Polyester compositions, process for their preparation and use, white reflective film

Abstract

The present application relates to the field of polyester composition, discloses a kind of polyester composition and its preparation method and application.The polyester composition includes polyester 100 parts by weight;Crosslinking maleic anhydride copolymer microspheres 8-55 parts by weight;Auxiliary 0.1-15 parts by weight;The crosslinking degree of the crosslinking maleic anhydride copolymer microspheres is ≥65%, and the average particle size is 500-2000nm.The composition contains crosslinking maleic anhydride copolymer microspheres, the particle size size distribution of the copolymer microspheres is uniform, can be dispersed in polyester matrix in the absence of dispersant, compatibilizer, and no agglomeration phenomenon occurs, can avoid the size and its distribution of inorganic particle are not uniform, poor dispersibility, poor compatibility and other shortcomings.The composition is applied in white reflective film, can simplify process flow, improve the light reflectivity of film product.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyester compositions, in particular, to a polyester composition and a preparation method and application thereof, and a white reflective film. BACKGROUND

[0002] Liquid crystal display technology has been widely used, becoming an important part of the optoelectronic information industry. Liquid crystal display is a passive display device, which does not emit light itself, and the displayed image and text are the result of its modulation of the light emitted by the backlight. Therefore, the main indicators of the display, such as brightness, chroma, and power consumption, depend on the performance of the backlight. The main components of the liquid crystal backlight module are: light source, reflective film, light guide plate, diffusion film, brightness enhancement film, and outer frame. The reflective film is located at the bottom of the backlight module, below the light guide plate. Its role is to reflect the light that leaks through the light guide plate back to the panel side, thereby reducing light loss and increasing backlight brightness.

[0003] The types of reflective films mainly include polypropylene (PP), polycarbonate (PC), and polyethylene terephthalate (PET), etc. Compared with PP and PC, PET reflective film has good temperature resistance, ductility, mechanical properties, weather resistance, fatigue resistance, electrical insulation, and chemical resistance, etc. Currently, the main methods for preparing reflective films at home and abroad are coating, multi-layer film, blending, and microporous. The blending method is to directly add reflective particles (such as calcium carbonate, magnesium sulfate, titanium dioxide, silicon dioxide, zinc oxide, and other inorganic particles) into the film, and directly use an extruder for melt extrusion and casting film. The microporous method is to add incompatible components (inorganic particles) to the film, which are not compatible with the base resin, through melt extrusion, casting, longitudinal stretching, transverse stretching, and heat setting, etc. to produce pores in the film, thereby whitening the film and increasing the reflectivity of the film. The introduction of a large number of micrometer-sized pores in the film, with air in the micrometer-sized pores, when light enters the film, it will be reflected or refracted, and part of it will undergo total reflection. A large number of micrometer-sized pores can cause multiple reflections of light, thereby increasing the reflectivity of the film.

[0004] CN100480305C discloses a white polyester film obtained from a composition of copolyester and inorganic particles, the proportion of inorganic particles in the composition is 30-50wt%, the transverse and longitudinal thermal shrinkage rates of the film at 85℃ are ≤0.7%, and the transverse and longitudinal thermal shrinkage rates of the film at 150℃ are ≤5.0%.

[0005] CN102686653B discloses a white reflective film prepared by adding incompatible TOPAS cyclic olefin polymer and inorganic particles TiO2 into PET as the base resin, blending into a film, and stretching to form pores.

[0006] CN102362217B discloses a reflective film that can be used in the backlight unit of a liquid crystal display device. It includes a white reflective layer and a support layer. The white reflective layer is a film with a pore volume ratio of 55-80% obtained by casting a composition of PET and barium sulfate and then stretching it. The support layer is a biaxially stretched polyester film.

[0007] CN103030937B discloses a method of using polyester as a base material, adding inorganic particles (such as titanium dioxide, silicon dioxide or barium sulfate) and resin (such as polyvinylidene fluoride or polydimethylsiloxane), a compatibilizer, an ultraviolet absorber and an antistatic agent to the base material to form a film, and then stretching the film to obtain a single-layer biaxially oriented white reflective polyester film.

[0008] Problems with these methods include uneven distribution of inorganic particles, which affects the film's reflectivity; susceptibility to cracking, making film production difficult; and heavy film weight and poor mechanical properties. Addressing these issues typically requires the introduction of additional dispersants, coupling agents, and compatibilizers, or the use of copolyester as a matrix, which further complicates the process. Copolyester's high thermal shrinkage leads to poor thermal dimensional stability. Summary of the Invention

[0009] To overcome the problems existing in the prior art, the present invention provides a polyester composition, its preparation method, and application, as well as a white reflective film. The composition comprises cross-linked maleic anhydride copolymer microspheres, which exhibit a uniform particle size distribution. These microspheres can be well dispersed in a polyester matrix without the use of dispersants or compatibilizers, without agglomeration. This composition avoids the drawbacks of inorganic particles, such as uneven size and distribution, poor dispersibility, and poor compatibility. Application of this composition in white reflective film can simplify the process and improve the reflectivity of the film product.

[0010] In order to achieve the above object, the first aspect of the present invention provides a polyester composition, characterized in that the composition comprises:

[0011] 100 parts by weight of polyester;

[0012] 8-55 parts by weight of cross-linked maleic anhydride copolymer microspheres;

[0013] 0.1-15 parts by weight of auxiliary agent;

[0014] The cross-linking degree of the cross-linked maleic anhydride copolymer microspheres is ≥65%, and the average particle size is 500-2000nm.

[0015] A second aspect of the present invention provides use of the polyester composition in a white reflective film.

[0016] A third aspect of the present invention provides a method for preparing the above-mentioned polyester composition, characterized in that the method comprises:

[0017] (1) mixing polyester, cross-linked maleic anhydride copolymer microspheres and an antioxidant composite auxiliary agent to obtain a mixture;

[0018] (2) The mixture is melt-blended and extruded in a twin-screw extruder, pelletized, and dried to obtain the polyester composition.

