1. A processing method of a spandex recycled filler superfine fiber synthetic leather is characterized by comprising the step of impregnating a base fabric by adopting a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: recovering fillers from spandex; the spandex recovery filler is prepared by adding spandex recovery waste silk into a high-boiling-point solvent DMF (dimethyl formamide), and is prepared from the following raw materials in parts by weight (20-30): (70-80) and stirring the resulting liquid in a reaction vessel.

2. The method for processing the polyurethane fiber recycled filler superfine fiber synthetic leather according to claim 1, wherein the impregnation slurry for wet impregnation comprises: the high-support polyurethane and spandex recycled filler comprises the following components in parts by weight (95-105): (40-50) to prepare an impregnation slurry.

3. The method for processing the polyurethane fiber recycled filler superfine fiber synthetic leather according to claim 2, wherein the impregnation slurry for wet impregnation comprises: high-support polyurethane, a spandex recovered filler, a solvent DMF and a softening agent, wherein the components in parts by weight (95-105): (40-50): (30-55): (1-2) adding the resulting mixture to prepare an impregnation slurry.

4. The method for processing the polyurethane fiber recycled filler superfine fiber synthetic leather according to claim 1, which is characterized by comprising the following steps:

step one, mixing PA slices and PE slices in proportion and preparing a polyamide blended sea-island fiber through a spinning process;

secondly, manufacturing superfine fiber non-woven fabrics from the prepared chinlon blending sea-island fibers by a needle punching process;

step three, shaping the superfine fiber non-woven fabric according to the thickness and the gram weight to finish the production and the manufacture of the base fabric;

impregnating the base fabric by using a wet impregnation process;

fifthly, splitting the impregnated base fabric to obtain split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

5. The method for processing the superfine fiber synthetic leather with the recycled spandex filler as claimed in claim 4, wherein in the step one, the PA slices and the PE slices are mixed according to the parts by weight (60-70) to (40-30) and then are spun to obtain the nylon blended sea-island fiber.

6. The method for processing the spandex recovered filler superfine fiber synthetic leather as claimed in claim 4, wherein in the second step, the needle density is 2100-2500C/cm during the needling process²。

7. The processing method of the superfine fiber synthetic leather with the recycled spandex filler according to claim 4, wherein in the third step, the superfine fiber non-woven fabric is heated in a gradient manner by a 7-stage oven, the temperature is respectively set to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, the speed of the vehicle is controlled to be 6.5-8.5 m/min, and the heat-set superfine fiber non-woven fabric is cooled by a cooling roller at 10-20 ℃, so that the thickness and the gram weight of the superfine fiber non-woven fabric are set, and the production and the manufacture of the base fabric are finished.

8. The method for processing the superfine fiber synthetic leather with the spandex recycled filler according to claim 7, wherein in the third step, the density of the superfine fiber non-woven fabric after shaping is in a range of 0.275-0.310.

9. The method for processing the spandex recycled filler superfine fiber synthetic leather according to claim 4, wherein in the fourth step, the wet impregnation process is performed at a high sugar degree and a low temperature, and the temperature is 25-30 ℃ and the sugar degree is 35-40 ℃.

10. The method for processing the superfine fiber synthetic leather with the recycled spandex filler according to claim 4, wherein in the fifth step, the impregnated base fabric is immersed in hot toluene at a temperature of 80-85 ℃ for 60-90min to be subjected to fiber opening treatment, and then is washed with water at a temperature of 95-105 ℃ for 20-30min to obtain the base fabric subjected to fiber opening.

Background

Spandex has excellent elasticity and physical and mechanical properties and is widely applied to the fields of textile clothing and the like. In recent years, China has developed the spandex industry rapidly, but a large amount of waste silk is generated in the production and use processes of spandex. At present, enterprises generally adopt a landfill incineration mode to treat waste silk, and the enterprises are urgent to solve the problems that the environmental protection, energy conservation and sustainable development are advocated, the spandex waste silk is reasonably recycled, the damage to the natural environment is reduced, and the enterprises are urgent to solve.

For example, the invention with the publication number of CN101886810A applies for an incinerator for a chemical plant, and particularly discloses a chemical component incinerator. The chemical component incinerator comprises a furnace body, a hearth and a chimney, wherein a channel leading to the chimney is formed in the rear part of the furnace body, and a purification device is arranged in the channel; one end of the channel is fixed with the furnace body, and the other end of the channel is connected with the chimney through a flange; the inner wall of the channel is provided with internal threads, the outer wall of the shell of the purification device is provided with external threads, and the purification device is screwed with the channel. When the invention is used, the incineration gas passes through the purification device to be purified, and the purification absorption solution absorbs the macromolecular gas to be recycled, thereby greatly saving energy and reducing air pollution. Can be widely applied to the incineration of high polymer components such as polypropylene fiber, acrylic fiber, spandex, chinlon, terylene and the like. The incinerator is used for spandex incineration, so that material waste is caused, the surrounding environment is affected and polluted, and energy conservation and environmental protection are insufficient.

