BOPET (Biaxially Oriented Polyethylene Terephthalate) film super-hydrophilic-antistatic modification method based on aqueous system

Abstract

The invention discloses a water-based system-based BOPET (Biaxially Oriented Polyethylene Terephthalate) film super-hydrophilic-antistatic modification method, which comprises the following steps: mixing polyethyleneimine, polyisocyanate, a conductive filler and a water-based solvent to obtain a modified solution; and distributing the modification liquid on the surface of the BOPET film, and then carrying out heat treatment to obtain the super-hydrophilic-antistatic BOPET film. According to the invention, a hydrophilic and stable cross-linked network is constructed by polyethyleneimine and polyisocyanate, and a conductive network is formed by using the conductive filler, so that surface static charges are quickly released, and the modified BOPET film has super-hydrophilicity and antistatic property at the same time. Meanwhile, the introduction of the conductive filler can increase the roughness of the surface of the BOPET film, so that the surface energy is obviously improved, the tensile strength of the BOPET film is not damaged, and the water-resistant stability and adhesiveness of the coating can also be ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of BOPET film materials, and particularly relates to a super-hydrophilic and antistatic modification method for BOPET films based on an aqueous system. Background Art

[0002] Polyethylene terephthalate (PET) has excellent mechanical properties, abrasion resistance, etc., and is widely used in various civilian and military fields. Among them, biaxially oriented polyethylene terephthalate (BOPET) film has become the preferred material for industrial applications due to its excellent mechanical strength and optical properties.

[0003] In practical applications, BOPET films usually require functional coatings to endow them with scene applicability. For example, optical films for electronic displays require high surface energy to adhere antireflection coatings, and at the same time need to be antistatic to prevent dust adsorption and electrostatic discharge damage; medical sterile packaging requires hydrophilicity to be compatible with high-temperature sterilization processes and relies on antistatic properties to avoid particulate contamination; printing substrates require high surface energy to improve ink adhesion and at the same time need to prevent electrostatic problems during the printing process. However, existing functional coatings generally have problems such as easy peeling and adhesive layer shedding. The main reasons are that the PET molecular chain contains a rigid benzene ring structure, and the polarity of the ester group is weakened by molecular symmetry. In addition, as a crystalline polymer, a highly oriented surface structure is formed during the biaxial stretching process. These factors together result in a low surface energy (about 36 mN / m), poor adhesion to coatings, and easy electrostatic accumulation on the surface.

[0004] Therefore, there is an urgent need to surface-treat BOPET films to optimize their surface chemical properties. Precoating treatment is a commonly used method for surface modification of BOPET films, which mainly changes the surface characteristics of the films by physical or chemical means. However, existing methods often have difficulty in ensuring the water resistance stability and adhesion performance of the coatings while achieving super-hydrophilicity on the surface of BOPET films. Summary of the Invention

[0005] The purpose of the present invention is to endow super-hydrophilicity on the surface by virtue of the abundant amino groups in the main polymer structure of polyethyleneimine, and effectively improve the surface energy of the modified BOPET film. At the same time, polyethyleneimine and polyisocyanate react through -NH2 and -NCO groups to form a stable urea bond crosslinking network, ensuring the water resistance stability and adhesion of the coating. In addition, the introduction of conductive fillers forms a conductive network to achieve rapid movement and release of static charges. Solve the problems of shedding and glue dropping of the functional coating of BOPET film and electrostatic accumulation on the surface of BOPET film.

[0006] To achieve the above purpose, the present invention provides a super-hydrophilic and antistatic modification method for BOPET films in an aqueous system, including, Mix polyethyleneimine, polyisocyanate, conductive filler and aqueous solvent to obtain a modified liquid; Distribute the modified liquid on the surface of the BOPET film and then perform heat treatment to obtain a superhydrophilic and antistatic BOPET film.

[0007] Furthermore, the mass ratio of the polyethyleneimine, polyisocyanate, and conductive filler is 1-10:1-2:0.005-0.5.

[0008] Furthermore, the solid content of the modified liquid is 5%-35% and the pH is 7.0±0.2.

[0009] In the present invention, the thickness of the BOPET film does not need to be strictly limited and can be the conventional thickness of commercially available products. Exemplarily, the thickness is about 50-60 μm.

