Polyester film and method for producing same

Abstract

The invention discloses a polyester film and a manufacturing method thereof. The manufacturing method of the polyester film is used for recycling a recycled plastic, and comprises the following steps: physically reproducing a part of the recycled plastic to obtain a physically recycled polyester resin; and chemically reproducing the other part of the recycled plastic to obtain a chemically recycled polyester resin. Preparing a polyester composition, wherein the polyester composition comprises physically recycled polyester resin and chemically recycled polyester resin; wherein the total weight of the polyester composition is 100 wt%, and the weight ratio of the chemically recycled polyester resin is greater than or equal to 5 wt%. Forming a polyester film using the polyester composition; wherein, with the total weight of the polyester film being 100 wt%, the total weight of the physically recycled polyester resin and the chemically recycled polyester resin being 10 wt% to 100 wt%.

Description

[0001] This invention is a divisional application, with the parent application having application number 201910880174.4, application date of September 18, 2019, and title "Polyester Film and Method for Manufacturing the Same". Technical Field

[0002] This invention relates to a polyester film and a method for manufacturing the same, and more particularly to a polyester film that uses both physically recycled polyester resin and chemically recycled polyester resin, and a method for manufacturing the same. Background Technology

[0003] In recent years, the use of plastics has increased dramatically, resulting in a large amount of plastic waste. Because plastics are not easily decomposed, plastic recycling and post-recycling treatment methods have become extremely important.

[0004] Among recycled plastics, polyethylene terephthalate (PET) is the most abundant, accounting for approximately 52.4% of all recycled plastics. Therefore, the following discussion will focus on PET recycled plastics. Faced with such a large quantity of PET recycled plastics, technicians in related fields have had to dedicate themselves to developing methods for processing PET recycled plastics.

[0005] The most common PET recycling method in the current technology is to recycle PET through physical (mechanical) means. First, the cleaned recycled PET plastic is cut into fragments, melted at high temperature, and extruded through an extruder to produce PET recycled pellets (also known as r-PET).

[0006] To maintain a high proportion of environmentally friendly recyclable PET pellets in PET products while adhering to environmental protection requirements, a large quantity of high-quality recycled PET pellets is needed. Currently, most industries use physical recycling methods to recycle PET, but the recycled pellets produced cannot incorporate functional components such as lubricants and electrostatic adhesives into the physical recycling process. Therefore, it is necessary to use entirely new, non-recycled PET pellets and add additional functional components such as lubricants and electrostatic adhesives.

[0007] However, this would reduce the percentage of recycled PET pellets used in PET products. In other words, current technology cannot fully utilize recycled PET pellets to manufacture new PET products. If the percentage of recycled PET pellets used is too low, it may fail to meet environmental regulations and obtain eco-labels. Furthermore, the PET pellets newly used in the manufacturing process will eventually become recycled plastic awaiting processing, ultimately requiring recycling and reuse. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a polyester film that uses both physically recycled polyester resin and chemically recycled polyester resin, and a method for manufacturing the same, in order to address the shortcomings of the prior art.

[0009] To address the aforementioned technical problems, one technical solution adopted by this invention is to provide a method for manufacturing a polyester film for recycling and reusing recycled plastic. The method includes: physically recycling a portion of the recycled plastic to obtain a physically recycled polyester resin, wherein a first lubricant with a particle size greater than 2 micrometers is added during the physical recycling process; chemically recycling another portion of the recycled plastic to obtain a chemically recycled polyester resin, wherein the chemical recycling process includes depolymerizing the other portion of the recycled plastic to obtain a raw material mixture, and adding a second lubricant with a particle size less than 2 micrometers during the repolymerization of the raw material mixture; preparing a polyester composition comprising the physically recycled polyester resin and the chemically recycled polyester resin, wherein the total weight of the polyester composition is 100 wt%, and the weight ratio of the chemically recycled polyester resin is greater than or equal to 5 wt%; and using the polyester composition to form the polyester film, wherein the total weight of the polyester film is 100 wt%, and the total weight of the physically recycled polyester resin and the chemically recycled polyester resin is 10 wt%. The content is from wt% to 100wt%, wherein the haze of the polyester film is less than or equal to 5%, and the transparency is greater than or equal to 85%.

[0010] Preferably, the first lubricant is silica, polystyrene, polymethyl methacrylate, silicone, acrylic, or a combination thereof, and the second lubricant is silica, polystyrene, polymethyl methacrylate, silicone, acrylic, or a combination thereof.

