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Title:
COMPOSITION SUITABLE FOR USE AS AN ADHESIVE
Document Type and Number:
WIPO Patent Application WO/2014/058514
Kind Code:
A1
Abstract:
A composition comprises a first polysiloxane resin, a second polysiloxane resin, and a solvent. The first polysiloxane resin comprises at least one repeating unit in which a hydrogen is directly bonded to a silicon atom. The second polysiloxane resin comprises at least one repeating unit in which an alkyl group or alkenyl group (e.g., vinyl group) is directly bonded to a silicon atom.

Inventors:
HOY OLHA V (US)
Application Number:
PCT/US2013/052033
Publication Date:
April 17, 2014
Filing Date:
July 25, 2013
Export Citation:
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Assignee:
MILLIKEN & CO (US)
International Classes:
C09J183/04; A61K6/00
Foreign References:
US6433057B12002-08-13
US20090189180A12009-07-30
US6255407B12001-07-03
US4707531A1987-11-17
US2676182A1954-04-20
US4965295A1990-10-23
US6998427B22006-02-14
Other References:
GELEST INC: "REACTIVE SILICONES: FORGING NEW POLYMER LINKS", INTERNET CITATION, 2004, XP002470135, Retrieved from the Internet [retrieved on 20080220]
"Silicones", 15 April 2003, ENCYCLOPEDIA OF POLYMER SCIENCE AND TECHNOLOGY, WILEY, US, PAGE(S) 765 - 841, XP007918236
Attorney, Agent or Firm:
LANNING, Robert, M. (M-495Spartanburg, SC, US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1 . A composition comprising:

(a) a first polysiloxane resin, the first polysiloxane resin comprising at least one repeating unit conforming to the structure of Formula (I)

(I)

and at least one repeating unit conforming to the structure of Formula (II)

wherein Ri and R2 are independently selected from the group consisting of hydrogen, alkyl groups, and aryl groups;

(b) a second polysiloxane resin, the second polysiloxane resin comprising at least one repeating unit conforming to the structure of Formula (I) (I)

and at least one repeating unit conforming to the structure of Formula (I I I)

(I I I)

wherein R3 and R4 are independently selected from the group consisting of alkyl groups and aryl groups, and R5 is selected from the group consisting alkyl groups and alkenyl groups; and

(c) a solvent.

2. The composition of claim 1 , wherein R and R2 are independently selected from the group consisting C1 -C4 alkyl groups.

3. The composition of claim 1 or claim 2, wherein R and R2 are methyl groups.

4. The composition of any of claims 1 -3, wherein the first polysiloxane resin has a molecular weight of about 900 to about 1 , 1 00 g/mole.

5. The composition of any of claims 1 -4, wherein the first polysiloxane resin has a functional hydrogen content of about 9 mmole/g.

6. The composition of any of claims 1 -5, wherein R3 and R4 are

independently selected from the group consisting of C C4 alkyl groups.

7. The composition of any of claims 1 -6, wherein R3 and R4 are methyl groups.

8. The composition of any of claims 1 -7, wherein R5 is a CrC alkenyl group.

9. The composition of any of claims 1 -8, wherein R5 is a vinyl group.

10. The composition of any of claims 1 -9, wherein the second polysiloxane resin has a molecular weight of 4,000 to about 4,500 g/mole.

1 1 . The composition of any of claims 1 -10, wherein the second

polysiloxane resin has a functional alkenyl content of about 1 mmole/g.

12. The composition of any of claims 1 -1 1 , wherein the first polysiloxane resin comprises about 15 to about 30% by weight of the combined total weight of the first polysiloxane resin and the second polysiloxane resin present in the composition.

13. The composition of any of claims 1 -12, wherein the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 5 to about 75% of the total weight of the composition.

14. The composition of any of claims 1 -13, wherein the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 10 to about 60% of the total weight of the composition.

15. The composition of any of claims 1 -14, wherein the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 15 to about 50% of the total weight of the composition.

16. The composition of any of claims 1 -15, wherein the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 20 to about 45% of the total weight of the composition.