[0010] It should be noted that after mixing polyethyleneimine, polyisocyanate, conductive filler and aqueous solvent, a mixed system is obtained. Subsequently, the pH and solid content of the mixed system are adjusted. The reagent for adjusting the pH does not need to be strictly limited and can be common low-boiling acids, bases or buffer solutions, etc. The pH adjustment reagent will not be elaborated in the present invention and can be selected by oneself. Then, a mechanical mixing method such as stirring or ultrasonic is used to make the mixed system uniformly dispersed; finally, a modified liquid with a pH of 7.0±0.2 and a solid content of 5%-35% is obtained.

[0011] Furthermore, the aqueous solvent does not need to be strictly limited and can be exemplarily selected as at least one of water, ethanol, propylene glycol, glycerol, and propylene glycol methyl ether; preferably, water is used as the aqueous solvent.

[0012] Furthermore, the thickness of the modified liquid distributed on the surface of the BOPET film is 10-100 μm.

[0013] Furthermore, the heat treatment is carried out at 50-150 °C for 10-180 min.

[0014] Furthermore, the polyisocyanate is polymerized from at least one of the monomers hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), and toluene diisocyanate (TDI), and is a water-soluble system after polymerization. Polyisocyanate is a compound containing multiple isocyanate groups, and it includes types such as blocked HDI and ionic MDI. It can be directly purchased as a commercially available product or prepared by oneself, and is a conventional isocyanate curing agent, such as commercially available Hafotex ®WH-1993 and Duranate WA21-100.

[0015] Furthermore, the conductive filler includes at least one of carbon nanotubes, graphene, and antimony tin oxide.

[0016] Furthermore, the BOPET film is also subjected to corona treatment; The corona treatment is carried out at 1 - 4V and the number of times is 1 - 5 times.

[0017] The present invention also provides a superhydrophilic - antistatic BOPET film, which is obtained by the superhydrophilic - antistatic modification method of the BOPET film of the above - mentioned aqueous system.

[0018] The present invention also provides the application of the above - mentioned superhydrophilic - antistatic BOPET film in the fields of printing, flexible electronic devices, and sterile medical packaging.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention constructs a hydrophilic and stable cross - linked network with polyethyleneimine and polyisocyanate, and at the same time forms a conductive network with conductive fillers to quickly release surface static charges, so that the modified BOPET film has both superhydrophilicity and antistatic properties.

[0020] Compared with the unmodified BOPET film, the surface energy of the modified BOPET film is significantly increased. After forming a polyethyleneimine - based covalent cross - linked network on the surface of the BOPET film, the content of polar groups on the surface of the BOPET film is increased. At the same time, the introduction of conductive fillers can increase the surface roughness of the BOPET film, so the surface energy is significantly improved, and it will not damage the tensile strength of the BOPET film, and can also ensure the water resistance stability and adhesion of the coating.

[0021] The method of the present invention adopts an environmentally friendly aqueous phase treatment process, which does not require complex equipment or expensive reagents, and has potential industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 A line graph showing the water contact angle and diiodomethane contact angle of the BOPET film materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2; Figure 2 A diagram showing the surface energy test results of the BOPET film materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2; Figures 3a - 3c Optical microscope photos of the superhydrophilic - antistatic BOPET films obtained from Example 1, Example 2, and Comparative Example 2 are respectively shown; Figures 4b - 4c Optical microscope photographs of the BOPET film materials of Example 1, Example 2 and Comparative Example 2 after being immersed in water for 40 h are respectively shown. Detailed implementation manners

[0024] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the specific embodiments of the present invention and the specification drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1 A method for superhydrophilic-antistatic modification of a BOPET film in an aqueous system includes the following steps: (1) Perform corona pretreatment on a BOPET film with a thickness of 55 μm: set the voltage to 3 V and the number of corona times to 1 time; (2) Prepare a modification liquid: mix polyethyleneimine, blocked HDI and carbon nanotubes at a mass ratio of 1:1:0.005, use deionized water as a solvent to obtain a mixed system, and adjust the pH of the mixed system to 7.0 and the solid content to 20%; stir mechanically at 100 rpm for 1 h until the mixed system is uniformly dispersed to obtain a modification liquid; (3) Coat the modification liquid to obtain a modification coating: set the coating thickness to 50 μm, use a coating roller to coat the modification liquid obtained in step (2) on the surface of the BOPET film; transfer the coated BOPET film to a constant temperature oven at 100 °C and keep it warm for reaction for 30 min to obtain a superhydrophilic-antistatic BOPET film.

