A polyester film with pressure-sensitive discoloration, a preparation method and application thereof

Abstract

This invention relates to the field of functional polyester film technology, specifically to a pressure-sensitive color-changing polyester film, its preparation method, and its application. The preparation method of the pressure-sensitive color-changing polyester film includes the following steps: S1, adding pure polyester PET chips (core layer preparation material), pure polyester chips (upper and lower surface layer preparation materials), and anti-sticking masterbatch to an extruder, and preparing a substrate layer through a three-layer co-extrusion and biaxial stretching process; S2, mixing acrylic resin emulsion, pressure-sensitive color-changing microcapsule powder, dispersant, defoamer, water-based wax powder, and solvent to prepare a coating liquid, and then applying the coating liquid to the surface of the substrate layer by online coating or specific pattern gravure coating to obtain a pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating is 1.2 g / m². 2 S3. Prepare a primer coating solution by mixing the primer and thinner in a ratio of 78% to 22%. Then, apply the solution to the surface of the pressure-sensitive color-changing coating using an online coating method to form a primer coating. The dry weight of the primer coating is controlled at 1.0 g / m². 2 S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect is obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes. The pressure-sensitive color-changing polyester film involved in this invention can reveal the scratch stress color at scratches during the transverse stretching and traction processes, assisting the inspection machine in detecting specific scratches on the film, greatly reducing the detection limit of the inspection machine for film scratches, and improving product yield.

Description

Technical Field

[0001] This invention relates to the field of functional polyester film technology, specifically to a pressure-sensitive color-changing polyester film, its preparation method, and its application. Background Technology

[0002] Biaxially oriented polyester film, due to its high tensile strength, good light transmittance, colorless, odorless, and non-toxic properties, has seen significant development in food packaging, cigarette packaging, and electronic display fields in recent years. With advancements in technology and materials science, functional anti-counterfeiting films have emerged. In recent years, the application of thermosensitive color-changing microcapsules, moisture-sensitive color-changing microcapsules, and flavor-controlled-release microcapsules in the film field has received widespread attention, while research on the application of pressure-sensitive color-changing microcapsules in anti-counterfeiting films is scarce.

[0003] During the production of polyester film, the film substrate is passed between steel rollers and rubber pressure rollers. Foreign matter on the surfaces of the rubber pressure rollers and steel rollers can easily cause scratches on the film surface under the winding tension, especially in the transverse stretching and traction sections. Due to the extremely high light transmittance of the film, the inspection machine at the end of the production line has difficulty detecting minor scratches, which can easily lead to a decline in product quality. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a pressure-sensitive color-changing polyester film, its preparation method, and its applications.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a pressure-sensitive color-changing polyester film, the method comprising the following steps:

[0007] S1. Pure polyester PET chips (the raw material for the core layer), pure polyester chips (the raw materials for the upper and lower surface layers), and anti-sticking masterbatch are added to an extruder and the substrate layer is prepared by a three-layer co-extrusion and biaxial stretching process.

[0008] S2. An acrylic resin emulsion, pressure-sensitive color-changing microcapsule powder, dispersant, defoamer, water-based wax powder, and solvent are mixed to prepare a coating liquid. The coating liquid is then applied to the substrate surface via online coating for full-area application or gravure coating with a specific pattern to obtain a pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating is 1.2 g / m². 2 ;

[0009] S3. Prepare a primer coating solution by mixing the primer and thinner in a ratio of 78% to 22%. Then, apply the solution onto the surface of the pressure-sensitive color-changing coating using an online coating method to form a primer coating. The dry weight of the primer coating is controlled at 1.0 g / m². 2 ;

[0010] S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect can be obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes.

[0011] Preferably, the mass ratio of the raw materials for preparing the pressure-sensitive color-changing coating, namely acrylic resin emulsion, pressure-sensitive color-changing microcapsule powder, dispersant, defoamer, water-based wax powder and solvent, is (65-70):(6-10):(0.5-1):(0.5-1):(1-3):(27-30).

