FIRE RETARDANT PAPER

Abstract

The invention relates to a fire retardant paper comprising reinforcing fibre, a fire retardant material and a binder system, wherein the binder system comprises a first organic binder and a second organic binder, wherein the first organic binder has a lower glass transition temperature than the second organic binder.

Claims

1. A fire retardant paper comprising reinforcing fibre, a fire retardant material and a binder system, wherein the binder system comprises a first organic binder and a second organic binder, wherein the first organic binder has a lower glass transition temperature than the second organic binder.

2. The fire retardant paper according to claim 1, having a flexibility value of less than 152 mm and a 20% compression value of at least 0.09 Mpa and a 60% compression value of at least 0.9 MPa.

3. The fire retardant paper according to claim 1, wherein the first organic binder has a glass transition temperature of less than 20° C.

4. The fire retardant paper according to claim 1, wherein the first organic binder has a glass transition temperature of less than 12° C.

5. The fire retardant paper according to claim 1, wherein the second organic binder has a glass transition temperature of greater than 20° C.

6. The fire retardant paper of claim 1, wherein the first organic binder has a glass transition temperature in a range of −100° C. to 45° C. and the second organic binder has a glass transition temperature in a range of 20° C. to 100° C.

7. The fire retardant paper according to claim 1, wherein a difference between the glass transition temperature of the second and first organic binders (Tg.sub.2−Tg.sub.1) is greater than 10° C.

8. The fire retardant paper according to claim 1, comprising: (A) 20 wt % to 65 wt % refractory fibre; (B) 0 wt % to 30 wt % organic fibre; (C) 5.0 wt % to 65 wt % fire retardant material; (D) 3.0 wt % to 30 wt % organic binder; and (E) 0 to 2.0 wt % inorganic binder, wherein a total of A+B+C+D+E is >80 wt %.

9. The fire retardant paper according to claim 1, comprising: (A) 25 wt % to 50 wt % refractory fibre; (B) 0 wt % to 15 wt % organic fibre; (C) 20 wt % to 60 wt % fire retardant material; (D) 5.0 wt % to 15 wt % organic binder; and (E) 0 to 2.0 wt % inorganic binder, wherein a total of A+B+C+D+E is >80 wt %.

10. The fire retardant paper according to claim 1, comprising at least 2 wt % organic fibre.

11. The fire retardant paper according to claim 1, further comprising an inorganic binder.

12. The fire retardant paper according to claim 1, wherein the reinforcing fibre comprises refractory fibre with less than 20 wt % shot (>45 μm).

13. The fire retardant paper according to claim 1, wherein a weight ratio of the first organic binder to the second organic binder is in a range of from 1:1 to 10:1.

14. The fire retardant paper according to claim 1, comprising: (i.) refractory fibre with less than 20 wt % shot (>45 μm); (ii.) less than 1.0 wt % inorganic binder; (iii.) the weight ratio of the first organic binder to the second organic binder is in a range of from 2:1 to 10:1; and (iv.) the first organic binder has a glass transition temperature in the range of −20° C. to 45° C. and the second organic binder has a glass transition temperature in a range of 20° C. to 100° C.

15. The fire retardant paper according to claim 1, wherein a weight ratio of the first organic binder to the second organic binder is greater than 2:1.

16. The fire retardant paper according to claim 1, wherein at least one of the first organic binder and/or the second organic binder is a heat reactive binder, wherein the fire retardant material comprises an endothermic material, and wherein the organic binder cross links below an activation temperature of the endothermic material.

17. The fire retardant paper according to claim 1, further comprising between 0.5 to 5 wt % of a reactive binder relative to a total weight of the organic binder.

18. The fire retardant paper according to claim 17, wherein the reactive binder has a curing temperature within 20° C. of an activation temperature of the endothermic material.

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. An energy storage device comprising the fire retardant paper as defined in claim 1.

25. A fire retardant laminate or layered structure comprising the fire retardant paper as defined in claim 1.

26. A fire retardant paper comprising reinforcing fibre, a fire retardant material, and a binder system, the binder system comprising two different binders, the fire retardant paper configured to have a flexibility value of greater than 21.5 to less than 152 mm, a 20% compression value of at least 0.09 Mpa, and a 60% compression value of at least 0.9 MPa and at most 5.0 MPa.

