CN110724369B - Modified PET (polyethylene terephthalate) film for lithium battery flexible packaging film - Google Patents
Modified PET (polyethylene terephthalate) film for lithium battery flexible packaging film Download PDFInfo
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- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
- C08G63/181—Acids containing aromatic rings
- C08G63/183—Terephthalic acids
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B5/00—Drying solid materials or objects by processes not involving the application of heat
- F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
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- C08J2471/00—Characterised by the use of polyethers obtained by reactions forming an ether link in the main chain; Derivatives of such polymers
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Abstract
The invention discloses a modified PET film for a lithium battery flexible packaging film, which comprises the following components in parts by weight: 70-80 parts of terephthalic acid, 150 parts of ethylene glycol 120-montmorillonite, 10.5-32.4 parts of nano-montmorillonite, 0.5-10 parts of dispersant and 0.1-20 parts of coupling agent; the preparation method of the modified PET film comprises the steps of firstly carrying out esterification reaction on terephthalic acid and ethylene glycol to generate low-polymerization-degree polyethylene terephthalate, carrying out polycondensation reaction on the low-polymerization-degree polyethylene terephthalate, and carrying out lamellar distribution of nano montmorillonite in PET under the action of a dispersing agent and a coupling agent in the polycondensation reaction process to obtain the modified PET, so that the problem of poor barrier property of the traditional PET film is solved.
Description
Technical Field
The invention belongs to the technical field of modified polyester, and particularly relates to a modified PET (polyethylene terephthalate) film for a lithium battery flexible packaging film.
Background
Polyethylene terephthalate is an important engineering plastic, has excellent physical and mechanical properties in a wide temperature range, can still maintain excellent electrical insulation performance at high temperature and high frequency, and PET materials produced by the polyethylene terephthalate are widely applied to various industries such as electronics, food, medicine, office supplies, toys and the like. However, since the PET material itself has problems such as poor gas barrier property, which limits the application of the PET material in many aspects, it is necessary to modify the PET material to some extent in order to obtain a PET material with wider application.
The main ways of modifying plastics today are: on the basis of general plastics and engineering plastics, the plastics are processed and modified by filling, blending, reinforcing and other methods, so that the performance of the plastics is improved. Along with the continuous development and perfection of nanotechnology in recent years, various technical means are adopted to add inorganic nanoparticles into PET materials, so that the problems of poor gas barrier property and the like of the PET materials are solved;
however, due to problems such as material selection and process, inorganic nanoparticles cannot be dispersed in PET materials, and improvement of gas barrier properties of PET materials is not desirable. The polymer/montmorillonite nano composite material is the most potential composite material in a plurality of inorganic nano particle modified composite materials, but montmorillonite has oleophobic property due to a large amount of inorganic ions between layers, and the characteristic is unfavorable for the dispersion and uneven dispersion in a polymer matrix.
Disclosure of Invention
The invention aims to provide a modified PET film for a lithium battery flexible packaging film, which aims to solve the problems that the gas barrier property of a PET material is poor and the like in the background.
The technical problems to be solved by the invention are as follows:
(1) how to solve the problem of poor PET gas barrier property.
(2) How to solve the modification problem of the nano montmorillonite.
(3) How to solve the problem of compounding the nano montmorillonite and the PET.
In order to achieve the purpose, the invention provides the following technical scheme:
a modified PET film for a lithium battery flexible packaging film is composed of the following components in parts by weight: 70-80 parts of terephthalic acid, 150 parts of ethylene glycol 120-montmorillonite, 10.5-32.4 parts of nano-montmorillonite, 0.5-10 parts of dispersant and 0.1-20 parts of coupling agent;
preferably, the preparation method of the modified PET film comprises the following steps:
s1, placing the nano montmorillonite, the dispersing agent and the coupling agent, and the terephthalic acid and the ethylene glycol into a reaction kettle, and carrying out esterification reaction on the terephthalic acid and the ethylene glycol to obtain polyethylene glycol terephthalate with low polymerization degree;
s2, carrying out polycondensation reaction on polyethylene glycol terephthalate with low polymerization degree in a reaction kettle, and distributing the nano montmorillonite in the PET in a lamellar manner under the action of a dispersing agent and a coupling agent in the polycondensation process to obtain modified PET; the modification mode solves the problem that the nano montmorillonite can not be uniformly distributed and combined with the nano montmorillonite.
