Low-tear PU protective film for vehicle-mounted screen

Abstract

The invention belongs to the field of protective films, and particularly relates to a low-tear PU (polyurethane) protective film for a vehicle-mounted screen, which comprises a polyurethane adhesive layer, the polyurethane adhesive layer comprises the following polyurethane resin; the polyurethane resin is prepared from the following substances in parts by weight: 60 to 80 parts of polycarbonate polyol, 5 to 10 parts of tetrahydrofuran copolymer polyol, 5 to 10 parts of polyester polyol and 10 to 20 parts of polyether polyol. The problems that the film tearing voltage of a PU protective film on glass with AG, AR and AF coatings is relatively high, and the pollution to the glass with the AG, AR and AF coatings at high temperature and high humidity for a long time is relatively poor are solved at the same time.

Description

Technical Field

[0001] The invention belongs to the field of protective films, and in particular relates to a low-tear PU protective film for a vehicle-mounted screen. Background Art

[0002] In order to prevent the display screen from being scratched by foreign objects during the production and shipping process or from being contaminated during stacking and transportation, a protective film is used in actual applications.

[0003] There are several significant problems with existing protective films. First, the protective film cannot have a low tearing voltage for glass with AG, AR, and AF coatings at the same time. Too high a tearing voltage will cause damage to the protective film during installation, while too low a tearing voltage will affect its adhesion and durability. The main mechanism of tearing voltage is: the polyurethane used in the PU protective film has good electrical insulation, so the static charge generated by friction is not easy to disappear. The accumulation of static charge will cause the tearing voltage to be generated when the protective film is torn off.

[0004] Secondly, it is impossible to achieve better protection and lower pollution for glass with AG, AR, and AF coatings under long-term high temperature and high humidity conditions. At present, the export volume by sea is increasing, and the sea transportation process will be accompanied by long-term high temperature and high humidity. After tearing off the protective film, the unreacted small molecular monomers, antistatic agents, surfactants, etc. in the adhesive layer may precipitate and remain on the surface of the glass and coating, affecting the optical properties of the product, so the pollution requirements for the protective film are more stringent. At present, there is no effective way to solve the above technical problems. Summary of the invention

[0005] The present application provides a low-tear PU protective film for a car screen, which simultaneously solves the problem that the PU protective film has a high tearing voltage for glass with AG, AR, and AF coatings, and has poor pollution resistance to high temperature and high humidity for a long time for glass with AG, AR, and AF coatings.

[0006] In order to achieve the above technical purpose, the technical solution adopted by the present application is a low-tear PU protective film for a vehicle-mounted screen, comprising a polyurethane adhesive layer; the polyurethane adhesive layer comprises the following polyurethane resin;

[0007] The polyurethane resin includes the following substances in parts by weight:

[0008] Polycarbonate polyol 60-80 parts

[0009] Tetrahydrofuran copolymer polyol 5-10

[0010] Polyester polyol 5-10

[0011] Polyether polyol 10-20.

[0012] As an improved technical solution of the present application, the viscosity of the polyurethane resin is 100-2000cps.

[0013] As an improved technical solution of the present application, the weight average molecular weight of the polyurethane resin is 10,000-50,000.

[0014] As an improved technical solution of the present application, the glass transition temperature of the polyurethane resin is -25--10°C.

[0015] As an improved technical solution of the present application, the polyurethane adhesive layer includes the following substances in parts by weight:

[0016] Polyurethane resin 100 parts

[0017] Curing agent 4-20 parts

[0018] Catalyst 0.05-0.5 parts

[0019] Delay agent 2-6 parts

[0020] Stabilizer 0.1-1 part

[0021] UV absorber 0.1-1 part

[0022] Adhesion promoter 0.1-1 part

[0023] Antistatic agent 0.1-1 part

[0024] 2-10 parts of antistatic additives.

[0025] As an improved technical solution of the present application, the curing agent is selected from any one of dimethyl diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate trimer, toluene diisocyanate trimer, isophorone diisocyanate trimer or tris(4-phenylisocyanate)thiophosphate, or a combination of at least two of them in any weight ratio.

