DE112023004825T5 - ANTISTATIC FILM AND METHOD FOR ITS PRODUCTION - Google Patents

Abstract

The present invention belongs to the field of antistatic technology and, more particularly, relates to an antistatic film and a method for producing the same. The antistatic film comprises a substrate and at least one antistatic layer disposed on one side of the substrate. The antistatic layer is subjected to transverse stretching and then bonding in synchronization with the substrate to obtain the antistatic film. The antistatic layer comprises a conductive material, a modified polyurethane-acrylate copolymer resin, a crosslinking agent, and deionized water. The antistatic layer of the present invention uses the modified polyurethane-acrylate copolymer resin, thereby reducing the resistance change after use of the layer and achieving excellent antistatic weather resistance.

Description

Technical area

The present invention belongs to the field of antistatic technology and particularly relates to an antistatic film and a method for producing the same.

State of the art

Optical films in LCD displays are becoming increasingly widely used. During transportation and deep processing, these optical films can become contaminated due to electrostatic effects, leading to various drawbacks in the deep processing process and compromising the overall quality of the optical films. Therefore, an antistatic protective film must be applied to the surface of the optical films.

Currently, antistatic films can be divided into two types: internally coated and coated. There are two coating methods for coated antistatic films: offline coating and inline coating. Since inline-coated antistatic films have high resistance and therefore limited applications, offline-coated antistatic films are more widely used. Inline coating of antistatic films is achieved by applying an antistatic coating solution to the film surface during the manufacturing process. However, on the one hand, the coating thickness is limited and remains very thin, usually in the range of a few tens of nanometers. On the other hand, the films undergo 3-5 times stretching after coating, which can lead to a reduction or even complete loss of antistatic properties. Therefore, very high requirements are placed on the performance of the coating material. Therefore, antistatic films used in the release film and protective film industries are mainly produced by offline methods.

However, existing antistatic films in the state of the art have the problem of poor antistatic weather resistance.

In view of this, the present invention is presented.

Contents of the present invention

Antistatic weather resistance is closely related to the change in resistance of the antistatic film. After a certain period of use, the resistance of the antistatic film changes. The greater the change in resistance, the worse the antistatic weather resistance; the smaller the change in resistance, the better the antistatic weather resistance.

To solve the technical problems of the prior art, the present invention provides an antistatic film and a method for producing the same. The antistatic layer of the present invention uses a modified polyurethane-acrylate copolymer resin, which reduces the change in resistance after use of the layer and achieves excellent antistatic weather resistance.

The present invention includes the following technical solutions:

According to a first aspect of the present invention, an antistatic film is provided comprising a substrate and at least one antistatic layer disposed on one side of the substrate. The antistatic layer is subjected to transverse stretching and then fixing in synchronization with the substrate to obtain the antistatic film. The antistatic layer comprises a conductive material, a modified polyurethane-acrylate copolymer resin, a crosslinking agent, and deionized water.

• Leitfähiges Material: 5 % bis 20 %;
• modifiziertes Polyurethan-Acrylat-Copolymerharz: 5 % bis 20 %;
• Vernetzungsmittel: 0,1 % bis 5 %;
• Deionisiertes Wasser: 55 % bis 89,9 %.

Furthermore, the antistatic layer contains the following mass fractions of raw materials:

• Conductive material: 5% to 20%;
• modified polyurethane-acrylate copolymer resin: 5% to 20%;
• Crosslinking agent: 0.1% to 5%;
• Deionized water: 55% to 89.9%.

Furthermore, a process for producing the modified polyurethane-acrylate copolymer resin comprises:

Adding isocyanate to polyol and conducting a reaction while heating;

Adding a chain extender and carrying out a reaction;

Adding diethylenetriamine, a low molecular weight crosslinking agent and a solution of maleic anhydride in acetone sequentially and carrying out a reaction under heating;

Adding a sodium hydroxide solution and keeping it at a constant temperature;

Adding an emulsifier and water while stirring, then adding a butyl acrylate solution with an initiator and carrying out a reaction while heating;

Cool to obtain the modified polyurethane-acrylate copolymer resin.

Furthermore, the isocyanate comprises at least one of isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate.

Furthermore, the initiator is azobisisobutyronitrile.

Furthermore, the low molecular weight crosslinking agent is trimethylolpropane.