And S3, extruding the modified PET through a T-shaped die head of an extruder, quenching the cooling liquid, and biaxially stretching the cooled cooling liquid through a tenter to obtain the modified PET film.
Preferably, when the terephthalic acid and the ethylene glycol are subjected to esterification reaction, the temperature of a reaction kettle is 192-; when the low-polymerization-degree polyethylene terephthalate is subjected to polycondensation reaction, the temperature of the reaction kettle is 245-278 ℃ and the pressure is 28-43 Pa.
Preferably, the dispersant is polyethylene glycol; the coupling agent is N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane.
Preferably, the extrusion temperature of the extruder is 274-286 ℃, and the rotating speed of the screw is 32-36 rpm; the longitudinal stretching temperature of the tenter is 84-88 ℃, the longitudinal stretching ratio is 2.85-3.1 times, the transverse stretching temperature is 104-118 ℃, the transverse stretching ratio is 2.6-3.4 times, and the heat setting temperature is 234-236 ℃.
Preferably, the preparation of the nano montmorillonite comprises the following steps:
the method comprises the following steps: taking 30-40g of sodium bentonite, adding 400-500ml of water, stirring for 5-10min to fully dissolve the sodium bentonite, and removing impurities to obtain a first product of the nano montmorillonite;
step two: placing the first product of nano montmorillonite in 500ml beaker, heating with electric hot plate, stirring continuously during heating, adding 15-20ml 50% Na at 65-78 deg.C2CO3Stirring the solution for 30-50min, and standing for 18-24h to obtain a second product of the nano montmorillonite;
step three: pouring the second product of the nano montmorillonite into a centrifuge tube, performing centrifugal sedimentation by a centrifuge, removing supernatant, washing by water, and performing centrifugal sedimentation until a layer of semitransparent soil gel is obtained, namely a third product of the nano montmorillonite;
step four: mixing the third product of the nano montmorillonite with water in a beaker, stirring by using a stirrer, performing ultrasonic treatment to form a stable suspension system, and standing for 40-60min to obtain a fourth product of the nano montmorillonite;
step five: heating the beaker filled with the fourth product of the nano montmorillonite on a heating plate, stirring and adding the intercalating agent when the temperature is 60-80 ℃, stirring for 10-20min by using a stirrer, and carrying out ultrasonic treatment for 30-50min to obtain a fifth product of the nano montmorillonite;
step six: and (3) heating the fifth product of the nano montmorillonite on an electric heating plate, stirring at the temperature of 60-80 ℃, adding a water-soluble polymer surfactant, centrifuging in a centrifuge, and freeze-drying to obtain the nano montmorillonite. The nano montmorillonite is modified by firstly using an aqueous solution of an intercalating agent octadecylamine hydrochloride, then using a water-soluble high-molecular surfactant polyvinylpyrrolidone, and freeze-drying to obtain the loose nano montmorillonite with large interlayer spacing, and the nano montmorillonite in the state can more easily complete the modification of PET while the low-polymerization-degree polyethylene glycol terephthalate is subjected to polycondensation reaction.
Preferably, the rotating speed of the centrifugal machine is 10000rpm, and the centrifugal time is 20-30 min.
Preferably, the rotor speed of the stirrer is 800 rpm.
Preferably, the water-soluble polymer surfactant is polyvinylpyrrolidone; the intercalating agent is an aqueous solution of octadecyl amine hydrochloride.
