AMINE CATALYST BLEND USEFUL IN THE PRODUCTION OF POLYURETHANE ARTICLES

Roger Hennington

Robert Allison Grigsby, Jr.

Ernest L. Rister, Jr.

GeneWiltz, Jr. Jennifer Koch Pratt

FIELD OF THE DISCLOSURE [0001] This disclosure, in general, relates to amine catalyst blends and in particular, to amine catalyst blends useful in the production of polyurethane articles.

BACKGROUND

[0002] Polyurethanes comprise a versatile family of polymers that can be used in a variety of applications. For example, polyurethane can be used to form films, foams, paints, and polymer fibers, or can be used as adhesives. In particular, polyurethane elastomeric foams can be used to form a variety of products including seat cushions and the soles of shoes.

[0003] To form polyurethane, a polyol is mixed with an isocyanate in the presence of catalyst. To form foams and in particular, to form elastomeric foams, a polyol and isocyanate may be mixed in the presence of a catalyst and a blowing agent.

[0004] When used in a manufacturing setting, the cost of the article is often influenced by the curing characteristics of the polyurethane used in the process. If the reaction is initiated too quickly, it may be difficult to fill a mold with a mix of the prepolymer components. On the other hand, if the reaction proceeds in a slow manner, product through put is slowed, resulting in increased cost.

[0005] As such, an improved polyurethane system would be desirable.

SUMMARY

[0006] In a particular embodiment, a catalyst blend includes a triethylenediamine and a triazine.

[0007] In another exemplary embodiment, a catalyst blend includes a triethylenediamine component, a hexahydrotriazine component, and a solvent. The ratio of the amount of the triethylenediamine component to the amount of the hexahydrotriazine component is in a range between about 10:1 and about 1 :10.

[0008] In a further exemplary embodiment, a method of forming a polyurethane includes blending a first polyol component, an isocyanate component, a triethylenediamine component, and a triazine component to form a blend, and curing the blend to form the polyurethane.

DESCRIPTION OF THE EMBODIMENTS

[0009] In a particular embodiment, polyurethane is formed from a blend of prepolymer components including a polyol component, an isocyanate component, and a catalyst blend component. In addition, the prepolymer components may include one or more additional polyols. The prepolymer components also may include a blowing agent, such as water. In a particular example, the catalyst blend includes a triethylenediamine component and a triazine component. The catalyst blend also may include metal catalysts or additional amine catalysts. In a particular example, the triethylenediamine (TEDA) component and the triazine component are included in amounts in a ratio of about 1 : 10 to about 20: 1 TEDA:triazine. In a particular embodiment, the polyurethane is an elastomeric foam polyurethane.

[0010] In another exemplary embodiment, a method of forming a polyurethane includes blending a polyol component, a triethylenediamine (TEDA) component, a triazine component, and an isocyanate component to form a blend. The method further includes curing the blend to form a polyurethane. The method also may include blending a blowing agent to form the blend.

[0011] In general, the polyurethane is formed from a prepolymer mixture including an isocyanate component, a polyol component, and a catalyst blend. In addition, the prepolymer mixture may include a blowing agent, additives, auxiliary agents, or any combination thereof. In an exemplary embodiment, the isocyanate component may include a di-isocyanate monomer. An exemplary di-isocyanate monomer may include tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, polymethylenepolyphenyl diisocyanate, 3,3'-dimethyl-4,4'- biphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3'- dichloro-4,4'-biphenylene diisocyanate or 1,5 -naphthalene diisocyanate; their modified products, for instance, carbodiimide-modifϊed products; or the like, or any combination thereof. Such di-isocyanate monomers may be used alone or in admixture of at least two kinds. Among them, 4,4'-diphenylmethane diisocyanate, and a combined use of 4,4'-diphenylmethane diisocyanate and its carbodiimide- modified product may be used to provide sufficient strength and wear resistance as a shoe sole. In a particular example, the isocyanate component may be Suprasec® 2981, an aliphatic ester based quasi prepolymer formed from the reaction of an aliphatic polyester polyol and MDI, available from Huntsman.

[0012] The amount of isocyanate reactive compound used in the prepolymer components provides an Isocyanate Index of between about 80 and about 120, such as between about 95 and about 105. The Isocyanate Index equals the actual amount of isocyanate used divided by the amount of isocyanate required to react all reactive species in the polyol component multiplied by 100.

