A high-thermal-stability, high-toughness white master batch for polyester film special for bidirectional stretching and a preparation method thereof

Abstract

The application relates to a high-thermal-stability high-toughness white master batch special for polyester film and a preparation method thereof, which is applied to bidirectional stretching and comprises the following raw materials: PET, PMDA and EEA. The application is used for solving the problems that the PET processing process requires high temperature control and is prone to cause PET thermal degradation, solving the problems of the reduced tensile property, the uneven and rough frosted texture of the film surface caused by the PET thermal degradation and effectively reducing the crystal points of the film.

Description

Technical Field

[0001] This invention belongs to the field of waste recycling technology, specifically relating to a white masterbatch for biaxially oriented polyester film with high thermal stability and high toughness, and its preparation method. Background Technology

[0002] BOPET film, due to its excellent properties, is widely used in packaging for cigarettes, audio-visual products, food, etc., as well as in bag making, adhesive tape, metal coating, packaging materials, card protectors, photographic film, hot stamping foil, capacitor film, anti-counterfeiting, signage, tear strips, tapes, special electrical appliances, films, X-ray films, and electrical insulation. Based on film thickness, it is divided into ultra-thin film, thin film, medium film, and thick film. Thin and medium films are generally referred to as general-purpose films, with a thickness typically between 6 and 65 μm, mainly used in packaging. Ultra-thin and thick films are used as specialty films, primarily in other industrial fields.

[0003] Biaxial stretching is the most widely used process in plastic film production, offering numerous advantages such as improved optical properties, enhanced barrier properties, improved heat and cold resistance, increased tensile strength, high production efficiency, and large capacity. The biaxial stretching process improves the performance of the stretched plastic film by arranging molecules and molecular chains in an orderly manner. Among existing PET tackifying polyester masterbatch technologies, invention patent CN 106905668 A discloses a PET tackifying polyester masterbatch and tackifying process. This tackifying polyester masterbatch mainly comprises: 90-99% tackifying polyester masterbatch, 0.5-7% polyester powder, 0.1-2.5% chain extender, and 0.1-2.5% antioxidant. Although this increases the viscosity of the PET polyester masterbatch, excessively high processing temperatures can lead to hydrolysis or thermal decomposition of the ester groups in the PET resin, generating gas that causes voids or holes in the masterbatch or film. Summary of the Invention

[0004] To address the decline in thermal stability and toughness of existing PET masterbatches during processing, one objective of this invention is that an appropriate amount of PMDA can significantly increase the molecular weight of PET, thereby increasing its initial tensile strength and improving its toughness. However, excessive PMDA will worsen the toughness of PET. An appropriate amount of PMDA can significantly increase the molecular weight of PET, while also resulting in samples with lower end-carboxyl group content. However, excessive PMDA will cause a rapid decrease in the molecular weight of PET and a significant increase in the end-carboxyl group content in the PET / PMDA blend system. An appropriate amount of PMDA can inhibit the thermal degradation of PET at high temperatures, with minimal difference in degradation due to temperature increases. However, excessive PMDA will undergo acid hydrolysis at high temperatures, with higher temperatures accelerating PET degradation. Blending PMDA with PET alters the original linear chain structure of PET, causing branching, disrupting the regularity of the molecular chain, and reducing crystallinity. The glass transition temperature of PET is essentially unaffected, but the melting point will decrease.

[0005] Another objective of this invention is to incorporate EEA (ethylene-ethyl acrylate copolymer) into PET for toughening modification. Ethyl acrylate resins are among the most tough and flexible polyolefins, enabling high-strength PET to possess extraordinary toughness and flexibility, thereby achieving the toughness requirements for biaxial stretching of films.

[0006] Another objective of this invention is to improve upon existing technologies that address the high temperature control requirements during PET processing, which can easily lead to PET thermal degradation; to resolve the reduced tensile strength, uneven film surface, and rough frosted texture resulting from PET thermal degradation; and to effectively reduce the number of crystal points in the film.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A white masterbatch for biaxially oriented polyester film with high thermal stability and high toughness, comprising the following raw materials: PET, PMDA, and EEA.

[0008] A white masterbatch for use in BOPET biaxially oriented polyester films with good thermal stability and high toughness comprises the following raw materials: a heat-oxidation stabilizer; wherein the heat-oxidation stabilizer is PMDA (1,2,4,5-pyramidal dianhydride) and a toughening agent EEA (ethylene-ethyl acrylate copolymer).

[0009] PMDA (1,2,4,5-pyromellitic dianhydride) is an important organic chemical raw material with a wide range of applications. Its main uses are: ① 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 stabilizer for the synthesis of phthalocyanine blue dye and urea-formaldehyde resin.

