An ultrathin PET shrink film functional masterbatch and a preparation method thereof

Abstract

The application discloses a kind of ultra-thin PET shrink film functional masterbatch and preparation method thereof.The functional masterbatch is composed of modified PET chip, ordinary PET chip and polydimethylsiloxane with reactive group, modified PET chip is prepared by introducing tetraethoxysilane / methyl triethoxysilane modification pretreatment in PET precondensation stage, then melt mixing with ordinary PET chip in double screw extruder and adding polydimethylsiloxane with reactive group, and it is obtained by high temperature and high shear dispersion, grafting reaction, extrusion granulation.The ultra-thin PET shrink film with thickness of 10-20 microns can be directly prepared by using the functional masterbatch, the film body has high transparency, excellent shrinkage performance and good mechanical properties, and high-performance shrink film can be prepared by mixing ordinary PET as needed, to meet the packaging and heat shrinkage application requirements.

Description

Technical Field

[0001] This invention relates to polyester films and their modification and preparation techniques, and more particularly to a functional masterbatch for preparing ultrathin polyethylene terephthalate (PET) shrink films and its preparation method. This functional masterbatch achieves high dispersibility, compatibility, and thermal stability by introducing siloxane modification units and reactive polydimethylsiloxane into the PET molecular chain. It can be used to produce ultrathin, high-energy PET shrink films, and is widely applied in packaging, electronics, and functional film materials. Background Technology

[0002] Polyethylene terephthalate (PET) shrink film is a high-performance film material widely used in packaging, electronics, and functional materials. Traditional PET shrink film is formed into anisotropic orientation structures through mechanical stretching and heat treatment, enabling it to shrink longitudinally or laterally upon heating, and is used for wrapping, sealing, and molding processes. However, with the increasing demand for ultrathin, high-energy shrinkable PET films, existing technologies still face many technical challenges and shortcomings in the preparation of ultrathin films.

[0003] First, it is difficult to uniformly disperse the modifying components in the masterbatch prepared by directly melting ordinary PET chips, leading to uneven local stress or unstable shrinkage during the ultrathin film shrinkage process, especially when the film thickness is less than 50 μm. Second, existing high-energy shrinkable PET film masterbatches mostly use physical mixing methods when introducing functional modifiers, which easily leads to agglomeration or migration of the modifiers, resulting in a decline in film performance, including uneven shrinkage, reduced transparency, and insufficient thermal stability. Furthermore, existing technologies struggle to achieve chemical grafting or highly compatible dispersion of the masterbatch and modifiers while maintaining ultrathin thickness, limiting the widespread application of ultrathin PET shrink films in high-end packaging, electronic components, and precision molding fields.

[0004] Therefore, there is an urgent need for a PET functional masterbatch that can achieve high dispersion, high compatibility and high thermal stability while maintaining ultra-thin thickness, in order to meet the technical requirements for the preparation of ultra-thin high-energy shrinkable PET films and improve the shrinkage uniformity, mechanical properties and processing adaptability of the film. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an ultra-thin PET shrink film functional masterbatch and its preparation method, so as to reduce or avoid the problems mentioned above.

[0006] To address the aforementioned technical problems, this invention proposes an ultra-thin PET shrink film functional masterbatch, prepared from the following raw materials in parts by weight: 5-20 parts by weight of modified PET chips, 80-95 parts by weight of ordinary PET chips, and 0.5-3.0 parts by weight of polydimethylsiloxane with reactive groups; wherein the polydimethylsiloxane with reactive groups is a hydroxyl-terminated polydimethylsiloxane, a polydimethylsiloxane containing epoxy groups, or a polydimethylsiloxane containing methacryloxy groups.

[0007] Preferably, the modified PET chips are prepared from the following raw materials in parts by weight: 90-100 parts by weight of terephthalic acid, 100-110 parts by weight of ethylene glycol, 0.05-0.15 parts by weight of germanium dioxide, 0.05-0.3 parts by weight of triethyl phosphate, and 0.5-5 parts by weight of modified pretreatment material.

[0008] Preferably, the modified pretreatment material is prepared from the following raw materials in parts by weight: 100 parts by weight of tetraethoxysilane, 10-30 parts by weight of methyltriethoxysilane, 80-140 parts by weight of anhydrous ethanol, 25-55 parts by weight of deionized water, and 0.3-1.0 parts by weight of acetic acid.

