Heat-insulating polyurethane multilayer film and preparation method therefor

Abstract

Disclosed in the present invention are a heat-insulating polyurethane multilayer film and a preparation method therefor. The preparation method comprises the following steps: uniformly mixing a polyester polyol and a polylactic acid polyol, then adding polyisocyanate, and heating and stirring the mixture to react to obtain a precursor; adding a chain extender and stirring the mixture to react to obtain a polyurethane elastomer solution; coating a PET release film with the polyurethane elastomer solution, and drying to obtain a first TPU base film and a second TPU base film; coating a surface of the first TPU base film with a coating layer containing a heat-insulating nanomaterial and then covering with the second TPU base film, followed by curing; forming a heat-insulating layer in the middle layer between the two base films; and peeling off the release film from the second TPU base film, coating the second TPU base film with a self-repairing protective coating layer, peeling off the release film from the first TPU base film, and coating a back surface of the first TPU base film with a pressure-sensitive adhesive layer, followed by baking and drying. The multilayer composite film obtained by the present invention has high transparency, and a good self-repairing function is realized by utilizing a polyurethane elastomer.

Description

Thermal insulation polyurethane multilayer film and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the field of film preparation, in particular to a thermal insulation polyurethane multilayer film and a preparation method thereof. BACKGROUND

[0002] At present, the TPU (polyurethane elastomer) car protection film sold on the market is mainly used for the surface of car paint. It has excellent mechanical properties and durability, and can further improve the appearance of car paint and even the car while protecting the car paint from the damage of the external environment.

[0003] At present, the commonly used film main body of the car glass film sold on the market is optical grade hard PET (polyethylene terephthalate), which has excellent optical performance and low haze and does not affect the line of sight. In use, unlike the TPU car paint protection film, the PET film is attached to the inner side of the glass (i.e. the side facing the interior of the car). One disadvantage of the inner attachment is that the VOC (volatile organic compounds) formed in the production process of the PET window film product formula, such as the residual solvent and monomers in the pressure-sensitive adhesive, can easily stay in the car interior for a long time, causing pollution in the car interior. If it can be changed to outer attachment, this problem can be avoided. However, the PET film itself has poor resistance to ultraviolet aging and hydrolysis, so even if it is attached outside, it cannot be used for a long time. At the same time, the PET film does not have the ability to resist external mechanical damage (such as scratching), which further limits the possibility of PET outer attachment. The TPU (polyurethane elastomer) film has thermal repairability and excellent weather resistance, which can avoid the problem of poor durability caused by the use of PET film. However, the biggest problem of the TPU (polyurethane elastomer) protection film when attached to the car glass is poor transparency, mainly reflected in high transmission haze, which will affect the line of sight of the person inside the car. Especially when it is used on the surface of the front glass, since the front glass has a certain angle with the line of sight of the driver, the defect of high transmission haze will be magnified in the case of poor night vision, which seriously affects the actual application of the product. Therefore, a film with low transmission haze, excellent repair performance and good outdoor durability is needed to replace the existing PET film and TPU film, so as to realize the application of the outer attachment of the car glass film. SUMMARY

[0004] The present application relates to a thermal insulation polyurethane multilayer film and a preparation method thereof.

[0005] The multilayer film prepared by the solution method has high transparency, and the use of polyurethane elastomer realizes good self-repairing function, and the addition of the thermal insulation material layer makes the film have good thermal insulation effect.

[0006] After research, the inventors found that TPU film prepared by solution method can replace PET as the window film matrix and can achieve the optical properties of PET while having repair and impact resistance functions.

[0007] A method for preparing a heat-insulating polyurethane multilayer film comprises the following steps:

[0008] (1) Under an inert atmosphere, citric acid and polyethylene glycol 600 are mixed evenly, heated and stirred, an acidic catalyst is added, and the reaction is stirred until the weight of the system does not change to obtain a polyester polyol;

[0009] (2) In a solvent, under the action of a catalyst, polyester polyol and polylactic acid polyol are mixed evenly, and then polyisocyanate is added, and heated and stirred to react to obtain a prepolymer;

[0010] (3) adding a chain extender and stirring the reaction to obtain a polyurethane elastomer solution;

[0011] (4) coating the polyurethane elastomer solution on the PET release film, and drying to obtain a first TPU base film and a second TPU base film;

[0012] (5) coating the surface of the first TPU base film with a coating containing a heat-insulating nanomaterial, then covering it with a second TPU base film, and curing it to form a heat-insulating layer between the two base films;

[0013] (6) peeling off the release film of the second TPU base film and coating the self-repairing protective coating on the second base film;

[0014] (7) Peel off the release film of the first TPU base film and apply a pressure-sensitive adhesive layer on the back of the first TPU base film, and bake and dry it.

