CN109721751B

CN109721751B - Polyester film and preparation method thereof

Info

Publication number: CN109721751B
Application number: CN201811614010.9A
Authority: CN
Inventors: 张元华; 王山水; 王丽丽
Original assignee: Jiangsu Hengli Chemical Fiber Co Ltd
Current assignee: Jiangsu Hengli Chemical Fiber Co Ltd
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2021-02-05
Anticipated expiration: 2038-12-27
Also published as: CN109721751A

Abstract

The invention relates to a polyester film and a preparation method thereof, wherein the preparation method comprises the following steps: after the modified polyester melt is melted and extruded, cooling and solidifying, and then carrying out multi-stage longitudinal stretching, transverse stretching, heat setting and rolling to obtain a polyester film; the prepared polyester film is made of modified polyester, the molecular chain of the modified polyester comprises a terephthalic acid chain segment, a glycol chain segment, a 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol chain segment and a fluorine-containing diacid chain segment, and doped modified Bi is dispersed in the modified polyester₂O₃Powder; the doping modification process comprises the following steps: first, Ca is contained²⁺And a solution containing Bi³⁺The solution is uniformly mixed, then a precipitator is dripped until the pH value of the mixed solution is 9-10, and finally the precipitation product is calcined. The preparation method has simple process and low cost, and the degradation rate of the polyester is accelerated by modifying the polyester; the prepared product has good mechanical property and high degradation efficiency, and is beneficial to environmental protection.

Description

Polyester film and preparation method thereof

Technical Field

The invention belongs to the technical field of polyester fibers, and relates to a polyester film and a preparation method thereof.

Background

The polyester film (BOPET) is a biaxially oriented polyester film, which is prepared by taking polyethylene terephthalate slices as raw materials, preparing into a thick sheet through the working procedures of material mixing, drying and dewatering, extrusion melting, filter filtering, die head extrusion and the like, and then longitudinally stretching, transversely stretching, drawing and rolling. The polyester film has the characteristics of high tensile strength, good optical property, high elastic modulus, good toughness, good thermal stability and the like, and has the advantages of acid resistance, alkali resistance, good air tightness and the like. The polyester film is mainly applied to the packaging industry, such as food packaging, cigarette packets, wine packets, medicine packaging and the like, and is partially applied to the field of special films, such as liquid crystal displays (TFT-LCDs), automobile/building glass films, household appliance steel plate composite films, building decoration films and the like. The polyester film industry has huge development space in China, and the integral dosage of the polyester film is continuously increased along with the development of economy and society in China.

Because the crops covered by the mulching film have the functions of increasing temperature, preserving soil moisture, inhibiting weeds and the like, the application of the technology can realize the great increase in yield and income of the crops, and the mulching film can become important agricultural production data besides seeds, pesticides and chemical fertilizers. At present, the application of the mulching film technology greatly improves the yield of crops such as vegetables, corns, peanuts, cotton and the like in China, and makes a great contribution to ensuring the safe supply of agricultural products in China. At the same time, however, the widespread use of mulching also brings about a series of problems, such as technical general use and abuse, and "white pollution" caused by residual mulching film. Therefore, the reasonable utilization of the mulching film covering technology and the development of novel environment-friendly biodegradable mulching film products are new requirements of modern agriculture in China.

In practical application, the polyester is degraded by chemical degradation methods, which mainly include hydrolysis and alcoholysis, and ammonolysis, aminolysis and pyrolysis. However, the chemical degradation method used at present still has the problems of slow degradation rate, poor degradation effect and the like, and the method still cannot solve the problem of degradation and recycling of a large amount of mulching film residues.

In addition, with the diversification of the demand of people for polyester films, the production and use of colored polyester films have been increased year by year. However, because the raw material PET for preparing the polyester film belongs to hydrophobic fibers, the molecules of the PET do not contain hydrophilic groups, and the molecular structure of the PET lacks active groups which can be combined with dyes, such as cellulose or protein fibers, and the dyeing performance is poor. At present, when a color polyester film is prepared, disperse dyes are generally selected to dye at high temperature (130 ℃) and high pressure, the dye-uptake of fibers can be ensured only by dyeing at high temperature and high pressure, the requirements of high temperature and high pressure on equipment are high, the energy consumption is high, and meanwhile, the cost of the process is high due to the fact that the dyeing difficulty is high, the time required for dyeing is long.

Therefore, the research on the polyester film capable of being degraded and recycled with high efficiency and the preparation method thereof have very important significance.

Disclosure of Invention

The invention aims to overcome the defect of low natural degradation effect in the prior art and provides a polyester film capable of being degraded and recycled with high efficiency and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the preparation method of the polyester film comprises the steps of melting and extruding a modified polyester melt, cooling and solidifying, and then carrying out multistage longitudinal stretching, transverse stretching, heat setting and rolling to obtain the polyester film;

the preparation method of the modified polyester comprises the following steps: terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol, fluorine-containing dibasic acid and doping modified Bi₂O₃Uniformly mixing the powder, and then carrying out esterification reaction and polycondensation reaction in sequence;

the structural formula of 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is as follows:

according to the invention, 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is used for modifying the polyester, and the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol can significantly increase the space free volume of the polyester, particularly the existence of tert-butyl in the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol can cause the change of the activity of a main chain, so that the interaction force among chain units is changed, the distance among the chain units can be correspondingly changed, and the cavity free volume of the polyester is increased. Meanwhile, the free volume of the cavity is larger than that of the slit, so that the effective space size is larger, the penetration of small molecules such as water and oxygen is facilitated, the oxidative degradation of polyester is facilitated, sufficient nucleophilic ions are provided for nucleophilic reaction during polyester degradation, and the natural degradation speed of the modified fiber is promoted.

The fluorine-containing dibasic acid is 2, 2-difluoro-1, 3-malonic acid, 2-difluoro-1, 4-succinic acid, 2-difluoro-1, 5-glutaric acid or 2,2,3, 3-tetrafluoro-1, 4-succinic acid; the fluorine-containing dibasic acid is characterized in that fluorine atoms are on alpha carbon, when the fluorine-containing dibasic acid is introduced in the hydrolysis process, the electron-withdrawing capacity of the fluorine atoms on the alpha carbon is strong, so that the electron cloud density on a C-O bond in polyester is reduced, the stability of tetrahedral negative ions is reduced, the nucleophilic addition reaction is facilitated, and meanwhile, the steric hindrance of the fluorine-containing dibasic acid on the alpha carbon is smaller than that of terephthalic acid, so that the nucleophilic addition reaction is further promoted, and the degradation rate is remarkably improved.