[0027] Example 2 A method for superhydrophilic-antistatic modification of a BOPET film in an aqueous system includes the following steps: (1) Perform corona pretreatment on a BOPET film with a thickness of 55 μm: set the voltage to 3 V and the number of corona times to 1 time; (2) Preparation of the modified liquid: Mix polyethyleneimine, blocked HDI, and carbon nanotubes in a mass ratio of 2:1:0.04, use deionized water as the solvent to obtain a mixed system, and adjust the pH of the mixed system to 7.0 and the solid content to 15%; Stir mechanically at 100 rpm for 1 h until the mixed system is evenly dispersed to obtain the modified liquid; (3) Coating the modified liquid to obtain a modified coating: Set the coating thickness to 50 μm, and use a coating roller to coat the modified liquid obtained in step (2) on the surface of the BOPET film; Transfer the coated BOPET film to a constant temperature oven at 90 °C and keep it warm for 50 min to obtain a superhydrophilic-antistatic BOPET film.

[0028] Comparative Example 1 It is the BOPET film after corona treatment in steps (1) of Example 1 and Example 2.

[0029] Comparative Example 2 (1) Perform corona pretreatment on a BOPET film with a thickness of 55 μm: Set the voltage to 3 V and the number of corona times to 1 time; (2) Preparation of the modified liquid: Mix polyethyleneimine and blocked HDI in a mass ratio of 20:1, use deionized water as the solvent to obtain a mixed system, and adjust the pH of the mixed system to 7.0 and the solid content to 15%; Stir mechanically at 100 rpm for 1 h until the mixed system is evenly dispersed to obtain the modified liquid; (3) Coating the modified liquid to obtain a modified coating: Set the coating thickness to 50 μm, and use a coating roller to coat the modified liquid obtained in step (2) on the surface of the BOPET film; Transfer the coated BOPET film to a constant temperature oven at 90 °C and keep it warm for 50 min to obtain a superhydrophilic-antistatic BOPET film.

[0030] Test Example The water contact angle and diiodomethane contact angle of the BOPET film materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were tested. From Figure 1 It can be seen that the water contact angles of the BOPET films obtained in Example 1, Example 2, and Comparative Example 2 are 0. Generally, it is considered that when the water contact angle is lower than 10°, the material surface has superhydrophilicity. These results show that the water contact angle of the BOPET film in Comparative Example 1 is close to 60°, while the water contact angles of the BOPET films obtained by the modification treatments in Example 1, Example 2, and Comparative Example 2 are all 0, and they all have superhydrophilicity.

[0031] Figure 2 The surface energy data in the middle was obtained through Figure 1 data calculation, and the calculation process is as follows: ; ; Among them, , and are the surface energy, the polar component of the surface energy, and the dispersion component of the BOPET film, respectively; , and are the surface energy, the polar component of the surface energy, and the dispersion component of the test liquid, respectively; θ is the contact angle between the test liquid and the surface of the BOPET film.

[0032] The surface energy, the polar component of the surface energy, and the dispersion component of the polar test liquid deionized water are 72.8 mN·m -1 , 51.0 mN·m -1 and 21.8 mN·m -1 , respectively. The surface energy, the polar component of the surface energy, and the dispersion component of the non-polar test liquid diiodomethane are 50.8 mN·m -1 , 0.0 mN·m -1 and 50.8 mN·m -1 , respectively.

[0033] It can be seen from Figure 2 that the surface energies of the BOPET film materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are 80.2 mN / m, 79.40 mN / m, 56.4 mN / m, and 77.7 mN / m, respectively. It can be seen that the surface energy of the BOPET film obtained by the modification treatment in Example 1 and Example 2 is significantly improved.

[0034] The surface resistivities of the BOPET film materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were tested, and the results are shown in Table 1. It can be seen that the introduction of conductive fillers forms a conductive network, significantly improving the conductive performance of the BOPET film material and endowing the modified BOPET film with antistatic properties.

