Special white master batch for high-thermal-stability and high-toughness polyester film applied to two-way stretching and preparation method of special white master batch

Abstract

The invention particularly relates to a white master batch special for a high-thermal-stability and high-toughness polyester film applied to two-way stretching and a preparation method of the white master batch. The white master batch is prepared from the following raw materials: PET, PMDA and EEA. The method is used for solving the problems that in the PET processing process, the requirement for temperature control is high, and PET thermal degradation is easily caused; the problems that the tensile property is reduced after PET thermal degradation, the surface of the film is uneven, and rough frosted textures are caused are solved; and the crystal points of the film are effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of waste material recycling and reuse, and specifically relates to a white masterbatch specially used for biaxially stretched polyester film with high thermal stability and high toughness, and a preparation method thereof. Background Art

[0002] Due to its excellent properties, BOPET film is widely used in packaging for cigarettes, audiovisual products, and food, as well as in bag making, adhesive tape, metal coating, packaging materials, card holders, imaging films, hot stamping foil, capacitor film, anti-counterfeiting, signage, tear cords, adhesive tape, specialty electrical appliances, film, X-ray film, and electrical insulation. Film thickness varies, with thin, medium, and thick grades being generally considered general-purpose films, typically ranging in thickness from 6 to 65 μm, and primarily used in packaging. Ultra-thin and thick grades are used as specialty films, primarily in other industrial sectors.

[0003] Biaxial stretching is the most widely used process in plastic film production. It offers numerous advantages, including improved optical properties, barrier properties, heat and cold resistance, and film tensile strength, as well as high production efficiency and capacity. The biaxial stretching process orderly arranges molecules and molecular chains, improving the properties of the stretched plastic film. Among existing PET tackifying polyester masterbatch technologies, invention patent CN 106905668 A discloses a PET tackifying polyester masterbatch and tackifying process. The tackifying polyester masterbatch primarily comprises: 90-99% of the polyester masterbatch to be tackified, 0.5-7% of polyester powder, 0.1-2.5% of a chain extender, and 0.1-2.5% of an antioxidant. While this increases the viscosity of the PET masterbatch, excessively high processing temperatures can cause hydrolysis or thermal decomposition of the ester groups in the PET resin, generating gas that can cause voids and cracks in the masterbatch or film. Summary of the Invention

[0004] To address the problem of decreased thermal stability and toughness during processing of existing PET masterbatches, one objective of the present invention is to significantly increase the molecular weight of PET, enhance its initial tensile strength, and improve its toughness. However, excessive PMDA can deteriorate PET's toughness. While an appropriate amount of PMDA can significantly increase PET's molecular weight, the resulting sample also has a lower end carboxyl content. However, excessive PMDA can cause a rapid decrease in PET molecular weight and a significant increase in end carboxyl content in PET / PMDA blends. An appropriate amount of PMDA can inhibit thermal degradation of PET at high temperatures, minimizing the degradation effect of elevated temperatures. However, excessive PMDA can lead to acid hydrolysis at high temperatures, resulting in faster degradation of PET at higher temperatures. Blending PMDA with PET can alter the original linear structure of PET, causing branching, disrupting the regularity of the molecular chain, and reducing crystallization properties. While the glass transition temperature of PET is largely unaffected, the melting point is reduced.

[0005] Another object of the present invention is to add EEA (ethylene-ethyl acrylate copolymer) to PET by melt blending for toughening and modification. EEA resins are among the toughest and most flexible polyolefins, enabling them to impart exceptional toughness and flexibility to PET with high grit, thereby achieving the toughness required for biaxially stretched films.

[0006] Another object of the present invention is to improve the existing technology for solving the problem that the PET processing process has high temperature control requirements and easily leads to thermal degradation of PET; solve the problem that the tensile properties of PET are reduced after thermal degradation, and the film surface is uneven and rough frosted texture; and effectively reduce the crystal points of the film.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A white masterbatch specifically designed for high-thermal stability and high-toughness polyester films for biaxial stretching, comprising the following raw materials: PET, PMDA, and EEA.