[0015] Wherein, in step (1), the acidic catalyst is preferably one or more of p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid; and the solvent is preferably one or more of DMF, DMSO, THF, and methyl isobutyl ketone.

[0016] In step (1), the inert atmosphere is preferably a nitrogen atmosphere.

[0017] Wherein, in step (2), the catalyst is preferably dibutyltin dilaurate, an organic bismuth catalyst, an organic zinc catalyst, or a tertiary amine catalyst.

[0018] In step (2), the weight average molecular weight of the precursor is preferably 1,000 to 20,000.

[0019] In step (4), the polyurethane elastomer solution is preferably coated on the PET release film by roller coating, spraying or dipping.

[0020] The coating of the heat insulation nanomaterials is preferably a heat insulation coating in the art, and the formula preferably comprises the following components by weight: 20-25 parts of heat insulation material slurry, 72-83 parts of film forming material, and 0.5-0.6 parts of antioxidant. The heat insulation material slurry is preferably a dispersion liquid of lanthanum hexaboride, indium tin oxide, antimony tin oxide or cesium tungstate powder; when ultraviolet light curing is used, the film forming material comprises 50-55 parts of diluent, 20-25 parts of oligomer and 2-3 parts of initiator; the diluent is preferably 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA) or tripropylene glycol diacrylate (TPGDA); the oligomer is preferably polyurethane acrylate; and the initiator is preferably an Irgacure series initiator product of IGM Company; when baking heat curing is used, the film forming material is polyacrylate or polyurethane. The antioxidant is preferably a Tinuvin series antioxidant product of BASF Company.

[0021] The polyisocyanate is preferably selected from diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), methylene bis(4-cyclohexyl isocyanate) (HMDI) and mixtures thereof.

[0022] In step (3), the weight average molecular weight of the polyurethane elastomer is preferably 10,000-200,000.

[0023] The polylactic acid polyol is preferably HPB500 or HPB1000 purchased from Anhui Huaihai Biological Technology Co., Ltd.

[0024] The chain extender is preferably one or more selected from ethane-1,2-diol, propane-1,3-diol, butane-1,4-diol and hexane-1,6-diol, diethylene glycol and triethylene glycol.

[0025] In step (5), the curing is preferably baking curing or UV curing, and more preferably baking curing.

[0026] In step (6), the coating of the self-repairing protective coating can be performed by a method of a protective coating in the art, and preferably by the method of CN201710820811.X.

[0027] The application also provides a heat insulation polyurethane multilayer film prepared by the above preparation method.

[0028] The heat insulation polyurethane multilayer film comprises a pressure-sensitive adhesive layer, a first base film, a heat insulation nanomaterial layer, a second base film and a self-repairing protective coating, which are sequentially stacked and combined from bottom to top.

[0029] Preferably, the thickness of the pressure-sensitive adhesive layer is 5-50 microns, preferably 8-30 microns.

[0030] Preferably, the thickness of the first base film and the second base film is 5-300 microns, preferably 10-50 microns.

[0031] Preferably, the thickness of the heat-insulating nanomaterial layer is 1-30 microns, preferably 2-20 microns.

[0032] Preferably, the thickness of the self-repairing protective coating is 2-30 microns, preferably 5-15 microns.

[0033] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the present application.

[0034] The reagents and raw materials used in the present application are commercially available.

[0035] The present application has achieved the following positive progress: the composite multilayer film obtained by the present application has high transparency, and the use of polyurethane elastomer realizes good self-repairing function. In addition, the formation of a self-repairing protective coating on the surface of the base film better realizes the self-repairing function of the multilayer composite film. DETAILED DESCRIPTION

[0036] The present application will be further described by way of examples, but the present application is not limited to the examples. In the following examples, the experimental methods not specified in the examples are selected according to conventional methods and conditions, or according to the instructions of the goods.

