WO2009124122A2

WO2009124122A2 - High viscosity siliconization methods

Info

Publication number: WO2009124122A2
Application number: PCT/US2009/039138
Authority: WO
Inventors: Thomas Klumpen; Andre Janssen
Original assignee: West Pharmaceutical Services, Inc.
Priority date: 2008-04-02
Filing date: 2009-04-01
Publication date: 2009-10-08
Also published as: WO2009124122A3

Abstract

Siliconization methods are provided for uniformly siliconizing a component with high viscosity silicone oil. A silicone blend is initially formed from a high viscosity silicone oil and a low viscosity liquid. A silicone emulsion is then formed with the silicone blend and a carrier liquid. Components are then coated with the silicone emulsion. The carrier liquid and low viscosity liquid are then removed from the silicone emulsion coating on the components thereby leaving a substantially uniform coating of high viscosity silicone oil on the surfaces of components.

Description

TITLE OF THE INVENTION [0001] High Viscosity Siliconization Methods

BACKGROUND OF THE INVENTION

[0002] The present invention generally relates to a siliconization process. In particular, the present invention relates to a siliconization process using an emulsion that includes high viscosity silicone oil.

[0003] Silicones, or polymerized siloxanes or polysiloxanes, are mixed inorganic-organic polymers. Silicones can be polymerized to various molecular weights to vary their physical and chemical properties, such as their kinematic and dynamic viscosities. Common silicone oils applicable to the present invention include, but are not limited to, polydimethylsiloxanes.

[0004] Siliconization processes generally provide a surface coated with a layer of silicone oil to provide, for example, lubricity to the coated object. Siliconization processes are used in a wide variety of applications, including various medical devices, such as in the coating of elastomeric or rubber components. Such rubber components are used in medical devices such as syringes, collection devices, and intravenous systems. However, conventional siliconization processes are problematic in that it is very difficult to provide for a defined amount of silicone on the components based upon a dosage of a defined amount of silicone oil in such siliconization processes. Thus, the silicone oil used in such conventional siliconization processes adheres easily to various components of the siliconization process itself, such as hoses and chamber interiors. As a result, this leads to inconsistent silicone oil levels on finished coated products/components. Moreover, silicone oils with high viscosities, due to the high viscosity nature of the silicone oil, cannot be readily formed into an emulsion in an appropriate carrier liquid (i.e., continuous phase), and therefore cannot be readily used in an emulsion based coating process.

[0005] Siliconized components, i.e., components coated with a silicone oil, are typically coated with a silicone oil having a kinematic viscosity of about 1,000 centistokes (cSt). Higher viscosity silicone oils, e.g., on the order of about 12,500 cSt, have not typically been used in such applications due to difficulties in the siliconization process with such high viscosity silicone oils. That is, due to the high viscosity of the silicone oil itself, it is difficult to uniformly and homogenously coat components with such silicone oils. For example, if the siliconization process uses an emulsion, such high viscosity silicone oils cannot be easily emulsified, if at all. As a result, this can lead to a non-homogenous silicone oil coating which can adversely affect surface properties of the coated components, such as adhesion, friction, and/or particle debris generation. In addition, low viscosity silicone oils, e.g., on the order of about 0.1 to 200 cSt, have also not been typically used in siliconization processes due to their high volatility and flammability. Such high volatility and flammability of low viscosity silicone oils can lead to, among other things, safety issues such as risk of explosions.

[0006] Silicone oils having a viscosity in the range of about 1 ,000 cSt also have various drawbacks, such as the formation of subvisible particles on coated surfaces due to coalescence of the silicone oil. As a result, products coated with these silicone oils fail to pass certain quality requirements, such as the Chinese Pharmacopeia which specifies very stringent limitations concerning subvisible particles on products. Moreover, these subvisible particles can contaminate fluids in contact with the siliconized parts. This is problematic where the fluids are drugs or biological fluids, such as blood serum samples, to be analyzed, as the subvisible particles may cause turbidity in the drugs or interactions with the fluid sample analyzers.