[0026] As an improved technical solution of the present application, the catalyst is dibutyltin dilaurate, the retarder is acetylacetone, the stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, the adhesion promoter is titanate chelate or aluminum acetylacetonate, and the antistatic additive is a polyurethane modified substance.

[0027] As an improved technical solution of the present application, the ultraviolet absorber is any one of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'diphenylisopropyl)benzotriazole or 2-(2-hydroxy-3-dodecyl-5-methyl)benzotriazole, or a combination of at least two of them in any weight ratio.

[0028] As an improved technical solution of the present application, the antistatic agent is any one of bistrifluoromethylsulfonyl imide salt, coconut ethyl dimethylamine ethyl sulfate and polyalkylene glycol (3-laurylamide propyl) methyl sulfate or a combination of at least two of them in any weight ratio.

[0029] As an improved technical solution of the present application, the PU protective film includes a substrate layer, a polyurethane adhesive layer and a release film layer stacked in sequence; the thickness of the substrate layer is 25-125μm, the thickness of the polyurethane adhesive layer is 4-20μm, and the thickness of the release film layer is 12-75μm.

[0030] Beneficial Effects

[0031] The present invention selects the main adhesive raw material components of the PU protective film, further adds an adhesion promoter and screens an antistatic agent that is more resistant to precipitation and a modified polyurethane auxiliary agent to graft polyurethane to form high polarity to facilitate high-speed charge movement, thereby improving the static elimination ability of the material to improve aging pollution and obtain a lower film tearing voltage. The prepared PU protective film has a lower film tearing voltage, better pollution resistance, better exhaust resistance and good adhesion. The PU protective film provided by the present invention is suitable for the production and transportation protection of vehicle-mounted screens. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram showing the structure of a low-tear PU protective film is shown;

[0033] In the figure, 1-substrate layer, 2-PU adhesive layer, 3-release surface of release film. DETAILED DESCRIPTION

[0034] A low-tear PU protective film for a vehicle screen, comprising a polyurethane adhesive layer; the polyurethane adhesive layer (PU adhesive layer 2) comprises the following polyurethane resin;

[0035] The polyurethane resin includes the following substances in parts by weight:

[0036] Polycarbonate polyol 60-80 parts

[0037] Tetrahydrofuran copolymer polyol 5-10

[0038] Polyester polyol 5-10

[0039] Polyether polyol 10-20.

[0040] Tetrahydrofuran copolymer polyol, polyester polyol and polyether polyol are dissolved in ethyl acetate, stirred evenly, toluene diisocyanate trimer and dibutyltin dilaurate catalyst are added to carry out prepolymerization at 78°C, and after 4 hours, a mixture of polycarbonate polyol and toluene is added to continue the reaction at 82°C for 6 hours to obtain the polyurethane resin. In some embodiments, the viscosity of the polyurethane resin is 100-2000cps, preferably 300-2000cps.

[0041] In some embodiments, the weight average molecular weight of the polyurethane resin is 10,000-50,000, preferably 15,000-50,000.

[0042] In some embodiments, the polyurethane resin has a glass transition temperature of -25 to 10° C., preferably -20 to 15° C. A too high glass transition temperature will harden the adhesive layer, deteriorate the temperature resistance and deteriorate the exhaust performance; a too low glass transition temperature will soften the adhesive layer, deteriorate the high temperature and high humidity pollution resistance, and may also cause die-cutting glue overflow.

[0043] In some embodiments, the solid content of the polyurethane resin is 30%-40%, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, etc. The purpose is that too high a solid content will increase the viscosity after the solvent evaporates during the coating process, resulting in a poor appearance, and too low a solid content will cause a large amount of solvent waste, affecting energy consumption and cost.

[0044] In some embodiments, the polyurethane resin further includes a solvent, which is selected from any one of ethyl acetate, toluene, butyl acetate, and butanone, or a combination of at least two of them in any weight ratio.

[0045] As an improved technical solution of the present application, the polyurethane adhesive layer includes the following substances in parts by weight:

[0046] Polyurethane resin 100 parts

[0047] Curing agent 4-20 parts

[0048] Catalyst 0.05-0.5 parts

[0049] Delay agent 2-6 parts

[0050] Stabilizer 0.1-1 part

[0051] UV absorber 0.1-1 part

[0052] Adhesion promoter 0.1-1 part

[0053] Antistatic agent 0.1-1 part

[0054] 2-10 parts of antistatic additives.

