Lasting hydrophobic automobile paint surface protective film and preparation method thereof

Abstract

The invention discloses a durable hydrophobic automobile paint surface protective film and a preparation method thereof, and belongs to the technical field of protective films. The technical problem that the environmental protection standard cannot be met due to the fact that fluorine atoms are introduced into an existing hydrophobic coating and the use amount of a solvent is increased is solved. According to the technical scheme, the preparation method comprises the following steps: preparing a fluorine-containing polyurethane elastomer base film containing a fluorocarbon side chain, performing corona treatment on one surface of the fluorine-containing polyurethane elastomer base film, then coating an acrylate coating to obtain an acrylate coating, and compounding the other surface of the fluorine-containing polyurethane elastomer base film with a pressure-sensitive adhesive layer to obtain the durable hydrophobic automobile paint surface protective film. The automobile paint protective film has the beneficial effects that the intermolecular force is weakened at high temperature, the fluorocarbon side chain of the base film is driven by surface free energy to migrate to the surface of the coating, the hydrophobic effect of the surface of the automobile paint protective film is achieved, and the fluorocarbon side chain is limited by the base film, so that the durability of the hydrophobic performance is good.

Description

Technical Field

[0001] The invention belongs to the technical field of protective films, and in particular relates to a durable hydrophobic automobile paint protective film and a preparation method thereof. Background Art

[0002] At present, automotive paint protection films mainly use elastomeric polyurethane as the base film, and form an acrylic coating on the surface of the base film through coating technology to further improve the surface properties of the automotive paint protection film, including wear resistance, weather resistance and hydrophobicity. The hydrophobicity of automotive paint protection films enables them to effectively prevent moisture from adhering to the surface, thereby reducing the generation of water spots and stains.

[0003] At present, the hydrophobicity of acrylate coatings is achieved by introducing nanofillers, such as silicon dioxide, carbon nanomaterials, nano metal oxides, etc., to increase the roughness of the coating surface. However, nanofillers are prone to agglomeration, the stability of the coating is poor, and there are problems with compatibility with the resin matrix, which affects the durability of the hydrophobic effect. Or acrylates are fluorinated. For example, patent CN 113072890A discloses a self-repairing anti-yellowing paint protective film and a preparation method thereof, wherein the self-repairing coating is coated and thermally cured by a functionalized polyurethane acrylate coating, and its composition includes a polyhydroxy fluorine-modified acrylate resin, and the coating is given hydrophobic properties by introducing a fluorine component, but the introduction of fluorine atoms increases the relative molecular mass of the coating, resulting in an increase in viscosity, and then a large amount of solvent is required for dilution, which increases the volatile organic compound (VOC) content in the coating and cannot meet increasingly stringent environmental standards. Summary of the invention

[0004] In view of the technical problem that the introduction of fluorine atoms into existing hydrophobic coatings increases the amount of solvent used, resulting in the inability to meet environmental protection standards, the purpose of the present invention is to provide a method for preparing a durable hydrophobic automobile paint protection film, by weakening the intermolecular force at high temperature, the fluorocarbon side chains of the base film migrate to the surface of the coating driven by the surface free energy, so that the surface of the automobile paint protection film exerts a hydrophobic effect, and the fluorocarbon side chains are also restricted by the base film to ensure that the hydrophobic performance is durable.

[0005] To achieve the above purpose, the present invention adopts the following technical scheme: a method for preparing a durable hydrophobic automobile paint protective film, comprising the following steps:

[0006] (1) mixing polycaprolactone polyol, isophorone diisocyanate and a catalyst to obtain a polyurethane prepolymer; adding a combined chain extender to the polyurethane prepolymer, mixing and aging to obtain a fluorine-containing polyurethane prepolymer; extruding and granulating the fluorine-containing polyurethane prepolymer to obtain particles; then casting and extruding the particles to form a film, and laminating one side of the film with a PET substrate film to obtain a fluorine-containing polyurethane elastomer base film;

[0007] (2) subjecting the side of the fluorinated polyurethane elastomer base film obtained in step (1) without the PET substrate film to a corona treatment to obtain a corona surface of the fluorinated polyurethane elastomer base film;

[0008] (3) applying an acrylic coating to the corona surface of the fluorinated polyurethane elastomer base film obtained in step (2), followed by curing to obtain an acrylic coating, and compounding an optical grade PET protective film on the coating to obtain a semi-finished product;

[0009] (4) coating an acrylic pressure-sensitive adhesive on a PET release film, drying the pressure-sensitive adhesive layer, and compounding the pressure-sensitive adhesive layer with one side of the semi-finished PET substrate film obtained in step (3), and aging the resultant to obtain a durable hydrophobic automotive paint protection film.