Bi₂O₃The doping modification process comprises the following steps: first, Ca is contained²⁺And a solution containing Bi³⁺The solution is uniformly mixed, then a precipitator is dripped until the pH value of the mixed solution is 9-10, and finally the precipitation product is calcined. When the polyester contains the oxygen reduction catalyst, oxygen in the air can permeate into the polyester through the free volume in the polyester material, and oxygen reduction reaction is carried out on the surface of the oxygen reduction catalyst, so that ester bonds of the polyester are broken, and the degradation of the polyester is accelerated, but the further improvement of the degradation efficiency of the pure oxygen reduction catalyst is still limited. The modified polyester of the invention has Bi modified by doping dispersed therein₂O₃Powder, compared with the mixture prepared by only physically blending calcium oxide and bismuth trioxide, the calcium oxide is doped with Bi₂O₃Can destroy Bi₂O₃On the one hand, doped Bi₂O₃Increase the specific surface area of (2), and can improve Bi per unit mass₂O₃On the other hand, doped Bi₂O₃By monoclinic Bi₂O₃Bi is doped instead of end-type adsorption on surface₂O₃Lateral adsorption of the surface, and the adsorption is not influenced by the steric effect of Bi atoms on the surface, O₂The chemical adsorption of molecules at the Bi atom position is enhanced, the oxygen reduction catalysis efficiency of the catalyst is improved, and the modified Bi is dispersedly doped₂O₃The polyester film of the powder has high degradation efficiency during recovery treatment, and is beneficial to environmental protection.

As a preferred technical scheme:

in the above method for preparing a polyester film, the method for synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol comprises: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 10-15%, reacting for 3-4 hours at the temperature of 70-75 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1: 1.5-2.0: 0.015.

The method for producing a polyester film containing Ca as described above²⁺The concentration of the solution is 2-3 wt%, the solvent is water, and the anion in the solution is NO₃ ^-；

The Bi-containing component³⁺The solution of (a) is Bi with a concentration of 20 to 25 wt%₂O₃The solvent of (1) is nitric acid;

the precipitator is ammonia water with the concentration of 2 mol/L;

ca in the mixture at the beginning of precipitation²⁺And Bi³⁺The molar ratio of (A) to (B) is 5-8: 100; the invention is realized by adding Bi₂O₃Into which metal ion Ca is introduced²⁺(Bi₂O₃Is a main catalyst), the conduction rate of oxygen ions is increased, and the degree of oxygen reduction reaction is further increased, if the molar ratio is too large, Bi is influenced₂O₃Performance of (d); if the molar ratio is too small, the conduction rate of oxygen ions is not significantly increased.

Washing and drying the precipitate product before calcining, wherein the drying temperature is 105-110 ℃, and the drying time is 2-3 h;

the calcining process comprises the following steps: firstly, heating to 400 ℃, then preserving heat for 2-3 h, then heating to 700 ℃, preserving heat for 1-2 h, and finally cooling in the air; bi₂O₃After doping modification, crushing to obtain powder with the average grain diameter of less than 0.5 micron; the invention dissolves calcium into Bi in the calcining process₂O₃Inside the crystal lattice, the catalyst body forms more defects, so that the catalyst body is in a highly dispersed state on the surface of the solid solution, and Bi is further destroyed₂O₃The crystal plane structure of (1). The cooling speed is too slow, and the dispersion speed of mass points in the solid phase is slow, so that independent crystals are formed, and the damage to Bi is influenced₂O₃The crystal face structure of (1) is cooled in air, is not beneficial to forming crystals and is beneficial to damaging Bi₂O₃The crystal plane structure of (1).

The preparation method of the polyester film comprises the following steps:

(1) performing esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and fluorine-containing dibasic acid into slurry, and adding doped modified Bi₂O₃Uniformly mixing the powder, the catalyst, the flatting agent and the stabilizer, and pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is normal pressure to 0.3MPa, the temperature of the esterification reaction is 250-260 ℃, and the end point of the esterification reaction is when the distilled amount of water in the esterification reaction reaches more than 90% of the theoretical value;

(2) performing polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in a low vacuum stage under the condition of negative pressure, wherein the pressure in the stage is stably pumped from normal pressure to below 500Pa in 30-50 min, the reaction temperature is 250-260 ℃, the reaction time is 30-50 min, then continuously pumping vacuum to perform the polycondensation reaction in a high vacuum stage, so that the reaction pressure is further reduced to below 100Pa, the reaction temperature is 270-282 ℃, and the reaction time is 50-90 min.

The method for preparing the polyester film comprises the steps of enabling the molar ratio of the terephthalic acid, the ethylene glycol, the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol and the fluorine-containing dibasic acid to be 1: 1.2-2.0: 0.02-0.03: 0.03-0.05, and enabling the doped and modified Bi to be doped and modified₂O₃The addition amounts of the powder, the catalyst, the delustering agent and the stabilizer are respectively 0.15-0.20 wt%, 0.03-0.05 wt%, 0.20-0.25 wt% and 0.01-0.05 wt% of the addition amount of the terephthalic acid. 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, fluorine-containing dibasic acid and doping modified Bi₂O₃The addition amount of the powder can be adjusted according to actual application, but the adjustment range is not too large, the excessive addition amount can affect the performance (mechanical property) of the polyester film and influence the application of the polyester film, the too small addition amount has too small influence on the degradation performance of the polyester film, and the natural degradation rate of the polyester film is difficult to obviously improve.

According to the preparation method of the polyester film, the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, the flatting agent is titanium dioxide, and the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite.

The preparation method of the polyester film has the modified polyester with the number average molecular weight of 25000-30000 and the molecular weight distribution index of 1.8-2.2.

The preparation method of the polyester film comprises the steps of carrying out melt extrusion on the polyester film from a T-shaped head of a double-screw extruder, wherein the temperature of the melt extrusion is 275-285 ℃; the temperature for cooling and solidifying is 20-40 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 80-90 ℃, the stretching ratio is 1.0-1.3, the second longitudinal stretching temperature is 110-120 ℃, the stretching ratio is 2.0-2.5, the third longitudinal stretching temperature is 90-100 ℃, and the stretching ratio is 1.3-1.5; the transverse stretching temperature is 95-115 ℃, and the stretching ratio is 3.0-4.0; the heat setting temperature is 200-240 ℃.