[0007] In addition, the application of 1,000 cSt silicone oil in certain cases can provide excessive lubrication to a part surface, which may negatively affect the part's function in a device. For example, in manufacturing medical syringes, needle shields coated with 1,000 cSt silicone oil often result in pull-off forces for the needle shield that are too low. The use of about 1,000 cSt silicone oils can also prove to be problematic when used to siliconize syringe plungers, as the 1,000 cSt silicone oil can be pressed off the ribs of the syringe plunger more easily than high viscosity silicone oils. In contrast, the break-loose forces of such syringe plungers can be reduced by using high viscosity silicone oils, but this entails the problems discussed above for such high viscosity silicone oils.

[0008] U.S. Patent No. 7,332,227 discloses a lubricious coating composition for use with medical devices and the like. The lubricious composition includes a first siloxane polymer having a viscosity of less than 50 centistokes, a second siloxane polymer having a viscosity greater than 1 ,000 centistokes, and a reactive silicone polymer for crosslinking the first and second siloxane polymers. As a result, the lubricious composition formed and coated onto various medical devices is a crosslinked composition of both the first and second siloxane polymers. This coating composition and method of coating, however, do not involve an emulsion based process. That is, the coating composition is formed without an additional solvent, as the first siloxane polymer acts as the solvent for the coating composition. Moreover, the coating composition further requires additional components, such as a reactive silicone polymer. Thus, this method and coating composition not only fail to provide a substantially uniform coating consisting of high viscosity silicone oil using an emulsion based process, but further add to the complexity of the coating composition itself with additional reactive silicone polymers and the need to initiate crosslinking of the coating composition. [0009] U.S. Patent No. 5,911,711 discloses a two step coating process for coating hypodermic needles with a lubricant system. The lubricant system includes a first layer formed from at least partially cured organosiloxane copolymer and a polydimethylsiloxane that has a viscosity greater than 1 ,000 centistokes, and a second layer over the first layer that includes a polydimethylsiloxane having a viscosity of 50-350 centistokes. The coating compositions of the first and second layers are applied in a two step process with the use of a volatile carrier solvent. Thus, this lubricant system fails to provide a coated component with only a high viscosity silicone oil and further fails to address the problems associated with emulsion based systems having high viscosity silicone oils.

BRIEF SUMMARY OF THE INVENTION

[0010] The present invention provides a siliconization process capable of siliconizing components with high viscosity silicone oil using a silicone emulsion to advantageously provide a more uniform and homogenous coating of high viscosity silicone oil compared to traditional siliconization processes. Such coatings with high viscosity silicone oil can provide higher pull-off forces in the case of medical syringe tip caps or rubber stoppers and alleviate the problems of subvisible particles associated with coatings using silicone oils of about 1,000 cSt. The present invention also provides for more accurate control of the total silicone oil content on the siliconized components compared to conventional siliconization processes.

[0011] The present invention further provides a siliconization process that can uniformly siliconize a component with a high viscosity silicone oil, such as those having a kinematic viscosity from about 1,000 to 300,000 cSt. As used hereinafter, the term "viscosity" is meant to refer to kinematic viscosity. The high viscosity silicone oil is initially blended with a low viscosity liquid capable of forming a blended mixture (hereinafter a "silicone blend" or "silicone admixture"). The low viscosity liquid can be any liquid, such as a low viscosity silicone oil, capable of forming a blended mixture with the high viscosity silicone oil, such as a liquid having a kinematic viscosity from about 0.1 to 200 cSt. The low viscosity liquid is blended with the high viscosity silicone oil to form a silicone blend that effectively results in a homogenous silicone blend having a kinematic viscosity lower than that of the high viscosity silicone oil. Preferably, the silicone blend has a kinematic viscosity from about 10 cSt to 8,000 cSt, such that the silicone blend can be easily dispersed into an emulsion in a carrier liquid.