27. The fire retardant paper according to claim 26, wherein the binder system comprises a first organic binder having a glass transition temperature of less than 20° C., and a second organic binder having a glass transition temperature of greater than 20° C.

28. The fire retardant paper according to claim 27, wherein a difference in the glass transition temperature between the second and first organic binders is greater than 10° C.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0113] FIG. 1 is a graph of the compressive resistance (MPa) versus the % compression of an embodiment of the fire retardant paper of the present invention (Example 1) relative to a comparative example (Example 2).

[0114] FIG. 2 is a schematic diagram of the apparatus setup for the thermal performance test.

[0115] FIG. 3 is a graphic representation of the results of the thermal performance test.

DETAILED DESCRIPTION

[0116] The fire retardant paper can be prepared by combining and mixing the ingredients, such as by forming an aqueous slurry of the formulation ingredients, casting the slurry onto a paper making screen to form a paper web, and dewatering and drying the paper web into sheets or rolls using standard paper-making techniques as described, for example, in U.S. Pat. No. 3,458,329, the disclosure of which is incorporated by reference.

[0117] By way of further illustration, the fibres and binder may be combined to form a mixture or slurry. The slurry may be diluted with water to enhance formation, and it may be flocculated with a flocculating agent and drainage retention aid chemicals. Then, the flocculated mixture or slurry may be placed onto a papermaking machine to be formed into the paper. The sheets or rolls may also be formed by vacuum or tape casting the slurry or mixture with conventional equipment, and are typically dried in forced hot air ovens. Hand sheet moulds, a fourdrinier paper machine, a rotoformer paper machine, a vertical former or cylinders can be utilized to make the paper.

Example 1

[0118] Ingredients

[0119] Refractory fibre: Superwool® Max available from Thermal Ceramics Inc. The fibre has been cleaned to remove the shot levels (>45 μm) to a maximum of 10 wt % of the refractory fibre. Shot was removed using classification techniques as known in the art, with no substantial reduction in fibre length observed during the cleaning process.

[0120] Fibre B: Superwool Plus (grade 112) available from Thermal Ceramics Inc. The fibre has not been cleaned and has shot levels (>45 μm) of about 42 wt % of the refractory fibre.

[0121] Fibre C: Superwool HT available from Thermal Ceramics Inc. The fibre has not been cleaned and has shot levels (>45 μm) of about 42 wt % of the refractory fibre.

[0122] Fibre D: Evanite 706 microglass fibre available from Evanite Fiber Corporation.

[0123] Organic fibre: Bleached Eucalyptus Hardwood Pulp available from Fibria.

[0124] Fire Retardant: Aluminium Tri-hydrate (RJ Marshall 208ATH) with a D.sub.50 of 8 μm.

[0125] First organic binder: Binder A (see Table 1)

[0126] Second organic binder: Binder C (see Table 1)

[0127] Inorganic binder: Megasol® S50, a colloidal silica available from Wesbond with an average particle size of 70 nm.

[0128] Inorganic binder B: Levsil FO4020 is an aqueous amorphous silica solution (30-50 wt % silica) available from AzoNobel.

[0129] Flocculant: Percol 3232L available from BASF.

[0130] In addition to the above, where indicated, the following ingredients were also used in Examples 2 to 20.

[0131] Films formed from Hycar 26138 (Binder A), Acronal S 888 S (Binder E) or Acronal 4420 (Binder B) by the evaporation of water may already be partially cross linked on drying. The degree of crosslinking can be increased by heating them to between 150-180° C.

