BACKGROUND

[0001] Isocyanates are used in various industrial products and are well known as a chemical used in urethane, pesticides and plastic industries. Isocyanates are highly reactive and have low molecular weight. Due to their high reactivity, isocyanates crystallize during storage, resulting in short shelf lives. Once isocyanates crystallize, they may be not used to manufacture polyurethane and other industrial products, leading to product waste. Therefore, the short of the shelf life of isocyanates is highly undesirable. Accordingly, there exists a need for a method to extend the shelf lives of isocyanates.

SUMMARY

[0002] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0003] In one aspect, embodiments disclosed herein relate to method for extending shelf life of polymeric isocyanate with composition containing hydrotalcite.

[0004] In one aspect, embodiments disclosed herein relate to a composition containing an isocyanate and a hydrotalcite additive. The hydrotalcite additive may be a dehydrated hydrotalcite and/or hydrated hydrotalcite.

[0005] In another aspect, embodiments disclosed herein relate to a method for producing the composition containing the isocyanate and the hydrotalcite additive. The method may include mixing the hydrotalcite additive with the isocyanate.

[0006] In yet another aspect, embodiments disclosed herein relate to a method for stabilizing the isocyanate. The method may include mixing the hydrotalcite additive with the isocyanate to form a mixture, absorbing at least one of a H2O molecule and an anion from the mixture into a crystal structure of the hydrotalcite additive, and maintaining the mixture for a period of time. [0007] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a flow chart of a method for stabilizing an isocyanate in accordance with one or more embodiments.

[0009] FIG. 2 is a schematic depiction of an anion exchange mechanism between an anion and hydrotalcite in accordance with one or more embodiments.

[0010] FIG. 3 is a schematic depiction of a water absorbing mechanism and anion absorbing mechanism of dehydrated hydrotalcite in accordance with one or more embodiments.

DETAILED DESCRIPTION

[0011] Hydrotalcites have excellent acid reactivity and anion exchange ability. They may be used in various applications such as medical (e.g., antacids) and wastewater treatment. In one or more embodiments of the present disclosure, hydrotalcite may be used as an additive to absorb reactive compounds in isocyanate mixtures and may stabilize isocyanates to extend the shelf life of isocyanates.

[0012] Specific embodiments of the disclosure will now be described in detail.

[0013] In the following Detailed Description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

COMPOSITION

[0014] In one aspect, embodiments disclosed herein relate to a composition used to extend the shelf life of isocyanates. The composition of one or more embodiments includes an isocyanate and a hydrotalcite additive. Hydrotalcite Additive

[0015] In one or more embodiments, the additive included in the composition may be a hydrotalcite (hydrotalcite additive). The hydrotalcite disclosed herein may have a layered crystal structure where every other layer is composed of hydroxides (alternating layers). In between the hydroxide layers are metallic layers including M ²⁺ and/or M ³⁺ or FhO/A ¹¹ ’ layers.

[0016] In one or more embodiments, the hydrotalcite may be represented by formula (I):

(M ²⁺ )i-p(M ³⁺ )p(OH)2(A ⁿ -)(p/ _n )-mH2O formula (I)

[0017] wherein M ²⁺ is a divalent metal cation, M ³⁺ is a trivalent metal ion, A ¹¹ ’ is an anion where n- is a charge of the anion with an integer of 1 to 6, p is 0.17 < p < 0.36, and m is 0 < m < 10.

[0018] In one or more particular embodiments, M ²⁺ is Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Zn ²⁺ , Mn ²⁺ , Co ²⁺ , MO ²⁺ , Ni ²⁺ , Fe ²⁺ , Sr ²⁺ , Cu ²⁺ , or mixtures thereof. In particular embodiments, M ²⁺ is Mg ²⁺ ,Ca ²⁺ , Zn ²⁺ ,Mn ²⁺ ,Ni ²⁺ ,Fe ²⁺ , or mixtures thereof.