Furthermore, the antistatic layer has a thickness between 5 and 2 µm.

Furthermore, the conductive material is one or more of carbon nanotube powder, polythiophene particles, polyaniline powder, and conductive metals; or the conductive material is one or more of polythiophene dispersions, carbon nanotube dispersions, polyaniline dispersions, silver paste, and silver threads.

Furthermore, the crosslinking agent is one of oxazolines, isocyanates, azapyridines and melamines.

According to a second aspect of the present invention, there is provided a method for producing an antistatic film, which method serves to produce the antistatic film described above. The method comprises the following steps:

Introducing a substrate raw material into an extrusion system for melting and extruding a substrate melt;

Forming the substrate melt on a cooling roll into an amorphous cast plate;

Subjecting the cooled cast plate, after preheating, to a 3.0 to 5.0-fold longitudinal stretching to obtain a film web;

Applying a coating solution for the antistatic layer to one side of the film web;

Subjecting the film web coated with the coating solution to 3.0 to 5.0 times transverse stretching after preheating to obtain a film;

Heat-setting the film to obtain the antistatic film.

• 1. In der antistatischen Schicht der vorliegenden Erfindung wird das modifizierte Polyurethan-Acrylat-Copolymerharz verwendet, wodurch nach Einsatz der Schicht die Widerstandsänderung reduziert und eine hervorragende antistatische Witterungsbeständigkeit erreicht wird.
• 2. Bei dem erfindungsgemäßen Verfahren wird die Beschichtungslösung für die antistatische Schicht, hergestellt aus dem modifizierten Polyurethan-Acrylat-Copolymerharz, wässerigen leitfähigen Material und Vernetzungsmittel, durch Inline-Beschichtung auf dem Substrat aufgetragen. Gleichzeitig wird sie mit dem Substrat synchron der Querstreckung und Fixierung unterzogen, wobei durch thermische Aushärtung eine dreidimensionale Netzwerkstruktur gebildet wird. Dadurch weist die erhaltene antistatische Folie mit einem Oberflächenwiderstand von 10⁴ Ω bis 10¹¹ Ω eine hervorragende Witterungsbeständigkeit und antistatische Eigenschaften auf.
• 3. Das in der vorliegenden Erfindung beschriebene modifizierte Polyurethan-Acrylat-Copolymerharz vereint die Vorteile von Polyurethan und Polyacrylat, ist sicher und umweltfreundlich, weist hervorragende Folienbildungseigenschaften sowie ausgezeichnete physikalisch-mechanische Eigenschaften auf. Durch Inline-Beschichtung, Streckung und Fixierung bildet es mit dem Antistatikum ein interpenetrierendes Netzwerk. Die Beschichtung mit dem interpenetrierenden Polymernetzwerk weist bessere optische Eigenschaften auf. Um die Witterungsbeständigkeit und die antistatischen Eigenschaften der wässrigen antistatischen Beschichtungslösung zu erhöhen, wird das wässrige modifizierte Polyurethan-Acrylat-Copolymerharz als interpenetrierendes Polymernetzwerk verwendet, das Eigenschaften wie niedrige Viskosität und steuerbare Molekularstruktur aufweist.
• 4. In der vorliegenden Erfindung wird durch molekulares Strukturdesign 5Polyacrylharz als gemischtes Hartsegment in die Molekülkettensegmente von Polyurethan-Kautschuk eingebracht, wodurch die Vernetzungswirkung verbessert wird und die Beschichtung hervorragende antistatische Eigenschaften sowie Witterungsbeständigkeit aufweist. Gleichzeitig wird das modifizierte Polyurethan-Acrylat-Copolymerharz zusammen mit dem wässrigen leitfähigen Polymermaterial durch Inline-Beschichtung mit dem Substrat synchron der Querstreckung und Fixierung unterzogen, wobei durch die thermische Aushärtung die dreidimensionale Netzwerkstruktur gebildet wird, die dichte leitfähige Pfade ausbildet. Die erhaltene antistatische Folie weist einen Oberflächenwiderstand von 10⁴ Ω bis 10¹¹ Ω auf und besitzt ausgezeichnete antistatische Eigenschaften.