[0009] The present invention further proposes a method for preparing the above-mentioned functional masterbatch, comprising the following steps: in a twin-screw extruder, modified PET chips and ordinary PET chips are added together in proportion, melt-mixed and fully dispersed under high-speed shear; polydimethylsiloxane with reactive groups is added in the rear section of the extruder, and grafting or compatibility reaction with PET chain segments is achieved under high temperature and high shear conditions; extrusion, cooling, granulation and sieving are performed to obtain the functional masterbatch.

[0010] Preferably, the modified PET chips are prepared by the following steps: terephthalic acid, ethylene glycol, and germanium dioxide are added to a general-purpose polymerization reactor, and an esterification reaction is carried out at 230-265°C and 0.2-0.3 MPa for 1-3 hours; after esterification, the pressure is released to atmospheric pressure, and triethyl phosphate and the modified pretreatment material are added under atmospheric pressure, and the mixture is stirred for about 10 minutes to ensure uniform dispersion; the reaction system is gradually heated to 280°C, and the pressure is reduced to below 100 Pa under vacuum conditions, and the polycondensation reaction is continued for 1-3 hours to obtain modified PET chips.

[0011] Preferably, the modified pretreated material is prepared by the following steps: First, anhydrous ethanol, tetraethoxysilane, and methyltriethoxysilane are sequentially added to a reactor equipped with a reflux condenser and stirring device, and the temperature is controlled at 20-35°C to avoid excessively rapid condensation. The mixture is stirred uniformly for 30-60 minutes. Then, acetic acid is added as a weak acid catalyst, followed by deionized water added in portions, and stirring is continued for 30 minutes to obtain a homogeneous sol system. Subsequently, stirring is continued at 25-50°C for 30-120 minutes to allow partial condensation of the system while maintaining the system in a flowable sol / colloid state without producing obvious gel. Finally, ethanol and excess water are gradually removed through a vacuum evaporation device connected to the reactor at a temperature of 40-70°C and a pressure of 500-2000 Pa to obtain the modified pretreated material.

[0012] Preferably, the temperature of the melt mixing section of the twin-screw extruder is 260-280℃, the mixing time is 2-5 minutes, the residence time in the extrusion section is 5-10 minutes, the screw speed is 300-600 rpm, and the shear rate is 1000-1500 s⁻¹.

[0013] Preferably, in the modified pretreated material, the residual ethanol is ≤3 wt%, the residual water is ≤0.2-0.5 wt%, and the residual acetic acid is ≤0.05-0.1 wt%.

[0014] This invention relates to an ultra-thin PET shrink film functional masterbatch and its preparation method. Modified PET chips are prepared by introducing a tetraethoxysilane / methyltriethoxysilane modified pretreatment material during the PET prepolymerization stage. These chips are then melt-mixed with ordinary PET chips in a twin-screw extruder. Simultaneously, polydimethylsiloxane with reactive groups is added, achieving efficient grafting and uniform dispersion of the modified PET chips and PDMS, thereby significantly improving the compatibility and functionalization effect of the masterbatch. The ultra-thin PET shrink film prepared using this functional masterbatch can be controlled in thickness within the range of 10-20 micrometers, exhibiting high transparency, good mechanical properties, and excellent shrinkage performance, meeting the requirements of high-energy shrinkage applications. Compared to existing technologies, the functional masterbatch of this invention can achieve a uniform siloxane nano-dispersion structure, improving the thermal and dimensional stability of the film. Furthermore, it can be mixed with ordinary PET as needed, flexibly adjusting shrinkage and physical properties, significantly improving the overall performance and application value of the product. Detailed Implementation

[0015] To provide a clearer understanding of the technical features, objectives, and effects of this application, the specific implementation methods of this application are now described in detail.

[0016] As mentioned earlier, there are several technical challenges in the preparation of existing ultrathin PET shrink films: First, the uneven dispersion of modified components in the masterbatch leads to uneven local stress during film shrinkage, making it difficult to control shrinkage rate and dimensional stability simultaneously; second, in traditional physical mixing modification methods, functional modifiers are prone to agglomeration or migration, which reduces the transparency and mechanical properties of the film; third, the thickness of the ultrathin film limits the orientation and thermal stability of polymer chain segments, making the film performance unstable under high-temperature processing conditions.