The invention also provides a polyester film prepared by the preparation method of the polyester film, and the material is modified polyester;

the molecular chain of the modified polyester comprises a terephthalic acid chain segment, a glycol chain segment, a 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol chain segment and a fluorine-containing diacid chain segment; the modified polyester is dispersed with the doped and modified Bi₂O₃And (3) powder.

As a preferred technical scheme:

the thickness of the polyester film is 5-50 mu m, the longitudinal or transverse tensile strength is more than or equal to 150MPa, the longitudinal or transverse elongation at break is more than or equal to 70%, the longitudinal heat shrinkage rate is less than or equal to 1.5%, and the transverse heat shrinkage rate is less than or equal to 0.5%; the invention uses fluorine-containing binary acid and doped Bi₂O₃And 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol are used for modifying the polyester, and the mechanical property of the prepared polyester film is not reduced and is equivalent to that of the prior art.

After the polyester film is placed for 60 months under the conditions that the temperature is 25 ℃ and the relative humidity is 65%, the intrinsic viscosity of the polyester film is reduced by 26-30%; the intrinsic viscosity of the comparative sample was reduced by 3.7% under the same conditions, and the comparative sample and the polyester film of the present invention were formedThe difference is that the material is common polyester and Bi which is not added with doping modification is adopted₂O₃And (3) powder. The invention mechanism is as follows:

the invention modifies the polyester by 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, effectively improves the dyeing property of the polyester film, and simultaneously, the invention also modifies Bi by fluorine-containing dibasic acid and doping modification₂O₃The mutual cooperation of powder carries out further modification to polyester, on the basis that the dyeing effect promotes, has realized the accelerated degradation of polyester again, has effectively solved polyester film recycle's problem.

The action mechanism of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol for modifying the polyester and effectively improving the dyeing property of the polyester film is as follows:

the macromolecular chains in the polymer are not completely tightly packed, and voids always exist among the macromolecular chains, and the void volume is the free volume. Since small molecules are allowed to penetrate into the polymer, voids are sufficiently large in the polymer or between the polymers, the permeability and diffusivity of the small molecules are related to the size of the voids (i.e., the size of free volume) in the polymer structure, and within a certain range, the larger the size of the free volume, the higher the permeability of the small molecules, and the better the diffusivity. The free volume is divided into a cavity free volume and a slit free volume, the cavity free volume has larger space size than the slit free volume, and the effect of the cavity free volume is more obvious than the effect of the slit free volume for improving the permeability of small molecules.

The size and type of free volume depends primarily on the structure of the polymer, and the primary factors affecting the polymer structure are steric hindrance, pendant group size, pendant group structure, and the like. When a certain position on the main chain of the polymer is substituted by a side group, the activity of the main chain is inevitably changed, so that the interaction force between chains is changed, the distance between the chains is also correspondingly changed, and consequently, the cohesive energy and the free volume are changed, and the polarity, the size, the length and the like of the substituent on the side chain of the polymer have certain influences on the rigidity of the molecular chain, the interaction between molecules and the free volume fraction of the polymer structure, so that the effects generated by different substituents are different, and the osmotic separation performance of the polymer is often different.

For glycol straight chain molecules such as ethylene glycol and butanediol, the C atoms on the main chain are arranged in a zigzag manner from top to bottom, and when the H atom on a certain methylene on the main chain is replaced by a methyl group (-CH)₃) When in substitution, the C atoms on the side groups and the main chain C atoms are not in the same plane, so that four sp3 hybridized orbitals on the center C are respectively overlapped with empty orbitals on the four surrounding C atoms to form four completely same sigma bonds which are arranged in a regular tetrahedron, the four carbon atoms are respectively positioned at four vertexes of the regular tetrahedron, when three hydrogen of a methyl group is further substituted by the methyl group, the three hydrogen is equivalent to tert-butyl to form a larger tetrahedron structure, and compared with the molecular chain which is arranged in a zigzag manner, the molecular chain which is arranged in the regular tetrahedron manner has the advantages that the free volume of the empty hole is obviously increased, and the permeability and the diffusivity of small molecules can be obviously improved; when the H atom on a certain methylene on the main chain is replaced by the long branched chain substituent, the slit free volume is mainly increased, the increase amplitude is small, the improvement effect on the permeability and the diffusivity of the micromolecule is limited, and meanwhile, the long branched chain substituent has low rigidity, the molecular chains are easy to tangle, and the increase of the free volume is not facilitated.

The invention obviously improves the dyeing property of the polyester by introducing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol into the molecular chain of the polyester, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is as follows:

the existence of the tert-butyl group in the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol can cause the change of the activity of the main chain, thereby changing the interaction force among chain units, and the distance among the molecular chain units can be correspondingly changed, thereby causing the increase of the free volume of the modified polyester cavity. Compared with short-chain substituent groups (such as methyl, ethyl and the like), the tertiary butyl group occupies a larger spatial position, and a larger free volume is obtained in the molecular chain arrangement mode; compared with the long-branched-chain substituent, on one hand, the tertiary butyl group has the increased free volume of a cavity, the long-branched-chain substituent has the increased free volume of a slit, and on the other hand, the rigidity of the tertiary butyl group is higher than that of the long-branched-chain substituent, so that entanglement among molecular chains is reduced, and the tertiary butyl group has more free volume than the long-branched-chain substituent in the arrangement mode of the molecular chains. Meanwhile, the free volume of the cavity is larger than that of the slit, so that the effective space size is larger, the penetration of small molecules such as water and oxygen is facilitated, the oxidative degradation of polyester is facilitated, sufficient nucleophilic ions are provided for nucleophilic reaction during polyester degradation, and the natural degradation speed of the modified fiber is promoted.

In addition, the free volume of the cavity is larger than that of the slit, so that the free volume of the cavity is larger than that of the slit, dye molecules can be more favorably permeated into the fiber, the free volume of the cavity of the modified polyester is increased due to the introduction of 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, the difficulty of water or other molecules such as dye and the like permeating into polyester macromolecules is obviously reduced, the dyeing and the like of the polyester are positively influenced, the dyeing temperature can be reduced, the dyeing time can be shortened, the energy consumption can be reduced, and the dyeing rate of the polyester film can be improved.