Disclosure of Invention

In order to solve the problem that in the prior art, a large amount of waste silk is generated in the production and use processes of spandex, and enterprises generally adopt a landfill incineration mode to treat the waste silk. The invention provides a processing method of spandex recovery filler superfine fiber synthetic leather, which adds spandex recovery waste silk into a high-boiling-point solvent to prepare liquid and reapplies the liquid on the superfine fiber synthetic leather, thus developing a new way for using the spandex recovery waste silk, and being more environment-friendly and energy-saving. The specific technical scheme is as follows:

a processing method of a spandex recycled filler superfine fiber synthetic leather comprises the step of impregnating a base fabric by a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: recovering fillers from spandex; the spandex recovery filler is prepared by adding spandex recovery waste silk into a high-boiling-point solvent DMF (dimethyl formamide), and is prepared from the following raw materials in parts by weight (20-30): (70-80) and stirring the resulting liquid in a reaction vessel.

The method develops a new way for recycling the waste spandex fibers, can greatly reduce the use of synthetic polyurethane so as to reduce the production cost of enterprises, and adopts ways such as incineration and the like to recycle the waste spandex fibers compared with the prior art, so that the method is more environment-friendly and energy-saving and is more environment-friendly.

Preferably, the impregnation slurry for impregnation by the wet impregnation process comprises: the high-support polyurethane and spandex recycled filler comprises the following components in parts by weight (95-105): (40-50) to prepare an impregnation slurry.

The polyurethane fiber material has the characteristic of high elasticity, but has the characteristic of no generation of foam during the wet solidification process of the traditional superfine fiber synthetic leather production process, so that the high-support polyurethane is added to generate foam, the wall thickness of the foam generated by the high-support polyurethane has toughness, the high-support polyurethane and the polyurethane fiber recycled filler do not generate the characteristic of foam interaction, and the foam generated after the wet impregnation solidification by adopting the impregnation slurry containing the high-support polyurethane and the polyurethane fiber recycled filler is fine, dense and tough, so that the problems of low density, insufficient fineness of fold lines, weak skin feel, high resin consumption and poor comfort of the traditional superfine fiber synthetic leather can be solved.

Preferably, the impregnation slurry for impregnation by the wet impregnation process comprises: high-support polyurethane, a spandex recovered filler, a solvent DMF and a softening agent, wherein the components in parts by weight (95-105): (40-50): (30-55): (1-2) adding the resulting mixture to prepare an impregnation slurry.

Preferably, the method comprises the following steps:

step one, mixing PA slices and PE slices in proportion and preparing a polyamide blended sea-island fiber through a spinning process;

secondly, manufacturing superfine fiber non-woven fabrics from the prepared chinlon blending sea-island fibers by a needle punching process;

step three, shaping the superfine fiber non-woven fabric according to the thickness and the gram weight to finish the production and the manufacture of the base fabric;

impregnating the base fabric by using a wet impregnation process;

fifthly, splitting the impregnated base fabric to obtain split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

Preferably, in the step one, the PA slices and the PE slices are mixed according to the parts by weight (60-70) to (40-30) to prepare the chinlon blending sea-island fiber through a spinning process.

Preferably, in the second step, the needle density in the needling process is 2100-²。

Preferably, in the third step, the superfine fiber non-woven fabric is heated in a 7-level oven in a gradient mode, the temperature is set to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, the vehicle speed is controlled to be 6.5-8.5 m/min, the superfine fiber non-woven fabric after heat setting is cooled by a cooling roller at 10-20 ℃, the thickness and the gram weight of the superfine fiber non-woven fabric are set, and the production and the manufacture of the base fabric are finished.

Preferably, in the third step, the density of the shaped superfine fiber non-woven fabric is in the range of 0.275-0.310.

Preferably, in the fourth step, the wet impregnation process adopts high sugar degree and low temperature for solidification, the temperature is 25-30 ℃, and the sugar degree is 35-40 ℃.

Preferably, in the fifth step, the impregnated base fabric is immersed in hot toluene at the temperature of 80-85 ℃ for 60-90min to carry out fiber opening treatment, and then is washed with water at the temperature of 95-105 ℃ for 20-30min to obtain the base fabric after fiber opening.