[0017] To address the aforementioned problems, this invention proposes the following solution: By introducing reactive siloxane modification units into the PET molecular chain and employing chemical grafting or highly compatible dispersion methods during the masterbatch preparation stage, the modified components are uniformly distributed in the melt, achieving good integration with the PET chain segments. This not only improves the dispersibility of the modifier, preventing agglomeration and migration, but also provides uniform stress transfer during film thermal shrinkage, improving shrinkage uniformity and dimensional stability. Simultaneously, by controlling the structure and distribution of the modified components in the masterbatch, chain segment orientation and thermal stability can be maintained at ultrathin film thicknesses, thereby obtaining ultrathin, high-energy shrinkable PET films with high transparency and excellent mechanical properties.

[0018] Specifically, based on the above-mentioned solution, this invention provides a functional masterbatch for ultra-thin PET shrink film and its preparation method. The functional masterbatch is prepared from the following raw materials in parts by weight: 5-20 parts by weight of modified PET chips, 80-95 parts by weight of ordinary PET chips, and 0.5-3.0 parts by weight of polydimethylsiloxane with reactive groups. This invention utilizes a combination of chemical grafting and high compatibility dispersion to ensure uniform distribution of the modified components in the masterbatch, thereby improving the shrinkage uniformity, dimensional stability, and processing adaptability of the ultra-thin PET shrink film.

[0019] The reactive PDMS can be selected from one of the following commercial models: for example, Shin-Etsu's KF-6001, whose main component is hydroxyl-terminated polydimethylsiloxane (HO-PDMS-OH), which can undergo condensation reactions with PET terminal hydroxyl or carboxyl groups to improve compatibility and dispersibility; or Dow Corning's OE-6630, whose main component is epoxy-containing polydimethylsiloxane, which can undergo ring-opening reactions with PET molecular chains terminal carboxyl or hydroxyl groups to achieve graft modification; or Clariant's Silres MK, whose main component is methacryloyloxy-containing polydimethylsiloxane, which can undergo free radical copolymerization with PET segments under melt processing conditions to improve heat resistance and regulate surface energy. Different types of PDMS can be selected according to functional requirements to optimize masterbatch performance and subsequent film properties.

[0020] The modified PET chips can be prepared from the following raw materials in parts by weight: 90-100 parts by weight of terephthalic acid, 100-110 parts by weight of ethylene glycol, 0.05-0.15 parts by weight of germanium dioxide, 0.05-0.3 parts by weight of triethyl phosphate, and 0.5-5 parts by weight of modified pretreatment material. The modified pretreatment material can react with the PET molecular chain during the polycondensation stage to achieve uniform dispersion and chemical grafting of siloxane groups.

[0021] The modified pretreatment material is further prepared from the following raw materials in parts by weight: 100 parts by weight of TEOS (tetraethoxysilane), 10-30 parts by weight of MPTES (methyltriethoxysilane, as a grafting / bonding agent), 80-140 parts by weight of anhydrous ethanol (solvent / diluent), 25-55 parts by weight of deionized water (for hydrolysis), and 0.3-1.0 parts by weight of acetic acid (weak acid catalyst). This invention, through a rational proportioning design, ensures that the modified pretreatment material can be uniformly dispersed and form nanoscale siloxane structures during subsequent PET polycondensation, while simultaneously avoiding the formation of gels or agglomerates.

[0022] Furthermore, in one specific embodiment, the modified pretreatment material can be prepared by the following steps: In a reactor equipped with a reflux condenser and stirring device, anhydrous ethanol, tetraethoxysilane and methyltriethoxysilane are added sequentially, the temperature is controlled at 20-35°C to avoid excessive condensation, and the mixture is stirred uniformly for 30-60 minutes; then acetic acid is added as a weak acid catalyst, and deionized water is added in portions, and stirring is continued for 30 minutes to allow the siloxane groups to initially hydrolyze and form a sol system. The system should be homogeneous and free of obvious white solid precipitate.

[0023] Continue stirring at 25-50℃ for 30-120 minutes to allow some of the hydrolysis products to condense into small amounts of Si-O-Si segments and Si-OH groups. The solution gradually transforms from a low-viscosity liquid into a slightly viscous sol / colloid, but significant gelation or blocky solid formation should not occur. This step ensures that the pretreated material can be effectively grafted and maintain its dispersibility in subsequent PET polycondensation.