Fluorine-containing dibasic acid and doped modified Bi₂O₃The mutual matching of the powder body further modifies the polyester, and the action mechanism of the accelerated degradation of the polyester is realized as follows:

the hydrolytic degradation process of polyester under alkaline condition is nucleophilic addition-elimination process, and OH is generated at the beginning of hydrolysis reaction^-Attack the C atom of ester carbonyl RCOOR ' to generate nucleophilic addition reaction to form intermediate (tetrahedral anion) which can eliminate OR ' to obtain carboxylic acid RCOOH and break ester bond, and OR ' and H⁺Binding to give alcohol HOR'. However, the degradation rate of polyester is slow because the anion structure of tetrahedron formed in the hydrolysis process is crowded, the steric hindrance is large, and the nucleophilic addition reaction is not facilitated. The invention obviously improves the degradation rate of polyester by introducing the fluorine-containing dibasic acid with a special structure into a polyester molecular chain, and the fluorine-containing dibasic acid is characterized in that fluorine atoms are on alpha carbon, and when the fluorine-containing dibasic acid is introduced in the hydrolysis processWhen the fluorine-containing dibasic acid is added, the electron absorption capacity is strong because fluorine atoms are on alpha carbon, so that the electron cloud density on a C-O bond in polyester is reduced, the stability of anions of a tetrahedron is reduced, and the nucleophilic addition reaction is facilitated. If fluorine-containing dibasic acid with fluorine atoms in beta carbon is introduced into a polyester molecular chain, the degradation rate of the polyester cannot be obviously improved, because when electron-withdrawing groups exist on the beta carbon, the generated influence is only limited on adjacent carbons, and the influence on C-O bonds in ester bonds is small, so that OH is influenced^-The reaction for attacking the ester carbonyl group to undergo nucleophilic addition has less influence.

In addition, because the polyester is exposed in the air for a long time, when the polyester contains a certain amount of oxygen reduction catalyst, oxygen in the air can permeate into the polyester through the free volume (narrow slit free volume and/OR hollow free volume) in the polyester material, the oxygen is adsorbed on the surface of the oxygen reduction catalyst, the oxygen gradually migrates to the surface of the oxygen reduction catalyst in the polyester, the adsorbed oxygen is formed after reaching a certain oxygen concentration gradient, oxygen reduction reaction (oxygen ionization) occurs on the surface of the oxygen reduction catalyst, in the reaction process, the oxygen is partially reduced into peroxide, oxygen molecules adsorbed by the oxygen reduction catalyst are bonded with ester in the polyester and are combined on the surface of the catalyst to form RCOOOR ', then a proton is combined and oxygen bonds are broken to form RCOOH, ester bonds are broken, and meanwhile OR' and H are broken⁺The alcohol HOR' is obtained by combination, thereby accelerating the degradation of the polyester.

According to the invention, the doping of calcium oxide and bismuth trioxide is realized by the method of solution blending, coprecipitation and calcination, so that the oxygen reduction catalytic process of bismuth trioxide is influenced, and the degradation rate of polyester is improved. To a certain extent, the closer the doped ion radius is to the doped ion radius, the more favorable the formation of oxygen vacancies and the more favorable the conduction of oxygen ions are, and the doping and Bi are selected in the invention³⁺Ca of the same ionic radius²⁺(Bi³⁺And Ca²⁺All with an ionic radius of 0.103nm) pairsIt is doped, which can increase the conduction rate of oxygen ions, which in turn increases the extent of the oxygen reduction reaction. The doping effect on the bismuth trioxide was as follows:

on the one hand, Bi can be destroyed by adopting the doping mode of the invention₂O₃The specific surface area is increased, and the unit mass Bi is further improved₂O₃The amount of oxygen adsorption of (a); on the other hand, Bi can be changed by adopting the doping mode of the invention₂O₃The adsorption mode and the oxygen reduction reaction mechanism are that before doping modification, the adsorption mode is monoclinic Bi₂O₃Terminal adsorption of surface, O atom in different monoclinic Bi₂O₃When the crystal face is adsorbed, the crystal face is influenced by the steric hindrance effect of Bi atoms on the surface, and O is₂Molecules are adsorbed at Bi atom positions through weak physical adsorption or weak chemical adsorption and are adsorbed at different monoclinic Bi₂O₃Crystal face O₂The molecules are reduced into peroxide, and after doping modification, the adsorption mode is that Bi is doped₂O₃Lateral adsorption of the surface, which is not affected by the "steric effect", enhances O₂The chemical adsorption of molecules at Bi atom position can also promote O₂Breaking of the O-O bond of the molecule, i.e. promoting O₂The molecules are reduced to generate peroxide, so that the oxygen reduction catalytic efficiency is improved, and the polyester degradation rate is further improved. If only calcium oxide and bismuth trioxide are physically blended, calcium oxide does not affect the crystal face structure of bismuth trioxide, and the adsorption mode and the oxygen reduction reaction mechanism of the calcium oxide are not changed, so that the oxygen reduction catalytic efficiency is not improved, and the polyester degradation rate is not improved.

Due to the existence of the oxygen reduction catalyst in the polyester, oxygen can stay in the polyester for a long time, the weakest ester group in the polyester can be oxidized, and the degradation degree of the polyester is accelerated. The prior art degradation polyester is started from the surface of the polyester, and the invention provides a new idea for degrading from the interior of the polyester by mixing the oxygen reduction catalyst into the polyester, and has high degradation efficiency.

Has the advantages that:

(1) the polyester film disclosed by the invention is excellent in dyeing property, good in mechanical property, easy to degrade, recycle and free from quality reduction, and has a good application prospect;

(2) according to the preparation method of the polyester film, the addition of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol enables the cavity free volume of the modified polyester to be larger, so that small dye molecules can easily enter the fiber to have positive influence on dyeing and the like of the polyester film, and meanwhile, the modified polyester film is also mixed with the fluorine-containing dibasic acid and the doped modified Bi₂O₃The powder performs synergistic action, can efficiently degrade the polyester film waste, and is beneficial to environmental protection.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

Example 1

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) was added at a concentration of 2.5 wt%₃)₂Aqueous solution with 22 wt% Bi₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 7: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 10 to obtain a precipitate, washing and drying the precipitate at 105 ℃ for 2.5 hours;

(1.3) heating the dried product to 400 ℃, then preserving heat for 2.5h, then heating to 700 ℃, preserving heat for 1.5h, and finally emptyingCooling in air and crushing to obtain doped modified Bi with the average grain diameter of 0.45 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 10%, reacting for 3 hours at the temperature of 72 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:2.0:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as the formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 3-malonic acid into slurry according to the molar ratio of 1:1.2:0.02:0.03, and adding doped modified Bi₂O₃Uniformly mixing the powder, antimony trioxide, titanium dioxide and triphenyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is normal pressure, the esterification reaction temperature is 250 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of a theoretical value, and modified Bi is doped₂O₃The adding amount of the powder, the antimony trioxide, the titanium dioxide and the triphenyl phosphate is respectively 0.15 wt%, 0.03 wt%, 0.20 wt% and 0.01 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in a low vacuum stage under the negative pressure condition, wherein the pressure in the stage is stably pumped from normal pressure to absolute pressure 499Pa within 30min, the reaction temperature is 250 ℃, the reaction time is 30min, then continuing to pump vacuum, and carrying out the polycondensation reaction in a high vacuum stage, so that the reaction pressure is further reduced to absolute pressure 99Pa, the reaction temperature is 270 ℃, the reaction time is 50min, and the modified polyester with the number average molecular weight of 25000 and the molecular weight distribution index of 1.8 is prepared;