[0037] Solvent resistance test method: 1 ml of xylene is sprayed on the surface of the material to be tested, and after 30 seconds, the material is wiped dry with a wiping paper. If there is no obvious change in the appearance of the material (such as swelling, deformation, coating peeling, etc.), it is considered that the solvent resistance test is qualified.

[0038] Self-repairing test method: after a copper wire brush is used to brush a scratch on the surface of the film, it is observed whether the scratch can disappear automatically within 1 hour or under the condition of a heat source (such as hot water pouring). If it can disappear, it is considered that the material has self-repairing function.

[0039] Gloss evaluation method: the flexible high polymer substrate coated with the self-repairing coating is adhered to a black metal plate, and the gloss of the material surface is observed from the front and side (45 degrees) respectively. If the surface is smooth and reflective, and the reflection is clear and sharp, it is considered that the gloss is good, otherwise it is considered that the gloss is poor.

[0040] Staining resistance evaluation method: make marks on the surface of the coating with a reliable 6881 black oil-based marker, and after 10 minutes, wipe off the marks directly with a lens cleaning paper or with a lens cleaning paper soaked with anhydrous alcohol, and observe the removal of the marks. If the marks can be completely removed without leaving any traces, the staining resistance is considered to be excellent. If the marks cannot be removed, the staining resistance is considered to be poor. If the marks can be removed but leave a small amount of traces, the staining resistance is considered to be good.

[0041] Elongation at break test method: cut the material to be tested into a sample with a size of 25 cm (length) x 2.5 cm (width), and mark the middle 5 cm length. Use a KJ-1065 electronic tensile testing machine (Guangdong Kejian Instrument Co., Ltd.) with a 50 kg sensor, set the clamp distance to 5 cm, and stretch at a speed of 10 cm / min until breaking, and record the elongation at break data.

[0042] The weather resistance test method is as follows: using a Q-lab QUV ultraviolet accelerated aging tester, using a UV lamp with a peak wavelength of 340 nm, outdoor weather resistance simulation test is carried out. One test cycle consists of two steps:

[0043] Step 1: temperature 60℃, irradiation intensity 0.71Mw / cm 2

[0044] Step 2: 4 hours of rain, temperature 40℃.

[0045] After repeating the above cycle for a total test time of 1000 hours,

[0046] (1) observe the coating with the naked eye.

[0047] (2) test the color change before and after weather resistance test with BYK-mac i colorimeter, and use ΔE to represent it.

[0048] If no cracks or local peeling are observed, and ΔE is less than 3, it indicates that the outdoor weather resistance is good.

[0049] Transparency test method: the transparency of the composite film is represented by the transmission haze value, and the specific test method is as follows: the composite film is attached to the surface of a 1 mm thick glass plate, and the haze value is tested with a transmission haze instrument of BYK-Garden. The lower the haze value, the better the transparency.

[0050] Each component in the formula is calculated by weight.

[0051] The pressure-sensitive adhesive layer is a pressure-sensitive adhesive formula commonly used in the art, which specifically includes: acrylic acid, methyl acrylate, laurylene, , butadiene, toluene.

[0052] The coating of the thermal insulation nanomaterial is prepared by using a conventional thermal insulation coating in the art. In the embodiments of the present application, a thermal insulation material slurry is prepared by using the following formula: 25 parts of a cesium tungstate powder dispersion liquid (solid content of 40%), 50 parts of a diluent (1,6-hexanediol diacrylate (HDDA)), 25 parts of an oligomer (polyurethane acrylate), 3 parts of an initiator (Irgacure 651), and 0.5 parts of an antioxidant (Tinuvin P). The parts in the following examples all refer to weight parts.

[0053] Example 1

[0054] Under a nitrogen atmosphere, 100 g of citric acid and 200 g of polyethylene glycol 600 are added to a round-bottom flask and mixed uniformly. The mixture is heated to 150°C and stirred for 2 hours. Then, 0.1 g of p-toluenesulfonic acid is added, and the reaction is continued for 1 hour with stirring. The reaction system is vacuumed to remove small molecular byproducts until the weight of the reaction system does not change significantly. Then, the reaction is stopped to obtain a polyester polyol.

