A pet matt base film for label and a method for preparing the same

Abstract

The application discloses a PET matte base film for labels and a preparation method thereof. The PET matte base film is composed of terephthalic acid, ethylene glycol, a catalyst, tetraethoxysilane, 1,4-cyclohexane dimethanol, 3-aminopropyl triethoxysilane and an antioxidant, and nano composite particles are generated in situ in a polyester esterification-polycondensation process. After the molten polyester is extruded, the film passes through a homogenizing roller and a flattening vacuum shaping device in sequence, and then is subjected to bidirectional stretching, so that a matte PET base film with uniform thickness and uniform micro-nano rough structure on the surface is obtained. The base film has low gloss, uniform matte effect, high longitudinal and transverse tensile strength, moderate breaking elongation, excellent flexibility and printing adhesion, and is suitable for adhesive labels and consumer product labels. Through composite component design and optimization of a processing process, the application effectively improves the problems of surface light spots, uneven gloss and unstable mechanical properties of the existing PET matte film for labels, realizes high balance between the matte effect and the mechanical properties, and has good industrial application value.

Description

Technical Field

[0001] This invention belongs to the technical field of polyester functional film materials, specifically relating to a self-adhesive substrate film for labels, particularly a PET base film with a matte appearance and its preparation method. This base film is suitable for label applications such as consumer product packaging, logistics barcodes, and daily chemical product identification. Background Technology

[0002] Labels are an important component of packaging and information identification, widely used in food and beverage, daily chemical products, pharmaceuticals, electronic products, and logistics management. Common self-adhesive labels typically consist of three parts: a surface material layer, an adhesive layer, and a release liner layer. The surface material layer often uses a film with certain mechanical and surface treatment properties as the substrate. With increasing demands for visual appeal and information identification in product packaging, matte films with low reflectivity and good printability are gradually becoming an important development direction for label films.

[0003] Most existing matte labels use PET as the base material. A micro-rough structure is created on the base film surface by adding fillers, controlling crystallization, or coating with matting agents. This achieves a diffuse reflection effect, reducing the gloss of the film surface, improving the scanning and recognition rate of barcodes and QR codes, and enhancing the visual contrast of printed images and text. This type of PET matte base film not only possesses the inherent high tensile strength, heat resistance, and dimensional stability of PET material, but also provides a soft appearance while maintaining transparency, making it an important choice for label films.

[0004] Despite these shortcomings, existing matte PET base films for labels still have some drawbacks. Firstly, during high-speed printing or lamination processes, maintaining a stable matte finish is often difficult, leading to uneven gloss distribution and affecting appearance consistency. Secondly, the design and control of surface roughness are often inadequate, resulting in insufficient adhesion of inks or heat transfer ribbons to the film surface, reducing printability and durability. Thirdly, some base films sacrifice mechanical properties or transparency in pursuit of a matte finish, making them prone to breakage, peeling, or insufficient transparency during die-cutting, waste removal, and labeling. Furthermore, traditional matte film preparation methods are complex, requiring strict control over filler dispersion and film-forming conditions, which not only increases production costs but also hinders large-scale product promotion and application.

[0005] Therefore, how to develop a PET matte base film for labels with a reasonable structure, stable matte effect, and excellent printability and mechanical properties, and its preparation method, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a matte PET base film for labels and a method for preparing the same, so as to reduce or avoid the problems mentioned above.

[0007] Specifically, in order to overcome the defects of existing matte PET base films for labels, such as unstable matte effect, insufficient surface printability, decreased mechanical properties, and complex preparation process, this invention proposes a matte PET base film for labels and its preparation method that can achieve stable matte effect, excellent printing adhesion, and suitability for industrial-scale production while maintaining good mechanical properties and dimensional stability.

[0008] To address the aforementioned technical problems, the overall technical solution of this invention lies in introducing a special organic-inorganic composite particle system during the PET polymerization process. This allows the particles to be generated in situ and uniformly dispersed within the polyester matrix, thereby constructing a controllable micro-nano-scale rough structure on the film surface during film forming and biaxial stretching, achieving a stable matte effect. Unlike traditional methods that rely on physically adding fillers or surface coating, this invention uses molecular design and polymerization processes to synergistically control the interfacial interaction between the particles and the matrix, enabling the matte structure to form a stable bond with the matrix layer. This not only avoids particle migration or detachment issues but also achieves long-term maintenance and consistency of matte finish, optimizing the film surface roughness distribution. Consequently, the film possesses both low gloss and excellent transparency and printability.