[0035] Table 1 Surface Resistivity Results

[0036] The adhesion of the surface modification coatings of the film materials of Example 1, Example 2, and Comparative Example 2 was tested. The adhesion test of the coating: Adhesion refers to the bonding ability between the coating and the BOPET film material. The adhesion between the BOPET film and the coating was tested according to ASTM D3359. Use 3M tape to stick on the surface and stay for 2 min, and finally quickly tear off the 3M tape. The adhesion ability of the coating was characterized by the number of squares remaining on the BOPET film. The results are shown in Table 2.

[0037] Table 2 Adhesion Test Results

[0038] The appearance photos of the superhydrophilic-antistatic BOPET films obtained in Example 1, Example 2 and Comparative Example 2 are respectively as Figures 3a - 3c shown. The superhydrophilic-antistatic BOPET films obtained in Example 1, Example 2 and Comparative Example 2 were respectively soaked in water for 40 h, and the appearance structure of the soaked BOPET films was observed. From Figures 4a - 4c it can be seen that after soaking in water, the phenomenon of surface coating peeling of the superhydrophilic-antistatic BOPET film in Comparative Example 2 is very obvious. The adhesion test in Table 2 also shows that its coating adhesion is poor, and the adhesion grade is 0; while after soaking in the aqueous solution, there is no obvious change on the surface of the superhydrophilic-antistatic BOPET films in Example 1 and Example 2, and the adhesion test also shows that the coating adhesion is good, and the adhesion grade is 4B, which indicates that the surface modification coating has good water resistance stability. This is because under the condition of appropriate ratio, polyethyleneimine reacts with polyisocyanate to form a stable urea bond crosslinking network, ensuring the water resistance stability and adhesion of the coating. In addition, as shown in Table 3, the tensile strength of the superhydrophilic-antistatic BOPET films in Example 1 and Example 2 can both reach 230 MPa without damage.

[0039] Table 3 Tensile Strength Test Results

[0040] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for superhydrophilic and antistatic modification of BOPET films in an aqueous system, characterized in that, Including, Mixing polyethyleneimine, polyisocyanate, conductive filler and aqueous solvent to obtain a modified liquid; Distributing the modified liquid on the surface of a BOPET film and then performing heat treatment to obtain a superhydrophilic-antistatic BOPET film.

2. The superhydrophilic-antistatic modification method of the BOPET film in the aqueous system according to claim 1, characterized in that, The mass ratio of the polyethyleneimine, polyisocyanate, and conductive filler is 1-10:1-2:0.005-0.

5.

3. The superhydrophilic and antistatic modification method of BOPET film for aqueous system according to claim 1, characterized in that, The solid content of the modified liquid is 5%-35% and the pH is 7.0±0.

2.

4. The super-hydrophilic and antistatic modification method of BOPET film in the aqueous system according to claim 1, characterized in that The thickness of the modified liquid distributed on the surface of the BOPET film is 10-100 μm.

5. The superhydrophilic and antistatic modification method of BOPET film in the aqueous system according to claim 1, characterized in that, The heat treatment is carried out at 50-150 °C for 10-180 min.

6. The superhydrophilic and antistatic modification method of BOPET film for aqueous system according to claim 1, characterized in that, The polyisocyanate is obtained by polymerizing at least one of the monomers hexamethylene diisocyanate, diphenylmethane diisocyanate, and toluene diisocyanate, and is a water-soluble system after polymerization.

7. The superhydrophilic and antistatic modification method of the BOPET film in the aqueous system according to claim 1, characterized in that, The conductive filler includes at least one of carbon nanotubes, graphene, and antimony tin oxide.

8. The superhydrophilic and antistatic modification method of BOPET film for aqueous system according to any one of claims 1-7, characterized in that, The BOPET film is also subjected to corona treatment; The corona treatment is carried out at 1-4 V and the number of times is 1-5 times.

9. A superhydrophilic and antistatic BOPET film, characterized in that, Obtained by the method for superhydrophilic-antistatic modification of a BOPET film of the aqueous system according to any one of claims 1-9.

10. Use of a superhydrophilic-antistatic BOPET film as claimed in the claim in the fields of printing, flexible electronic devices, and sterile medical packaging.

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