阅读说明：本技术 一种低铁勃姆石及其制备方法和应用 (Low-iron boehmite and preparation method and application thereof ) 是由 谢庚彪 车洪生 刘现民 苏静波 周跃华 于 2021-09-24 设计创作，主要内容包括：本发明特别涉及一种低铁勃姆石及其制备方法和应用,属于勃姆石材料技术领域,方法包括：将原料氢氧化铝溶于第一溶剂中,后与酸液混合并研磨,得到第一溶液；将所述第一溶液进行水浴,后过滤洗涤,得到滤饼；将所述滤饼溶于第二溶剂,后加入添加剂,得到第二溶液；将所述第二溶液进行水热反应,得到水热反应产物；将所述水热反应产物进行过滤洗涤,后进行干燥,得到低铁勃姆石；本申请通过水热法制备勃姆石,首先通过砂磨过程和酸液除去一部分除铁,再通过水热法除去部分铁,从而得到低铁勃姆石。(The invention particularly relates to low-iron boehmite as well as a preparation method and application thereof, belonging to the technical field of boehmite materials, wherein the method comprises the following steps: dissolving raw material aluminum hydroxide in a first solvent, mixing with acid liquor and grinding to obtain a first solution; carrying out water bath on the first solution, and then filtering and washing to obtain a filter cake; dissolving the filter cake in a second solvent, and then adding an additive to obtain a second solution; carrying out hydrothermal reaction on the second solution to obtain a hydrothermal reaction product; filtering and washing the hydrothermal reaction product, and then drying to obtain low-iron boehmite; according to the application, boehmite is prepared by a hydrothermal method, a part of iron is removed through a sand grinding process and an acid solution, and a part of iron is removed through a hydrothermal method, so that low-iron boehmite is obtained.)

1. A method for preparing low-iron boehmite, the method comprising:

dissolving raw material aluminum hydroxide in a first solvent, mixing with acid liquor and grinding to obtain a first solution;

carrying out water bath on the first solution, and then filtering and washing to obtain a filter cake;

dissolving the filter cake in a second solvent, and then adding an additive to obtain a second solution;

carrying out hydrothermal reaction on the second solution to obtain a hydrothermal reaction product;

and filtering and washing the hydrothermal reaction product, and then drying to obtain the low-iron boehmite.

2. The method of preparing low-iron boehmite according to claim 1, characterized in that the acid liquor comprises at least one of dilute sulfuric acid, acetic acid, oxalic acid, citric acid and salicylic acid.

3. The method of preparing low-iron boehmite according to claim 1, wherein the median particle size D50 of the aluminum hydroxide in the first solution is 0.8 μm to 1.2 μm.

4. The process for preparing low-iron boehmite according to claim 1, characterized in that the solid content of the first solution is 300g/L to 400g/L by weight.

5. The preparation method of low-iron boehmite according to claim 1, characterized in that the temperature of the water bath is 60-80 ℃, the time of the water bath is 1-2 h, and the filtration washing is performed by using a polyethersulfone microporous membrane.

6. The method for preparing low-iron boehmite according to claim 1, characterized in that the additive comprises one of sodium dodecyl benzene sulfonate, sodium lignosulfonate, lignosulfonic acid, sodium 4-n-octylbenzenesulfonate or sodium sulfamate and derivatives thereof, and the mass fraction of the additive is 0.05% -0.1%.

7. The process for preparing low-iron boehmite according to claim 1, characterized in that the solid content of the second solution is 150g/L to 220g/L by weight.

8. The method for preparing low-iron boehmite according to claim 1, characterized in that the temperature of the hydrothermal reaction is 180-220 ℃ and the time of the hydrothermal reaction is 1-4 h.

9. Low-iron boehmite produced according to a process for producing low-iron boehmite according to any one of claims 1 to 8.

10. Use of low-iron boehmite, characterized in that it comprises using said boehmite as a separator material for lithium batteries; the boehmite according to claim 9.

Technical Field

The invention belongs to the technical field of boehmite materials, and particularly relates to low-iron boehmite as well as a preparation method and application thereof.