[0009] More specifically, to solve the above-mentioned technical problems, the present invention proposes a matte PET base film for labels, which is made from the following raw materials: 90-100 parts by weight of terephthalic acid, 100-110 parts by weight of ethylene glycol, 0.01-0.1 parts by weight of catalyst, 5-15 parts by weight of tetraethoxysilane, 2-8 parts by weight of 1,4-cyclohexanediol, 0.5-3 parts by weight of 3-aminopropyltriethoxysilane, and 0.2-1 parts by weight of antioxidant Irganox 1010; the film is processed by homogenizing rollers and flattening vacuum shaping device after melt extrusion, and then formed into a matte PET base film with uniform thickness and uniform micro-nano rough surface structure by biaxial stretching.

[0010] Preferably, the catalyst is one or a combination of p-toluenesulfonic acid and antimony oxide.

[0011] Preferably, the film thickness is 55-70 µm.

[0012] Preferably, the surface gloss is 4.5-5 GU, the longitudinal tensile strength is 180-195 MPa, the transverse tensile strength is 160-175 MPa, the longitudinal elongation at break is 110-125%, and the transverse elongation at break is 105-115%.

[0013] Preferably, the film is suitable for self-adhesive labels, consumer product labels and other printing applications.

[0014] This invention also proposes a method for preparing the above-mentioned matte PET base film for labels, comprising the following steps: mixing terephthalic acid and ethylene glycol with a catalyst for esterification; adding tetraethoxysilane, a composite particle precursor, 1,4-cyclohexanediethanol, a surface conditioner, 3-aminopropyltriethoxysilane, and an antioxidant, Irganox 1010, during the esterification or polycondensation process to generate nanocomposite particles in situ; extruding molten polyester into a film; passing the film sequentially through a homogenizing roller and a flattening vacuum shaping device; and finally performing biaxial stretching to obtain a matte PET base film for labels with uniform thickness and a uniform micro-nano rough surface structure.

[0015] Preferably, the esterification temperature is 250-280 ℃, the polycondensation temperature is 280-290 ℃, the pressure is 0.5-5 kPa, and the reaction time is 2-4 hours.

[0016] Preferably, the temperature of the homogenizing roller is controlled at 70-100 ℃, and the vacuum degree of the vacuum setting device is 50-90 kPa.

[0017] Preferably, the biaxial stretching has a transverse stretching ratio of 1.5-2.5 times, a longitudinal stretching ratio of 2.0-3.0 times, and a stretching temperature of 80-100 ℃.

[0018] Preferably, the film has a thickness of 55-70 µm after stretching, a surface gloss of 4.5-5 GU, a longitudinal tensile strength of 180-195 MPa, and a transverse tensile strength of 160-175 MPa.

[0019] The PET matte base film for labels and its preparation method provided by this invention can generate nanocomposite particles in situ during the polyester esterification-polymerization process, and rationally add flexible modifiers, surface conditioners, and antioxidants. Combined with a biaxial stretching process using a homogenizing roller and a flattening vacuum setting device, the film achieves uniform thickness and a uniform micro-nano rough surface structure, resulting in an excellent matte finish. Compared with existing technologies, the film of this invention exhibits high longitudinal and transverse tensile strength, moderate elongation at break, good flexibility and scratch resistance, and stable printing adhesion, making it suitable for various applications such as self-adhesive labels and consumer product labels. Through systematic optimization of raw material formulation and preparation process, the film of this invention effectively avoids problems such as surface spots, uneven gloss, and unstable mechanical properties, achieving a high balance between matte finish and mechanical properties, demonstrating significant industrial application value and promising prospects for widespread application. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail.

[0021] The matte PET base film for labels provided by this invention is prepared by introducing organic-inorganic composite particles that can be generated in situ within the polyester matrix during the esterification-polymerization process of polyethylene terephthalate (PET). Simultaneously, appropriate amounts of flexibility modifiers and surface conditioners are added, thereby forming a micro-nano-scale surface rough structure during film forming and biaxial stretching, achieving a stable matte effect. This structure not only ensures the high mechanical properties and dimensional stability of the PET substrate but also improves the film's printing adhesion and flexibility, meeting the requirements for self-adhesive labels in die-cutting, printing, and labeling processes.

