A composite antistatic film and preparation method thereof

Abstract

The present application discloses a kind of composite antistatic film and preparation method thereof, relate to the field of automobile parts film materials.Compound antistatic film includes core layer and outer layer, and core layer is made using toughening modified PET resin, and outer layer is made using antistatic PET resin;Toughening modified PET resin includes 100 weight portions of the first PET resin, 24.3 30.8 weight portions of hydroxyl-terminated polyurethane resin, 1.0 1.5 weight portions of the first hydroxy graphitized carbon nanotube, 8.8 10.4 weight portions of the first bis-oxazoline chain extender;Antistatic PET resin includes 100 weight portions of the second PET resin, 0.85 1.0 weight portions of the second hydroxy graphitized carbon nanotube, 3.5 4.8 weight portions of the second bis-oxazoline chain extender.The composite antistatic film of the present application has both toughness and antistatic property, can improve the forming efficiency of composite antistatic film, can also promote the rapid derivation of static electricity, improve the dustproofness of composite antistatic film.

Description

Technical Field

[0001] The present application relates to the field of automotive parts film materials, and in particular to a composite antistatic film and a preparation method thereof. Background Art

[0002] PET (polyethylene terephthalate) film is usually obtained by stretching after melt extrusion of PET resin, toughening agent and releasing agent. PET film has excellent physical and mechanical properties in a wide temperature range, and has good organic solvent resistance, weather resistance and scratch resistance, and can protect auto parts from being scratched. However, the existing PET film mainly has the following two shortcomings: the first, the poor film forming property of PET resin. In the process of producing PET film, PET film is easily broken, and molding efficiency is low. Although adding toughening agent can improve the film forming property of PET resin, the existing toughening agent is usually acrylonitrile-butadiene-styrene copolymer or styrene-butadiene thermoplastic elastomer. Acrylonitrile-butadiene-styrene copolymer or styrene-butadiene thermoplastic elastomer has poor compatibility with PET resin, and the improvement effect is limited. The second is the poor antistatic property of PET film, and dust is easily attached to the surface. Summary of the Invention

[0003] In order to improve the problems of easy breakage and poor antistatic properties of PET films during the molding process in the related art, the present application provides a composite antistatic film and a preparation method thereof.

[0004] In the first aspect, the present application provides a composite antistatic film using the following technical solutions:

[0005] A composite antistatic film comprises a core layer and outer layers composited to the upper and lower surfaces of the core layer, wherein the core layer is made of a toughened modified PET resin, and the outer layers are made of an antistatic PET resin; wherein, based on the raw materials, the toughened modified PET resin comprises 100 parts by weight of a first PET resin, 24.3-30.8 parts by weight of a hydroxyl-terminated polyurethane resin, 1.0-1.5 parts by weight of a first hydroxyl-graphitized carbon nanotube, and 8.8-10.4 parts by weight of a first bis-oxazoline chain extender;

[0006] The antistatic PET resin includes 100 parts by weight of a second PET resin, 0.85-1.0 parts by weight of a second hydroxy graphitized carbon nanotube, and 3.5-4.8 parts by weight of a second bisoxazoline chain extender.

[0007] The composite antistatic film in the present application comprises at least a core layer and outer layers composited on the upper and lower surfaces of the core layer. The difference between the core layer and the outer layer lies in that the raw material ratio is different and a hydroxyl-terminated polyurethane resin is added to the core layer.

[0008] The core layer is made of a toughened modified PET resin, in which the end-hydroxy polyurethane resin is used to improve toughness, and the first hydroxy graphitized carbon nanotubes are used to improve antistatic properties. The first bisoxazoline chain extender can react with the hydroxyl groups on the first PET resin, the end-hydroxy polyurethane resin, and the first hydroxy graphitized carbon nanotubes to improve the compatibility between the first PET resin, the end-hydroxy polyurethane resin, and the first hydroxy graphitized carbon nanotubes, which is conducive to obtaining a core layer with good toughness and antistatic properties, and can improve the molding efficiency of the composite antistatic film.

[0009] The outer layer is made of antistatic PET resin. In the antistatic PET resin, the second hydroxy graphitized carbon nanotubes are used to improve the antistatic property. The second bisoxazoline chain extender can react with the hydroxyl groups on the second PET resin and the second hydroxy graphitized carbon nanotubes to improve the compatibility between the second PET resin and the second hydroxy graphitized carbon nanotubes, which is conducive to obtaining an outer layer with good antistatic performance.