[0019] In one or more particular embodiments, M ³⁺ is B ³⁺ , Al ³⁺ , Ga ³⁺ , In ³⁺ , Bi ³⁺ , Fe ³⁺ , Cr ³⁺ , Co ³⁺ , Sc ³⁺ , La ³⁺ , Ce ³⁺ , or mixtures thereof. In particular embodiments, M ³⁺ is Al ³⁺ , Fe ³⁺ , or mixtures thereof.

[0020] In one or more particular embodiments, A ¹¹ ’ is CO3’ ² , CIO ^4- , Cl’, NO3’, SO4’ ² , PO4’ ³ , or mixtures thereof. In particular embodiments, A ¹¹ ’ is CO3’ ² .

[0021] In one or more embodiments, the hydrotalcite additive included in the composition may be a dehydrated hydrotalcite. As used herein, “dehydrated hydrotalcite” refers to a hydrotalcite composition that has 1 wt% (weight percent) of water or less in its crystal structure. In one or more embodiments, the dehydrated hydrotalcite may be represented by formula (II):

(M ²⁺ )i- _x (M ³⁺ ) _x (OH)2- _y (A ⁿ -)( _[x / _n]-z) -wH2O formula (II)

[0022] wherein M ²⁺ , M ³⁺ , and A ¹¹ ’ are as described above with reference to formula (I), and wherein x is 0.2 < x < 0.34, y is 0 < y < 0.7, z is 0 < z < (x/n), and w is 0 < w < 0.34. [0023] In one or more embodiments, the dehydrated hydrotalcite may alternatively be represented by formula (III):

(M ²⁺ )i-a(M ³⁺ ) _a O (H ₂ O)i-b(A ^I1 -)( _[ a/ _n ]-c)-dH ₂ O formula (III)

[0024] wherein M ²⁺ , M ³⁺ , and A ^11- are as described above with reference to formula (I), and wherein a is 0.2 < a < 0.34, b is O < b < l, c is O < c < (x/n), and d is 0 < d < 0.34

[0025] Examples of commercially available dehydrated hydrotalcites include, but are not limited to, DHT™-4C and KW-2200 (Kyowa Chemical Industry Co., Ltd, Kagawa, Japan).

[0026] In one or more embodiments, the hydrotalcite additive included in the composition may be a hydrated hydrotalcite. In one or more embodiments, hydrated hydrotalcite may be represented by formula (I) as described above. As used herein, “hydrated hydrotalcite” refers to a hydrotalcite composition that has more than 1 wt% (weight percent) of water its crystal structure.

[0027] An example of a hydrated hydrotalcite includes, but is not limited to, DHT®-4V (Kisuma Chemicals, Veendam, Netherlands).

[0028] In one or more embodiments, the hydrotalcite may be in the form of a powder. In such embodiments, the particles in the hydrotalcite powder may have an average particle size (D50) of from 0.1 to 0.8 pm. For example, the D50 particle size may have a lower limit of any one of 0.1, 0.2, 0.3, 0.4, and 0.5 and an upper limit of any one of 0.4, 0.5, 0.6, 0.7 and 0.8 pm, where any lower limit may be paired with any mathematically compatible upper limit. The D50 particle size refers to a median particle diameter or median particle size, where the cumulative percentage reaches 50%. For example, if the D50 is from 0.1 to 0.8 pm, 50% of the particles have a particle size of from 0.1 to 0.8 microns and the remainder have a particle size less than or equal to 0.1 microns and greater than or equal to 0.8 microns. The D50 particle size is measured using a laser diffraction scattering method known by those skilled in the art.

[0029] The hydrotalcite of one or more embodiments may have an MgO/Al ₂ O3 molar ratio of from 3.0 to 7.0. For example, hydrotalcite of one or more embodiments may have a MgO/Al ₂ O3 molar ratio in a range having a lower limit of any one of 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5, and having an upper limit of any one of 3.5 ,4.0, 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0, where any lower limit may be paired with any mathematically compatible upper limit.

