阅读说明：本技术 一种免洗凝胶及其制备方法 (Washing-free gel and preparation method thereof ) 是由 罗屹东 余镇城 王国忠 李玉柱 于 2021-08-18 设计创作，主要内容包括：本发明提供了一种免洗凝胶,包括双癸基二甲基氯化铵、十二烷基二甲基苄基氯化铵、甘油、防腐剂、纳米纤维素、角鲨烷、栀子花香精、去离子水的成分；本发明制备的免洗凝胶具有优异的抗菌性、保湿性、生物降解性以及稳定性,通过季铵化纳米纤维素的三维网络结构,能有效负载抗菌成分,进而赋予免洗凝胶更高的抗菌时效；本发明利用阳离子化的季铵化纳米纤维素的正电荷与阳离子小分子抗菌之间产生静电斥力作用,通过高压均质形成内部具有三维网络结构的凝胶,一方面利用其中的化学键装载抗菌成分,另一方面通过凝胶将抗菌成分均匀分布,使得抗菌成分通过凝胶以均匀的速率向外扩散。(The invention provides a wash-free gel which comprises the components of didecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, glycerol, a preservative, nano cellulose, squalane, gardenia essence and deionized water; the no-clean gel prepared by the invention has excellent antibacterial property, moisture retention property, biodegradability and stability, and can effectively load antibacterial components through the three-dimensional network structure of the quaternized nanocellulose, so that the no-clean gel is endowed with higher antibacterial aging; according to the invention, electrostatic repulsion action is generated between positive charges of cationized quaternized nano-cellulose and cationic micromolecule antibacterial, gel with a three-dimensional network structure inside is formed through high-pressure homogenization, and on one hand, antibacterial components are loaded by using chemical bonds in the gel, and on the other hand, the antibacterial components are uniformly distributed through the gel, so that the antibacterial components are diffused outwards at a uniform rate through the gel.)

1. The washing-free gel is characterized by comprising the following components in percentage by mass:

0.15 to 0.35 percent of didecyl dimethyl ammonium chloride, 0.15 to 0.35 percent of dodecyl dimethyl benzyl ammonium chloride, 0.1 to 0.3 percent of glycerol, 0.02 to 0.1 percent of preservative, 0.65 to 2 percent of nano-cellulose, 0.1 to 0.5 percent of squalane, 0.001 to 0.003 percent of gardenia essence and the balance of deionized water.

2. The leave-on gel of claim 1, wherein the nanocellulose is quaternized nanocellulose.

3. The leave-on gel according to claim 2, characterized in that the preparation method of the quaternized nanocellulose comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use;

dissolving cellulose in the reaction system, and stirring for 3-5 min under the condition of 1500-2500 r/min to obtain a first mixture;

dropwise adding a cationic etherifying agent into the first mixture, and reacting for 8-16 h at room temperature to obtain a second mixture;

and washing the second mixture with ethanol for 3-5 times, then washing with deionized water for 3-5 times, and filtering to obtain the quaternized cellulose.

4. The leave-on gel according to claim 3, wherein the cellulose is one or a mixture of pulp fiber and cotton cellulose.

5. The leave-on gel of claim 3, wherein said cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyl-trimethylammonium chloride, 3-chloro-2-hydroxypropyldodecyltrimethylammonium chloride.

6. A process for preparing a leave-on gel according to any of claims 2 to 5 comprising the steps of:

adding the quaternized nano-cellulose into deionized water to obtain a quaternized nano-cellulose solution, and then carrying out primary homogenization treatment on the quaternized nano-cellulose solution to obtain a quaternized nano-cellulose gel;

dissolving didecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, glycerol and a preservative in deionized water at room temperature, and uniformly stirring to obtain a mixed solution;

and adding the mixed solution into the quaternized nano cellulose gel, after the second homogenization treatment is finished, dropwise adding squalane and gardenia essence, and continuing the third homogenization treatment to obtain the no-wash gel.

7. The method for preparing a leave-on gel according to claim 6, wherein the quaternized nanofibers account for 0.65% -2% of the mass percentage of the quaternized nanocellulose solution.

8. The method for preparing a leave-on gel according to claim 6, wherein the conditions of the first homogenization treatment are as follows: homogenizing for 1-3 times by a high-pressure homogenizer under the condition of 200-500 bar.

9. The method for preparing a leave-on gel according to claim 6, wherein the conditions of the second homogenization treatment are as follows: and (3) homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 0 bar.

10. The method for preparing a leave-on gel according to claim 6, wherein the conditions of the third homogenization treatment are as follows: and homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 300-500 bar.