[0008] A white masterbatch specially used for BOPET biaxially oriented polyester film with good thermal stability and high toughness, comprising the following raw materials: a thermal oxidation stabilizer; the thermal oxidation stabilizer is PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride) and a toughening agent EEA (ethylene-ethyl acrylate copolymer).

[0009] PMDA (1,2,4,5-tetracarboxylic dianhydride) is an important organic chemical raw material with a wide range of applications. Its main uses are: ① as a key raw material for the synthesis of polyimide (PI), ② as a curing agent for epoxy resins, ③ as a plasticizer for PVC, and ④ as a synthesizer for phthalocyanine blue dyes and urea-formaldehyde resin stabilizers.

[0010] EEA is a thermoplastic elastomer formed by copolymerization of ethylene and ethyl acrylate. In its molecular structure, the ethyl acrylate portion provides flexibility and polarity to the copolymer, typically comprising 15-30% by weight of the polymer. Its primary products include packaging materials, medical supplies, automotive parts, wire and cable protective coverings, and construction materials.

[0011] However, the present invention adds PMDA as a thermal oxygen stabilizer and EEA as a toughening agent to PET, and the mixed reaction and processing of the three materials are difficult: ① PDMA, EEA, and PET differ in molecular structure and chemical properties, which may lead to poor compatibility between them. During processing, this incompatibility may cause interfacial delamination, peeling, or other defects.

[0012] ②PDMA and PET will react chemically, introducing long-chain branching structures into the main chain of the PET molecule, rapidly increasing the molecular weight of PET and increasing the viscosity of the melt. The dosage must be precisely controlled to control the degree of reaction.

[0013] PET is prone to decomposition at high temperatures, with the primary decomposition products being acetaldehyde and carbon dioxide, but no toxic gases. However, PET completely decomposes at higher temperatures (approximately 300-400°C). By utilizing the thermal stability of 1,2,4,5-tetracarboxylic dianhydride, this process inhibits thermal degradation during high-temperature processing of PET.

[0014] Preferably, the thermal oxidation stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride) has excellent thermal stability, and the EEA (ethylene-ethyl acrylate copolymer) has excellent toughness and flexibility, which can better enhance the viscosity of PET and improve its thermal stability.

[0015] By adding PMDA (1,2,4,5-tetracarboxylic dianhydride) and EEA (ethylene-ethyl acrylate copolymer), the PET molecular chain reacts with PMDA during the processing of PET, causing the molecular weight to increase rapidly, which not only inhibits the thermal degradation of PET at high temperatures, but also increases the intrinsic viscosity of the PET sample.

[0016] Preferably, the weight ratio of the PET, the PMDA, and the EEA is 25-35:0.1-1.0:25-35.

[0017] When the PET (polyethylene terephthalate) content is within the range of 25-35%, the PMDA content is 0.1-1.0%, and the EEA content is 25-35%, the intrinsic viscosity of the PET sample can be maintained at an upward stage. Adding too much PMDA or no PMDA at all will cause the intrinsic viscosity of the PET (polyethylene terephthalate) to decrease. This will accelerate the thermal degradation of the PET during temperature rise, causing a rapid decrease in molecular weight, a reduction in tensile strength, poor dispersion, and the formation of crystal points.

[0018] Preferably, the following raw materials are also included: antioxidant, nucleating agent, and colorant.

[0019] Preferably, the following raw materials are included in weight percentage: PET: 25~35% PMDA: 0.1~1.0% The EEA: 25~35% The antioxidant: 0.1~1.0% The nucleating agent: 5~10% The colorant: 30~40%.

[0020] Preferably, the antioxidant includes one or more of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris[2,4-di-tert-butylphenyl]phosphite, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the nucleating agent includes one or more of light calcium carbonate powder, talc, silicon dioxide, and magnesium oxide; and the colorant includes titanium dioxide.