[0011] Preferably, the total weight of the polyester composition is 100 wt%, the content of the physically recycled polyester resin is 10 wt% to 90 wt%, and the content of the chemically recycled polyester resin is 10 wt% to 90 wt%.

[0012] Preferably, during the repolymerization process, a colorant is further added to the raw material mixture; the polyester composition contains 10 ppm to 10 wt% of the colorant.

[0013] Preferably, during the repolymerization process, a white additive is further added to the raw material mixture; the polyester composition contains 5 wt% to 40 wt% of the white additive.

[0014] Preferably, the white additive is selected from at least one of titanium dioxide, barium sulfate, and calcium carbonate.

[0015] Preferably, the white additive comprises titanium dioxide, barium sulfate and calcium carbonate, wherein the titanium dioxide accounts for 0.01 wt% to 80 wt% of the total weight of the white additive, the barium sulfate accounts for 0.01 wt% to 80 wt% of the total weight of the white additive, and the calcium carbonate accounts for 0.01 wt% to 80 wt% of the total weight of the white additive.

[0016] Preferably, during the repolymerization process, an electrostatic adhesive is further added to the raw material mixture, the electrostatic adhesive being a complex containing an alkali metal or an alkaline earth metal.

[0017] Preferably, during the repolymerization process, a biodegradable material is further added to the raw material mixture; the polyester composition contains 5 wt% to 90 wt% of the biodegradable material.

[0018] Preferably, an organic additive is further added during the physical reprocessing process, wherein the organic additive is polyethylene, polypropylene, poly4-methylpentene, or a combination thereof.

[0019] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a polyester film, which is made by the manufacturing method described above; the polyester film has a haze of less than or equal to 5% and a transparency of greater than or equal to 85%.

[0020] In summary, the polyester film and its manufacturing method provided by this invention can improve the problem of poor color of polyester products made using recycled polyester resin by means of the technical features of "preparing a polyester composition comprising physically recycled polyester resin and chemically recycled polyester resin" and "the weight proportion of chemically recycled polyester resin being greater than or equal to 5 wt%". Furthermore, according to various needs and applications, different properties of chemically recycled polyester resin can be selected, and polyester films with different properties can be prepared by adjusting the amounts of physically recycled polyester resin and chemically recycled polyester resin.

[0021] To further understand the features and technical content of this invention, please refer to the following detailed description of this invention. Detailed Implementation

[0022] The following are specific examples illustrating the embodiments of the "polyester film and its manufacturing method" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention.

[0023] It should be understood that the term "or" as used in this document may include, depending on the circumstances, any combination of one or more of the related listed items.

[0024] To address the issue of large quantities of recycled plastics, this invention provides a polyester film and its manufacturing method, which is made using recycled polyester resin and has a high recycled polyester resin utilization rate. In this invention's polyester film and manufacturing method, both physically recycled polyester resin obtained through physical reprocessing and chemically recycled polyester resin obtained through chemical reprocessing are used. Furthermore, the polyester film and manufacturing method of this invention can be prepared entirely using recycled polyester resin without the need for additional ester virgin resin.

[0025] First, in order to obtain reusable recycled plastics, after collecting various types of waste plastics, they are sorted according to their type, color, and intended use, and then compressed, packaged, and transported to a processing plant. In this embodiment, the material for recycled plastics is PET, but it is not limited to this.

[0026] Next, the bottle caps, labels, and adhesives are removed from the recycled plastic. After separating other non-recycled plastic objects from the recycled plastic, the recycled plastic is crushed. The bottle necks, liners, and bodies of different materials are then separated using flotation. After drying, the processed bottle flakes are obtained. In other embodiments, the processed bottle flakes can also be purchased directly.

[0027] Then, the present invention physically reprocesses a portion of the bottle flakes to obtain physically recycled polyester resin, and chemically reprocesses another portion of the bottle flakes to obtain chemically recycled polyester resin.

[0028] Physical reproduction

[0029] Physical recycling involves first cutting the bottle flakes to reduce the time and energy required for melting them. Next, the cut flakes are melted and mixed. Granulation is then performed using a single-screw or twin-screw extruder to produce physically recycled polyester resin. In other words, the formed bottle flakes are reshaped through a sequence of cutting, melting, and extrusion, causing the polyester molecules in the original flakes to rearrange. It is important to note that during physical recycling, the polyester molecules only rearrange, not reassemble; components originally present in the recycled plastic (such as metal catalysts, lubricants, antioxidants, or additives used in polyester synthesis) remain in the physically recycled polyester resin.