Technical Field

The invention relates to the field of daily chemical products, in particular to a wash-free gel and a preparation method thereof.

Background

Because of frequent contact with the external environment, hands almost become the most direct bridge for pathogen microorganisms to invade human bodies, and products for hand disinfection are various on the market, and alcohols, iodides, hydrogen peroxide, quaternary ammonium salts and compound products of the alcohols, the iodides, the hydrogen peroxide and the quaternary ammonium salts are the most common. The main sterilization component of the currently marketed wash-free antibacterial gel is ethanol, the carrier is carbopol resin generally, the ethanol content in the product is 60-80%, the ethanol is a Volatile Organic Compound (VOC) and pollutes the surrounding environment in the use process, the carbopol resin is a cross-linked acrylic polymer, the carbopol resin is a petrochemical-source high polymer material which cannot be biodegraded, the biocompatibility of the carbopol resin is poor, and the environment is easily polluted after being discarded. In addition, the no-clean gel products in the prior art have the problems of high skin irritation, rough skin caused by dryness, and unsatisfactory antibacterial effect and stability.

In conclusion, there are still some problems to be solved in the field of preparing leave-on gels.

Disclosure of Invention

Based on the above, in order to solve the problems of large skin irritation, and unsatisfactory antibacterial effect and stability of the no-wash gel in the prior art, the invention provides the no-wash gel, and the specific technical scheme is as follows:

the washing-free gel comprises the following components in percentage by mass:

0.15 to 0.35 percent of didecyl dimethyl ammonium chloride, 0.15 to 0.35 percent of dodecyl dimethyl benzyl ammonium chloride, 0.1 to 0.3 percent of glycerol, 0.02 to 0.1 percent of preservative, 0.65 to 2 percent of nano-cellulose, 0.1 to 0.5 percent of squalane, 0.001 to 0.003 percent of gardenia essence and the balance of deionized water.

Preferably, the nanocellulose is quaternized nanocellulose.

Preferably, the preparation method of the quaternized nanocellulose comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use;

dissolving cellulose in the reaction system, and stirring for 3-5 min under the condition of 1500-2500 r/min to obtain a first mixture;

dropwise adding a cationic etherifying agent into the first mixture, and reacting for 8-16 h at room temperature to obtain a second mixture;

and washing the second mixture with ethanol for 3-5 times, then washing with deionized water for 3-5 times, and filtering to obtain the quaternized cellulose.

Preferably, the cellulose is one or a mixture of pulp fiber and cotton cellulose.

Preferably, the cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethyl ammonium chloride, 3-chlorine-2-hydroxypropyl-trimethyl ammonium chloride and 3-chlorine-2-hydroxypropyl dodecyl trimethyl ammonium chloride.

In addition, the invention also provides a preparation method of the no-clean gel, which comprises the following steps:

adding the quaternized nano-cellulose into deionized water to obtain a quaternized nano-cellulose solution, and then carrying out primary homogenization treatment on the quaternized nano-cellulose solution to obtain a quaternized nano-cellulose gel;

dissolving didecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, glycerol and a preservative in deionized water at room temperature, and uniformly stirring to obtain a mixed solution;

and adding the mixed solution into the quaternized nano cellulose gel, after the second homogenization treatment is finished, dropwise adding squalane and gardenia essence, and continuing the third homogenization treatment to obtain the no-wash gel.

Preferably, the quaternized nanocellulose accounts for 0.65-2% of the quaternized nanocellulose solution by mass.

Preferably, the conditions of the first homogenization treatment are as follows: homogenizing for 1-3 times by a high-pressure homogenizer under the condition of 200-500 bar.

Preferably, the conditions of the second homogenization treatment are as follows: and (3) homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 0 bar.

Preferably, the conditions of the third homogenization treatment are as follows: and homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 300-500 bar.

The no-clean gel prepared by the scheme has excellent antibacterial property, moisture retention property, biodegradability and stability, and the antibacterial components can be effectively loaded through the three-dimensional network structure of the quaternized nanocellulose, so that the antibacterial components are gradually released when the no-clean gel is used, the no-clean gel is endowed with higher antibacterial aging, no VOC substance is generated, and the environmental protection performance is higher; according to the preparation method, thickening agents and stabilizing agents are not required to be added excessively, electrostatic repulsion effect is generated between positive charges of cationized quaternized nano-cellulose and cationic micromolecular antibacterial components, the gel with the three-dimensional network structure inside is formed through high-pressure homogenization, on one hand, the antibacterial components are loaded through chemical bonds, on the other hand, the antibacterial components are uniformly distributed through the gel, and the antibacterial components are enabled to diffuse outwards at a uniform rate through the gel.