TABLE-US-00001 TABLE 1 Tg Binder Brand Description (° C.) A Hycar 26138 Available from Lubrizol: a heat reactive acrylic  25° C. copolymer latex in an aqueous solution (about 49 wt % solids) B Acronal 4420 Available from BASF: an aqueous dispersion of −11° C. a heat-crosslinking copolymer of acrylic esters (about 50 wt % solids). C Elvanol 71-30 Available from Kuraray: Polyvinyl alcohol −80° C. aqueous dispersion, (about X w t% solids). D Hycar 26083 Available from Lubrizol: A heat reactive, −15° C. carboxylated acrylic copolymer latex (about 52.5 wt % solids) E Acronal S Available from BASF: an aqueous dispersion of  31° C. 888S heat crosslinking copolymer of acrylic esters and styrene manufactured by a process incorporating acrylonitrile (about 49 wt % solids) F Acronal NX Available from BASF: an aqueous dispersion of  39° C. 5818 an n-butyl acrylate-acrylonitrile-styrene copolymer (about 48 wt % solids). G Acronal NX Available from BASF: aqueous copolymer  23° C. 4787 dispersion of butyl acrylate and styrene (about 50 wt % solids). H Rhoplex Available from Dow Chemicals: a styrenated −15° C. 2019RX acrylic polymer (about 50 wt % solids). I Rhoplex HA8 Available from Dow Chemicals: a self- −10° C. crosslinking, acrylic emulsion (about 45.5 wt % solids). J Rhoplex E-358 Available from Dow Chemicals: a self-  8° C. crosslinking, acrylic emulsion (about 60 wt % solids). K Rhoplex CS Available from Dow Chemicals: an 100% acrylic 32° C. 4000 polymer emulsion (about 48 wt % solids). L Rhoplex AC Available from Dow Chemicals: an 100% acrylic 27° C. 337N polymer emulsion (about 45.5 wt % solids).

[0132] Fused Silica: 3M™ Fused Silica 20 with a particle size distribution with less than 3 wt % greater than 45 μm available from Ceradyne Inc.

Examples 21 to 60

[0133] The following formula was used:

TABLE-US-00002 Water 15 US gal. Refractory fibre (Superwool ® Max) 390 g Bleached Eucalyptus Hardwood Pulp 72 g Aluminium trihydrate (RJ Marshall 208ATH) 360 g Binder #1 (see Tables 1 and 3) 132 g Binder #2 (see Table 1 and 3) 33 g Inorganic binder (Megasol ® S50) 10 g Flocculant (Percol 3232L) 7 drops

[0134] The approximate composition of the dried composition is presented in Table 3, based upon the binders comprising 50 wt % solids.

[0135] Method

[0136] The refractory fibre was added to a vessel containing being mixed under high agitation. The refractory fibre was mixed for 5 to 10 minutes prior to adding the organic fibre at a medium to high agitation speed. The fire retardant and first and second binders were then added and mixed for at least a further 5 minutes. The inorganic binder and flocculant were then added and mixed for a further 5 minutes. The slurry was then formed into a non-woven paper sheet using traditional wet laid equipment. The wet sheet was then dried to between 120° C. to 180° C. for about 1 hour so as to initiate some of the cross-linking in the binder system, but not activate the endothermic material. After drying, the material is rolled onto a 6 inch (152 mm) core for storage and transportation. The paper had a nominal thickness of approximately 2.0 mm. It will be appreciated that the thickness of the paper may be suitably adjusted during the paper making process.

[0137] Flexibility Test

[0138] The flexibility test was based upon section 8 of ASTM F137. The samples were conditioned for at least 24 hrs @ 72° F. +/−3° F. and 70% =/−5% Relative Humidity.

[0139] The flexibility of the paper is important in ensuring that that the paper and laminates thereof are able to be used in mass production continuous operation equipment, which typically require paper and other materials to be fed into a production line from a cylindrical reel from which the paper is wound onto.

[0140] As such, the flexibility test involves a 2″×10″ sheet of paper being rolled flush around a 6 inch (152 mm) cylinder. The paper is then unwound and visually inspected for cracking. If no cracking is observed with the naked eye, then the test is repeated for decreasing diameter cylinders down to the smallest diameter cylinder. The mandrel sizes used were 21.5 mm, 26.7 mm, 33.3 mm, 42.2 mm, 48.5 mm, 60.4 mm, 88.9 mm, 114 mm, and 152 mm.

[0141] The flexibility value of the paper is measured by the diameter of the cylinder prior to the diameter at which a crack was first visually detected (i.e. if crack first detected at a 33.3 mm diameter, then the flexibility value would be the preceding diameter of 42.2 mm). For samples which crack at the largest mandrel size, a flexibility value of >152 mm was given. Samples with a flexibility value of 21.5 mm (lowest measured value) may have a lower flexibility value if small mandrel diameters were used.

