阅读说明：本技术 一种玻纤增强苯乙烯马来酸酐共聚物组合物及其制备方法 (Glass fiber reinforced styrene maleic anhydride copolymer composition and preparation method thereof ) 是由 林荣涛 黄险波 叶南飚 王琪 李欣达 郭涛 李文龙 丁正亚 于 2020-12-22 设计创作，主要内容包括：本发明公开一种玻纤增强苯乙烯马来酸酐共聚物的组合物,包括如下重量份的成分：苯乙烯-马来酸酐共聚物20-70份、增韧剂10-50份、短切玻璃纤维20-50份和加工助剂0.1-2份；所述苯乙烯-马来酸酐共聚物为苯乙烯-马来酸酐无规共聚物,所述苯乙烯-马来酸酐共聚物中,残余马来酸酐为0.1～1000ppm。本发明通过控制苯乙烯-马来酸酐共聚物中残余马来酸酐(残单)的含量,能够显著提升玻纤增强苯乙烯-马来酸酐共聚物复合材料的机械性能和耐热性,同时配合苯乙烯-马来酸酐共聚物以及短切玻璃纤维,其提升效果更上一个台阶。同时,本发明还公开了所述玻纤增强苯乙烯马来酸酐共聚物的组合物的制备方法及应用。(The invention discloses a glass fiber reinforced styrene maleic anhydride copolymer composition, which comprises the following components in parts by weight: 20-70 parts of styrene-maleic anhydride copolymer, 10-50 parts of toughening agent, 20-50 parts of chopped glass fiber and 0.1-2 parts of processing aid; the styrene-maleic anhydride copolymer is a styrene-maleic anhydride random copolymer, and the residual maleic anhydride in the styrene-maleic anhydride copolymer is 0.1-1000 ppm. According to the invention, by controlling the content of residual maleic anhydride (residual monomer) in the styrene-maleic anhydride copolymer, the mechanical property and heat resistance of the glass fiber reinforced styrene-maleic anhydride copolymer composite material can be remarkably improved, and the improvement effect is more one step by matching with the styrene-maleic anhydride copolymer and the chopped glass fiber. Meanwhile, the invention also discloses a preparation method and application of the glass fiber reinforced styrene maleic anhydride copolymer composition.)

1. The glass fiber reinforced styrene-maleic anhydride copolymer composition is characterized by comprising the following components in parts by weight: 20-70 parts of styrene-maleic anhydride copolymer, 10-50 parts of toughening agent, 20-50 parts of chopped glass fiber and 0.1-2 parts of processing aid; the styrene-maleic anhydride copolymer is a styrene-maleic anhydride random copolymer; in the styrene-maleic anhydride copolymer, the content of residual maleic anhydride is 0.1-1000 ppm.

2. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 1, wherein the styrene maleic anhydride copolymer has a residual maleic anhydride content of 5 to 200 ppm.

3. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 1, wherein the styrene maleic anhydride copolymer has a maleic anhydride molar content of 5 to 28%.

4. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 1, wherein the chopped glass fiber is an alkali-free chopped glass fiber, and the diameter of the chopped glass fiber is 6 to 20 μm.

5. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 1, wherein the toughening agent is at least one of styrene-butadiene-acrylonitrile copolymer, styrene-butadiene-acrylate copolymer, methacrylate-butadiene-styrene copolymer, methacrylate-acrylate-styrene copolymer, styrene-acrylate-acrylonitrile copolymer, methacrylate-acrylate copolymer.

6. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 5, wherein the toughening agent comprises 10 to 50 weight percent of rubber, and the number average particle diameter D50 of the rubber is 0.01 to 5.0 μm.

7. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 5, wherein when the toughening agent is a styrene-butadiene-acrylonitrile copolymer, the weight percentage of butadiene in the toughening agent is 10-65%, and the number average particle diameter D50 of the butadiene is 0.05-5.0 μm.

8. The glass fiber reinforced styrene maleic anhydride copolymer composition of claim 1, wherein the processing aid is at least one selected from the group consisting of antioxidants, lubricants, heat stabilizers, light stabilizers, and colorants.