Preferably, the freeze drying equipment comprises an outer shell and an inner shell, a vacuum state is pumped between the outer shell and the inner shell, a raw material groove, a raw material control valve and a raw material pressure pump are installed at the top end of the outer shell, the raw material groove, the raw material control valve and the raw material pressure pump are connected with the outer shell and the inner shell through inlet pipes, a vacuum pump and a vacuum control valve which are symmetrical relative to the inlet pipes are installed on two sides of the upper part of the outer shell, the vacuum pump and the vacuum pump control valve are connected with the outer shell through exhaust pipes, one end of each exhaust pipe is connected with the corresponding vacuum pump control valve, the other end of each exhaust pipe is connected with the corresponding inlet pipe, the other end of each exhaust pipe is of a slope-shaped structure, a vacuum drying chamber is arranged inside the inner shell, fixing frames are arranged on two sides of the middle position of the vacuum drying chamber, a condensation plate is fixed between the two fixing frames, the fixing frames are movably connected with the condensation plate, and a drying plate is installed on the upper surface of the condensation plate, the drying plate is welded on two sides with a fixing plate, a rotating rod is welded and fixed in the center of the fixing plate, the rotating rod is movably connected with supporting legs welded on the surface of the inner wall of the inner shell, a liquid inlet and a liquid outlet are mounted on the condensing disc, the condensing disc is connected with the liquid inlet and the liquid outlet through condensing hoses, a condenser control valve is connected with the condenser, the condenser is mounted on one side of the outer shell, the condenser is arranged below the fixing frame, a liquid nitrogen storage tank and a liquid nitrogen control valve are mounted on the other side of the outer shell, the liquid nitrogen storage tank and the liquid nitrogen control valve are connected with the outer shell through air inlet pipes, the air inlet pipes are mounted at positions between the drying plate and the feeding pipe orifices, the fixing frame is mounted and fixed on the other side of the feeding pipe orifices, and a storage box is arranged at the bottom of the inner shell;
when the freeze drying equipment works, a raw material control valve and a raw material pressure pump are opened, nano montmorillonite to be subjected to freeze drying is stored in a raw material tank through a feed pipe and is sprayed onto the surface of a drying plate through the feed pipe, a liquid nitrogen storage tank and a liquid nitrogen control valve are opened firstly, the raw material is frozen, then a condenser and a condenser control valve are opened, a vacuum pump and a vacuum pump control valve are opened, after water is sublimated and dried, the drying plate pours the nano montmorillonite subjected to freeze drying on the surface of the drying plate into a storage box through a rotating rod, the temperature is-15 ℃ to-45 ℃ in the freeze drying process, and the freezing pressure is 1.3Pa to 12.6 Pa.
The invention has the beneficial effects that:
(1) the PET material is modified by using the nano-montmorillonite, when the sodium bentonite is purified, ion exchange is used, and continuous high-speed centrifugation, standing, stirring and the like are performed, so that the obtained nano-montmorillonite is higher in purity, the particle size of particles is uniform and smaller, the water solution of the octadecyl amine hydrochloride serving as an intercalation agent is used after purification, the polyvinylpyrrolidone serving as a water-soluble high-molecular surfactant is used, and the nano-montmorillonite in a loose state and large in interlayer spacing is obtained after freeze drying, so that the compounding of a polymer and the nano-montmorillonite later is facilitated.
(2) According to the freeze drying equipment designed by the invention, the exhaust pipe is arranged in a slope shape, the tip end of the exhaust pipe is welded with the feeding pipe, the loss caused by the fact that the nano montmorillonite is pumped into the vacuum pump when the vacuum pump works is avoided, the temperature in the vacuum drying chamber can be reduced to-15 ℃ to-45 ℃ in a very short time, the nano montmorillonite is rapidly frozen, the structure of the nano montmorillonite is protected to the maximum extent, the condensation disc is connected with the drying plate, the temperature can be rapidly transferred to the frozen nano montmorillonite, the water in the nano montmorillonite is increased rapidly, and the re-drying process of the nano montmorillonite is facilitated.
(3) The PET material is modified by using the nano-montmorillonite, esterification reaction is firstly carried out in the reaction of terephthalic acid and ethylene glycol to generate low-polymerization-degree polyethylene terephthalate, the low-polymerization-degree polyethylene terephthalate is then subjected to polycondensation reaction to obtain PET, and the nano-montmorillonite is laminarly distributed in the PET under the action of a dispersing agent and a coupling agent during the polycondensation reaction to obtain the modified PET. The modified PET obtained by the method can be directly and uniformly combined with the nano-montmorillonite, and the problem of poor gas barrier property of the PET material is effectively solved, so that the modified PET material with excellent barrier property is obtained.