Drawings

FIG. 1 is a schematic representation of a quaternized nanopaper cellulose hydrogel prepared in example 1;

FIG. 2 is a schematic representation of the leave-on gel prepared in example 1 in a human skin efficacy test;

FIG. 3 is a schematic diagram of the bacteriostatic ring experiment of E.coli 8099 of the leave-on gel prepared in example 3;

FIG. 4 is a schematic diagram of the zone of inhibition experiment for Staphylococcus aureus ATCC6538 of the leave-on gel prepared in example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to embodiments thereof. It should be understood that the detailed description and specific examples, while indicating the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

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. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The washing-free gel in one embodiment of the invention comprises the following components in percentage by mass:

0.15 to 0.35 percent of didecyl dimethyl ammonium chloride, 0.15 to 0.35 percent of dodecyl dimethyl benzyl ammonium chloride, 0.1 to 0.3 percent of glycerol, 0.02 to 0.1 percent of preservative, 0.65 to 2 percent of nano-cellulose, 0.1 to 0.5 percent of squalane, 0.001 to 0.003 percent of gardenia essence and the balance of deionized water.

In one embodiment thereof, the nanocellulose is quaternized nanocellulose.

In one embodiment, the preservative is one or a mixture of 2-methyl-4-isothiazolin-3-one and 2-methyl-5-chloro-4-isothiazolin-3-one in any proportion.

In one embodiment, the method for preparing the quaternized nanocellulose comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use;

dissolving cellulose in the reaction system, and stirring for 3-5 min under the condition of 1500-2500 r/min to obtain a first mixture;

dropwise adding a cationic etherifying agent into the first mixture, and reacting for 8-16 h at room temperature to obtain a second mixture;

and washing the second mixture with ethanol for 3-5 times, then washing with deionized water for 3-5 times, and filtering to obtain the quaternized cellulose.

In one embodiment, the cellulose is one or a mixture of pulp fiber and cotton cellulose.

In one embodiment, the cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyl-trimethylammonium chloride, and 3-chloro-2-hydroxypropyldodecyltrimethylammonium chloride.

In one embodiment, the mass ratio of the cellulose to the cationic etherifying agent is 1: 10-15.

In addition, the invention also provides a preparation method of the no-clean gel, which comprises the following steps:

adding the quaternized nano-cellulose into deionized water to obtain a quaternized nano-cellulose solution, and then carrying out primary homogenization treatment on the quaternized nano-cellulose solution to obtain a quaternized nano-cellulose gel;

dissolving a mixture of didecyl dimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, glycerol, 2-methyl-4-isothiazoline-3-ketone and 2-methyl-5-chlorine-4-isothiazoline-3-ketone in a small amount of deionized water at room temperature, and uniformly stirring to obtain a mixed solution;

and adding the mixed solution into the quaternized nano cellulose gel, after the second homogenization treatment is finished, dropwise adding squalane and gardenia essence, and continuing the third homogenization treatment to obtain the no-wash gel.

In one embodiment, the quaternized nanocellulose accounts for 0.65% -2% of the mass of the quaternized nanocellulose solution.

In one embodiment, the conditions of the first homogenization treatment are as follows: homogenizing for 1-3 times by a high-pressure homogenizer under the condition of 200-500 bar.

In one embodiment, the conditions of the second homogenization treatment are as follows: and (3) homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 0 bar.

In one embodiment, the conditions of the third homogenization treatment are as follows: and homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 300-500 bar.

The no-clean gel prepared by the scheme has excellent antibacterial property, moisture retention property, biodegradability and stability, and the antibacterial components can be effectively loaded through the three-dimensional network structure of the quaternized nanocellulose, so that the antibacterial components are gradually released when the no-clean gel is used, the no-clean gel is endowed with higher antibacterial aging, no VOC substance is generated, and the no-clean gel is high in environmental protection performance; according to the preparation method, thickening agents and stabilizing agents are not required to be added excessively, electrostatic repulsion effect is generated between positive charges of cationized quaternized nano-cellulose and cationic micromolecular antibacterial components, the gel with the three-dimensional network structure inside is formed through high-pressure homogenization, on one hand, the antibacterial components are loaded through chemical bonds, on the other hand, the antibacterial components are uniformly distributed through the gel, and the antibacterial components are enabled to diffuse outwards at a uniform rate through the gel.

Embodiments of the present invention will be described in detail below with reference to specific examples.