9. A method for preparing the glass fiber reinforced styrene-maleic anhydride copolymer composition as defined in any one of claims 1 to 8, wherein the method comprises: uniformly mixing a styrene-maleic anhydride copolymer, a toughening agent and a processing aid, and then putting the mixture into a screw extruder for extrusion granulation at the temperature of 200-300 ℃, wherein the chopped glass fiber is fed into a double-screw extruder from the side to obtain a glass fiber reinforced styrene-maleic anhydride copolymer composition; wherein the screw rotating speed of the double-screw extruder is 100-700 r/min.

10. Use of the glass fiber reinforced styrene maleic anhydride copolymer composition according to any one of claims 1 to 8 in automotive structural parts.

Technical Field

The invention relates to the field of modification of high polymer materials, in particular to a high-performance glass fiber reinforced styrene-maleic anhydride copolymer composition and a preparation method thereof, and is suitable for application to automobile structural parts.

Background

The automobile lightweight technology is one of important directions for the development of the automobile industry, is a common choice of automobile manufacturers all over the world, is an effective, direct and feasible way for realizing energy conservation and emission reduction, is a necessary measure for coping with energy safety in China, and is also a necessary way for the sustainable development of the automobile industry.

The styrene-maleic anhydride material, especially the glass fiber reinforced styrene-maleic anhydride copolymer compound, has more excellent rigidity, heat resistance, dimensional stability, low warpage, high fluidity, aging resistance and other properties than the glass fiber reinforced crystalline material (polypropylene), so that the styrene-maleic anhydride material has potential application in functional structural parts of automobiles. For the capital branded host factory, the core structural functional parts of the capital branded host factory often have extremely strict mechanical performance and appearance requirements, however, the existing styrene-maleic anhydride material technology has a certain gap, which also makes the market share of the materials in the automobile functional parts relatively small.

The invention patent with publication number CN101864117B discloses a glass fiber reinforced styrene resin blend with good appearance and mechanical properties and a preparation method thereof, wherein the blend comprises styrene resin, polymethyl methacrylate, phosphorus-containing compound, styrene-maleic anhydride copolymer and the like. The blend is actually a glass fiber reinforced ABS resin, styrene-maleic anhydride is used as a glass fiber compatilizer, and polymethyl methacrylate is used as a mechanical property improving aid, so that the blend can be suitable for preparing products with high fatigue resistance requirements, such as water treatment valves, connecting pieces, water treatment pumps, water treatment barrel filling openings and the like. Patent publication No. CN103819862B discloses the preparation of a continuous long fiber reinforced styrene-maleic anhydride copolymer for the production of a sunroof frame for an automobile by introducing long glass fibers. The invention patent with publication number CN101555341B discloses a high-strength glass fiber reinforced ABS composite material and a preparation method thereof, wherein the bonding property of an ABS matrix and glass fibers is improved by compounding epoxy resin and styrene-maleic anhydride copolymer as a compatilizer, so that the mechanical property and the heat resistance of the whole composition are improved, and the phenomenon of fiber floating is improved.

Therefore, in the prior art, the mechanical properties of the glass fiber reinforced ABS or the glass fiber reinforced styrene-maleic anhydride copolymer are improved mainly by adding epoxy and PMMA or replacing chopped glass fibers with plant fibers and long glass fibers. The technology still has some defects, such as complicated pretreatment process of the plant fiber and high water absorption rate; the dispersion of long glass fibers in a styrene-maleic anhydride copolymer is a great problem, and the appearance of a glass fiber aggregate 'fishbone' aggravates 'floating fibers'; while increasing compatibility solutions currently reduces material flowability; the forming and processing of the oversized automobile structural parts such as instrument panel frameworks, skylight frames and the like are not small challenges.