[0022] In a preferred embodiment of the present invention, the PET matte base film for the label is made from the following raw materials: 90-100 parts of terephthalic acid (PTA), 100-110 parts of ethylene glycol (EG), 0.01-0.1 parts by weight of catalyst (p-toluenesulfonic acid or antimony oxide), 5-15 parts of tetraethoxysilane (TEOS), 2-8 parts of 1,4-cyclohexanediethanol (CHDM), 0.5-3 parts of 3-aminopropyltriethoxysilane (APTES), and 0.2-1 parts of antioxidant Irganox 1010 (BASF product).

[0023] In this process, terephthalic acid (PTA) and ethylene glycol (EG) are used to synthesize polyethylene terephthalate (PET) matrix in situ via esterification-condensation reaction; a catalyst, such as p-toluenesulfonic acid or antimony oxide, is used to promote PET formation; tetraethoxysilane (TEOS) serves as an organic-inorganic composite particle precursor, used for hydrolysis and condensation during polymerization to generate uniformly dispersed nanoscale particles, thereby forming a stable micro-nano rough structure on the film surface and achieving a matte effect; 1,4-cyclohexanediethanol (CHDM) acts as a flexibility modifier, used to embed flexible segments into the PET molecular chain, improving the film's flexibility and folding resistance; 3-aminopropyltriethoxysilane (APTES) acts as a surface conditioner, used to regulate the film surface polarity and wettability, thereby improving the adhesion of printing inks or thermal transfer ribbons; and the antioxidant Irganox 1010 acts as a stabilizer, used to prevent thermal degradation and color changes during polymerization and subsequent processing.

[0024] More specifically, the raw materials can preferably be sourced from the following sources: terephthalic acid (PTA) and ethylene glycol (EG) are industrial-grade pure products, which can be purchased from companies such as Yisheng Petrochemical and Hengyi Petrochemical; the composite particle precursor is preferably tetraethoxysilane (TEOS), which can be purchased from Aladdin Chemical's industrial-grade products; the flexible modifier is preferably 1,4-cyclohexanediethanol (CHDM), which can be purchased from Dongman Company; the surface conditioner is preferably 3-aminopropyltriethoxysilane (APTES), which can be purchased from Shin-Etsu Chemical; and the stabilizer is preferably Irganox 1010, which can be purchased from BASF.

[0025] Through the above formulation design, the matte PET base film for labels prepared by this invention achieves a stable matte effect by simultaneously polymerizing PET in situ and generating a micro-nano rough structure through hydrolysis and condensation of 5-15 parts by weight of composite particles. The addition of a flexibility modifier enhances the film's flexibility, the surface conditioner improves printing adhesion, and the stabilizer ensures thermal and color stability during preparation and processing. This allows the base film to maintain mechanical properties and dimensional stability while simultaneously meeting the comprehensive requirements of matte effect, printability, and industrial processing performance.

[0026] Furthermore, the method for preparing the matte PET base film for labels provided by this invention includes the following steps: First, 90-100 parts by weight of terephthalic acid (PTA) and 100-110 parts by weight of ethylene glycol (EG) are placed in an esterification reactor, and a catalyst such as p-toluenesulfonic acid or antimony oxide (0.01-0.1 parts by weight) is added. The esterification reaction is carried out at a temperature of 220-260°C, while the generated water vapor is slowly discharged. During the reaction, the stirring speed is maintained at 50-200 rpm until the acid value decreases to ≤50 mgKOH / g, indicating that the esterification is basically completed.

[0027] When esterification is nearing completion, add 5-15 parts by weight of an organic-inorganic composite particle precursor, such as tetraethoxysilane (TEOS), to the system, and maintain the temperature at 200-250℃ and the stirring speed at 100-200 rpm. This allows the composite particles to undergo in-situ hydrolysis and condensation in the PET oligomer system to generate nanoparticles. At this time, 2-8 parts by weight of a flexibility modifier, such as 1,4-cyclohexanediethanol (CHDM), can be added simultaneously to allow it to participate in copolymerization during the polycondensation reaction, thereby embedding flexible segments into the polyester molecular chain and improving the film toughness.