Using the above-mentioned technical solutions, the present invention has the following advantages:

• 1. The antistatic layer of the present invention uses the modified polyurethane-acrylate copolymer resin, which reduces the resistance change after the layer is used and achieves excellent antistatic weather resistance.
• 2. In the process of the present invention, the coating solution for the antistatic layer, made of the modified polyurethane-acrylate copolymer resin, aqueous conductive material, and crosslinking agent, is applied to the substrate by inline coating. At the same time, it is subjected to transverse stretching and fixation synchronously with the substrate, forming a three-dimensional network structure through thermal curing. As a result, the resulting antistatic film with a surface resistance of 10 ⁴ Ω to 10 ¹¹ Ω exhibits excellent weather resistance and antistatic properties.
• 3. The modified polyurethane-acrylate copolymer resin described in the present invention combines the advantages of polyurethane and polyacrylate, is safe and environmentally friendly, has excellent film-forming properties, and excellent physico-mechanical properties. Through inline coating, stretching, and fixation, it forms an interpenetrating network with the antistatic agent. The coating with the interpenetrating polymer network exhibits superior optical properties. To enhance the weather resistance and antistatic properties of the aqueous antistatic coating solution, the aqueous modified polyurethane-acrylate copolymer resin is used as the interpenetrating polymer network, which has properties such as low viscosity and controllable molecular structure.
• 4. In the present invention, polyacrylic resin is incorporated as a mixed hard segment into the molecular chain segments of polyurethane rubber through molecular structural design, thereby improving the crosslinking effect and providing the coating with excellent antistatic properties and weather resistance. At the same time, the modified polyurethane-acrylate copolymer resin, together with the aqueous conductive polymer material, is synchronously subjected to transverse stretching and fixation by inline coating with the substrate. Thermal curing forms a three-dimensional network structure that forms dense conductive paths. The resulting antistatic film has a surface resistance of 10 ⁴ Ω to 10 ¹¹ Ω and possesses excellent antistatic properties.

Brief description of the drawings

• 1 ist eine schematische Darstellung der Struktur einer antistatischen Folie gemäß Ausführungsformen der vorliegenden Erfindung.

To more clearly illustrate the technical solutions of the embodiments of the present invention or the related art, an accompanying drawing necessary for describing the embodiments or related art is briefly presented below. It is obvious that the accompanying drawing in the following description illustrates only some embodiments of the present invention, and a person skilled in the art can obtain other accompanying drawings based on these drawings without exerting any creative effort.

• 1 is a schematic representation of the structure of an antistatic film according to embodiments of the present invention.

List of reference symbols: 1-Substrate, 2-Antistatic layer.

Detailed embodiments

Various embodiments or examples for implementing various features of the present invention are provided below. The specific examples of components and their arrangement described below are intended only to concisely illustrate the present invention and are to be understood as examples only, not as limitations on this invention.

To clarify the object, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the embodiments of the present invention are described clearly and completely below with reference to the attached drawings. Obviously, the described embodiments represent a portion of the embodiments of the present invention and not all embodiments. Starting from the embodiments of the present invention, all other embodiments that can be devised by a person skilled in the art without creative effort fall within the scope of the present invention.

Embodiment 1

This embodiment provides an antistatic film which, as in 1 shown, comprises a substrate and at least one antistatic layer arranged on one side of the substrate, wherein the anti The static layer is synchronously stretched and then fixed to the substrate to obtain the antistatic film. The antistatic layer comprises a conductive material, a modified polyurethane-acrylate copolymer resin, a crosslinking agent, and deionized water.

• Leitfähiges Material: 5 % bis 20 %;
• modifiziertes Polyurethan-Acrylat-Copolymerharz: 5 % bis 20 %;
• Vernetzungsmittel: 0,1 % bis 5 %;
• Deionisiertes Wasser: 55 % bis 89,9 %.

Furthermore, the antistatic layer contains the following mass fractions of raw materials:

• Conductive material: 5% to 20%;
• modified polyurethane-acrylate copolymer resin: 5% to 20%;
• Crosslinking agent: 0.1% to 5%;
• Deionized water: 55% to 89.9%.

