1. The high-flame-retardant low-smoke halogen-free insulation material capable of being rapidly crosslinked by ultraviolet light is characterized by comprising the following components in parts by mass:

ethylene-vinyl acetate copolymer resin: 10-20 parts;

metallocene polyethylene: 5-10 parts;

linear low density polyethylene: 5-10 parts;

a compatilizer: 5-10 parts;

flame-retardant filler: 55-75 parts;

flame retardant auxiliary agent: 2.5-7 parts;

photoinitiator (2): 2-5 parts;

1-3 parts of an auxiliary crosslinking agent;

antioxidant: 0.5-1.5 parts;

lubricant: 0.5 to 1.5 portions.

2. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, characterized in that the optimal ratio is as follows according to mass percent:

ethylene-vinyl acetate copolymer resin: 15 parts of (1);

metallocene polyethylene: 7.5 parts;

linear low density polyethylene: 7.5 parts;

a compatilizer: 7.5 parts;

flame-retardant filler: 65 parts of (1);

flame retardant auxiliary agent: 4.5 parts;

photoinitiator (2): 3.5 parts;

auxiliary crosslinking agent: 2 parts of (1);

antioxidant: 1 part;

lubricant: 1 part.

3. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulation material according to claim 1, wherein the ethylene-vinyl acetate copolymer resin has a melt index of 10; the metallocene polyethylene has a melt index of 3.5 and the linear low density polyethylene has a melt index of 20.

4. The ultraviolet fast crosslinking high flame retardant low smoke zero halogen insulation material according to claim 1, wherein the compatilizer is maleic anhydride grafted ethylene octene copolymer.

5. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, wherein the flame-retardant filler is magnesium hydroxide and aluminum hydroxide, and the parts of the magnesium hydroxide and the aluminum hydroxide are 15-25 parts and 40-50 parts respectively.

6. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, wherein the flame-retardant auxiliary agent is ultra-high molecular weight polysiloxane and organic montmorillonite, and the mass part ratio of the ultra-high molecular weight polysiloxane to the organic montmorillonite is 1: (2-4).

7. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, wherein the photoinitiator is a mixture of several of alpha-hydroxyalkyl acetone type initiators, hydrogen abstraction type free radical photoinitiator derivatives and thioxanthone type photoinitiators in proportion, specifically benzophenone: 2-isopropyl thioxanthone: 4-hydroxybenzophenone laurate in a ratio of 1: 1:0.5 mixing.

8. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, wherein the auxiliary crosslinking agent is a mixture of triallyl isocyanurate and trimethylolpropane trimethacrylate in a ratio of 1: 1.

9. The ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material as claimed in claim 1, wherein the antioxidant is an antioxidant resistant to ultraviolet radiation, and is one or a mixture of dioctadecyl alcohol pentaerythritol diphosphite and bis (2,2,6, 6-tetramethyl-3-piperidinylamino) -isophthalamide; the lubricant is silicone master batch.

10. A preparation method of an ultraviolet light fast crosslinking high-flame-retardant low-smoke halogen-free insulating material is characterized by being used for producing the ultraviolet light fast crosslinking high-flame-retardant low-smoke halogen-free insulating material; the method comprises the following steps:

s1: mixing; weighing the components according to the proportion, firstly directly putting the ethylene-vinyl acetate resin, the metallocene polyethylene, the linear low-density polyethylene, the compatilizer and the magnesium hydroxide into an internal mixer for internal mixing; then, uniformly mixing the lubricant, the initiator, the cross-linking agent and the antioxidant with 5kg of aluminum hydroxide, and adding the mixture into an internal mixer;

s2, banburying: banburying for 15-20 minutes by an internal mixer, opening a pressurizing cover to clean once floating dust when the temperature is 10 minutes midway, and discharging when the temperature reaches 140 ℃ and 150 ℃;

s3: extruding and granulating; and feeding the internally mixed materials into a double-screw extruder through forced feeding, fully mixing and extruding, and then extruding and granulating through a single-screw extruder to obtain the ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material.