[0028] The above system is then subjected to a polycondensation reaction at a temperature of 270-290℃ and a pressure of 0.5-5 kPa (under vacuum) for 2-4 hours to ensure complete transesterification and generate high molecular weight PET. Simultaneously, the composite particles are uniformly dispersed within the polyester matrix. During this stage, 0.5-3 parts by weight of a surface conditioner, such as 3-aminopropyltriethoxysilane (APTES), can be added to improve film surface wettability and printing adhesion through interfacial interactions. Simultaneously, 0.2-1 parts by weight of a stabilizer, such as Irganox 1010, can be added to prevent thermal degradation during polymerization.

[0029] After polymerization, the molten polyester is extruded into a film using a single-screw or twin-screw extruder. The extrusion temperature is controlled at 260-280℃. The film then passes sequentially through a homogenizing roller and a vacuum setting device to ensure uniform thickness. The homogenizing roller temperature is controlled at 70-100℃, and the vacuum setting device maintains a vacuum level of 50-90 kPa. Subsequently, the film undergoes biaxial stretching with a transverse stretch ratio of 1.5-2.5 times and a longitudinal stretch ratio of 2.0-3.0 times. The stretching temperature is 80-100℃, and the stretching speed is controlled at 50-150 mm / s to create a stable micro-nano-scale rough structure on the film surface, achieving a uniform matte finish. After stretching, the film undergoes heat setting at 200-230℃ for 1-5 minutes to fix molecular orientation and surface structure, ensuring dimensional stability and mechanical properties.

[0030] Because the matte PET base film for labels of this invention needs to form a stable and uniform micro-nano rough structure while ensuring uniform thickness, thereby achieving excellent matte effect, good printability, and flexibility, the molten extruded film is sequentially passed through a homogenizing roller and a vacuum setting device before biaxial stretching. The homogenizing roller uses multiple sets of parallel rollers to calender and slightly shear the molten polyester, smoothing out local thickness differences. Simultaneously, heating or cooling is used to control film flowability, resulting in a uniform thickness distribution and good surface smoothness. Subsequently, the film enters the vacuum setting device, where vacuum adsorption fixes the film surface to a smooth plate, and cooling or solidifying it under slight tension. This stabilizes the molecular chain orientation and micro-nano surface structure, while eliminating bubbles or wrinkles on the film surface, further ensuring uniform film thickness and dimensional stability. This process arrangement not only ensures the formation of a uniform matte structure during subsequent biaxial stretching but also significantly improves the film's mechanical properties, printability, and repeatability in industrial production.

[0031] The PET matte base film for labels obtained by the above preparation method has 5-15 parts by weight of composite particles forming a micro-nano rough structure on the film surface, achieving a low-gloss, uniform and stable matte effect; 2-8 parts by weight of flexible modifier ensures the flexibility of the film during die-cutting, printing and labeling processes; 0.5-3 parts by weight of surface conditioner improves the adhesion of ink and ribbon; and 0.2-1 parts by weight of stabilizer ensures thermal stability and color stability during processing and film formation, ultimately resulting in a high-performance PET matte base film that can be used for self-adhesive labels or consumer product labels.

[0032] Example 1

[0033] 90 parts by weight of terephthalic acid (PTA) and 100 parts by weight of ethylene glycol (EG) were added to an esterification reactor, along with 0.01 parts by weight of p-toluenesulfonic acid and 0.01 parts by weight of antimony oxide catalysts. During esterification, the generated water vapor was slowly discharged. 5 parts by weight of tetraethoxysilane (TEOS) were added as a precursor for the composite particles, along with 2 parts by weight of the flexible modifier 1,4-cyclohexanediethanol (CHDM), 0.5 parts by weight of the surface conditioner 3-aminopropyltriethoxysilane (APTES), and 0.2 parts by weight of the antioxidant Irganox 1010. After in-situ generation of nanocomposite particles through esterification-condensation polymerization, the melt was extruded into a film, and after being homogenized by rollers and vacuum-set to fix the thickness, it was subjected to biaxial stretching. The resulting film has a thickness of 55µm, a surface gloss of about 5 GU, a longitudinal (MD) tensile strength of 180 MPa, a transverse (TD) tensile strength of 160 MPa, an elongation at break of MD 120% and TD 110%, a uniform micro-nano rough structure on the surface, and excellent printing adhesion and flexibility.