Disclosure of Invention

Based on the above, the present invention aims to overcome the defects of the prior art and provide a high-performance glass fiber reinforced styrene maleic anhydride copolymer composition.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the glass fiber reinforced styrene maleic anhydride copolymer composition comprises the following components in parts by weight: 20-70 parts of styrene-maleic anhydride copolymer, 10-50 parts of toughening agent, 20-50 parts of chopped glass fiber and 0.1-2 parts of processing aid; the styrene-maleic anhydride is a styrene-maleic anhydride random copolymer, and the content of residual maleic anhydride in the styrene-maleic anhydride copolymer is 0.1-1000 ppm. The method for testing the content of the residual maleic anhydride comprises the following steps: dissolving a styrene-maleic anhydride copolymer in acetone, dropwise adding methanol into the acetone for precipitation, repeatedly extracting the mixture for three times by using Soxhlet extraction, drying the solution, and determining the content of residual maleic anhydride by measuring the weight change.

Preferably, the content of residual maleic anhydride in the styrene-maleic anhydride copolymer is 5-200 ppm.

Preferably, in the styrene-maleic anhydride copolymer, the molar content of maleic anhydride is 5-28%. The method for testing the content of the maleic anhydride comprises the following steps: dissolving a styrene-maleic anhydride copolymer with deuterated chloroform at room temperature to prepare a solution of 2-3 wt%, and measuring by using NMR.

Preferably, the chopped glass fiber is alkali-free chopped glass fiber, and the diameter of the chopped glass fiber is 6-20 μm.

The more the content of residual maleic anhydride (residual monomer) is, the more than 1000ppm, the residual maleic anhydride monomer (residual monomer) is combined with the polar group on the surface of the glass fiber under the auxiliary action of water (the resin and the glass fiber have certain water absorption rate), so that the polar group on the surface of the glass fiber cannot be combined with the styrene-maleic anhydride copolymer; in other words, residual maleic anhydride (residual monomers) competitively binds to the glass fibers, resulting in a decrease in the binding force of the resin to the glass fibers, thereby reducing the mechanical properties and heat resistance of the overall composite. After the residual maleic anhydride is optimized and controlled, the performance of the whole composite material is greatly improved; meanwhile, the content of the maleic anhydride monomer in the styrene-maleic anhydride copolymer is optimized, and the proper chopped glass fiber is matched, so that the mechanical property and the heat resistance of the composite material reach new heights, and the defect of 'floating fiber' in appearance is the slightest.

Preferably, the toughening agent is at least one of styrene-butadiene-acrylonitrile copolymer (ABS), styrene-butadiene-acrylate copolymer, methacrylate-butadiene-styrene copolymer (MBS), methacrylate-acrylate-styrene copolymer, styrene-acrylate-acrylonitrile copolymer (ASA), methacrylate-acrylate copolymer.

Preferably, in the toughening agent, the weight percentage of the rubber is 10% -50%, and the number average particle diameter D50 of the rubber is 0.01-5.0 μm.

More preferably, when the toughening agent is a styrene-butadiene-acrylonitrile copolymer; in the toughening agent, the weight percentage of butadiene is 10-65%, and the number average particle diameter D50 of butadiene is 0.05-5.0 μm.

Preferably, the processing aid is at least one selected from the group consisting of an antioxidant, a lubricant, a heat stabilizer, a light stabilizer, and a colorant.

Wherein the antioxidant comprises a primary antioxidant or stabilizer (e.g., a hindered phenol and/or a secondary arylamine) and optionally a secondary antioxidant (e.g., a phosphate and/or a thioester). Suitable antioxidants include, secondary antioxidants, organic phosphates such as tris (nonylphenyl) phosphite, tris (2, 4-di-t-butylphenyl) phosphite, bis (2, 4-di-t-butylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite or the like; primary antioxidants, alkylated monophenols or polyphenols; alkylation reaction products of polyhydric phenols with dienes such as tetrakis [ methylene (3, 5-di-tert-butyl-4-hydroxyhydrocinnamate) ] methane and the like; butylated reaction products of p-cresol or dicyclopentadiene; alkylated hydroquinones; hydroxylated thiodiphenyl ether; alkylidene bisphenols; a benzyl compound; esters of beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionic acid with mono-or polyhydric alcohols; esters of beta- (5-tert-butyl-4-hydroxy-3-methylphenyl) -propionic acid with mono-or polyhydric alcohols; esters of thioalkyl or thioaryl compounds such as distearylthiopropionate, dilaurylthiopropionate, ditridecylthiopropionate, octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythritol-tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) ] propionate and the like; amides of beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionic acid and the like; or a combination comprising at least two of the foregoing antioxidants.