Background

The low-smoke halogen-free flame-retardant polyolefin cable material has better flame retardant property, does not release toxic gas during combustion, but has lower mechanical property due to the addition of a large amount of flame-retardant filler, and the non-crosslinked material is not resistant to temperature and is difficult to meet the requirement of high-temperature use environment. The polyolefin crosslinking methods commonly used at present mainly include peroxide crosslinking, silane crosslinking, radiation crosslinking and ultraviolet crosslinking. The ultraviolet light wavelength range is 300-400 nm, because the energy is strong, the crosslinking reaction of the resin material can be excited, and the ultraviolet light crosslinking technology does not belong to high-energy rays, the irradiated workpiece or product has no radioactivity, and the ultraviolet light crosslinking technology has the advantages of being unique, small in pollution, low in energy consumption, stable in crosslinking and the like, so that the ultraviolet light crosslinking technology is rapidly developed and widely applied. Compared with other existing crosslinking technologies, the method can be used for directly forming coils on line, is high in production efficiency and low in equipment maintenance cost, and therefore has a good development prospect.

When the ultraviolet crosslinking technology is applied to the halogen-free flame-retardant cable material, the crosslinking efficiency of the system can be reduced due to the difference of the absorption wavelengths of ultraviolet light by different colors of the insulated wires and the addition of a large amount of flame-retardant filler due to the flame-retardant requirement. Therefore, the material has the problems of low crosslinking speed, insufficient crosslinking density, difficult improvement of flame retardance and the like at present.

Therefore, those skilled in the art need to develop a uv-crosslinked high-flame-retardant low-smoke halogen-free cable material to solve the technical problem that the crosslinking efficiency, density and high flame-retardant property of the uv-crosslinked low-smoke halogen-free flame-retardant cable material in the field are difficult to coexist for a long time.

The prior art CN102492196A discloses a high-temperature abrasion-resistant polyolefin compound and a preparation method thereof, wherein the high-temperature abrasion-resistant polyolefin compound comprises 35-75 wt% of polyolefin, 5-20 wt% of high-temperature abrasion-resistant agent, 1-5 wt% of coupling agent and 30-10 wt% of mineral filler, wollastonite is disclosed to be added into the high-temperature abrasion-resistant polyolefin compound as the mineral filler, but whether the wollastonite improves the high-temperature aging resistance of the material is not specifically stated. Further, the improvement of the wear resistance of the high-temperature wear-resistant polyolefin composite disclosed above is only aimed at improving the wear resistance loss of the material before and after aging, and is not aimed at improving the mechanical properties of the material used at high temperature for a long time, and the ultraviolet light crosslinking low-smoke halogen-free cable material on the market has poor flame resistance, generally has an oxygen index of 32, and cannot meet the actual high flame-retardant requirement.

Disclosure of Invention

Aiming at the defects in the technology, the invention provides the ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material, the high-melt-index resin base material is added to obtain higher crosslinking density, the photoinitiators and the auxiliary crosslinking agents with different mechanisms are matched with each other, the absorption range of ultraviolet wavelength is expanded, the crosslinking speed is improved, and meanwhile, the flame-retardant filler is matched with the flame-retardant auxiliary agent to generate a crusting effect, so that the mechanical property and the aging property of the insulating material are greatly improved compared with those of the common thermoplastic insulating material, the use temperature of 125 ℃ is reached, the oxygen index is up to more than 36, and the prepared cable can pass a single or bundled combustion experiment.

In order to achieve the purpose, the invention provides an ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material which comprises the following components in parts by mass:

ethylene-vinyl acetate copolymer resin: 10-20 parts;

metallocene polyethylene: 5-10 parts;

linear low density polyethylene: 5-10 parts;

a compatilizer: 5-10 parts;

flame-retardant filler: 55-75 parts;

flame retardant auxiliary agent: 2.5-7 parts;

photoinitiator (2): 2-5 parts;

1-3 parts of an auxiliary crosslinking agent;

antioxidant: 0.5-1.5 parts;

lubricant: 0.5 to 1.5 portions.