Has the advantages that:

the technical scheme of the invention has the following beneficial effects:

(1) the method develops a new way for recycling the waste spandex fibers, can greatly reduce the use of synthetic polyurethane so as to reduce the production cost of enterprises, and adopts ways such as incineration and the like to recycle the waste spandex fibers compared with the prior art, so that the method is more environment-friendly and energy-saving and is more environment-friendly.

(2) The polyurethane fiber material has the characteristic of high elasticity, but has the characteristic of no generation of foam during the wet solidification process of the traditional superfine fiber synthetic leather production process, so that the high-support polyurethane is added to generate foam, the wall thickness of the foam generated by the high-support polyurethane has toughness, the high-support polyurethane and the polyurethane fiber recycled filler do not generate the characteristic of foam interaction, and the foam generated after the wet impregnation solidification by adopting the impregnation slurry containing the high-support polyurethane and the polyurethane fiber recycled filler is fine, dense and tough, so that the problems of low density, insufficient fineness of fold lines, weak skin feel, high resin consumption and poor comfort of the traditional superfine fiber synthetic leather can be solved.

Detailed Description

The described embodiments of the invention are only some, but not all embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of embodiments of the invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

A processing method of a spandex recycled filler superfine fiber synthetic leather comprises the step of impregnating a base fabric by a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: recovering fillers from spandex; the spandex recovery filler is prepared by adding spandex recovery waste silk into a high-boiling-point solvent DMF (dimethyl formamide), and is prepared from the following raw materials in parts by weight (20-30): (70-80) and stirring the resulting liquid in a reaction vessel.

The method develops a new way for recycling the waste spandex fibers, can greatly reduce the use of synthetic polyurethane so as to reduce the production cost of enterprises, and adopts ways such as incineration and the like to recycle the waste spandex fibers compared with the prior art, so that the method is more environment-friendly and energy-saving and is more environment-friendly.

As a preferred embodiment, the spandex recovery filler is prepared by adding the spandex recovery waste silk into a high-boiling-point solvent to react in a reaction vessel under stirring to obtain a liquid, wherein the reaction time is 24-72 hours, and the reaction temperature is 160-220 ℃.

As a preferred embodiment, the spandex recovery filler is a liquid which is obtained by adding the spandex recovery waste silk into a high-boiling-point solvent and stirring and reacting in a reaction vessel, wherein the solid content is 20-30%, and the viscosity is 200-300 cps. The synthetic leather manufactured by adopting the spandex recycled filler with the solid content and the viscosity within the range has better physical property.

As a preferred embodiment, the reaction vessel is a reaction vessel.

As a preferred embodiment, the impregnation slurry for impregnation by the wet impregnation process includes: the high-support polyurethane and spandex recycled filler comprises the following components in parts by weight (95-105): (40-50) to prepare an impregnation slurry.

In a preferred embodiment, the high-support polyurethane myogenic index is not less than 70%.

Specifically, the high-support polyurethane in the invention is high-support polyurethane with a small cell characteristic.

The polyurethane fiber material has the characteristic of high elasticity, but has the characteristic of no generation of foam during the wet solidification process of the traditional superfine fiber synthetic leather production process, so that the high-support polyurethane is added to generate foam, the wall thickness of the foam generated by the high-support polyurethane has toughness, the high-support polyurethane and the polyurethane fiber recycled filler do not generate the characteristic of foam interaction, and the foam generated after the wet impregnation solidification by adopting the impregnation slurry containing the high-support polyurethane and the polyurethane fiber recycled filler is fine, dense and tough, so that the problems of low density, insufficient fineness of fold lines, weak skin feel, high resin consumption and poor comfort of the traditional superfine fiber synthetic leather can be solved.

As a preferred embodiment, the impregnation slurry for impregnation by the wet impregnation process includes: high-support polyurethane, a spandex recovered filler, a solvent DMF and a softening agent, wherein the components in parts by weight (95-105): (40-50): (30-55): (1-2) adding the resulting mixture to prepare an impregnation slurry.

As a preferred embodiment, the impregnation slurry for wet impregnation process further comprises color paste, which is added according to the weight portion (0.5: 1.5).