If the proportion of conductive material is too low, the antistatic effect will be insufficient. If the proportion of conductive material is too high, the spreadability of the coating solution will decrease, the coating appearance will deteriorate, and the weather resistance will also be compromised. Therefore, the mass fraction of the conductive material is preferably between 5% and 25%. If the proportion of modified polyurethane-acrylate copolymer resin is too low, the film-forming effect of the conductive material on the film surface will be insufficient, the coating appearance will deteriorate, and the weather resistance will also be compromised. If the proportion of modified polyurethane-acrylate copolymer resin is too high, the conductive material will be over-enclosed, so that too little conductive material is exposed on the surface and the antistatic effect cannot be sufficiently exerted, resulting in insufficient antistatic performance. Therefore, the mass fraction of modified polyurethane-acrylate copolymer resin is preferably between 5% and 25%. If the crosslinking agent content is too low, the crosslinking density of the coating will be too low, reducing both the hardness and scratch resistance of the antistatic coating, as well as its weathering resistance. If the crosslinking agent content is too high, the stability of the coating solution will deteriorate, and an excess of small molecules will lead to excessive crosslinking, increasing the risk of precipitation at high temperatures. Therefore, the mass fraction of the crosslinking agent is preferably between 0.1% and 5%.

Furthermore, a process for producing the modified polyurethane-acrylate copolymer resin comprises:

Adding isocyanate to polyol and conducting a reaction while heating;

Adding a chain extender and carrying out a reaction;

Adding diethylenetriamine, a low molecular weight crosslinking agent and a solution of maleic anhydride in acetone sequentially and carrying out a reaction under heating;

Adding a sodium hydroxide solution and keeping it at a constant temperature;

Adding an emulsifier and water while stirring, then adding a butyl acrylate solution with an initiator and carrying out a reaction while heating;

Cool to obtain the modified polyurethane-acrylate copolymer resin.

Preferably, it comprises: adding isocyanate into polyol, heating to 75 to 85 °C and conducting a reaction for 1 to 3 hours;

Adding a chain extender and conducting a reaction for 1 to 3 hours;

Adding diethylenetriamine, a low molecular weight crosslinking agent and a solution of maleic anhydride in acetone sequentially, heating to 50 to 70 °C and carrying out a reaction for 1 to 2 hours;

Adding a sodium hydroxide solution and keeping at a temperature of 45 to 55 °C for 0.5 to 1.5 hours;

Adding an emulsifier and water with stirring, followed by adding a butyl acrylate solution containing an initiator, emulsifying for 30 minutes, heating to 75 to 85 °C, and reacting for 2.5 to 3.5 hours, repeatedly heating to 85 to 95 °C and reacting for 1 to 2 hours;

Cool to obtain the modified polyurethane-acrylate copolymer resin.

Furthermore, the isocyanate comprises at least one of isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate.

Furthermore, the initiator is azobisisobutyronitrile.

Furthermore, the low molecular weight crosslinking agent is trimethylolpropane.

If the antistatic layer is too thin, the antistatic agent concentration per unit area is low, resulting in a weaker antistatic effect. At the same time, there are fewer polar groups per unit area, which reduces weather resistance. If the antistatic layer is too thick, the antistatic agent concentration per unit area is high and the antistatic effect is excellent, but this can lead to a poorer coating appearance. Furthermore, the antistatic layer has a thickness between 5 and 2 µm.

Furthermore, the conductive material is one or more of carbon nanotube powder, polythiophene particles, polyaniline powder, and conductive metals; or the conductive material is one or more of polythiophene dispersions, carbon nanotube dispersions, polyaniline dispersions, silver paste, and silver threads.

This increases the crosslinking density of the antistatic coating and ensures that linear molecules are interconnected, creating a three-dimensional network structure. This leads to improved weather resistance, the formation of dense conductive pathways, and the maintenance of the stability of the antistatic solution. Furthermore, the crosslinking agent is a combination of oxazolines, isocyanates, azapyridines, and melamines.

Embodiment 2

This embodiment provides a method for producing an antistatic film. The method of this embodiment can be used to produce the antistatic film described in Embodiment 1 and comprises the following steps:

Introducing a substrate raw material into an extrusion system for melting and extruding a substrate melt;

Forming the substrate melt on a cooling roll into an amorphous cast plate;

Subjecting the cooled cast plate, after preheating, to a 3.0 to 5.0-fold longitudinal stretching to obtain a film web, wherein the 3.0 to 5.0-fold longitudinal stretching ensures that, on the one hand, a uniform thickness is guaranteed in the longitudinal direction and, on the other hand, the longitudinal stretching is not excessive, thereby avoiding excessive orientation, which would make film formation in a subsequent transverse stretching more difficult.