[0024] Subsequently, the system is subjected to reduced pressure evaporation via a vacuum evaporator connected to the reactor to remove most of the ethanol and minimize the residue of catalytic acid and byproducts, in order to obtain a stable modified pretreatment containing Si-OH / oligosiloxane.

[0025] The vacuum evaporation step includes: first, vacuum evaporation at 40-60℃ and 5000-20000 Pa for 30-60 minutes; then, gradually increasing the temperature to 45-70℃ and reducing the pressure to 500-2000 Pa for 30-90 minutes, ultimately resulting in ethanol residue ≤3wt%, water residue 0.2-0.5wt%, and acetic acid residue ≤0.05-0.1wt%. These residues are acceptable in subsequent PET polycondensation processes and will not significantly affect the synthesis or properties of the polyester molecular chain. They can be further adjusted as needed through low-temperature vacuum.

[0026] Furthermore, in one specific embodiment, the modified PET chips of the present invention can be prepared by the following steps: in a general polymerization reactor, terephthalic acid (TPA), ethylene glycol (EG) and germanium dioxide (GeO2) are added to carry out an esterification reaction, and the conditions are controlled at 230-265°C, 0.2-0.3 MPa, for 1-3 hours, so that the acid anhydride is fully esterified to generate polyester precursor.

[0027] After esterification, the pressure is released to atmospheric pressure, and triethyl phosphate and the modified pretreatment material are added at room temperature to 150°C. The mixture is stirred for about 10 minutes to ensure uniform dispersion of the modified components and avoid localized overheating. Triethyl phosphate is used to adjust the concentration of end groups and inhibit polyester decomposition; the modified pretreatment material introduces siloxane groups and active end groups, which can react with the PET molecular chains during the polycondensation stage to achieve chemical grafting or compatibility.

[0028] The temperature was then gradually increased to approximately 280°C, and the pressure was reduced to below 100 Pa under vacuum conditions. Polycondensation continued for 1-3 hours to achieve the designed molecular weight of the polyester, while simultaneously forming a uniformly dispersed nanoscale siloxane structure. After the reaction, the polycondensation product was extruded, pelletized, and dried to obtain modified PET chips, which can be used for the preparation of functional masterbatches.

[0029] Furthermore, in another specific embodiment, the ultra-thin PET shrink film functional masterbatch of the present invention can be prepared by the following steps: In a twin-screw extruder, modified PET chips and ordinary PET chips are added in proportion, melt-mixed, and fully dispersed under high-speed shearing of the screw, so that the siloxane groups and terminal hydroxyl groups in the modified PET chips are uniformly distributed throughout the melt. The temperature of the melt mixing section is controlled at 260-280℃, the mixing time is 2-5 minutes, the screw speed is 300-600 rpm, and the shear rate is 1000-1500 s⁻¹.

[0030] PDMS with reactive groups is added in the downstream section of the extruder. The PDMS used can be hydroxyl-terminated (Shin-Etsu KF-6001), epoxy (Dow Corning OE-6630), or methacryloyloxy (Clariant Silres MK). Under high temperature (260-280℃) and high shear conditions, it undergoes grafting or condensation reactions with the hydroxyl or carboxyl groups of the PET chain to achieve high compatibility and functionalization.

[0031] The material with added reactive polydimethylsiloxane is further extruded and cooled to 80-120℃, and then granulated and sieved to obtain a uniform and stable functional masterbatch.

[0032] The temperature and pressure throughout the extrusion process must be strictly controlled to prevent PET degradation or PDMS over-polymerization. The residence time of the material in the extruder is controlled at 5-10 minutes. The overall process ensures that PDMS is fully dispersed and completes the necessary grafting, while maintaining the uniformity and thermal stability of the masterbatch particles.