[0030] The hydrotalcite of one or more embodiments may have a loss on drying of less than 1.0 weight%, such as less than 0.8 weight%, or less than 0.5 weight%, or less than 0.3 weight%, or less than 0.1 weight%, or 0.0 weight % (105 °C for 1 hour). In one or more embodiments, the hydrotalcite may have a loss on drying of less than 5.0 weight%, such as less than 4.5 weight%, or less than 4.0 weight%, or less than 3.0 weight%, or less than 1.0 weight%, or 0.0 weight % (250°C for 1 hour).

[0031] The hydrotalcite of one or more embodiments may have a loss on heating (300°C for 1 hour) of from 0.0 to 5.0 weight%. For example, hydrotalcite of one or more embodiments may have loss on heating in a range having a lower limit of any one of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 weight%, and having an upper limit of any one of 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 4.6, 4.7, 4.8, 4.9, and 5.0 weight%, where any lower limit may be paired with any mathematically compatible upper limit.

[0032] The hydrotalcite of one or more embodiments may have a specific surface area (BET) of from 2 to 250 m ² /g. The hydrotalcite of one or more embodiments may have a BET in a range having a lower limit of any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50 ,60 ,70, 80, 90, 100, 110, 120, 130, 140, and 150 m ² /g, and having an upper limit of any one of 15, 20, 25, 30, 50, 75, 100, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, and 250 m ² /g, where any lower limit may be paired with any mathematically compatible upper limit.

[0033] The hydrotalcite of one or more embodiments may have a total heavy metals content of 10 parts per million (ppm) or less, such as less than 9 ppm, less than 8 ppm, less than 7 ppm, less than 6 ppm, less than 5 ppm, less than 4 ppm, less than 3 ppm, less than 2 ppm, or less than 1 ppm. The heavy metals disclosed herein may be any heavy metals except for Mn, Fe, Zn, Co, Cu, Mo, and Ni, which may be main components of hydrotalcite.

[0034] The hydrotalcite may be included in the composition in an amount ranging from

0.10 to 1.0 weight % based on the total mass of the composition. The hydrotalcite may be included in the composition in a range having a lower limit of any one of 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, and 0.55 weight %, and an upper limit of any one of 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 1.0 weight %, where any lower limit may be paired with any mathematically compatible upper limit.

[0035] The hydrotalcite of one or more embodiments may be coated or uncoated. An uncoated hydrotalcite does not include a surface treatment. A coated hydrotalcite includes a surface treatment. Examples of a suitable surface treatment agent are saturated fatty acid based or salts thereof, such as stearic acid or stearate. An example of a coated hydrated hydrotalcite is DHT®-4V (Kisuma Chemicals, Veendam, Netherlands). An example of an uncoated dehydrated hydrotalcite is KW-2200 (Kyowa Chemical Industry Co., Ltd, Kagawa, Japan).

Isocyanate

[0036] As noted above, compositions in accordance with the present disclosure include an isocyanate and an hydrotalcite additive. In one or more embodiments, the isocyanate in the composition may be represented by formula (IV): formula (IV)

[0037] where R is a hydrogen atom or a hydrocarbon group. As used throughout this description, the term “hydrocarbon group” may refer to branched, straight chain, and/or ring-containing hydrocarbon groups, which may be saturated or unsaturated. The hydrocarbon groups may be primary, secondary, and/or tertiary hydrocarbons.

[0038] Furthermore, in one or more embodiments, the isocyanate may be a diisocyanate, represented by formula (V):

N=C=O

R ¹ / O — C — N formula (V)

[0039] where R ¹ is a hydrocarbon group.

[0040] In one or more embodiments, examples of the isocyanate may include, but are not limited to, diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI) and isomers thereof (such as toluene 2,4-diisocyanate and toluene 2,6-diisocyanate), 1,5- naphthalene diisocyanate (NDI), para-phenylene diisocyanate (PPDI), dicyclohexane diisocyanate (HMDI), and meta-tetramethylxylene diisocyanate (TMXDI).

[0041] In one or more embodiments, the isocyanate disclosed herein may be selected from the group consisting of a polymeric isocyanate, a monomeric isocyanate and combinations thereof. The polymeric isocyanate may be a polyisocyanate or an isocyanate prepolymer.