[0030] Additionally, during the physical recycling process, an organic additive can be added to produce physically recycled polyester resin. In the manufacturing process, the PET polyester resin and the organic additive form incompatible intracellular pores in the membrane, resulting in a white, hazy optical property in the PET film and a decrease in the density of the polyester film. This organic additive is, for example, but not limited to, polyethylene (PE), polypropylene (PP), poly(4-methylpentene) (TRX), or combinations thereof.

[0031] Alternatively, a lubricant may be added during the physical reprocessing process. The lubricant may be, but is not limited to, silica, polystyrene, polymethyl methacrylate, silicone, acrylic, or combinations thereof, and the particle size of the lubricant is greater than 2 micrometers.

[0032] Chemical reprocessing

[0033] The chemical recycling process involves first cutting the bottle flakes to reduce the time and energy required for depolymerization. Next, the flakes are immersed in a chemical depolymerization solution to break down the polyester molecules, thereby depolymerizing them and obtaining polyester monomers and oligomers with shorter molecular chains. In this embodiment, the chemical depolymerization solution may be a solution containing formic acid, methanol, acetic acid, ethanol, ethylene glycol, propionic acid, malonic acid, acetone, butanone, toluene, or combinations thereof, but is not limited thereto. In a preferred embodiment, the chemical depolymerization solution includes ethylene glycol. Furthermore, to reduce the impurity content in the chemically recycled polyester resin, the recycled plastic can be depolymerized under vacuum to remove vaporized or volatile organic impurities, resulting in a raw material mixture.

[0034] Next, the raw material mixture undergoes a separation and purification step to increase the content of monomers and / or oligomers in the mixture. Under specific reaction conditions, the monomers and / or oligomers in the raw material mixture are repolymerized to obtain chemically recycled polyester resin. In other words, during the chemical recycling process, polyester molecules can be depolymerized into smaller molecules and further recombine and polymerize into new polyester molecules.

[0035] In other embodiments, the preparation method of chemically recycled polyester resin is not limited to the above, and it can also be obtained by hydrolysis or supercritical fluid method. Hydrolysis involves placing the resin flakes in an alkaline solution, controlling the temperature and pressure, and irradiating with microwaves to completely decompose the polyester molecules into monomers. Supercritical fluid method involves decomposing the polyester into small amounts of monomers and oligomers in supercritical methanol; the yields of monomers and oligomers are affected by the reaction temperature and reaction time.

[0036] Furthermore, during the repolymerization process, appropriate additives may be added to the raw material mixture to adjust the properties of the chemically recycled polyester resin (e.g., slip, electrostatic adhesion, haze, color, degradation and / or strength).

[0037] For example, during the repolymerization process, the lubricity and optical properties of chemically recycled polyester resin can be improved by adding a lubricant to the raw material mixture to obtain a chemically recycled polyester resin that meets specific transparency requirements. The lubricant can be, but is not limited to, silica, polystyrene (PS), polymethyl methacrylate (PMMA), silicone, acrylic, or combinations thereof. In this embodiment, the lubricant is spherical, thus exhibiting better light transmittance. Furthermore, the particle size of the lubricant is less than 2 micrometers.

[0038] During the repolymerization process, the haze of the chemically recycled polyester resin can be adjusted by adding a haze additive to the raw material mixture to obtain a chemically recycled polyester resin that meets specific haze requirements. The haze additive can be, but is not limited to, silica, organic matter, silicone, acrylic, or combinations thereof. In a preferred embodiment, the haze additive is spherical, which can increase light scattering.

[0039] During the repolymerization process, the color of the chemically recycled polyester resin can be adjusted by adding colorants to the raw material mixture to meet the requirements of various polyester products. For example, adding a black colorant can produce a black chemically recycled polyester resin. In addition to colorants, additives that are themselves colored can also be added. For instance, a white chemically recycled polyester resin can be produced by adding a white additive.