Example 1:

a preparation method of a disposable gel comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use; dissolving 10g of paper pulp cellulose in the reaction system, and stirring for 5min under the condition of 1500r/min to obtain a first mixture; adding 117.6g of 2, 3-epoxypropyltrimethylammonium chloride into the first mixture dropwise, and reacting for 8 hours at room temperature to obtain a second mixture; washing the second mixture with 20% by mass of ethanol for 5 times, then washing with deionized water for 3 times, and filtering to obtain quaternized nano pulp cellulose;

adding 0.65g of the quaternized nano pulp cellulose into deionized water to prepare a quaternized nano pulp cellulose solution, and homogenizing the quaternized nano pulp cellulose solution for 3 times under the condition of 200bar by using a high-pressure homogenizer to obtain quaternized nano pulp cellulose gel, wherein the quaternized nano pulp cellulose accounts for 0.65% of the mass of the quaternized nano pulp cellulose solution;

dissolving 0.15g of didecyl dimethyl ammonium chloride, 0.35g of dodecyl dimethyl benzyl ammonium chloride, 0.1g of glycerol and 0.1g of a mixture of 2-methyl-4-isothiazolin-3-one and 2-methyl-5-chloro-4-isothiazolin-3-one in a mass ratio of 1:1 in a small amount of deionized water at room temperature, and uniformly stirring to obtain a mixed solution;

and adding the mixed solution into the quaternized nano paper pulp cellulose gel, homogenizing for 1-3 times by adopting a high-pressure homogenizer under the condition of 0bar, dropwise adding 0.5g of squalane and 0.001g of gardenia essence, and continuously homogenizing for 1-3 times under the condition of 300-500 bar to obtain the washing-free gel.

Example 2:

a preparation method of a disposable gel comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use; dissolving 10g of cotton cellulose in the reaction system, and stirring for 5min at the speed of 2500r/min to obtain a first mixture; adding 117.6g of 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride dropwise into the first mixture, and reacting at room temperature for 16h to obtain a second mixture; washing the second mixture with 20% ethanol by mass for 5 times, then washing with deionized water for 3 times, and filtering to obtain quaternized nano cotton cellulose;

adding 1.2g of the quaternized nano cotton cellulose into deionized water to prepare a quaternized nano cotton cellulose solution, homogenizing the quaternized nano cotton cellulose solution for 3 times under the condition of 300bar by using a high-pressure homogenizer to obtain quaternized nano cotton cellulose gel, wherein the quaternized nano cotton cellulose accounts for 1.2% of the mass of the quaternized nano cotton cellulose solution;

dissolving 0.25g of didecyl dimethyl ammonium chloride, 0.25g of dodecyl dimethyl benzyl ammonium chloride and 0.2g of glycerol into a small amount of deionized water at room temperature, and uniformly stirring to obtain a mixed solution, wherein the mass ratio of 0.06g of a mixture of 2-methyl-4-isothiazolin-3-one and 2-methyl-5-chloro-4-isothiazolin-3-one is 2: 1;

and adding the mixed solution into the quaternized nano cotton cellulose gel, homogenizing for 3 times under the condition of 0bar by using a high-pressure homogenizer, dropwise adding 0.3g of squalane and 0.002g of gardenia essence, and continuously homogenizing for 3 times under the condition of 400bar to obtain the washing-free gel.

Example 3:

a preparation method of a disposable gel comprises the following steps:

preparing a reaction system by NaOH, urea and water according to the mass percentage of 7:12:81, and storing the reaction system at the temperature of-18 ℃ for later use; dissolving 10g of paper pulp cellulose in the reaction system, and stirring for 5min under the condition of 2000r/min to obtain a first mixture; adding 117.6g of 3-chloro-2-hydroxypropyl dodecyl trimethyl ammonium chloride dropwise into the first mixture, and reacting for 10 hours at room temperature to obtain a second mixture; washing the second mixture with 20% ethanol by mass for 5 times, then washing with deionized water for 3 times, and filtering to obtain quaternized nano pulp cellulose;

adding 2.0g of the quaternized nano pulp cellulose into deionized water, preparing to obtain a quaternized nano pulp cellulose solution, homogenizing the quaternized nano pulp cellulose solution for 3 times under the condition of 500bar by using a high-pressure homogenizer to obtain quaternized nano pulp cellulose gel, wherein the quaternized nano pulp cellulose accounts for 2.0% of the mass of the quaternized nano pulp cellulose solution;

dissolving 0.35g of didecyl dimethyl ammonium chloride, 0.15g of dodecyl dimethyl benzyl ammonium chloride, 0.3g of glycerol and 0.1g of a mixture of 2-methyl-4-isothiazolin-3-one and 2-methyl-5-chloro-4-isothiazolin-3-one in a mass ratio of 1:1 in a small amount of deionized water at room temperature, and uniformly stirring to obtain a mixed solution;

and adding the mixed solution into the quaternized nano paper pulp cellulose gel, homogenizing for 3 times under the condition of 0bar by using a high-pressure homogenizer, dropwise adding 0.1g of squalane and 0.003g of gardenia essence, and continuously homogenizing for 3 times under the condition of 500bar to obtain the washing-free gel.