[0042] Isocyanates are widely available commercially and different types of isocyanates may be selected based on the end use. Examples of commercially available isocyanates include, but are not limited to, PAPI™ 27, PAPI™ 94, PAPI™ 95 (DOW Chemical Company, Midland, Michigan, USA), Lupranat® T 80 A, Lupranat® M 10R, Lupranat® M 20R (BASF SE, Ludwigshafen, Germany), Desmodur® XP 2838, Desmodur® XP N 3400, Desmodur® BL 5375, Desmodur® XP 2406, and Desmodur® BL 4265 SN (Covestro AG, Leverkusen, Germany).

METHOD OF MAKING THE COMPOSITION

[0043] In one aspect, embodiments disclosed herein relate to a method of making the previously described composition. The method may include mixing at least one isocyanate with an hydrotalcite additive as described above. The mixing may be performed using any mixing means known in the art. For example, in one or more embodiments, the composition may be mixed with a high shear mixing blade at an appropriate speed, such as from 1500 to 2500 rpm. Any suitable mixing equipment may be used provided it has enough force to mix the hydrotalcite additive with the isocyanate such that the hydrotalcite additive is evenly dispersed in the isocyanate. The hydrotalcite additive may be mixed at a suitable temperature, such as a temperature of from 20 to 45°C. Sufficient mixing has been conducted when no clumps are visible in the isocyanate/hydrotalcite mixture.

Method for stabilizing an isocyanate

[0044] Isocyanates are known to be highly reactive with water and acids, especially when ionized into their respective anions and hydronium ions. Acids may exist in isocyanates because they are byproducts of the isocyanate manufacturing process. For example, hydrochloric acid is formed as a byproduct when reacting amine and phosgene to produce isocyanate. Hydrotalcite may reduce the amount of water and chloride ions from hydrochloric acid in isocyanate mixtures, which reduces polymerization of isocyanate, thereby stabilizing the isocyanate and extending its shelf life. As will be appreciated by those skilled in the art, while the present disclosure uses residual hydrochloric acid to explain the possible mechanisms of how hydrotalcite stabilizes isocyanates, other trace impurities may also be mitigated by the use of hydrotalcite. Thus, in one aspect, embodiments disclosed herein relate to a method of stabilizing an isocyanate with hydrotalcite.

[0045] FIG. 1 is a flow chart of a method for stabilizing an isocyanate 10 in accordance with one or more embodiments of the present disclosure. First, the hydrotalcite additive and the isocyanate may be mixed to form a mixture 101. The mixing may be performed as described above. The hydrotalcite may then absorb at least one of a H2O molecule and an anion from the isocyanate mixture into the crystal structure of the hydrotalcite 102. The anion in the isocyanate is generally an anion of an acid, such as hydrochloric acid (i.e., a chloride ion). The obtained mixture may be maintained for a period of time to stabilize the isocyanate 103.

[0046] FIG. 2 shows a schematic depiction of a hydrotalcite structure and the general scheme of how hydrotalcite can undergo an anion exchange reaction between anions in acids such as chloride ions and A ^11- anions in the hydrotalcite structure. Hydrotalcite has a layered crystal structure 20 containing base layers 201 and interlayers 202. The base layers 201 contain hydroxides 2011 and metals which include M ³⁺ 2012 and M ²⁺ 2013. The interlayers 202 contain H2O molecules 2021 and A ^11- ions 2022. The mixture of isocyanate and hydrotalcite may include acids 30. Anions 3001 of the acids 30 may be incorporated into the site of the A ^11- 2022 in interlayers 202, resulting in having anions 3001 in the crystal structure of the hydrotalcite as shown in structure 21. The A ^11- 2023 that was originally in interlayers 202 will react with protons (hydrogen ions, 3002) of the acids 30. When A ^11- is CO3 ² ’, CO2 22 and H2O 23 are produced as byproducts.