Applying a coating solution for the antistatic layer to one side of the film web;

Subjecting the film web coated with the coating solution to 3.0 to 5.0 times transverse stretching after preheating to obtain a film, wherein the 3.0 to 5.0 times transverse stretching ensures both uniform thickness in the transverse direction and tightness of the in-line applied carbon nanotube coating, thereby forming stable conductive paths, wherein if the stretching ratio is too low, the coating is too thick, the carbon nanotubes tend to bridge significantly and are unevenly distributed on the polyester film surface, while if the stretching ratio is too high, the coating breaks, the conductive paths are destroyed, and excellent antistatic properties cannot be formed.

Heat-setting the film to obtain the antistatic film.

Example 1

Preparation of the modified polyurethane-acrylate copolymer resin:

Isophorone diisocyanate was added to vacuum-dehydrated polypropylene glycol. After a reaction time of 1 hour at 75°C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 1 hour. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 50°C and allowed to react for 1 hour. An appropriate amount of NaOH solution was then added and kept at 45°C for 0.5 hour. A butyl acrylate solution containing azobisisobutyronitrile as the initiator was then added. After a certain pre-emulsification time, polymerization was carried out at 75°C for 2.5 hours. The mixture was then heated to 85°C and allowed to react for 1 hour. After cooling to room temperature, the modified polyurethane-acrylate copolymer resin was obtained.

Preparation of the coating solution for the antistatic layer:

5 g of aqueous polythiophene dispersion A200 (Agfa, with a mass fraction of 5% polythiophene in the dispersion), 5 g of modified polyurethane-acrylate copolymer resin, 89.9 g of deionized water, and 0.1 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare the coating solution for the antistatic layer.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared coating solution for the antistatic layer was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating method. After drying by heating, the film coated with the coating solution was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 5 nm.

Example 2

Preparation of the modified polyurethane-acrylate copolymer resin:

Diphenylmethane diisocyanate was added to vacuum-dehydrated polypropylene glycol. After a 3-hour reaction at 85°C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 3 hours. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 70°C and allowed to react for 2 hours. An appropriate amount of NaOH solution was then added and kept at 55°C for 1.5 hours. The PU, emulsifier, and water were then mixed and poured into a four-necked flask. After thorough stirring, a butyl acrylate solution containing azobisisobutyronitrile as the initiator was added. After a certain pre-emulsification time, the polymerization was carried out at 85°C for 3.5 hours. The mixture was then heated to 95°C and allowed to react for 2 hours. After cooling to room temperature, the modified polyurethane-acrylate copolymer resin was obtained.

Preparation of the coating solution for the antistatic layer:

12.5 g of aqueous polyaniline dispersion HS0394 (Nanhai Jiangshun Chemical Products, Foshan, with a mass fraction of 5% polyaniline in the dispersion), 12.5 g of modified polyurethane-acrylate copolymer resin, 72.5 g of water, and 2.5 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare the coating solution for the antistatic layer.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared coating solution for the antistatic layer was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the film coated with the coating solution was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 1 µm.

Example 3

Preparation of the modified polyurethane-acrylate copolymer resin:

Toluene diisocyanate was added to vacuum-dehydrated polypropylene glycol. After a 2-hour reaction at 80°C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 2 hours. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 60°C and allowed to react for 1.5 hours. An appropriate amount of NaOH solution was then added and kept at 50°C for 1 hour. The PU, emulsifier, and water were then mixed and poured into a four-necked flask. After thorough stirring, a butyl acrylate solution containing azobisisobutyronitrile as the initiator was added. After a certain pre-emulsification time, the polymerization was carried out for 3 hours at 80°C. The mixture was then heated to 90°C and allowed to react for 1.5 hours. After cooling to room temperature, the modified polyurethane-acrylate copolymer resin was obtained.

Preparation of the coating solution for the antistatic layer:

20 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 20 g of modified polyurethane-acrylate copolymer resin, 55 g of water, and 5 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare the coating solution for the antistatic layer.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared coating solution for the antistatic layer was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the film coated with the coating solution was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 2 µm.