[0012] Preferably, the dispersant is a polyvinyl alcohol hydrophilic polymer, the defoamer is an organosilicon defoamer, and the solvent is a mixture of ethanol and water, with a volume ratio of ethanol to water of 1:5.

[0013] Preferably, the raw material formulations for the upper and lower surface layers are the same, consisting of pure polyester chips and anti-adhesion masterbatch, and the mass ratio of pure polyester chips to anti-adhesion masterbatch is (38-45):(55-62).

[0014] Preferably, the primer is an acrylic resin primer or a polyurethane primer.

[0015] Preferably, the diluent is a mixture of alcohol and deionized water, wherein the volume ratio of alcohol to deionized water is 1:5.

[0016] Preferably, in step S2, the temperature of the online coating box is controlled at 100℃±10℃; in step S3, the coating temperature is controlled at 100℃±10℃.

[0017] A pressure-sensitive color-changing polyester film is prepared by the preparation method described above.

[0018] As described above, a pressure-sensitive color-changing polyester film is used as an anti-counterfeiting film in the food packaging field.

[0019] The beneficial effects of this invention are:

[0020] 1. The pressure-sensitive color-changing polyester film involved in this invention can display the scratch stress color of scratches during the transverse stretching and traction processes, assisting the inspection machine in discovering specific scratches on the film, greatly reducing the detection limit of the inspection machine for scratches on the film, and improving the product yield.

[0021] 2. This pressure-sensitive color-changing film can have anti-counterfeiting effects. The pressure-sensitive color-changing coating can be gravure-printed using a customized gravure pattern, and the film will develop color under certain pressure conditions. It can be used for pressure warning and pressure-based anti-counterfeiting functions in film products. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Preparation of polyester film substrate layer

[0024] The substrate layer includes an upper surface layer, a core layer, and a lower surface layer;

[0025] The specific preparation steps are as follows:

[0026] Step 1: Dry pure polyester chips in a fluidized bed at 120°C for two hours, then heat them to a molten state in the main extruder, and filter them to obtain the main extruded melt as the core layer; the extrusion rate in the main extruder is 22.7 rpm.

[0027] Step 2: The raw materials for the upper surface layer, pure polyester chips and anti-sticking masterbatch, and the raw materials for the lower surface layer, pure polyester chips and anti-sticking masterbatch, are added to two auxiliary extruders respectively. After melting, vacuuming, and filtering, the upper surface auxiliary extrusion melt and the lower surface auxiliary extrusion melt are obtained. The extrusion rate in both auxiliary extruders is 47.7 rpm.

[0028] Step 3: The main extrusion melt, the upper surface auxiliary extrusion melt, and the lower surface auxiliary extrusion melt are combined and extruded in the T-die area, and then cast and stretched to obtain the base material layer.

[0029] The core layer of pure polyester PET chips was purchased from Lucky Pharma China. The pure PET polyester chips have an intrinsic viscosity of 0.6-0.66 dl / g, a moisture content of ≤2000ppm, a melting point of 260±6℃, and a color b value of 5±3.

[0030] The pure polyester chips used for the upper and lower surface layers were purchased from Zhejiang Yongsheng Dayouguang Chips, and the anti-sticking masterbatch was purchased from Zhejiang Yongsheng Special Supply Anti-sticking Masterbatch. Zhejiang Yongsheng's pure polyester chips have an intrinsic viscosity of 0.6-0.66 dl / g, a moisture content ≤2000ppm, a melting point of 260±6℃, and a colorimetric b value of 5±3. The anti-sticking masterbatch used for the upper and lower surface layers has an intrinsic viscosity of 0.56-0.66 dl / g, a moisture content ≤2000ppm, a melting point of 260±6℃, and a colorimetric b value of 5±3.