[0019] A fourth aspect of the present invention provides a white reflective film, characterized in that the white reflective film is made from the above-mentioned polyester composition.

[0020] Through the above technical solution, the polyester composition provided by the present invention and its preparation method and application achieve the following beneficial effects:

[0021] The polyester composition provided by the present invention incorporates cross-linked maleic anhydride copolymer microspheres, which can be uniformly dispersed in a polyester resin matrix without the use of a dispersant or compatibilizer. The film produced from the composition also exhibits uniform micropore size. This composition addresses existing issues such as the limited adjustable range of physical properties and reflectivity of reflective films and complex processes, offering broad adaptability, simple operation, and stable product performance. The polyester composition prepared by the present invention can be widely used in the field of white reflective films. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a SEM photograph of a cross section of a polyester composition sample obtained in Example 1;

[0023] Figure 2 is a SEM photograph of a cross section of a polyester composition sample prepared in Comparative Example 2;

[0024] Figure 3 This is a SEM photograph of the cross section of the polyester composition sample prepared in Comparative Example 3. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] A first aspect of the present invention provides a polyester composition, characterized in that the composition comprises:

[0027] 100 parts by weight of polyester;

[0028] 8-55 parts by weight of cross-linked maleic anhydride copolymer microspheres;

[0029] 0.1-15 parts by weight of auxiliary agent;

[0030] The cross-linking degree of the cross-linked maleic anhydride copolymer microspheres is ≥65%, and the average particle size is 500-2000nm.

[0031] The polyester composition provided by the present invention incorporates cross-linked maleic anhydride copolymer microspheres, which can be uniformly dispersed in a polyester resin matrix without the use of a dispersant or compatibilizer. The film produced from the composition also exhibits uniform micropore size. This composition addresses existing issues such as the limited adjustable range of physical properties and reflectivity of reflective films and complex processes, offering broad adaptability, simple operation, and stable product performance. The polyester composition prepared by the present invention can be widely used in the field of white reflective films.

[0032] Furthermore, the composition comprises:

[0033] 100 parts by weight of polyester;

[0034] 10-48 parts by weight of cross-linked maleic anhydride copolymer microspheres;

[0035] 0.3-12 parts by weight of auxiliary agent.

[0036] Furthermore, the cross-linking degree of the cross-linked maleic anhydride copolymer microspheres is ≥70%.

[0037] Furthermore, the average particle size of the cross-linked maleic anhydride copolymer microspheres is 800-1700 nm, preferably 900-1500 nm.

[0038] According to the present invention, the melting enthalpy of the polyester is ΔH mPET , the melting enthalpy of the polyester composition is ΔH m组合物 ;

[0039] Among them, △H mPET and △H m组合物 The difference is 8-28 J / g.

[0040] In the present invention, when the difference between the melting enthalpy of the polyester and the melting enthalpy of the polyester composition satisfies the above range, the cross-linked maleic anhydride copolymer microspheres can be evenly distributed in the polyester composition and can produce a good light reflection effect without a significant decrease in the melting enthalpy due to agglomeration of the cross-linked maleic anhydride copolymer microspheres. As a result, the light reflective film prepared from the composition has both excellent physical properties and reflectivity.

[0041] In the present invention, the melting enthalpy of the polyester and the polyester composition is measured by differential scanning calorimetry.

[0042] Furthermore, ΔH mPET and △H m组合物 The difference is 10-25 J / g.

[0043] According to the present invention, the polyester is selected from at least one of polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyethylene naphthalate (PEN), preferably polyethylene terephthalate (PET).

[0044] According to the present invention, at 25° C., the intrinsic viscosity of the polyester is 0.62-0.88 dL / g.

[0045] According to the present invention, the glass transition temperature of the polyester is 65-85°C.

[0046] According to the present invention, the melting point of the polyester is 240-265°C.

[0047] According to the present invention, the crystallization temperature of the polyester is 168-192°C.

[0048] In a specific embodiment of the present invention, the polyester composition further comprises at least one organic particle selected from linear, branched or cyclic polyolefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, cyclopentadiene, acrylic resins such as poly(meth)acrylate, polystyrene, fluororesins and silicone resins.

[0049] Preferably, the polyester composition further comprises at least one organic particle selected from polyethylene, polystyrene, polypropylene, polybutene, poly-4-methyl-1-pentene, cyclic olefin copolymers, polymethacrylic acid, silicone resin, ethylene-methyl methacrylate copolymer, and ethylene-vinyl acetate copolymer, preferably polypropylene, poly-4-methyl-1-pentene, and cyclic olefin copolymer. The amount of the organic particles used is not particularly limited. For example, the amount of the organic particles is 10-20 parts per 100 parts of the polyester.

[0050] According to the present invention, the auxiliary agent includes at least one of an antioxidant, a heat stabilizer, an antistatic agent, an anti-hydrolysis agent, a nucleating agent, a flame retardant and an ultraviolet absorber.

[0051] According to the present invention, the antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butyl)phenyl phosphite, octadecyl propionate and alkylated polyphenols.

[0052] Furthermore, the antioxidant is pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Antioxidant 1010) and (2,4-di-tert-butylphenyl)trisphosphite; or, n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Antioxidant 1076) and (2,4-di-tert-butylphenyl)trisphosphite. Specifically, the weight ratio of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to (2,4-di-tert-butylphenyl)trisphosphite is 1-3:1, preferably 2-3:1.

[0053] According to the present invention, the heat stabilizer is a phosphorus-based heat stabilizer, preferably at least one selected from trimethyl phosphate, triphenyl phosphate and triethyl phosphate.

[0054] According to the present invention, the antistatic agent is at least one selected from ethoxylated alkylamines, tetraalkylammonium salts, alkylbenzene sulfonates, alkyl sulfonates, polyetheresteramides, polyetheramideimides, and copolymers of methoxypolyethylene glycol and methacrylate.