[0012] The silicone blend is preferably mixed with a carrier liquid to form a silicone emulsion. The components to be siliconized are then exposed to the silicone emulsion in a washing, tumbling, coating, or similar process, to sufficiently expose the components to the silicone emulsion.

Thereafter, the carrier liquid and low viscosity liquid are substantially removed from the surfaces of the components coated with the silicone emulsion, thereby leaving a uniform coating of essentially high viscosity silicone oil on the components.

[0013] In a preferred embodiment, the present invention also provides a method of uniformly coating high viscosity silicone oil onto components comprising: blending a high viscosity silicone oil and a low viscosity liquid to form a silicone blend; admixing the silicone blend with a carrier liquid to form a silicone emulsion; coating components with the silicone emulsion; and substantially removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil. [0014] In another preferred embodiment, the present invention provides a method of uniformly coating high viscosity silicone oil onto components comprising: providing a washing machine having a mixer; adding a blend of a high viscosity silicone oil and a low viscosity liquid, and a carrier liquid to the mixer to form a silicone emulsion; washing components in the washing machine with the silicone emulsion to uniformly coat the components with the silicone emulsion; removing the washed components from the washing machine; and substantially removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil.

[0015] In yet another preferred embodiment, the present invention provides a method of siliconizing components comprising: forming a silicone emulsion that includes a blend of a high viscosity silicone oil and a low viscosity liquid, and a carrier liquid; adding the silicone emulsion to a mixing tumbler; tumbling components in the mixing tumbler with the silicone emulsion to form components coated with the silicone emulsion; and substantially removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention provides a siliconization process for siliconizing surfaces with a high viscosity silicone oil. In accordance with a preferred embodiment of the present invention, the siliconization process will now be described with reference to siliconizing rubber stoppers. While the present embodiment refers, by way of example only, to siliconizing rubber stoppers, the process of the present embodiment is applicable to siliconizing any component or material with high viscosity silicone oil. Such materials include polymers (such as plastics and rubbers), glass, metals, alloys, and ceramics.

[0017] High viscosity silicone oils applicable to the present embodiment can be any silicone oil having a kinematic viscosity from about 1,000 cSt to 300,000 cSt. By way of example only and not by way of limitation, exemplary high viscosity silicone oils include 200^® Fluids, 10,000-300,000 cSt from Dow Corning of Midland, MI (i.e., a polydimethysiloxane) and polydialkylsiloxanes. Additional producers of high viscosity silicone oils include GE (Bayer) of Fairfield, CT and Wacker Chemie AG of Mϋnchen, Germany. [0018] The present embodiment provides a method of coating components with a high viscosity silicone oil. The high viscosity silicone oil is coated on the components using an emulsion. The emulsion is formed by initially blending the high viscosity silicone oil with a low viscosity liquid to form a silicone blend. The low viscosity liquid can be any volatile organic or inorganic-organic liquid having a low viscosity and capable of forming a blended mixture with the high viscosity silicone oil. The blend of high viscosity silicone oil and low viscosity liquid results in a silicone blend having an overall kinematic viscosity that is less than that of the high viscosity silicone oil alone.

[0019] Preferably, the low viscosity liquid has a kinematic viscosity in the range of about 0.1 to 200 cSt. The low viscosity liquid has a vapor pressure higher than the high viscosity silicone oil, such that the low viscosity liquid can be readily separated and removed from the high viscosity silicone oil by, for example, the application of heat or another drying process. By way of example only and not by way of limitation, exemplary low viscosity liquids include silicone oils, aliphatic hydrocarbons (such as alkanes, alkenes, and alkynes), aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, polymers, alcohols, ethers, esters, and ketones, and blends, derivatives, adducts, salts, and conjugates thereof having a viscosity in the range of about 0.1 to 200 cSt. Preferred low viscosity liquids include low viscosity silicones, such as 200^® Fluids, 0.5-20 cSt from Dow Corning, hexamethyldisiloxane, octamethyltrisiloxane, cyclohexane, naphtha, methyl ethylketone, dioxane, butanol, and amyl acetate.