[0010] EEA is a thermoplastic elastomer copolymerized from ethylene and ethyl acrylate. In its molecular structure, the ethyl acrylate moiety provides flexibility and polarity to the copolymer, typically comprising 15-30% (wt) of the polymer. Its main products include packaging materials, medical supplies, automotive parts, wire and cable protective sheaths, and building materials.

[0011] This invention incorporates PMDA as a thermo-oxidative stabilizer and EEA as a toughening agent into PET, but the mixing and processing of these three materials presents significant challenges. 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 undergo a chemical reaction, introducing long-chain branched structures into the main chain of PET molecules, which rapidly increases the molecular weight of PET and increases the viscosity of the melt. The amount used needs to be precisely controlled to control the degree of reaction.

[0013] PET is prone to decomposition under high-temperature conditions. The main decomposition products are acetaldehyde and carbon dioxide, which do not produce toxic gases. PET will completely decompose at relatively high temperatures (approximately 300-400℃). The thermal stability of 1,2,4,5-pyromellitic dianhydride is utilized to inhibit thermal degradation of PET during high-temperature processing.

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

[0015] By adding PMDA (1,2,4,5-pyridoxane dianhydride) and EEA (ethylene-ethyl acrylate copolymer), the molecular chains of PET react with PMDA during processing, causing the molecular weight of PET to increase rapidly. This 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 PET, PMDA, and EEA is 25~35:0.1~1.0:25~35.

[0017] When the proportion of polyethylene terephthalate (PET) is 25-35%, PMDA (1,2,4,5-myricetic dianhydride) is 0.1-1.0%, and EEA (ethylene-ethyl acrylate copolymer) is within the range of 25-35%, the intrinsic viscosity of the PET sample is in an upward phase. Adding too much PMDA or not adding any at all will cause the intrinsic viscosity of the PET to decrease. This leads to accelerated thermal degradation of PET during temperature increases, a rapid decrease in molecular weight, and also affects the tensile strength of PET, resulting in poor dispersibility and the formation of crystal points.

[0018] Preferably, the ingredients also include the following: antioxidants, nucleating agents, and colorants.

[0019] Preferably, the raw materials include the following weight percentages: The PET content is 25-35%. PMDA: 0.1~1.0% The EEA content is 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 biaxially oriented, high-thermal-stability, high-toughness polyester film includes the following steps: S1. Weigh the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant separately and set aside; add the polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), antioxidant, nucleating agent, and colorant to the corresponding hoppers respectively; S2. Then, the PET, PMDA, antioxidant, nucleating agent, and colorant are mixed and kneaded to obtain a melt. S3. Then, the EEA is added to the melt, and the mixture is continuously kneaded and shaped to obtain a molded body. Polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent, and colorant are weighed and fed into an internal mixer. The mixture is then mixed and melted. EEA (ethylene-ethyl acrylate copolymer) is then added and thoroughly mixed and mixed to form the final product. S4. The molded body is then extruded to obtain extruded material; S5. The extruded material is then granulated to obtain particles; S6. The particles are then dehydrated and sieved to obtain the white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film.

[0022] After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

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

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

[0025] The particles are extruded using an extruder and granulated by underwater extrusion ring cutting. After dehydration, they are vibrated and screened to remove large and small particles, controlling the particle size to 45~60 particles / g.

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

[0027] Compared with the prior art, implementing the present invention has the following beneficial effects: 1. PMDA 1,2,4,5-Hyperpyridine dianhydride heat stabilizer is used. PMDA has good thermal stability and can react with PET molecular chains, causing a rapid increase in molecular weight during PET processing. This inhibits thermal degradation of PET at high temperatures, increasing the intrinsic viscosity of the PET sample and thus improving its thermal stability. When the proportion of PET (polyethylene terephthalate) is 25-35% and the proportion of PMDA 1,2,4,5-Hyperpyridine dianhydride is 0.1-1.0%, the intrinsic viscosity of the PET sample is in an upward phase due to increased viscosity and enhanced thermal stability. At this point, EEA (ethylene-ethyl acrylate copolymer) is added and melt-blended with PET, increasing the toughness and flexibility of PET. Simultaneously, PMDA also provides some thermal stability protection for EEA. The synergistic effect of these three agents gives the white masterbatch characteristics such as easy dispersibility and high toughness, resulting in good dispersibility, low crystal point, high toughness, and flexibility when producing biaxially oriented polyester films.