[0010] Furthermore, in step (1), the combined chain extender includes a chain extender containing a fluorocarbon side chain and a chain extender not containing a fluorocarbon side chain.

[0011] Furthermore, in step (1), the raw materials of the chain extender containing fluorine-carbon side chains include isophorone diisocyanate, monofluoroalcohol and trimethylolpropane.

[0012] Furthermore, the monohydric fluoroalcohol is hexafluoroisopropanol, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol or perfluorohexylethyl alcohol.

[0013] Furthermore, in step (1), the chain extender containing no fluorocarbon side chain is 1,4-butanediol, ethylene glycol, 1,3-propylene glycol, 1,6-hexanediol or dimethylpropylene glycol.

[0014] Furthermore, in step (1), the mass ratio of the polycaprolactone polyol, isophorone diisocyanate, combined chain extender and catalyst is 45-55wt%: 20-40wt%: 12-25wt%: 0.01-0.1wt%.

[0015] Furthermore, in step (2), the power of the corona treatment is 1 to 2 kW.

[0016] Furthermore, in step (3), the acrylate coating is a polyurethane acrylate coating.

[0017] Furthermore, in step (3), the curing treatment is divided into two stages: the temperature of the first stage is 70°C to 90°C, and the time is 1 to 3 minutes; the temperature of the second stage is 110 to 125°C, and the time is 1 to 3 minutes.

[0018] A durable hydrophobic automobile paint protection film is prepared by the above method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The base film of the present invention is a fluorine-containing polyurethane elastomer base film, and its raw material composition includes polyol, isophorone diisocyanate and a combined chain extender, and the combined chain extender includes a chain extender containing a fluorine carbon side chain and a chain extender without a fluorine carbon side chain. The asymmetric molecular structure of isophorone diisocyanate makes the hydrogen bond formed between molecules weaker. At the same time, compared with the direct bonding of fluorine atoms with main chain carbon atoms, the surface aggregation performance of the chain extender containing a fluorine carbon side chain is large, and the fluidity of the fluorine carbon molecular chain is good;

[0021] (2) Fluorine has strong electronegativity and high CF bond energy in the structure. Fluorocarbon molecular chains with low surface energy are easy to migrate and accumulate on the surface of the membrane. In the present invention, the fluorine-containing polyurethane elastomer base membrane is melted and the intermolecular force is weakened through the segmented curing process of the acrylate coating. At the same time, the solvent in the acrylate coating evaporates to form micropores or gaps, and the solvent carries the fluorocarbon molecular chains to migrate more easily to the surface of the coating. The fluorocarbon molecular chains are regularly distributed on the surface and can exert hydrophobic properties on the surface of the coating. Then a curing reaction occurs. At the same time, since the fluorocarbon molecular chains are also restricted by the base membrane, the durability of the hydrophobic property can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Among them, 1. Fluorinated polyurethane elastomer base film; 2. Acrylate coating; 3. Optical grade PET protective film; 4. Pressure-sensitive adhesive layer; 5. PET release film. DETAILED DESCRIPTION

[0024] In order to express the technical mode implemented by the present invention clearly, accurately and completely, the present invention will be further described below in conjunction with embodiments and drawings.

[0025] The present invention utilizes that the acrylate coating needs high temperature for curing treatment. High temperature can increase the heat energy in the molecule, making the interaction between the molecules unstable and the hydrogen bond easily destroyed. Moreover, due to the strong electronegativity of fluorine and the high CF bond energy in the structure, the fluorine carbon side chain migrates to the surface of the coating under the driving of the surface free energy, so that the surface of the automobile paint protection film plays a hydrophobic role. In order to avoid reducing the bonding effect between the acrylate coating and the fluorine-containing polyurethane elastomer base film, a corona treatment is performed on one side of the fluorine-containing polyurethane elastomer base film to make its surface rough. During the corona treatment process, chemical bonds such as methyl and methylene on the surface of the fluorine-containing polyurethane elastomer base film are broken, generating active groups such as hydroxyl and carboxyl, thereby enhancing its bonding effect with the polyester polyurethane acrylate coating.

[0026] The raw materials and equipment in the following examples and comparative examples are all commercially available.