(3) preparing a polyester film;

the modified polyester melt is melted and extruded from a T-shaped head of a double-screw extruder at the temperature of 285 ℃, cooled and solidified, and then subjected to multistage longitudinal stretching, transverse stretching, heat setting and rolling to prepare a polyester film; wherein the temperature for cooling and solidifying is 20 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 90 ℃, the stretching ratio is 1.3, the second longitudinal stretching temperature is 120 ℃, the stretching ratio is 2.5, the third longitudinal stretching temperature is 100 ℃, and the stretching ratio is 1.5; the temperature of transverse stretching is 115 ℃, and the stretching ratio is 4.0; the heat-setting temperature was 240 ℃.

The finally prepared polyester film has the thickness of 5 mu m, the longitudinal tensile strength of 165MPa, the elongation at break of 77 percent, the transverse tensile strength of 165MPa, the elongation at break of 76 percent, the longitudinal heat shrinkage of 1.2 percent and the transverse heat shrinkage of 0.4 percent;

the intrinsic viscosity of the polyester film decreased by 26% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%.

Comparative example 1

A process for producing a polyester film, which comprises substantially the same procedure as in example 1, except that 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, 2-difluoro-1, 3-propanedioic acid and doped modified Bi are not added in the step (2.2)₂O₃And (3) powder. The finally prepared polyester film has the thickness of 5 mu m, the longitudinal tensile strength of 165MPa, the elongation at break of 77 percent, the transverse tensile strength of 166MPa, the elongation at break of 75 percent, the longitudinal heat shrinkage of 1.3 percent and the transverse heat shrinkage of 0.4 percent; the intrinsic viscosity of the polyester film decreased by 3.7% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%. Comparing example 1 with comparative example 1, the invention greatly improves the degradability of the polyester fiber by modifying the polyester, and the mechanical property is not affected.

Comparative example 2

A process for producing a polyester film, substantially as described in example 1, except that 3, 3-difluoroglutaric acid is used in place of 2, 2-difluoro-1, 3-malonic acid in step (2.2). The intrinsic viscosity of the obtained polyester film was reduced by 14% after standing for 60 months at a temperature of 25 ℃ and a relative humidity of 65%. As can be seen by comparing example 1 with comparative example 1,because the fluorine atom has electron-withdrawing group on the beta carbon of the beta-carbon fluorine-containing dibasic acid, the generated influence is only limited on the adjacent carbon, and the influence on the C-O bond in the ester bond is small, thereby the fluorine atom has little influence on OH^-The influence of the reaction of attacking ester carbonyl group for nucleophilic addition is small, and the influence on the natural degradation process of the fiber is small, so that the fluorine-containing dibasic acid with fluorine atoms at alpha carbon is more favorable for improving the natural degradation performance of the fiber.

Comparative example 3

A process for producing a polyester film, which substantially corresponds to example 1, except that 1, 2-dodecyldiol is used in place of 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol in the step (2.2), and the intrinsic viscosity of the resulting polyester film decreases by 17% after the film is left to stand at a temperature of 25 ℃ and a relative humidity of 65% for 60 months. Comparing example 1 with comparative example 1, it can be seen that the increased void free volume of 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol of the present invention is greater than the increased slit free volume of 1, 2-dodecanediol, which is more favorable for providing sufficient nucleophilic ions and oxygen for the nucleophilic reaction of polyester degradation and redox reaction, and therefore, it can better react with Bi containing doping modification₂O₃The powder and the fluorine-containing binary acid chain segment have synergistic effect, so that the natural degradation speed of the polyester is improved.

Example 2

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) at a concentration of 2 wt%₃)₂Aqueous solution with 20 wt% Bi₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 5: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 9 to obtain a precipitate, washing and drying the precipitate at 105 ℃ for 2 h;

(1.3) heating the dried product to 400 ℃, then preserving the heat for 2h, then heating to 700 DEG CKeeping the temperature for 1h, finally cooling in air and crushing to obtain the doped modified Bi with the average grain diameter of 0.4 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 11%, reacting for 4 hours at the temperature of 70 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.8:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as the formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 4-succinic acid into slurry according to the molar ratio of 1:2.0:0.022:0.035, adding doped modified Bi₂O₃Uniformly mixing the powder, ethylene glycol antimony, titanium dioxide and trimethyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is 0.2MPa, the esterification reaction temperature is 260 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of a theoretical value, and modified Bi is doped₂O₃The adding amount of the powder, the ethylene glycol antimony, the titanium dioxide and the trimethyl phosphate is respectively 0.17 wt%, 0.04 wt%, 0.21 wt% and 0.02 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in a low vacuum stage under the negative pressure condition, wherein the pressure in the stage is stably pumped from normal pressure to the absolute pressure of 450Pa within 50min, the reaction temperature is 260 ℃, the reaction time is 50min, then continuing to pump vacuum, and carrying out the polycondensation reaction in a high vacuum stage, so that the reaction pressure is further reduced to the absolute pressure of 90Pa, the reaction temperature is 282 ℃, the reaction time is 90min, and the modified polyester with the number average molecular weight of 30000 and the molecular weight distribution index of 2.2 is prepared;

(2) preparing a polyester film;

The finally prepared polyester film has the thickness of 5 mu m, the longitudinal tensile strength of 164MPa, the elongation at break of 76 percent, the transverse tensile strength of 164MPa, the elongation at break of more than or equal to 77 percent, the longitudinal heat shrinkage rate of 1.2 percent and the transverse heat shrinkage rate of 0.42 percent;

the intrinsic viscosity of the polyester film decreased by 27% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%.

