A polycarbonate sheet with enhanced weather resistance and preparation method thereof

Abstract

The invention discloses a polycarbonate sheet with enhanced weather resistance and a preparation method thereof, which belongs to the technical field of polycarbonate sheets, and comprises a polycarbonate sheet body and a weather-resistant coating coated on the surface of the polycarbonate sheet body, wherein the weather-resistant coating comprises the following raw materials in parts by weight: 100 parts of fluorocarbon resin, 80-120 parts of organic solvent, 20-30 parts of curing agent, 12-16 parts of modified nano titanium dioxide, and 0.5-2 parts of catalyst. The invention coats a layer of weather-resistant coating on the surface of the polycarbonate sheet, and the weather-resistant coating has a multi-effect anti-aging mechanism and good flexibility, can effectively improve the weather resistance of the polycarbonate sheet, expand the application range of the polycarbonate sheet, and increase its service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of polycarbonate sheets, and in particular, relates to a polycarbonate sheet with enhanced weather resistance and a preparation method thereof. Background Art

[0002] Polycarbonate (PC for short) is a high molecular polymer containing carbonate groups in the molecular chain. According to the structure of the ester group, it can be divided into aliphatic, aromatic, aliphatic-aromatic and other types. Polycarbonate board is made of polycarbonate polymer as raw material, using advanced formula and the latest extrusion process technology. PC board is a new type of high-strength, light-transmitting building material, and is the best building material to replace glass and plexiglass. PC board has more excellent properties such as lightness, super strength, flame retardancy and sound insulation than laminated glass, tempered glass, hollow glass, etc., and has become a popular building decoration material.

[0003] However, when it is used in an environment exposed to sunlight, it will be exposed to sunlight for a long time and easily fade. Its own weather resistance can no longer meet the requirements of use under such conditions, and its weather resistance needs to be further enhanced. In the prior art, ultraviolet absorbers are often added to polycarbonate. Although they can improve the weather resistance of PC boards to a certain extent, the effect of the added ultraviolet absorbers is limited. Summary of the invention

[0004] The object of the present invention is to provide a polycarbonate sheet with enhanced weather resistance and a preparation method thereof. By coating a layer of weather-resistant coating on the surface of the polycarbonate sheet, the weather-resistant coating has a multi-effect anti-aging mechanism and good flexibility, which can effectively improve the weather resistance of the polycarbonate sheet, expand the application range of the polycarbonate sheet and increase its service life.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A polycarbonate sheet with enhanced weather resistance comprises a polycarbonate sheet body and a weather-resistant coating coated on the surface of the polycarbonate sheet body, wherein the weather-resistant coating comprises the following raw materials in parts by weight:

[0007] 100 parts of fluorocarbon resin, 80-120 parts of organic solvent, 20-30 parts of curing agent, 12-16 parts of modified nano titanium dioxide, and 0.5-2 parts of catalyst.

[0008] Furthermore, the fluorocarbon resin is one or a mixture of any proportion of polyvinylidene fluoride, polychlorotrifluoroethylene, polytetrafluoroethylene, ethylene / tetrafluoroethylene copolymer, and ethylene / trichlorofluoroethylene copolymer.

[0009] Furthermore, the organic solvent is one of toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl isobutyl ketone, isopropanol, and N-methylpyrrolidone, or a mixture of several of them in any proportion.

[0010] Furthermore, the curing agent is one or a mixture of any proportion of toluene diisocyanate trimer, toluene diisocyanate prepolymer, hexamethylene diisocyanate trimer, diphenylmethane diisocyanate trimer and isophorone diisocyanate trimer.

[0011] Furthermore, the catalyst is an organotin catalyst.

[0012] Furthermore, the modified nano titanium dioxide is prepared by the following steps:

[0013] S1. Ultrasonic dispersion of nano-titanium dioxide in an ethanol aqueous solution (volume fraction 50%) according to a solid-liquid ratio of 1 g:10-15 mL, then adding silane coupling agent KH550, stirring continuously for 2-3 hours, filtering, washing, and drying to obtain pretreated nano-titanium dioxide;

[0014] The amount of silane coupling agent KH550 added is 35-45% of the mass of nano titanium dioxide;

[0015] Pre-treating nano-titanium dioxide with silane coupling agent KH550, and grafting molecular chains of silane coupling agent KH550 on the surface of nano-titanium dioxide;

[0016] S2. Add 2,2,6,6-tetramethylpiperidinamine, triethylamine and acetone to a dry three-necked flask, place the flask in an ice bath, stir and mix, and when the system temperature is stabilized at 0-2°C, slowly drip 4-chlorobutyric acid in acetone under stirring. After the dropwise addition is completed, react at 0-2°C for 3-4h, and remove the solvent by vacuum rotary evaporation to obtain an intermediate product;