[0055] According to the present invention, the anti-hydrolysis agent is selected from carbodiimides, preferably at least one selected from dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide and polycarbodiimide.

[0056] According to the present invention, the nucleating agent is selected from at least one of an inorganic salt nucleating agent, an organic acid salt nucleating agent, an ionomer nucleating agent, and an alkali metal salt nucleating agent of a polyester oligomer. In the present invention, the inorganic salt nucleating agent is selected from at least one of a carbonate nucleating agent, a silicate nucleating agent, and a sulfate nucleating agent; and the organic acid salt nucleating agent is selected from at least one of a monocarboxylate nucleating agent, a benzoate nucleating agent, an aromatic hydroxysulfonic acid metal salt nucleating agent, and an organophosphorus compound nucleating agent.

[0057] According to the present invention, the flame retardant is selected from brominated organic flame retardants and / or inorganic flame retardants. In the present invention, the inorganic flame retardant is selected from at least one of aluminum hydroxide, magnesium hydroxide, zinc borate and molybdenum ditelluride.

[0058] According to the present invention, the ultraviolet absorber is selected from at least one of methyl o-hydroxybenzoate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,4-dihydroxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone.

[0059] In the present invention, the amounts of the antioxidant, the heat stabilizer, the antistatic agent, the anti-hydrolysis agent, the nucleating agent, the flame retardant and the ultraviolet absorber may be conventional amounts in the art.

[0060] According to the present application, the cross-linked maleic anhydride copolymer microspheres comprise structural unit A from maleic anhydride, structural unit B from the comonomer M and cross-linking structural unit;

[0061] In the copolymer, the molar ratio between the structural unit A, the structural unit B and the cross-linking structural unit is 100:100-120:1-40.

[0062] Further, in the copolymer, the molar ratio between the structural unit A, the structural unit B and the cross-linking structural unit is 100:100-105:10-30.

[0063] According to the present application, the comonomer M is selected from at least one of the compounds shown in formula (1), vinyl acetate, carbon tetra-olefins and carbon penta-olefins;

[0064] wherein R is H or methyl.

[0065] In the present application, the mixed carbon four refers to the general term of hydrocarbon compounds with four carbon atoms (mainly including butene), generally, in addition to various different structures of butene (such as trans-2-butene, cis-2-butene, n-butene, isobutene), the mixed carbon four also includes a certain amount of alkanes (such as n-butane) and other possible impurities. In the present application, the content of olefins in the mixed carbon four is in the range of 60-75% by weight.

[0066] In the present application, the mixed carbon five refers to the general term of hydrocarbon compounds with five carbon atoms (mainly including pentene), generally, in addition to various different structures of pentene (such as dienes (isoprene, cyclopentadiene, 1,4-pentadiene, piperonal) and mono-olefins (1-pentene, 2-pentene, cyclopentene, 2-methyl-1-butene, 2-methyl-2-butene)), the mixed carbon five also includes a certain amount of alkanes (such as n-pentane, isopentane, cyclopentane, 2-methylbutane), acetylenes (such as butyne-2, 3-pentene-1-yne) and other possible impurities. In the present application, the content of olefins in the mixed carbon five is 55-65% by weight.

[0067] In one specific embodiment of the present application, the cross-linked maleic anhydride copolymer microspheres are prepared according to the following steps:

[0068] In the presence of an initiator, maleic anhydride, the comonomer M shown in formula (I) and a cross-linking agent are contacted to react in an organic solvent to obtain the cross-linked maleic anhydride copolymer microspheres;

[0069] The comonomer M is selected from at least one of the compounds shown in formula (I), vinyl acetate, mixed carbon four and mixed carbon five.

[0070]

[0071] Wherein, in formula I, R is H or methyl.

[0072] In one embodiment of the present invention, the amount of the comonomer M is 50-150 mol, more preferably 75-100 mol, relative to 100 mol of maleic anhydride.

[0073] In the present invention, there is no particular limitation on the amount of the organic solvent, as long as it can provide a medium for the reaction. Preferably, the amount of the organic solvent is 50-150 L, more preferably 75-100 L, relative to 100 mol of maleic anhydride.

[0074] In the present invention, the organic solvent can be a common solvent for various solution polymerization reactions. For example, the organic solvent includes an organic acid alkyl ester, that is, an organic acid alkyl ester, or a mixture of an organic acid alkyl ester and an alkane, or a mixture of an organic acid alkyl ester and an aromatic hydrocarbon. The organic acid alkyl ester includes, but is not limited to, at least one of methyl formate, ethyl formate, propyl formate, butyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, benzyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, isobutyl butyrate, isoamyl butyrate, isoamyl isovalerate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, isoamyl benzoate, methyl phenylacetate, and ethyl phenylacetate. The alkane includes, but is not limited to, n-hexane and / or n-heptane. The aromatic hydrocarbons include, but are not limited to, at least one of benzene, toluene and xylene.

[0075] In the present invention, there is no particular requirement for the amount of the initiator. Preferably, the amount of the initiator is 0.05-10 mol, preferably 0.8-1.5 mol, relative to 100 mol of maleic anhydride.

[0076] In the present invention, the initiator can be a reagent commonly used in the art for initiating the polymerization reaction of maleic anhydride and a comonomer (such as α-methylstyrene, styrene, etc.), and can be a thermal decomposition initiator. Preferably, the initiator is selected from at least one of dibenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, dodecyl peroxide, tert-butyl perbenzoate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, azobisisobutyronitrile, and azobisisoheptonitrile.

[0077] In the present invention, there is no particular limitation on the amount of the cross-linking agent used. Preferably, the amount of the cross-linking agent used is 5-30 mol, more preferably 10-20 mol, relative to 100 mol of maleic anhydride.

[0078] In the present invention, the crosslinking agent can be any common vinyl-containing monomer with a functionality of two or more and capable of free radical polymerization. Preferably, the crosslinking agent is selected from divinylbenzene and / or an acrylate crosslinking agent containing at least two acrylate groups, wherein the acrylate groups have the structural formula: -OC(O)-C(R')=CH2, where R' is H or a C1-C4 alkyl group (e.g., methyl).

