Durable waterproof breathable polyester film and preparation method thereof

Abstract

The invention provides a durable waterproof breathable polyester film and a preparation method thereof, a first monomer and a second monomer are mixed for an esterification reaction, a third monomer is added for a condensation polymerization reaction, a copolymer is obtained after the condensation polymerization is finished, the copolymer is sliced, the first monomer is terephthalic acid, the second monomer is ethylene glycol, and the third monomer is an organosilicon reagent; and dissolving the copolymer slices by using a mixed solvent of trifluoroacetic acid and dichloromethane to obtain a spinning solution, and carrying out electrostatic spinning on the spinning solution to obtain the polyester fiber membrane. According to the invention, dibasic acid, dihydric alcohol and hydroxyl silicone oil monomers containing different side group substituents are copolymerized to prepare the copolyester with durable hydrophobicity, and the hydrophobicity of the copolyester is accurately controlled by adjusting the lengths of side group functional groups and chain segments; the preparation of the intrinsically-modified waterproof breathable polyester film with durability is realized by regulating and controlling key parameters such as pore structure, porosity and specific surface area of nanofibers in combination with an electrostatic spinning technology.

Description

Technical Field

[0001] The invention relates to the technical field of polyester films, and in particular to a durable waterproof and breathable polyester film and a preparation method thereof. Background Art

[0002] Waterproof and breathable functional membrane products are mostly made of fluorine-containing polymers. Although these materials provide excellent waterproofness and breathability, long-term contact with these fluorine-containing materials will pose a threat to consumers' health. In addition, excessive fluorine is released into the environment during the degradation of the materials, which may lead to excessive fluorine intake in the human body, which also has a serious impact on the environment. In view of the above problems, it is of great significance to develop fluorine-free and environmentally friendly membrane materials.

[0003] Xue et al. (Surf.Coat.Tech.2017,310,134) coated PDMS (polydimethylsiloxane) / SiO2 mixture on PET (polyethylene terephthalate) fabric and then in situ Reaction, further hydrophobic treatment of the coated textiles with tetraethoxysilane and hexadecyltrimethoxysilane can successfully prepare superhydrophobic textiles with high water pressure resistance. You et al. (Compos. Commun. 2023, 40, 101621) used a blending method to configure electrospinning solutions of PET and PDMS in different proportions, and prepared a waterproof and breathable polyester film by electrospinning combined with heat treatment technology. Although these studies have achieved remarkable results in the preparation of superhydrophobic surfaces, the application of coating and blending technology still faces some challenges, including insufficient durability, poor compatibility, and easy occurrence of component analysis, which limit their practical application.

[0004] In view of this, it is necessary to design an improved durable waterproof breathable polyester film and a preparation method thereof to solve the above problems. Summary of the invention

[0005] In view of the defects of the above-mentioned prior art, the object of the present invention is to provide a durable waterproof and breathable polyester film and a preparation method thereof, wherein a hydrophobic copolyester is prepared by copolymerizing a dibasic acid, a diol and a hydroxy silicone oil monomer containing different side substituents, and the hydrophobic properties of the copolyester are precisely controlled by adjusting the side functional groups and the length of the chain segments.

[0006] To achieve the above object, the present invention provides a method for preparing a durable waterproof and breathable polyester film, comprising the following steps:

[0007] S1. Add the first monomer and the second monomer into the reactor for esterification reaction, add the third monomer after the esterification is completed, react for 0.5 to 1 hour under normal pressure, and then carry out polycondensation reaction, slice the obtained copolymer to obtain modified polyester slices; the first monomer is PTA (terephthalic acid), the second monomer is EG (ethylene glycol), and the third monomer is an organosilicon reagent;

[0008] S2. The polyester chips obtained in step S1 are dissolved in a TFA / DCM (trifluoroacetic acid / dichloromethane) mixed solvent, stirred at room temperature for a predetermined time to prepare an electrospinning solution, and the electrospinning solution is electrospun to obtain a durable waterproof and breathable polyester film.

[0009] As a further improvement of the present invention, in step S1, the general structural formula of the third monomer is In the formula, R is C0~C 20 R1 and R2 are independently methyl, phenyl or C3~C 10 Long chain alkyl; X is O or NH; m is a positive integer. The amount of the third monomer added is 2.5-10% of the mass of the first monomer.

[0010] The molar ratio of the first monomer to the second monomer is 1:(1-1.5).

