PCR-PET (Polymerase Chain Reaction-Polyethylene Terephthalate) polyester film with excellent mechanical property and thermal stability and preparation method thereof

Abstract

The invention discloses a PCR-PET (Polymerase Chain Reaction-Polyethylene Terephthalate) polyester film with excellent mechanical property and thermal stability and a preparation method thereof, and belongs to the field of preparation of organic high-molecular compounds. Comprising the following components in parts by weight: 80-99 parts of PCR-PET slices and 1-20 parts of copolyester master batches, wherein the PCR-PET slice is prepared by granulating a PET beverage bottle which is recycled after consumption; the copolyester master batch contains an amide structure. Polyester beverage bottles recycled after consumption are taken as raw materials, PCR-PET (Polymerase Chain Reaction-Polyethylene Terephthalate) chips are obtained through crushing, cleaning and extrusion granulation, a copolyester master batch containing an amide structure on a molecular main chain is synthesized by adopting a copolymerization method, the master batch and the PCR-PET chips are blended and extruded, and the polyester beverage bottles are prepared. The PCR-PET polyester film with excellent mechanical property and high thermal stability is prepared; in addition, the film is transparent and does not become yellow, the appearance of the film is free of defects such as crystal points and gel, and the product quality of recycled PET plastic is greatly improved. The method is simple in preparation process, simple and convenient in procedure, easy to operate and high in practicability.

Description

Technical Field

[0001] The invention belongs to the field of preparation of organic polymer compounds, and specifically relates to a PCR-PET polyester film with excellent mechanical properties and thermal stability and a preparation method thereof. Background Art

[0002] Polyester (PET) is a common plastic with a wide range of uses and excellent performance in life, such as beverage bottles, clothes, packaging films, etc. PCR-PET refers to polyester materials recycled after consumption. PET beverage bottles are one of the main raw materials for producing PCR-PET. Compared with PET raw materials, PCR-PET has disadvantages such as more impurities and low viscosity. This is because the molecular chain breaks and impurities are introduced during the recycling and regranulation process. The polyester film prepared using PCR-PET slices often has poor mechanical properties and thermal stability, and cannot meet the performance indicators of normal products.

[0003] Patent No. CN118082346A discloses an optical reflective film based on PCR-PET and its preparation method. In this patent, the amount of PCR-PET is relatively small (20% to 40%), and a chain extender is used to increase the molecular weight of PCR-PET to improve the mechanical strength of the film, but it is easy to have crystal points and gel points, which affect the appearance of the PCR-PET film; solid phase thickening can increase the viscosity of PCR-PET slices to a certain extent, thereby improving the mechanical properties, but it will also make the color of PCR-PET slices yellowish, and the transparent PCR-PET film prepared in this way will also turn yellow, and the thermal stability of the film is not improved. Patent CN115895208A discloses a PET composite material containing PCR-PET film material and its preparation method and application. In this patent, PCR-PET is a PET film recycled after consumption, and the mechanical properties and crystallization properties of the film are improved mainly by adding glass fiber and nucleating agent. After adding glass fiber to the system, there are problems such as easy clogging of the filter, obvious die swelling, and difficulty in adjusting the film tolerance, and the thermal stability of the film is not improved. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a PCR-PET polyester film having excellent mechanical properties and thermal stability and a preparation method thereof, so as to at least achieve the purpose of improving the mechanical properties and thermal stability of the PCR-PET polyester film.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A PCR-PET polyester film with excellent mechanical properties and thermal stability comprises the following components in parts by weight:

[0007] 80-99 parts of PCR-PET chips and 1-20 parts of copolyester masterbatch;

[0008] Wherein, the PCR-PET slices are made by granulating PET beverage bottles recycled after consumption;

[0009] The structural formula of the copolyester masterbatch is:

[0010]

[0011] Among them, m:n=70~95:5~30.