[0010] The outer layer may or may not contain a hydroxyl-terminated polyurethane resin. Omitting the hydroxyl-terminated polyurethane resin reduces costs and improves the stiffness of the composite antistatic film. Furthermore, in the present application, the core layer and the outer layer form a complete static-conducting network, promoting the rapid discharge of static electricity and improving the dustproofness of the composite antistatic film.

[0011] Optionally, the first PET resin and the second PET resin are American DuPont PT2251 or Korean SKBR8040.

[0012] Optionally, based on the raw materials, the hydroxyl-terminated polyurethane resin includes 58-64 parts by weight of isocyanate-terminated polyurethane prepolymer, 5.5-6.0 parts by weight of small molecule diol chain extender and 8.5-10.8 parts by weight of double-terminated hydroxypropyl silicone oil; the isocyanate-terminated polyurethane prepolymer is prepared from 30-40 parts by weight of polyester diol, 12.8-16.4 parts by weight of diisocyanate and 0.01-0.015 parts by weight of catalyst.

[0013] In the present application, the hydroxyl-terminated polyurethane resin is prepared by using isocyanate-terminated polyurethane prepolymer, small molecule diol chain extender and double-terminated hydroxypropyl silicone oil. Among them, the isocyanate-terminated polyurethane prepolymer is chain extended by the small molecule diol chain extender and the double-terminated hydroxypropyl silicone oil, which is beneficial to improving the problem of foaming and stratification of the composite antistatic film in the later stage due to the increase in melt viscosity of the toughened modified PET resin, the inability to discharge bubbles in the melt in time, or the existence of local extrusion unevenness during the melt extrusion process.

[0014] Optionally, the small molecule diol chain extender is at least one of propylene glycol, 1,4-butanediol, and neopentyl glycol.

[0015] Optionally, the molecular weight of the polyester diol is 1000-2000.

[0016] In the present application, the molecular weight of the polyester diol is controlled within the range of 1000-2000, which is beneficial to further improve the toughness of the hydroxyl-terminated polyurethane resin.

[0017] Optionally, the diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0018] Optionally, the catalyst is at least one of dibutyltin dilaurate and stannous octoate.

[0019] Optionally, the preparation method of the hydroxyl-terminated polyurethane resin comprises the following steps:

[0020] The polyester diol is heated to 45-55°C, and then diisocyanate and catalyst are added. The temperature is raised to 70-75°C under nitrogen protection and reacted for 3-4 hours to obtain an isocyanate-terminated polyurethane prepolymer;

[0021] Add a small molecule diol chain extender and a double-terminated hydroxypropyl silicone oil to the isocyanate-terminated polyurethane prepolymer, continue the reaction at 80-85°C for 3-4 hours, then evacuate, cool, and granulate to obtain a hydroxyl-terminated polyurethane resin.

[0022] In the present application, the above method for preparing the hydroxyl-terminated polyurethane resin has the characteristics of simple steps and good product stability.

[0023] Optionally, the diameter of the first hydroxyl-graphitized carbon nanotube and the second hydroxyl-graphitized carbon nanotube is 10-30 nm, and the length is 10-30 μm.

[0024] In the present application, the diameter of the first hydroxyl graphitized carbon nanotubes and the second hydroxyl graphitized carbon nanotubes are controlled to be 10-30 nm and the length is 10-30 μm, which is conducive to the uniform dispersion of the first hydroxyl graphitized carbon nanotubes and the second hydroxyl graphitized carbon nanotubes.

[0025] Optionally, the first bisoxazoline chain extender and the second bisoxazoline chain extender are at least one of dioxazoline and 2,2'-(1,3-phenylene)-dioxazoline.

[0026] Optionally, the thickness ratio of the core layer to the outer layer is 1:(1-1.5).

[0027] In a second aspect, the present application provides a method for preparing a composite antistatic film using the following technical solution:

[0028] A method for preparing a composite antistatic film comprises the following steps:

[0029] The first PET resin, the hydroxyl-terminated polyurethane resin, the first hydroxyl-graphitized carbon nanotubes and the first bisoxazoline chain extender are mixed, melt-extruded at 245-260° C., and pelletized to obtain a toughened modified PET resin;

[0030] The second PET resin, the second hydroxy graphitized carbon nanotubes and the second bisoxazoline chain extender are mixed, melt-extruded at 245-260° C., and pelletized to obtain an antistatic PET resin;

[0031] The toughened modified PET resin is fed into the extruder A, and the temperature of the extruder A is set at 265-280° C.;

[0032] The antistatic PET resin is fed into the extruder B, and the temperature of the extruder B is set at 265-280°C;

[0033] Connect the die distributor to extruders A and B. The melt from extruder B is evenly distributed to the upper and lower flow channels through the die distributor, and the melt from extruder A is distributed to the middle flow channel through the die distributor. The fluids in the three flow channels are co-extruded from the die lip and cast to obtain a cast sheet.