[0079] Further, the cross-linking agent is selected from at least one of divinylbenzene, propylene glycol bis(meth)acrylates (such as 1,3-propylene glycol dimethacrylate, 1,2-propylene glycol dimethacrylate, 1,3-propylene glycol diacrylate, 1,2-propylene glycol diacrylate), ethylene glycol bis(meth)acrylates (ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol diacrylate), trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol phthalate diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and ethoxylated multifunctional acrylate.

[0080] Furthermore, the cross-linking agent is divinylbenzene.

[0081] According to the present invention, the reaction conditions include: carrying out the reaction in the presence of an inert atmosphere, a reaction temperature of 50-90° C., a reaction time of 3-15 h, and a reaction pressure of 0.1-1 MPa.

[0082] Furthermore, the reaction temperature is 60-70° C., the reaction time is 5-12 h, and the reaction pressure is 0.1-0.5 MPa.

[0083] In the present invention, the product (suspension) of the above reaction is subjected to post-treatment steps such as separation, washing and drying to obtain maleic anhydride copolymer microspheres having a cross-linked structure.

[0084] In the present invention, a water bath and / or an oil bath is used to provide the heat required for the polymerization of the present invention.

[0085] In the present invention, the copolymer emulsion suspension obtained by the polymerization reaction is separated by solid-liquid separation to obtain composite microspheres.

[0086] In the present invention, conventional solid-liquid separation methods in the prior art can be used, preferably centrifugal separation.

[0087] In the present invention, when centrifugal separation is adopted, the centrifugal speed is 1500-5000 rad / min and the centrifugal time is 5-60 min.

[0088] According to the present invention, the composition does not contain dispersants, compatibilizers and coupling agents.

[0089] A second aspect of the present invention provides use of the polyester composition in a white reflective film.

[0090] A third aspect of the present invention provides a method for preparing the above-mentioned polyester composition, characterized in that the method comprises:

[0091] (1) mixing polyester, cross-linked maleic anhydride copolymer microspheres and an auxiliary agent to obtain a mixture;

[0092] (2) The mixture is melt-blended and extruded in a twin-screw extruder, pelletized, and dried to obtain the polyester composition.

[0093] According to the present invention, the rotation speed of the twin-screw extruder is 80-300 r / min.

[0094] According to the present invention, the temperatures of the feeding section, melting section, homogenizing section and die head of the twin-screw extruder are 200-230°C, 240-260°C, 255-275°C and 250-270°C respectively.

[0095] A fourth aspect of the present invention provides a white reflective film, characterized in that the white reflective film is made from the above-mentioned polyester composition.

[0096] In the present invention, the white reflective film prepared from the polyester composition not only retains the excellent physical properties of the polyester composition, but more importantly, has high light reflectivity and can be widely used in the field of light reflective films.

[0097] In the present invention, there is no particular limitation on the preparation method of the white reflective film and the film can be prepared according to conventional methods in the art. For example, the polyester composition is melted at 275°C using a single-screw extruder with an aspect ratio greater than 40, extruded through a single-layer T-shaped die to form a single-layer thick sheet, and then cooled to 30-60°C by rollers passing cold water at 20°C to form a polyester cast sheet. The cast sheet is preheated at 80-180°C and then uniaxially stretched by 2-5 times to form a polyester film. The polyester film then enters a heat setting zone in an electric heating channel at a heat setting temperature of 100-200°C. The polyester film is then cooled at 60-80°C after passing through the heat setting zone to obtain a white reflective polyester film with an average thickness of 0.1-0.3 mm.

[0098] The present invention will be described in detail below through examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0099] The relevant data in the present invention and its embodiments were obtained by the following test methods:

[0100] 1. Degree of cross-linking of cross-linked maleic anhydride copolymer: The degree of cross-linking is the gel content. Weigh 2-3 g of polymer microspheres (w1), wrap them with medium-speed qualitative filter paper, place them in a Soxhlet extractor, and extract them with tetrahydrofuran for 24 hours. The polymer is dried and weighed w2, and the degree of cross-linking is calculated by w2 / w1;

[0101] 2. Content of each structural unit in the copolymer: For cross-linked maleic anhydride-α-methylstyrene copolymer microspheres, LC-MC analysis is used to analyze the amount of monomer or cross-linking agent that does not participate in the reaction, and the molar ratio of structural unit A, structural unit B, and cross-linking structural unit is calculated based on the feed amount; for cross-linked mixed C4-maleic anhydride copolymer microspheres, X-ray fluorescence spectroscopy is used to determine the carbon and oxygen contents in the polymer; the clear liquid after centrifugation is analyzed by gas chromatography to determine the remaining maleic anhydride and cross-linking agent contents; and the molar ratio of structural unit A, structural unit B, and cross-linking structural unit in the polymer can be calculated based on the comprehensive analysis results.

[0102] 3. Copolymer microsphere particle size test method: After the copolymer microsphere powder is vacuum-sprayed with gold, the morphology is observed on a Hitachi S4800 field emission scanning electron microscope. 500 microspheres are selected from the electron microscope photographs, and their diameters are measured. The average particle size of the microspheres is calculated using the mathematical averaging method.

[0103] 4. Intrinsic Viscosity: Place approximately 10g of sample in liquid nitrogen and cool for 10 minutes. Remove the sample and immediately crush it using a pulverizer for no more than 30 seconds. Grind the entire sample to a particle size of less than 1mm. Determine the intrinsic viscosity using an Ubbelohde viscometer using the method and solvent specified in GB / T 14190-2017.

[0104] 5. Morphology of the polyester sample cross section and dispersion of incompatible components: The sample was immersed in liquid nitrogen for 15 minutes and then fractured. The cross section was then gold-sprayed and characterized using a Hitachi S4800 field emission scanning electron microscope to obtain microscopic morphology photographs.