Example 4

Preparation of the modified polyurethane-acrylate copolymer resin:

4,4'-Dicyclohexylmethane diisocyanate was added to vacuum-dehydrated polypropylene glycol. After 1.5 hours of reaction at 77.5 °C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 1.5 hours. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 55 °C and allowed to react for 1.25 hours. An appropriate amount of NaOH solution was then added and maintained at 47.5 °C for 0.75 hours. The PU, emulsifier, and water were then mixed and poured into a four-necked flask. After thorough stirring, a butyl acrylate solution containing azobisisobutyronitrile as the initiator was added. After a certain pre-emulsification time, polymerization was carried out at 77.5 °C for 2.75 hours. It was then heated to 87.5 °C and 1.25 The reaction was allowed to proceed for several hours. After cooling to room temperature, the modified polyurethane-acrylate copolymer resin was fully prepared.

Preparation of the coating solution for the antistatic layer:

16.25 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 16.25 g of modified polyurethane-acrylate copolymer resin, 64.25 g of water, and 3.25 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare the coating solution for the antistatic layer.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared coating solution for the antistatic layer was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the film coated with the coating solution was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 1.5 µm.

Example 5

Preparation of the modified polyurethane-acrylate copolymer resin:

Isophorone diisocyanate was added to vacuum-dehydrated polypropylene glycol. After a reaction time of 2.5 hours at 82.5 °C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 2.5 hours. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 65 °C and allowed to react for 1.75 hours. An appropriate amount of NaOH solution was then added and maintained at a temperature of 52.5 °C for 1.25 hours. The PU, emulsifier, and water were then mixed and poured into a four-necked flask. After thorough stirring, a butyl acrylate solution containing azobisisobutyronitrile as the initiator was added. After a specific pre-emulsification time, polymerization was carried out for 3.25 hours at 82.5 °C. It was then heated to 92.5 °C and allowed to react for 1.75 hours. After cooling to room temperature, the modified polyurethane-acrylate copolymer resin was obtained.

Preparation of the coating solution for the antistatic layer:

8.75 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 8.75 g of modified polyurethane-acrylate copolymer resin, 82.25 g of water, and 1.25 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare the coating solution for the antistatic layer.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared coating solution for the antistatic layer was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the film coated with the coating solution was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 0.5 µm.

Comparison example 1

Preparation of the antistatic coating solution:

8.75 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 8.75 g of polyurethane resin, 82.25 g of water, and 1.25 g of oxazoline crosslinker WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare an antistatic coating solution.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. The prepared antistatic coating solution was then applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the coated film was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 0.5 µm.

Comparison example 2

Preparation of the antistatic coating solution:

5 g of aqueous polythiophene dispersion A200 (Agfa, with a mass fraction of 5% polythiophene in the dispersion), 5 g of acrylic resin, 89.9 g of water, and 0.1 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier, producing an antistatic coating solution.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a suitable extrusion system, melted and extruded, and then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared antistatic coating solution was applied to one or both sides of the longitudinally stretched film by a gravure coating, bar coating, or dip coating process. After drying by heating, the coated film was stretched transversely at a stretch ratio of 3:1, then heat-set and wound to obtain the antistatic film with a dry film thickness of 5 nm.

Comparison example 3

Preparation of the antistatic coating solution:

20 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 10 g of polyurethane resin, 10 g of acrylic resin, 55 g of water, and 5 g of oxazoline crosslinker WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare an antistatic coating solution.

Production of the antistatic film:

First, crystallized and dried polyester chips were introduced into a corresponding extrusion system, melted and extruded, then cast onto a rotating chill roll. The cooled cast strip was preheated and stretched longitudinally at a stretch ratio of 3:1. Subsequently, the prepared antistatic coating solution was applied to one or both sides of the longitudinally stretched film by a process consisting of gravure coating, bar coating, or dip coating. After drying, the coated film was transversely direction with a stretch ratio of 3:1 and then heat-set and wound up to obtain the antistatic film with a dry film thickness of 2 µm.