[0142] A flexibility measurement value is should be at or below the diameter of the reel diameter used in the manufacturing environment. The lower the flexibility value the less likely the paper will crack during the manufacturing process.

[0143] Compressive Strength Test

[0144] The paper is required to a degree of compressive strength to securely package the cells in normal operation as well as withstanding swelling of individual cells during a thermal event. As such, the paper preferably has an ability to deform slightly (e.g. 20% compression of the original thickness of the paper) under moderate force used to assemble a battery pack as well as withstanding higher forces whilst still providing a mechanical barrier between cells (e.g. 60% compression of the original thickness of the paper).

[0145] FIG. 1 illustrates the compressive strength properties of Example 1 (laboratory made and pilot plant made) versus Example 2 (a comparative example with a single organic binder). The results indicate that the compressive resistance of Example 2 is significantly below that of Example 1. Further, the flexibility of Example 1 was better than Example 2, with the partial substitution of a “hard” organic binder for an inorganic binder in example 1 resulting in improved flexibility and compressive resistance.

[0146] The compression force used to compress the thickness of the paper (nominal 2 mm thickness) by up to 80% of the original thickness was performed using a Tinius Olsen test unit with a load cell capable of handling 10 KN force. The results of the compression force (compression value) required to obtain 20%, 60% and selective 50% compression are provided in Tables 2 & 3.

[0147] The results from Table 2 illustrate that paper with relatively high amounts of inorganic binder or with high shot levels (e.g. >10 wt %) generally do not have sufficient flexibility to be used for mass production techniques requiring continuous feeding of the paper from a reel.

[0148] A comparison of Examples 11 to 14 highlights the detrimental effect of having elevated shot levels with the compressive strength significantly decreasing in the samples containing uncleaned refractory fibres (Examples 11 & 13). It is thought that the presence of shot particles reducing the effective bridging of the binders with the fibrous material, thereby reducing the ability of the paper to absorb compressive forces.

[0149] The comparison of Examples 1 & 7 demonstrates how relatively small changes in organic binder content can significantly affect the compressive strength properties of the paper.

TABLE-US-00003 TABLE 2 Organic Organic 20% 60% (50%) Refractory Organic Fire Inorganic Binder Binder Flex Compression Compression Binder Example Fibre Fibre Retardant Binder #1 #2 test Mpa Mpa O/I B1/B2 1 42.78 7.91 39.54 0.55 7.40 1.82 88.9 0.20/0.31 1.52/1.74 16.8 4.1 2 42.11 7.97 39.86 1.79 9.15 — 152 0.05 0.80 (0.51) 5.1 — 3 41.23 7.98 39.88 3.45 7.46 — >152 0.25 1.45 2.2 — 4 41.22 7.97 39.86 1.66 7.46 1.83 33.3 0.30 1.57 5.6 4.1 5 41.22 7.97 39.86 1.66  7.46 B 1.83 88.9 0.15 1.02 5.6 4.1 6 42.79 7.91 39.56 1.78 7.40 0.56 152 0.13 1.21 4.5 1.3 7 41.26 7.98 39.90 0.55 8.47 1.83 114 0.12 1.12 18.7 4.6 8  42.36 B 7.83 39.16 0.54 8.31 1.80 >152 0.14 1.20 18.7 4.6 9  42.37 B 7.83 39.17 1.76 8.31 1.76 >152 0.12 1.13 (0.78) 5.7 4.7 10  41.26 B 7.98 39.90 0.55 8.47 1.83 >152 0.25 1.54 18.7 4.6 11  42.38 B 5.68 40.99 1.71 7.36 1.88 >152 0.18 1.38 5.4 3.9 12 42.38 5.68 40.99 1.71 7.36 1.88 >152 0.28 1.78 5.4 3.9 13  42.38 B 5.68 40.99 1.71 7.36 1.88 152 0.09 0.97 5.4 3.9 14 42.38 5.68 40.99  1.71 B 7.36 1.88 >152 0.20 1.41 5.4 3.9 15  42.01 B 4.17 40.63 1.69 8.62 2.87 114 0.13 1.24 6.8 3.0 16  34.56 C 3.24 21.60# 2.70  2.75 B 2.75 114 0.08 — (0.52) 2.0 1.0   5.40 D 17  34.56 B 3.24 21.60# 2.70  2.75 B 2.75 152 0.08 — (0.55) 2.0 1.0   5.40 D 18  37.79 B 2.16 21.59# 1.62  3.85 B 2.75 152 0.08 — (0.50) 4.1 1.4   3.24 D 19 41.09 6.32 37.98 0.54 5.27 3.42 + 48.5 0.06 — (0.56) 26.0 0.6 5.37 C 20 43.19 6.64 39.92 0.54 5.65 1.83 + 88.9 0.13 — (0.78) 17.9 1.4 2.21 C 21-60 39.0  7.2 36.0 1.0  13.2  3.3 See Table 3 #further contains 27 wt % fused silica O/I signifies the weight ratio of the organic binder to the inorganic binder B1/B2 signifies the weight ratio of the organic binder #1 to the organic binder #2 Unless indicated otherwise (e.g. 37.79 B), the ingredients used are those used in Example 1. The compression value for example 1 relate to a laboratory made and a plant trial made formula respectively.

