively stiff.

6. A method as claimed in any one of the preceding claims 1-4 wherein the container is a bag, the wall of said bag preferably being essentially flexible.

7. A method as claimed in any one of the preceding claims wherein said porous wall section is a single layer material.

8. A method as claimed in any one of the preceding claims 1-6 wherein said porous wall section comprises two or more layers, said two or more layers being of the same or of different material and optionally being laminated.

9. A method as claimed in any one of the preceding claims wherein said porous wall section comprises at least one layer of a material selected from the group consisting of paper, polymer and textile, such as linen.

10. A method as claimed in any one of the preceding claims wherein said porous wall section comprises at least one layer of a polymer, preferably selected from the group consisting of olefin, such as poly ethylene (PE); polyamide (PA); aramid such as Kevlar®; Polyimide (Pl), polyester (PE), polyacrylate (PMMA), Poly phenylene-sulphide (PPS), Thermoplastic polyether (PET/PBT).

11. A method as claimed in any one of the preceding claims wherein said porous wall section comprises at least one woven layer.

12. A method as claimed in any one of the preceding claims wherein said porous wall section comprises at least one non-woven layer.

13. A method as claimed in any one of the preceding claims wherein said porous wall section has a thickness of from 1 μm to 2 mm, such as from 10 μm to

1 mm, such as from 20-200 μm.

14. A method as claimed in any one of the preceding claims comprising treating said at least one item by liquid Cθ₂ in a vessel comprising a rotary basket.

15. A method as claimed in claim 14 wherein said method comprises fixing said container non-concentrically in said vessel, the method preferably comprising fixing said container to an annular wall of the rotary basket.

5 16. A method as claimed in any one of the preceding claims, said method comprising providing said at least one polymer item, providing said container applying said at least one polymer item in said container and sealing said 10 container, applying said container in said vessel and treating said polymer item(s) with liquid CO2 for a predetermined time, and withdrawing said container from said vessel.

15 17. A method as claimed in claim 16 wherein said at least one polymer item is shaped preferably by moulding, such as compression moulding, transfer moulding or injection moulding; extrusion, blowing or combinations thereof.

18. A method as claimed in any one of claims 16 and 17 wherein said item(s) 20 are packed in said container within 24 hours after shaping, preferably within 12 hours, such as within 8 hours, such as within 4 hours, such as within 2 hours such as within 1 hour after shaping.

19. A method as claimed in any one of claims 16, 17 and 18 wherein said 25 item(s) are produced at a production site and packed in said container at said production site where they were shaped.

20. A method as claimed in claim 19 wherein the polymer items are transferred from the production site to a remote location where the container is applied in the

30 vessel and the polymer item(s) are treated with liquid CO2.

21. A method as claimed in any one of claims 16-20 wherein the container after being withdrawn from the vessel is transferred to a remote location in said sealed container.

22. 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.

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

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;

25. A method as claimed in claim 24, wherein the polymer item being 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 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.

26. A method as claimed in claim any one of claims 24 and 25 wherein said silicone rubber is cross-linked, preferably by a method from the group of condensation reaction, addition reaction, peroxide assisted reaction and mixtures thereof.

27. 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 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.

28. A method as claimed in any one of the preceding claims wherein said treatment of said polymer item(s) exclude any simultaneously microwave treatment.

29. A method as claimed in any one of the preceding claims wherein said treatment of said polymer item(s) exclude any simultaneously electromagnetic energy treatment.