As a preferred embodiment, the method comprises the following steps:

step one, mixing PA slices and PE slices in proportion and preparing a polyamide blended sea-island fiber through a spinning process;

secondly, manufacturing superfine fiber non-woven fabrics from the prepared chinlon blending sea-island fibers by a needle punching process;

step three, shaping the superfine fiber non-woven fabric according to the thickness and the gram weight to finish the production and the manufacture of the base fabric;

impregnating the base fabric by using a wet impregnation process;

fifthly, splitting the impregnated base fabric to obtain split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

As a preferred embodiment, in the step one, the PA slices and the PE slices are mixed according to the parts by weight (60-70) to (40-30) to prepare the chinlon blending sea-island fiber through a spinning process.

As a preferred embodiment, in the second step, the needle density in the needling process is 2100-²。

In a preferred embodiment, in the third step, the superfine fiber non-woven fabric is heated in a gradient way by a 7-stage oven, the temperature is respectively set to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, the vehicle speed is controlled to be 6.5-8.5 m/min, the superfine fiber non-woven fabric after heat setting is cooled by a cooling roller at 10-20 ℃, the thickness and the gram weight of the superfine fiber non-woven fabric are set, and the production and the manufacture of the base fabric are finished.

In a preferred embodiment, in step three, the density of the shaped microfiber nonwoven fabric is in the range of 0.275 to 0.310.

In a preferred embodiment, in the fourth step, the wet impregnation process is performed by adopting a high sugar degree and low temperature for solidification, wherein the temperature is 25-30 ℃ and the sugar degree is 35-40 ℃.

In a preferred embodiment, in the fifth step, the impregnated base fabric is immersed in hot toluene at a temperature of 80-85 ℃ for 60-90min to carry out fiber opening treatment, and then washed with water at a temperature of 95-105 ℃ for 20-30min to obtain the base fabric after fiber opening.

Example one

A processing method of a spandex recycled filler superfine fiber synthetic leather comprises the step of impregnating a base fabric by a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: high-support polyurethane, spandex recycled filler, DMF (dimethyl formamide) solvent, a softening agent and color paste, wherein the weight parts are 100: 45: 45: 1: 1 adding to prepare impregnation slurry. The spandex recovery filler is yellow viscous liquid which is obtained by adding the spandex recovery waste silk into a high-boiling point solvent DMF according to the weight part of 20:80 and stirring in a reaction kettle for reaction, wherein the solid content of the yellow viscous liquid is 20-30%, the viscosity of the yellow viscous liquid is 200-300cps, the reaction time is 24-72 hours, and the reaction temperature is 160-220 ℃. Wherein the high-support polyurethane is high-support polyurethane with the myogenic index being equal to or larger than 70%.

The processing method of the spandex recycled filler superfine fiber synthetic leather specifically comprises the following steps:

step one, mixing the PA slices and the PE slices according to the weight part of 60:40, and preparing the chinlon blended sea-island fiber by a spinning process;

step two, the prepared chinlon blending sea island fiber is produced into superfine fiber non-woven fabric through a needling process, and the needle density is 2100-²；

Step three, performing thickness and gram weight setting on the superfine fiber non-woven fabric, specifically, performing gradient heating on the superfine fiber non-woven fabric through a 7-level oven, setting the temperature to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, controlling the vehicle speed to be 6.5-8.5 m/min, cooling the superfine fiber non-woven fabric subjected to heat setting through four cooling rollers at 10-20 ℃, realizing the thickness and gram weight setting of the superfine fiber non-woven fabric, and finishing the production and manufacture of the base fabric, wherein the density range of the superfine fiber non-woven fabric subjected to setting is 0.275-0.310;

step four, impregnating the base cloth by using a wet impregnation process, wherein a solidification process in the wet impregnation process adopts high sugar degree and low temperature for solidification, the temperature is 25-30 ℃, and the sugar degree is 35-40 ℃;

step five, performing splitting treatment on the impregnated base fabric to obtain the split base fabric, specifically, soaking the impregnated base fabric in hot toluene at the temperature of 80-85 ℃ for 60-90min to perform splitting treatment, and then washing with water at the temperature of 95-105 ℃ for 20-30min to obtain the split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

Example two

A processing method of a spandex recycled filler superfine fiber synthetic leather comprises the step of impregnating a base fabric by a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: high-support polyurethane, spandex recycled filler, DMF (dimethyl formamide) solvent, a softening agent and color paste, wherein the weight parts are as follows: 40: 35: 1: 0.5 addition of the impregnating slurry. The spandex recovery filler is yellow viscous liquid which is obtained by adding 25:75 parts by weight of spandex recovery waste silk into a high-boiling-point solvent DMF and stirring the mixture in a reaction kettle for reaction, wherein the solid content of the yellow viscous liquid is 20-30%, the viscosity of the yellow viscous liquid is 200-300cps, the reaction time is 24-72 hours, and the reaction temperature is 160-220 ℃. Wherein the high-support polyurethane is high-support polyurethane with the myogenic index being equal to or larger than 70%.