[0011] As a further improvement of the present invention, in step S1, a catalyst is further added to the esterification reaction, and the catalyst is Sb2O3, and the addition amount is 400-600 ppm. The reaction temperature of the esterification reaction is 240-260° C. When the water output of the esterification reaction reaches 90% of the theoretical water output, the esterification reaction is stopped.

[0012] As a further improvement of the present invention, in step S1, the specific reaction conditions of the polycondensation reaction are: slowly evacuating to 80-100 Pa within 1-3 hours, heating the system to 270-280° C., and reacting for 1-2 hours.

[0013] As a further improvement of the present invention, in step S2, the mass ratio of TFA to DCM in the TFA / DCM mixed solvent is (4-8):1; and the stirring time is 10-14 hours.

[0014] The present invention also provides a durable waterproof breathable polyester film, which is prepared by the above-mentioned method for preparing the durable waterproof breathable polyester film. The thickness of the durable waterproof breathable polyester film is 65-75 μm.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention provides a durable waterproof and breathable polyester film and a preparation method thereof. A hydrophobic copolyester is prepared by copolymerizing a dibasic acid, a diol and a hydroxy silicone oil monomer containing different side group substituents. The hydrophobic properties of the copolyester are precisely controlled by adjusting the side group functional group and the length of the chain segment. In addition, by combining the electrospinning technology, key parameters such as the pore structure, porosity and specific surface area of ​​the nanofibers are regulated, thereby realizing the preparation of a waterproof and breathable polyester film with intrinsic modification. This method not only improves the durability and stability of the material, but also facilitates large-scale production, providing a feasible solution for practical applications.

[0017] 2. The present invention obtains permanent hydrophobic polyester by chemical copolymerization intrinsic modification, and then obtains waterproof and breathable fiber membrane by electrostatic spinning, so as to achieve fluorine-free, environmentally friendly, low-cost, and better stability and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The synthetic route of the modified polyester of the present invention is shown in FIG.

[0019] Figure 2 This is the SEM image of the PET-PDMSx fiber membrane prepared in the present invention.

[0020] Figure 3 This is the contact angle diagram of the PET-PDMSx copolymer slice and fiber membrane prepared in the present invention.

[0021] Figure 4 The maximum pore size and porosity of the PET-PDMSx fiber membrane prepared in the present invention.

[0022] Figure 5 This is the contact angle diagram of the fiber membrane blended with different PDMS addition amounts in comparative examples 2-4. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0025] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0026] The present invention provides a method for preparing a durable waterproof and breathable polyester film, comprising the following steps:

[0027] S1. Add the first monomer and the second monomer into a reactor for esterification reaction, add the third monomer after the esterification is completed, react for 0.5 to 1 hour under normal pressure, and then carry out polycondensation reaction, slice the obtained copolymer to obtain modified polyester slices; the first monomer is PTA, the second monomer is EG, and the third monomer is an organosilicon reagent.

[0028] Specifically, the esterification process is adopted, with PTA and EG as the first monomer and the second monomer, and they are put into the reactor according to the molar ratio of 1: (1-1.5), and 400-600ppm Sb2O3 is added as a catalyst for esterification reaction. The reaction temperature is 240-260℃. When the water output of the esterification reaction reaches 90% of the theoretical water output, the esterification reaction is stopped, and the third monomer silicone reagent is added. After reacting for 0.5-1h under normal pressure, the polycondensation stage is entered. First, a pre-polycondensation treatment is carried out, and the vacuum is slowly evacuated to 80-100pa within 1-3h. Subsequently, the system is heated to 270-280℃, and the reaction is continued for 1-2h. The material is discharged from the bottom of the reactor and sliced.

[0029] The general structural formula of the third monomer is In the formula, R is C0~C 20 R1 and R2 are independently methyl, phenyl or C3~C 10 long chain alkyl; X is O or NH; m is a positive integer. The amount of the third monomer added is 2.5-10% of the mass of the first monomer. In some embodiments of the present invention, the third monomer is PDMS (polydimethylsiloxane), and the obtained copolymer is PET-PDMSx, where x represents the mass ratio of PDMS to PTA, that is, PDMS / PTA=x / 100.

[0030] The synthetic route of modified polyester is as follows Figure 1 As shown, n and p are positive integers, which can be calculated based on the molecular weight of the copolyester and the integration of its nuclear magnetic resonance peak.