Suitable lubricants include zinc stearate, calcium stearate, magnesium stearate, polyethylene wax, EVA wax, oleamide, erucamide, ethylene bis stearamide, silicone lubricants and pentaerythritol stearate.

Suitable heat stabilizers include, for example, organophosphites such as triphenyl phosphite, tris (2, 6-dimethylphenyl) phosphite, tris (mixed mono-and dinonylphenyl) phosphite, and the like; phosphonates such as dimethylbenzene phosphonate or the like; phosphate esters such as trimethyl phosphate and the like; or a combination comprising at least two of the foregoing heat stabilizers.

Suitable light stabilizers include, for example, benzotriazoles, such as 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) -benzotriazole, and 2-hydroxy-4-n-octyloxybenzophenone, and the like, as well as triazine-based ultraviolet light absorbers or combinations comprising at least two of the foregoing light stabilizers.

Such as pigment and/or dye additives. Suitable pigments include, for example, inorganic pigments such as metal oxides and mixed metal oxides such as zinc oxide, titanium dioxide, iron oxide, and the like; sulfides such as zinc sulfide and the like; an aluminate salt; sodium thiosilicates, sulfates, chromates, and the like; carbon black; zinc ferrite; ultramarine blue; pigment brown 24; pigment red 101; pigment yellow 119; organic pigments such as azo, diazo, quinacridone, perylene, napthalenetetracarboxylic acid, flavanthrone, isoindolinone, tetrachloroisoindolinone, anthraquinone, anthanthrone, dioxazine, phthalocyanine, and azo lakes; pigment blue 60, pigment red 122, pigment red 149, pigment red 177, pigment red 179, pigment red 202, pigment white 29, pigment blue 15, pigment green 7, pigment yellow 147 and pigment yellow 150, or a combination comprising at least one of the foregoing pigments. Preferred colorants include carbon black, iron oxide red or titanium dioxide. Suitable dyes may be organic materials, for example coumarin dyes such as coumarin 460 (blue), coumarin 6 (green), nile red lamp; a lanthanide complex; hydrocarbon and substituted hydrocarbon dyes; a polycyclic aromatic hydrocarbon dye; scintillation dyes, such as oxazole or oxadiazole dyes; aryl or heteroaryl substituted poly (C2-8) olefin dyes; a carbocyanine dye; indanthrone dyes; a phthalocyanine dye; an oxazine dye; a quinolone dye; a naphthalene tetracarboxylic acid dye; a porphyrin dye; bis (styryl) biphenyl dyes; an acridine dye; anthraquinone dyes; a cyanine dye; a methine dye; an arylmethane dye; an azo dye; indigoid dyes, thioindigoid dyes; a diazo dye; nitro dyes; quinone imine dyes; an aminoketone dye; a tetrazolium dye; a thiazole dye; a perylene dye; a perylene ketone dye; di-benzoxazolyl thiophene; a triarylmethane dye; a thioxanthene dye; naphthalimide dyes; a lactone dye; fluorophores such as anti-stokes shift dyes that absorb in the near infrared wavelength and emit in the visible wavelength, and the like; luminescent dyes, such as 7-amino-4-methylcoumarin; 3- (2' -benzothiazolyl) -7-diethylaminocoumarin; 2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3, 4-oxadiazole; 2, 5-bis- (4-biphenyl) -oxazole; 2, 2' -dimethyl-p-quaterphenyl; 2,2, -dimethyl-p-terphenyl; 3,5,3 ", 5" -tetra-tert-butyl-p-pentabiphenyl; 2, 5-diphenylfuran; 2, 5-diphenyloxazole; 4, 4' -diphenylstilbene; 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran; 1,1 '-diethyl-2, 2' -carbocyanine iodide; 3,3 ' -diethyl-4, 4 ', 5,5 ' -dibenzothiatricarbocyanin iodide; 7-dimethylamino-1-methyl-4-methoxy-8-azaquinolone-2; 7-dimethylamino-4-methylquinolone-2; 2- (4- (4-dimethylaminophenyl)) -1, 3-butadienyl) -3-ethylbenzothiazole perchlorate; 3-diethylamino-7-diethyliminophenoxazole perchlorate; 2- (1-naphthyl) -5-phenyloxazole; 2, 2' -p-phenylene-bis (5-phenyloxazole); rhodamine 700; rhodamine 800; pyrene; 1, 2-triphenylene; (ii) a rubrene; coronene, or the like, or combinations comprising at least two of the foregoing dyes.

