High-temperature-resistant polyester film based on carbamido unit copolymerization modification and preparation method of high-temperature-resistant polyester film

Abstract

The invention discloses a high-temperature-resistant polyester film based on carbamido unit copolymerization modification and a preparation method thereof, and relates to a high-temperature-resistant polyester film and a preparation method thereof. The invention aims to solve the problem that ideal balance among cost, processability and heat resistance cannot be achieved in the prior art. The preparation method comprises the following steps: reacting a diamine monomer containing a primary amine group or a secondary amine group with excessive dihydric alcohol to synthesize a hydroxyl-terminated ureido dihydric alcohol prepolymer; then, the prepolymer is used as a comonomer, and is subjected to esterification / ester exchange and melt phase polycondensation with terephthalic acid and ethylene glycol to prepare copolyester containing a ureido structural unit in a molecular main chain. The carbamido units form a high-strength hydrogen bond network among molecular chains, so that the movement of molecular chain segments is substantially limited fundamentally, the glass-transition temperature of the obtained copolyester film is increased to 110-130 DEG C, the thermal deformation temperature exceeds 180 DEG C, and meanwhile, good mechanical properties and extremely low thermal shrinkage rate are kept. The invention belongs to the technical field of high polymer materials.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of high-temperature-resistant polyester film and its preparation method, belong to high polymer material technical field. BACKGROUND

[0002] Polyethylene terephthalate (PET) is widely used in packaging, fiber, film and other fields due to its excellent mechanical properties, transparency, cost-effectiveness and recyclability. However, its low glass transition temperature (Tg ~ 78℃) and heat distortion temperature (HDT ~ 70℃) severely limit its application in high temperature fields, such as flexible printed circuit board (FPC), high-temperature-resistant capacitor film, new energy battery insulation material, etc.

[0003] The existing technology to improve the heat resistance of PET mainly includes: 1. Copolymerization modification: such as introducing cyclohexane dimethanol (CHDM) to generate PETG, but the Tg is limitedly improved (usually < 90℃); or introducing naphthalene dicarboxylic acid (NDA) to generate PEN, which can increase Tg, but the cost is high and the raw material is limited. 2. Nanocomposite: adding nano inorganic fillers (such as montmorillonite, ) to improve the heat distortion temperature, but it often leads to a decrease in film transparency and an increase in brittleness, and has little effect on the improvement of Tg. 3. High crystallinity: high crystallinity PET is obtained by strengthening stretching and heat setting, but its heat shrinkage rate is difficult to control, and the essential improvement of Tg is limited.

[0004] However, the above methods all have obvious shortcomings and cannot achieve an ideal balance between cost, processability and heat resistance. Therefore, it is an urgent need in the industry to develop a new material that can substantially improve the heat resistance of PET from the essence of molecular structure and has good overall performance. SUMMARY

[0005] To solve the problem that the prior art cannot achieve an ideal balance between cost, processability and heat resistance, the present application proposes a high-temperature-resistant polyester film based on urea-based unit copolymerization modification and a preparation method thereof.

[0006] The technical solution adopted by the present application to solve the above problems is: the high-temperature-resistant polyester film based on urea-based unit copolymerization modification according to the present application is prepared from copolyester, and the molecular main chain of the copolyester is composed of terephthalic acid segment, ethylene glycol segment and urea-based copolymer unit segment; the urea-based copolymer unit is introduced by participating in copolycondensation reaction with hydroxyl-terminated urea-based dihydric alcohol prepolymer represented by general formula (I) or (II): HO-R1-O-C(O)-NH-R2-NH-C(O)-O-R1-OH… (I), HO-R1-O-C(O)-NH-R3-NH-C(O)-O-R1-OH… (II), wherein, R1 is C2-C6 alkylene; R2 is C6-C12 aromatic diamine residue; R3 is one of C2-C12 aliphatic diamine and alicyclic diamine residue.

[0007] Further, the mole fraction of the urea-based copolymer unit in the copolyester is 5% to 15%.

[0008] Further, R1 is one of , , .

[0009] Further, R2 is one of p-phenylene, 4,4'-methylene diphenylene, 2,6-naphthalene.

[0010] Further, R3 is one of isophorone diamine residue, 1,6-hexylene, 1,4-cyclohexylene.

[0011] Further, the intrinsic viscosity of the copolyester is 0.7~0.95dL / g.

[0012] Further, the glass transition temperature of the high-temperature-resistant polyester film is 110℃ to 130℃, and the heat distortion temperature is not less than 180℃.

[0013] The preparation method of the high-temperature-resistant polyester film based on urea unit copolymerization modification according to the present application comprises the following specific steps: Step 1, prepolymer synthesis; make excess dihydric alcohol HO-R1-OH and diamine or react at 100~150℃ to generate a terminal hydroxyl urea dihydric alcohol prepolymer; Step 2, copolycondensation reaction: mix terephthalic acid or its derivative, ethylene glycol and the prepolymer obtained in step 1, and sequentially perform esterification / ester exchange reaction and melt polycondensation reaction under the action of a catalyst to obtain the copolyester; Step 3, film forming: melt extrude, cast, biaxially stretch and heat set the copolyester obtained in step 2 to prepare the high-temperature-resistant copolyester film.