[0021] Preferably, the colorant comprises rutile titanium dioxide A method for preparing the above-mentioned white masterbatch for high thermal stability and high toughness polyester film for biaxial stretching comprises the following steps: S1. Weigh the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant separately for later use; put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), antioxidant, nucleating agent, and colorant into corresponding hoppers respectively; S2, then mixing the PET, the PMDA, the antioxidant, the nucleating agent, and the colorant and performing banburying to obtain a melt; S3, then adding the EEA to the melt, continuing to mix and shape, to obtain a molded body; Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer, mix them until they are mixed and melted, then add EEA (ethylene-ethyl acrylate copolymer), mix them thoroughly and mix them into shape; S4, then extruding the formed body to obtain an extruded material; S5, then granulating the extruded material to obtain particles; S6. Then, the particles are dehydrated and sieved to obtain the white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching.

[0022] After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0023] Preferably, in step S1, the PET, the PMDA, the EEA, the antioxidant, the nucleating agent, and the colorant are weighed separately and placed in different hoppers for standby use; in step S2, the temperature of the banburying is 250~270°C, and the rotation speed is 60~80r / min; in step S3, the temperature of the banburying molding is 250~270°C, and the rotation speed is 40~60r / min; in step S4, the temperature of the extrusion is 255~275°C, and the rotation speed is 65~75r / min; in step S5, the granulation method includes underwater ring cutting granulation, and the water temperature of the water ring cutting is controlled at 50~65°C; in step S6, the particle size of the white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching is 45~60 pieces / g.

[0024] Preferably, in step S1, the weighing method includes weighing using a loss-in-weight scale, and adding the feed in the required proportion using the loss-in-weight scale; steps S2 and S3 are carried out in an internal mixer, and the materials are fed into the internal mixer in steps, and are sheared and mixed in the internal mixing chamber step by step before entering the extruder; in step S4, the extrusion is carried out in the extruder; in step S5, the water temperature of the underwater ring cutting for granulation is 50~65℃; in step S6, the screening method includes a vibrating screen.

[0025] It is extruded through an extruder and granulated by underwater extrusion ring cutting. After dehydration and vibration screening, large and small particles are removed and the particle size is controlled to 45~60 pieces / g.

[0026] Preferably, in step S4, the extruder includes a twin-screw extruder.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. PMDA (1,2,4,5-tetracarboxylic dianhydride) thermal stabilizer utilizes PMDA's excellent thermal stability and reacts with PET molecular chains, rapidly increasing the molecular weight during processing. This reaction inhibits thermal degradation at high temperatures, increasing the intrinsic viscosity of the PET sample and improving its thermal stability. When the PET polyethylene terephthalate content is between 25-35% and the PMDA content is between 0.1-1.0%, the intrinsic viscosity of the PET sample increases, resulting in increased viscosity and enhanced thermal stability. At this point, the addition of EEA (ethylene ethyl acrylate copolymer) to the melt blend increases the toughness and flexibility of the PET. Furthermore, PMDA provides a certain degree of thermal stability protection for the EEA. The synergistic effect of these three factors results in a white masterbatch with easy dispersion and high toughness. This allows for excellent dispersibility in the production of biaxially oriented polyester film, resulting in a low crystallization point, high toughness, and flexibility.

[0028] 2. The present invention only requires the addition of a small amount of PMDA (1,2,4,5-tetracarboxylic dianhydride) (0.1-1.0%) during the production of masterbatches, and only requires the addition of 30-50% of masterbatches during the production of films to achieve good thermal stability and enhance film toughness, thereby reducing the use of other stabilizers and lowering film production costs. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to specific embodiments.