Background

Boehmite (also called boehmite, gamma-AlOOH) is widely used in the fields of special ceramics, catalyst carriers, battery separators, inorganic flame retardants and the like due to unique pore channel structure and surface properties. Iron is one of the main impurities in the boehmite, and the low-iron boehmite can replace the matrix of an expensive electronic coating due to the characteristics of the low-iron boehmite, so that the cost is reduced, and the additional value of the product is improved. In the application of new materials in China, the content of iron impurities in boehmite is an important index, the requirement of low-iron boehmite for coating a battery diaphragm and a positive electrode on the content of iron is lower than 50ppm, and the service performance and the service life of a product are seriously influenced due to overhigh content of the iron impurities, so that the exploration of an effective method for deeply removing iron is an urgent technical problem to be solved.

At present, no relevant reports and industrialization cases for removing iron impurities are found in the synthesis of boehmite by a hydrothermal method. Therefore, according to the characteristics of boehmite hydrothermal method production, the low-iron boehmite prepared by a simple, convenient, rapid and energy-saving method and having high product purity and controllable product granularity is developed, and has important significance for improving market competitiveness of ultrafine powder in China.

Disclosure of Invention

The application aims to provide low-iron boehmite, and a preparation method and application thereof, so as to fill the blank of removing iron impurities in boehmite synthesized by a current hydrothermal method.

The embodiment of the invention provides a preparation method of low-iron boehmite, which comprises the following steps:

dissolving raw material aluminum hydroxide in a first solvent, mixing with acid liquor and grinding to obtain a first solution;

carrying out water bath on the first solution, and then filtering and washing to obtain a filter cake;

dissolving the filter cake in a second solvent, and then adding an additive to obtain a second solution;

carrying out hydrothermal reaction on the second solution to obtain a hydrothermal reaction product;

and filtering and washing the hydrothermal reaction product, and then drying to obtain the low-iron boehmite.

Optionally, the acid solution comprises at least one of dilute sulfuric acid, acetic acid, oxalic acid, citric acid and salicylic acid.

Optionally, the median particle size D50 of the aluminum hydroxide in the first solution is 0.8 μm to 1.2 μm.

Optionally, the first solution has a solids content of 300g/L to 400g/L by weight.

Optionally, the temperature of the water bath is 60-80 ℃, the time of the water bath is 1-2 h, and a polyethersulfone microporous filter membrane is adopted for filtration in the filtration and washing.

Optionally, the additive comprises one of sodium dodecyl benzene sulfonate, sodium lignin benzene sulfonate, lignosulfonic acid, 4-n-octylbenzene sulfonate or sodium sulfamate and derivatives thereof, and the mass fraction of the additive is 0.05% -0.1%.

Optionally, the solids content of the second solution is 150g/L to 220g/L by weight.

Optionally, the temperature of the hydrothermal reaction is 180-220 ℃, and the time of the hydrothermal reaction is 1-4 h.

Based on the same inventive concept, the embodiment of the invention also provides low-iron boehmite prepared by adopting the preparation method of the low-iron boehmite.

Optionally, the boehmite has a mass purity of 99.9% and a specific surface area of 5m²/g-8m²(ii)/g, the boehmite has a median particle diameter D50 of 0.8 μm to 1.0 μm.

Based on the same inventive concept, the embodiment of the invention also provides an application of low-iron boehmite, wherein the application comprises the step of taking the boehmite as a diaphragm material of a lithium battery; the boehmite is boehmite as described above.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

according to the preparation method of the low-iron boehmite provided by the embodiment of the invention, the industrial aluminum hydroxide and the acid solution are mixed and ground to obtain the first solution, and the positive effect of adding the acid is that the acid can complex Fe²⁺、Fe³⁺Thereby achieving the purpose of iron removal; filtering the first solution slurry to obtain a filter cake, re-dissolving the filter cake with deionized water and adjustingThe solid content of the aluminum hydroxide is saved, an additive is added to obtain a second solution, the second solution is subjected to hydrothermal reaction, the additive has the positive effect that sulfonate and iron ions in the additive can preferentially form a complex compound to fix iron along with release of the iron ions from crystal lattices of the aluminum hydroxide in the hydrothermal process, the complex compound formed by the iron is dissolved in water, and the iron is separated out through filtration, and meanwhile, the sulfonate and the iron ions in the additive cannot be re-adsorbed to the surface of boehmite in the phase inversion process; and filtering and drying the reaction product after hydrothermal treatment to obtain the low-iron boehmite. According to the application, boehmite is prepared by a hydrothermal method, a part of iron is removed through a sand grinding process and an acid solution, and a part of iron is removed through a hydrothermal method, so that low-iron boehmite is obtained.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a scanning electron micrograph of one-dimensional low-iron boehmite provided in example 1 of the present invention.