[0027] Example 1

[0028] The durable hydrophobic automobile paint protection film of this embodiment is prepared by the following steps:

[0029] (1) Polycaprolactone polyol (BASF PCL2000), isophorone diisocyanate (Covestro Desmodur I) and an organic tin catalyst (DBTDL-T12) were mixed and reacted at 80°C for 4 hours to obtain a polyurethane prepolymer; a combined chain extender was added to the polyurethane prepolymer and mixed, and then aged at 100°C for 12 hours to obtain a fluorinated polyurethane prepolymer; the fluorinated polyurethane prepolymer was crushed and then extruded to obtain granules; and the granules were Casting extrusion is performed to form a film, and one side of the film is attached to a PET substrate film for winding to obtain a fluorinated polyurethane elastomer base film; wherein the raw material composition is as follows: 52.40wt% of polycaprolactone polyol, 25.61wt% of isophorone diisocyanate, 21.97wt% of a combined chain extender, and 0.02wt% of an organic tin catalyst; the combined chain extender is composed of a chain extender containing a fluorinated carbon side chain and butanediol, and the molar ratio of the chain extender containing a fluorinated carbon side chain to butanediol is 1:2.2;

[0030] (2) subjecting the side of the fluorinated polyurethane elastomer base film obtained in step (1) without the PET substrate film to a corona treatment to obtain a corona surface of the fluorinated polyurethane elastomer base film; wherein the power of the corona treatment machine is 1 kW and the speed is 6 m / min;

[0031] (3) a main agent polyurethane acrylate (solid content 35%), an aliphatic polyisocyanate curing agent (solid content 90%) and a diluent ethyl acetate are mixed in a mass ratio of 2:1:4, and a leveling agent (SY-9733) is added in an amount of 0.5% of the sum of the mass of the main agent, the curing agent and the diluent to obtain a polyurethane acrylate coating; the polyurethane acrylate coating is coated on the corona surface of the fluorine-containing polyurethane elastomer base film obtained in step (2) by a micro-concave roller, and a polyurethane acrylate coating is obtained by curing the coating, and a layer of optical grade PET protective film is compounded on the coating to obtain a semi-finished product; the curing treatment is divided into two stages, the temperature of the first stage is 70-90° C., and the time is 1.8 min; the temperature of the second stage is 110-120° C., and the time is 1.8 min;

[0032] (4) using a comma blade coating method to coat the acrylic pressure-sensitive adhesive on the PET release film, drying at 100° C. to obtain a pressure-sensitive adhesive layer, compounding it with one side of the semi-finished PET substrate film obtained in step (3), and aging at 45° C. for 72 hours to obtain a durable hydrophobic paint protection film; wherein the thickness of the adhesive layer is 35 μm.

[0033] In step (1), the raw materials of the fluorine-containing carbon side chain chain extender include isophorone diisocyanate, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, and trimethylolpropane; the preparation of the fluorine-containing carbon side chain chain extender includes the following steps: adding isophorone diisocyanate, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, and ethyl acetate to a catalyst for reaction; then adding trimethylolpropane dropwise for reaction to obtain; the structural formula of the fluorine-containing carbon side chain chain extender of this embodiment is:

[0034]

[0035] The structure of the durable hydrophobic paint protection film of this embodiment is as follows Figure 1 As shown, an acrylate coating 2 and a pressure-sensitive adhesive layer 4 are provided on both sides of the fluorinated polyurethane elastomer base film 1, an optical-grade PET protective film 3 is provided on one side of the acrylate coating 2, and a PET release film 5 is provided on one side of the pressure-sensitive adhesive layer 4. When in use, the PET release film 5 and the optical-grade PET protective film 3 are torn off, and the pressure-sensitive adhesive layer 4 is bonded to the car paint surface.

[0036] Example 2

[0037] The durable hydrophobic automobile paint protection film of this embodiment is prepared by the following steps:

[0038] (1) Polycaprolactone polyol (BASF PCL1000), isophorone diisocyanate (Covestro Desmodur I) and an organic tin catalyst (DBTDL-T12) were mixed and reacted at 90°C for 3 hours to obtain a polyurethane prepolymer; a combined chain extender was added to the polyurethane prepolymer and mixed, and then aged at 100°C for 12 hours to obtain a fluorinated polyurethane prepolymer; the fluorinated polyurethane prepolymer was crushed and then extruded to obtain granules; and the granules were then The pellets are cast and extruded into a film, and one side of the film is attached to a PET substrate film for winding to obtain a fluorinated polyurethane elastomer base film; wherein the raw material composition is as follows: 48.22wt% of polycaprolactone polyol, 27.32wt% of isophorone diisocyanate, 24.44wt% of a combined chain extender, and 0.02wt% of an organic tin catalyst; the combined chain extender is composed of a chain extender containing a fluorinated carbon side chain and butanediol, and the molar ratio of the chain extender containing a fluorinated carbon side chain to butanediol is 1:1;