Preferably, the optimal proportion is as follows according to the mass percentage:

ethylene-vinyl acetate copolymer resin: 15 parts of (1);

metallocene polyethylene: 7.5 parts;

linear low density polyethylene: 7.5 parts;

a compatilizer: 7.5 parts;

flame-retardant filler: 65 parts of (1);

flame retardant auxiliary agent: 4.5 parts;

photoinitiator (2): 3.5 parts;

auxiliary crosslinking agent: 2 parts of (1);

antioxidant: 1 part;

lubricant: 1 part.

Preferably, the ethylene-vinyl acetate copolymer resin has a melt index of 10; the metallocene polyethylene has a melt index of 3.5 and the linear low density polyethylene has a melt index of 20.

Preferably, the compatibilizer is a maleic anhydride grafted ethylene octene copolymer.

Preferably, the flame-retardant filler is magnesium hydroxide and aluminum hydroxide, and the parts of the magnesium hydroxide and the aluminum hydroxide are 15-25 parts and 40-50 parts respectively.

Preferably, the flame retardant auxiliary agent is ultrahigh molecular weight polysiloxane and organic montmorillonite, and the mass part ratio of the ultrahigh molecular weight polysiloxane to the organic montmorillonite is 1: (2-4).

Preferably, the photoinitiator is a mixture of several of alpha-hydroxyalkyl acetone initiators, derivatives of hydrogen abstraction type free radical photoinitiators and thioxanthone photoinitiators in proportion, specifically benzophenone: 2-isopropyl thioxanthone: 4-hydroxybenzophenone laurate in a ratio of 1: 1:0.5 mixing.

Preferably, the auxiliary crosslinking agent is mixture of triallyl isocyanurate and trimethylolpropane trimethacrylate according to the proportion of 1: 1.

Preferably, the antioxidant is an ultraviolet radiation resistant antioxidant, and is one or a mixture of two of dioctadecyl alcohol pentaerythritol diphosphite and bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide; the lubricant is silicone master batch.

The invention also discloses a preparation method of the ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material, which is used for producing the ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material; the method comprises the following steps:

s1: mixing; weighing the components according to the proportion, firstly directly putting the ethylene-vinyl acetate resin, the metallocene polyethylene, the linear low-density polyethylene, the compatilizer and the magnesium hydroxide into an internal mixer for internal mixing; then, uniformly mixing the lubricant, the initiator, the cross-linking agent and the antioxidant with 5kg of aluminum hydroxide, and adding the mixture into an internal mixer;

s2, banburying: banburying for 15-20 minutes by an internal mixer, opening a pressurizing cover to clean once floating dust when the temperature is 10 minutes midway, and discharging when the temperature reaches 140 ℃ and 150 ℃;

s3: extruding and granulating; and feeding the internally mixed materials into a double-screw extruder through forced feeding, fully mixing and extruding, and then extruding and granulating through a single-screw extruder to obtain the ultraviolet fast crosslinking high-flame-retardant low-smoke halogen-free insulating material.

The invention has the beneficial effects that: compared with the prior art, the invention does not adopt any wollastonite, breaks through the conventional technology that wollastonite is utilized to improve the rigidity and the hardness of the material in the traditional thinking, the invention mainly adopts the addition of high-index resin base stock to obtain higher crosslinking density, and simultaneously uses flame-retardant filler to be matched with flame-retardant auxiliary agent to generate the crusting effect, the obtained ultraviolet light fast crosslinking high-flame-retardant low-smoke halogen-free insulating material has higher wear resistance, and simultaneously the mechanical property and the aging property are greatly improved compared with the common thermoplastic insulating material, the oxygen index of the material reaches more than 36, the elongation at break can reach 170 percent, the tensile strength can reach 12.1MPa, and the thermal deformation rate is only 11 percent; the cable can pass an aging experiment at a temperature of 158 ℃/168h, has excellent tensile property and thermal aging property, and can be widely applied to the preparation of wires and cables with a temperature resistance level of 125 ℃ through a single or bundled combustion experiment.