[0034] The cast sheet is stretched to obtain a composite antistatic film.

[0035] In the present application, the composite antistatic film prepared by the above method can obtain a composite antistatic film with good toughness and good antistatic properties.

[0036] In summary, this application has at least the following beneficial effects:

[0037] (1) The composite antistatic film in the present application comprises at least a core layer and an outer layer composited on the upper and lower surfaces of the core layer. The core layer is made of a toughened modified PET resin, wherein the toughened modified PET resin comprises a hydroxyl-terminated polyurethane resin for improving toughness, a first hydroxyl-graphitized carbon nanotube for improving antistatic properties, and a first bis-oxazoline chain extender capable of reacting with the hydroxyl groups on the first PET resin, the hydroxyl-terminated polyurethane resin, and the first hydroxyl-graphitized carbon nanotube to improve compatibility between the first PET resin, the hydroxyl-terminated polyurethane resin, and the first hydroxyl-graphitized carbon nanotube, thereby facilitating the formation of a core layer having good toughness and good antistatic properties, and improving the forming efficiency of the composite antistatic film. The outer layer is made of an antistatic PET resin, wherein the antistatic PET resin comprises a second hydroxyl-graphitized carbon nanotube for improving antistatic properties, and a second bis-oxazoline chain extender capable of reacting with the hydroxyl groups on the second PET resin and the second hydroxyl-graphitized carbon nanotube to improve compatibility between the second PET resin and the second hydroxyl-graphitized carbon nanotube, thereby facilitating the formation of an outer layer having good antistatic properties. The outer layer can be added with or without end-hydroxyl polyurethane resin. Not adding end-hydroxyl polyurethane resin is beneficial to reducing costs and making the composite antistatic film more stiff. It also promotes the rapid discharge of static electricity and improves the dustproofness of the composite antistatic film.

[0038] (2) In the present application, the hydroxyl-terminated polyurethane resin is prepared by using an isocyanate-terminated polyurethane prepolymer, a small molecule diol chain extender and a double-terminated hydroxypropyl silicone oil. The isocyanate-terminated polyurethane prepolymer is chain extended by the small molecule diol chain extender and the double-terminated hydroxypropyl silicone oil, which is beneficial to improving the problem of foaming and stratification of the composite antistatic film in the later stage due to the increase in melt viscosity of the toughened modified PET resin, the inability to discharge bubbles in the melt in time, or the existence of local extrusion unevenness during the melt extrusion process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of a composite antistatic film according to an embodiment of the present application.

[0040] Description of reference numerals:

[0041] 1. Core layer; 2. Outer layer. DETAILED DESCRIPTION

[0042] The present application is further described below in conjunction with specific experiments.

[0043] Preparation Example

[0044] [Preparation Example 1]

[0045] A hydroxyl-terminated polyurethane resin, calculated on the basis of raw materials, includes 58 kg of isocyanate-terminated polyurethane prepolymer, 5.5 kg of propylene glycol and 10.8 kg of double-terminated hydroxypropyl silicone oil HX-10 (Huaxiang Kejie), wherein the isocyanate-terminated polyurethane prepolymer is prepared from 30 kg of polycaprolactone diol with a molecular weight of 2000, 12.8 kg of isophorone diisocyanate and 0.01 kg of dibutyltin dilaurate.

[0046] In this preparation example, the preparation method of the hydroxyl-terminated polyurethane resin includes the following steps:

[0047] The polycaprolactone diol was heated to 45°C, and then isophorone diisocyanate and dibutyltin dilaurate were added, and the temperature was raised to 70°C under nitrogen protection for 4 hours to obtain an isocyanate-terminated polyurethane prepolymer;

[0048] Propylene glycol and double-terminated hydroxypropyl silicone oil were added to the isocyanate-terminated polyurethane prepolymer according to the ratio, and the reaction was continued at 80° C. for 4 hours, and then vacuumed, cooled, and granulated to obtain a hydroxyl-terminated polyurethane resin.