[0013] In an exemplary embodiment, the polyol may include a polyether polyol, a polyester polyol, a polymeric polyol, a low molecular weight polyol, or any combination thereof. Suitable polyether polyols useful for production of the elastomers can be produced polyinsertion via DMC catalysis of alkylene oxides, by anionic polymerization of alkylene oxides in the presence of alkali hydroxides or alkali alcoholates as catalysts and with the addition of at least one initiator molecule containing 2 to 6, preferably 2 to 4, reactive hydrogen atoms in bonded form, or by

cationic polymerization of alkylene oxides in the presence of Lewis acids, such as antimony pentachloride or boron fluoride etherate. Suitable alkylene oxides contain 2 to 4 carbon atoms in the alkylene radical. An example includes tetrahydrofuran, 1,2- propylene oxide, 1,2- or 2,3-butylene oxide; ethylene oxide, 1 ,2-propylene oxide, or any combination thereof. The alkylene oxides can be used individually, in succession, or as a mixture. In particular, mixtures of 1,2-propylene oxide and ethylene oxide may be used, whereby the ethylene oxide is used in quantities of 10 to 50% as an ethylene oxide terminal block so that the resulting polyols display over 70% primary OH terminal groups. An example of an initiator molecule includes water or dihydric or trihydric alcohols, such as ethylene glycol, 1,2-propanediol and 1,3-propanediol, diethylene glycol, dipropylene glycol, ethane- 1,4-diol, glycerol, trimethylol propane, or any combination theroef.

[0014] Suitable polyether polyols, such as polyoxypropylene polyoxyethylene polyols, have average functionalities of 1.6 to 2.4, such as 1.8 to 2.4, and number- average molecular weights of 800 g/mol to 25,000 g/mol, such as 800 g/mol to 14,000 g/mol, particularly 2,000 g/mol to 9,000 g/mol. Difunctional or trifunctional polyether polyols having a number-average molecular weight of 800 g/mol to 25,000 g/mol, such as 800 g/mol to 14,000 g/mol, or even 2,000 g/mol to 9,000 g/mol, may be used as polyol components.

[0015] Also, suitable polyol components include polymer polyols, polyether polyols, polymer-modified polyether polyols, such as graft polyether polyols, or any combination thereof. For example, polyols based on styrene or acrylonitrile may be used.

[0016] In an exemplary embodiment, a polyester polyol is derived from dibasic acids such as adipic, glutaric, fumaric, succinic, or maleic acid, or anhydrides and difunctional alcohols, such as ethylene glycol, diethylene glycol, propylene glycol, di or tripropylene glycol, 1-4 butane diol, 1-6 hεxanε diol, or any combination. For example, the polyester polyol may be formed by the condensation reaction of the glycol and the acid with the continuous removal of the water by-product. A small amount of high functional alcohol, such as glycerin, trimethanol propane,

pentaerythritol, sucrose or sorbitol or polysaccarides may be used to increase branching of the polyester polyol. The esters of simple alcohol and the acid may be used via an ester interchange reaction where the simple alcohols are removed continuously like the water and replaced by one or more of the glycols above. Additionally, polyester polyols may be produced from aromatic acids, such as terphthalic acid, phthalic acid, 1,3, 5 benzoic acid or their anhydrides, such as phthalic anhydride. An exemplary polyester polyols may include Fomrez available from Witco Corporation. For example, Fomrez-53 is a 56-hydroxyl number diethylene glycol adipate manufactured by Witco Corporation. A similar product is manufactured by Inolex under the brand name Lexorez 1102-56 A.

[0017] In a particular embodiment, the polyurethane may be prepared using both a high molecular weight polyol and one or more low molecular weight polyols. For example, the high molecular weight polyol may have a hydroxyl number not greater than about 60, such as a hydroxyl number of not greater than about 56. In another example, the one or more low molecular weight polyols may have a hydroxyl number of at least about 800, such as at least about 900. In a particular embodiment, the prepolymer components may include an aliphatic polyester polyol and a low molecular weight polyol, such as 1 , 4 butane diol or ethylene glycol. For example, a high molecular weight polyol and a low molecular weight polyol may be used in a ratio of about 5:1 to about 10:1 High:Low, such as about 6.5:1 to about 9:1.