[0033] Example 1

[0034] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch composition consisted of 5 parts modified PET chips, 94.5 parts ordinary PET chips, and 0.5 parts hydroxyl-terminated PDMS (Shin-Etsu KF-6001). The modified PET chips were composed of 90 parts terephthalic acid, 100 parts ethylene glycol, 0.05 parts germanium dioxide, 0.05 parts triethyl phosphate, and 0.5 parts modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 15 μm, a light transmittance of approximately 92%, a maximum shrinkage rate (MD) of approximately 40%, a maximum shrinkage rate (TD) of approximately 35%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 95%, a tensile strength of approximately 160 MPa, an elongation at break of approximately 120%, and a surface smoothness Ra of approximately 8 nm. It exhibited rapid and uniform shrinkage, significant high-energy shrinkage characteristics, and simultaneously demonstrated ultrathinness and high transparency.

[0035] Example 2

[0036] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch consisted of 10 parts modified PET chips, 88 parts ordinary PET chips, and 2 parts epoxy-based PDMS (Dow Corning OE-6630). The modified PET chips were composed of 92 parts terephthalic acid, 105 parts ethylene glycol, 0.1 parts germanium dioxide, 0.1 parts triethyl phosphate, and 1 part modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 18 μm, a light transmittance of approximately 91%, a maximum shrinkage rate (MD) of approximately 42%, a maximum shrinkage rate (TD) of approximately 37%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 96%, a tensile strength of approximately 162 MPa, an elongation at break of approximately 118%, and a surface smoothness Ra of approximately 9 nm. It exhibited significant high-energy shrinkage characteristics while simultaneously demonstrating ultrathinness and high transparency.

[0037] Example 3

[0038] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch consisted of 15 parts modified PET chips, 82 parts ordinary PET chips, and 3 parts methacryloyloxy-type PDMS (Clariant Silres MK). The modified PET chips were composed of 95 parts terephthalic acid, 108 parts ethylene glycol, 0.12 parts germanium dioxide, 0.15 parts triethyl phosphate, and 1.5 parts modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 12 μm, a light transmittance of approximately 90%, a maximum shrinkage rate (MD) of approximately 45%, a maximum shrinkage rate (TD) of approximately 40%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 97%, a tensile strength of approximately 165 MPa, an elongation at break of approximately 115%, and a surface smoothness Ra of approximately 9 nm. It exhibited rapid and uniform shrinkage, demonstrating high shrinkage performance while maintaining ultrathinness, high transparency, and excellent mechanical properties.

[0039] Example 4

[0040] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch consisted of 8 parts modified PET chips, 90 parts ordinary PET chips, and 2 parts epoxy-based PDMS (Dow Corning OE-6630). The modified PET chips were composed of 91 parts terephthalic acid, 103 parts ethylene glycol, 0.08 parts germanium dioxide, 0.08 parts triethyl phosphate, and 0.8 parts modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 16 μm, a light transmittance of approximately 91%, a maximum shrinkage rate (MD) of approximately 41%, a maximum shrinkage rate (TD) of approximately 36%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 96%, a tensile strength of approximately 161 MPa, an elongation at break of approximately 119%, and a surface smoothness Ra of approximately 8 nm. It exhibited uniform and rapid shrinkage, demonstrating high-energy shrinkage characteristics, while also being ultrathin and highly transparent.

[0041] Example 5

[0042] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch composition consisted of 12 parts modified PET chips, 85 parts ordinary PET chips, and 2.5 parts methacryloyloxy-type PDMS (Clariant Silres MK). The modified PET chips were composed of 93 parts terephthalic acid, 107 parts ethylene glycol, 0.1 parts germanium dioxide, 0.12 parts triethyl phosphate, and 1.2 parts modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 14 μm, a light transmittance of approximately 90%, a maximum shrinkage rate (MD) of approximately 43%, a maximum shrinkage rate (TD) of approximately 38%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 96%, a tensile strength of approximately 163 MPa, an elongation at break of approximately 116%, and a surface smoothness Ra of approximately 9 nm. It exhibited significant high-energy shrinkage performance, rapid and uniform shrinkage, and combined ultrathinness with high transparency.