[0030] Example 1 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 9.8%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0031] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0032] Example 2 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.5%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 9.4%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0033] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0034] Example 3 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 8.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0035] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0036] Example 4 PET polyethylene terephthalate: 30%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.8%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.8%; Nucleating agent (light calcium carbonate powder): 8.4%; Colorant (R-type titanium dioxide): 35%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0037] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0038] Example 5 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 35%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.6%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 1%; Nucleating agent (light calcium carbonate powder): 6.4%; Colorant (R-type titanium dioxide): 32%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0039] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0040] Example 6 PET polyethylene terephthalate: 35%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.8%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 1%; Nucleating agent (light calcium carbonate powder): 8.2%; Colorant (R-type titanium dioxide): 30%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0041] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0042] Comparative Example 1 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 9.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0043] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0044] Comparative Example 2 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 2%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 7.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0045] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0046] Comparative Example 3 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 3%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 6.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0047] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0048] Comparative Example 4 PET polyethylene terephthalate: 50%; EEA ethylene-ethyl acrylate copolymer: 0%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 8.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0049] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0050] Comparative Example 5 PET polyethylene terephthalate: 40%; EEA ethylene-ethyl acrylate copolymer: 10%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 8.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0051] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0052] Comparative Example 6 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 8.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 280℃; The temperature of the extruder zone 1 is 270°C, the temperature of the zone 2 is 275°C, the temperature of the zone 3 is 280°C, the temperature of the zone 4 is 280°C, and the temperature of the zone 5 is 285°C.

[0053] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0054] Comparative Example 7 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 8.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 290℃; The temperature of the extruder zone 1 is 280°C, the temperature of the zone 2 is 285°C, the temperature of the zone 3 is 290°C, the temperature of the zone 4 is 290°C, and the temperature of the zone 5 is 295°C.

[0055] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0056] Comparative Example 8 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 9.9%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 290℃; The temperature of the extruder zone 1 is 280°C, the temperature of the zone 2 is 285°C, the temperature of the zone 3 is 290°C, the temperature of the zone 4 is 290°C, and the temperature of the zone 5 is 295°C.

[0057] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh polyethylene terephthalate, 1,2,4,5-isobutylene tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant separately and put them into internal mixer. Mix them until they are mixed and melted. Then add EEA (ethylene-ethyl acrylate copolymer) and mix them thoroughly and mix them into the internal mixer. C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0058] Comparative Example 9 PET polyethylene terephthalate: 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Thermal stabilizer (PMDA 1,2,4,5-tetracarboxylic dianhydride): 0.1%; Antioxidant (tris[2,4-di-tert-butylphenyl]phosphite): 0.1%; Nucleating agent (light calcium carbonate powder): 9.8%; Colorant (R-type titanium dioxide): 40%; Internal mixer temperature 260℃; The temperature of the extruder zone 1 is 250°C, the temperature of the zone 2 is 255°C, the temperature of the zone 3 is 260°C, the temperature of the zone 4 is 260°C, and the temperature of the zone 5 is 265°C.

[0059] A. Put the polyethylene terephthalate, the thermo-oxidative stabilizer PMDA (1,2,4,5-homogeneous tetracarboxylic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant into corresponding hoppers respectively; B. Weigh all the raw materials according to the proportion and put them into the internal mixer at the same time for mixing and internal mixing; C. After extrusion granulation, screening, and fine dehydration, the white masterbatch specially used for BOPET biaxially oriented polyester film is obtained.

[0060] Effect Example 1 The polyester masterbatches prepared in Examples 1 to 5 and the polyester masterbatches prepared in Comparative Examples 1, 2, and 3 were subjected to DSC cold crystallization temperature tests, and the masterbatches prepared above were subjected to biaxial stretching by casting with an internal addition of 30%. The dispersibility of the film was tested, and film samples with a width of 15 mm and a thickness of 25 c were made to test the tensile strength. The quality of the film was analyzed to compare the effect of adding PMDA thermal stabilizer on the performance of the polyester masterbatch. The comparative data are shown in Table 1.