17. The composition of any of claims 1 -16, wherein the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 40% of the total weight of the composition.

18. The composition of any of claims 1 -17, wherein the solvent is selected from the group consisting of ethyl acetate, methyl acetate, acetone, and mixtures thereof.

19. The composition of any of claims 1 -18, wherein the solvent is ethyl acetate.

Description:
COMPOSITION SUITABLE FOR USE AS AN ADHESIVE

TECHNICAL FIELD

[0001] This disclosure relates to compositions suitable for use as adhesives in dental applications. In particular, this disclosure relates to compositions that are believed to be well suited for use in temporarily bonding silicone dental impression materials to dental equipment, such as metal and/or plastic trays used to hold the impression material.

BRIEF SUMMARY OF THE INVENTION

[0002] The invention generally provides a composition suitable for use as an adhesive, such as an adhesive for dental applications. The composition generally comprises a blend of two polysiloxane resins in a solvent. The first polysiloxane resin comprises at least one repeating unit in which a hydrogen is directly bonded to a silicon atom. The second polysiloxane resin comprises at least one repeating unit in which an alkyl group or alkenyl group (e.g., vinyl group) is directly bonded to a silicon atom.

[0003] In a first embodiment, the invention provides a composition comprising:

(a) a first polysiloxane resin, the first polysiloxane resin comprising at least one repeating unit conforming to the structure of Formula (I)

(I)

and at least one repeating unit conforming to the structure of Formula (II) wherein Ri and R 2 are independently selected from the group consisting of hydrogen, alkyl groups, and aryl groups;

(b) a second polysiloxane resin, the second polysiloxane resin comprising at least one repeating unit conforming to the structure of Formula (I)

(I)

and at least one repeating unit conforming to the structure of Formula (III)

(III)

wherein R 3 and R 4 are independently selected from the group consisting of alkyl groups and aryl groups, and R 5 is selected from the group consisting alkyl groups and alkenyl groups; and

(c) a solvent. DETAILED DESCRI PTION OF THE INVENTION

[0004] In a first series of embodiment, the invention generally provides a composition comprising a first polysiloxane resin, a second polysiloxane resin, and a solvent. In a possibly preferred embodiment, the invention provides a composition consisting essentially of the first polysiloxane resin, the second polysiloxane resin, and the solvent. In such an embodiment, the term "consisting essentially of" means that the composition does not contain appreciable amounts of additional polysiloxane resins (i.e., polysiloxane resins in addition to the first and second polysiloxane resins enumerated above and described below). For example, if any such additional polysiloxane resins are present in such a composition (i.e., a composition consisting essentially of the components enumerated above), the additional polysiloxane resin(s) are present in an amount of about 5% or less, about 4% or less, about 3% or less, about 2% or less, or about 1 % or less by weight of the composition.

[0005] The first and second polysiloxane resins can be generally described as "MQ resins." This terminology denotes the particular siloxane repeating units contained in the resin. The Q refers to a repeating unit having a structure

conforming to Formula (I)

(I)

In the structure of Formula (I) and the other structures set forth herein, the "Oi/ 2 " bonded to the silicon atom is intended to denote an oxygen atom that is "shared" by adjacent repeating units in the resin. Thus, the O-i /2 from adjacent repeating units "combine" to form a Si— O— Si linkage. The M refers to a repeating unit conforming to the structure of Formula (A) (A)

In the structure of Formula (A), R', R", and R"' each represent groups such as alkyl groups, aryl groups, or hydrogen. As can be seen from the structure, the M units contain only one bond to an adjacent siloxane repeating unit (i.e., they contain only one Ο 1 / 2 ). Therefore, an M unit terminates the propagation of the siloxane chain.