[0018] The catalyst blend used in the prepolymer mixture may include triethylenediamine (TEDA) and a triazine catalyst. The triazine may, for example, include a hexahydrotriazine, such as a hexahydrotriazine with functional groups. In a particular example, the hexahydrotriazine functional groups may include amine functional groups, such as secondary or tertiary amine functional groups. In a particular example, the amine functional groups are dialkyl amino alkyl groups. For example, the hexahydrotriazine may include N, N', N" - tris (N, N - dialkylamino alkyl) hexahydrotriazine, such as N, N', N" - tris (N, N - dimethylamino propyl) hexahydrotriazine or N,N'N"-tris (N ₅ N dimethylaminoethoxypropyl) hexahydrotriazine.

[0019] The TEDA and the triazine may be used in amounts in a ratio of about 1 : 90 to about 90:1 TEDA:triazine. For example, the ratio may be in a range of about 1:10 to about 20:1, such as a range of about 1 :1 to about 10:1, or a range of about 2:1 to about 6:1.

[0020] In a particular embodiment, the TEDA and the triazine may be included in a catalyst blend that also includes a solvent. For example, a solvent may include a chain extender. In an example, the solvent may include a polyol, such as 1, 4 - butanediol or ethylene glycol. In a particular example, the solvent is included in an amount of about 25 wt% to about 95 wt% of the catalyst blend, such as about 50 wt% to about 75 wt%.

[0021] The catalyst blend also may include additional catalysts, such as a metal catalyst, another amine catalyst, or a combination thereof. A metal catalyst may for example include a lithium carboxylate, an organic titanium, an organic zirconium, a bismuth carboxylate, or any combination thereof.

[0022] The additional amine catalyst may include a tertiary amine, such as tributylamine, N-methyl morpholine, N-ethyl morpholine, N ₅ N ₅ N' ,N'-tetramethyl ethylene diamine, pentamethyl diethylene triamine and higher homologues, 1 ,4- diazabicyclo-[2,2 ,2] -octane, N-methyl-N'-dimethylaminoethyl piperazine, bis(dimethylaminoalkyl) piperazine, N,N-dimethyl benzylamine, N,N-dimethyl cyclohexylamine, N,N-diethyl benzylamine, bis(N,N-diethylaminoethyl) adipate, N,N,N',N'-tetramethyl-l,3-butane diamine, N,N-dimethyl-β-phenyl ethylamine, bis(dimethylaminopropyl) urea, bis(dimethylaminopropyl) amine, 1,2-dimethyl imidazole, 2-methyl imidazole, monocyclic and bicyclic amidine, bis(dialkylamino) alkyl ether, such as e.g., bis(dimethylaminoethyl) ethers, tertiary amines having amide groups (such as formamide groups), or any combination thereof. Another example of a catalyst component includes Mannich bases including secondary amines, such as dimethylaminε, or aldehyde, such as formaldehyde, or ketone such as acetone, methyl ethyl ketone or cyclohexanone or phenol, such as phenol, nonyl phenol or bisphenol. A catalyst in the form of a tertiary amine having hydrogen atoms that are active with respect to isocyanate groups may include triethanolamine, triisopropanolamine, N-

methyldiethanolamine, N-ethyl diethanolamine, N,N-dimethyl ethanolamine, reaction products thereof with alkylene oxides such as propylene oxide or ethylene oxide, or secondary-tertiary amines, or any combination thereof. Silamines with carbon-silicon bonds can also be used as catalysts, for example, 2,2,4-trimethyl-2-silamorpholine, 1,3 -diethyl aminomethyl tetramethyl disiloxane, or any combination thereof.

[0023] In a particular example, the additional amine catalyst is selected from a pentamethyl diethylene triamine, dimethylaminopropylamine, N ₅ N' dimethylpiperazine and dimorpholinoethylether, N ₅ N' dimethyl aminoethyl N-methyl piperazine, JEFFCAT®DM-70 (a mixture of N ₅ N' dimethylpiperazine and dimorpholinoethylether), imadozoles, triazines, or any combination thereof. In a particular example, a ratio of the amount of TEDA to the amount of the additional amine catalyst is in a range of about 10:1 to about 1 :10 TEDA: additional amine catalyst, such as a range of about 6: 1 to about 2:1.