Drawings
FIG. 1 is a schematic structural diagram of a main body of a freeze drying apparatus;
FIG. 2 is a schematic diagram of a drying plate structure;
FIG. 3 is a schematic view of a condensation plate;
in the figure: 1. a raw material tank; 2. a raw material control valve; 3. a raw material pressure pump; 4. a housing; 5. an inner shell; 6. a vacuum pump; 7. a vacuum drying chamber; 8. a fixed mount; 9. a storage box; 10. drying the plate; 11. a condensation pan; 111. a liquid inlet; 112. a liquid discharge port; 12. a liquid nitrogen storage tank; 13. a liquid nitrogen control valve; 14. a vacuum pump control valve; 15. supporting legs; 16. rotating the rod; 17. a fixing plate; 18. a condenser; 19. a condenser control valve.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1 to 3, a modified PET film for a flexible packaging film of a lithium battery is composed of the following components in parts by weight: 71.5 parts of terephthalic acid, 130 parts of ethylene glycol, 12.4 parts of nano montmorillonite, 5.4 parts of polyethylene glycol and 4.8 parts of N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane;
the preparation method of the modified PET film comprises the following steps:
s1, putting the nano montmorillonite, the dispersant and the coupling agent, and the terephthalic acid and the ethylene glycol into a reaction kettle, wherein the temperature of the reaction kettle is 195.5 ℃, the pressure of the reaction kettle is 0.34MPa, and the terephthalic acid and the ethylene glycol are subjected to esterification reaction to obtain polyethylene glycol terephthalate with low polymerization degree;
and S2, carrying out polycondensation reaction on the polyethylene glycol terephthalate with low polymerization degree in nano montmorillonite at the temperature of 256 ℃ and the pressure of 32Pa in the reaction kettle, wherein the nano montmorillonite is distributed in the PET in a lamellar manner under the action of polyethylene glycol and N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane in the polycondensation reaction process, so as to obtain the modified polyethylene glycol terephthalate with high polymerization degree, namely the modified PET.
S3, extruding the modified PET through a T-shaped die of an extruder with the extrusion temperature of 279 ℃ and the screw rotation speed of 35rpm, quenching the extruded modified PET through cooling liquid, and performing biaxial tension through a tenter to obtain a modified PET film; the longitudinal stretching temperature was 85.5 ℃, the longitudinal stretching ratio was 2.93 times, the transverse stretching temperature was 105 ℃, the transverse stretching ratio was 2.7 times, and the heat-setting temperature was 234 ℃.
The preparation of the nano montmorillonite comprises the following steps:
the method comprises the following steps: taking 32g of sodium bentonite, adding 420ml of water, stirring for 6min to fully dissolve the sodium bentonite, and removing impurities to obtain a first product of the nano montmorillonite;
step two: placing the first product of nano montmorillonite in 500ml beaker, heating with electric hot plate, stirring continuously during heating, and adding 17ml 50% Na at 72 deg.C2CO3Stirring the solution for 40min, and standing for 20h to obtain a second product of the nano montmorillonite;
step three: pouring the second product of the nano montmorillonite into a centrifuge tube, centrifuging and settling by a centrifuge, removing supernatant, cleaning by water, centrifuging and settling for 25min until a layer of semitransparent clay gel is obtained, namely a third product of the nano montmorillonite;
step four: mixing the third product of the nano montmorillonite with water in a beaker, stirring by using a stirrer with the rotating speed of a rotor of 800rpm, performing ultrasonic treatment to form a stable suspension system, and standing for 48min to obtain a fourth product of the nano montmorillonite;
step five: heating a beaker filled with a fourth product of the nano montmorillonite on a heating plate, stirring and adding an aqueous solution of octadecylamine hydrochloride when the temperature is 62 ℃, stirring for 15min by using a stirrer with a rotor rotating speed of 800rpm, and carrying out ultrasonic treatment for 30min to obtain a fifth product of the nano montmorillonite;