[0006] In a preferred embodiment, the first polysiloxane resin is an MQ resin comprising at least one repeating unit in which a hydrogen is directly bonded to a silicon atom. More specifically, in such an embodiment, the first polysiloxane resin comprises at least one repeating unit conforming to the structure of Formula (I)

(I)

and at least one repeating unit conforming to the structure of Formula (II)

R 2 In the structure of Formula (II), Ri and R 2 are independently selected from the group consisting of hydrogen, alkyl groups (e.g., C 1 -C 2 0 alkyl groups), and aryl groups (e.g., C 6 -C 2 o aryl groups). Preferably, Ri and R 2 are independently selected from the group consisting of C-i-C-io alkyl groups, more preferably C C 4 alkyl groups, with methyl groups being particularly preferred. The first polysiloxane resin can comprise additional repeating units in addition to those specifically noted above. For example, the first polysiloxane resin can also comprise one or more additional M units (i.e., one or more M units having a different structure than the structure of Formula (II)). Thus, the first polysiloxane resin can further comprise one or more repeating units conforming to the structure of Formula (A)

(A)

where R', R", and R'" are each independently selected from the group consisting of alkyl groups and aryl groups, such as the particular alkyl groups and aryl groups discussed above as suitable for the repeating unit conforming to the structure of Formula (II). The first polysiloxane resin can also comprise D units and/or T units. The D units have the structure

and the T units have the structure

In these D units and T units, R' and R" are each independently selected from the groups identified above in connection with the discussion of the structure of Formula (A). Preferably, the first polysiloxane resin consists essentially of repeating units conforming to the structure of Formula (I) and Formula (II). As used in this context, the term "consists essentially of" means that the resin does not contain appreciable amounts of repeating units conforming to a different structure. More preferably, the first polysiloxane resin consists of repeating units conforming to the structure of Formula (I) and Formula (II).

[0007] The first polysiloxane resin can have any suitable molecular weight. The molecular weight values reported herein are the weight average molecular weight (M w ) of the resin. The weight average molecular weight of the resin can be measured by known techniques using, for example, gel permeation chromatography (GPC) and standards of known molecular weight (e.g., polystyrene standards of known molecular weight). The molecular weights for all of the resins reported herein preferably are measured using such a GPC technique. Preferably, the first polysiloxane resin has a molecular weight of about 300 g/mole or more, about 400 g/mole or more, about 500 g/mole or more, about 600 g/mole or more, about 700 g/mole or more, about 800 g/mole or more, or about 900 g/mole or more. The first polysiloxane resin preferably has a molecular weight of about 2,000 g/mole or less, about 1 ,900 g/mole or less, about 1 ,800 g/mole or less, about 1 ,700 g/mole or less, about 1 ,600 g/mole or less, about 1 ,500 g/mole or less, about 1 ,400 g/mole or less, about 1 ,300 g/mole or less, about 1 ,200 g/mole or less, or about 1 ,100 g/mole or less. Thus, in a series of preferred embodiments, the first polysiloxane resin has a molecular weight of about 300 to about 1 ,500 g/mole, about 400 to about 1 ,400 g/mole, about 500 to about 1 ,300 g/mole, about 600 to about 1 ,200 g/mole, about 700 to about 1 ,100 g/mole, about 800 to about 1 ,100 g/mole, or about 900 to about 1 ,100 g/mole (e.g., about 1 ,000 g/mole).

[0008] The first polysiloxane resin can have any suitable functional hydrogen content. As utilized herein, the term "functional hydrogen content" refers to the amount of hydrogen atoms directly bonded to silicon atoms in the polysiloxane resin. Preferably, the first polysiloxane resin has a functional hydrogen content of about 0.1 mmole/g or more, about 0.5 mmole/g or more, about 1 mmole/g or more, about 2 mmole/g or more, about 3 mmole/g or more, about 4 mmole/g or more, about 5 mmole/g or more, about 6 mmole/g or more, about 7 mmole/g or more, or about 8 mmole/g or more. The first polysiloxane resin preferably has a functional hydrogen content of about 36 mmole/g or less, about 30 mmole/g or less, about 25 mmole/g or less, about 20 mmole/g or less, about 15 mmole/g or less, or about 10 mmole/g or less. Thus, in a series of preferred embodiments, the first polysiloxane resin has functional hydrogen content of about 0.1 to about 36 mmole/g, about 5 to about 25 mmole/g, about 6 to about 20 mmole/g, about 7 to about 15 mmole/g, or about 8 to about 10 mmole/g (e.g., about 9 mmole/g).