The specific implementation mode is as follows:

the present invention will be further described with reference to specific embodiments, but the present invention is not limited to the examples in any way. The starting reagents used in the examples of the present invention are, unless otherwise specified, those conventionally available and commercially available.

Firstly, in the application, ethylene-vinyl acetate copolymer resin, metallocene polyethylene and linear low-density polyethylene are used as resin base materials, and the ethylene-vinyl acetate copolymer resin adopts 7670s, 625 or NUC3190, so that the melt index is about 10; compared with the traditional PE, the metallocene polyethylene has obvious different performance, and is obviously superior to the traditional polyethylene in the aspects of toughness, transparency, hot adhesiveness, heat sealing temperature, low odor and the like; in the present application, metallocene polyethylene and alpha olefin can be effectively combined, and in the specific using process, metallocene polyethylene 3518 with the melt index of 3.5 can be adopted; in the application, the adopted linear low-density polyethylene has a linear molecular structure, no long branched chain winding exists, and more short branched chains exist, so that the obtained product has higher mechanical property and better warping resistance, and the linear low-density polyethylene with the melt index of 20 is adopted in the specific use process; as is well known, the melt index is the amount of thermoplastic material extruded in a certain time under specified conditions, namely the mass of a melt passing through a standard die capillary every 10min, expressed by M FR, and the unit is g/10min, the higher the melt index of the same kind of resin under the same test conditions is, the lower the molecular weight is, in the application, the linear low-density polyethylene with the melt index of 20 is adopted, so that more end group and branch chain crosslinking points can be provided, the crosslinking density of the material can be greatly improved, and meanwhile, because the resin of the melt index 20 has good fluidity in a molten state, the three resin base materials can be fully mixed in the granulation process, and the three resin base materials can be mixed more uniformly according to the principle of similar compatibility.

The compatilizer adopted in the application is a maleic anhydride grafted elastomer, more specifically, a maleic anhydride grafted ethylene-octene copolymer is adopted, a grafted polymer simultaneously has a polar group and a non-polar group, wherein the polar group can be better combined with hydroxyl in the flame-retardant filler, and simultaneously the non-polar group can be combined with base resin, so that a polymer base material and the inorganic non-metallic flame-retardant filler can be strongly combined together instead of simple mixing, and the overall performance of the finally obtained product is better.

The combination of the flame-retardant filler and the flame-retardant auxiliary agent can generate a crusting effect during combustion to generate a compact carbon layer to form a heat-insulating and oxygen-blocking barrier layer, the contact between the interior of the insulating material and oxygen prevents flame from further spreading, and the flame retardant property of a final product is improved, so that the cable can pass a single combustion test in national standards after being manufactured.

The photoinitiator and the auxiliary crosslinking agent are used as substances which are necessary to be added for ultraviolet light rapid crosslinking, the photoinitiator is one or a mixture of an alpha-hydroxyalkylacetone initiator, a derivative of a hydrogen abstraction type free radical photoinitiator and a thioxanthone photoinitiator, and the photoinitiator adopts benzophenone, 2-isopropyl thioxanthone and 4-hydroxybenzophenone laurate according to the ratio of 2: the alpha-hydroxyalkyl acetone initiator is obtained by mixing the components in a ratio of 2:1, has stable performance and good yellowing resistance, is a benzophenone or heterocyclic aromatic ketone compound as hydrogen abstraction type free radical photoinitiators, has good intermiscibility with oligomers as the hydrogen abstraction type free radical photoinitiator and the thioxanthone photoinitiator, and has stable property as the hydrogen abstraction type free radical photoinitiator and the thioxanthone photoinitiator interact with the alpha-hydroxyalkyl acetone initiator to improve the initiation efficiency; when the polyolefin resin is subjected to crosslinking reaction, a trifunctional auxiliary crosslinking agent must be added to improve the crosslinking reaction speed, and the triallyl isocyanurate (TMPTMA) and the triallyl isocyanurate (TAIC) are matched, so that the crosslinking speed can be greatly improved, the wire outlet speed of the cable during extrusion can be improved, and the production efficiency of the cable is improved.