[0040] The white additive can be a white inorganic substance, such as, but not limited to, titanium dioxide, barium sulfate, calcium carbonate, or combinations thereof. The addition of the white additive, besides adjusting the color of the chemically recycled polyester resin, may also affect the physical properties of the polyester film. For example, the amount of titanium dioxide added affects the haze of the polyester film, while the amounts of barium sulfate and calcium carbonate added affect the surface gloss of the polyester film. In a preferred embodiment, the white additive simultaneously comprises titanium dioxide, barium sulfate, and calcium carbonate, with titanium dioxide accounting for 0.01 wt% to 80 wt% of the total weight of the white additive, barium sulfate accounting for 0.01 wt% to 80 wt% of the total weight of the white additive, and calcium carbonate accounting for 0.01 wt% to 80 wt% of the total weight of the white additive.

[0041] During the repolymerization process, the amount of plastic requiring future disposal can be reduced by adding biodegradable materials to the raw material mixture. Biodegradable materials can be biopolymers, natural materials, or mixtures thereof. Specifically, biopolymers can be, but are not limited to: starch, cellulose, chitin, polylactic acid (PLA), polyglycolic acid (PGA), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxycaproate (PHC), polyhydroxyheptanoate (PHH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene succinate / adipate copolymer (PBSA), and polybutylene succinate / butylene terephthalate copolymer (PBSA). Natural materials may include, but are not limited to: natural rubber, lignin, coffee, tea, cocoa, lemongrass, rice, flowers, turmeric, leaves, wood, sugarcane, coconut shell, corn, seeds, sweet potato, grapefruit peel, or mixtures thereof. Other natural materials may include, but are not limited to: natural rubber, lignin, coffee, tea, cocoa, lemongrass, rice, flowers, turmeric, leaves, wood, sugarcane, coconut shell, corn, seeds, sweet potato, grapefruit peel, or mixtures thereof.

[0042] Accordingly, various chemically recycled polyester resins with different properties can be prepared using the aforementioned additives. Furthermore, through the two different processes of physical and chemical reprocessing, physically recycled polyester resins and chemically recycled polyester resins with different properties can be obtained. Therefore, by selecting a specific type of chemically recycled polyester resin and adjusting the proportions of physically and chemically recycled polyester resins, it is beneficial to subsequently manufacture different polyester products, such as polyester films.

[0043] Following the physical and chemical recycling steps, this invention utilizes physically and chemically recycled polyester resins to prepare a polyester composition. The polyester composition includes both physically and chemically recycled polyester resins, and by adjusting the specific proportions of these resins, it can be used to prepare various polyester products. To maintain the appearance and color of the polyester product, the total weight of the recycled polyester resin is 100 wt%, and the weight proportion of the chemically recycled polyester resin is greater than or equal to 5 wt%. Furthermore, chemically recycled polyester resins with different properties can be selected according to the requirements and applications of the polyester film.

[0044] For example, when preparing a transparent polyester film, a specific chemically or physically recycled polyester resin can be used as a base, so that the polyester composition (including physically recycled polyester resin and chemically recycled polyester resin) contains 0.01 wt% to 1 wt% of lubricant. That is, after mixing the lubricant into the chemically recycled polyester resin, the amounts of the chemically and physically recycled polyester resins are adjusted to ensure that the polyester composition contains 0.01 wt% to 1 wt% lubricant. In this embodiment, the transparency of the resulting transparent polyester film is greater than or equal to 85%. By further adjusting the added components and content of the lubricant, the haze of the polyester film can be less than or equal to 5%.

[0045] When preparing multi-colored polyester films, specific chemically or physically recycled polyester resins can be used as a base, allowing the polyester composition to contain 10 ppm to 10 wt% colorant. For example, when preparing a black polyester film, the polyester composition can contain 10 ppm to 10 wt% black colorant. In addition to colorants, other colored additives can also be included in the polyester composition when preparing multi-colored polyester films. For example, to prepare a white polyester film, the polyester composition can contain 5 wt% to 40 wt% white additives. As mentioned earlier, the haze and surface gloss of the polyester film are also affected by the proportion of white additives. In a preferred embodiment, the total weight of white additives is 100 wt%, the content of titanium dioxide is 0.01 wt% to 80 wt%, the content of barium sulfate is 0.01 wt% to 80 wt%, and the content of calcium carbonate is 0.01 wt% to 80 wt%.

[0046] When preparing a matte polyester film, a specific chemically or physically recycled polyester resin can be used as a base to include 500 ppm to 20 wt% of matte additives in the polyester composition. The matte additives can exist in particulate form, thereby producing a matte polyester film with a haze of 0.1% to 90%.