[0031] S2. dissolving the polyester chips obtained in step S1 in a TFA / DCM mixed solvent, stirring at room temperature for a predetermined time to prepare an electrospinning solution, and electrospinning the electrospinning solution to obtain a durable waterproof and breathable polyester film.

[0032] Specifically, the modified polyester chips were dissolved in a TFA / DCM mixed solvent and stirred at room temperature for 10 to 14 h to prepare an electrospinning solution. The mass ratio of TFA to DCM in the TFA / DCM mixed solvent was (4 to 8):1. Polyester fiber membranes containing different silicone contents were prepared using electrospinning technology. During this process, the spinning voltage was set to 22 kV, while the solution injection speed was kept constant at 0.08 mm / min. The deposition of the fibers was carried out continuously on a metal roller, the roller rotating speed was 140 rpm, and the distance between the spinneret and the roller was maintained at 20 cm. In order to control the environmental conditions, the relative humidity and temperature were maintained at approximately 23 ± 3 ° C and 10% RH, respectively. The thickness of the prepared fiber membrane was controlled within a precise range of 65 to 75 μm. Before further processing, these fiber membranes were first naturally flattened at room temperature and their edges were fixed using polyimide heat-resistant tape to ensure the stability of the membrane. Subsequently, the fiber membranes were placed in an oven and heated at 120 ° C for 1 h to remove any residual solvent.

[0033] Different electrospinning parameters, such as solution concentration, spinning speed, spinning voltage, etc., will lead to changes in the spun fibers, directly affecting the changes in the pore structure and porosity of the fiber membrane. The solution concentration affects the droplet formation and solidification speed during the spinning process, thereby affecting the diameter, surface morphology and structure of the nanofiber membrane. The spinning speed affects the dispersion and molding of the fibers, thereby affecting the diameter and structure of the fibers. The spinning voltage is an important parameter for controlling the charge distribution during the fiber formation process. As the spinning voltage increases, the accumulation of charge and the strength of the electrostatic field will also increase, resulting in changes in the diameter, porosity and pore size of the fiber membrane.

[0034] The preparation method of the durable waterproof and breathable polyester film provided by the present invention is described below with reference to specific embodiments.

[0035] Example 1

[0036] Embodiment 1 provides a method for preparing a durable waterproof and breathable polyester film, comprising the following steps:

[0037] S1. PTA and EG are put into the reactor in a molar ratio of 1:1.3 for esterification reaction, 500ppm Sb2O3 is added as a catalyst, the esterification reaction temperature is 250℃, when the water output of the esterification reaction reaches 90% of the theoretical water output, the esterification reaction is stopped, and the third monomer silicone reagent is added. After reacting for 0.5h under normal pressure, it enters the polycondensation stage. First, a pre-polycondensation treatment is carried out, and the vacuum is slowly evacuated to 100pa within 1.5h. Then, the system is heated to 280℃ and the reaction is continued for 1.5h. After the polycondensation is completed, the material is sliced, wherein the third monomer is PDMS, and the amount used is 2.5% of the mass of terephthalic acid.

[0038] S2. The modified polyester chips were dissolved in a TFA / DCM (6 / 1, w / w) mixed solvent and stirred at room temperature for 12 h to prepare an electrospinning solution. Next, the polyester fiber membrane was prepared using electrospinning technology. During this process, the spinning voltage was set to 22 kV, while the solution injection speed was kept constant at 0.08 mm / min. The deposition of the fibers was carried out continuously on a metal roller, the roller rotating at a speed of 140 rpm, and the distance between the spinneret and the roller was maintained at 20 cm. In order to control the environmental conditions, the relative humidity and temperature were maintained at approximately 23 ± 3 ° C and 10% RH, respectively. Before further processing, these fiber membranes were first naturally flattened at room temperature and their edges were fixed using polyimide heat-resistant tape to ensure the stability of the membrane. Subsequently, the fiber membrane was placed in an oven and heated at 120 ° C for 1 h to remove any residual solvent.

[0039] Example 2-3

[0040] Examples 2-3 respectively provide a method for preparing a durable waterproof and breathable polyester film. Compared with Example 1, the only difference is that the amount of the third monomer added is different, which is 5% and 10% of the mass of terephthalic acid, respectively. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0041] Example 4

[0042] Example 4 provides a method for preparing a durable waterproof and breathable polyester film. Compared with Example 1, the only difference is that the third monomer is amino silicone oil (i.e., X in the third monomer structural formula is NH), and other experimental parameters and conditions are basically the same as those in Example 1, which will not be repeated here.