[0049] [Preparation Example 2]

[0050] A hydroxyl-terminated polyurethane resin, calculated on the basis of raw materials, includes 64 kg of isocyanate-terminated polyurethane prepolymer, 6.0 kg of 1,4-butanediol and 8.5 kg of double-terminated hydroxypropyl silicone oil HX-20 (Huaxiang Kejie), wherein the isocyanate-terminated polyurethane prepolymer is prepared from 40 kg of polycaprolactone diol with a molecular weight of 2000, 16.4 kg of diphenylmethane diisocyanate and 0.015 kg of dibutyltin dilaurate.

[0051] In this preparation example, the preparation method of the hydroxyl-terminated polyurethane resin includes the following steps:

[0052] The polycaprolactone diol was heated to 55°C, and then diphenylmethane diisocyanate and dibutyltin dilaurate were added, and the temperature was raised to 75°C under nitrogen protection for reaction for 3 hours to obtain an isocyanate-terminated polyurethane prepolymer;

[0053] 1,4-Butanediol and double-terminated hydroxypropyl silicone oil were added to the isocyanate-terminated polyurethane prepolymer according to the ratio, and the reaction was continued at 85°C for 3 hours. The mixture was then vacuumed, cooled, and granulated to obtain a hydroxyl-terminated polyurethane resin.

[0054] [Preparation Example 3]

[0055] A hydroxyl-terminated polyurethane resin, which differs from [Preparation Example 1] in that an equal amount of propylene glycol is used instead of the double-terminated hydroxypropyl silicone oil.

[0056] [Preparation Example 4]

[0057] A hydroxyl-terminated polyurethane resin, which differs from [Preparation Example 1] in that propylene glycol is replaced by an equal amount of dihydroxypropyl silicone oil.

[0058] Example

[0059] [Example 1]

[0060] A composite antistatic film, referring to Figure 1 The invention relates to a composite material comprising a core layer 1 and an outer layer 2 composited on the upper and lower surfaces of the core layer 1. The thickness ratio of the core layer 1 to the outer layer 2 is 1:1.5. The core layer 1 has a thickness of 5 μm. The core layer 1 is made of a toughened modified PET resin, and the outer layer 2 is made of an antistatic PET resin. The toughened modified PET resin comprises 100 kg of a first PET resin, 24.3 kg of a hydroxyl-terminated polyurethane resin prepared in [Preparation Example 1], 1.0 kg of a first hydroxyl-graphitized carbon nanotube, and 8.8 kg of a first bis-oxazoline chain extender. The antistatic PET resin comprises 100 kg of a second PET resin, 1.0 kg of a second hydroxyl-graphitized carbon nanotube, and 4.8 kg of a second bis-oxazoline chain extender.

[0061] In this embodiment, the first PET resin and the second PET resin are both made of American DuPont PT2251; the first hydroxyl graphitized carbon nanotube and the second hydroxyl graphitized carbon nanotube are both made of hydroxyl graphitized carbon nanotube CNT224 produced by China Science and Technology Research Institute, and the tube diameter of the hydroxyl graphitized carbon nanotube CNT224 is 10-20nm and the length is 10-30μm; the first bisoxazoline chain extender and the second bisoxazoline chain extender are both made of disoxizoline.

[0062] In this embodiment, the preparation method of the composite antistatic film includes the following steps:

[0063] The first PET resin, the hydroxyl-terminated polyurethane resin, the first hydroxyl-graphitized carbon nanotubes and the first bisoxazoline chain extender are mixed, melt-extruded at 245° C., and pelletized to obtain a toughened modified PET resin;

[0064] The second PET resin, the second hydroxy graphitized carbon nanotubes and the second bisoxazoline chain extender are mixed, melt-extruded at 245° C., and pelletized to obtain an antistatic PET resin;

[0065] The toughened modified PET resin was fed into extruder A, and the temperature of extruder A was set at 265°C;

[0066] The antistatic PET resin was fed into the extruder B, and the temperature of the extruder B was set to 265°C;

[0067] Connect the die distributor to extruders A and B. The melt from extruder B is evenly distributed to the upper and lower flow channels through the die distributor, and the melt from extruder A is distributed to the middle flow channel through the die distributor. The fluids in the three flow channels are co-extruded from the die lip and cast to obtain a cast sheet.