TABLE-US-00004 TABLE 3 Tg(2) − Wt Mean 20% 60% binder Tg(2) binder Tg(1) Tg(1) T.sub.g Flexibility compression compression Example #2 ° C. #1 ° C. ° C. ° C. mm MPa MPa 21 F 39 G 23 16 26.2 48.5 0.159 1.724 22 F 39 B  11* 28 16.6 33.3 0.113 1.223 23 F 39 H −15  54 −4.2 26.7 0.147 1.887 24 F 39 I −10* 49 −0.2 26.7 0.182 1.962 25 F 39 J  8* 31 14.2 26.7 0.100 1.283 26 F 39 D −15* 54 −4.2 21.5 0.195 1.823 27 F 39 A  25* 14 27.8 88.9 0.153 1.535 28 G 23 B  11* 12 13.4 21.5 0.136 1.801 29 G 23 H −15  38 −7.4 21.5 0.120 1.341 30 G 23 I −10* 33 −3.4 21.5 0.127 1.587 31 G 23 J  8* 15 11 21.5 0.137 1.359 32 G 23 D −15* 38 −7.4 21.5 0.122 1.563  33** A  25* G 23 2 24.6 60.4 0.102 1.196 34 K 32 G 23 9 24.8 60.4 0.091 1.195 35 K 32 B  11* 21 15.2 26.7 0.082 1.241 36 K 32 H −15  47 −5.6 21.5 0.165 1.493 37 K 32 I −10* 42 −1.6 21.5 0.138 1.370 38 K 32 J  8* 24 12.8 21.5 0.095 1.150 39 K 32 I −15* 47 −5.6 26.7 0.150 1.551 40 K 32 A  25* 7 26.4 88.9 0.108 1.345 Tg(2) − Wt Mean 20% 60% binder Tg(2) binder Tg(1) Tg(1) Tg Flexibility compression compression Example #2 ° C. #1 ° C. ° C. ° C. mm MPa MPa 41 L 27 G 23 4 23.8 42.2 0.103 0.954 42 L 27 B  11* 16 14.2 26.7 0.137 1.424 43 L 27 H −15  42 −6.6 26.7 0.158 1.575 44 L 27 I −10* 37 −2.6 21.5 0.148 1.488 45 L 27 J  8* 19 11.8 21.5 0.191 1.750 46 L 27 D −15* 42 −6.6 26.7 0.128 1.255 47 L 27 A  25* 2 25.4 60.4 0.266 2.056 48 E  31* G 23 8 24.6 60.4 0.231 2.140  49a E  31* B  11* 20 15 33.3 0.164 1.688  49b E  31* B  11* 20 15 152 0.504 3.614 50 E  31* H −15  46 −5.8 33.3 0.136 1.739 51 E  31* I −10* 41 −1.8 26.7 0.128 1.139 52 E  31* J  8* 23 12.6 26.7 0.093 1.340 53 E  31* D −15* 46 −5.8 21.5 0.136 1.437 54 C 80 G 23 57 34.4 114 0.148 1.797 55 C 80 B  11* 69 24.8 114 0.151 2.452 56 C 80 H −15  95 4 21.5 0.176 2.072 57 C 80 I −10* 90 8 21.5 0.116 1.683 58 C 80 J  8* 72 22.4 21.5 0.093 1.185 59 C 80 D −15* 95 4 21.5 0.120 1.431 60 C 80 A  25* 55 25 114 0.180 2.685 *contains a heat activated cross-linking agent **132 g binder #2 and 33 g of binder #1