[0055] In a round-bottom flask, the polyester polyol and a polylactic acid polyol (purchased from Anhui Huaihai Biological Technology Co., Ltd., model HPB500) are mixed uniformly in DMF. After being heated at 120°C for 2 hours, diphenylmethane diisocyanate (MDI) and a catalytic amount of dibutyltin dilaurate are added. The reaction is continued at 100°C for 3 hours to obtain a prepolymer.

[0056] A chain extender butane-1,4-diol is added, and the reaction is continued at 100°C to obtain a polyurethane elastomer solution.

[0057] The polyurethane elastomer solution is coated on a PET release film by using a roll coating method. After drying, two TPU base films are obtained. A coating layer containing thermal insulation nanomaterials is coated on the surface of the first base film, and a second base film is overlaid. Ultraviolet light is used for curing. A thermal insulation layer is formed between the two base films. The release film of the second TPU base film is peeled off, and a self-repairing protective coating layer is coated on the second base film (according to the method of patent CN201710820811.X). The release film of the first TPU base film is peeled off, and an acrylic pressure-sensitive adhesive solution is coated on the back of the first base film to form a pressure-sensitive adhesive layer. After drying, the product is obtained.

[0058] The multilayer composite film prepared in this example comprises a pressure-sensitive adhesive layer, a first base film, a thermal insulation nanomaterial layer, a second base film, and a self-repairing protective coating layer, which are stacked and combined in order from bottom to top. The thickness of the pressure-sensitive adhesive layer is 25 microns. The thickness of each of the first base film and the second base film is 20 microns. The thickness of the thermal insulation nanomaterial layer is 5 microns. The thickness of the self-repairing protective coating layer is 12 microns.

[0059] The detection results are as follows:

[0060] (1) The adhesion of the polyurethane coating is good, and it is not easy to fall off, with a 5B rating in the grid test;

[0061] (2) The elongation at break is 330%, and the breaking strength is 30 MPa; it has a self-repairing function;

[0062] (3) Good scratch resistance, 0000# copper wire load 1kg back and forth friction 1000 times or more without damage;

[0063] (4) Good weather resistance, after 1000 hours of repeated weathering cycles, no cracks or local peeling are observed on the coating surface, and ΔE = 2.0;

[0064] (5) The film is flat, and the leveling performance is excellent, with a 20-degree gloss of 94;

[0065] (6) Good transparency, with a transmission haze value of 1.0, reaching the optical performance of PET.

[0066] Example 2

[0067] Under a nitrogen atmosphere, 100g of citric acid and 200g of polyethylene glycol 600 were added to a round-bottom flask and mixed evenly, heated to 150°C and stirred for 2 hours, then 0.1g of concentrated sulfuric acid was added, and the reaction was continued for 1 hour. The reaction system was vacuumed to remove small molecular by-products until the weight of the reaction system did not change significantly, and then the reaction was stopped to obtain a polyester polyol;

[0068] In DMF, the above-mentioned polyester polyol and polylactic acid polyol (purchased from Anhui Huaihai Biological Technology Co., Ltd., model HPB1000) were added to a round-bottom flask and mixed evenly, heated to 120°C for 2 hours, then hexamethylene diisocyanate and a catalytic amount of dibutyltin dilaurate were added, and the reaction was continued at 100°C for 3 hours to obtain a prepolymer;

[0069] A chain extender, hexane-1,6-diol, was added, and the reaction was continued at 100°C to obtain a polyurethane elastomer solution;

[0070] The polyurethane elastomer solution was coated on a PET release film using a roll coating method, and after drying, two TPU base films were obtained. A coating layer containing thermal insulation nanomaterials was coated on the surface of the first base film, and then a second base film was covered. Ultraviolet light curing was performed to form a thermal insulation layer between the two base films. The release film of the second TPU base film was peeled off, and a self-repairing protective coating layer was coated on the second base film (according to the method of patent CN201710820811.X). The release film of the first TPU base film was peeled off, and an acrylic pressure-sensitive adhesive solution was coated on the back of the first base film to form a pressure-sensitive adhesive layer. After baking and drying, it was ready.