[0068] The cast sheet was stretched, and the transverse stretching ratio and the longitudinal stretching ratio were both 3 times to obtain a composite antistatic film.

[0069] [Example 2]

[0070] A composite antistatic film, referring to Figure 1 The invention relates to a composite material comprising a core layer 1 and an outer layer 2 composited onto the upper and lower surfaces of the core layer 1. The thickness ratio of the core layer 1 to the outer layer 2 is 1:1.5. The core layer 1 has a thickness of 5 μm. The core layer 1 is made of a toughened modified PET resin, and the outer layer 2 is made of an antistatic PET resin. The toughened modified PET resin comprises 100 kg of a first PET resin, 30.8 kg of a hydroxyl-terminated polyurethane resin prepared in [Preparation Example 2], 1.5 kg of a first hydroxyl-graphitized carbon nanotube, and 10.4 kg of a first bisoxazoline chain extender. The antistatic PET resin comprises 100 kg of a second PET resin, 0.85 kg of a second hydroxyl-graphitized carbon nanotube, and 3.5 kg of a second bisoxazoline chain extender.

[0071] In this embodiment, the first PET resin and the second PET resin are both made of Korean SK BR8040; the first hydroxyl graphitized carbon nanotube and the second hydroxyl graphitized carbon nanotube are both made of hydroxyl graphitized carbon nanotube CNT225 produced by China Science and Technology Research Institute, and the diameter of the hydroxyl graphitized carbon nanotube CNT225 is 20-30 nm and the length is 10-30 μm; the first bis-oxazoline chain extender and the second bis-oxazoline chain extender are both made of 2,2'-(1,3-phenylene)-bis-oxazoline.

[0072] In this embodiment, the preparation method of the composite antistatic film includes the following steps:

[0073] The first PET resin, the hydroxyl-terminated polyurethane resin, the first hydroxyl-graphitized carbon nanotubes and the first bisoxazoline chain extender are mixed, melt-extruded at 260° C., and pelletized to obtain a toughened modified PET resin;

[0074] The second PET resin, the second hydroxy graphitized carbon nanotubes and the second bisoxazoline chain extender are mixed, melt-extruded at 260° C., and pelletized to obtain an antistatic PET resin;

[0075] The toughened modified PET resin was fed into extruder A, and the temperature of extruder A was set at 280°C;

[0076] The antistatic PET resin was fed into the extruder B, and the temperature of the extruder B was set to 280°C;

[0077] Connect the die distributor to extruders A and B. The melt from extruder B is evenly distributed to the upper and lower flow channels through the die distributor, and the melt from extruder A is distributed to the middle flow channel through the die distributor. The fluids in the three flow channels are co-extruded from the die lip and cast to obtain a cast sheet.

[0078] The cast sheet was stretched, and the transverse stretching ratio and the longitudinal stretching ratio were both 3 times to obtain a composite antistatic film.

[0079] [Example 3]

[0080] A composite antistatic film, which differs from [Example 1] in that the hydroxyl-terminated polyurethane resin is replaced by an equal amount of the hydroxyl-terminated polyurethane resin prepared in [Preparation Example 3].

[0081] [Example 4]

[0082] A composite antistatic film, which differs from [Example 1] in that the hydroxyl-terminated polyurethane resin is replaced by an equal amount of the hydroxyl-terminated polyurethane resin prepared in [Preparation Example 4].

[0083] Comparative Example

[0084] [Comparative Example 1]

[0085] A composite antistatic film, which differs from [Example 1] in that:

[0086] In the toughened modified PET resin, the hydroxyl-terminated polyurethane resin is replaced by an equal amount of the first PET resin.

[0087] [Comparative Example 2]

[0088] A composite antistatic film, which differs from [Example 1] in that:

[0089] In the toughened modified PET resin, the hydroxyl-terminated polyurethane resin is replaced by an equal amount of styrene-butadiene thermoplastic elastomer T171.

[0090] [Comparative Example 3]

[0091] A composite antistatic film, which differs from [Example 1] in that:

[0092] In the toughened modified PET resin, the first bisoxazoline chain extender is replaced by an equal amount of diphenylmethane diisocyanate, and in the antistatic PET resin, the second bisoxazoline chain extender is replaced by an equal amount of diphenylmethane diisocyanate.