[0024] The catalyst blend may be useful in a range of about 0.03 wt% to about 10.0 wt% of the prepolymer mixture. For example, the catalyst blend may be used in an amount of about 0.1 wt% to about 4.0 wt% of the prepolymer mixture.

[0025] In a further embodiment, the prepolymer mixture also may include low molecular weight chain extenders, blowing agents, stabilizers, and other additives and auxiliary agents. For example, the prepolymer mixture may also include a low molecular weight chain extender having an average functionality of 1.8 to 2.1. In an example, the low molecular weight chain extender may have an average functionality of about 2. A suitable chain extender may include alkane diol, dialkylene glycol, polyalkylene polyols, or any combination thereof. In addition, the prepolymer mixture may include trifunctional or tetrafunctional crosslinking agents or mixtures of chain extenders and crosslinking agents. An exemplary crosslinking agent may including trihydric or tetrahydric alcohols or oligomeric polyalkylene polyols having an average functionality of 3 to 4 and a molecular weight of up to about 750 g/mol. In particular, the crosslinking agent may have a molecular weight of about 18 g/mol to about 400 g/mol, such as about 60 g/mol to about 300 g/mol. Alkane diols having 2 to 12, preferably 2, 4 or 6 carbon atoms, such as ethanediol, 1,6-hexanediol, 1,7-

heptanediol, 1,8-octanediol, 1 ,9-nonanediol, 1,10-decanediol, or in particular, 1,4- butanediol, or dialkylene glycols having 4 to 8 carbon atoms, such as diethylene glycol and dipropylene glycol, as well as polyoxyalkylene glycols, or any combination thereof, may be used as chain extenders. Also suitable are branched- chain or unsaturated alkane diols with no more than 12 carbon atoms, such as 1 ,2- propanediol, 2-methyl-l,3-propanediol, 2,2-dimethyl- 1,3 -propanediol, 2-butyl-2- ethyl- 1,3 -propanediol, 2-butene-l,4-diol or 2-butyne-l,4-diol, diesters of terephthalic acid with glycols having 2 to 4 carbon atoms, such as terephthalic acid-bis-ethylene glycol or terephthalic acid-bis-l,4-butanediol, hydroxyalkylene ethers of hydroquinone or resorcinol, e.g., l,4-di(β-hydroxyethyl) hydroquinone or l,3-(β- hydroxyethyl) resorcinol, alkanolamines with 2 to 12 carbon atoms such as ethanolamine, 2-aminopropanol and 3-amino-2,2-dimethyl propanol, N-alkyl dialkanolamines, such as N-methyl and N-ethyl diethanolamine, (cyclo)aliphatic diamines with 2 to 15 carbon atoms, such as 1,2-ethylene diamine, 1,3 -propylene diamine, 1,4-butylene diamine and 1,6-hexa-methylene diamine, isophorone diamine, 1 ,4-cyclohexamethylene diamine and 4,4'-diaminodicyclohexyl methane, N-alkyl- substituted, N,N'-dialkyl-substituted and aromatic diamines, which can also be substituted at the aromatic radical by alkyl groups, having 1 to 20, preferably 1 to 4 carbon atoms in the N-alkyl radical, such as N,N'-diethyl, N,N'-di-sec.-pentyl, N ₅ N'- di-sec.-hexyl, N,N'-di-sec.-decyl and N,N'-dicyclohexyl (p- or m-) phenylene diamine, N,N'-dimethyl, N,N'-diethyl, N,N'-diisopropyl, N,N'-di-sec.-butyl, N ₅ N'- dicyclohexyl, -4,4'-diaminodiphenylmethane, N,N'-di-sec. -butyl benzidine, methylene bis(4-amino-3 -methyl benzoate), 2,4-chloro-4,4'-diaminodiphenylmethane, 2,4- and 2,6-toluene diamine, or any combination thereof.