[0150] Examples 2 & 3 highlight the difficulties in obtaining both good compressive strength and the required flexibility through the use of a single organic binder. With Example 1, 7 and 20 illustrating that the use of two or more binders is able to deliver the required properties for the fire retardant paper. While the 60% compression test was not performed for Example 20, it may be deduced from the 50% compression results that Example 20 would have had a similar 60% compression result to that of Example 9.

[0151] It will be appreciated that the level of flexibility may also be increased through lowering the amount or type of fire retardant material.

[0152] The flexibility and compressive strength test were performed at approximately 21° C.

[0153] Thermal Performance

[0154] The fire retardant paper has the function to prevent thermal runaway between neighbouring cells and, as such, it is important that the temperature of the paper furthest away from the thermal event (i.e. the cold face) is kept as low as possible and below a temperature which is likely to result in the thermal event extending to the neighbouring cell.

[0155] The paper produced in accordance to Example 1 (2.0 mm thick) was tested by placing a sample in an insulated chamber according to the configuration illustrated in FIG. 2. The heat gun was set at a temperature of 500° C. for 10 minutes, with the temperature of the cold face 10 recorded over time, with the results provided in FIG. 3.

[0156] The performance of Example 1 was compared to a 2.0 mm paper comprising 93.6 wt % Superwool® Plus and 5.0 wt % Arconal 420 S (Tg: −6° C.) and 1.4 wt % Arconal S 888S (Tg: 31° C.). As illustrated in FIG. 3, the paper of the present disclosure has is able to maintain a lower cold face through a combination of the insulation and endothermic properties of the paper.

[0157] Effect of Binder

[0158] Examples 21 to 60 were designed to assess the impact of different combination of polymeric binders. All other components of the of the paper were kept the same, with the binder components varied. Example 49b is Example 49a held at 180° C. for 1 hour to activate the in-situ cross-linking agent.

[0159] The following observations were made: [0160] Improved flexibility was obtained when second (softer) binder had a lower T.sub.g, with the maximum flexibility achieved with a T.sub.g of 11° C. or lower (e.g. Examples 26, 28-32, 37, 38, 44, 45, 56-59). [0161] While increased flexibility generally correlated with a lower weight mean glass transition temperature of the binder system, as indicated in Example 58, having a minor proportion of a softer binder (e.g. T.sub.g below 11° C. or lower) is sufficient to maintain good flexibility in the paper. [0162] The drying of the paper does not appear to have resulted in significant cross-linking of the heat activated polymers, with binders D and H behaving similarly, despite binder D comprising a heat activated cross-linking agent. [0163] The activation of cross-linking of the binder system has the ability to significantly increase the compression resistance of the paper, whilst decreasing paper flexibility ((Examples 49a & 49b). The skilled artisan would be able to take the teachings of Examples 49a & 49b to produce a fire retardant paper under the second aspect of the present disclosure.

[0164] Applications

[0165] While the paper is particularly advantageous when used as spacers between pouch cells, the fire retardant paper may find applications outside of those in energy storage devices. For example, the fire retardant paper may be used to protect electronics and cabling from fire and/or be used in compact spaces such as the aerospace, automobile or shipping industry. The paper may also be used in heat shield applications.

[0166] Reference throughout this specification to “one embodiment,” “certain embodiments,” “various embodiments,” “one or more embodiments” or “an embodiment” and the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in various embodiments,” “in one embodiment” or “in an embodiment” and the like in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

[0167] Although the disclosure herein provided a description with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope thereof. Thus, it is intended that the present disclosure include modifications and variations that are within the scope of the appended claims and their equivalents.