Example 3

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) was added at a concentration of 3 wt%₃)₂Aqueous solution with Bi of concentration 25 wt%₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 8: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 9 to obtain a precipitate, washing and drying the precipitate at the temperature of 110 ℃ for 3 hours;

(1.3) heating the dried product to 400 ℃, then preserving heat for 3h, then heating to 700 ℃, then preserving heat for 2h, finally cooling in air, and crushing to obtain the doped modified Bi with the average particle size of 0.4 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 12%, reacting for 4 hours at the temperature of 74 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.6:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as the formula (I);

(2.2) esterification reaction;

mixing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 5-glutaric acid into slurry according to the mol ratio of 1:1.5:0.024:0.034, adding doped modified Bi₂O₃Uniformly mixing the powder, antimony acetate, titanium dioxide and trimethyl phosphite, pressurizing in nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is 0.3MPa, the esterification reaction temperature is 255 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of the theoretical value, and modified Bi is doped₂O₃The adding amount of the powder, the antimony acetate, the titanium dioxide and the trimethyl phosphite is respectively 0.18 wt%, 0.05 wt%, 0.25 wt% and 0.05 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in the low vacuum stage under the negative pressure condition, stably pumping the pressure in the stage from normal pressure to absolute pressure of 480Pa within 40min, controlling the reaction temperature to be 255 ℃ and the reaction time to be 40min, then continuing to pump vacuum, and carrying out the polycondensation reaction in the high vacuum stage to further reduce the reaction pressure to absolute pressure of 95Pa, control the reaction temperature to be 272 ℃ and control the reaction time to be 70min, thus obtaining the modified polyester with the number average molecular weight of 27000 and the molecular weight distribution index of 2.0;

(3) preparing a polyester film;

the modified polyester melt is melted and extruded from a T-shaped head of a double-screw extruder at the temperature of 280 ℃, cooled and solidified, and then subjected to multistage longitudinal stretching, transverse stretching, heat setting and rolling to prepare a polyester film; wherein the temperature for cooling and solidifying is 25 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 85 ℃, the stretching ratio is 1.2, the second longitudinal stretching temperature is 115 ℃, the stretching ratio is 2.2, the third longitudinal stretching temperature is 95 ℃, and the stretching ratio is 1.4; the temperature of transverse stretching is 100 ℃, and the stretching ratio is 3.5; the heat-setting temperature was 220 ℃.

The finally prepared polyester film has the thickness of 30 mu m, the longitudinal tensile strength of 162MPa, the elongation at break of 75 percent, the transverse tensile strength of 160MPa, the elongation at break of 75 percent, the longitudinal heat shrinkage rate of 1.3 percent and the transverse heat shrinkage rate of 0.4 percent;

Example 4

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) was added at a concentration of 2.5 wt%₃)₂Aqueous solution with Bi of concentration 25 wt%₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 8: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 10 to obtain a precipitate, washing and drying the precipitate at the temperature of 110 ℃ for 3 hours;

(1.3) heating the dried product to 400 ℃, then preserving heat for 2.5h, then heating to 700 ℃, then preserving heat for 2h, finally cooling in air and crushing to obtain the doped modified Bi with the average grain diameter of 0.4 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 13%, reacting for 3.5 hours at the temperature of 74 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.5:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as the formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2,2,3, 3-tetrafluoro-1, 4-succinic acid into slurry according to the molar ratio of 1:1.6:0.025:0.038, and adding doped modified Bi₂O₃Uniformly mixing the powder, antimony acetate, titanium dioxide and triphenyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is 0.2MPa, the esterification reaction temperature is 260 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of a theoretical value, and modified Bi is doped₂O₃The adding amounts of the powder, the antimony acetate, the titanium dioxide and the triphenyl phosphate are respectively 0.18 wt%, 0.037 wt%, 0.22 wt% and 0.01 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in a low vacuum stage under the negative pressure condition, stably pumping the pressure in the low vacuum stage from normal pressure to absolute pressure of 480Pa within 35min, controlling the reaction temperature to 258 ℃, controlling the reaction time to be 45min, then continuing to pump vacuum, and carrying out the polycondensation reaction in a high vacuum stage, so that the reaction pressure is further reduced to absolute pressure of 96Pa, the reaction temperature is 270 ℃, the reaction time is 55min, and the modified polyester with the number average molecular weight of 26000 and the molecular weight distribution index of 1.9 is prepared;

(3) preparing a polyester film;

The finally prepared polyester film has the thickness of 30 mu m, the longitudinal tensile strength of 158MPa, the elongation at break of 76%, the transverse tensile strength of 160MPa, the elongation at break of 75%, the longitudinal heat shrinkage of 1.4% and the transverse heat shrinkage of 0.46%;

the intrinsic viscosity of the polyester film decreased by 28% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%.

Example 5

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) was added at a concentration of 2.5 wt%₃)₂Aqueous solution with Bi of concentration 24 wt%₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 6: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 10 to obtain a precipitate, washing and drying the precipitate at the temperature of 107 ℃ for 2.5 hours;

(1.3) heating the dried product to 400 ℃, then preserving heat for 2.5h, then heating to 700 ℃, then preserving heat for 2h, finally cooling in air and crushing to obtain the doping modified Bi with the average grain diameter of 0.45 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 14%, reacting for 3.5 hours at the temperature of 71 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.7:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as a formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2,2,3, 3-tetrafluoro-1, 4-succinic acid into slurry according to the molar ratio of 1:1.8:0.026:0.04, and adding doped modified Bi₂O₃Uniformly mixing the powder, antimony acetate, titanium dioxide and triphenyl phosphate, and pressurizing in a nitrogen atmosphere to perform esterification reactionThe pressurizing pressure is 0.2MPa, the temperature of the esterification reaction is 260 ℃, the end point of the esterification reaction is when the distilled amount of water in the esterification reaction reaches 95 percent of the theoretical value, and modified Bi is doped₂O₃The adding amounts of the powder, the antimony acetate, the titanium dioxide and the triphenyl phosphate are respectively 0.18 wt%, 0.03 wt%, 0.25 wt% and 0.01 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in the low vacuum stage under the negative pressure condition, smoothly pumping the pressure in the stage from normal pressure to absolute pressure of 480Pa within 50min, controlling the reaction temperature to be 255 ℃ and the reaction time to be 50min, then continuing pumping vacuum, and carrying out the polycondensation reaction in the high vacuum stage to further reduce the reaction pressure to absolute pressure of 95Pa, control the reaction temperature to be 282 ℃ and control the reaction time to be 80min, thus preparing the modified polyester with the number average molecular weight of 29000 and the molecular weight distribution index of 2.1;

(3) preparing a polyester film;

the modified polyester melt is melted and extruded from a T-shaped head of a double-screw extruder at 275 ℃, cooled and solidified, and then subjected to multistage longitudinal stretching, transverse stretching, heat setting and rolling to prepare a polyester film; wherein the temperature for cooling and solidifying is 40 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 80 ℃, the stretching ratio is 1.0, the second longitudinal stretching temperature is 110 ℃, the stretching ratio is 2.0, the third longitudinal stretching temperature is 90 ℃, and the stretching ratio is 1.3; the temperature of transverse stretching is 95 ℃, and the stretching ratio is 3.0; the heat-setting temperature was 200 ℃.