[0028] 2. In the process of producing masterbatch, only a small amount of PMDA (1,2,4,5-pyramidal dianhydride) of 0.1-1.0% needs to be added. In the process of producing film, only 30-50% of masterbatch needs to be added to achieve good thermal stability and enhance film toughness, thereby reducing the amount of other stabilizers used and reducing film production costs. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, 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%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0031] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0032] Example 2 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0033] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0034] Example 3 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyromellitic 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0035] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0036] Example 4 PET (Polyethylene terephthalate): 30%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0037] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0038] Example 5 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 35%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0039] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0040] Example 6 PET (Polyethylene terephthalate): 35%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0041] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0043] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0044] Comparative Example 2 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0045] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0046] Comparative Example 3 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0047] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0048] Comparative Example 4 PET (Polyethylene terephthalate): 50%; EEA ethylene-ethyl acrylate copolymer: 0%; Heat stabilizer (PMDA 1,2,4,5-pyromellitic 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0049] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0050] Comparative Example 5 PET (Polyethylene terephthalate): 40%; EEA ethylene-ethyl acrylate copolymer: 10%; Heat stabilizer (PMDA 1,2,4,5-pyromellitic 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0051] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0052] Comparative Example 6 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyromellitic 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 extruder temperature is 270℃ in zone 1, 275℃ in zone 2, 280℃ in zone 3, 280℃ in zone 4, and 285℃ in zone 5.

[0053] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0054] Comparative Example 7 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyromellitic 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 extruder temperature is 280℃ in zone 1, 285℃ in zone 2, 290℃ in zone 3, 290℃ in zone 4, and 295℃ in zone 5.

[0055] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in 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 extruder temperature is 280℃ in zone 1, 285℃ in zone 2, 290℃ in zone 3, 290℃ in zone 4, and 295℃ in zone 5.

[0057] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh and feed polyethylene terephthalate, 1,2,4,5-homogeneous tetracarboxylic dianhydride, antioxidant, nucleating agent and colorant into an internal mixer, mix until mixed and molten, then add EEA (ethylene-ethyl acrylate copolymer), mix thoroughly and mix into shape. C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0058] Comparative Example 9 PET (Polyethylene terephthalate): 25%; EEA ethylene-ethyl acrylate copolymer: 25%; Heat stabilizer (PMDA 1,2,4,5-pyramidal 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 extruder temperature is 250℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, 260℃ in zone 4, and 265℃ in zone 5.

[0059] A. The polyethylene terephthalate, the heat and oxygen stabilizer PMDA (1,2,4,5-pyromellitic dianhydride), EEA (ethylene-ethyl acrylate copolymer), the antioxidant, the nucleating agent, and the colorant are respectively added into the corresponding hoppers; B. Weigh each raw material according to the proportion and put them into the internal mixer at the same time for mixing and internal mixing to form the product; C. After extrusion granulation, sieving, and fine dehydration, the white masterbatch specifically for use in BOPET biaxially oriented polyester film is obtained.

[0060] Example of effect 1 The polyester masterbatches prepared in Examples 1-5 and the polyester masterbatches prepared in Comparative Examples 1, 2, and 3 were subjected to DSC cold crystallization temperature tests. The masterbatches prepared above were then cast and biaxially stretched with an internal addition of 30% to test the dispersibility of the film. Film samples with a width of 15 mm and a thickness of 25 cm were prepared and tested for tensile strength. The quality of the film was analyzed to compare the effect of adding PMDA thermo-oxidative stabilizer on the performance of the polyester masterbatches. The comparative data are shown in Table 1.

[0061] Table 1. Effects of adding different proportions of PMDA thermo-oxidative stabilizer on polyester masterbatch

[0062] As shown in Table 1, the addition of appropriate amounts of PMDA in Examples 1-5 increased the cooling crystallization temperature (Tc) of PET. This indicates that the addition of PMDA altered the original linear structure of PET, causing partial branching, disrupting the regularity of the molecular chains, and reducing crystallinity. Consequently, the tensile strength of the film decreased, affecting its toughness. While increasing the amount of PMDA increased the viscosity of PET, it also accelerated the hydrolysis within the system. Furthermore, higher temperatures resulted in more severe thermal degradation within the system. Appropriate addition of a certain proportion of PMDA increased the thermal stability of PET, thereby improving the dispersibility of the polyester masterbatch. However, increasing the amount of PMDA negatively impacted its dispersibility.

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

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

[0065] As can be seen from the data in Table 2, the toughness and flexibility of the film changed significantly after adding different proportions of toughening agent EEA in Examples 3 and Comparative Examples 4 and 5. According to Example 2, EEA can affect the tensile properties and cold crystallization temperature of polyester. By changing the proportion of EEA added, the toughness of the film can be increased without changing the thermal stability of PET, thereby achieving the toughness and flexibility required for biaxial stretching.

[0066] Example 3 The polyester masterbatch prepared in Example 3 and the polyester masterbatches prepared in Comparative Examples 6 and 7 were subjected to DSC cold crystallization temperature test. The masterbatch prepared above was added with 30% internally and then cast and biaxially stretched to test the film dispersibility. Film samples with a width of 15 mm and a thickness of 25 cm were made and tested for tensile strength. The quality of the film was analyzed to compare the effect of different processing temperatures on the performance of 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 Examples 3 and Comparative Examples 6 and 7, the processing temperature was increased to 280℃ and 290℃, respectively. This indicates that the cold crystallization temperature of the polyester masterbatch was roughly the same, and the tensile strength of the film did not change significantly, indicating good dispersibility. This suggests that an appropriate amount of PMDA inhibited the thermal degradation of PET at high temperatures.