[0034] Example 2

[0035] 92 parts by weight of terephthalic acid (PTA) and 102 parts by weight of ethylene glycol (EG) were added to the esterification reactor. The catalysts used were 0.05 parts by weight of p-toluenesulfonic acid and 0.05 parts by weight of antimony oxide. During the esterification reaction, 7 parts by weight of the composite particle precursor TEOS, 3 parts by weight of the flexible modifier CHDM, 1 part by weight of the surface conditioner APTES, and 0.5 parts by weight of Irganox 1010 were added. The composite particles were generated in situ. After the melt polyester was extruded into a film, it was sequentially passed through a homogenizing roller and a vacuum setting device, and then biaxially stretched. The film thickness was 60 µm, with a gloss of approximately 4.8 GU, a maximum density (MD) of 185 MPa, a maximum tensile strength (TD) of 165 MPa, and an elongation at break (MD) of 110% and TD of 105%. The micro / nano particles were uniformly distributed, resulting in a stable matte finish and good printing adhesion.

[0036] Example 3

[0037] The method employed 95 parts by weight of PTA and 105 parts by weight of EG, 0.1 parts by weight of p-toluenesulfonic acid catalyst and 0.1 parts by weight of antimony oxide catalyst, 10 parts by weight of TEOS composite particle precursor, 5 parts by weight of CHDM flexible modifier, 2 parts by weight of APTES, and 0.8 parts by weight of Irganox 1010. Nanocomposite particles were generated in situ during the esterification-polymerization process. The resulting film was extruded, leveled by a homogenizing roller, vacuum-set to fix the thickness, and then biaxially stretched. The resulting film had a thickness of 65 µm, a gloss level of 5 GU, a tensile strength (MD) of 190 MPa and a tensile strength (TD) of 170 MPa, and an elongation at break (MD) of 125% and a TD of 115%. The film exhibited a uniform micro-nano rough structure on its surface, excellent matte uniformity, and superior flexibility.

[0038] Example 4

[0039] The composite particles were generated in situ via esterification-polymerization, consisting of 98 parts by weight of PTA, 108 parts by weight of EG, 0.01 parts by weight of p-toluenesulfonic acid catalyst, 0.1 parts by weight of antimony oxide catalyst, 12 parts by weight of TEOS composite particle precursor, 6 parts by weight of CHDM, 2.5 parts by weight of APTES, and 10101 parts by weight of Irganox. After melt extrusion into a film, the film was sequentially passed through a homogenizing roller and vacuum-set, followed by biaxial stretching. The resulting film had a thickness of 70 µm, a gloss of 4.5 GU, a maximum density (MD) of 192 MPa, a maximum tensile strength (TD) of 172 MPa, and an elongation at break (MD) of 120% and TD of 110%. The film surface exhibited a concentrated and uniform particle size distribution, stable matte finish, and excellent printability.

[0040] Example 5

[0041] The composition comprises 100 parts by weight of PTA, 110 parts by weight of EG, 0.05 parts by weight of p-toluenesulfonic acid catalyst, 0.05 parts by weight of antimony oxide catalyst, 15 parts by weight of TEOS composite particle precursor, 8 parts by weight of CHDM, 3 parts by weight of APTES, and 0.2 parts by weight of Irganox 10100. Nanocomposite particles are generated in situ, extruded into a film, homogenized by a roller, vacuum-set, and then biaxially stretched. The film thickness is 68µm, gloss is 4 GU, tensile strength (MD) is 195 MPa, tensile strength (TD) is 175 MPa, elongation at break (MD) is 118%, and elongation at break (TD) is 108%. The surface exhibits a uniform and clear micro / nano rough structure, excellent flexibility, and good print adhesion.

[0042] Example 6

[0043] The film comprises 90 parts by weight of PTA, 100 parts by weight of EG, 0.1 parts by weight of p-toluenesulfonic acid catalyst, 0.01 parts by weight of antimony oxide catalyst, 8 parts by weight of TEOS composite particle precursor, 4 parts by weight of CHDM, 1.5 parts by weight of APTES, and 0.5 parts by weight of Irganox 1010. Composite particles are generated in situ during the esterification-polymerization process. After film extrusion, the film is passed sequentially through a homogenizing roller and a flattening vacuum shaping device, followed by biaxial stretching to obtain a matte film with a thickness of 62µm, a gloss level of 5 GU, a maximum density (MD) of 188 MPa, a maximum tensile strength (TD) of 168 MPa, and an elongation at break (MD) of 120% and a TD of 110%. The surface micro- and nano-particles are uniformly distributed, and the matte uniformity, flexibility, and printability are all excellent.

[0044] Comparative Example 1.