The finally prepared polyester film has the thickness of 50 mu m, the longitudinal tensile strength of 160MPa, the elongation at break of 75 percent, the transverse tensile strength of 160MPa, the elongation at break of 74 percent, the longitudinal heat shrinkage rate of 1.4 percent and the transverse heat shrinkage rate of 0.45 percent;

Example 6

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.1) Ca (NO) was added at a concentration of 3 wt%₃)₂Aqueous solution with Bi of concentration 24 wt%₂O₃The solution of (A) is mixed evenly, Bi₂O₃The solvent of the solution (2) is nitric acid, and Ca is contained in the mixed solution²⁺And Bi³⁺In a molar ratio of 7: 100;

(1.2) dropwise adding 2mol/L ammonia water until the pH value of the mixed solution is 10 to obtain a precipitate, washing and drying the precipitate at the temperature of 110 ℃ for 2.5 hours;

(1.3) heating the dried product to 400 ℃, then preserving heat for 3h, then heating to 700 ℃, then preserving heat for 1.5h, finally cooling in air and crushing to obtain the doping modified Bi with the average grain diameter of 0.45 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 15%, reacting for 3 hours at the temperature of 75 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.9:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as the formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 3-malonic acid into slurry according to the molar ratio of 1:1.7:0.028:0.042, and adding doped modified Bi₂O₃Uniformly mixing the powder, antimony acetate, titanium dioxide and trimethyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is normal pressure MPa, the esterification reaction temperature is 260 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of a theoretical value, and modified Bi is doped₂O₃The adding amount of the powder, the antimony acetate, the titanium dioxide and the trimethyl phosphate is respectively 0.18 wt%, 0.03 wt%, 0.25 wt% and 0.05 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in the low vacuum stage under the negative pressure condition, stably pumping the pressure in the stage from normal pressure to absolute pressure of 450Pa within 30min, controlling the reaction temperature to be 260 ℃ and the reaction time to be 30min, then continuing to pump vacuum, and carrying out the polycondensation reaction in the high vacuum stage to further reduce the reaction pressure to absolute pressure of 92Pa, controlling the reaction temperature to be 272 ℃ and the reaction time to be 85min, thus preparing the modified polyester with the number average molecular weight of 28000 and the molecular weight distribution index of 1.8;

(3) preparing a polyester film;

The finally prepared polyester film has the thickness of 50 mu m, the longitudinal tensile strength of 158MPa, the elongation at break of 74 percent, the transverse tensile strength of 158MPa, the elongation at break of 74 percent, the longitudinal heat shrinkage rate of 1.3 percent and the transverse heat shrinkage rate of 0.45 percent;

Example 7

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.3) heating the dried product to 400 ℃, then preserving heat for 3h, then heating to 700 ℃, then preserving heat for 2h, finally cooling in air, and crushing to obtain the doped modified Bi with the average grain diameter of 0.45 micron₂O₃Powder;

(2) preparing modified polyester;

(2.1) synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol by the following method: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 13.5%, reacting for 3.4 hours at the temperature of 73 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1:1.8:0.015, and the structural formula of the 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol is shown as a formula (I);

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 4-succinic acid into slurry according to the molar ratio of 1:1.8:0.027:0.045, and adding doped modified Bi₂O₃Uniformly mixing the powder, ethylene glycol antimony, titanium dioxide and trimethyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is 0.3MPa, the esterification reaction temperature is 260 ℃, the esterification reaction endpoint is when the water distillate in the esterification reaction reaches 95% of a theoretical value, and modified Bi is doped₂O₃The adding amount of the powder, the ethylene glycol antimony, the titanium dioxide and the trimethyl phosphate is respectively 0.18 wt%, 0.045 wt%, 0.22 wt% and 0.04 wt% of the adding amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in a low vacuum stage under the negative pressure condition, stably pumping the pressure in the stage from normal pressure to absolute pressure of 490Pa within 50min, controlling the reaction temperature to be 255 ℃ and the reaction time to be 50min, then continuing to pump vacuum, and carrying out the polycondensation reaction in a high vacuum stage to further reduce the reaction pressure to absolute pressure of 95Pa, control the reaction temperature to be 275 ℃ and control the reaction time to be 55min, thus preparing the modified polyester with the number average molecular weight of 25000 and the molecular weight distribution index of 2.2;

(3) preparing a polyester film;

the modified polyester melt is melted and extruded from a T-shaped head of a double-screw extruder at the temperature of 280 ℃, cooled and solidified, and then subjected to multistage longitudinal stretching, transverse stretching, heat setting and rolling to prepare a polyester film; wherein the temperature for cooling and solidifying is 30 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 84 ℃, the stretching ratio is 1.1, the second longitudinal stretching temperature is 115 ℃, the stretching ratio is 2.3, the third longitudinal stretching temperature is 95 ℃, and the stretching ratio is 1.4; the temperature of transverse stretching is 130 ℃, and the stretching ratio is 3.4; the heat-setting temperature was 230 ℃.

The finally prepared polyester film has the thickness of 35 mu m, the longitudinal tensile strength of 150MPa, the elongation at break of 73 percent, the transverse tensile strength of 155MPa, the elongation at break of 74 percent, the longitudinal heat shrinkage rate of 1.5 percent and the transverse heat shrinkage rate of 0.48 percent;

the intrinsic viscosity of the polyester film decreased by 29% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%.