[0009] In a preferred embodiment, the second polysiloxane resin is an MQ resin comprising at least one repeating unit in which an alkyl group or alkenyl group is directly bonded to a silicon atom. More specifically, in such an embodiment, the second polysiloxane resin comprises at least one repeating unit conforming to the structure of Formula (I)

(I)

and at least one repeating unit conforming to the structure of Formula (III) (III)

In the structure of Formula (III), R 3 and R 4 are independently selected from the group consisting of alkyl groups (e.g., C- 1 -C 2 0 alkyl groups) and aryl groups (e.g., C 6 -C 2 o aryl groups). Preferably, Ri and R 2 are independently selected from the group consisting of C do alkyl groups, more preferably d-C 4 alkyl groups, with methyl groups being particularly preferred. R 5 is selected from the group consisting of alkyl groups (e.g., C 1 -C 2 0 alkyl groups) and alkenyl groups (e.g., C-i-C-io alkenyl groups). Preferably, R 5 is selected from the group consisting of alkenyl groups (e.g., C do alkenyl groups), more preferably d-C 4 alkenyl groups, with vinyl groups being particular preferred. The second polysiloxane resin can comprise additional repeating units in addition to those specifically noted above. For example, the second polysiloxane resin can also comprise one or more additional M units (i.e., one or more M units having a different structure than the structure of Formula (III)). Thus, the first polysiloxane resin can further comprise one or more repeating units conforming to the structure of Formula (A)

(A)

where R', R", and R'" are each independently selected from the group consisting of alkyl groups and aryl groups, such as the particular alkyl groups and aryl groups discussed above as suitable for the repeating unit conforming to the structure of Formula (III). The second polysiloxane resin can also comprise D units and/or T units, such as those described above in connection with the first polysiloxane resin. Preferably, the second polysiloxane resin consists essentially of repeating units conforming to the structure of Formula (I) and Formula (III). As used in this context, the term "consists essentially of" means that the resin does not contain appreciable amounts of repeating units conforming to a different structure. More preferably, the first polysiloxane resin consists of repeating units conforming to the structure of Formula (I) and Formula (III).

[0010] In another possible embodiment, the second polysiloxane resin can further comprise one or more M units having at least one hydrogen directly bonded to the silicon atom. Thus, in such an embodiment, the second polysiloxane resin can further comprise at least one repeating unit conforming to the structure of Formula (II) as such structure is described above in connection with the first polysiloxane resin. In such an embodiment, the repeating unit(s) of Formula (II) can be present in in the second polysiloxane resin in any suitable amount. Preferably, the repeating unit(s) of Formula (II) are present in the second polysiloxane resin in an amount sufficient to provide a functional hydrogen content falling within one of the ranges recited above for the first polysiloxane resin. When the second polysiloxane resin comprises at least one repeating unit conforming to Formula (II), the first

polysiloxane resin can optionally be omitted from the composition.

[0011] The second polysiloxane resin can have any suitable molecular weight. Preferably, the second polysiloxane resin has a molecular weight of about 2,000 g/mole or more, about 2,250 g/mole or more, about 2,500 g/mole or more, about 2,750 g/mole or more, about 3,000 g/mole or more, about 3,250 g/mole or more, about 3,500 g/mole or more, about 3,750 g/mole or more, or about 4,000 g/mole or more. The second polysiloxane resin preferably has a molecular weight of about 20,000 g/mole or less, about 17,500 g/mole or less, about 15,000 g/mole or less, about 12,500 g/mole or less, about 10,000 g/mole or less, about 9,000 g/mole or less, about 8,000 g/mole or less, about 7,000 g/mole or less, about 6,000 g/mole or less, or about 5,000 g/mole or less (e.g., about 4,500 g/mole or less). Thus, in a series of preferred embodiments, the second polysiloxane resin has a molecular weight of about 2,000 to about 20,000 g/mole, about 2,250 to about 17,500 g/mole, about 2,500 to about 15,000 g/mole, about 2,750 to about 12,500 g/mole, about 3,000 to about 10,000 g/mole, about 3,250 to about 9,000 g/mole, about 3,500 to about 8,000 g/mole, about 3,500 to about 7,000 g/mole, about 3,500 to about 6,000 g/mole, about 3,500 to about 5,000 g/mole, about 3,500 to about 4,500 g/mole, or about 4,000 to about 4,500 g/mole (e.g., about 4,300 g/mole).