[0105] 6. T C, Tm and △Hm: Differential scanning calorimetry was used to analyze the melting and crystallization processes of the material. The specific operation was as follows: Under nitrogen protection, 5-10 mg of sample was measured from 20℃ to 300℃ using a three-stage temperature ramp measurement method. The change in heat flow reflects the melting and crystallization process of the material. The crystallization temperature T was calculated according to GB / T 19466.3-2004. C , melting temperature Tm and melting enthalpy △Hm;

[0106] 7. Tensile properties: measured according to the method specified in GB / T 1040.3-2006 using the INSTRON universal tensile testing machine produced by Instron Corporation of the United States.

[0107] 8. Reflectivity: Reflectivity was measured using a HunterLab ColorQuestXE spectrometer (USA) under a D65 illuminant using an integrating sphere with a d / 8° configuration, in accordance with the method specified in GB / T 3979-2008. Reflectivity data is a weighted average of the reflectivity at 10nm wavelength intervals from 400-700nm, with the weights corresponding to the energy distribution curve of the D65 illuminant.

[0108] Polyester: PET-1, intrinsic viscosity 0.66 dL / g, glass transition temperature 79.1°C, crystallization temperature 188.9°C, melting point 259.1°C, purchased from Sinopec Yizheng Chemical Fiber Co., Ltd.

[0109] Polyester: PET-2, intrinsic viscosity 0.84 dL / g, glass transition temperature 68.2°C, crystallization temperature 171.5°C, melting point 255.1°C, purchased from China Resources Chemical Materials Technology Co., Ltd.

[0110] Polyester: PET-3, intrinsic viscosity 0.76 dL / g, glass transition temperature 74.4°C, crystallization temperature 178.5°C, melting point 257.3°C, purchased from Zhejiang Hengyi High-tech Materials Co., Ltd.

[0111] Other raw materials used in the examples and comparative examples are all commercially available.

[0112] Preparation Example 1

[0113] Maleic anhydride 430 g, α-methylstyrene 520 g, divinylbenzene 95 g, azobisisobutyronitrile 9 g were dissolved in 4.2 L of isopentyl acetate, and the reaction was carried out under a nitrogen atmosphere at 0.1 MPa and 70°C for 5 hours. The reaction system was centrifuged at 5000 rpm for 30 minutes after the reaction to obtain crosslinked α-methylstyrene / maleic anhydride polymer microspheres Al, which were washed and purified with n-hexane and dried in a vacuum. The amount of α-methylstyrene was 99.4 mol, the amount of divinylbenzene was 16.6 mol, and the amount of initiator was 1.2 mol, with respect to 100 mol of maleic anhydride.

[0114] The crosslinking degree of the crosslinked maleic anhydride-α-methylstyrene copolymer microspheres Al was 81%, the molar ratio between the structural unit A, the structural unit B, and the crosslinking structural unit was 100:101:25, and the average particle size of the copolymer microspheres was 1180 nm.

[0115] Preparation Example 2

[0116] Maleic anhydride 430 g, α-methylstyrene 520 g, divinylbenzene 95 g, azobisisobutyronitrile 9 g were dissolved in 4.2 L of isopentyl acetate, and the reaction was carried out under a nitrogen atmosphere at 0.1 MPa and 70°C for 5 hours. The reaction system was centrifuged at 5000 rpm for 30 minutes after the reaction to obtain crosslinked α-methylstyrene / maleic anhydride polymer microspheres Al, which were washed and purified with n-hexane and dried in a vacuum. The amount of α-methylstyrene was 99.4 mol, the amount of divinylbenzene was 16.6 mol, and the amount of initiator was 1.2 mol, with respect to 100 mol of maleic anhydride.

[0117] The crosslinking degree of the crosslinked maleic anhydride-α-methylstyrene copolymer microspheres Al was 81%, the molar ratio between the structural unit A, the structural unit B, and the crosslinking structural unit was 100:101:25, and the average particle size of the copolymer microspheres was 1180 nm.

[0118] Preparation Example 3

[0119] Maleic anhydride 430 g, α-methylstyrene 520 g, divinylbenzene 95 g, azobisisobutyronitrile 9 g were dissolved in 4.2 L of isopentyl acetate, and the reaction was carried out under a nitrogen atmosphere at 0.1 MPa and 70°C for 5 hours. The reaction system was centrifuged at 5000 rpm for 30 minutes after the reaction to obtain crosslinked α-methylstyrene / maleic anhydride polymer microspheres Al, which were washed and purified with n-hexane and dried in a vacuum. The amount of α-methylstyrene was 99.4 mol, the amount of divinylbenzene was 16.6 mol, and the amount of initiator was 1.2 mol, with respect to 100 mol of maleic anhydride.

[0120] The crosslinking degree of the crosslinked maleic anhydride-α-methylstyrene copolymer microspheres A1 is 72%, the molar ratio among the structural unit A, the structural unit B and the crosslinking structural unit is 100:102:24, and the average particle size of the copolymer microspheres is 1480 nm.

[0121] Preparation Example 4

[0122] The composition of the mixed butene gas is as follows: trans-2-butene, 40.83% by weight; cis-2-butene, 18.18% by weight; n-butane, 24.29% by weight; n-butene, 9.52% by weight; iso-butene, 2.78% by weight; and others, 4.4% by weight. A measured amount of the mixed butene (the molar ratio of maleic anhydride to the effective component (terminal olefin) in the mixed olefin is 1:1) is introduced into a 1L isopentyl acetate solution containing maleic anhydride at a concentration of 1 mol / L, 0.05 mol / L azobisisobutyronitrile and 0.2 mol / L divinylbenzene under a nitrogen atmosphere, and the system is reacted at 70°C for 6 hours under a relative pressure of 0.5 MPa of nitrogen. The reacted system is centrifuged at 5000 rad / min for 30 minutes to obtain crosslinked mixed butene / maleic anhydride polymer microspheres A4, which are washed and purified with n-hexane and vacuum dried. Herein, the amount of the mixed butene (effective component) is 100 mol, the amount of divinylbenzene is 20 mol, and the amount of the initiator is 5 mol, relative to 100 mol of maleic anhydride.