[0055] The present invention selects the main raw material components of the PU protective film, further adds an adhesion promoter and selects an antistatic agent that is more resistant to precipitation and a modified polyurethane auxiliary agent to graft polyurethane to form high polarity to facilitate high-speed charge movement, thereby improving the static elimination ability of the material to improve aging pollution and obtain a lower film tearing voltage. The prepared PU protective film has a lower film tearing voltage, good pollution resistance, good exhaust resistance and good adhesion, and is suitable for the production and transportation protection of vehicle-mounted screens.

[0056] As an improved technical solution of the present application, the curing agent is selected from any one of dimethyl diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate trimer, toluene diisocyanate trimer, isophorone diisocyanate trimer or tris(4-phenylisocyanate)phosphothioate, or a combination of at least two of them in any weight ratio. The curing agent reacts with the polyurethane resin at high temperature to form a three-dimensional network structure.

[0057] As an improved technical solution of the present application, the catalyst is dibutyltin dilaurate, which functions to accelerate the reaction rate of isocyanate and hydroxyl in the curing agent and shorten the aging time.

[0058] The retarder is acetylacetone, which has the function of reducing the gel speed during coating and making the product appearance better during the coating process.

[0059] The stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, which can prevent small molecules from precipitating during high temperature and high humidity.

[0060] The adhesion promoter is a titanate chelate or aluminum acetylacetonate, and its function is to react with the hydroxyl groups in the substrate to increase the adhesion to the substrate.

[0061] The antistatic agent is a polyurethane modification: Chenzhuo Chemical K011, German BYK-163, etc., which is used to graft polyurethane to form high polarity to facilitate high-speed charge movement and charge extraction, thereby improving the static elimination ability of the material. The amount of the antistatic agent is preferably 5-10 parts.

[0062] As an improved technical solution of the present application, the ultraviolet absorber is any one of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'diphenylisopropyl)benzotriazole or 2-(2-hydroxy-3-dodecyl-5-methyl)benzotriazole or a combination of at least two of them in any weight ratio. The purpose is to prevent the product from yellowing.

[0063] As an improved technical solution of the present application, the antistatic agent is any one of bis(trifluoromethylsulfonyl)imide salt, cocoyl ethyl dimethylamine ethyl sulfate and polyalkylene glycol (3-laurylamide propyl) methyl sulfate salt or a combination of at least two of them in any weight ratio. The function is to reduce the impedance of the polyurethane adhesive layer, improve the conductivity and reduce the film tearing voltage.

[0064] As an improved technical solution of the present application, the PU protective film comprises a substrate layer, a polyurethane adhesive layer and a release film layer stacked in sequence; the thickness of the substrate layer is 25-125 μm, the thickness of the polyurethane adhesive layer is 4-20 μm,

[0065] The thickness of the release film layer is 12-75 μm, for example, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or 75 μm, etc. The release film layer is a PET single silicon release film layer, so that the machine can easily tear the release film when tearing it during automatic operation.

[0066] The release force of the PET single silicon release film is 10-30g / 25mm, for example, it can be 10g / 25mm, 12g / 25mm, 14g / 25mm, 16g / 25mm, 18g / 25mm, 20g / 25mm, 22g / 25mm, 24g / 25mm, 26g / 25mm, 28g / 25mm or 30g / 25mm, etc.

[0067] The preparation method of the PU protective film comprises the following steps:

[0068] (1) applying a polyurethane adhesive resin to a side of the PET having a high dyne value, and drying the resin to obtain a polyurethane adhesive layer and a substrate layer that are bonded to each other; the drying temperature is 100-130° C., for example, 100° C., 105° C., 110° C., 115° C., 120° C., 125° C., or 130° C., etc.; the drying time is 1-4 min., for example, 1 min., 1.5 min., 2 min., 2.5 min., 3 min., 3.5 min., or 4 min., etc.

[0069] (2) Compounding the release surface of the release film and the substrate layer with the polyurethane adhesive layer, and aging to obtain the PU protective film; the aging temperature is 40-50°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, etc. The aging time is 12-24h, for example, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, etc.