Meanwhile, the invention also discloses a preparation method of the glass fiber reinforced styrene maleic anhydride copolymer composition, which comprises the following steps: uniformly mixing styrene-maleic anhydride, a toughening agent and a processing aid, and then putting the mixture into a screw extruder for extrusion granulation at 200-300 ℃, wherein the chopped glass fiber is fed into a double-screw extruder from the side to obtain a glass fiber reinforced styrene-maleic anhydride copolymer composition; wherein the screw rotating speed of the double-screw extruder is 100-700 r/min.

In addition, the invention also discloses an application of the glass fiber reinforced styrene maleic anhydride copolymer composition in an automobile structural part, such as an instrument panel framework, a front end frame, a skylight frame, a wind protection ring, a rearview mirror bracket and the like, but not limited to the application, wherein the glass fiber reinforced styrene maleic anhydride copolymer composition is particularly suitable for preparing a large skylight frame.

Compared with the prior art, the invention has the beneficial effects that:

in the glass fiber reinforced styrene-maleic anhydride copolymer composition, the mechanical property and the heat resistance of the glass fiber reinforced styrene-maleic anhydride copolymer composite material can be remarkably improved by controlling the content of residual maleic anhydride (residual monomer) in the styrene-maleic anhydride copolymer, and the improvement effect is more one step by matching the styrene-maleic anhydride copolymer and the chopped glass fiber. Therefore, the high-performance glass fiber reinforced styrene-maleic anhydride copolymer composition can meet the high-performance requirement of replacing steel with plastic for automobile structural parts.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to specific examples.

The main representative materials used in the examples and comparative examples are as follows:

styrene-maleic anhydride copolymer:

styrene-maleic anhydride copolymer-1 (SMA-1): residual maleic anhydride content (residual monomer) 5ppm, maleic anhydride content 22%, Polyscope, Netherlands;

styrene-maleic anhydride copolymer-2 (SMA-2): 200ppm of residual maleic anhydride (residual monomer), 18 percent of maleic anhydride and Chinese Wen;

styrene-maleic anhydride copolymer-3 (SMA-3): residual maleic anhydride content (residual monomer) 1000ppm, maleic anhydride content 8%, Chinese Wen;

styrene-maleic anhydride copolymer-4 (SMA-4): residual maleic anhydride content (residual monomer) 2000ppm, maleic anhydride content 25%, Polyscope, Netherlands;

a toughening agent:

the toughening agent is styrene-butadiene-acrylonitrile copolymer;

toughener-1 (ZRJ-1): 15% by weight of rubber, 12% by weight of butadiene and a number average particle size D50 of 3.0 μm, produced by high bridge petrochemical;

toughener-2 (ZRJ-2): 15 percent of rubber, 18 percent of butadiene and 0.3 mu m of number average particle diameter D50, and is produced by a benzene collar;

toughener-3 (ZRJ-3): the rubber accounts for 20 percent by weight, the butadiene accounts for 22 percent by weight, the number average particle diameter D50 is 6.0 mu m, and the rubber is produced by the brocade lake through petrochemical;

toughener-4 (ZRJ-4): 60 percent of rubber, 60 percent of butadiene and 0.3 mu m of number average particle size D50, and is produced by the brocade lake through petrochemical production;

toughener-5 (ZRJ-5): 50 percent of rubber, 70 percent of butadiene and 0.5 mu m of number average particle size D50, and is produced in a bench mode;