[0123] The crosslinking degree of the crosslinked mixed butene / maleic anhydride copolymer microspheres A4 is 76%, the molar ratio among the structural unit A, the structural unit B and the crosslinking structural unit is 100:100:25, and the average particle size of the copolymer microspheres is 1100 nm.

[0124] Preparation Example 5

[0125] The ionomer microspheres are prepared according to the method of Preparation Example 1, except that the amount of divinylbenzene is 190 g, to obtain crosslinked α-methylstyrene / maleic anhydride polymer microspheres A5. Herein, the amount of α-methylstyrene is 99.4 mol, the amount of divinylbenzene is 33.3 mol, and the amount of the initiator is 1.2 mol, relative to 100 mol of maleic anhydride.

[0126] The crosslinking degree of the crosslinked maleic anhydride-α-methylstyrene copolymer microspheres A5 is 88%, the molar ratio among the structural unit A, the structural unit B and the crosslinking structural unit is 100:101:31, and the average particle size of the copolymer microspheres is 420 nm.

[0127] Example 1

[0128] Preparation of the polyester composition

[0129] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 25 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two is 2:1.

[0130] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section, and die of the twin-screw extruder were 220℃, 240℃, 265℃, and 260℃, respectively, and the screw rotation speed was 150 r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1. The polyester composition was melted at 265℃ and pressed into a sheet, and the thickness of the sheet was 140-180μm. Figure 1 is a SEM photo of the cross section of the polyester composition sheet. From the SEM photo, it can be seen that the crosslinked maleic anhydride copolymer microspheres are uniformly distributed in the polyester matrix. Figure 1 It can be seen that the crosslinked maleic anhydride copolymer microspheres have uniform particle size and are uniformly distributed in the polyester matrix.

[0131] Example 2

[0132] Preparation of the polyester composition

[0133] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 11 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two is 2:1.

[0134] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section, and die of the twin-screw extruder were 220℃, 240℃, 265℃, and 260℃, respectively, and the screw rotation speed was 150 r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1.

[0135] Example 3

[0136] Preparation of the polyester composition

[0137] 100 parts of PET-2 were dried at 140℃ for 5h, and then blended with 43 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two was 2:1.

[0138] The mixed granules were added to a twin-screw extruder for granulation, the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder were 220℃, 240℃, 265℃ and 260℃ respectively, the rotation speed of the screw was 150r / min, and the polyester composition of the application was obtained by granulation. The performance of the polyester composition was tested after the polyester composition was dried at 140℃ for 12h, and the performance results are shown in Table 1.

[0139] Example 4

[0140] Preparation of the polyester composition

[0141] 100 parts of PET-3 were dried at 140℃ for 5h, and then blended with 25 parts of crosslinked maleic anhydride copolymer microspheres A2, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two was 2:1.

[0142] The mixed granules were added to a twin-screw extruder for granulation, the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder were 220℃, 240℃, 265℃ and 260℃ respectively, the rotation speed of the screw was 150r / min, and the polyester composition of the application was obtained by granulation. The performance of the polyester composition was tested after the polyester composition was dried at 140℃ for 12h, and the performance results are shown in Table 1.

[0143] Example 5

[0144] Preparation of the polyester composition

[0145] 100 parts of PET-3 were dried at 140℃ for 5h, and then blended with 25 parts of crosslinked maleic anhydride copolymer microspheres A3, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two was 2:1.

[0146] The mixed granules are added to a twin-screw extruder for granulation, the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder are 220℃, 240℃, 265℃ and 260℃ respectively, the rotation speed of the screw is 150r / min, and the polyester composition of the present application is obtained by granulation. The performance of the polyester composition is tested after the polyester composition is dried at 140℃ for 12h, and the performance results are shown in Table 1.

[0147] Example 6

[0148] Preparation of the polyester composition

[0149] 100 parts of PET-1 are dried at 140℃ for 5h, and are blended with 25 parts of crosslinked maleic anhydride copolymer microspheres A4, 1 part of antioxidant and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed stirrer, wherein the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two is 2:1.

[0150] The mixed granules are added to a twin-screw extruder for granulation, the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder are 220℃, 240℃, 265℃ and 260℃ respectively, the rotation speed of the screw is 150r / min, and the polyester composition of the present application is obtained by granulation. The performance of the polyester composition is tested after the polyester composition is dried at 140℃ for 12h, and the performance results are shown in Table 1.

[0151] Example 7

[0152] Preparation of the polyester composition

[0153] 100 parts of PET-1 are dried at 140℃ for 5h, and are blended with 54 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed stirrer, wherein the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two is 2:1.

[0154] The mixed granules are added to a twin-screw extruder for granulation, the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder are 220℃, 240℃, 265℃ and 260℃ respectively, the rotation speed of the screw is 150r / min, and the polyester composition of the present application is obtained by granulation. The performance of the polyester composition is tested after the polyester composition is dried at 140℃ for 12h, and the performance results are shown in Table 1.

[0155] Comparative Example 1

[0156] Preparation of the polyester composition

[0157] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 5 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two was 2:1.

[0158] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section, and die of the twin-screw extruder were 220℃, 240℃, 265℃, and 260℃, respectively, and the screw rotation speed was 150 r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1.

[0159] Comparative Example 2

[0160] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 25 parts of nano-CaCO3 powder (Shanghai Yinjiang Chemical Co., Ltd., 10000 mesh), 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the two was 2:1.

[0161] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section, and die of the twin-screw extruder were 220℃, 240℃, 265℃, and 260℃, respectively, and the screw rotation speed was 150 r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1. The polyester composition was melted at 265℃ and pressed into a tablet, and the thickness of the tablet was 140-180μm. Figure 2 is a SEM photo of the cross section of the polyester composition tablet. It can be seen from the photo that the inorganic powder is distributed uniformly, and there is no obvious agglomeration. Figure 2 It can be seen that the inorganic powder is not uniformly distributed, and obvious agglomeration occurs.