[0061] Table 1 Effect of adding different proportions of PMDA thermal oxidation stabilizer on polyester masterbatch

[0062] The data in Table 1 show that the addition of an appropriate amount of PMDA in Examples 1-5 increases the cooling crystallization temperature (Tc) of PET. This indicates that the addition of PMDA alters the original linear structure of PET, partially branching it, disrupting the regularity of the molecular chain and reducing crystallinity. This leads to a decrease in the tensile strength of the film, affecting its toughness. Further increasing the amount of PMDA increases the viscosity of PET, but also accelerates hydrolysis within the system. Furthermore, higher temperatures lead to more severe thermal degradation within the system. The appropriate addition of PMDA increases the thermal stability of PET, thereby significantly improving the dispersibility of the polyester masterbatch. However, increasing the amount of PMDA can actually impair its dispersibility.

[0063] Effect Example 2 The polyester masterbatch prepared in Example 3 and the polyester masterbatch prepared in Comparative Examples 4 and 5 were subjected to DSC cold crystallization temperature test, and the masterbatch prepared above was added with 30% internally for biaxial stretching, the dispersion of the film was tested, and the tensile strength of film samples with a width of 15 mm and a thickness of 25 cm was tested. The quality of the film was analyzed to compare the effect of adding toughening agent EEA on the performance of the polyester masterbatch. The comparative data are shown in Table 2.

[0064] Table 2 Effect of adding different proportions of toughening agent EEA on polyester masterbatch

[0065] As can be seen from the data in Table 2, after adding different proportions of the toughening agent EEA to Example 3 and Comparative Examples 4 and 5, the toughness and flexibility of the films changed significantly. According to Effect Example 2, it can be seen that EEA affects the tensile properties and cold crystallization temperature of polyester. By changing the addition ratio of EEA, the toughness of the film can be increased while maintaining the thermal stability of PET, thereby achieving the toughness and flexibility required for biaxial stretching.

[0066] Effect Example 3 The polyester masterbatch prepared in Example 3 and the polyester masterbatch prepared in Comparative Examples 6 and 7 were subjected to DSC cold crystallization temperature test, and the masterbatch prepared above was added with 30% internally for biaxial stretching, the dispersion of the film was tested, and the tensile strength of the film sample with a width of 15 mm and a thickness of 25 cm was tested. The quality of the film was analyzed to compare the effects of different processing temperatures on the performance of the polyester masterbatch. The comparative data are shown in Table 3.

[0067] Table 3 Effect of different processing temperatures on polyester masterbatch

[0068] As can be seen from the data in Table 3, after adding the same proportion of PMDA in Example 3 and Comparative Examples 6 and 7, the processing temperature was increased to 280°C and 290°C, respectively. It can be seen that the cold crystallization temperature of the polyester masterbatch is roughly the same, the tensile strength of the film does not change much, and the dispersibility is good, indicating that an appropriate amount of PMDA inhibits the thermal degradation of PET at high temperatures.

[0069] Effect Example 4 The polyester masterbatches prepared in Comparative Examples 1 and 8 were subjected to DSC cold crystallization temperature test, and the masterbatches prepared above were subjected to cast biaxial stretching with 30% internal addition to test the dispersibility of the film, and film samples with a width of 15 mm and a thickness of 25 c were made to test the tensile strength. The quality of the film was analyzed to compare the effects of different processing temperatures on the performance of the polyester masterbatch. The comparative data are shown in Table 4.

[0070] Table 4 Changes of PET at different temperatures without adding PMDA

[0071] From the data in Table 4, it can be seen that when comparing Comparative Examples 1 and 8, no PMDA thermal stabilizer was added, the cold crystallization temperature and film tensile strength decreased significantly, and the dispersibility was poor, which indicates that high temperature accelerated the degree of hydrolysis and thermal degradation in the PET system.

[0072] Effect Example 5 The polyester masterbatch prepared in Example 1 and the polyester masterbatch prepared in Comparative Example 9 were subjected to DSC cold crystallization temperature test, and the masterbatch prepared above was subjected to cast biaxial stretching with 30% internal addition, the dispersibility of the film was tested, and the tensile strength of the film sample with a width of 15 mm and a thickness of 25 cm was tested. The quality of the film was analyzed to compare the effects of different processing temperatures on the performance of the polyester masterbatch. The comparative data are shown in Table 5.