step six: heating the fifth product on an electric heating plate, stirring at 63 deg.C, adding water-soluble polymer surfactant polyvinylpyrrolidone, centrifuging at 10000rpm for 22 min; the freeze drying equipment comprises an outer shell 4 and an inner shell 5, a vacuum state is pumped between the outer shell 4 and the inner shell 5, a raw material groove 1, a raw material control valve 2 and a raw material pressure pump 3 are installed at the top end of the outer shell 4, the raw material groove 1, the raw material control valve 2 and the raw material pressure pump 3 are connected with the outer shell 4 and the inner shell 5 through a feeding pipe, a vacuum pump 6 and a vacuum pump control valve 14 which are symmetrical relative to the feeding pipe are installed on two sides of the upper portion of the outer shell 4, the vacuum pump 6 and the vacuum pump control valve 14 are connected with the outer shell 4 through an exhaust pipe, one end of the exhaust pipe is connected with the vacuum pump control valve 14, the other end of the exhaust pipe is connected with the feeding pipe, the other end of the exhaust pipe is of a slope-shaped structure, the inside of the inner shell 5 is a vacuum drying chamber 7, fixing frames 8 are arranged on two sides of the middle position of the vacuum drying chamber 7, a condensing disc 11 is fixed between the two fixing frames 8, and the fixing frames 8 are movably connected with the condensing disc 11, the upper surface of the condensation tray 11 is provided with a drying plate 10, two sides of the drying plate 10 are welded with a fixing plate 17, the central position of the fixing plate 17 is welded and fixed with a rotating rod 16, the rotating rod 16 is movably connected with a supporting leg 15 welded on the inner wall surface of the inner shell 5, the condensation tray 11 is provided with a liquid inlet 111 and a liquid outlet 112, the liquid inlet 111 and the liquid outlet 112 connect the condensation tray 11 through a condensation hose, the condenser control valve 19 is connected with the condenser 18, the condenser 18 is installed on one side of the outer shell 4, the condenser 18 is arranged below the fixing frame 8, the liquid nitrogen storage tank 12 and the liquid nitrogen control valve 13 are installed on the other side of the outer shell 4, the liquid nitrogen storage tank 12 and the liquid nitrogen control valve 13 are connected with the outer shell 4 through air inlet pipes, the air inlet pipes are installed between the drying plate 10 and a feeding pipe opening, the fixing frame 8 is installed and fixed on the other side of the feeding pipe opening, and the bottom of the inner shell 5 is provided with the storage box 9;
when the freeze drying equipment works, the raw material control valve 2 and the raw material pressure pump 3 are opened, nano montmorillonite to be freeze-dried, which is stored in the raw material tank 1 through the feed pipe, is sprayed onto the surface of the drying plate 10 through the feed pipe, the liquid nitrogen storage tank 12 and the liquid nitrogen control valve 13 are opened first, the raw materials are frozen, the condenser 18 (model: HS-C10) and the condenser control valve 19 are opened, the vacuum pump 6 and the vacuum pump control valve 14 are opened, water is sublimated and dried in the freeze drying equipment with the temperature of-25 ℃ and the pressure of 10.6Pa, then the drying plate 10 pours the nano montmorillonite subjected to freeze drying on the surface of the drying plate 10 into the storage box 9 through the rotating rod 16, and the nano montmorillonite is obtained.
The modified PET film was subjected to a gas barrier test.
Example 2
Referring to fig. 1 to 3, a modified PET film for a flexible packaging film of a lithium battery is composed of the following components in parts by weight: 73.5 parts of terephthalic acid, 136.5 parts of ethylene glycol, 21.6 parts of nano montmorillonite, 1.6 parts of polyethylene glycol and 1.8 parts of N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane;
the preparation method of the modified PET film comprises the following steps:
s1, putting the nano montmorillonite, the dispersant and the coupling agent, and the terephthalic acid and the ethylene glycol into a reaction kettle, wherein the temperature of the reaction kettle is 195.6 ℃, the pressure of the reaction kettle is 0.36MPa, and the terephthalic acid and the ethylene glycol are subjected to esterification reaction to obtain polyethylene glycol terephthalate with low polymerization degree;
and S2, carrying out polycondensation reaction on the polyethylene glycol terephthalate with low polymerization degree in nano montmorillonite at the temperature of 264 ℃ and the pressure of 30.5Pa, wherein the nano montmorillonite is distributed in the PET in a lamellar manner under the action of polyethylene glycol and N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane in the polycondensation reaction process, so as to obtain the modified polyethylene glycol terephthalate with high polymerization degree, namely the modified PET.
S3, extruding the modified PET through a T-shaped die of an extruder with the extrusion temperature of 281.5 ℃ and the screw rotation speed of 33rpm, quenching the extruded modified PET through cooling liquid, and performing biaxial tension through a tenter to obtain a modified PET film; the longitudinal stretching temperature is 85.5 ℃, the longitudinal stretching ratio is 2.95 times, the transverse stretching temperature is 106.5 ℃, the transverse stretching ratio is 2.75 times, and the heat setting temperature is 235 ℃.