The processing method of the spandex recycled filler superfine fiber synthetic leather specifically comprises the following steps:

step one, mixing the PA slices and the PE slices according to the weight part of 70:30, and preparing the chinlon blended sea-island fiber by a spinning process;

step two, the prepared chinlon blending sea island fiber is produced into superfine fiber non-woven fabric through a needling process, and the needle density is 2100-²；

Step three, performing thickness and gram weight setting on the superfine fiber non-woven fabric, specifically, performing gradient heating on the superfine fiber non-woven fabric through a 7-level oven, setting the temperature to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, controlling the vehicle speed to be 6.5-8.5 m/min, cooling the superfine fiber non-woven fabric subjected to heat setting through four cooling rollers at 10-20 ℃, realizing the thickness and gram weight setting of the superfine fiber non-woven fabric, and finishing the production and manufacture of the base fabric, wherein the density range of the superfine fiber non-woven fabric subjected to setting is 0.275-0.310;

step four, impregnating the base cloth by using a wet impregnation process, wherein a solidification process in the wet impregnation process adopts high sugar degree and low temperature for solidification, the temperature is 25-30 ℃, and the sugar degree is 35-40 ℃;

step five, performing splitting treatment on the impregnated base fabric to obtain the split base fabric, specifically, soaking the impregnated base fabric in hot toluene at the temperature of 80-85 ℃ for 60-90min to perform splitting treatment, and then washing with water at the temperature of 95-105 ℃ for 20-30min to obtain the split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

EXAMPLE III

A processing method of a spandex recycled filler superfine fiber synthetic leather comprises the step of impregnating a base fabric by a wet impregnation process, wherein the impregnation slurry for the wet impregnation process comprises the following steps: high-support polyurethane, spandex recycled filler, DMF (dimethyl formamide) solvent, a softening agent and color paste, wherein the weight portion is 105: 50: 55: 2: 1.5 addition preparation of impregnation slurry. The spandex recovery filler is yellow viscous liquid which is obtained by adding the spandex recovery waste silk into a high-boiling-point solvent DMF according to the weight part of 30:70 and stirring in a reaction kettle for reaction, wherein the solid content of the yellow viscous liquid is 20-30%, the viscosity of the yellow viscous liquid is 200-300cps, the reaction time is 24-72 hours, and the reaction temperature is 160-220 ℃. Wherein the high-support polyurethane is high-support polyurethane with the myogenic index being equal to or larger than 70%.

The processing method of the spandex recycled filler superfine fiber synthetic leather specifically comprises the following steps:

step one, mixing PA slices and PE slices according to the weight part of 65:35, and preparing a polyamide blended sea-island fiber through a spinning process;

step two, the prepared chinlon blending sea island fiber is produced into superfine fiber non-woven fabric through a needling process, and the needle density is 2100-²；

Step three, performing thickness and gram weight setting on the superfine fiber non-woven fabric, specifically, performing gradient heating on the superfine fiber non-woven fabric through a 7-level oven, setting the temperature to be 85 ℃, 100 ℃, 125 ℃, 140 ℃, 145 ℃ and 145 ℃, controlling the vehicle speed to be 6.5-8.5 m/min, cooling the superfine fiber non-woven fabric subjected to heat setting through four cooling rollers at 10-20 ℃, realizing the thickness and gram weight setting of the superfine fiber non-woven fabric, and finishing the production and manufacture of the base fabric, wherein the density range of the superfine fiber non-woven fabric subjected to setting is 0.275-0.310;

step four, impregnating the base cloth by using a wet impregnation process, wherein a solidification process in the wet impregnation process adopts high sugar degree and low temperature for solidification, the temperature is 25-30 ℃, and the sugar degree is 35-40 ℃;

step five, performing splitting treatment on the impregnated base fabric to obtain the split base fabric, specifically, soaking the impregnated base fabric in hot toluene at the temperature of 80-85 ℃ for 60-90min to perform splitting treatment, and then washing with water at the temperature of 95-105 ℃ for 20-30min to obtain the split base fabric;

step six, drying, oiling, shaping and kneading the split base cloth;

step seven, carrying out hot kneading on the base cloth after the skin is kneaded through a hot kneading machine;

and step eight, carrying out a dry veneering process on the base cloth subjected to hot kneading to obtain the spandex recycled filler superfine fiber synthetic leather.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.