[0070] The PU protective film of the present application can be used in car screens, and can also be used on other coated glass, such as mobile phones, tablets, watches, and small computers.

[0071] The technical solution of the present application is fully and comprehensively described below in conjunction with specific embodiments.

[0072] Example 1

[0073] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 50 μm, a polyurethane adhesive layer with a thickness of 10 μm and a PET single silicon release film layer with a thickness of 50 μm which are stacked in sequence.

[0074] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0075] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (the polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 2 500, hydroxyl value 65) in a mass ratio of 70:5:10:15), 8 parts of curing agent (toluene diisocyanate trimer), 2 parts of delay agent, 0.2 parts of stabilizer, 0.2 parts of ultraviolet absorber (2-(2'-hydroxy-5'-methylphenyl) benzotriazole), 0.1 parts of catalyst, 0.3 parts of adhesion promoter, 0.3 parts of antistatic agent (bistrifluoromethylsulfonyl imide salt), 10 parts of antistatic auxiliary agent (Chenzhuo Chemical K011) and 120 parts of solvent;

[0076] The solvent is composed of ethyl acetate and toluene in a mass ratio of 7:3;

[0077] The preparation method of the polyurethane resin is as follows:

[0078] The polyurethane resin, curing agent, delay agent, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are mixed evenly to obtain a polyurethane resin with a solid content of 35%. The viscosity of the polyurethane resin is 300cps, the weight average molecular weight is 15,000, and the glass transition temperature is -15°C.

[0079] like Figure 1 As shown, the preparation method of the above PU protective film is as follows:

[0080] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 120° C. for 2 min to obtain a polyurethane adhesive layer (PU adhesive layer 2) and a substrate layer 1 that are bonded together;

[0081] (2) Compounding the release film release surface 3 and the adhesive surface of the substrate layer 1, and aging at 50° C. for 24 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 50 μm, the thickness of the polyurethane adhesive layer (PU adhesive layer 2) is 10 μm, and the thickness of the release film layer (release film release surface 3) is 50 μm.

[0082] Example 2

[0083] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 50 μm, a polyurethane adhesive layer with a thickness of 8 μm and a PET single silicon release film layer with a thickness of 50 μm which are stacked in sequence.

[0084] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0085] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 25 00, hydroxyl value 65) in a mass ratio of 80:5:5:10), 9 parts of curing agent (toluene diisocyanate trimer), 4 parts of retarder, 0.1 parts of stabilizer, 0.1 parts of UV absorber (2-(2'-hydroxy-5'-methylphenyl)benzotriazole), 0.05 parts of catalyst, 0.1 parts of adhesion promoter, 0.1 parts of antistatic agent (bistrifluoromethylsulfonyl imide salt), 10 parts of antistatic auxiliary agent (BYK-163) and 130 parts of solvent;

[0086] The solvent is composed of ethyl acetate and toluene in a mass ratio of 8:2;

[0087] The preparation method of the polyurethane resin is as follows:

[0088] The polyurethane resin, curing agent, delay agent, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are mixed evenly to obtain a polyurethane resin with a solid content of 33%. The viscosity of the obtained polyurethane resin is 500cps, the weight average molecular weight is 20,000, and the glass transition temperature is -20°C

[0089] The preparation method of the above PU protective film is as follows:

[0090] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 120° C. for 2 minutes to obtain a polyurethane adhesive layer and a PET substrate layer that are bonded together;

[0091] (2) Compounding the release surface 3 of the release film and the adhesive surface of the substrate layer 1, and aging at 45° C. for 24 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 50 μm, the thickness of the polyurethane adhesive layer is 8 μm, and the thickness of the release film layer is 50 μm.

[0092] Example 3

[0093] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 36 μm, a polyurethane adhesive layer with a thickness of 10 μm and a PET single silicon release film layer with a thickness of 25 μm which are stacked in sequence.