[0014] Further, the molar feeding ratio of dihydric alcohol to diamine in step 1 is (2.1~2.5):1.

[0015] Further, the stretching temperature of biaxial stretching in step 3 is 90~110℃, and the longitudinal and lateral stretching ratios are both 3.0~4.0; the heat setting temperature is 200~240℃, and the time is 5~30 seconds.

[0016] The present application has the following beneficial effects: 1. The high-temperature-resistant quality of the present application: through the high-strength and high-density hydrogen bond network formed by the strong polar urea unit (-NH-C(O)-NH-) between the molecular chains, the physical crosslinking network greatly limits the movement of the molecular chain segments, thereby greatly increasing the glass transition temperature (Tg) of the material from 78℃ of ordinary PET to 110-130℃, and increasing the heat distortion temperature (HDT) to above 180℃; 2. The present application has excellent comprehensive performance: the hydrogen bond network not only gives high heat resistance, but also plays the role of physical crosslinking point, can effectively transfer and disperse stress, so that the film has high heat resistance, excellent mechanical strength, modulus and dimensional stability; 3. The present application has good processability: by designing the route of "hydroxyl-terminated urea pre-polymer", it is ensured that the copolymerization unit can smoothly participate in the melt polycondensation reaction of PET, avoiding the side reactions and gelation problems caused by the direct participation of diamine in polycondensation, and ensuring the feasibility and stability of the polymerization process; 4. The structure of the present application has strong designability: by selecting different diamine monomers (R2 or R3), the strength and density of hydrogen bond and the rigidity of copolyester can be flexibly adjusted to realize the fine customization of material performance. DETAILED DESCRIPTION

[0017] Specific embodiment one: a high-temperature-resistant polyester film based on urea unit copolymerization modification, the high-temperature-resistant polyester film is made of copolyester, the polyester molecular main chain is a random or block copolymer composed of terephthalic acid chain segment, ethylene glycol chain segment and urea copolymer unit chain segment; the urea copolymer unit is introduced by participating in the copolycondensation reaction of the hydroxyl-terminated urea dihydric alcohol pre-polymer generated by the reaction of diamine monomer containing primary amine group or secondary amine group and excess dihydric alcohol; The hydroxyl-terminated urea dihydric alcohol pre-polymer has the following general structure: HO-R1-O-C(O)-NH-R2-NH-C(O)-O-R1-OH Or HO-R1-O-C(O)-NH-R3-NH-C(O)-O-R1-OH Wherein, R1 is C2-C6 alkylene; R2 is C6-C12 aromatic diamine residue; R3 is C2-C12 aliphatic diamine or alicyclic diamine residue; In some embodiments, the mole fraction of the urea copolymer unit in the final copolyester is 5% ~ 15%; the mole fraction of the urea copolymer unit in the final copolyester is less than 5%, the heat resistance improvement effect is not significant; the mole fraction of the urea copolymer unit in the final copolyester is higher than 15%, which may cause processing difficulty and cost increase.

[0018] Specific embodiment two: a preparation method of high-temperature-resistant polyester film based on urea-based unit copolymerization modification, the specific steps include: Step 1, prepolymer synthesis: an excess of dihydric alcohol (HO-R1-OH, such as ethylene glycol, 1,4-butanediol) is reacted with a dihydric amine (such as p-phenylenediamine, isophorone diamine) at 100-150°C to generate a hydroxyl-terminated urea-based dihydric alcohol prepolymer; the molar ratio (dihydric alcohol: dihydric amine > 2:1) needs to be strictly controlled in this step to ensure that the end group is a hydroxyl group; or such as p-phenylenediamine, isophorone diamine) at 100-150°C to generate a hydroxyl-terminated urea-based dihydric alcohol prepolymer; the molar ratio (dihydric alcohol: dihydric amine > 2:1) needs to be strictly controlled in this step to ensure that the end group is a hydroxyl group; Step 2, esterification / ester exchange: terephthalic acid (PTA) or its dimethyl terephthalate (DMT) is mixed with ethylene glycol (EG) in a conventional ratio, and the hydroxyl-terminated urea-based dihydric alcohol prepolymer synthesized in step 1 is added, and esterification or ester exchange is carried out under the action of a catalyst; Step 3, polycondensation: the product after esterification / ester exchange is subjected to melt polycondensation at high temperature and high vacuum to obtain a copolyester with an intrinsic viscosity in the range of 0.70 ~ 0.95 dL / g; Step 4, casting and biaxial stretching: the copolyester melt is extruded into a cast sheet through a die, and then synchronous or stepwise biaxial stretching is carried out at a temperature of 10-30°C above Tg, with a stretching ratio of 3.0*3.0 ~ 4.0*4.0; Step 5, heat setting: the stretched film is heat set at 200 ~ 240°C for 5~ 30 seconds to obtain a stable crystal structure and extremely low thermal shrinkage.