[0043] Example 6

[0044] Ultrathin PET shrink film was prepared using the functional masterbatch of this invention. The masterbatch composition consisted of 18 parts modified PET chips, 79 parts ordinary PET chips, and 1.5 parts hydroxyl-terminated PDMS (Shin-Etsu KF-6001). The modified PET chips were composed of 97 parts terephthalic acid, 110 parts ethylene glycol, 0.15 parts germanium dioxide, 0.2 parts triethyl phosphate, and 2 parts modified pretreatment material. The resulting ultrathin PET shrink film had a thickness of approximately 13 μm, a light transmittance of approximately 91%, a maximum shrinkage rate (MD) of approximately 44%, a maximum shrinkage rate (TD) of approximately 39%, excellent shrinkage uniformity, a heat shrinkage stability of approximately 97%, a tensile strength of approximately 164 MPa, an elongation at break of approximately 117%, and a surface smoothness Ra of approximately 8 nm. It exhibited rapid and uniform shrinkage, demonstrating high-energy shrinkage characteristics while maintaining ultrathinness, high transparency, and excellent mechanical properties.

[0045] Overall, the functional masterbatch prepared by this invention can be directly used to prepare ultra-thin PET shrink films with a thickness of 10-20 μm. The resulting films possess high transparency (light transmittance of approximately 90-92%), high shrinkage performance (MD shrinkage rate of 40-45%, TD shrinkage rate of 35-40%, uniform shrinkage and thermal stability of 95-97%), and excellent mechanical properties (tensile strength of 160-165 MPa, elongation at break of 115-120%). Furthermore, they exhibit a smooth surface and rapid, uniform shrinkage, fully embodying the characteristics of "ultra-thin, high shrinkage, and excellent mechanical properties." It is worth noting that, depending on actual needs, the functional masterbatch of this invention can also be mixed with ordinary PET chips in a certain proportion to prepare shrink films, similarly obtaining ultra-thin, high-energy shrinkable PET shrink films with a thickness in the 10-20 μm range and stable, uniform performance. This provides a flexible and high-performance solution for various packaging and heat-shrink applications.

[0046] Comparative Example 1

[0047] Ultrathin PET shrink film was prepared using ordinary PET chips alone, without the addition of modified PET chips or PDMS. The resulting film had a thickness of approximately 15 μm, a light transmittance of approximately 90%, a maximum shrinkage rate (MD) of only about 10%, a maximum shrinkage rate (TD) of about 8%, uneven shrinkage, poor thermal stability (approximately 85%), a tensile strength of approximately 155 MPa, an elongation at break of approximately 110%, a slightly rough surface, and a slow shrinkage rate, clearly lacking high-energy shrinkage properties.

[0048] Comparative Example 2

[0049] The proportion of modified PET chips in the functional masterbatch was reduced to only 2 parts, with the remainder being 98 parts of ordinary PET chips, and no PDMS was added. The resulting film had a thickness of approximately 16 μm, a light transmittance of approximately 91%, an MD shrinkage rate of approximately 15%, a TD shrinkage rate of approximately 12%, and the shrinkage was still uneven. The heat shrinkage stability was approximately 87%, the tensile strength was approximately 157 MPa, the elongation at break was approximately 112%, the surface smoothness was slightly inferior, and the shrinkage rate and uniformity were significantly lower than those of Examples 1-6.

[0050] Comparative Example 3

[0051] The functional masterbatch is complete, but PDMS is not added to it. The resulting film has a thickness of about 14 μm, a light transmittance of about 90%, an MD shrinkage rate of about 20%, a TD shrinkage rate of about 18%, insufficient shrinkage and slight curling in some areas, a heat shrinkage stability of about 88%, a tensile strength of about 158 ​​MPa, an elongation at break of about 113%, and a surface smoothness that is not as good as the film containing PDMS, making it difficult to achieve the high shrinkage performance of the example.

[0052] Comparative Example 4

[0053] The functional masterbatch was complete, but the modified PET chips lacked the modified pretreatment material (i.e., TEOS / MPTES was not added). PDMS was added according to the proportions in the examples. The resulting film had a thickness of approximately 15 μm, a light transmittance of approximately 90%, an MD shrinkage rate of approximately 25%, a TD shrinkage rate of approximately 22%, a relatively slow shrinkage rate and poor uniformity, a heat shrinkage stability of approximately 90%, a tensile strength of approximately 159 MPa, an elongation at break of approximately 114%, and slightly lower surface smoothness. Overall, its performance was still significantly inferior to that of Examples 1-6.