[0093] [Comparative Example 4]

[0094] A composite antistatic film, which differs from [Example 1] in that:

[0095] In the toughened modified PET resin, the first bisoxazoline chain extender is replaced by an equal amount of the first PET resin, and in the antistatic PET resin, the second bisoxazoline chain extender is replaced by an equal amount of the second PET resin.

[0096] Performance testing

[0097] 1. Elongation at Break: Referring to GB / T 13022-1991 "Test Method for Tensile Properties of Plastic Films", the composite antistatic films prepared in each example and comparative example of this application were made into standard test specimens. The composite antistatic films in each example and comparative example were tested for elongation at break according to the standard. The test speed was 100 mm / min, and the elongation at break of the composite antistatic films in each example and comparative example was recorded.

[0098] 2. Stability: Take 10 rolls of the composite antistatic film in each example and comparative example (all without interlayer blistering problems), store them under the same environmental conditions for 180 days, observe whether blistering occurs between the layers of the composite antistatic film, and record the number of rolls of the composite antistatic film with interlayer blistering.

[0099] 3. Surface resistance: The surface resistance of the composite antistatic films prepared in the examples and comparative examples of this application was measured with reference to GB / T 33398-2016 "Measurement method for surface resistance of optically functional polyethylene terephthalate (PET) films".

[0100] Table 1

[0101] Sample Elongation at break / % Number of foam rolls / roll Surface resistance / Ω Example 1 58.6 0 <![CDATA[2.5*10 6 ]]> Example 2 54.9 0 <![CDATA[2.9*10 6 ]]> Example 3 56.8 4 <![CDATA[2.7*10 6 ]]> Example 4 49.5 2 <![CDATA[2.8*10 6 ]]> Comparative Example 1 22.8 0 <![CDATA[2.7*10 6 ]]> Comparative Example 2 28.9 0 <![CDATA[2.6*10 6 ]]> Comparative Example 3 39.9 0 <![CDATA[2.9*10 6 ]]> Comparative Example 4 32.1 0 <![CDATA[4.3*10 7 ]]>

[0102] Comparative Example 1 differs from Example 1 in that the hydroxyl-terminated polyurethane resin in Comparative Example 1 is replaced with an equal amount of the first PET resin. The data in Table 1 show that replacing the hydroxyl-terminated polyurethane resin with the first PET resin significantly reduces the elongation at break of the composite antistatic film, hindering the efficiency of composite antistatic film formation.

[0103] Comparative Example 2 differs from Example 1 in that the hydroxyl-terminated polyurethane resin in Comparative Example 2 is replaced with an equal amount of styrene-butadiene thermoplastic elastomer. Combined with the data in Table 1, it can be seen that replacing the hydroxyl-terminated polyurethane resin with styrene-butadiene thermoplastic elastomer significantly reduces the elongation at break of the composite antistatic film, which is not conducive to improving the molding efficiency of the composite antistatic film.

[0104] Comparative Example 3 differs from Example 1 in that the first and second bisoxazoline chain extenders in Comparative Example 3 are each replaced with an equal amount of diphenylmethane diisocyanate. Combining the data in Table 1, it can be seen that after the bisoxazoline chain extender is replaced with diphenylmethane diisocyanate, the elongation at break of the composite antistatic film decreases somewhat, but is superior to the composite antistatic film in Comparative Example 2.

[0105] Comparative Example 4 differs from Example 1 in that no bisoxazoline chain extender is added to the toughened and modified PET resin or the antistatic PET resin in Comparative Example 4. Combined with the data in Table 1, it can be seen that without the addition of a bisoxazoline chain extender, the elongation at break of the composite antistatic film decreases, and the surface resistance of the composite antistatic film tends to increase, weakening the antistatic performance.

[0106] The difference between Example 3 and Example 1 is that in Example 3, no bi-terminal hydroxypropyl silicone oil was added during the synthesis of the hydroxyl-terminated polyurethane resin. Combined with the data in Table 1, it can be seen that without the addition of bi-terminal hydroxypropyl silicone oil during the synthesis of the hydroxyl-terminated polyurethane resin, some composite antistatic films were prone to localized blistering between layers after long-term storage. This is due to the increased melt viscosity of the toughened modified PET resin, which prevented bubbles from being promptly expelled from the melt, or localized uneven extrusion during the melt extrusion process, resulting in blistering and delamination of the composite antistatic film in the later stages.