[0019] Example Example 1 Step 1, prepolymer synthesis: under nitrogen protection, an excess of ethylene glycol (EG) and a metered amount of p-phenylenediamine (PPD) are added to a reaction kettle, and reacted at 120°C for 4 hours to generate a hydroxyl-terminated bis(2-hydroxyethyl) p-phenylenediamine prepolymer; Step 2, copolycondensation: PTA, EG and the above prepolymer (molar ratio PTA: (EG + prepolymer) = 1:1.5, and the prepolymer accounts for 8 mol% of the total dihydric alcohol component) are added to an esterification kettle, and antimony acetate is added as a catalyst to carry out a conventional esterification reaction. Subsequently, the material is transferred to a polycondensation kettle, and polycondensation is carried out at 285°C and a vacuum degree <100 Pa to obtain a copolyester with an intrinsic viscosity of 0.82 dL / g; Step 3, film formation: after drying the copolyester chips, melt extrusion, casting, then biaxial stretching of 3.5 times longitudinally and 3.5 times transversely at 95°C, and finally heat setting at 220°C for 10 seconds, a film with a thickness of 50μm is prepared.

[0020] Comparative example The common bottle-grade PET chip is used to prepare a common BOPET film with a thickness of 50 μm under the same process conditions.

[0021] Performance test The films obtained in Example 1 and the comparative example are subjected to performance test, and the results are shown in the following table.

[0022] The test results show that the heat resistance of the copolyester film prepared in the application has been greatly improved, and the mechanical properties are excellent, which fully meets the application requirements in the fields of high-end electronic insulation, high-temperature adhesive tape base materials and the like.

[0023] The above is only a preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above with a preferred embodiment, it is not intended to limit the application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the application, and the equivalent embodiments with equivalent changes are equivalent. Any simple modification, equivalent replacement and improvement of the above embodiments, as long as it does not depart from the technical solution of the application, is within the protection scope of the technical solution of the application.

Claims

1. A high-temperature resistant polyester film based on copolymerization modification of urea-based units, characterized by, The high-temperature-resistant polyester film is prepared from a copolyester, and a main chain of the copolyester is composed of terephthalic acid segments, ethylene glycol segments and urea-based copolymer unit segments; the urea-based copolymer unit is introduced by participating in a copolycondensation reaction of a hydroxyl-terminated urea-based dihydric alcohol prepolymer represented by general formula (I) or (II): HO-R1-O-C(O)-NH-R2-NH-C(O)-O-R1-OH… (I), HO-R1-O-C(O)-NH-R3-NH-C(O)-O-R1-OH… (II), wherein R1 is C2-C6 alkylene; R2 is C6-C12 aromatic diamine residue; and R3 is one of C2-C12 aliphatic diamine and alicyclic diamine residue.

2. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, The mole fraction of the urea-based copolymer unit in the copolyester is 5% to 15%.

3. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, R1 is one of , , .

4. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, R2 is one of p-phenylene, 4,4'-methylene diphenylene and 2,6-naphthalene.

5. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, R3 is one of isophorone diamine residue, 1,6-hexylene and 1,4-cyclohexylene.

6. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, The intrinsic viscosity of the copolyester is 0.7-0.95 dL / g.

7. The urea-based unit copolymer-modified high-temperature-resistant polyester film according to claim 1, characterized in that, The glass transition temperature of the high-temperature-resistant polyester film is 110-130℃, and the heat distortion temperature is not less than 180℃.

8. A method of producing the high-temperature-resistant polyester film according to claim 1, characterized by, The specific steps include: Step 1, prepolymer synthesis; excess diol HO-R1-OH is reacted with di-amine H2N-R2-NH2 or at 100-150°C to form a terminal hydroxyl urea diol prepolymer; Step 2, copolycondensation reaction: terephthalic acid or its derivative and ethylene glycol are mixed with the prepolymer obtained in step 1, and esterification / ester exchange reaction and melt polycondensation reaction are sequentially carried out under the action of a catalyst to obtain the copolyester; Step 3, film forming: the copolyester obtained in step 2 is melt-extruded, cast, bidirectionally stretched and heat set to prepare the high-temperature-resistant copolyester film.

9. The method for preparing the high-temperature-resistant polyester film based on urea-based unit copolymerization modification according to claim 8, characterized in that, The molar feeding ratio of dihydric alcohol to diamine in step 1 is (2.1-2.5):

1.

10. The method for preparing a high-temperature-resistant polyester film based on urea group unit copolymerization modification according to claim 8, characterized in that, In step 3, the stretching temperature of bidirectional stretching is 90-110℃, and the longitudinal and lateral stretching ratios are both 3.0-4.0; the heat setting temperature is 200-240℃, and the time is 5-30 seconds.

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