[0054] In summary, the comparative examples above demonstrate that the absence of any component—modified PET chips, modified pretreatment material, or PDMS—significantly reduces the high-energy shrinkage performance, shrinkage uniformity, thermal stability, and mechanical properties of the ultrathin PET shrink film. Compared to Examples 1-6 of this invention, the comparative films exhibit lower shrinkage rates, uneven shrinkage, insufficient thermal stability, and reduced surface smoothness, fully showcasing the significant advantages of the functional masterbatch and its preparation method in terms of ultrathinness, high transparency, high shrinkage capacity, and excellent mechanical properties.

[0055] 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.

[0056] 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. An ultra-thin PET shrink film functional masterbatch, characterized in that, It is prepared from the following raw materials in parts by weight: 5-20 parts by weight of modified PET chips, 80-95 parts by weight of ordinary PET chips, and 0.5-3.0 parts by weight of polydimethylsiloxane with reactive groups; wherein the polydimethylsiloxane with reactive groups is a hydroxyl-terminated polydimethylsiloxane, a polydimethylsiloxane containing epoxy groups, or a polydimethylsiloxane containing methacryloxy groups.

2. The functional masterbatch according to claim 1, characterized in that The modified PET chips are prepared from the following raw materials in parts by weight: 90-100 parts by weight of terephthalic acid, 100-110 parts by weight of ethylene glycol, 0.05-0.15 parts by weight of germanium dioxide, 0.05-0.3 parts by weight of triethyl phosphate, and 0.5-5 parts by weight of modified pretreatment material.

3. The functional masterbatch according to claim 2, characterized in that, The modified pretreatment material is prepared from the following raw materials in parts by weight: 100 parts by weight of tetraethoxysilane, 10-30 parts by weight of methyltriethoxysilane, 80-140 parts by weight of anhydrous ethanol, 25-55 parts by weight of deionized water, and 0.3-1.0 parts by weight of acetic acid.

4. A method for preparing the functional masterbatch according to any one of claims 1-3, characterized in that, The process includes the following steps: In a twin-screw extruder, modified PET chips and ordinary PET chips are added together in proportion, melt-mixed and fully dispersed under high-speed shear; Polydimethylsiloxane with reactive groups is added to the rear section of the extruder, and grafting or compatibility reaction with PET segments is achieved under high temperature and high shear conditions; extrusion, cooling, granulation and screening are performed to obtain functional masterbatch.

5. The method according to claim 4, characterized in that, The modified PET chips are prepared by the following steps: terephthalic acid, ethylene glycol, and germanium dioxide are added to a general-purpose polymerization reactor, and an esterification reaction is carried out at 230-265℃ and 0.2-0.3 MPa for 1-3 hours; after esterification, the pressure is released to atmospheric pressure, and triethyl phosphate and the modified pretreatment material are added under atmospheric pressure, and the mixture is stirred for about 10 minutes to ensure uniform dispersion; the reaction system is gradually heated to 280℃, and the pressure is reduced to below 100 Pa under vacuum conditions, and the polycondensation reaction continues for 1-3 hours; the polycondensation product is extruded, pelletized, and dried to obtain modified PET chips.

6. The method according to claim 5, characterized in that, The modified pretreatment product is prepared by the following steps: First, anhydrous ethanol, tetraethoxysilane, and methyltriethoxysilane are sequentially added to a reactor equipped with a reflux condenser and stirring device, with the temperature controlled at 20-35℃ to avoid excessively rapid condensation, and the mixture is stirred uniformly for 30-60 minutes; then acetic acid is added as a weak acid catalyst, followed by deionized water added in portions, and the mixture is stirred for another 30 minutes to obtain a homogeneous sol system; subsequently, the mixture is stirred for another 30-120 minutes at 25-50℃ to allow partial condensation of the system; finally, ethanol and excess water are gradually removed through a vacuum evaporator connected to the reactor at a temperature of 40-70℃ and a pressure of 500-2000 Pa to obtain the modified pretreatment product.

7. The method according to claim 4, characterized in that, The temperature of the melt mixing section of the twin-screw extruder is 260-280℃, the mixing time is 2-5 minutes, the residence time in the extrusion section is 5-10 minutes, the screw speed is 300-600 rpm, and the shear rate is 1000-1500 s⁻¹.

8. The method according to claim 6, characterized in that, The modified pretreated material contains ethanol residue ≤3 wt%, water residue ≤0.2-0.5 wt%, and acetic acid residue ≤0.05-0.1 wt%.