The invention is illustrated below using specific examples:

the first embodiment is as follows:

firstly, weighing 10 parts of ethylene-vinyl acetate copolymer resin; 10 parts of metallocene polyethylene; linear low density polyethylene: 5 parts of a mixture; a compatilizer: 5 parts of a mixture; 40 parts of aluminum hydroxide and 15 parts of magnesium hydroxide; ultra-high molecular weight polysiloxane: 0.5 part; 2 parts of organic montmorillonite; benzophenone and 2-isopropyl thioxanthone and 4. hydroxybenzophenone laurate using a 1: mixing at a ratio of 1:0.5, and weighing 2 parts; mixing trimethylolpropane trimethacrylate and triallyl isocyanurate in a ratio of 1:1, weighing 1 part, weighing 0.5 part of bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide and dioctadecyl alcohol pentaerythritol diphosphite in a ratio of 1:1 as an antioxidant, and weighing 0.5 part of silicone master batch in a ratio of 1: 1;

then putting resin matrix (ethylene-vinyl acetate copolymer resin; metallocene polyethylene and linear low density polyethylene) and maleic anhydride grafted ethylene-octene copolymer and magnesium hydroxide into an internal mixer, then mixing and adding lubricant, initiator, cross-linking agent and antioxidant into aluminum hydroxide, adding into the internal mixer after mixing uniformly, then internally mixing for 15 minutes, opening a pressurizing cover for cleaning once floating dust after about 8 minutes, stopping working when the material temperature reaches 140 ℃, taking out the material, adding into a double-screw extruder for fully mixing, then transferring into a single-screw extruder for continuous mixing, and finally extruding and granulating through the single-screw extruder.

Example two:

firstly, weighing 13 parts of ethylene-vinyl acetate copolymer resin; 8 parts of metallocene polyethylene; 8 parts of linear low-density polyethylene; a compatilizer: 8 parts of a mixture; 45 parts of aluminum hydroxide and 20 parts of magnesium hydroxide; ultra-high molecular weight polysiloxane: 1 part; 3 parts of organic montmorillonite; benzophenone and 2-isopropyl thioxanthone and 4. hydroxybenzophenone laurate using a 1: weighing 3 parts in a ratio of 1: 0.5; 1.5 parts of trimethylolpropane trimethacrylate and triallyl isocyanurate are weighed according to the proportion of 1:1, 0.8 part of bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide and dioctadecyl alcohol pentaerythritol diphosphite are weighed according to the proportion of 1:1 as an antioxidant, and 0.8 part of silicone master batch is weighed;

then putting resin matrix (ethylene-vinyl acetate copolymer resin; metallocene polyethylene and linear low density polyethylene) and maleic anhydride grafted ethylene-octene copolymer and magnesium hydroxide into an internal mixer, then mixing and adding lubricant, initiator, cross-linking agent and antioxidant into aluminum hydroxide, adding into the internal mixer after mixing uniformly, then internally mixing for 17 minutes, opening a pressure cover about 10 minutes to clean floating dust once, stopping working when the material temperature reaches 145 ℃, taking out the material, adding into a double-screw extruder for full mixing, then transferring into a single-screw extruder for continuous mixing, and finally extruding and granulating through the single-screw extruder.

Example three:

firstly, weighing 15 parts of ethylene-vinyl acetate copolymer resin; 7.5 parts of metallocene polyethylene; 7.5 parts of linear low-density polyethylene; a compatilizer: 7.5 parts; 45 parts of aluminum hydroxide and 20 parts of magnesium hydroxide; ultra-high molecular weight polysiloxane: 1.5 parts; 2 parts of organic montmorillonite; benzophenone and 2-isopropyl thioxanthone and 4. hydroxybenzophenone laurate using a 1: weighing 3.5 parts according to the proportion of 1: 0.5; weighing 2 parts of trimethylolpropane trimethacrylate and triallyl isocyanurate in a ratio of 1:1, weighing 1 part of bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide and dioctadecyl alcohol pentaerythritol diphosphite in a ratio of 1:1 as an antioxidant, and weighing 1 part of silicone master batch;