Fig. 2 is a scanning electron micrograph of one-dimensional low-iron boehmite provided in example 2 of the present invention.

Figure 3 is an XRD picture of one-dimensional low-iron boehmite provided in examples 1 and 2 of the present invention.

Figure 4 is a graph of particle size of boehmite providing very low iron in accordance with example 1 of the invention.

FIG. 5 is a block diagram of a process provided by an embodiment of the invention;

fig. 6 is a flow chart of a method provided by an embodiment of the invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to an exemplary embodiment of the present invention, there is provided a method for preparing low-iron boehmite, the method comprising:

s1, dissolving a raw material aluminum hydroxide in a first solvent, mixing with an acid liquor, and grinding to obtain a first solution;

with the above design, the positive effect of adding acid is that the acid can complex Fe²⁺、Fe³⁺Thereby achieving the purpose of iron removal.

As an alternative embodiment, the acid solution comprises at least one of dilute sulfuric acid, acetic acid, oxalic acid, citric acid, and salicylic acid.

As an alternative embodiment, the median particle size D50 of the aluminum hydroxide in the first solution is between 0.8 μm and 1.2. mu.m.

The median particle size D50 of controlling aluminium hydroxide in first solution is 0.8 mu m-1.2 mu m, both can let the iron impurity of being wrapped up by aluminium hydroxide fully expose, can not produce great energy consumption again, and the too big adverse effect of this particle size value results in the iron impurity of being wrapped up by aluminium hydroxide can't fully expose on the granule surface, and the sand mill sanding is difficult for the too little adverse effect, and the energy consumption increases.

As an alternative embodiment, the first solution has a solids content of from 300g/L to 400g/L by weight.

The solid content of the first solution is controlled to be 300g/L-400g/L so as to ensure that the grinding efficiency of the sand mill is the highest, the adverse effect of overlarge content is that the sand mill is easy to block in the sand grinding and refining process, and the adverse effect of undersize is that the grinding efficiency of the sand mill is low, and the grinding time to the ideal granularity is long.

S2, carrying out water bath on the first solution, and then filtering and washing to obtain a filter cake;

as an alternative embodiment, the temperature of the water bath is 60-80 ℃, the time of the water bath is 1-2 h, and the filtration washing is carried out by adopting a polyethersulfone microporous filter membrane.

The temperature of the water bath is controlled to be 60-80 ℃, the time of the water bath is 1-2 h, so that the acid liquid can fully react with the iron impurities, the energy consumption is increased due to overlarge adverse effect, and the incomplete reaction is caused due to undersize adverse effect.

The positive effect of using the polyethersulfone microporous filter membrane for filtration is that solid-liquid separation is performed, iron is filtered out along with the solution, and in other embodiments, those skilled in the art can also use a centrifuge for separation and other separation operations.

S3, dissolving the filter cake in a second solvent, and adding an additive to obtain a second solution;

as an optional embodiment, the additive comprises one of sodium dodecyl benzene sulfonate, sodium lignin benzene sulfonate, lignosulfonic acid, sodium 4-n-octylbenzene sulfonate or sodium sulfamate and derivatives thereof, and the mass fraction of the additive is 0.05% -0.1%.

By adopting the design, the positive effect of adding the additive is that as iron ions are released from crystal lattices of aluminum hydroxide in the hydrothermal process, sulfonate groups and the iron ions in the additive can preferentially form a complex to fix iron, and meanwhile, the iron ions cannot be re-adsorbed to the boehmite surface in the phase inversion process, and the iron forming complex is dissolved in water.

The mass fraction of the additive is controlled to be 0.05-0.1% so as to control the content of the additive and reduce the cost, the excessive adverse effect is that the cost is increased, and the excessive adverse effect is that the complexing capability is reduced and the iron removal is incomplete.

As an alternative embodiment, the solids content of the second solution is 150g/L to 220g/L by weight.

The solid content of the second solution is controlled to be 150g/L-220g/L, the solid content is too large due to the adverse effect of too large content, more materials are easy to agglomerate and are not beneficial to the reaction, and the reaction amount is small due to the adverse effect of too small content, so that the economic principle is not met.