[0026] In a particular example, the prepolymer mixture includes a blowing agent. For example, a blowing agent may include water, or a physical blowing agent, such as a low boiling alkane, partially or completely fluorinated hydrocarbons, or any combination thereof. A suitable low boiling alkane includes acetone, pentane, hexane, cyclopentane, or any combination thereof. An example of a suitable partially or completely fluorinated hydrocarbon includes HFC-134a (1,1,1,2-tetrafluoroethane), HFC-245fa (1,1,1,3,3-pentafluoropropane), HFC-245ca (1,1,2,2,3-

pentafluoropropane), HFC-236ca (1,1,1,2,3,3-hexafluoropropane), or any combination thereof. Methylene chloride is also a suitable blowing agent. In particular, mixtures of these various blowing agents are also suitable. In a particular embodiment, the blowing agent includes water. For example, water may be used in a range of about 0.1 to about 2.0 parts per hundred parts of isocyanate reactive component.

[0027] In an exemplary embodiment, the prepolymer mixture may include film stabilizers, such as silicone oils or emulsifiers. For example, the film stabilizer may be an organic silane or siloxane. In particular, the silicone foam stabilizer may have the formula:

RSi[O-(R ₂ SiO) _H -(oxyalkylene) _m R] ₃

[0028] wherein R is an alkyl group containing about 1 to about 4 carbon atoms; n is an integer of about 4 to about 8; m is an integer of about 20 to about 40; and the oxyalkylene groups are derived from propylene oxide or ethylene oxide.

[0029] In addition, other additives and auxiliary agents may be used. For example, an additive or an auxiliary agent may be selected from a cell regulator, a crosslinker, a flame retardant, a plasticizer, a filler, a pigment, or any combination thereof.

[0030] In a particular embodiment, a polyurethane is formed by blending the components of the prepolymer mixture. For example, the polyurethane may be formed by blending a polyol component, an isocyanate component, TEDA component, and a triazine component to form a blend. The method includes curing the blend to form the polyurethane. The method may further include blending a second polyol to form the blend. For example, the first polyol may have a hydroxyl number not greater than about 60, such as not greater than about 56, and the second polyol may have a hydroxyl number of at least about 800, such as at least about 900.

[0031] In a particular example, blending includes blending the catalyst components in specific ratio. For example, the ratio of the amount of TEDA component to the amount of triazine component may be in a range of about 1 :10 to about 20:1

TEDA:triazine. For example, the ratio may be about 1 :1 to about 10:1, such as about 6:1 to about 2:1.

[0032] In a particular example, the TEDA component and the triazine component may be mixed with the polyol component to form a preblend prior to mixing the isocyanate component to form the blend. Further, the TEDA component and the triazine component may be blended with a solvent to form a catalyst blend. The catalyst blend may be used to blend with the polyol prior to blending with the isocyanate component, or in conjunction with blending with the isocyanate component.

[0033] The method further may include filling a mold with the blend and allowing the polyurethane prepolymer mixture to at least partially cure to form the polyurethane. In a particular example, the at least partially cured polyurethane may be removed from the mold prior to complete curing and allowed to cure to completion outside of the mold.

[0034] While the catalyst blend has been described in the context of a prepolymer mixture configured to form a polyurethane, the catalyst blend also may be useful in reactions between isocyanate functionality and an active hydrogen containing compound. For example, the active hydrogen containing compound may include an alcohol, a polyol, an amine, water, or any combination thereof.

[0035] Particular embodiments disclosed above advantageously provide technical features desirable in polyurethane systems. In particular, embodiments influence the cure parameters of polyurethane systems, such as cream time, gel time, rise time, tack free time, rebound pinch time, and rise height. Cream time correlates with the initiation of the reaction within the prepolymer components. Cream time is determined when the mixture of prepolymer components becomes milky or forms air bubbles. Generally, it is desirable to have a moderate cream time, not too fast and not too slow, such as about 8 sec. to 10 sec. The gel time is when the liquid has polymerised enough that on touching the liquid and pulling away a thin polymer strand (or string) is seen. At this point the liquid is turning into a polymer gel. The

rise time is when the foamed polyurethane has reached the largest volume. When the foaming reaction is performed in a cup, the rise time is the time for the foam to reach maximum height and stop rising. The tack-free time is when the polyurethane foam has cured enough that it is no longer 'sticky' or 'tacky' to the touch. The rebound pinch time is the time for the foam to cure enough that upon pinching, the foam rebounds to it original shape or shows little evidence of deformation caused by the pinching. Rise height is the maximum height the foam rises when reacted in a controlled measuring cup. The tack-free time and rebound pinch time are indicative of the back end of the reaction and the cream time and gel time are indicative of the front end of the reaction.