[0094] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0095] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (the polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 2 500, hydroxyl value 65) in a mass ratio of 75:8:7:10), 20 parts of curing agent (polymethylene polyphenyl isocyanate trimer), 2 parts of retarder, 1 part of stabilizer, 1 part of UV absorber (2-(2'-hydroxy-5'-methylphenyl) benzotriazole), 0.5 parts of catalyst, 1 part of adhesion promoter, 1 part of antistatic agent (coconut oil ethyl dimethylamine ethyl sulfate), 1 part of antistatic auxiliary agent (Chenzhuo Chemical K011) and 120 parts of solvent;

[0096] The solvent is composed of ethyl acetate and toluene in a mass ratio of 7:3;

[0097] The preparation method of the polyurethane resin is as follows:

[0098] The polyurethane resin, curing agent, delay agent, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are mixed evenly to obtain a polyurethane resin with a solid content of 35%. The viscosity of the obtained polyurethane resin is 400cps, the weight average molecular weight is 18,000, and the glass transition temperature is -18°C

[0099] The preparation method of the above PU protective film is as follows:

[0100] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 125° C. for 1 minute to obtain a polyurethane adhesive layer and a PET substrate layer that are bonded together;

[0101] (2) Compounding the release surface 3 of the release film and the adhesive surface of the substrate layer 1, and aging at 50° C. for 12 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 36 μm, the thickness of the polyurethane adhesive layer is 10 μm, and the thickness of the release film layer is 25 μm.

[0102] Example 4

[0103] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 36 μm, a polyurethane adhesive layer with a thickness of 5 μm and a PET single silicon release film layer with a thickness of 50 μm which are stacked in sequence.

[0104] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0105] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 2500 , hydroxyl value 65) in a mass ratio of 60:10:10:20), 16 parts of curing agent (dimethyl diphenylmethane diisocyanate), 2 parts of delay agent, 0.2 parts of stabilizer, 0.2 parts of ultraviolet absorber (2-(2'-hydroxy-5'-methylphenyl) benzotriazole), 0.1 parts of catalyst, 0.5 parts of adhesion promoter, 0.2 parts of antistatic agent (bistrifluoromethylsulfonyl imide salt), 10 parts of antistatic auxiliary agent (Chenzhuo Chemical K011) and 140 parts of solvent;

[0106] The solvent is composed of ethyl acetate and toluene in a mass ratio of 7:3;

[0107] The preparation method of the polyurethane resin is as follows:

[0108] The polyurethane resin, curing agent, delay agent, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are mixed evenly to obtain a polyurethane resin with a solid content of 33%. The viscosity of the obtained polyurethane resin is 2000cps, the weight average molecular weight is 50,000, and the glass transition temperature is -25°C

[0109] The preparation method of the above PU protective film is as follows:

[0110] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 130° C. for 2 minutes to obtain a polyurethane adhesive layer and a PET substrate layer that are bonded together;

[0111] (2) Compounding the release film release surface 3 and the adhesive surface of the substrate layer 1, and aging at 50° C. for 12 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 36 μm, the thickness of the polyurethane adhesive layer is 5 μm, and the thickness of the release film layer is 50 μm.

[0112] Example 5

[0113] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 50 μm, a polyurethane adhesive layer with a thickness of 5 μm and a PET single silicon release film layer with a thickness of 25 μm which are stacked in sequence.

[0114] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0115] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 2500, 65) in a mass ratio of 70:5:10:15), 20 parts of curing agent (dimethyl diphenylmethane diisocyanate), 6 parts of delay agent, 0.2 parts of stabilizer, 0.2 parts of ultraviolet absorber (2-(2'-hydroxy-3', 5' diphenylisopropyl) benzotriazole), 0.2 parts of catalyst, 0.3 parts of adhesion promoter, 0.3 parts of antistatic agent (bistrifluoromethylsulfonyl imide salt), 10 parts of antistatic auxiliary agent (BYK-163) and 130 parts of solvent;

[0116] The solvent is composed of ethyl acetate and toluene in a mass ratio of 7:3;

[0117] The preparation method of the polyurethane resin is as follows:

[0118] The polyurethane resin, curing agent, retarder, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are uniformly mixed to obtain a polyurethane adhesive resin with a solid content of 34%. The obtained polyurethane resin has a viscosity of 350 cps, a weight average molecular weight of 15,000, and a glass transition temperature of -20°C.