[0045] Using 90 parts by weight of terephthalic acid (PTA), 100 parts by weight of ethylene glycol (EG), 0.01 parts by weight of p-toluenesulfonic acid catalyst, and 0.01 parts by weight of antimony oxide, only a conventional esterification-condensation reaction was carried out. No composite particle precursor TEOS, flexible modifier CHDM, surface conditioner APTES, or antioxidant Irganox 1010 were added. The film was directly biaxially stretched after extrusion. The resulting film thickness was approximately 55 µm, but the surface gloss was high (approximately 15 GU), with poor matte uniformity and obvious gloss spots on the film surface. The maximum density (MD) was 150 MPa, the maximum tensile strength (TD) was 140 MPa, and the elongation at break was MD 90% and TD 80%. The film was prone to scratches and insufficient printing adhesion.

[0046] Comparative Example 2.

[0047] The film contains 95 parts by weight of PTA, 105 parts by weight of EG, 0.05 parts by weight of p-toluenesulfonic acid catalyst, 0.05 parts by weight of antimony oxide catalyst, 7 parts by weight of TEOS catalyst, but omits the flexibility modifier CHDM and surface conditioner APTES, and 0.5 parts by weight of antioxidant Irganox 1010. After melt extrusion, it is directly biaxially stretched without homogenization rollers, leveling, or vacuum shaping. The film thickness is 60µm, gloss is approximately 10 GU, the surface micro / nano rough structure is unevenly distributed, MD strength is 160 MPa, TD strength is 145 MPa, elongation at break is MD 95%, TD 85%, and the film lacks flexibility, resulting in decreased die-cutting and printing performance.

[0048] Comparative Example 3.

[0049] The film contains 100 parts by weight of PTA, 110 parts by weight of EG, 0.1 parts by weight of p-toluenesulfonic acid catalyst, and 0.1 parts by weight of antimony oxide catalyst. The composite particles TEOS are omitted, but 5 parts by weight of CHDM, 1.5 parts by weight of APTES, and 0.8 parts by weight of Irganox 1010 are added. After extrusion, the film is biaxially stretched, but no homogenizing roller or vacuum setting treatment is performed. The film thickness is 65µm, gloss is approximately 12 GU, MD strength is 165 MPa, TD strength is 150 MPa, and elongation at break is MD 100% and TD 90%. The matte finish is poor with noticeable surface spots, and printing adhesion is reduced.

[0050] Comparative Example 4.

[0051] The film was prepared using 92 parts by weight of PTA, 102 parts by weight of EG, 0.05 parts by weight of p-toluenesulfonic acid catalyst, 0.05 parts by weight of antimony oxide catalyst, and 10 parts by weight of TEOS. However, the flexibility modifier CHDM and antioxidant Irganox 1010 were omitted. The film was directly biaxially stretched after extrusion without the use of a homogenizing roller or vacuum setting device. The film thickness was approximately 62 µm, with a gloss of 15 GU. The surface exhibited an uneven micro-nano rough structure, a maximum density (MD) of 160 MPa, a maximum tensile strength (TD) of 145 MPa, and an elongation at break of 95% for MD and 85% for TD. Flexibility and printability were significantly reduced.

[0052] Comparative Example 5.

[0053] The film contained 98 parts by weight of PTA, 108 parts by weight of EG, 0.01 parts by weight of p-toluenesulfonic acid catalyst, 0.1 parts by weight of antimony oxide, 6 parts by weight of CHDM, and 2 parts by weight of APTES. However, the composite particles TEOS and antioxidant Irganox 1010 were omitted. After extrusion, the film was directly biaxially stretched without homogenization rollers and vacuum setting. The film thickness was 68µm, gloss was approximately 13 GU, MD strength was 170 MPa, TD strength was 150 MPa, and elongation at break was MD 100% and TD 90%. The matte uniformity and printing adhesion were significantly inferior to the example.

[0054] Comparative Example 6.

[0055] The film contains 90 parts by weight of PTA, 100 parts by weight of EG, 0.1 parts by weight of p-toluenesulfonic acid catalyst, and 0.01 parts by weight of antimony oxide. The composite particles TEOS, the flexible modifier CHDM, and the surface conditioner APTES are omitted; only 0.5 parts by weight of Irganox 1010 are added. After extrusion, the film is directly biaxially stretched without passing through a homogenizing roller or vacuum setting device. The final film thickness is 62µm, gloss is approximately 16 GU, the surface matte finish is uneven, the MD strength is 155 MPa, the TD strength is 140 MPa, the elongation at break is MD 90%, and the TD strength is 80%. The film exhibits poor flexibility, and its printing adhesion and scratch resistance are significantly reduced.