Comparison example 4

Production of modified polyurethane-acrylate composite resin:

Isophorone diisocyanate was added to vacuum-dehydrated polypropylene glycol. After a reaction time of 2.5 hours at 82.5 °C, 2,2-bis(hydroxymethyl)propionic acid and butanediol were added, and the mixture was allowed to react for another 2.5 hours. Diethylenetriamine, epichlorohydrin, and a solution of maleic anhydride in acetone were then added dropwise. The mixture was heated to 65 °C and allowed to react for 1.75 hours. An appropriate amount of NaOH solution was then added and maintained at a temperature of 52.5 °C for 1.25 hours. The PU, emulsifier, and water were then mixed and poured into a four-necked flask. After thorough stirring, a butyl acrylate solution containing azobisisobutyronitrile as the initiator was added. After a specific pre-emulsification time, polymerization was carried out for 3.25 hours at 82.5 °C. It was then heated to 92.5 °C and allowed to react for 1.75 hours. After cooling to room temperature, a modified polyurethane-acrylate composite emulsion was obtained.

Preparation of the antistatic coating solution:

16.25 g of aqueous carbon nanotube dispersion ML1293 (JingKang Bio, with a mass fraction of 5% carbon nanotubes in the dispersion), 16.25 g of modified polyurethane-acrylate composite resin, 64.25 g of water, and 3.25 g of oxazoline crosslinking agent WS-700 (UN Chemical) were taken. They were homogeneously dispersed using a high-shear emulsifier to prepare an antistatic coating solution.

Production of the antistatic film:

The prepared antistatic coating solution was applied to one or both sides of a film (the coating and the film were not stretched synchronously) and then cured. After winding, the antistatic film with a dry film thickness of 5 nm was obtained.

1. (1) Oberflächenwiderstand (antistatische Schicht) wurde gemäß GB/T 33398 ermittelt;
2. (2) Prüfmethode der Witterungsbeständigkeit: Die hergestellte antistatische Folie wurde auf A4-Größe zugeschnitten und bei konstanter Temperatur und Luftfeuchtigkeit (85 °C, 85 % RH) für jeweils 200 h und 500 h gelagert. Anschließend wurde der Oberflächenwiderstand gemäß GB/T 33398 ermittelt.

The methods for testing the various properties are as follows:

1. (1) Surface resistance (antistatic layer) was determined according to GB/T 33398;
2. (2) Weather resistance test method: The prepared antistatic film was cut into A4 size and stored at constant temperature and humidity (85 °C, 85% RH) for 200 hours and 500 hours, respectively. The surface resistance was then determined according to GB/T 33398.

The test results can be seen in Table 1: Table 1: Test results of the working examples and comparative examples Examinations Surface resistance (Ω) Weather resistance test (Ω) 200 hours 500 hours Example 1 10 ⁶ Ω 10 ⁶ Ω 10 ⁶ Ω Example 2 10 ⁵ Ω 10 ⁵ Ω 10 ⁵ Ω Example 3 10 ⁴ Ω 10 ⁴ Ω 10 ⁴ Ω Example 4 10 ⁵ Ω 10 ⁵ Ω 10 ⁵ Ω Example 5 10 ⁶ Ω 10 ⁶ Ω 10 ⁶ Ω Comparison example 1 > 10 ¹² Ω > 10 ¹² Ω > 10 ¹² Ω Comparison example 2 10 ⁶ Ω > 10 ¹² Ω > 10 ¹² Ω Comparison example 3 > 10 ¹² Ω > 10 ¹² Ω > 10 ¹² Ω Comparison example 4 10 ⁶ Ω 10 ⁹ Ω > 10 ¹² Ω

From the comparison between Comparative Example 1 and Working Example 5, it is clear that when the modified polyurethane-acrylic resin was used in Working Example 5, compared with ordinary polyurethane, the carbon nanotube coating solution after in-line coating, biaxial stretching and fixing had a surface resistance of 10 ⁶ Ω, and at the same time, the carbon nanotube coating solution showed better weather resistance.

From the comparison between Comparative Example 2 and Working Example 1, it can be seen that when using the unmodified acrylic resin in Comparative Example 2, the conductive polythiophene polymer coating exhibited a surface resistance of >10 ⁶ Ω after inline coating, biaxial stretching, and fixation, but after the 200- and 500-hour aging tests, the surface resistance increased to >10 ¹² Ω. This significant change in resistance indicates poor weather resistance.

From the comparison between Comparative Example 3 and Working Example 3, it can be seen that in Comparative Example 3, a combination of polyurethane resin and acrylic resin was used, and the surface resistance was >10 ¹² Ω.