[0069] Example 4 The polyester masterbatches prepared in Comparative Examples 1 and 8 were subjected to DSC cold crystallization temperature testing. The masterbatches prepared above were then cast and biaxially stretched with an internal addition of 30% to test the film dispersibility. Film samples with a width of 15 mm and a thickness of 25 cm were prepared and tested for tensile strength. The quality of the film was analyzed to compare the effects of different processing temperatures on the performance of the polyester masterbatches. The comparative data are shown in Table 4.

[0070] Table 4. Changes in PET at different temperatures without PMDA addition

[0071] As can be seen from the data in Table 4, compared with Comparative Examples 1 and 8, without the addition of PMDA heat stabilizer, the cold crystallization temperature and tensile strength of the film are significantly reduced, and the dispersibility is poor. This indicates that high temperature accelerates the degree of hydrolysis and thermal degradation in the PET system.

[0072] 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. The masterbatch prepared above was added with 30% internally and then cast and biaxially stretched to test the film dispersibility. Film samples with a width of 15 mm and a thickness of 25 cm were made and tested for tensile strength. The quality of the film was analyzed to compare the effect of different processing temperatures on the performance of polyester masterbatch. The comparative data are shown in Table 5.

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

[0074] As can be seen from the data in Table 5, although the formulation systems of Example 1 and Comparative Example 9 are the same, the mixing steps are different, and the tensile strength and dispersibility of the film are significantly different. According to the effect example 5, since the melting point of EEA is between 80 and 110°C, it is not suitable for long-term mixing and shearing at high temperatures, as it is easy to decompose and cause serious loss of material mechanical properties. Therefore, the stepwise mixing method with EEA added last greatly helps the dispersibility of the entire formulation system.

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

[0076] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A white masterbatch for use in biaxially oriented polyester films with high thermal stability and high toughness, characterized in that, It includes the following raw materials: PET, PMDA, and EEA; it also includes the following raw materials: antioxidant, nucleating agent, and colorant; the weight ratio of PET, PMDA, and EEA is 25~35:0.1~1.0:25~35; The preparation of the white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film includes the following steps: S1. Weigh the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant separately for later use; S2. Then, the PET, PMDA, antioxidant, nucleating agent, and colorant are mixed and kneaded to obtain a melt. S3. Then, the EEA is added to the melt, and the mixture is continuously kneaded and shaped to obtain a molded body. S4. The molded body is then extruded to obtain extruded material; S5. The extruded material is then granulated to obtain particles; S6. The particles are then dehydrated and sieved to obtain the white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film.

2. The white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film as described in claim 1, characterized in that, The raw materials include the following weight percentages: The PET content is 25-35%. PMDA: 0.1~1.0% The EEA content is 25-35%. The antioxidant: 0.1~1.0% The nucleating agent: 5-10% The colorant: 30~40%.

3. The white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film as described in claim 1, 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.

4. The white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film as described in claim 1, characterized in that, The colorant includes rutile titanium dioxide.

5. A method for preparing a white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film according to claim 1, characterized in that, Includes the following steps: S1. Weigh the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant separately for later use; S2. Then, the PET, PMDA, antioxidant, nucleating agent, and colorant are mixed and kneaded to obtain a melt. S3. Then, the EEA is added to the melt, and the mixture is continuously kneaded and shaped to obtain a molded body. S4. The molded body is then extruded to obtain extruded material; S5. The extruded material is then granulated to obtain particles; S6. The particles are then dehydrated and sieved to obtain the white masterbatch for biaxially oriented, high-thermal-stability, high-toughness polyester film.

6. The preparation method according to claim 5, characterized in that, In step S1, the PET, PMDA, EEA, antioxidant, nucleating agent, and colorant are weighed and stored in different hoppers for later use; in step S2, the mixing temperature is 250~270℃ and the rotation speed is 60~80 r / min; in step S3, the mixing molding temperature is 250~270℃ and the rotation speed is 40~60 r / min; in step S4, the extrusion temperature is 255~275℃ 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 applied to biaxial stretching is 45~60 particles / g.

7. The preparation method according to claim 5, characterized in that, In step S1, the weighing method includes weighing using a loss-in-weight scale; steps S2 and S3 are carried out in an internal mixer; in step S4, the extrusion is carried out in an extruder; in step S5, the underwater ring cutting water temperature for granulation includes 50~65℃; in step S6, the sieving method includes a vibrating screen.

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

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