[0056] A comparison of the above embodiments with the comparative embodiments shows that the PET matte base film for labels of the present invention, through in-situ generation of composite particles, reasonable addition of flexible modifiers, surface conditioners, and antioxidants, and after homogenization roller leveling and vacuum shaping treatment, can obtain a matte film with uniform thickness, stable micro-nano rough surface structure, low and uniform gloss, high tensile strength, moderate elongation at break, and excellent flexibility and printing adhesion, making it suitable for various self-adhesive and consumer product label applications. In contrast, the comparative embodiments, due to the lack of composite particles, flexible modifiers, or the omission of thickness leveling treatment, result in uneven matte surface effect, higher gloss, decreased mechanical properties, and insufficient flexibility and printing adhesion, making it difficult to meet the requirements of industrial production and high-precision label applications. This fully demonstrates the innovation, advancement, and practical value of the composite component formulation and process of the present invention.

[0057] Those skilled in the art should understand that although the present invention has been described with reference to multiple embodiments, not every embodiment contains only one independent technical solution. This description is provided merely for clarity; those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of the present invention.

[0058] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A matte PET base film for labels, characterized in that, It is made from the following raw materials: 90-100 parts by weight of terephthalic acid, 100-110 parts by weight of ethylene glycol, 0.01-0.1 parts by weight of catalyst, 5-15 parts by weight of tetraethoxysilane, 2-8 parts by weight of 1,4-cyclohexanediethanol, 0.5-3 parts by weight of 3-aminopropyltriethoxysilane, and 0.2-1 parts by weight of antioxidant Irganox 1010; the film made from the raw materials is processed by homogenizing rollers and flattening vacuum shaping device after melt extrusion, and then formed into a matte PET base film with uniform thickness and uniform micro-nano rough surface structure by biaxial stretching.

2. The matte PET base film for labels according to claim 1, characterized in that, The catalyst is one or a combination of p-toluenesulfonic acid and antimony oxide.

3. The matte PET base film for labels according to claim 1 or 2, characterized in that, The thickness of the base film is 55-70 µm.

4. The matte PET base film for labels according to any one of claims 1-3, characterized in that, The base film has a surface gloss of 4.5-5 GU, a longitudinal tensile strength of 180-195 MPa, a transverse tensile strength of 160-175 MPa, a longitudinal elongation at break of 110-125%, and a transverse elongation at break of 105-115%.

5. The matte PET base film for labels according to any one of claims 1-4, characterized in that, The base film is suitable for self-adhesive labels, consumer product labels and other printing applications.

6. A method for preparing a matte PET base film for labels, characterized in that, The process includes the following steps: mixing terephthalic acid and ethylene glycol with a catalyst for esterification; adding tetraethoxysilane, a precursor of composite particles, 1,4-cyclohexanediethanol, 3-aminopropyltriethoxysilane, a surface conditioner, and Irganox 1010, as well as antioxidants, during esterification or polycondensation to generate nanocomposite particles in situ; extruding molten polyester into a film; passing the film sequentially through a homogenizing roller and a flattening vacuum shaping device; and finally, biaxially stretching to obtain a uniform thickness and a uniform micro-nano rough surface structure for a matte PET base film for labels.

7. The method according to claim 6, characterized in that, The esterification temperature is 250-280 ℃, the polycondensation temperature is 280-290 ℃, the pressure is 0.5-5 kPa, and the reaction time is 2-4 hours.

8. The method according to claim 6 or 7, characterized in that, The temperature of the homogenizing roller is controlled at 70-100 ℃, and the vacuum degree of the vacuum setting device is 50-90 kPa.

9. The method according to any one of claims 6-8, characterized in that, Biaxial tensile strength has a transverse tensile ratio of 1.5-2.5 times and a longitudinal tensile ratio of 2.0-3.0 times, with a tensile temperature of 80-100 ℃.

10. The method according to any one of claims 6-9, characterized in that, The base film, after stretching, has a thickness of 55-70 µm, a surface gloss of 4.5-5 GU, a longitudinal tensile strength of 180-195 MPa, and a transverse tensile strength of 160-175 MPa.