[0071] The multilayer composite film prepared in the embodiment comprises, from bottom to top, a pressure-sensitive adhesive layer, a first base film, a thermal insulation nanomaterial layer, a second base film, and a self-repairing protective coating, which are laminated and combined. The thickness of the pressure-sensitive adhesive layer is 20 microns, the thickness of the first base film and the second base film is 50 microns, the thickness of the thermal insulation nanomaterial layer is 15 microns, and the thickness of the self-repairing protective coating is 8 microns.

[0072] The detection effects are as follows:

[0073] (1) The adhesion of the polyurethane coating is good, and it is not easy to fall off, and the cross-hatch test reaches 5B;

[0074] (2) The elongation at break reaches 360%, the breaking strength reaches 35 MPa, and the self-repairing function is provided;

[0075] (3) The scratch resistance is good, and 0000# copper wire with a load of 1 kg is rubbed back and forth for more than 1000 times without damage;

[0076] (4) The weather resistance is good, and after repeated weather resistance cycles for 1000 hours, no cracks or local peeling are observed on the surface of the coating, and ΔE = 1.8;

[0077] (5) The film is flat, and the leveling performance is excellent, and the 20-degree gloss is 96;

[0078] (6) The transparency is good, the transmission haze value is 1.1, and the optical performance reaches that of PET.

Claims

1. A method for preparing a heat-insulating polyurethane multilayer film, comprising the following steps: (1) Under an inert atmosphere, citric acid and polyethylene glycol 600 are mixed evenly, heated and stirred, an acidic catalyst is added, and the reaction is stirred until the weight of the system does not change to obtain a polyester polyol; (2) In a solvent, under the action of a catalyst, polyester polyol and polylactic acid polyol are mixed evenly, and then polyisocyanate is added, and heated and stirred to react to obtain a prepolymer; (3) adding a chain extender and stirring the reaction to obtain a polyurethane elastomer solution; (4) coating the polyurethane elastomer solution on the PET release film, and drying to obtain a first TPU base film and a second TPU base film; (5) coating the surface of the first TPU base film with a coating containing a heat-insulating nanomaterial, then covering it with a second TPU base film, and curing it to form a heat-insulating layer between the two base films; (6) peeling off the release film of the second TPU base film and coating the self-repairing protective coating on the second base film; (7) Peel off the release film of the first TPU base film and apply a pressure-sensitive adhesive layer on the back of the first TPU base film, and bake and dry it.

2. The preparation method according to claim 1, wherein In step (1), the acidic catalyst is one or more of p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid; and the solvent is one or more of DMF, DMSO, THF, and methyl isobutyl ketone.

3. The preparation method according to claim 1, wherein In step (2), the catalyst is dibutyltin dilaurate, an organic bismuth catalyst, an organic zinc catalyst, or a tertiary amine catalyst; In step (2), the weight average molecular weight of the precursor is 1000-20000; In step (4), the polyurethane elastomer solution is preferably coated on the PET release film by roller coating, spraying or dipping.

4. The preparation method according to claim 1, wherein The polyisocyanate is selected from diphenylmethane diisocyanate, toluene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, methylene bis(4-cyclohexyl isocyanate) and mixtures thereof; In step (3), the weight average molecular weight of the polyurethane elastomer is 10,000-200,000.

5. The preparation method according to claim 1, wherein The chain extender is selected from one or more of ethane-1,2-diol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, diethylene glycol, and triethylene glycol.

6. The preparation method according to claim 1, wherein In step (5), the curing is baking curing or UV curing, preferably baking curing.

7. The preparation method according to claim 1, wherein The coating formula of the thermal insulation nanomaterial includes the following components in parts by weight: 20-25 parts of thermal insulation material slurry, 72-83 parts of film-forming material, and 0.5-0.6 parts of antioxidant; the thermal insulation material slurry is preferably a dispersion of lanthanum hexaboride, indium tin oxide, antimony tin oxide or cesium tungstate powder; when ultraviolet light curing is adopted, the film-forming material includes 50-55 parts of diluent, 20-25 parts of oligomer, and 2-3 parts of initiator; the diluent is preferably 1,6-hexanediol diacrylate, trimethylolpropane triacrylate or tripropylene glycol diacrylate; the oligomer is preferably polyurethane acrylate; when baking thermal curing is adopted, the film-forming material is polyacrylate or polyurethane.

8. A thermal insulating polyurethane multilayer film prepared by the preparation method according to any one of claims 1 to 7.

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