[0012] The present invention prepares a copolyester masterbatch with an amide structure in the main chain, and the amide structure can form hydrogen bonds between molecular chains, such as: hydrogen bonds are formed between -COOH and terminal hydroxyl -OH in the terminal carboxyl group of PCR-PET and -NH- in the copolyester masterbatch, -NH- in the copolyester masterbatch forms hydrogen bonds with its own -NH-, and -COOH and terminal hydroxyl -OH in the terminal carboxyl group of the copolyester masterbatch form hydrogen bonds with -NH- in the copolyester masterbatch. The formation of the above hydrogen bonds enhances the interaction force between molecular chains, improves the tensile strength, elongation at break and thermal stability of the PCR-PET film, solves the problems of weak mechanical properties and poor thermal stability caused by molecular chain breakage in the preparation process of PCR-PET slices, and the prepared transparent PCR-PET film is not yellowish and has no defects such as crystal points and gel in appearance, thereby greatly improving the product quality of PET plastic recycling and reuse.

[0013] As some possible implementation methods of the present application, the PCR-PET slice preparation steps are as follows:

[0014] A1. Sort the recycled PET beverage bottles, select the transparent PET beverage bottles without adhesive labels (such as Master Kong series, Uni-President series, etc.), use a cutter to remove the middle part of the bottle body, use a crusher to make bottle flakes from the middle part of the bottle body, and then use clean water to wash the bottle flakes;

[0015] A2, drying the bottle flakes prepared in A1, and then extruding and granulating them through a granulator to obtain PCR-PET slices.

[0016] In the above scheme, PET beverage bottles without adhesive labels were selected in the process of preparing PCR-PET slices to reduce the introduction of impurities such as label glue; the middle part of the PET beverage bottle was used to ensure the uniformity of raw material performance.

[0017] As some possible implementation methods of the present application, the drying temperature is 100-160°C, the drying time is 4-8h; and the granulator temperature is 260-290°C.

[0018] As some possible implementation methods of the present application, the copolyester masterbatch has a melting point of 242-252°C and a glass transition temperature of 70-80°C.

[0019] As some possible implementation methods of the present application, the copolyester masterbatch preparation method is as follows:

[0020] B1. Add parabens, p-hydroxyphenylethylamine and sodium methoxide into a container, control the system pressure to be below 3000 Pa in a closed system, then heat to 150-160° C., and after the reaction mixture is completely liquefied, stir for 10-14 hours to obtain a primary product (the primary product at this time is 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, with a purity of 95%-98% and a yield of 96%-99%), then dissolve the primary product in toluene at 70-90° C., and then recrystallize at -20--10° C. to obtain 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide; the reaction process is as follows:

[0021]

[0022] Wherein, R is one of -CH3, -CH2CH3, -CH2CH2CH3, and -CH(CH3)2.

[0023] B2. 1000 parts by mass of terephthalic acid, 348-418 parts by mass of ethylene glycol, 102-617 parts by mass of 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, 0.25-0.35 parts by mass of catalyst, 0.05-0.1 parts by mass of heat stabilizer and 0.05-0.5 parts by mass of antioxidant are added into a reactor, pressurized to 0.2 MPa for reaction, when the temperature in the reactor rises to 230-250°C and the water output is 200-215 parts by mass, the temperature is raised to 275-285°C for polycondensation, and vacuumization is slowly started for 2.5-4 hours, until the residual pressure in the reactor is 20-40 Pa and the resin viscosity is 0.60-0.80 dL / g, nitrogen is charged and discharged to obtain a copolyester masterbatch.

[0024] The structural formula of copolyester masterbatch is:

[0025]

[0026] Among them: m:n=70~95:5~30.

[0027] As some feasible embodiments of the present application, in step B1, the molar ratio of the hydroxybenzoic acid esters, p-hydroxyphenylethylamine and sodium methoxide is 1:1:0.1.

[0028] As some feasible embodiments of the present application, in step B1, the paraben is any one of methyl paraben, ethyl paraben, propyl paraben, and isopropyl paraben.

[0029] As some possible implementation methods of the present application, in step B2, the catalyst is antimony trioxide or antimony glycol.

[0030] As some possible implementation methods of the present application, in step B2, the heat stabilizer is triphenyl phosphate or trimethyl phosphate. As some possible implementation methods of the present application, the antioxidant is antioxidant 168 or antioxidant 330 or antioxidant 1790 or antioxidant S-9228.

[0031] As some possible embodiments of the present application, the viscosity of the PET copolyester masterbatch is 0.60 dL / g, 0.65 dL / g, 0.70 dL / g, 0.75 dL / g, or 0.80 dL / g.