Comparative example 1:

the difference from example 3 is that the added pulp cellulose is not treated with a cationic etherifying agent, and the other is the same as example 3.

Comparative example 2:

the preparation method of the antibacterial liquid comprises the following steps:

dissolving 0.35g of didecyl dimethyl ammonium chloride, 0.15g of dodecyl dimethyl benzyl ammonium chloride, 0.3g of glycerol and 0.1g of a mixture of 2-methyl-4-isothiazoline-3-ketone and 2-methyl-5-chloro-4-isothiazoline-3-ketone in a mass ratio of 1:1 in 100mL of deionized water at room temperature, uniformly stirring to obtain a mixed solution, continuously dropwise adding 0.1g of squalane and 0.003g of gardenia essence, and homogenizing for 3 times by using a high-pressure homogenizer at 500bar to obtain the antibacterial solution.

The results of the tests on the leave-on gels prepared in examples 1 to 3, the leave-on gel prepared in comparative example 1, and the antibacterial liquid prepared in comparative example 2 were verified, and the results of the tests on inhibition and killing of microorganisms in the examples were performed by referring to the bacteriostatic ring test and the carrier quantitative killing test method in the "disinfection technical specification" (2002 edition) of the ministry of health, and are shown in tables 1 and 2.

Table 1:

table 2:

as can be seen from the data analysis of tables 1 and 2, the no-clean gel prepared by the invention has excellent antibacterial and sterilization effects, and the antibacterial aging is longer; compared with the example 3, the quaternary ammonium nano pulp cellulose prepared by the method is applied to the no-wash gel, so that the antibacterial component can be effectively loaded, the uniform distribution and diffusion of the antibacterial component are promoted, and the antibacterial aging of the no-wash gel is prolonged.

In addition, the mildness, moisture retention and stability of the leave-on gels prepared in examples 1 to 3, the leave-on gel prepared in comparative example 1 and the antibacterial solution prepared in comparative example 2 were also tested according to the present invention, and the results are shown in Table 3.

The mildness and the moisture retention are completed through a human skin efficacy test, 50 volunteers are randomly selected, the test time is 5 days, and the detection equipment is a VISA skin detector. The stability test is as follows: the no-clean gels prepared in examples 1-3, the no-clean gel prepared in comparative example 1 and the antibacterial solution prepared in comparative example 2 were stored in a 37 ℃ incubator at RH > 75% for 90 days, and then observed for the presence of bleeding, coarse particles, caking, and change in odor, which was a rough subjective determination.

Table 3:

as can be seen from the preliminary detection analysis in Table 3, the wash-free gel prepared by the method is good in mildness, no adverse reaction occurs to skin after trial use of 50 volunteers, and the wash-free gel prepared by the method is considered to show excellent moisture retention. In addition, through stability tests, the addition of the quaternized nano pulp fibers in the invention contributes to the improvement of the stability of the leave-on gel.

Fig. 1 is a schematic representation of a substance of the quaternized nano pulp cellulose hydrogel prepared in example 1, and it can be seen from fig. 1 that the formed state of the quaternized nano pulp cellulose in the gel state prepared by the method of the present invention is stable; fig. 2 shows that the no-clean gel prepared in the invention is in the form of gel before rubbing, can be evenly spread and absorbed by skin, and has certain moisturizing effect, so that the skin is more delicate; FIG. 3 is a schematic diagram of the bacteriostatic ring experiment of E.coli 8099 of the leave-on gel prepared in example 3; fig. 4 is a schematic diagram of a bacteriostatic ring experiment of staphylococcus aureus ATCC6538 of the leave-on gel prepared in example 3, and it can be seen from fig. 3 and fig. 4 that the leave-on gel prepared in the present invention has an excellent bacteriostatic effect. Other experimental bacteria and experiments are the same as the operation of the bacteriostatic experiment on escherichia coli 8099 and staphylococcus aureus ATCC6538 in example 3, and are specifically described in tables 1 and 2, and thus, detailed description thereof is omitted.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features. The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.