then putting resin matrix (ethylene-vinyl acetate copolymer resin; metallocene polyethylene and linear low density polyethylene) and maleic anhydride grafted ethylene-octene copolymer, magnesium hydroxide into an internal mixer, then mixing and adding lubricant, initiator, cross-linking agent and antioxidant into aluminum hydroxide, adding into the internal mixer after mixing uniformly, then internally mixing for 20 minutes, opening a pressure cover about 10 minutes to clean floating dust once, stopping working when the material temperature reaches 150 ℃, taking out the material, adding into a double-screw extruder for fully mixing, then transferring into a single-screw extruder for continuous mixing, and finally extruding and granulating through the single-screw extruder.

Example four:

firstly, weighing 18 parts of ethylene-vinyl acetate copolymer resin; 8 parts of metallocene polyethylene; 8 parts of linear low-density polyethylene; a compatilizer: 8 parts of a mixture; 45 parts of aluminum hydroxide and 25 parts of magnesium hydroxide; ultra-high molecular weight polysiloxane: 2 parts of (1); 3 parts of organic montmorillonite; benzophenone and 2-isopropyl thioxanthone and 4. hydroxybenzophenone laurate using a 1: weighing 4 parts in a ratio of 1: 0.5; 2.5 parts of trimethylolpropane trimethacrylate and triallyl isocyanurate are weighed according to the proportion of 1:1, 1.2 parts of bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide and dioctadecyl alcohol pentaerythritol diphosphite are weighed according to the proportion of 1:1 as an antioxidant, and 1.2 parts of silicone master batch is weighed;

then putting resin matrix (ethylene-vinyl acetate copolymer resin; metallocene polyethylene and linear low density polyethylene) and maleic anhydride grafted ethylene-octene copolymer and magnesium hydroxide into an internal mixer, then mixing and adding lubricant, initiator, cross-linking agent and antioxidant into aluminum hydroxide, adding into the internal mixer after mixing uniformly, then carrying out internal mixing for 25 minutes, opening a pressurizing cover about 12 minutes to clean floating dust once, stopping working when the material temperature reaches 155 ℃, taking out the material, adding into a double-screw extruder for full mixing, then transferring into a single-screw extruder for continuous mixing, and finally carrying out extrusion granulation through the single-screw extruder.

Example five:

firstly, weighing 20 parts of ethylene-vinyl acetate copolymer resin; 10 parts of metallocene polyethylene; 10 parts of linear low-density polyethylene; a compatilizer: 5 parts of a mixture; 50 parts of aluminum hydroxide and 25 parts of magnesium hydroxide; ultra-high molecular weight polysiloxane: 2 parts of (1); 5 parts of organic montmorillonite; benzophenone and 2-isopropyl thioxanthone and 4. hydroxybenzophenone laurate using a 1: weighing 5 parts in a ratio of 1: 0.5; weighing 3 parts of trimethylolpropane trimethacrylate and triallyl isocyanurate in a ratio of 1:1, weighing 1.5 parts of bis (2,2,6, 6-tetramethyl-3-piperidylamino) -isophthalamide and dioctadecyl alcohol pentaerythritol diphosphite in a ratio of 1:1 as an antioxidant, and weighing 1.5 parts of silicone master batch;

then putting resin matrix (ethylene-vinyl acetate copolymer resin; metallocene polyethylene and linear low density polyethylene) and maleic anhydride grafted ethylene-octene copolymer and magnesium hydroxide into an internal mixer, then mixing and adding lubricant, initiator, cross-linking agent and antioxidant into aluminum hydroxide, adding into the internal mixer after mixing uniformly, then carrying out internal mixing for 25 minutes, opening a pressurizing cover about 12 minutes to clean floating dust once, stopping working when the material temperature reaches 155 ℃, taking out the material, adding into a double-screw extruder for full mixing, then transferring into a single-screw extruder for continuous mixing, and finally carrying out extrusion granulation through the single-screw extruder.

The products obtained in the above five examples were tested, and the test results are as follows:

the first embodiment is as follows:

example two

EXAMPLE III

Example four:

example five:

it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.