The preparation of the nano montmorillonite comprises the following steps:
the method comprises the following steps: taking 35.5g of sodium bentonite, adding 450ml of water, stirring for 10min to fully dissolve the sodium bentonite, and removing impurities to obtain a first product of the nano montmorillonite;
step two: placing the first product of nano montmorillonite in 500ml beaker, heating with electric hot plate, stirring continuously during heating, and adding 18ml 50% Na at 72 deg.C2CO3Stirring the solution for 45min, and standing for 22h to obtain a second product of the nano montmorillonite;
step three: pouring the second product of the nano montmorillonite into a centrifuge tube, centrifuging and settling by a centrifuge, removing supernatant, cleaning by water, centrifuging and settling for 30min until a layer of semitransparent clay gel is obtained, namely a third product of the nano montmorillonite;
step four: mixing the third product of the nano montmorillonite with water in a beaker, stirring by using a stirrer with the rotating speed of a rotor of 800rpm, performing ultrasonic treatment to form a stable suspension system, and standing for 48min to obtain a fourth product of the nano montmorillonite;
step five: heating the beaker filled with the fourth product of the nano montmorillonite on a heating plate, stirring and adding an aqueous solution of octadecyl amine hydrochloride when the temperature is 75.5 ℃, stirring for 12min by using a stirrer with a rotor rotating speed of 800rpm, and carrying out ultrasonic treatment for 46min to obtain a fifth product of the nano montmorillonite;
step six: heating the fifth product on an electric heating plate, stirring at 65.5 deg.C, adding water-soluble polymer surfactant polyvinylpyrrolidone, centrifuging at 10000rpm for 30 min; changing the temperature of the freeze drying equipment to-22 ℃ and the pressure to 10.5Pa, and performing freeze drying to obtain the nano montmorillonite by referring to the example 1 in other steps.
The modified PET film was subjected to a gas barrier test.
Example 3
Referring to fig. 1 to 3, a modified PET film for a flexible packaging film of a lithium battery is composed of the following components in parts by weight: 78.5 parts of terephthalic acid, 148.5 parts of ethylene glycol, 20.5 parts of nano montmorillonite, 8.5 parts of polyethylene glycol and 11.5 parts of N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane;
the preparation method of the modified PET film comprises the following steps:
s1, putting the nano montmorillonite, the dispersant and the coupling agent, and the terephthalic acid and the ethylene glycol into a reaction kettle, and carrying out esterification reaction on the terephthalic acid and the ethylene glycol to obtain polyethylene glycol terephthalate with low polymerization degree at the temperature of 195.5 ℃ and the pressure of 0.38MPa in the reaction kettle;
and S2, carrying out polycondensation reaction on the polyethylene glycol terephthalate with low polymerization degree in the nano montmorillonite at the temperature of 262.5 ℃ and under the pressure of 35Pa in the reaction kettle, wherein the nano montmorillonite is distributed in the PET in a lamellar manner under the action of the polyethylene glycol and the N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane in the polycondensation reaction process, so as to obtain the modified polyethylene glycol terephthalate with high polymerization degree, namely the modified PET.
S3, extruding the modified PET through a T-shaped die of an extruder with the extrusion temperature of 285.5 ℃ and the screw rotation speed of 34rpm, quenching the extruded modified PET through cooling liquid, and performing biaxial tension through a tenter to obtain a modified PET film; the longitudinal stretching temperature was 86.5 ℃, the longitudinal stretching ratio was 2.95 times, the transverse stretching temperature was 110.5 ℃, the transverse stretching ratio was 2.8 times, and the heat-setting temperature was 236 ℃.
The preparation of the nano montmorillonite comprises the following steps:
the method comprises the following steps: taking 39.5g of sodium bentonite, adding 460ml of water, stirring for 9min to fully dissolve the sodium bentonite, and removing impurities to obtain a first product of the nano montmorillonite;
step two: placing the first product of nano montmorillonite in 500ml beaker, heating with electric hot plate, stirring continuously during heating, and adding 18ml 50% Na at 75 deg.C2CO3Stirring the solution for 45minStanding for 24h to obtain a second product of the nano montmorillonite;
step three: pouring the second product of the nano montmorillonite into a centrifuge tube, repeatedly centrifuging and settling by a centrifuge, removing supernatant, cleaning by water, centrifuging and settling for 28min until a layer of semitransparent soil gel is obtained, namely a third product of the nano montmorillonite;
step four: mixing the third product of the nano montmorillonite with water in a beaker, stirring by using a stirrer with the rotating speed of a rotor of 800rpm, performing ultrasonic treatment to form a stable suspension system, and standing for 55min to obtain a fourth product of the nano montmorillonite;
step five: heating a beaker filled with a fourth product of the nano montmorillonite on a heating plate, stirring and adding an aqueous solution of octadecylamine hydrochloride when the temperature is 75 ℃, stirring for 20min by using a stirrer with a rotor rotating speed of 800rpm, and carrying out ultrasonic treatment for 45min to obtain a fifth product of the nano montmorillonite;
step six: heating the fifth product on an electric heating plate, stirring at 68 deg.C, adding water-soluble polymer surfactant polyvinylpyrrolidone, centrifuging at 10000rpm for 28 min; changing the temperature of the freeze drying equipment to-36 ℃ and the pressure to 10.8Pa, and performing freeze drying to obtain the nano montmorillonite by referring to the example 1 in other steps.