[0032] In addition, to achieve the above purpose, the present invention also provides a method for preparing a PCR-PET polyester film having excellent mechanical properties and thermal stability, comprising the following steps:

[0033] S1, drying 80-99 parts by weight of PCR-PET chips and 1-20 parts by weight of copolyester masterbatch at a temperature of 150-170° C. for 2-4 hours, then extruding them through an extruder at a temperature of 255-280° C., and then cold-drumming them at a temperature of 10-20° C. to form cast sheets;

[0034] S2. The cast sheet is first longitudinally stretched 3.0±0.5 times at a temperature of 60-90°C, then cooled to 10-25°C for 2-5s, and then transversely stretched 3.0±0.5 times at a temperature of 125±20°C. The biaxially stretched film enters the heat setting zone of the electric heating channel, wherein the temperature of zone one is 200-240°C, the temperature of zone two is 200-240°C, the temperature of zone three is 160-200°C, and the total heat setting time of the three zones of the film is 0.1-0.5min. The film passing through the heat setting zone is then cooled at a temperature of 60-80°C for 0.1-0.5min, then cooled at room temperature, and finally corona rolled to obtain a PCR-PET polyester film.

[0035] As some possible implementation modes of the present application, the thickness of the PCR-PET polyester film is 0.05 to 0.35 mm.

[0036] The beneficial effects of the present invention are:

[0037] The present invention prepares a copolyester masterbatch with an amide structure in the main chain, and the amide structure can form hydrogen bonds between molecular chains, such as: hydrogen bonds are formed between -COOH and terminal hydroxyl -OH in the terminal carboxyl group of PCR-PET and -NH- in the copolyester masterbatch, -NH- in the copolyester masterbatch forms hydrogen bonds with its own -NH-, and -COOH and terminal hydroxyl -OH in the terminal carboxyl group of the copolyester masterbatch form hydrogen bonds with -NH- in the copolyester masterbatch. The formation of the above hydrogen bonds enhances the interaction force between molecular chains, improves the tensile strength, elongation at break and thermal stability of the PCR-PET film, solves the problems of weak mechanical properties and poor thermal stability caused by molecular chain breakage in the preparation process of PCR-PET slices, and the prepared transparent PCR-PET film is not yellowish and has no defects such as crystal points and gel in appearance, thereby greatly improving the product quality of PET plastic recycling and reuse.

[0038] The invention has simple preparation technology, simple process, easy operation and strong practicability. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described in detail below in conjunction with embodiments, but the protection scope of the present invention is not limited to the following.

[0040] Implementation 1

[0041] A method for preparing 4-hydroxy-N-(4-hydroxyphenethyl)benzamide comprises the following steps:

[0042] S1. Add methyl p-hydroxybenzoate, p-hydroxyphenylethylamine and sodium methoxide (the molar ratio of the three is 1:1:0.1) into the container, seal the reaction system, and then use a water pump to evacuate the system to control the pressure below 3000 Pa. Then heat the system to 150°C, and after the reaction mixture is completely liquefied, start stirring, keep the temperature and stir for 12 hours, then stop the reaction to obtain the initial product 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, with a purity of 98% and a yield of 99%.

[0043] S2. The obtained primary product is dissolved in toluene at 80° C., and then recrystallized at -15° C. to obtain the product 4-hydroxy-N-(4-hydroxyphenethyl)benzamide.

[0044] Example 2

[0045] A method for preparing 4-hydroxy-N-(4-hydroxyphenethyl)benzamide comprises the following steps:

[0046] S1. Add propyl p-hydroxybenzoate, p-hydroxyphenylethylamine and sodium methoxide (the molar ratio of the three is 1:1:0.1) into the container, seal the reaction system, and then use a water pump to evacuate the system to control the pressure below 3000 Pa. Then heat the system to 155°C, and after the reaction mixture is completely liquefied, start stirring, keep the temperature and stir for 10 hours, then stop the reaction to obtain the initial product 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, with a purity of 96% and a yield of 97%.

[0047] S2. The obtained product is dissolved in toluene at 75° C., and then recrystallized at -20° C. to obtain the product 4-hydroxy-N-(4-hydroxyphenethyl)benzamide.