[0047] When preparing biodegradable polyester films, specific chemically or physically recycled polyester resins can be used as a base to include 5 wt% to 90 wt% of biodegradable materials in the polyester composition, thereby improving the degradation characteristics of the biodegradable polyester film.

[0048] Beneficial effects of the embodiments

[0049] One of the beneficial effects of this invention is that the polyester film and its manufacturing method provided by this invention can improve the problem of poor color of polyester products made using recycled polyester resin by means of the technical features of "preparing a polyester composition comprising physically recycled polyester resin and chemically recycled polyester resin" and "the weight ratio of chemically recycled polyester resin being greater than or equal to 5 wt%". Furthermore, according to various needs and applications, different properties of chemically recycled polyester resin can be selected, and by adjusting the amounts of physically recycled polyester resin and chemically recycled polyester resin, polyester films with different properties can be prepared.

[0050] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the claims of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification are included within the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a polyester film for recycling and reusing recycled plastics, characterized in that, The method for manufacturing the polyester film includes: The recycled plastic is physically recycled to obtain a physically recycled polyester resin; wherein a first lubricant is added during the physical recycling process, the first lubricant having a particle size greater than 2 micrometers; The recycled plastic is chemically recycled to obtain a chemically recycled polyester resin; wherein the chemical recycling process includes depolymerizing the recycled plastic to obtain a raw material mixture, and adding a second lubricant, the second lubricant having a particle size of less than 2 micrometers, during the repolymerization of the raw material mixture. Prepare a polyester composition comprising the physically recycled polyester resin and the chemically recycled polyester resin; wherein the total weight of the polyester composition is 100 wt%, and the weight proportion of the chemically recycled polyester resin is greater than or equal to 5 wt%; and The polyester film is formed using the polyester composition, wherein the total weight of the polyester film is 100 wt%, and the total weight of the physically recycled polyester resin and the chemically recycled polyester resin is from 10 wt% to 100 wt%. The polyester film has a haze of less than or equal to 5% and a transparency of greater than or equal to 85%.

2. The method for manufacturing polyester film according to claim 1, characterized in that, The first lubricant is silica, polystyrene, polymethyl methacrylate, silicone, acrylic, or a combination thereof, and the second lubricant is silica, polystyrene, polymethyl methacrylate, silicone, acrylic, or a combination thereof.

3. The method for manufacturing the polyester film according to claim 1, characterized in that, With a total weight of 100 wt% for the polyester composition, the content of the physically recycled polyester resin is 10 wt% to 90 wt%, and the content of the chemically recycled polyester resin is 10 wt% to 90 wt%.

4. The method for manufacturing the polyester film according to claim 1, characterized in that, During the repolymerization process, a colorant is further added to the raw material mixture; wherein the polyester composition contains 10 ppm to 10 wt% of the colorant.

5. The method for manufacturing a polyester film according to claim 1, characterized in that, During the repolymerization process, a white additive is further added to the raw material mixture; wherein the polyester composition contains 5 wt% to 40 wt% of the white additive.

6. The method for manufacturing a polyester film according to claim 5, characterized in that, The white additive is selected from at least one of titanium dioxide, barium sulfate, and calcium carbonate.

7. The method for manufacturing a polyester film according to claim 6, characterized in that, The white additive comprises titanium dioxide, barium sulfate, and calcium carbonate, wherein the titanium dioxide accounts for 0.01 wt% to 80 wt% of the total weight of the white additive, the barium sulfate accounts for 0.01 wt% to 80 wt% of the total weight of the white additive, and the calcium carbonate accounts for 0.01 wt% to 80 wt% of the total weight of the white additive.

8. The method for manufacturing a polyester film according to claim 1, characterized in that, During the repolymerization process, an electrostatic adhesive is further added to the raw material mixture, the electrostatic adhesive being a complex containing an alkali metal or an alkaline earth metal.

9. The method for manufacturing a polyester film according to claim 1, characterized in that, During the repolymerization process, a biodegradable material is further added to the raw material mixture; wherein the polyester composition comprises 5 wt% to 90 wt% of the biodegradable material.

10. The method for manufacturing a polyester film according to claim 1, characterized in that, In the physical reprocessing process, an organic additive is further added, wherein the organic additive is polyethylene, polypropylene, poly4-methylpentene, or a combination thereof.

11. A polyester film, characterized in that, The polyester film is produced by the manufacturing method according to any one of claims 1 to 10, wherein the polyester film has a haze of less than or equal to 5% and a transparency of greater than or equal to 85%.