[0073] Table 5 Effects of different mixing steps on polyester masterbatch

[0074] From the data in Table 5, it can be seen that the formulation systems of Example 1 and Comparative Example 9 are the same, but the banburying steps are different, and the tensile strength and dispersibility of the films vary significantly. According to Effect Example 5, it can be seen that since the melting point of EEA is between 80 and 110°C, it is not suitable for long-term banburying and shearing at high temperatures and is easily decomposed, resulting in serious loss of the mechanical properties of the material. Therefore, the step-by-step banburying method in which EEA is added last is very helpful for the dispersibility of the entire formulation system.

[0075] In summary, the polyester masterbatch of the present invention obtains the toughness and flexibility required for biaxial stretching of polyester by adding different addition ratios of heat stabilizer PMDA (1,2,4,5-tetracarboxylic dianhydride) and toughening agent EEA (ethylene-ethyl acrylate copolymer) to PET, making it easy to control the processing temperature, maintain stable PET polyester properties, and produce thinner films by biaxial stretching.

[0076] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A white masterbatch for high thermal stability and high toughness polyester film used in biaxial stretching, characterized in that: Including the following raw materials: PET, PMDA, EEA.

2. The white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching according to claim 1, characterized in that: The weight ratio of the PET, the PMDA, and the EEA is 25-35:0.1-1.0:25-35.

3. The white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching according to claim 1, characterized in that: It also includes the following raw materials: antioxidant, nucleating agent, and colorant.

4. The white masterbatch for high thermal stability and high toughness polyester film for biaxial stretching according to claim 3, characterized in that: The raw materials include the following weight percentages: PET: 25~35% PMDA: 0.1~1.0% The EEA: 25~35% The antioxidant: 0.1~1.0% The nucleating agent: 5~10% The colorant: 30~40%.

5. The white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching according to claim 3, characterized in that: The antioxidant includes one or more of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris[2,4-di-tert-butylphenyl]phosphite, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the nucleating agent includes one or more of light calcium carbonate powder, talc, silicon dioxide, and magnesium oxide; and the colorant includes titanium dioxide.

6. The white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching according to claim 3, characterized in that: The colorant includes rutile titanium dioxide.

7. A method for preparing a white masterbatch for high thermal stability and high toughness polyester film for biaxial stretching according to claim 3, characterized in that: The steps include: S1. Weigh the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant separately for later use; S2, then mixing the PET, the PMDA, the antioxidant, the nucleating agent, and the colorant and performing banburying to obtain a melt; S3, then adding the EEA to the melt, continuing to mix and shape, to obtain a molded body; S4, then extruding the formed body to obtain an extruded material; S5, then granulating the extruded material to obtain particles; S6. Then, the particles are dehydrated and sieved to obtain the white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching.

8. The preparation method according to claim 7, characterized in that: In step S1, the PET, the PMDA, the EEA, the antioxidant, the nucleating agent, and the colorant are weighed separately and placed in different hoppers for standby use; in step S2, the temperature of the banburying is 250-270°C, and the rotation speed is 60-80 r / min; in step S3, the temperature of the banburying molding is 250-270°C, and the rotation speed is 40-60 r / min; in step S4, the temperature of the extrusion is 255-275°C, and the rotation speed is 65-75 r / min; in step S5, the granulation method includes underwater ring cutting granulation; in step S6, the particle size of the white masterbatch for high thermal stability and high toughness polyester film used for biaxial stretching is 45-60 pieces / g.

9. The preparation method according to claim 7, characterized in that: In step S1, the weighing method includes weighing using a loss-in-weight scale; steps S2 and S3 are performed in an internal mixer; in step S4, the extrusion is performed in an extruder; in step S5, the water temperature of the underwater ring cutting for granulation is 50-65°C; in step S6, the screening method includes a vibrating screen.

10. The preparation method according to claim 7, characterized in that: In step S4, the extruder includes a twin-screw extruder.

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