[0039] (2) subjecting the side of the fluorinated polyurethane elastomer base film obtained in step (1) without the PET substrate film to a corona treatment to obtain a corona surface of the fluorinated polyurethane elastomer base film; wherein the power of the corona treatment machine is 2 kW and the speed is 6 m / min;

[0040] (3) a main agent polyurethane acrylate (solid content 35%), an aliphatic polyisocyanate curing agent (solid content 90%) and a diluent ethyl acetate are mixed in a mass ratio of 2:1:4, and a leveling agent (SY-9733) is added in an amount of 0.5% of the sum of the mass of the main agent, the curing agent and the diluent to obtain a polyurethane acrylate coating; the polyurethane acrylate coating is coated on the corona surface of the fluorine-containing polyurethane elastomer base film obtained in step (2) by a micro-concave roller, and a polyurethane acrylate coating is obtained by curing the coating, and a layer of optical grade PET protective film is compounded on the coating to obtain a semi-finished product; the curing treatment is divided into two stages, the temperature of the first stage is 70-90° C., and the time is 1.8 min; the temperature of the second stage is 110-120° C., and the time is 1.8 min;

[0041] (4) coating the acrylate pressure-sensitive adhesive on the PET release film by a slit coating method, drying at 100° C. to obtain a pressure-sensitive adhesive layer, compounding the pressure-sensitive adhesive layer with one side of the semi-finished PET substrate film obtained in step (3), and aging at 45° C. for 72 h to obtain a durable hydrophobic paint protection film; wherein the thickness of the adhesive layer is 35 μm.

[0042] In step (1), the raw materials of the fluorine-containing carbon side chain chain extender include isophorone diisocyanate, hexafluoroisopropanol, and trimethylolpropane; the preparation of the fluorine-containing carbon side chain chain extender includes the following steps: adding isophorone diisocyanate, hexafluoroisopropanol, and ethyl acetate to a catalyst for reaction; then adding trimethylolpropane dropwise for reaction to obtain; the structural formula of the fluorine-containing carbon side chain chain extender of this embodiment is:

[0043]

[0044] Comparative Example 1

[0045] The same as Example 1, except that isophorone diisocyanate is replaced by 4,4'-dicyclohexyl diisocyanate.

[0046] Comparative Example 2

[0047] The same as Example 1, except that the chain extender containing fluorine-carbon side chains is changed to 1H,1H,9H,9H-perfluoro-1,9-nonanediol.

[0048] Comparative Example 3

[0049] The same as Example 1, except that the temperature of the first stage is 70-90° C. and the time is 1.2 min.

[0050] Comparative Example 4

[0051] The method is the same as Example 1, except that step (1) does not contain a chain extender containing a fluorine-containing carbon side chain, and a hydrophobic agent is added to the polyurethane acrylate coating in step (3), the hydrophobic agent is a fluorine-containing block polymer solution, and the amount of the hydrophobic agent is 1% of the mass of the main polyurethane acrylate.

[0052] The present invention tests the surface water contact angle of Examples 1 to 2 and Comparative Examples 1 to 4 before and after aging. The surface water contact angle test of the present invention is in accordance with the standard of GB / T 30693-2014 "Measurement of the Contact Angle of Water on Plastic Film", and the aging method is to place the film under light 1000kW, temperature 60°C and humidity 70% for 3 hours. The results are shown in Table 1.

[0053] Table 1 Surface water contact angle results of Examples 1 to 2 and Comparative Examples 1 to 4

[0054] Surface water contact angle Hydrophobic persistence Example 1 95.7° 92.2° Example 2 95.1° 91.3° Comparative Example 1 89.3° — Comparative Example 2 87.6° — Comparative Example 3 90.5° — Comparative Example 4 100.2° 82.5°

[0055] As can be seen from Table 1, the water contact angle of Comparative Example 1 is lower than that of Example 1, which may be due to the fact that the polyisocyanate is 4,4'-dicyclohexyl diisocyanate, which has good symmetry of molecular structure, regular molecular chain, easy alignment to form hydrogen bonds, strong intermolecular force, but also reduces the mobility of fluorocarbon chain. The molecular structure of Example 1 is more conducive to the migration of fluorocarbon molecular chain to its surface during the segmented curing process of acrylate coating. The polyisocyanate of Example 1 is isophorone diisocyanate, whose molecule lacks symmetry, one NCO group in the molecule is connected to the cyclohexane ring, and the other is connected to the methyl side chain. At the same time, it is affected by the steric hindrance of the cyclohexane ring and the substituted methyl group. The two NCO groups have different positions and activities, and the hard segments formed are irregularly arranged. The strength of hydrogen bonds formed between molecules is also weak, which is conducive to the flow of fluorocarbon molecular chains.