[0107] The difference between Example 4 and Example 1 is that propylene glycol was not added during the synthesis of the hydroxyl-terminated polyurethane resin in Example 4. Combined with the data in Table 1, it can be seen that without the addition of propylene glycol during the synthesis of the hydroxyl-terminated polyurethane resin, the toughness of the composite antistatic film decreased, and some composite antistatic films also experienced blistering and delamination in the later stages.

[0108] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A composite antistatic film, characterized in that: The invention comprises a core layer (1) and an outer layer (2) compounded on the upper and lower surfaces of the core layer (1), wherein the core layer (1) is made of a toughened modified PET resin, and the outer layer (2) is made of an antistatic PET resin; wherein, based on the raw materials, the toughened modified PET resin comprises 100 parts by weight of a first PET resin, 24.3-30.8 parts by weight of a hydroxyl-terminated polyurethane resin, 1.0-1.5 parts by weight of a first hydroxyl graphitized carbon nanotube, and 8.8-10.4 parts by weight of a first bis-oxazoline chain extender; and the antistatic PET resin comprises 100 parts by weight of a second PET resin, 0.85-1.0 parts by weight of a second hydroxyl graphitized carbon nanotube, and 3.5-4.8 parts by weight of a second bis-oxazoline chain extender. Based on the raw materials, the hydroxyl-terminated polyurethane resin includes 58-64 parts by weight of isocyanate-terminated polyurethane prepolymer, 5.5-6.0 parts by weight of small molecule diol chain extender and 8.5-10.8 parts by weight of double-terminated hydroxypropyl silicone oil; the isocyanate-terminated polyurethane prepolymer is prepared from 30-40 parts by weight of polyester diol, 12.8-16.4 parts by weight of diisocyanate and 0.01-0.015 parts by weight of catalyst.

2. The composite antistatic film according to claim 1, characterized in that: The first PET resin and the second PET resin are made of American DuPont PT2251 or Korean SK BR8040.

3. The composite antistatic film according to claim 1, characterized in that: The small molecule diol chain extender is at least one of propylene glycol, 1,4-butanediol and neopentyl glycol.

4. The composite antistatic film according to claim 1, characterized in that: The molecular weight of the polyester diol is 1000-2000.

5. A composite antistatic film according to any one of claims 1 to 4, characterized in that: The preparation method of the terminal hydroxyl polyurethane resin includes the following steps: heating the polyester diol to 45-55°C, then adding diisocyanate and a catalyst, heating to 70-75°C under nitrogen protection and reacting for 3-4 hours to obtain an isocyanate-terminated polyurethane prepolymer; adding a small molecule diol chain extender and a double-terminated hydroxypropyl silicone oil to the isocyanate-terminated polyurethane prepolymer, continuing the reaction at 80-85°C for 3-4 hours, and then vacuuming, cooling, and granulating to obtain the terminal hydroxyl polyurethane resin.

6. The composite antistatic film according to claim 1, characterized in that: The diameter of the first hydroxy graphitized carbon nanotube and the second hydroxy graphitized carbon nanotube is 10-30 nm, and the length is 10-30 μm.

7. The composite antistatic film according to claim 1, characterized in that: The first bisoxazoline chain extender and the second bisoxazoline chain extender are 2,2'-(1,3-phenylene)-bisoxazoline.

8. The composite antistatic film according to claim 1, characterized in that: The thickness ratio of the core layer (1) to the outer layer (2) is 1:(1-1.5).

9. The method for preparing a composite antistatic film according to any one of claims 1 to 8, characterized in that: The following steps are involved: The first PET resin, the end-hydroxyl polyurethane resin, the first hydroxyl graphitized carbon nanotubes and the first bisoxazoline chain extender are mixed, melt-extruded and granulated at 245-260°C to obtain a toughened modified PET resin; the second PET resin, the second hydroxyl graphitized carbon nanotubes and the second bisoxazoline chain extender are mixed, melt-extruded and granulated at 245-260°C to obtain an antistatic PET resin; the toughened modified PET resin is fed into extruder A, and the temperature of extruder A is set to 265-280°C; the antistatic PET resin is fed into extruder B, and the temperature of extruder B is set to 265-280°C; a die distributor is connected to extruders A and B, wherein the melt of extruder B is evenly distributed to the upper and lower flow channels through the die distributor, and the melt of extruder A is distributed to the middle flow channel through the die distributor, and the fluids in the three flow channels are co-extruded and cast from the die lip to obtain a cast sheet; the cast sheet is stretched to obtain a composite antistatic film.

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