[0020] The high viscosity silicone oil is blended with the low viscosity liquid at a weight ratio ranging from about 1 to 99 parts high viscosity silicone oil to about 1 to 99 parts low viscosity liquid. The low viscosity liquid is blended with the high viscosity silicone oil in an amount to effectively reduce the overall viscosity of the silicone blend such that the silicone blend can be more readily processed to form a silicone emulsion. Preferably, the viscosity of the silicone blend for forming the silicone emulsion is about 10 to about 8,000 cSt and more preferably about 200 cSt to about 2,000 cSt. Typically, high viscosity silicone oils are of such high viscosity that they cannot be easily dispersed in a mixture or coated onto surfaces. As a result, high viscosity silicone oils are difficult to process in conventional siliconization processes. The final ratio of high viscosity silicone oil to low viscosity liquid will depend upon the particular viscosities of the high viscosity silicone oil and low viscosity liquid starting materials and the targeted final resulting viscosity of the silicone blend. Generally, for a given high viscosity silicone oil, the lower the viscosity of the low viscosity liquid, the lower total amount of low viscosity liquid will be required.

[0021] For exemplary purposes only, the present embodiment will now be further described with reference to a blend of a high viscosity silicone oil having a viscosity of about 12,500 cSt and a low viscosity silicone oil having a viscosity of about 1 cSt as the low viscosity liquid. The high viscosity silicone oil can be blended with the low viscosity silicone oil at a ratio of about 4: 1 to 1 :4 and preferably about 1 :1. The resulting silicone blend can have a viscosity in the range of about 10 to about 8,000 cSt. The resulting viscosity for the silicone blend, in part, advantageously allows for the siliconization of components with a homogenous distribution of high viscosity silicone oil, as further described in detail below.

[0022] The silicone blend can then be mixed with a carrier liquid to form a silicone emulsion. The carrier liquid can be virtually any liquid sufficient to create an emulsion with the silicone blend. Preferably, the carrier liquid is water, however other carrier liquids capable of forming an emulsion with the silicone blend are within the intent and scope of the present embodiment. The silicone emulsion can be generated by a mixer that mixes, agitates, and/or homogenizes the silicone blend with the carrier liquid to create a substantially homogenous emulsion. The amount of silicone blend added to the carrier liquid can vary depending upon the specific silicone oil requirements for the component or product to be siliconized. That is, the concentration of silicone blend in the carrier liquid varies depending upon the total target amount of high viscosity silicone oil to be ultimately applied to the components and the ratio of high viscosity silicone oil to low viscosity silicone oil in the silicone blend.

[0023] Initially blending the high viscosity silicone oil and low viscosity liquid to form a silicone blend advantageously provides a homogenous mixture of the silicone blend. This degree of homogeneity for the silicone blend allows the silicone blend to form an appropriate emulsion suitable for siliconization processes. Without initially blending the high viscosity silicone oil with a low viscosity liquid, the appropriate emulsion would be difficult, if at all possible, to form.

[0024] After the silicone emulsion is created, the stoppers or other components to be siliconized are exposed to the silicone emulsion. The stoppers can be exposed to the silicone emulsion by a variety of methods, such as dip coating, spray coating, tumbling, washing, and the like. Such methods of exposing the components to the silicone emulsion are well known in the art and a detailed explanation of their structure, function, and operation is not necessary for a complete understanding of the present invention. Preferably, the stoppers are exposed to the silicone emulsion by a washing process. [0025] The washing process includes a washing machine having a mixer. The washing machine also includes a container for receiving and holding the silicone emulsion. However, alternatively to forming a silicone emulsion prior to and outside of the washing machine, the high viscosity and low viscosity silicone oil blend can be directly added to the carrier liquid in the washing machine for mixing and forming the silicone emulsion therein. In use, the mixer can be configured to continuously mix the silicone emulsion concurrently with the washing process to facilitate maintaining a well mixed silicone emulsion.