chopped glass fiber:

alkali-free chopped glass fiber-1 (GF-1): the diameter of the glass fiber is 7 mu m, and the glass fiber is international in Chongqing;

alkali-free chopped glass fiber-2 (GF-2): the diameter of the glass fiber is 11 μm, and the Chongqing is international;

alkali-free chopped glass fiber-3 (GF-3): the diameter of the glass fiber is 21 mu m, and the Chongqing is international;

lubricant: pentaerythritol stearate;

antioxidant: tetrakis [ methylene (3, 5-di-tert-butyl-4-hydroxyhydrocinnamate) ] methane, trihexyl chemical;

examples and comparative examples glass fiber reinforced styrene-maleic anhydride copolymer compositions were prepared by the following method: uniformly mixing a styrene maleic anhydride copolymer, a toughening agent and a processing aid, and then putting the mixture into a screw extruder for extrusion granulation at 200-300 ℃, wherein the chopped glass fiber is fed into a double-screw extruder from the side, and finally obtaining a glass fiber reinforced styrene maleic anhydride copolymer resin composition; wherein the screw rotating speed of the double-screw extruder is 100-700 r/min.

The performance test method comprises the following steps:

(1) mechanical properties: and (5) using a male-shocking injection molding machine to injection mold various standard sample strips and templates.

Tensile strength: testing according to ISO527-2019 standard, wherein the tensile speed is 50 mm/min; flexural modulus: testing according to ISO178-2019 standard, with speed of 2mm/min and span of 64 mm; notched Izod impact strength: testing according to ISO180/1Ea-2016 standard; heat distortion temperature: according to ISO 75-2-2013, a heavy load standard test.

(2) Appearance performance: grading the area of the sample plate of the floating fiber, and grading to be 1-5 grade, wherein the defect of the floating fiber of grade 1 is the least; the 5-level "floating fiber" defect is the most serious.

The component contents and performance test results in examples 1 to 11 and comparative example 1 are shown in table 1:

TABLE 1 ingredient contents and Performance test results in examples 1 to 11 and comparative example 1

As can be seen from Table 1, comparing examples 1-3 with comparative example 1, SMA-4 in comparative example 1 has a residual maleic anhydride (residual monomer) content not in the range of 0.1-1000 ppm, and is inferior to examples 1-3 in tensile strength, flexural modulus, notched impact, heat distortion temperature, and "floating fiber" rating; comparing example 3 with examples 1 and 2, it can be seen that SMA-1 in example 3 has the lowest residual maleic anhydride (residual monomer) and a maleic anhydride content of 22%, which is within a proper selection range, and therefore the overall performance is better than that of examples 1-2. As can be seen from the results of the performance tests comparing example 1 with examples 2 to 3, the composition has an overall superior performance when the residual maleic anhydride content is in the range of 5 to 200 ppm.

Comparing examples 8 and 9 with comparative example 1, it can be seen that the residual maleic anhydride content of SMA is in the range of 0.1 to 1000ppm, and even if the contents of the remaining components are different, the performance of the composition as a whole is better than that of comparative example 1.

Comparing examples 3, 4-5, it can be seen that the chopped glass fibers of example 5 do not have tensile strength, flexural modulus, notched impact, heat distortion temperature, and "float fiber" rating in the range of 6-20 as is inferior to examples 3 and 4.

Comparing examples 3 and 6 to 7, it can be seen that the toughening agent of example 7 has a rubber particle diameter of 0.05 to 5.0 μm, and is inferior to examples 3 and 6 in tensile strength, flexural modulus, heat distortion temperature and "floating fiber" rating except for notched impact strength.

Comparing examples 3, 6 and 10, it can be seen that the toughening agent in example 10 has a rubber content of not within the range of 10 to 50%, and the properties other than the notched impact strength are inferior to those in examples 3 and 6.

Comparing examples 3, 6 and 11, it can be seen that the toughening agent in example 11 has a butadiene content of less than 10-65%, and the properties other than the notch impact strength are inferior to those in examples 3 and 6.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.