[0012] When R 5 is an alkenyl group, the second polysiloxane resin can have any suitable functional alkenyl content. As utilized herein, the term "functional alkenyl content" refers to the amount of alkenyl groups directly bonded to silicon atoms in the polysiloxane resin. Preferably, the second polysiloxane resin has a functional alkenyl content of about 0.05 mmole/g or more, about 0.1 mmole/g or more, about 0.15 mmole/g or more, about 0.2 mmole/g or more, about 0.3 mmole/g or more, about 0.4 mmole/g or more, about 0.5 mmole/g or more, about 0.6 mmole/g or more, about 0.7 mmole/g or more, about 0.8 mmole/g or more, or about 0.9 mmole/g or more. The second polysiloxane resin preferably has a functional alkenyl content of about 15 mmole/g or less, about 14 mmole/g or less, about 13 mmole/g or less, about 12 mmole/g or less, about 1 1 mmole/g or less, about 10 mmole/g or less, about 9 mmole/g or less, about 8 mmole/g or less, about 7 mmole/g or less, about 6 mmole/g or less, or about 5 mmole/g or less (e.g., about 2 mmole/g or less). Thus, in a series of preferred embodiments, the second polysiloxane resin has a functional alkenyl content of about 0.05 to about 15 mmole/g, about 0.1 to about 14 mmole/g, about 0.15 to about 13 mmole/g, about 0.2 to about 12 mmole/g (e.g., about 0.2 to about 6 mmole/g), about 0.3 to about 1 1 mmole/g, about 0.4 to about 10 mmole/g, about 0.5 to about 9 mmole/g (e.g., about 0.5 to about 2 mmole/g), about 0.6 to about 8 mmole/g, about 0.7 to about 7 mmole/g, about 0.8 to about 6 mmole/g, about 0.9 to about 5 mmole/g (e.g., about 0.9 to about 2 mmole/g or about 1 mmole/g).

[0013] The first polysiloxane resin and the second polysiloxane resin can be present in the composition in any suitable relative amounts. Preferably, the first polysiloxane resin comprises about 50% or less by weight of the combined total weight of the first polysiloxane resin and the second polysiloxane resin present in the composition. More preferably, the first polysiloxane resin comprises about 45% or less, about 40% or less, about 35% or less, about 30% or less, or about 25% or less by weight of the combined total weight of the first polysiloxane resin and the second polysiloxane resin present in the composition. The first polysiloxane resin preferably comprises about 1 % or more, about 5% or more, about 10% or more, about 15% or more, or about 20% or more by weight of the combined total weight of the first polysiloxane resin and the second polysiloxane resin present in the composition. Thus, in a series of preferred embodiments, the first polysiloxane resin comprises about 1 to about 50%, about 5 to about 45%, about 10 to about 40%, about 15 to about 35%, or about 15 to about 30% (e.g., about 15 to about 25%, about 20 to about 25%, or about 25%) by weight of the combined total weight of the first polysiloxane resin and the second polysiloxane resin present in the composition.

[0014] The first polysiloxane resin and the second polysiloxane resin can account for any suitable amount of the composition's total weight. Preferably, the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 5% or more, about 10% or more, about 20% or more, about 30% or more, or about 35% or more of the total weight of the composition. The total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition preferably is about 75% or less, about 60% or less, about 50% or less, or about 45% or less of the total weight of the composition. Thus, in a preferred series of embodiments, the total amount of the first polysiloxane resin and the second polysiloxane resin present in the composition is about 5 to about 75%, about 10 to about 60%, about 15 to about 50%, about 20 to about 45%, about 30 to about 45%, about 35 to about 45% (e.g., about 40%) of the total weight of the composition.