[0047] FIG. 3 shows a schematic depiction of a dehydrated hydrotalcite structure and the general scheme of how hydrotalcite can absorb water molecules into its crystal structure. The dehydrated hydrotalcite can undergo the anion exchange reaction described above with regard to FIG. 2, but also advantageously has less water and A ^11- in the crystal structure, allowing for water absorption and anion absorption as well. As shown in FIG. 3, hydrotalcite has a layered crystal structure 40 where every other layer is composed of hydroxides 401. In between the hydroxide layers 401 are metallic layers 402 which include M ³⁺ 4021 and/or M ²⁺ 4022 or FhO/A ^11- layers 403. The FLO/A ^11- layers 403 include H2O molecules 4031 and A ^11- ions 4032. Dehydrated hydrotalcite may be missing H2O molecules and A ^11- ions from the FLO/A ^11- layers 403 and may have empty sites 4033 and 4034. When dehydrated hydrotalcite is present in a mixture with an isocyanate, the H2O molecules 5001 and anions 3001 of acids 30 in the mixture may be incorporated into the empty sites 4033 and 4034 in the FhO/A ^11- layers 403, resulting in having additional H2O molecules and anions in the crystal structure of the hydrotalcite as shown in structure 41.

[0048] As noted above, in one or more embodiments, the mixture of hydrotalcite additive and isocyanate may be maintained for a period of time in order to stabilize the isocyanate, thereby increasing its original shelf life. This may be performed by sealing the mixture in a container and storing it at room temperature or elevated temperature for a period of time. During this time the aforementioned ion exchange, ion absorption, and water absorption mechanisms may occur, thereby stabilizing the isocyanate mixture. Conventionally, isocyanates must be used almost immediately once opened because of their sensitivity to moisture in ambient conditions. If they are opened and then resealed, they rapidly degrade and polymerize, rendering them unusable after being exposed to ambient conditions. Advantageously, as explained above, hydrotalcite has the ability to scavenge moisture from the environment, thereby reducing the degradation of isocyanate when exposed to air. As such, isocyanates may be opened, used, closed, and reopened for additional use at a later date when stabilized by hydrotalcite.

[0049] Due to the fact that the isocyanate may remain stable for significantly longer in the presence of the hydrotalcite additive, the isocyanate may be effectively used after a period of time. The presence of the hydrotalcite may not hinder the reactivity of the isocyanate itself, so it may be used for normal purposes. For example, in one or more embodiments, the mixture of the isocyanate and the hydrotalcite additive may be reacted with at least one polyol to form polyurethane. [0050] The shelf life of the isocyanate and hydrotalcite mixtures disclosed herein may be measured as compared to reference samples using the following method. A change in viscosity over time may be used as a proxy for the shelf life of the isocyanate. It is desirable that the mass and viscosity of the isocyanates do not change over time, as such changes are indicative of polymerization and/or decomposition. Therefore, these properties may be measured at various time intervals for isocyanates that have been exposed to open air to determine the effectiveness of the hydrotalcite additive in extending shelf life.

[0051] In one or more embodiments, the initial viscosity and mass of a mixture of hydrotalcite additive and isocyanate may be measured and then the mixture may be stored at a suitable temperature for each type of isocyanate, such as 55 to 65 °C, for a period of time. The viscosity may be measured with any rotational viscometer known in the art. For example, in one or more embodiments, the viscosity of the mixture may be measured with a Brookfield viscometer according to ASTM 2196D. Measurements of mass and viscosity may be taken at any interval, such as once per week. The measurements of viscosity and mass of the mixture may be repeated until a solid film is formed on the samples or after a predetermined period of time, such as one month.

[0052] Generally, different types of isocyanates may have different specifications for the viscosity as an indicator for product quality. In one or more embodiments, isocyanates having viscosity in a range of the specification may have no solid films of isocyanates formed in the mixture; that is, isocyanate may have not reached the end of the shelf life and is still in good use. For example, commercial isocyanate PAPI™ 27 has a viscosity range of from 150 to 220 cPs (centipoise) at a temperature of 25 °C, and in this viscosity range PAPI™ 27 is of good quality.