S4, carrying out a hydrothermal reaction on the second solution to obtain a hydrothermal reaction product;

as an alternative embodiment, the temperature of the hydrothermal reaction is 180-220 ℃, and the time of the hydrothermal reaction is 1-4 h.

And S5, filtering and washing the hydrothermal reaction product, and then drying to obtain the low-iron boehmite.

According to another exemplary embodiment of the present invention, there is provided a low-iron boehmite prepared by the method for preparing a low-iron boehmite as provided above.

According to another exemplary embodiment of the present invention, there is provided a use of low-iron boehmite, comprising using the boehmite as a separator material for a lithium battery; the boehmite is boehmite as provided above.

The present application of low-iron boehmite and its preparation and use will be described in detail with reference to examples, comparative examples and experimental data.

Example 1

A method of preparing low-iron boehmite, the method comprising:

(1) mixing 120g of aluminum hydroxide with 300ml of oxalic acid solution (0.5 wt%), and sanding into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 80 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water and sodium dodecyl benzene sulfonate to prepare a solution with the solid content of 200 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 4 hours at 200 ℃.

(5) Cooling the reactant to below 80 ℃, separating the material, and drying to obtain the low-iron boehmite.

Example 2

A method of preparing low-iron boehmite, the method comprising:

(1) 108g of aluminum hydroxide was mixed with 300ml of an acetic acid solution (0.5 wt%), and then sanded into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 60 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water and sodium dodecyl benzene sulfonate to prepare a solution with solid content of 180 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 2 hours at 200 ℃.

(5) Cooling the reactant to below 80 ℃, separating the material, and drying to obtain the low-iron boehmite.

Example 3

A method of preparing low-iron boehmite, the method comprising:

(1) mixing 120g of aluminum hydroxide with 300ml of oxalic acid solution (0.8 wt%), and sanding into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) for 2h at the temperature of 60 ℃;

(3) filtering the slurry after sanding into a filter cake, and adding water and sulfamic acid to prepare a solution with the solid content of 200 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 2 hours at 210 ℃.

(5) Cooling the reactant to below 80 ℃, separating the material, and drying to obtain the low-iron boehmite.

Example 4

A method of preparing low-iron boehmite, the method comprising:

(1) mixing 120g of aluminum hydroxide with 300ml of oxalic acid solution (1.0 wt%), and sanding into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) for 2h at the temperature of 80 ℃;

(3) filtering the slurry after sanding into a filter cake, and adding water and sodium sulfamate to prepare a solution with the solid content of 200 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 2 hours at 200 ℃.

(5) Cooling the reactant to below 80 ℃, separating the material, and drying to obtain the low-iron boehmite.

Example 5

A method of preparing low-iron boehmite, the method comprising:

(1) 108g of aluminum hydroxide was mixed with 300ml of oxalic acid solution (0.5 wt%), and then sanded into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 60 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water and sodium sulfamate to prepare a solution with the solid content of 1800 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 4 hours at 220 ℃.

(5) Cooling the reactant to below 80 ℃, separating the material, and drying to obtain the low-iron boehmite.

Comparative example 1

A method of preparing boehmite, the method comprising:

(1) mixing 108g of aluminum hydroxide with 300ml of water, and sanding the mixture into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 60 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water to prepare a solution with solid content of 180 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 4 hours at 220 ℃.

(5) Cooling the reactant to below 80 ℃, separating out materials, and drying to obtain the boehmite.

Comparative example 2

A method of preparing boehmite, the method comprising:

(1) 108g of aluminum hydroxide was mixed with 300ml of oxalic acid solution (0.5 wt%), and then sanded into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 80 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water to prepare a solution with solid content of 180 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 2 hours at 200 ℃.

(5) Cooling the reactant to below 80 ℃, separating out materials, and drying to obtain the boehmite.

Comparative example 3

A method of preparing boehmite, the method comprising:

(1) grinding 108g of aluminum hydroxide and 300ml of water into aluminum hydroxide slurry by a sand mill;

(2) carrying out water bath on the aluminum hydroxide slurry obtained in the step (1) at 60 ℃ for 1 h;

(3) filtering the slurry after sanding into a filter cake, and adding water and sodium sulfamate to prepare a solution with solid content of 180 g/L;

(4) and (4) transferring the mixture obtained in the step (3) to a stainless steel hydrothermal reaction kettle to perform hydrothermal reaction for 2 hours at 220 ℃.