[0015] The first and second polysiloxane resins can be produced by processes known to those familiar with the art. For example, a process that is believed to be suitable for producing the resins is disclosed in U.S. Patent No.

4,707,531 (Shirahata). U.S. Patent No. 2,676,182 (Daudt et al.) also discloses a process that is believed to be suitable for producing the resins.

[0016] The composition further comprises a solvent. The solvent can be any suitable solvent. The principal function of the solvent is provide a medium that allows the mixture of the first and second polysiloxane resins to be workable so that the mixture can be applied to the target substrate(s). Preferably, the solvent does not react with the first and second polysiloxane resins, has a relatively high vapor pressure at room temperature, and exhibits low toxicity or is non-toxic. Also, the solvent preferably is compatible with dental appliances and applications. Preferably, the solvent is selected from the group consisting of ethyl acetate, methyl acetate, acetone, and mixtures thereof.

[0017] The solvent can be present in the composition in any suitable amount. Generally, the amount of solvent in the composition is sufficient to render the composition workable and to aid application of the composition to the target substrate(s).

[0018] The composition of the invention is believed to be well-suited for use as an adhesive. In particular, Applicant believes that the composition is suitable for use as an adhesive for temporarily securing silicone dental impression materials to the trays used by dental professional in taking impressions using those materials. It is believed that the composition of the invention will provide a good balance of adhesion and release characteristics. In other words, it is believed that the composition will provide good adhesion between the impression material and the tray (e.g., metal or plastic tray), while also permitting the impression material to be removed from the tray after the impression is made. This is important because the silicone impression material can be damaged during the removal process if the adhesion between the tray and the impression material is too strong. On the other hand, if the adhesion is not strong enough, the impression material can separate from the tray while an impression is being made, making it difficult to obtain a useful impression.

[0019] In another embodiment, the invention provides a method for using the composition described above. More specifically, the invention provides a method for using the composition as an adhesive for dental impression materials. The method generally comprises the steps of: (a) providing a composition as described above; (b) providing a tray suitable for taking a dental impression or mold; (c) applying the composition to at least a portion of a surface of the tray; (d) allowing substantially all of the solvent in the composition applied to the substrate to evaporate; and (e) applying a dental impression material to the prepared tray (i.e., the tray to which the composition has been applied and allowed to dry). The method can further comprise the steps of: (f) taking an impression of a patient's mouth and/or teeth using the tray to which the dental impression material has been applied; and/or (g) removing the dental impression material from the tray. The tray and dental impression material used in the above-described method can be any suitable tray and dental impression material. Preferably, the dental impression material is a two-part room temperature vulcanizing (RTV) silicone impression material. It is believed that the materials disclosed in U.S. Patent No. 4,965,295 (Schwabe et al.) and U.S. Patent No.

6,998,427 (Del Torto et al.) are suitable for use as the impression materials in the above-described method, and these patents are hereby incorporated by reference for their disclosures of such impression materials.

[0020] While not wishing to be bound to any particular theory, it is believed that the composition provides particularly good adhesion due to a combination of its physical and chemical properties. From the physical property standpoint, the mixture of the polysiloxane resins in the composition forms, in the absence of the solvent, a nearly solid mass that is also very tacky. This physical property is believed to be at least partially responsible for the good adhesion to the tray. From the chemical property standpoint, it is believed that the functional hydrogen in the first

polysiloxane resin and/or the functional alkenyl groups in the second polysiloxane resin can react with components present in the silicone impression material. This reaction will result in the formation of chemical "hooks" between the silicone impression material and the mass of adhesive, promoting a strong bond between the tray and impression material.

[0021] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0022] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the subject matter of this application (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open- ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the subject matter of the application and does not pose a limitation on the scope of the subject matter unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the subject matter described herein.

[0023] Preferred embodiments of the subject matter of this application are described herein, including the best mode known to the inventors for carrying out the claimed subject matter. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the subject matter described herein to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above- described elements in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.