[0053] In contrast, isocyanates of one or more embodiments having a solid film formed in the mixture indicates that the isocyanate has reached its shelf life. Alternatively, isocyanates of one or more embodiments may react with reactive compounds and start to polymerize. An indication of such polymerization processes is when the mixture has a viscosity outside the specification range and/or has substantial change in viscosity. For example, if the viscosity of a sample doubles, it can be said to have experienced a “substantial change” in viscosity.

[0054] In one or more embodiments, the extension of shelf life of isocyanate may be proportional to the amount of residual anions and moisture in the mixture. When the amount of hydrotalcite in the isocyanate is enough to absorb the residual anions and moisture, the isocyanate may be stabilized, thereby extending the shelf life. As noted above, anions may originate from acids that may be contained in the isocyanate and the amount of acids, therefore, depends on type of isocyanates.

EXAMPLES

[0055] Isocyanate sample preparation

[0056] DHT™-4C and KW-2200 were obtained from Kyowa Chemical Industry Co., Ltd and PAPI™ 27 polymeric MDI was obtained from DOW Chemical Company.

[0057] Isocyanate samples with different additives were prepared by the method as described above. 0.25 wt.% of additives were added to the isocyanate and mixed with Cowles mixing blade at 2000 rpm for 10 minutes at room temperature. The obtained mixtures were sealed in a container and stored in a chamber at 60 °C using a Hepa Filtered IR Incubator.

[0058] Example 1 was a mixture of polymeric MDI and dehydrated hydrotalcite (DHT™-4C). 0.25 wt.% of DHT™-4C was added to the polymeric MDI based on the total mass of the composition.

[0059] Example 2 was a composition of polymeric MDI (PAPI™ 27) and dehydrated hydrotalcite like aluminum magnesium oxide (KW-2200). 0.25 wt.% of KW-2200 was added to the polymeric MDI based on the total mass of the composition.

[0060] Comparative Example 1 was a standard polymeric MDI (PAPI™ 27) with no additives. A mixing step as described above was not performed on this example.

[0061] The viscosity and mass of each sample was measured over time to evaluate the shelf life of isocyanate. The initial viscosity and mass of each mixture of isocyanate was measured per ASTM D2196 (American Society for Testing and Materials). Viscosity was measured using a Brookfield viscometer with spindle No. 4 at a rotation speed of 20 rpm and a dial torque of from 0.9 to 5. The temperature of the samples was 26.6°C. Then the samples were stored at a temperature of 60°C for several weeks. Measurements of mass and viscosity were taken at the intervals shown in Table 1. The measurements of viscosity and mass of the mixtures were repeated until a solid film was formed on the samples or after a predetermined period of time. The change in viscosity of each sample is shown in Table 1.

[0062] Table 1: Viscosity change of the Examples and Comparative Examples

[0063] As shown in Table 1, Comparative Example 1 formed a solid film after 18 days of storage and Example 2 formed a solid after 29 days of storage. In contrast, the viscosity of Example 1 increased but did not form a solid for the duration of the experiment. This result shows that hydrotalcite stabilized the MDI and extended the shelf life of isocyanate.

[0064] Example 2 that contains KW-2200 showed a substantial increase in viscosity compared to Example 1. However, KW-2200 stabilized the MDI since MDI with no additive (Comparative Example 1) formed a solid before Example 2 (KW-2200 containing mixture).

[0065] The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.

[0066] As used here and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.

[0067] When the word “approximately” or “about” are used, this term may mean that there can be a variance in value of up to ±10%, of up to 5%, of up to 2%, of up to 1%, of up to 0.5%, of up to 0.1%, or up to 0.01%.

[0068] “Optionally” and all grammatical variations thereof as used refers to a subsequently described event or circumstance that may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. [0069] The term “substantially” and all grammatical variations thereof as used refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0070] Ranges may be expressed as from about one particular value to about another particular value, inclusive. When such a range is expressed, it is to be understood that another one or more embodiments are from the one particular value to the other particular value, along with all particular values and combinations thereof within the range.

[0071] While the disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the attached claims.

[0072] Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims.

[0073] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.