[0031] Pressure-sensitive colorimetric microcapsules are microcapsules containing a solution of leuco dye. Under certain pressure, the capsule wall ruptures, releasing the organic solvent containing the leuco dye, which reacts with the colorimetric agent to produce color. These capsules consist of two parts: a wall material and a core material, with the core material encapsulated within the wall material. The wall material is made of gelatin. The core material is composed of leuco dye and an organic colorimetric agent, with a mass ratio of leuco dye to organic colorimetric agent of 1:1. The leuco dye is generally a cationic dye precursor, typically made of crystal violet lactone (CVL), and the organic solvent is diisopropylnaphthalene.

[0032] Example 1

[0033] S1. The substrate layer is prepared according to the above method for preparing a polyester film substrate layer;

[0034] S2. A coating liquid is prepared by mixing 65 parts of acrylic resin emulsion, 6 parts of pressure-sensitive color-changing microcapsule powder, 0.5 parts of dispersant, 1 part of defoamer, 1 part of water-based wax powder, and 27 parts of solvent. The coating liquid is then applied to the entire surface of the substrate layer via online coating. The dry weight of the pressure-sensitive color-changing coating is 1.2 g / m². 2 The temperature of the online coating horizontal stretching box is controlled at 100℃;

[0035] S3. Prepare a primer coating solution by mixing the primer and diluent, and then apply it to the surface of the pressure-sensitive color-changing coating via online coating to form a primer coating; the volume ratio of the primer to the diluent is 78:22; the primer is an acrylic resin primer, and the diluent is a mixture of alcohol and deionized water, wherein the volume ratio of alcohol to deionized water is 1:5; the dry weight of the primer coating is controlled at 1.0 g / m³. 2 The coating temperature is controlled at 100℃.

[0036] S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect can be obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes.

[0037] Example 2

[0038] S1. The substrate layer is prepared according to the above method for preparing a polyester film substrate layer;

[0039] S2. A coating liquid is prepared by mixing 68 parts of acrylic resin emulsion, 8 parts of pressure-sensitive color-changing microcapsule powder, 0.8 parts of dispersant, 0.5 parts of defoamer, 2 parts of water-based wax powder, and 28 parts of solvent. The coating liquid is then applied to the substrate surface via online coating. The dry weight of the pressure-sensitive color-changing coating is 1.2 g / m². 2 The temperature of the online coating horizontal stretching box is controlled at 110℃;

[0040] S3. Prepare a primer coating solution by mixing the primer and diluent, and then apply it to the surface of the pressure-sensitive color-changing coating via online coating to form a primer coating; the volume ratio of the primer to the diluent is 78:22; the primer is an acrylic resin primer, and the diluent is a mixture of alcohol and deionized water, wherein the volume ratio of alcohol to deionized water is 1:5; the dry weight of the primer coating is controlled at 1.0 g / m³. 2 The coating temperature is controlled at 110℃.

[0041] S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect can be obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes.

[0042] Example 3

[0043] S1. The substrate layer is prepared according to the above method for preparing a polyester film substrate layer;

[0044] S2. A coating liquid is prepared by mixing 70 parts of acrylic resin emulsion, 10 parts of pressure-sensitive color-changing microcapsule powder, 1 part of dispersant, 1 part of defoamer, 3 parts of water-based wax powder, and 30 parts of solvent. The coating liquid is then applied to the entire surface of the substrate layer via online coating. The dry weight of the pressure-sensitive color-changing coating is 1.2 g / m². 2 The temperature of the online coating horizontal stretching box is controlled at 90℃;

[0045] S3. Prepare a primer coating solution by mixing the primer and diluent, and then apply it to the surface of the pressure-sensitive color-changing coating via online coating to form a primer coating; the volume ratio of the primer to the diluent is 78:22; the primer is an acrylic resin primer, and the diluent is a mixture of alcohol and deionized water, wherein the volume ratio of alcohol to deionized water is 1:5; the dry weight of the primer coating is controlled at 1.0 g / m³. 2 The coating temperature is controlled at 90℃.

[0046] S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect can be obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes.

[0047] Comparative Example 1

[0048] Compared with Example 1, the raw materials for preparing the pressure-sensitive color-changing coating in Comparative Example 1 lacked the pressure-sensitive color-changing microcapsule powder component, while the other raw materials were the same as those in Example 1.