[0026] In washing the stoppers, the stoppers are placed in the washing machine's container and then agitated to thoroughly expose or wash the stoppers with the silicone emulsion. The stoppers can optionally be washed with the silicone emulsion at elevated temperatures within the washing machine, such as from about 15 to 100 degrees Celsius (C). Washing the stoppers with the silicone emulsion at elevated temperatures further reduces the viscosity of the silicone emulsion. Typically, for a given liquid, the viscosity lowers with increasing temperatures. Therefore, washing the stoppers at elevated temperatures with the silicone emulsion provides even better coating coverage due to the further reduction in viscosity of the silicone blend. The stoppers can also optionally be pre-washed prior to being exposed to or washed with the silicone emulsion to remove any debris or contaminants. [0027] After the stoppers are washed with the silicone emulsion, the carrier liquid (e.g., water) and low viscosity liquid are removed from the washed i.e., coated, stoppers. The carrier liquid and low viscosity liquid can be separated from the high viscosity silicone oil, and therefore removed from the coated stoppers, due to their higher volatile content or volatility compared to the high viscosity silicone oil. That is, low viscosity liquids, such as low viscosity silicone oils, typically have a relatively high vapor pressure and thus volatize at lower temperatures than high viscosity silicone oils. It is this difference in volatility of the low viscosity liquids versus high viscosity silicone oils that allows the siliconization process of the present embodiment to substantially remove the low viscosity liquids and carrier liquids from the stoppers, leaving the stoppers siliconized with a substantially uniform and homogenous distribution of high viscosity silicone oil coated on the surfaces of the stoppers.

[0028] An exemplary means of volatizing the carrier liquid and low viscosity liquid is to heat the coated stoppers in a heating process. Such heating processes are well known in the art, and a detailed description of their structure, function, and operation is not necessary for a complete understanding of the present invention. However, an exemplary heating process includes the use of heated air dryers.

[0029] Such heating processes maintain process parameters at specific predetermined conditions of time and temperature, which depend upon the specific silicone emulsion used to coat the components. That is, for a given silicone emulsion used to siliconize the stoppers, the predetermined conditions will be those sufficient to substantially remove the carrier liquid and low viscosity liquid from the silicone emulsion uniformly coated on the surfaces of the stoppers while maintaining the high viscosity silicone oil on the stoppers i.e., so as not to significantly volatize the high viscosity silicone oil. The predetermined conditions will also be sufficient so as not to detrimentally effect the components (stoppers) themselves. Thus, after the carrier liquid and low viscosity liquid are substantially or completely removed, the stoppers are left with a homogenous and uniform coating formed essentially of high viscosity silicone oil.

[0030] In an alternative embodiment, the stoppers or components can be siliconized in a mixing tumbler. In this embodiment, the silicone emulsion is prepared substantially the same as discussed above by initially blending a high viscosity silicone oil with a low viscosity liquid to form a silicone blend. The silicone blend is then mixed with a carrier liquid to form the silicone emulsion. This silicone emulsion is then added to the, mixing tumbler along with the stoppers for tumbling therein, thereby coating the stoppers with the silicone emulsion. The coated stoppers are then removed from the mixing tumbler. Thereafter, the carrier liquid and low viscosity liquid components of the silicone emulsion coated on the stoppers are removed.