(5) Cooling the reactant to below 80 ℃, separating out materials, and drying to obtain the boehmite.

Examples of the experiments

The intermediate products in the preparation process of example 1 are detected to obtain the key impurity content index of the low-iron boehmite: as shown in the following table:

	D50μm	SiO2 ppm	Fe2O3 ppm	Na2O ppm
					raw materials	11.14	284	105	1706
After sanding	1.124	306	106	1680
					After water bath	1.176	223	65	330
After hydrothermal treatment	0.867-0.954	198-242	49-52	321-340

From the above table, the content of iron element in boehmite prepared by the method provided in this example is less than or equal to 50 ppm.

Boehmite prepared in examples 1 to 5 and comparative examples 1 to N was examined and the results are shown in the following table:

	specific surface area m2/g	Purity%	Iron content
				Example 1	5.49	99.93	50
Example 2	5.13	99.91	49
				Example 3	6.19	99.90	49
Example 4	7.46	99.93	49
				Example 5	6.86	99.93	50
Comparative example 1	8.67	99.91	130
				Comparative example 2	7.14	99.90	87
Comparative example 3	7.31	99.90	99

As can be seen from the above table, the boehmite prepared by the method provided by the present example has the advantages of high purity, low iron content, and small specific surface area. As can be seen from comparison of comparative examples 1 to 3 with example 5, when no acid solution was added during sanding and water bath, no sulfonic acid was added during hydrothermal treatment, and the parameters were outside the ranges provided in this example, the iron content increased and the specific surface area increased.

Detailed description of the drawings 1-4:

fig. 1 is a scanning electron micrograph of the one-dimensional flaky boehmite according to example 1 of the present invention, and it can be seen from fig. 1 that the boehmite has a rhombic flaky structure, a uniform morphology, and no agglomeration.

Fig. 2 is a scanning electron micrograph of the one-dimensional flaky boehmite according to example 2 of the present invention, and it can be seen from fig. 2 that the boehmite has a rhombic flaky structure and a uniform morphology.

FIG. 3 is an XRD picture of one-dimensional flaky boehmite according to examples 1 and 2 of the present invention, and it can be seen from FIG. 3 that the boehmite has a high purity of 99.91%

Fig. 4 is a graph showing the particle size of the one-dimensional flaky boehmite according to example 1 of the present invention, and it can be seen from fig. 4 that the boehmite particle size D50 is 0.810 um.

One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:

(1) according to the method provided by the embodiment of the invention, the industrial aluminum hydroxide and the acid liquor are mixed and ground to obtain the first solution, and the positive effect of adding the acid is that the acid can complex Fe²⁺、Fe³⁺Thereby achieving the purpose of iron removal; filtering the slurry of the first solution to obtain a filter cake, redissolving the filter cake by using deionized water, adjusting the solid content of the aluminum hydroxide, adding an additive to obtain a second solution, and carrying out hydrothermal reaction, wherein the additive has the positive effect that sulfonate and iron ions in the additive can preferentially form a complex along with release of the iron ions from crystal lattices of the aluminum hydroxide in the hydrothermal process, so that the iron is fixed and cannot be re-adsorbed to the surface of boehmite in the phase inversion process, the iron forms the complex to be dissolved in water, and the iron is separated out by filtering; filtering and drying the reaction product after hydrothermal treatment to obtain low-iron boehmite;

(2) according to the method provided by the embodiment of the invention, boehmite is prepared by a hydrothermal method, wherein a part of iron is removed through a sand grinding process and an acid solution, and a part of iron is removed through a hydrothermal method, so that low-iron boehmite is obtained;

(3) the method provided by the embodiment of the invention has the advantages of short time consumption, simplicity, convenience, low temperature and the like;

(4) the boehmite provided by the embodiment of the invention has the advantages of iron content less than or equal to 50ppm, high purity, good crystal form, complete appearance, low sodium content and the like;

(5) the low-iron boehmite provided by the embodiment of the invention can be used as a lithium battery diaphragm material, and the service life of the lithium battery diaphragm can be obviously prolonged.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.