From the comparison between Comparative Example 4 and Working Example 4, it can be seen that the antistatic coating in Comparative Example 4 was not subjected to synchronous transverse stretching and bonding with the substrate. The surface resistance was 10 ⁶ Ω, but it increased to 10 ⁹ Ω after the 200-hour aging test. After the aging test, the surface resistance was consistently above 10 ⁹ Ω. This significant change in resistance indicates poor weather resistance.

From the comparison between Embodiment 3 and Embodiment 5, it can be seen that Embodiment 3 had a higher proportion of the modified polyurethane-acrylic resin in the coating than Embodiment 5. This results in a better dispersion of the carbon nanotubes, which leads to a significantly improved antistatic effect.

Table 1 shows that the antistatic films produced in the embodiments of the present invention are significantly improved compared to the antistatic films produced in the comparative examples in terms of both antistatic properties and the weather resistance of the antistatic layer. This demonstrates that the antistatic polyester film of the present invention not only exhibits excellent antistatic properties but also features excellent coating solution stability and good processability in continuous production. Thus, it has excellent application prospects.

To clarify the object, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the embodiments of the present invention are described clearly and completely below with reference to the attached drawings. Obviously, the described embodiments represent a portion of the embodiments of the present invention and not all embodiments. Starting from the embodiments of the present invention, all other embodiments that can be devised by a person skilled in the art without creative effort fall within the scope of the present invention.

Claims (10)

An antistatic film comprising a substrate (1) and at least one antistatic layer (2) arranged on one side of the substrate (1), wherein the antistatic layer is subjected to transverse stretching and then fixing synchronously with the substrate (1) to obtain the antistatic film, characterized in that the antistatic layer comprises a conductive material, a modified polyurethane-acrylate copolymer resin, a crosslinking agent and deionized water. Antistatic film according to Claim 1 , characterized in that the antistatic layer (2) has the following mass fractions of raw materials: conductive material: 5% to 20%; modified polyurethane-acrylate copolymer resin: 5% to 20%; crosslinking agent: 0.1% to 5%; deionized water: 55% to 89.9%. Antistatic film according to Claim 1 or 2 , characterized in that a process for producing the modified polyurethane-acrylate copolymer resin comprises the following steps: Adding isocyanate to polyol and conducting a reaction with heating; adding a chain extender and conducting a reaction; adding diethylenetriamine, a low-molecular-weight crosslinking agent, and a solution of maleic anhydride in acetone sequentially and conducting a reaction with heating; adding a sodium hydroxide solution and maintaining at a constant temperature; adding an emulsifier and water with stirring, then adding a butyl acrylate solution containing an initiator and conducting a reaction with heating; cooling to obtain the modified polyurethane-acrylate copolymer resin. Antistatic film according to Claim 3 , characterized in that the isocyanate comprises at least one of isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate. Antistatic film according to Claim 3 , characterized in that the initiator is azobisisobutyronitrile. Antistatic film according to Claim 3 , characterized in that the low molecular weight crosslinking agent is trimethylolpropane. Antistatic film according to Claim 1 or 2 , characterized in that the antistatic layer (2) has a thickness between 5 nm and 2 µm. Antistatic film according to Claim 1 or 2 , characterized in that the conductive material is one or more of carbon nanotube powder, polythiophene particles, polyaniline powder, and conductive metals; or the conductive material is one or more of polythiophene dispersions, carbon nanotube dispersions, polyaniline dispersions, silver paste, and silver threads. Antistatic film according to Claim 1 or 2 , characterized in that the crosslinking agent is one of oxazolines, isocyanates, azapyridines and melamines. A process for producing an antistatic film, characterized in that it is used to produce the antistatic film according to one of the Claims 1 until 9 wherein the method comprises the following steps: introducing a substrate raw material into an extrusion system for melting and extruding a substrate melt; forming the substrate melt on a chill roll into an amorphous cast sheet; subjecting the cooled cast sheet, after preheating, to 3.0 to 5.0 times longitudinal stretching to obtain a film web; applying a coating solution for the antistatic layer to one side of the film web; subjecting the film web coated with the coating solution, after preheating, to 3.0 to 5.0 times transverse stretching to obtain a film; heat-setting the film to obtain the antistatic film.