[0048] Embodiment 3-10

[0049] A method for preparing a copolyester masterbatch having an amide structure in the main chain, comprising the following steps:

[0050] 1000 parts by weight of terephthalic acid, 348-418 parts by weight of ethylene glycol, 102-617 parts by weight of 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, 0.25-0.35 parts by weight of a catalyst, 0.05-0.1 parts by weight of a heat stabilizer and 0.05-0.5 parts by weight of an antioxidant are added into a reactor, and the reactor is pressurized to 0.2 MPa for reaction; when the temperature in the reactor rises to 230-250° C. and the water output is 200-215 parts by weight, the reactor is heated to 275-285° C. for polycondensation, and vacuum is slowly drawn for 2.5-4 hours until the residual pressure in the reactor is 20-40 Pa and the resin viscosity is 0.60-0.80 dL / g, nitrogen is introduced and the material is discharged to obtain a copolyester masterbatch containing an amide structure in the main chain.

[0051] The material ratios, process parameters, and viscosities of the prepared copolyester masterbatches in Examples 3-10 are shown in Table 1.

[0052] Table 1:

[0053]

[0054] Examples 11-18 and Comparative Examples 1-2

[0055] A method for preparing a PCR-PET polyester film comprises the following steps:

[0056] S1, drying 80-99 parts by weight of PCR-PET chips and 1-20 parts by weight of copolyester masterbatch at a temperature of 150-170° C. for 2-4 hours, then extruding them through an extruder at a temperature of 255-280° C., and then cold-drumming them at a temperature of 10-20° C. to form cast sheets;

[0057] S2. The cast sheet is first longitudinally stretched 3.0±0.5 times at a temperature of 60-90°C, then cooled to 10-25°C for 2-5s, and then transversely stretched 3.0±0.5 times at a temperature of 125±20°C. The biaxially stretched film enters the heat setting zone of the electric heating channel, wherein the temperature of zone 1 is 200-240°C, the temperature of zone 2 is 200-240°C, the temperature of zone 3 is 160-200°C, and the total heat setting time of the three zones of the film is 0.1-0.5min. The film passing through the heat setting zone is then cooled at a temperature of 60-80°C for 0.1-0.5min, then cooled at room temperature, and finally corona rolled to obtain a PCR-PET polyester film with a thickness of 0.05-0.35mm.

[0058] The PCR-PET slice preparation process used in Examples 11-14 is as follows:

[0059] A1. Sort the recycled PET beverage bottles, select the transparent PET beverage bottles without adhesive labels, use a cutter to remove the middle part of the bottle body, use a crusher to make bottle flakes from the middle part of the bottle body, and then use clean water to wash the bottle flakes;

[0060] A2. Dry the bottle slices prepared in A1 at 150°C for 5.5h, and then extrude and granulate them through a granulator at a temperature of 280°C to obtain PCR-PET slices.

[0061] The drying and granulation parameters of the PCR-PET slice preparation process used in Examples 15-18 and Comparative Example 1 were adjusted compared with those of Examples 11-14, and the adjusted parameters were: drying at 100° C. for 8 h and a granulator temperature of 280° C. The other parameters remained unchanged.

[0062] The material ratios and process parameters in Examples 11-18 and Comparative Examples 1-2 are shown in Table 2.

[0063] Table 2:

[0064]

[0065] Note: Only key process parameters are selected for illustration in Table 2. The raw material is the slices produced by China Yizheng Chemical Fiber Co., Ltd., model FG728.

[0066] The mechanical properties of the polyester films (all with a thickness of 0.05 mm) in Examples 11-18 and Comparative Examples 1-2 were tested using an electronic universal testing machine, and the test standard was GB / T 13542.2;

[0067] The thermal stability of the polyester films (all with a thickness of 0.05 mm) in Examples 11-18 and Comparative Examples 1-2 was tested using a thermal gravimetric analyzer (TGA). The test conditions were: temperature range 30-700°C, heating rate 20°C / min, atmosphere: N2, and the thermal stability was evaluated using the 1% thermal decomposition temperature.

[0068] The mechanical properties and thermal stability test results are shown in Table 3.

[0069] Table 3:

[0070]

[0071] It can be seen from Table 3 that the tensile strength, elongation at break and 1% thermal decomposition temperature of the PCR-PET film to which the copolyester masterbatch containing an amide structure is added are significantly improved compared with those of Comparative Example 1, and are equivalent to the performance of the original material (Comparative Example 2). In addition, the PCR-PET films prepared in Examples 11-18 are transparent and not yellowish.