Example 8

A preparation method of a polyester film comprises the following steps:

(1) preparation of doped modified Bi₂O₃Powder;

(1.3) heating the dried product to 400 ℃, then preserving heat for 3h, then heating to 700 ℃, then preserving heat for 2h, finally cooling in air and crushing to obtain the product with the average grain diameter of 0.45 muBi modified by doping rice₂O₃Powder;

(2) preparing modified polyester;

(2.2) esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and 2, 2-difluoro-1, 5-glutaric acid into slurry according to the molar ratio of 1:1.8.0:0.03:0.05, adding doped modified Bi₂O₃Uniformly mixing the powder, ethylene glycol antimony, titanium dioxide and triphenyl phosphate, pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is 0.3MPa, the temperature of the esterification reaction is 260 ℃, the end point of the esterification reaction is defined when the distilled amount of water in the esterification reaction reaches 95% of the theoretical value, and modified Bi is doped₂O₃The addition amounts of the powder, the ethylene glycol antimony, the titanium dioxide and the triphenyl phosphate are respectively 0.20 wt%, 0.03 wt%, 0.20 wt% and 0.01 wt% of the addition amount of the terephthalic acid;

(2.3) a polycondensation reaction;

after the esterification reaction is finished, starting the polycondensation reaction in the low vacuum stage under the negative pressure condition, stably pumping the pressure in the stage from normal pressure to absolute pressure of 480Pa within 50min, controlling the reaction temperature to be 260 ℃ and the reaction time to be 40min, then continuously pumping vacuum to perform the polycondensation reaction in the high vacuum stage, further reducing the reaction pressure to absolute pressure of 95Pa, controlling the reaction temperature to be 272 ℃ and the reaction time to be 90min, and preparing the modified polyester with the number average molecular weight of 29000 and the molecular weight distribution index of 2.1;

(3) preparing a polyester film;

The finally prepared polyester film has the thickness of 35 mu m, the longitudinal tensile strength of 152MPa, the elongation at break of 70 percent, the transverse tensile strength of 150MPa, the elongation at break of 70 percent, the longitudinal heat shrinkage rate of 1.5 percent and the transverse heat shrinkage rate of 0.5 percent;

the intrinsic viscosity of the polyester film decreased by 30% after 60 months at a temperature of 25 ℃ and a relative humidity of 65%.

Claims

1. The preparation method of the polyester film is characterized by comprising the following steps: after the modified polyester melt is melted and extruded, cooling and solidifying, and then carrying out multi-stage longitudinal stretching, transverse stretching, heat setting and rolling to obtain a polyester film;

the fluorine-containing dibasic acid is 2, 2-difluoro-1, 3-malonic acid, 2-difluoro-1, 4-succinic acid, 2-difluoro-1, 5-glutaric acid or 2,2,3, 3-tetrafluoro-1, 4-succinic acid;

Bi₂O₃the doping modification process comprises the following steps: first, Ca is contained²⁺And a solution containing Bi³⁺The solution is uniformly mixed, then a precipitator is dripped until the pH value of the mixed solution is 9-10, and finally the precipitation product is calcined.

2. The method for preparing polyester film according to claim 1, wherein the method for synthesizing 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol comprises: uniformly mixing palladium acetate and dimethyl di-tert-butyl ethylene, adding a hydrogen peroxide solution with the mass concentration of 10-15%, reacting for 3-4 hours at the temperature of 70-75 ℃, and cooling, crystallizing and refining to obtain 2,2,3,4,5, 5-hexamethyl-3, 4-hexanediol, wherein the mass ratio of the dimethyl di-tert-butyl ethylene to the hydrogen peroxide solution to the palladium acetate is 1: 1.5-2.0: 0.015.

3. The process for producing polyester film according to claim 2, wherein said Ca is contained²⁺The concentration of the solution is 2-3 wt%, the solvent is water, and the anion in the solution is NO₃ ^-；

the precipitator is ammonia water with the concentration of 2 mol/L;

ca in the mixture at the beginning of precipitation²⁺And Bi³⁺The molar ratio of (A) to (B) is 5-8: 100;

the calcining process comprises the following steps: firstly, heating to 400 ℃, then preserving heat for 2-3 h, then heating to 700 ℃, preserving heat for 1-2 h, and finally cooling in the air; bi₂O₃After doping modification, crushing to obtain powder with average grain size less than 0.5 micron.

4. The process for producing a polyester film according to claim 3, wherein the modified polyester is produced by the steps of:

(1) performing esterification reaction;

preparing terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and fluorine-containing dibasic acid into slurry, and adding doped modified Bi₂O₃Powder, a,Uniformly mixing a catalyst, a flatting agent and a stabilizer, and pressurizing in a nitrogen atmosphere to perform esterification reaction, wherein the pressurizing pressure is normal pressure to 0.3MPa, the esterification reaction temperature is 250-260 ℃, and the esterification reaction end point is determined when the distilled amount of water in the esterification reaction reaches more than 90% of a theoretical value;

(2) performing polycondensation reaction;

5. The method for producing a polyester film according to claim 4, wherein the molar ratio of the terephthalic acid, ethylene glycol, 2,3,4,5, 5-hexamethyl-3, 4-hexanediol and the fluorine-containing dibasic acid is 1:1.2 to 2.0:0.02 to 0.03:0.03 to 0.05, and the doped and modified Bi is₂O₃The addition amounts of the powder, the catalyst, the delustering agent and the stabilizer are respectively 0.15-0.20 wt%, 0.03-0.05 wt%, 0.20-0.25 wt% and 0.01-0.05 wt% of the addition amount of the terephthalic acid.

6. The method of claim 5, wherein the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, the matting agent is titanium dioxide, and the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite.

7. The method for producing a polyester film according to claim 6, wherein the modified polyester has a number average molecular weight of 25000 to 30000 and a molecular weight distribution index of 1.8 to 2.2.

8. The method for preparing the polyester film as claimed in claim 1, wherein the melt extrusion is extrusion from a T-shaped head of a twin-screw extruder, and the temperature of the melt extrusion is 275-285 ℃; the temperature for cooling and solidifying is 20-40 ℃; the parameters of the multistage longitudinal stretching are as follows: the first longitudinal stretching temperature is 80-90 ℃, the stretching ratio is 1.0-1.3, the second longitudinal stretching temperature is 110-120 ℃, the stretching ratio is 2.0-2.5, the third longitudinal stretching temperature is 90-100 ℃, and the stretching ratio is 1.3-1.5; the transverse stretching temperature is 95-115 ℃, and the stretching ratio is 3.0-4.0; the heat setting temperature is 200-240 ℃.

9. The polyester film produced by the process for producing a polyester film according to any one of claims 1 to 8, wherein: the material is modified polyester;

10. The polyester film according to claim 9, wherein the polyester film has a thickness of 5 to 50 μm, a longitudinal or transverse tensile strength of not less than 150MPa, a longitudinal or transverse elongation at break of not less than 70%, a longitudinal heat shrinkage of not more than 1.5%, and a transverse heat shrinkage of not more than 0.5%; after the polyester film is placed for 60 months under the conditions that the temperature is 25 ℃ and the relative humidity is 65%, the intrinsic viscosity of the polyester film is reduced by 26-30%.