[0036] In particular, embodiments disclosed above exhibit improved back-end reaction characterstics, such as lower tack-free time and lower rebound pinch times, while exhibiting similar front end reaction characteristics, such as cream time and gel time, to other systems.

[0037] EXAMPLES

[0038] Laboratory-scale trials are conducted using free-rise experiments to attain reactivity profiles. Handmix techniques are used to prepare foams in square molds for physical property testing. The handmix technique is performed using a mechanically driven mixer equipped with high shear mixing blades.

[0039] For each of the experiments, foam production involves the preparation of a pre-blend, which consists of the polyols and other ingredients, except for the isocyanate prepolymer and the catalysts. The pre-blend is allowed to degas prior to foam production and is weighed into an appropriately sized mixing cup. The individual amine catalysts are added in appropriate quantities into the measured amount of preblend and are mixed for 10 seconds in a paper cup, followed by the immediate addition of isocyanate with continued mixing for 5 seconds. The reacting foam is immediately poured into the container. For polyether systems, the pre-blend and isocyanate prepolymer are used at 70-75 ⁰ F, while for polyester systems, the pre- blend and isocyanate are used at 105-115°F.

[0040] Reactivity profiles are recorded during the reaction; the cream, top of cup, end of rise, tack-free, and rebound pinch times are recorded. The rebound pinch time correlates with the demold time.

[0041] The mold for these experiments is 1 inch x 4 inch x 14 inch. The mold temperature is 45 ⁰ C and the demold time is 2 to 6 minutes.

[0042] The quantities listed in all examples are parts by weight. The aliphatic polyester polyol is made from adipic acid, diethylene glycol, and 1,4 butanediol. It is sold under the name of Daltorez P 716. Table 1 gives the preblended B-component use for the examples. DABCO DC- 193 is a silicone surfactant manufactured by Dow Corning Corporation.

Table 1

[0043] Examples A - C

[0044] For this set of examples, a pre-blend of B-component is prepared as in Table 1. The isocyanate is added via syringe for more accurate control. Example A is a comparative example. The results are shown in Table 2.

[0045] As shown by Examples B-C, the use of JEFFCAT® TR-90 (N, N', N" - tris (N, N - dimethylamino propyl) hexahydrotriazine) in combination with TEDA significantly improves the back-end of the reaction (tack free time and rebound pinch) without affecting the cream time (front-end reactivity).

Table 2

[0046] wherein:

8453-1 IG - 25%TEDA, 4.5%TR90, and 70.5%EG 8453-35a - 25%TEDA, 9%TR90, and 66%EG

[0047] Examples D-G

[0048] For this set of examples, a pre-blend of B-component is prepared as in Table 1. These examples show that amines in combination with TEDA do not provide the back end cure that the blend of TR-90 and TEDA gives.

TABLE 3

[0049] wherein:

8453-8A = 23% TEDA/9% PMDETA/68% BDO 8453-8B = 23% TEDA/9% JEFFCAT® ZR-40 (pentamethyl dipropylenetriamine)/68% BDO

8362-49 = 23% TEDA/9% JEFFCAT® TAP (l-methyl-4-dimethylaminoethyl- piperazine)/68% BDO

[0050] Examples H-M

[0051] The following examples (H-M) show that catalyst blend of TEDA, TR-90, and other tertiary amines can improve the back-end cure (i.e., rebound pinch time) of the foam. In these examples, the catalyst and B-component are mixed for 10 seconds and the isocyanate is mixed with the mixture for 7 seconds. The cream time, rise time^ and foam height are collected on a Format rate of rise apparatus.

[0052] As can be seen in Table 4, similar cream times are seen for catalyst systems that include TEDA, TR-90 and other amines. The TR-90 containing systems (with or without the other amine) exhibit increased cure over the control (i.e., reduced pinch

time) and increased rise times. The rise heights of the foams are also increased with TR-90 containing systems.

[0053] The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Attorney Docket No.: 81697 PCT

Table 4