[0043] Embodiment 5-6

[0044] Examples 5-6 respectively provide a method for preparing a durable waterproof and breathable polyester film. Compared with Example 4, the only difference is that the amount of the third monomer added is different, which is 5% and 10% of the mass of terephthalic acid, respectively. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0045] Example 7

[0046] Example 7 provides a method for preparing a durable waterproof and breathable polyester film. Compared with Example 1, the only difference is that the third monomer is hydroxyalkyl silicone oil (that is, R in the third monomer structure is a C3 long-chain alkyl group), and the other experimental parameters and conditions are basically the same as those in Example 1, which will not be repeated here.

[0047] Embodiment 8-9

[0048] Examples 8-9 respectively provide a method for preparing a durable waterproof and breathable polyester film. Compared with Example 7, the only difference is that the amount of the third monomer added is different, which is 5% and 10% of the mass of terephthalic acid, respectively. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0049] Comparative Example 1

[0050] Comparative Example 1 provides a method for preparing a durable waterproof and breathable polyester film. Compared with Example 1, the only difference is that the third monomer is not added, and other experimental parameters and conditions are basically the same as those in Example 1, which will not be repeated here.

[0051] Table 1 Contact angle data of fiber membranes spun by different organosilicon reagents

[0052] project The third monomer Addition amount Contact angle Example 1 PDMS 2.5％ 132.8° Example 2 PDMS 5％ 138.0° Example 3 PDMS 10％ 135.7° Example 4 Amino silicone oil 2.5％ 133.0° Example 5 Amino silicone oil 5％ 136.6° Example 6 Amino silicone oil 10％ 135.1° Example 7 Hydroxyalkyl silicone oil 2.5％ 130.8° Example 8 Hydroxyalkyl silicone oil 5％ 134.7° Example 9 Hydroxyalkyl silicone oil 10％ 134.0° Comparative Example 1 — — 130.4°

[0053] —Indicates not added.

[0054] As shown in Table 1, the hydrophobicity of the fiber membranes prepared in Examples 1-9 was improved compared with that of pure PET (Comparative Example 1).

[0055] The copolymers prepared in Examples 1-3 are respectively denoted as PET-PDMS 2.5 , PET-PDMS5, PET-PDMS 10 , the copolymer prepared in Comparative Example 1 is PET, such as Figure 2 As shown, a, b, c, and d represent PET and PET-PDMS, respectively. 2.5 , PET-PDMS5, PET-PDMS 10 Scanning electron microscope image of the fiber membrane shows that with the increase of the amount of PDMS added, the spun fiber filaments become obviously thinner. When the PDMS addition amount increases to 10%, the spun fiber filaments become thinner but uneven and adhesion occurs. The reason may be that the addition of PDMS causes the viscosity of the spinning solution to change, thus causing the fiber fineness and pore size of the fiber membrane to change, and its performance is reduced.

[0056] like Figure 3 As shown, a, b, c, and d are PET and PET-PDMS, respectively. 2.5 , PET-PDMS5, PET-PDMS 10 The contact angles of polyester slices, e, f, g, and h are PET and PET-PDMS, respectively. 2.5 , PET-PDMS5, PET-PDMS 10 The fiber-film contact angle of PET slices showed a low WCA of 80.4°, which was determined by the intrinsic properties of PET. 2.5The slices showed a WCA of 86.4°, and the increase in WCA may be due to the introduction of PDMS, a low surface energy additive that improves the hydrophobicity of the material surface. In addition, after the introduction of 5% PDMS, the WCA continued to increase to 100.3°. However, with the further increase of PDMS content, the WCA decreased slightly. Compared with the original copolyester slices, the WCA of the PET nanofiber membrane increased from 80.4° to about 130.4°, which may be due to the basic rough structure of the nanofiber membrane. However, the WCA of the fiber membrane did not increase significantly with the increase of PDMS content, which may be because the roughness of the membrane surface has a greater impact on the surface wettability. However, the WCA of the fiber membrane obtained after the introduction of PDMS in the polymer still increased to 138° because the introduction of PDMS enriched the low surface energy Si on the fiber surface, improving its hydrophobicity.