[0056] The water contact angle of Comparative Example 2 is lower than that of Example 1. This is because the fluorocarbon chain is on the main chain, and the migration of the entire fluorocarbon chain is constrained by the main chain, and the migration to the coating surface is insufficient, resulting in insufficient improvement of the hydrophobic effect. When the fluorocarbon chain of Example 1 is connected to the main chain in the form of a side chain, the movement of the other end of the fluorocarbon chain is not affected by the main chain, and the fluorine atoms can migrate to the coating surface, thereby reducing the surface energy of the coating and improving the hydrophobic effect.

[0057] The acrylate coating of Comparative Example 3 has a shorter solvent volatilization time at 70-90°C, and the curing reaction occurs earlier, which affects the migration of the fluorocarbon molecular chains and may be unevenly distributed on the surface. Example 1 prolongs the time of the first stage of the curing treatment of the acrylate coating, which is conducive to the migration and uniform arrangement of the fluorocarbon molecular chains.

[0058] In Comparative Example 4, a hydrophobic agent is added to the coating. The aging process causes chain scission, thermal oxidation and hydrolysis reactions in the acrylate coating. The hydrophobic performance decreases significantly after aging, indicating that the hydrophobic effect is not durable. The fluorocarbon chains in Example 1 are fixed by the base film, and the hydrophobic effect does not decrease significantly.

Claims

1. A method for preparing a durable hydrophobic automobile paint protective film, characterized in that: The steps include: (1) mixing polycaprolactone polyol, isophorone diisocyanate and a catalyst to obtain a polyurethane prepolymer; adding a combined chain extender to the polyurethane prepolymer, mixing and aging to obtain a fluorine-containing polyurethane prepolymer; extruding and granulating the fluorine-containing polyurethane prepolymer to obtain particles; then casting and extruding the particles to form a film, and laminating one side of the film with a PET substrate film to obtain a fluorine-containing polyurethane elastomer base film; (2) subjecting the side of the fluorinated polyurethane elastomer base film obtained in step (1) without the PET substrate film to a corona treatment to obtain a corona surface of the fluorinated polyurethane elastomer base film; (3) applying an acrylic coating to the corona surface of the fluorinated polyurethane elastomer base film obtained in step (2), followed by curing to obtain an acrylic coating, and compounding an optical grade PET protective film on the coating to obtain a semi-finished product; (4) coating an acrylic pressure-sensitive adhesive on a PET release film, drying the pressure-sensitive adhesive layer, and compounding the pressure-sensitive adhesive layer with one side of the semi-finished PET substrate film obtained in step (3), and aging the resultant to obtain a durable hydrophobic automotive paint protection film.

2. The preparation method according to claim 1, characterized in that: In step (1), the combined chain extender includes a chain extender containing a fluorocarbon side chain and a chain extender not containing a fluorocarbon side chain.

3. The preparation method according to claim 2, characterized in that: In step (1), the raw materials of the chain extender containing fluorine-carbon side chains include isophorone diisocyanate, monofluoroalcohol and trimethylolpropane.

4. The preparation method according to claim 3, characterized in that: The monovalent fluoroalcohol is hexafluoroisopropanol, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol or perfluorohexylethyl alcohol.

5. The preparation method according to claim 2, characterized in that: In step (1), the chain extender containing no fluorocarbon side chain is 1,4-butanediol, ethylene glycol, 1,3-propylene glycol, 1,6-hexanediol or dimethyl propanediol.

6. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the polycaprolactone polyol, isophorone diisocyanate, combined chain extender and catalyst is 45-55wt%: 20-40wt%: 12-25wt%: 0.01-0.1wt%.

7. The preparation method according to claim 1, characterized in that: In step (2), the power of the corona treatment is 1 to 2 kW.

8. The preparation method according to claim 1, characterized in that: In step (3), the acrylate coating is a polyurethane acrylate coating.

9. The preparation method according to claim 1, characterized in that: In step (3), the curing treatment is divided into two stages: the temperature of the first stage is 70°C to 90°C, and the time is 1 to 3 minutes; the temperature of the second stage is 110 to 125°C, and the time is 1 to 3 minutes.

10. A durable hydrophobic automobile paint protection film, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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