Claims

1. A PCR-PET polyester film having excellent mechanical properties and thermal stability, characterized in that: It includes the following components by weight: 80-99 parts of PCR-PET chips and 1-20 parts of copolyester masterbatch; Wherein, the PCR-PET slices are made by granulating PET beverage bottles recycled after consumption; The structural formula of the copolyester masterbatch is: Among them, m:n=70~95:5~30.

2. A PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 1, characterized in that: The PCR-PET slice preparation steps are as follows: A1. Sort the recycled PET beverage bottles, select the transparent PET beverage bottles without adhesive labels, use a cutter to remove the middle part of the bottle body, use a crusher to make bottle flakes from the middle part of the bottle body, and then use clean water to wash the bottle flakes; A2, drying the bottle flakes prepared in A1, and then extruding and granulating them through a granulator to obtain PCR-PET slices.

3. A PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 2, characterized in that: The drying temperature is 100-160°C, and the drying time is 4-8h; the granulator temperature is 260-290°C.

4. The PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 1, characterized in that: The copolyester masterbatch has a melting point of 242-252°C and a glass transition temperature of 70-80°C.

5. The PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 1, characterized in that: The copolyester masterbatch preparation method is as follows: B1. Add parabens, p-hydroxyphenylethylamine and sodium methoxide into a container, control the system pressure to be below 3000 Pa in a closed system, then heat to 150-160° C., and after the reaction mixture is completely liquefied, stir for 10-14 hours to obtain a primary product, then dissolve the primary product in toluene at 70-90° C., and then recrystallize at -20--10° C. to obtain 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide; B2. 1000 parts by mass of terephthalic acid, 348-418 parts by mass of ethylene glycol, 102-617 parts by mass of 4-hydroxy-N-(4-hydroxyphenylethyl)benzamide, 0.25-0.35 parts by mass of catalyst, 0.05-0.1 parts by mass of heat stabilizer and 0.05-0.5 parts by mass of antioxidant are added into a reactor, pressurized to 0.2 MPa for reaction, when the temperature in the reactor rises to 230-250°C and the water output is 200-215 parts by mass, the temperature is raised to 275-285°C for polycondensation, and vacuumization is slowly started for 2.5-4 hours, until the residual pressure in the reactor is 20-40 Pa and the resin viscosity is 0.60-0.80 dL / g, nitrogen is charged and discharged to obtain a copolyester masterbatch.

6. The PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 5, characterized in that: In step B1, the molar ratio of the hydroxybenzoic acid esters, p-hydroxyphenylethylamine and sodium methoxide is 1:1:0.

1.

7. The PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 5, characterized in that: In step B1, the parahydroxybenzoic acid ester is any one of methyl parahydroxybenzoate, ethyl parahydroxybenzoate, propyl parahydroxybenzoate and isopropyl parahydroxybenzoate.

8. The PCR-PET polyester film having excellent mechanical properties and thermal stability according to claim 5, characterized in that: In step B2, the catalyst is antimony trioxide or antimony glycol.

9. The method for preparing copolyester masterbatch according to claim 5, characterized in that: In step B2, the thermal stabilizer is triphenyl phosphate or trimethyl phosphate.

10. The method for preparing a PCR-PET polyester film having excellent mechanical properties and thermal stability according to any one of claims 1 to 9, characterized in that: The steps include: S1, drying 80-99 parts by weight of PCR-PET chips and 1-20 parts by weight of copolyester masterbatch at a temperature of 150-170° C. for 2-4 hours, then extruding them through an extruder at a temperature of 255-280° C., and then cold-drumming them at a temperature of 10-20° C. to form cast sheets; S2. The cast sheet is first longitudinally stretched 3.0±0.5 times at a temperature of 60-90°C, then cooled to 10-25°C for 2-5s, and then transversely stretched 3.0±0.5 times at a temperature of 125±20°C. The biaxially stretched film enters the heat setting zone of the electric heating channel, wherein the temperature of zone one is 200-240°C, the temperature of zone two is 200-240°C, the temperature of zone three is 160-200°C, and the total heat setting time of the three zones of the film is 0.1-0.5min. The film passing through the heat setting zone is then cooled at a temperature of 60-80°C for 0.1-0.5min, then cooled at room temperature, and finally corona rolled to obtain a PCR-PET polyester film.

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