[0031] The present invention advantageously solves the problems associated with conventional siliconization processes by providing methods to uniformly siliconize components with a coating of high viscosity silicone oil using an emulsion-based coating mixture. The methods of the present invention eliminate the need for using silicone oils of about 1,000 cSt, which typically result in subvisible particles that fail to meet certain quality requirements, may cause interactions with drug or fluid samples, and may add excessive lubricity to product components, such as syringe needle caps. In addition, due to the uniformity of the coating produced by the siliconization methods of the present invention, the total amount of high viscosity silicone oil applied to the components can be more accurately controlled.

[0032] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS We claim:

1. A method of uniformly coating high viscosity silicone oil onto components comprising the steps of: blending a high viscosity silicone oil and a low viscosity liquid to form a silicone blend; admixing the silicone blend with a carrier liquid to form a silicone emulsion; coating components with the silicone emulsion; and removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil.

2. The method of claim 1 , wherein the removing step comprises exposing the coated components to a heating process sufficient to volatize the carrier liquid and the low viscosity liquid leaving a substantially uniform layer of high viscosity silicone oil on the components.

3. The method of claim 1, wherein the low viscosity liquid is at least one of a silicone oil, an aliphatic hydrocarbon, an aromatic hydrocarbon, an alicyclic hydrocarbon, a halogenated hydrocarbon, a polymer, an alcohol, an ether, an ester, a ketone, and blends, derivatives, adducts, salts, and conjugates thereof.

4. The method of claim 3, wherein the low viscosity liquid has a kinematic viscosity from about 0.1 to 20O cSt.

5. The method of claim 1 , wherein the high viscosity silicone oil has a kinematic viscosity from about 1,000 cSt to about 300,000 cSt.

6. The method of claim 1 , wherein the low viscosity liquid has a kinematic viscosity from about 0.1 to 20O cSt.

7. The method of claim 1 , wherein the silicone blend has a kinematic viscosity from about 10 to 8,000 cSt.

8. The method of claim 1 , wherein the silicone blend has a kinematic viscosity from about 200 to 2,000 cSt.

9. The method of claim 1 , wherein the high viscosity silicone oil is blended with the low viscosity liquid at a ratio from about 1 to 99 parts high viscosity silicone oil to about 1 to 99 parts low viscosity liquid.

10. The method of claim 1 , wherein the carrier liquid is water.

11. The method of claim 1 , wherein the components are coated by at least one of a dip coating, a spray coating, a tumbling, and a washing process.

12. The method of claim 1 , wherein the coating step comprises the step of washing the components with the silicone emulsion in a washing machine.

13. A method of uniformly coating high viscosity silicone oil onto components comprising the steps of: providing a washing machine having a mixer; adding a silicone blend of a high viscosity silicone oil and a low viscosity liquid, and a carrier liquid to the mixer to form a silicone emulsion; washing components in the washing machine with the silicone emulsion to uniformly coat the components with the silicone emulsion; removing the washed components from the washing machine; and removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil.

14. The method of claim 13, wherein the carrier liquid is water.

15. The method of claim 13, wherein the removing step comprises volatizing the carrier liquid and the low viscosity liquid to form a substantially uniform layer of high viscosity silicone oil on the components.

16. The method of claim 13, wherein the washing step further includes mixing the silicone emulsion during the washing step.

17. The method of claim 13, wherein in the washing step the components are washed at temperatures from about 25 to 100 degrees C.

18. A method of siliconizing components comprising the steps of: forming a silicone emulsion that includes: a blend of a high viscosity silicone oil and a low viscosity liquid, and a carrier liquid; adding the silicone emulsion to a mixing tumbler; tumbling components in the mixing tumbler with the silicone emulsion to form components coated with the silicone emulsion; and removing the carrier liquid and the low viscosity liquid from the silicone emulsion coated on the components to form a coated component consisting essentially of high viscosity silicone oil.

19. The method of claim 18, wherein the carrier liquid is water.

20. The method of claim 18, wherein the removing step comprises exposing the coated components to heat sufficient to volatize the carrier liquid and the low viscosity liquid while substantially maintaining the high viscosity silicone oil on the coated components.