[0119] The preparation method of the above PU protective film is as follows:

[0120] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 130° C. for 2 minutes to obtain a polyurethane adhesive layer and a PET substrate layer that are bonded together;

[0121] (2) Compounding the release film release surface 3 and the adhesive surface of the substrate layer 1, and aging at 50° C. for 12 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 50 μm, the thickness of the polyurethane adhesive layer is 5 μm, and the thickness of the release film layer is 25 μm.

[0122] Example 6

[0123] This embodiment provides a PU protective film and a preparation method thereof. The structural schematic diagram of the PU protective film is as follows: Figure 1 As shown, it includes a PET substrate layer with a thickness of 75 μm, a polyurethane adhesive layer with a thickness of 5 μm and a PET single silicon release film layer with a thickness of 25 μm which are stacked in sequence.

[0124] The polyurethane adhesive layer is made of polyurethane adhesive resin;

[0125] The polyurethane resin comprises the following components in parts by weight: 100 parts of polyurethane resin (polyurethane glue is composed of polycarbonate polyol (Asahi Kasei T4672, molecular weight 2000, hydroxyl value 12-25), tetrahydrofuran copolymer polyol (Asahi Kasei PTXG-1800, molecular weight 1800, hydroxyl value 61), polyester polyol (Kuraray P5010, molecular weight 5000, hydroxyl value 21-24), polyether polyol (BASF TP2540, molecular weight 250 0, hydroxyl value 65) in a mass ratio of 70:5:10:15), 8 parts of curing agent (dimethyl diphenylmethane diisocyanate), 2 parts of delay agent, 0.2 parts of stabilizer, 0.2 parts of ultraviolet absorber (2-(2'-hydroxy-3', 5' diphenylisopropyl) benzotriazole), 0.2 parts of catalyst, 0.5 parts of adhesion promoter, 1 part of antistatic agent (bistrifluoromethylsulfonyl imide salt), 5 parts of antistatic auxiliary agent (Chenzhuo Chemical K011) and 130 parts of solvent;

[0126] The solvent is composed of ethyl acetate and toluene in a mass ratio of 7:3;

[0127] The preparation method of the polyurethane resin is as follows:

[0128] The polyurethane resin, curing agent, retarder, stabilizer, ultraviolet absorber, catalyst, adhesion promoter, antistatic agent, antistatic auxiliary agent, ethyl acetate and toluene are uniformly mixed to obtain a polyurethane adhesive resin with a solid content of 34%. The obtained polyurethane resin has a viscosity of 350 cps, a weight average molecular weight of 20,000, and a glass transition temperature of -20°C.

[0129] The preparation method of the above PU protective film is as follows:

[0130] (1) applying a polyurethane adhesive resin to the side of the PET with a higher dyne value, and drying at 130° C. for 2 minutes to obtain a polyurethane adhesive layer and a PET substrate layer that are bonded together;

[0131] (2) Compounding the release surface 3 of the release film and the adhesive surface of the substrate layer 1, and aging at 50° C. for 12 hours, to obtain the PU protective film. The thickness of the substrate layer 1 is 75 μm, the thickness of the polyurethane adhesive layer is 5 μm, and the thickness of the release film layer is 25 μm.

[0132] Example 7

[0133] The difference between this embodiment and embodiment 1 is that tetrahydrofuran copolymer polyol is not added, and the other components are the same as those in embodiment 1.

[0134] Example 8

[0135] The difference between this embodiment and embodiment 1 is that no antistatic additive is added, and the other aspects are the same as those of embodiment 1.

[0136] Comparative Example 1

[0137] The difference between this comparative example and Example 1 is that the amount of catalyst added is 0.6, and the other conditions are the same as those in Example 1.

[0138] Comparative Example 2

[0139] The difference between this comparative example and Example 1 is that the amount of curing agent added is 3, and the other conditions are the same as those in Example 1.