[0049] Comparative Example 2

[0050] Comparative Example 2 followed essentially the same steps as Example 1, except for the dry coating weight of the pressure-sensitive color-changing coating. The dry coating weight of the pressure-sensitive color-changing coating in Comparative Example 2 was 1.0 g / m².2 .

[0051] Comparative Example 3

[0052] Comparative Example 3 followed essentially the same steps as Example 1, except for the dry weight of the pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating in Comparative Example 3 was 0.8 g / m². 2 .

[0053] Comparative Example 4

[0054] Comparative Example 4 followed essentially the same steps as Example 1, except for the dry weight of the pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating in Comparative Example 4 was 1.4 g / m². 2 .

[0055] Comparative Example 5

[0056] Comparative Example 5 followed essentially the same steps as Example 1, except for the dry weight of the pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating in Comparative Example 5 was 1.6 g / m³. 2 .

[0057]

[0058] The experimental results from the examples and comparative examples show that the dry weight of the pressure-sensitive color-changing coating on the film substrate has a significant impact on the performance of the pressure-sensitive color-changing polyester film. Excessive dry weight results in good pressure color development, but can easily lead to poor adhesion between the primer coating and the film substrate. Insufficient dry weight results in poor color development. Therefore, strict control of the dry weight of the pressure-sensitive color-changing coating is necessary during production to obtain high-quality pressure-sensitive color-changing polyester film.

[0059] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a pressure-sensitive color-changing polyester film, characterized in that, The preparation method includes the following steps: S1. Pure polyester PET chips (the raw material for the core layer), pure polyester chips (the raw materials for the upper and lower surface layers), and anti-sticking masterbatch are added to an extruder and the substrate layer is prepared by a three-layer co-extrusion and biaxial stretching process. S2. An acrylic resin emulsion, pressure-sensitive color-changing microcapsule powder, dispersant, defoamer, water-based wax powder, and solvent are mixed to prepare a coating liquid. The coating liquid is then applied to the substrate surface via online coating for full-area application or gravure coating with a specific pattern to obtain a pressure-sensitive color-changing coating. The dry weight of the pressure-sensitive color-changing coating is 1.

2. The mass ratio of acrylic resin emulsion, pressure-sensitive color-changing microcapsule powder, dispersant, defoamer, water-based wax powder, and solvent is (65-70):(6-10):(0.5-1):(0.5-1):(1-3):(27-30). The dispersant is a polyvinyl alcohol hydrophilic polymer, the defoamer is an organosilicon defoamer, and the solvent is a mixture of ethanol and water with a volume ratio of ethanol to water of 1:

5. S3. Prepare a primer coating solution by mixing the primer and thinner in a ratio of 78% to 22%. Then, apply the solution to the surface of the pressure-sensitive color-changing coating using an online coating method to form a primer coating. The dry weight of the primer coating should be controlled at 1.

0. The diluent is a mixture of alcohol and deionized water, wherein the volume ratio of alcohol to deionized water is 1:5; the coating temperature is controlled at 100℃±10℃. S4. After the primer coating is applied, the polyester film with pressure-sensitive color-changing effect can be obtained by sequentially performing stretching, shaping, cooling, corona treatment, and winding processes.

2. The preparation method according to claim 1, characterized in that, The upper and lower surface layers are prepared using the same raw material formula, which is pure polyester chips and anti-adhesion masterbatch, and the mass ratio of pure polyester chips to anti-adhesion masterbatch is (38-45):(55-62).

3. The preparation method according to claim 1, characterized in that, The primer is either an acrylic resin primer or a polyurethane primer.

4. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the online coating horizontal stretching box is controlled at 100℃±10℃.

5. A pressure-sensitive color-changing polyester film is prepared by the preparation method according to any one of claims 1-4.

6. The pressure-sensitive color-changing polyester film as described in claim 5 is used as an anti-counterfeiting film in the food packaging field.

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