[0162] Comparative Example 3

[0163] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 25 parts of nano BaSO4 powder (Sahali Blanc Fixe Micro, organic coated, d50=0.7μm), 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, in a weight ratio of 2:1.

[0164] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder were 220℃, 240℃, 265℃ and 260℃ respectively, and the screw rotation speed was 150r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1. The polyester composition was melted at 265℃ and then tabletted, and the thickness of the sample tablet was 140-180μm. Figure 3 is a SEM photo of the cross section of the polyester composition sample tablet. It can be seen from Figure 3 It can be seen that the inorganic powder is unevenly distributed, and obvious agglomeration occurs.

[0165] Comparative Example 4

[0166] 100 parts of PET-1 were dried at 140℃ for 5h, and then blended with 75 parts of crosslinked maleic anhydride copolymer microspheres A1, 1 part of antioxidant, and 0.2 parts of thermal stabilizer trimethyl phosphate in a high-speed mixer, wherein the antioxidant was β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecyl ester (antioxidant 1076) and (2,4-di-tert-butylphenyl) phosphite, in a weight ratio of 2:1.

[0167] The mixed granules were added to a twin-screw extruder for granulation, and the temperatures of the feeding section, melting section, homogenizing section and die of the twin-screw extruder were 220℃, 240℃, 265℃ and 260℃ respectively, and the screw rotation speed was 150r / min, to obtain the polyester composition of the present application. The polyester composition was dried at 140℃ for 12h, and then the performance of the polyester composition was tested, and the performance results are shown in Table 1.

[0168] Comparative Example 5

[0169] 100 parts of PET-1 were dried at 140°C for 5 hours and blended with 25 parts of maleic anhydride copolymer microspheres A5, 1 part of antioxidant, and 0.2 parts of heat stabilizer trimethyl phosphate in a high-speed blender. The antioxidant used was β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (antioxidant 1076) and (2,4-di-tert-butylphenyl) triester phosphite, and the weight ratio of the two was 2:1.

[0170] The homogenized pellets were added to a twin-screw extruder for pelletization. The temperatures of the feed section, melting section, homogenizing section, and die head of the twin-screw extruder were set at 220°C, 240°C, 265°C, and 260°C, respectively, and the screw speed was 150 r / min. The polyester composition of the present invention was pelletized. The polyester composition was dried at 140°C for 12 hours and then tested for its properties. The performance results are shown in Table 1.

[0171] Table 1

[0172]

[0173] It can be seen from Table 1 that the difference in melting enthalpy (ΔH mPET and △H m组合物 The difference between the two) meets the scope of the present invention, indicating that the composition provided by the present invention can improve the uniformity of dispersion of maleic anhydride copolymer microspheres in the matrix resin without using any coupling agent, dispersant and compatibilizer, thereby enabling the polyester composition to meet the requirements of the stretching ratio and reflectivity of the reflective film.

[0174] Test Case

[0175] The polyester compositions of the examples and comparative examples were melted at 275°C using a single-screw extruder with an aspect ratio greater than 40, extruded through a single-layer T-shaped die, and then cooled to 30-60°C by rollers passing cold water at 20°C to produce a polyester cast sheet. The cast sheet was preheated at 80-180°C and then uniaxially stretched 2-5 times to produce a polyester film. The polyester film then entered a heat setting zone in an electric heating channel at a heat setting temperature of 100-200°C. After passing through the heat setting zone, the polyester film was cooled at 60-80°C to produce a white reflective polyester film with an average thickness of 0.1-0.3 mm.

[0176] Table 2

[0177] project Reflectivity (%) Example 1 97.3 Example 2 96.8 Example 3 96.9 Example 4 96.8 Example 5 96.7 Example 6 96.6 Example 7 96.5 Comparative Example 1 95.1 Comparative Example 2 95.3 Comparative Example 3 95.4 Comparative Example 4 95.5 Comparative Example 5 95.6

[0178] As shown in Table 2, the reflectivity of the light-reflecting films produced from the polyester compositions of the present invention is consistently greater than 96%, indicating that the films exhibit excellent light-reflecting properties, are free of surrounding shadows, and can reduce light loss. The resulting light-reflecting films are suitable for use in ultra-thin direct-lit backlight modules.

[0179] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A polyester composition, characterized in that The composition comprises: 100 parts by weight of polyester; 8-55 parts by weight of cross-linked maleic anhydride copolymer microspheres; 0.1-15 parts by weight of auxiliary agent; The cross-linked maleic anhydride copolymer microspheres have a cross-linking degree of ≥65% and an average particle size of 500-2000 nm; The melting enthalpy of the polyester is △ H mPET , the melting enthalpy of the polyester composition is △ H m组合物 ; in, △ H mPET and △ H m组合物 The difference is 8-28 J / g; Wherein, the polyester is polyethylene terephthalate; The cross-linked maleic anhydride copolymer microspheres contain a copolymer comprising a structural unit A derived from maleic anhydride, a structural unit B derived from a comonomer M, and a cross-linked structural unit; In the copolymer, the molar ratio of the structural unit A, the structural unit B and the cross-linking structural unit is 100:100-120:1-40; The comonomer M is selected from at least one of the compound represented by formula (1), vinyl acetate, C4 olefins and C5 olefins; Formula (1); wherein R is H or methyl.

2. The polyester composition according to claim 1, wherein The composition comprises: 100 parts by weight of polyester; 10-48 parts by weight of cross-linked maleic anhydride copolymer microspheres; 0.3-12 parts by weight of auxiliary agent.

3. The polyester composition according to claim 1 or 2, wherein The cross-linking degree of the cross-linked maleic anhydride copolymer microspheres is ≥70%; And / or, the average particle size of the cross-linked maleic anhydride copolymer microspheres is 800-1700 nm.