The modified PET film was subjected to a gas barrier test.
Comparative example 1
The common PET film is prepared without modifying the PET material.
The films were tested for gas barrier properties.
The test results were as follows:
| oxygen permeability cm3/m2·24h·0.1MPa | |
| Example 1 | 1.823 |
| Example 2 | 1.871 |
| Example 3 | 1.868 |
| Comparative example 1 | 51.563 |
TABLE 1
In summary, as can be seen from the data in table 1, the barrier property of the film made of PET modified by the nano-montmorillonite is obviously superior to that of the film made of unmodified PET, so that the barrier property of PET modified by the nano-montmorillonite is obviously improved.
The foregoing is merely exemplary and illustrative of the principles of the present invention and various modifications, additions and substitutions of the specific embodiments described herein may be made by those skilled in the art without departing from the principles of the present invention or exceeding the scope of the claims set forth herein.
Claims (8)
1. A modified PET film for a lithium battery flexible packaging film is characterized in that: the modified PET film comprises the following components in parts by weight: 70-80 parts of terephthalic acid, 150 parts of ethylene glycol 120-montmorillonite, 10.5-32.4 parts of nano-montmorillonite, 0.5-10 parts of dispersant and 0.1-20 parts of coupling agent;
the preparation method of the modified PET film comprises the following steps:
s1, placing the nano montmorillonite, the dispersing agent and the coupling agent, and the terephthalic acid and the ethylene glycol into a reaction kettle, and carrying out esterification reaction on the terephthalic acid and the ethylene glycol to obtain polyethylene glycol terephthalate with low polymerization degree;
s2, carrying out polycondensation reaction on polyethylene glycol terephthalate with low polymerization degree in a reaction kettle, and distributing the nano montmorillonite in the PET in a lamellar manner under the action of a dispersing agent and a coupling agent in the polycondensation process to obtain modified PET;
s3, extruding the modified PET through a T-shaped die head of an extruder, quenching the cooling liquid, and performing biaxial stretching through a tenter to obtain a modified PET film;
the preparation of the nano montmorillonite comprises the following steps:
the method comprises the following steps: taking 30-40g of sodium bentonite, adding 400-500ml of water, stirring for 5-10min to fully dissolve the sodium bentonite, and removing impurities to obtain a first product of the nano montmorillonite;
step two: placing the first product of nano montmorillonite in 500ml beaker, heating with electric hot plate, stirring continuously during heating, adding 15-20ml 50% Na at 65-78 deg.C2CO3Stirring the solution for 30-50min, and standing for 18-24h to obtain a second product of the nano montmorillonite;
step three: pouring the second nano-montmorillonite product into a centrifuge tube of a centrifuge, performing centrifugal sedimentation by the centrifuge, removing supernatant, washing with water, and performing centrifugal sedimentation until a layer of semitransparent soil gel is obtained, namely a third nano-montmorillonite product;
step four: mixing the third product of the nano montmorillonite with water in a beaker, stirring by using a stirrer, performing ultrasonic treatment to form a stable suspension system, and standing for 40-60min to obtain a fourth product of the nano montmorillonite;
step five: heating the beaker filled with the fourth product of the nano montmorillonite on a heating plate, stirring and adding the intercalating agent when the temperature is 60-80 ℃, stirring for 10-20min by using a stirrer, and carrying out ultrasonic treatment for 30-50min to obtain a fifth product of the nano montmorillonite;
step six: placing the fifth product of the nano montmorillonite on an electric heating plate, heating the fifth product at the temperature of 60-80 ℃, stirring and adding a water-soluble polymer surfactant, centrifuging the fifth product in a centrifuge, and freeze-drying the fifth product in freeze-drying equipment to obtain the nano montmorillonite, wherein the freeze-drying step comprises the following steps:
step 1: opening a raw material control valve (2) and a raw material pressure pump (3), spraying the nano montmorillonite to be freeze-dried, which is stored in a raw material tank (1) through a feeding pipe, onto the surface of a drying plate (10) through the feeding pipe, opening a liquid nitrogen storage tank (12) and a liquid nitrogen control valve (13) first, and freezing the raw material;
step 2: and opening a condenser (18) and a condenser control valve (19), opening a vacuum pump (6) and a vacuum pump control valve (14), sublimating and drying the water, pouring the nano montmorillonite which is subjected to freeze drying on the surface of the drying plate (10) into a storage box (9) by the drying plate (10) through a rotating rod (16), wherein the temperature is-15 ℃ to-45 ℃ in the freeze drying process, and the freezing pressure is 1.3Pa to 12.6 Pa.
2. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: when the terephthalic acid and the ethylene glycol are subjected to esterification reaction, the temperature of the reaction kettle is 192-; when the low-polymerization-degree polyethylene terephthalate is subjected to polycondensation reaction, the temperature of the reaction kettle is 245-278 ℃ and the pressure is 28-43 Pa.
3. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the dispersing agent is polyethylene glycol; the coupling agent is N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane.
4. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the extrusion temperature of the extruder is 274-286 ℃, and the rotating speed of the screw is 32-36 rpm; the longitudinal stretching temperature of the tenter is 84-88 ℃, the longitudinal stretching ratio is 2.85-3.1 times, the transverse stretching temperature is 104-118 ℃, the transverse stretching ratio is 2.6-3.4 times, and the heat setting temperature is 234-236 ℃.
5. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the rotation speed of the centrifugal machine is 10000rpm, and the centrifugation time is 20-30 min.
6. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the rotor speed of the stirrer was 800 rpm.
7. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the water-soluble polymer surfactant is polyvinylpyrrolidone; the intercalating agent is an aqueous solution of octadecyl amine hydrochloride.
8. The modified PET film for the flexible packaging film of the lithium battery as claimed in claim 1, wherein: the freeze drying equipment comprises an outer shell (4) and an inner shell (5), a gap between the outer shell (4) and the inner shell (5) is in a vacuum state, a raw material groove (1), a raw material control valve (2) and a raw material pressure pump (3) are installed on the top end of the outer shell (4), the raw material groove (1), the raw material control valve (2) and the raw material pressure pump (3) are connected with the outer shell (4) and the inner shell (5) through a feeding pipe, vacuum pumps (6) and vacuum pump control valves (14) which are symmetrical relative to the feeding pipe are installed on two sides of the upper portion of the outer shell (4), the vacuum pumps (6) and the vacuum pump control valves (14) are connected with the outer shell (4) through an exhaust pipe, one end of the exhaust pipe is connected with the vacuum pump control valve (14), the other end of the exhaust pipe is connected with the feeding pipe, the other end of the exhaust pipe is of a slope-shaped structure, the inner shell (5) is internally provided with a vacuum drying chamber (7), fixing frames (8) are arranged on two sides of the middle position of the vacuum drying chamber (7), a condensing disc (11) is fixed between the two fixing frames (8), the fixing frames (8) are movably connected with the condensing disc (11), a drying plate (10) is arranged on the upper surface of the condensing disc (11), and fixing plates (17) are welded on two sides of the drying plate (10);
a rotary rod (16) is fixedly welded at the central position of the fixing plate (17), the rotary rod (16) is movably connected with a supporting leg (15) welded on the surface of the inner wall of the inner shell (5), a liquid inlet (111) and a liquid outlet (112) are installed on the condensation disc (11), a condenser control valve (19) and a condenser (18) are connected through a condensation hose by the liquid inlet (111) and the liquid outlet (112), the condenser (18) is installed at one side of the outer shell (4), the condenser (18) is arranged below the fixing frame (8), a liquid nitrogen storage tank (12) and a liquid nitrogen control valve (13) are installed at the other side of the outer shell (4), the liquid nitrogen storage tank (12) and the liquid nitrogen control valve (13) are connected with the outer shell (4) through an air inlet pipe, the air inlet pipe is installed at a position between the drying plate (10) and a feeding pipe orifice, the fixing frame (8) is installed and fixed at the other side of the feeding pipe orifice, the bottom of the inner shell (5) is provided with a storage box (9).
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