[0140] The performance of the PU protective film provided in the above embodiments and comparative examples was tested, and the test standards were as follows:

[0141] Viscosity test: GB / T2792-1998;

[0142] Film tearing voltage: film tearing voltage tester;

[0143] Exhaust performance: ISO 8296:2003

[0144] The performance test results of the PU protective films provided in the above embodiments and comparative examples are shown in Table 1 below:

[0145] Table 1 Performance test results of PU protective film

[0146]

[0147]

[0148] It can be seen from the contents of Table 1 that in Examples 1-5, the main body of the polyurethane resin remains basically unchanged. When the adhesion promoter, antistatic agent and antistatic auxiliary agent are changed, good adhesion, lower film tearing voltage and better pollution resistance can be obtained. Changing the glue thickness does not affect the peeling force, and changing the amount of curing agent added changes the peeling force significantly. From Example 6, when the amount of antistatic agent added is large and the glue thickness is thin, long-term aging will result in obvious ring marks and a small amount of white mist. From Example 7, without adding tetrahydrofuran copolymer polyol, the glue is harder, tg is higher, the exhaust performance is poor when laminating glass, and the charge accumulates more, and the film tearing voltage is too large and the peeling force is low. From Example 8, it seems that without adding antistatic auxiliary agent, the charge cannot be completely derived when tearing the film, resulting in the film tearing voltage becoming higher. From Comparative Example 1, the amount of catalyst added is too large, the reaction is too fast, the glue layer has not been tightly combined with the film and has formed a film, the adhesion is very poor, and degumming will occur when laminating TP for a long time. From Comparative Example 2, the amount of curing agent is too small, the peeling force is too large, the reaction is incomplete, the glue layer is soft, and the pollution resistance is also poor.

[0149] In summary, the present invention selects the main adhesive raw material components of the PU protective film, further adds an adhesion promoter and screens an antistatic agent that is more resistant to precipitation and a modified polyurethane additive to graft polyurethane to form high polarity to facilitate high-speed charge movement, thereby improving the static electricity elimination ability of the material to improve aging pollution and obtain a lower tearing voltage. The prepared PU protective film has a lower tearing voltage, better pollution resistance, better exhaust resistance and good adhesion. The PU protective film provided by the present invention is suitable for the production and transportation protection of vehicle-mounted screens.

[0150] The applicant declares that the present invention illustrates the detailed process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A low tear PU protective film for a car screen, comprising a polyurethane adhesive layer; characterized in that: The polyurethane adhesive layer includes the following polyurethane resin; The polyurethane resin is formed by polymerization of the following materials in parts by weight: Polycarbonate polyol 60-80 parts 5-10 parts of tetrahydrofuran copolymer polyol Polyester polyol 5-10 parts Polyether polyol 10-20 parts.

2. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The viscosity of the polyurethane resin is 100-2000 cps.

3. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The weight average molecular weight of the polyurethane resin is 10,000-50,000.

4. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The glass transition temperature of the polyurethane resin is -25--10°C.

5. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The polyurethane adhesive layer includes the following substances in parts by weight: Polyurethane resin 100 parts Curing agent 4-20 parts Catalyst 0.05-0.5 parts Delay agent 2-6 parts Stabilizer 0.1-1 part UV absorber 0.1-1 part Adhesion promoter 0.1-1 part Antistatic agent 0.1-1 part 2-10 parts of antistatic additives.

6. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The curing agent is selected from any one of dimethyl diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate trimer, toluene diisocyanate trimer, isophorone diisocyanate trimer or tris(4-phenylisocyanate) thiophosphate, or a combination of at least two of them in any weight ratio.

7. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate, the retarder is acetylacetone, the stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, the adhesion promoter is titanate chelate or aluminum acetylacetonate, and the antistatic auxiliary agent is a polyurethane modification.

8. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The ultraviolet absorber is any one of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'diphenylisopropyl)benzotriazole or 2-(2-hydroxy-3-dodecyl-5-methyl)benzotriazole or a combination of at least two of them in any weight ratio.

9. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The antistatic agent is any one of bis(trifluoromethylsulfonyl)imide salt, coconut oil ethyl dimethylamine ethyl sulfate and polyalkylene glycol (3-laurylamide propyl) methyl sulfate or a combination of at least two of them in any weight ratio.

10. The low tear PU protective film for vehicle screen according to claim 1, characterized in that: The PU protective film comprises a substrate layer, a polyurethane adhesive layer and a release film layer stacked in sequence; the polyurethane adhesive layer is coated on the side of the substrate layer with a relatively high dyne value; the thickness of the substrate layer is 25-125 μm, the thickness of the polyurethane adhesive layer is 4-20 μm, and the thickness of the release film layer is 12-75 μm.

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