4. The polyester composition according to claim 1 or 2, wherein △ H mPET and △ H m组合物 The difference is 10-25 J / g.

5. The polyester composition according to claim 1 or 2, wherein At 25° C., the intrinsic viscosity of the polyester is 0.62-0.88 dL / g; and / or, the polyester has a glass transition temperature of 65-85°C; and / or, the polyester has a melting point of 240-265° C.; And / or, the polyester has a crystallization temperature of 168-192°C.

6. The polyester composition according to claim 1 or 2, wherein The polyester composition further comprises at least one organic particle selected from the group consisting of polyethylene, polystyrene, polypropylene, polybutene, poly-4-methyl-1-pentene, cyclic olefin copolymer, polymethacrylic acid, silicone resin, ethylene-methyl methacrylate copolymer and ethylene-vinyl acetate copolymer.

7. The polyester composition according to claim 1 or 2, wherein The auxiliary agent includes at least one of an antioxidant, a heat stabilizer, an antistatic agent, an anti-hydrolysis agent, a nucleating agent, a flame retardant and an ultraviolet absorber.

8. The polyester composition according to claim 7, wherein The antioxidant is at least one selected from the group consisting of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butyl)phenyl phosphite, octadecyl propionate, and alkylated polyphenols; And / or, the thermal stabilizer is a phosphorus-based thermal stabilizer; and / or, the antistatic agent is selected from at least one of ethoxylated alkylamines, tetraalkylammonium salts, alkylbenzene sulfonates, alkyl sulfonates, polyetheresteramides, polyetheramideimides, and copolymers of methoxypolyethylene glycol and methacrylate; and / or, the anti-hydrolysis agent is selected from carbodiimides; And / or, the nucleating agent is at least one selected from the group consisting of inorganic salt nucleating agents, organic acid salt nucleating agents, ionomer nucleating agents, and alkali metal salt nucleating agents of polyester oligomers; and / or, the flame retardant is selected from brominated organic flame retardants and / or inorganic flame retardants; And / or, the ultraviolet absorber is selected from at least one of methyl o-hydroxybenzoate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,4-dihydroxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone.

9. The polyester composition according to claim 8, wherein The heat stabilizer is selected from at least one of trimethyl phosphate, triphenyl phosphate and triethyl phosphate; And / or, the anti-hydrolysis agent is at least one selected from dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide and polycarbodiimide.

10. The polyester composition according to claim 8, wherein The antioxidants are pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and (2,4-di-tert-butylphenyl)trisphosphite; Alternatively, the antioxidant is n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and (2,4-di-tert-butylphenyl) phosphite triester.

11. The polyester composition according to claim 10, wherein The weight ratio of the pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) or the n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to the (2,4-di-tert-butylphenyl)trisphosphite is 1-3:

1.

12. The polyester composition according to claim 1, wherein In the copolymer, the molar ratio of the structural unit A, the structural unit B and the cross-linking structural unit is 100:100-105:10-30.

13. The polyester composition according to claim 1 or 2, wherein The cross-linked maleic anhydride copolymer microspheres are prepared according to the following method: In an organic solvent, in the presence of an initiator, maleic anhydride, a comonomer M represented by formula (I) and a crosslinking agent are contacted and reacted to obtain the crosslinked maleic anhydride copolymer microspheres; The comonomer M is selected from at least one of the compound represented by formula (I), vinyl acetate, mixed C4 and mixed C5; Formula I; Wherein, in formula I, R is H or methyl.

14. The polyester composition according to claim 13, wherein Relative to 100 mol of maleic anhydride, the amount of the comonomer M is 50-150 mol; the amount of the initiator is 0.05-10 mol; and the amount of the cross-linking agent is 5-30 mol.

15. The polyester composition according to claim 14, wherein For 100 mol of maleic anhydride, the amount of the comonomer M is 75-100 mol; the amount of the initiator is 0.8-1.5 mol; and the amount of the cross-linking agent is 10-20 mol.

16. The polyester composition according to claim 13, wherein The organic solvent includes an organic acid alkyl ester; and / or, the initiator is at least one selected from the group consisting of dibenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, dodecyl peroxide, tert-butyl perbenzoate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, azobisisobutyronitrile, and azobisisoheptonitrile; And / or, the cross-linking agent is selected from divinylbenzene and / or an acrylate cross-linking agent containing at least two acrylate groups.

17. The polyester composition according to claim 16, wherein The structural formula of the acrylate group is: -OC(O)-C(R')=CH2, where R' is H or a C1-C4 alkyl group.

18. The polyester composition according to claim 13, wherein The crosslinking agent is selected from at least one of divinylbenzene, propylene glycol diacrylate, propylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, diethylene glycol phthalate diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and ethoxylated multifunctional acrylate.

19. The polyester composition according to claim 18, wherein The cross-linking agent is divinylbenzene.

20. The polyester composition according to claim 13, wherein The reaction conditions include: carrying out the reaction in the presence of an inert atmosphere, a reaction temperature of 50-90° C., a reaction time of 3-15 h, and a reaction pressure of 0.1-1 MPa.

21. The polyester composition according to claim 1 or 2, wherein The composition does not contain dispersants, compatibilizers and coupling agents.

22. Use of the polyester composition according to any one of claims 1 to 21 in a white reflective film.

23. A method for preparing the polyester composition according to any one of claims 1 to 21, characterized in that: The method comprises: (1) mixing polyester, cross-linked maleic anhydride copolymer microspheres and an additive to obtain a mixture; (2) The mixture is melt-blended, extruded, pelletized, and dried in a twin-screw extruder to obtain the polyester composition.

24. The preparation method according to claim 23, wherein The speed of the twin-screw extruder is 80-300 r / min; And / or, the temperatures of the feeding section, melting section, homogenizing section and die head of the twin-screw extruder are 200-230° C., 240-260° C., 255-275° C. and 250-270° C., respectively.

25. A white reflective film, characterized in that: The white reflective film is made from the polyester composition according to any one of claims 1 to 21.

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