[0057] The porosimeter was measured using a CFP 1500AE capillary flow porosimeter (Porous Materials Inc., USA).

[0058] The porosity of the prepared fiber membrane was tested and calculated as follows:

[0059]

[0060] in represents the bulk density of the polymer (calculated based on the component ratio), Represents the density of the electrospun fiber membrane. The sample size is kept at 2×3cm 2 .like Figure 4 As shown in the figure, with the increase of PDMS content, the maximum pore size of the fiber membrane becomes smaller and the porosity increases, but too much PDMS will cause the porosity of the fiber membrane to decrease slightly.

[0061] Comparative Examples 2-4

[0062] Comparative Examples 2-4 respectively provide a method for preparing a durable waterproof and breathable polyester film. Compared with Example 1, the only difference is that the electrospinning solution is prepared by blending pure PET and PDMS in different mass ratios, and the mass ratios of PET and PDMS are 100:25, 100:50, and 100:75, respectively. The other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0063] like Figure 5As shown, the blending method can improve its hydrophobicity to a certain extent, but the application of blending technology still faces some challenges. Since the two polymers are mixed together by physical mixing, the compatibility between different polymers is poor, resulting in phase separation inside the fiber, affecting the mechanical properties and stability of the fiber, and causing performance degradation, poor compatibility, and easy component separation during use. The present invention uses copolymerization to combine different monomer units together through chemical reactions to form a single polymer chain, which has better compatibility and uniformity, and can provide more excellent mechanical properties and stability.

[0064] In summary, the present invention provides a durable waterproof and breathable polyester film and a preparation method thereof, wherein a hydrophobic copolyester is prepared by copolymerizing a dibasic acid, a diol, and a hydroxy silicone oil monomer containing different side group substituents, and the hydrophobic properties of the copolyester are precisely controlled by adjusting the side group functional groups and the length of the chain segments. In addition, by combining the electrospinning technology, key parameters such as the pore structure, porosity, and specific surface area of ​​the nanofibers are regulated, thereby realizing the preparation of a waterproof and breathable polyester film with intrinsic modification.

[0065] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a durable waterproof and breathable polyester film, characterized in that: The following steps are involved: S1. Add the first monomer and the second monomer into a reactor for esterification reaction, add the third monomer after the esterification is completed, react for 0.5 to 1 hour under normal pressure, and then perform polycondensation reaction, slice the obtained copolymer to obtain modified polyester slices; the first monomer is PTA, the second monomer is EG, and the third monomer is an organosilicon reagent; S2. dissolving the polyester chips obtained in step S1 in a TFA / DCM mixed solvent, stirring at room temperature for a predetermined time to prepare an electrospinning solution, and electrospinning the electrospinning solution to obtain a durable waterproof and breathable polyester film.

2. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S1, the general structural formula of the third monomer is In the formula, R is C0~C 20 R1 and R2 are independently methyl, phenyl or C3~C 10 Long chain alkyl; X is O or NH; m is a positive integer.

3. The method for preparing a durable waterproof and breathable polyester film according to claim 2, characterized in that: The amount of the third monomer added is 2.5-10% of the mass of the first monomer.

4. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S1, the molar ratio of the first monomer to the second monomer is 1:(1-1.5).

5. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S1, the esterification reaction also requires the addition of a catalyst, wherein the catalyst is Sb2O3, and the addition amount is 400-600 ppm.

6. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S1, the reaction temperature of the esterification reaction is 240-260°C.

7. The method for preparing a durable waterproof and breathable polyester film according to claim 6, characterized in that: When the water output of the esterification reaction reaches 90% of the theoretical water output, the esterification reaction is stopped.

8. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S1, the specific reaction conditions of the polycondensation reaction are: slowly evacuating to 80-100 Pa within 1-3 hours, heating the system to 270-280° C., and reacting for 1-2 hours.

9. The method for preparing a durable waterproof and breathable polyester film according to claim 1, characterized in that: In step S2, the mass ratio of TFA to DCM in the TFA / DCM mixed solvent is (4-8):1; and the stirring time is 10-14 hours.

10. A durable waterproof and breathable polyester film, characterized in that: The durable waterproof breathable polyester film is prepared by the preparation method of any one of claims 1 to 9, wherein the durable waterproof breathable polyester film has a thickness of 65 to 75 μm.

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