[0017] The molar ratio of 2,2,6,6-tetramethylpiperidinamine, triethylamine and 4-chlorobutyric acid is 1:1:1;

[0018] The -NH2 on the 2,2,6,6-tetramethylpiperidinamine molecule undergoes a nucleophilic substitution reaction with 4-chlorobutyric acid (halogenated hydrocarbon), and the process is shown below to obtain an intermediate product:

[0019]

[0020] S3, remove the air in the four-necked flask with N2, add the intermediate product and tetrahydrofuran, stir and mix evenly, place in an ice water bath, slowly drop into a tetrahydrofuran mixture containing cetyl chloride and triethylamine under stirring, after the dropwise addition is complete, heat to 40°C and react for 3-4h, and after the reaction is completed, perform reduced pressure distillation to obtain a modifier;

[0021] The ratio of the intermediate product, cetyl chloride and triethylamine used is 24.2g:26.1g:10.2g;

[0022] The -NH- on the intermediate product molecule undergoes a nucleophilic substitution reaction with the -Cl on the chlorocetylene molecule to obtain a modifier. The reaction process is as follows:

[0023]

[0024] S4, mixing the pretreated nano titanium dioxide, the modifier and DMF (N,N-dimethylformamide), adding DCC (dicyclohexylcarbodiimide) and DMAP (4-dimethylaminopyridine), magnetically stirring for 1-2 hours, then placing in a 60°C water bath for ultrasonication for 2-3 hours, then removing the water bath and magnetically stirring at room temperature for 24 hours, filtering, washing with anhydrous ethanol for 3-4 times, drying, and grinding to obtain modified nano titanium dioxide;

[0025] The ratio of the amount of pretreated nano-titanium dioxide, modifier, DCC and DMAP is 10g:2-3g:0.9g:0.08g;

[0026] Under the action of DCC and DMAP, -NH2 (introduced by silane coupling agent KH550) on the surface of pretreated nano-titanium dioxide undergoes amidation reaction with -COOH on the modifier molecule to obtain modified nano-titanium dioxide.

[0027] The obtained modified nano titanium dioxide is nano titanium dioxide with organic molecular chains grafted on the surface. It is well known that nano titanium dioxide has excellent anti-ultraviolet aging performance, but it is an inorganic nano material and is difficult to be evenly dispersed in the film-forming matrix (polymer) of the coating. The surface of the nano titanium dioxide of the present invention is grafted with organic molecular chains, which is equivalent to forming an organic layer on its surface, which can effectively improve the compatibility of nano titanium dioxide with the film-forming matrix, thereby promoting its uniform dispersion in the coating; in addition, the grafted organic molecular chain has hindered amine and long carbon chain structure in terms of structure. Hindered amine is a kind of photoinhibiting The effective ingredient for anti-aging is an organic anti-aging ingredient. It has a different anti-aging mechanism from nano titanium dioxide. Therefore, the two play a synergistic anti-aging role. Compared with the method of adding organic hindered amines alone, the hindered amines grafted on nano titanium dioxide are dispersed in the coating with the nano titanium dioxide, which has the advantage of being difficult to seep out, and can ensure the durability of the anti-aging performance; the long carbon chain structure (16 carbon chains) is a highly flexible carbon chain, which can penetrate between the molecular chains of fluorocarbon resin (film-forming matrix), which can not only improve the interaction between the modified nano titanium dioxide and the film-forming matrix, but also improve the flexibility of the coating.

[0028] A method for preparing a polycarbonate sheet with enhanced weather resistance comprises the following steps:

[0029] The first step is to use a high-pressure air gun to clean the dust on the surface of the polycarbonate sheet, and then use alcohol to clean the oil on the surface;

[0030] Step 2: Add the components of the coating into a stirring kettle according to the proportion, stir and mix evenly, and then homogenize for 20-30 minutes to obtain a weather-resistant coating;

[0031] The third step is to apply the weather-resistant coating on the surface of the polycarbonate sheet body with a coating thickness of 20-30 μm, and dry and cure at a temperature of 150-180° C. for 2-3 minutes to obtain the polycarbonate sheet.

[0032] Beneficial effects of the present invention:

[0033] By coating a layer of weather-resistant coating on the surface of the polycarbonate sheet, the weather-resistant coating has a multi-effect anti-aging mechanism and good flexibility, which can effectively improve the weather resistance of the polycarbonate sheet, expand the application range of the polycarbonate sheet and increase its service life. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1

[0036] Preparation of modified nano-titanium dioxide:

[0037] S1. Ultrasonic dispersion of 10 g of nano-titanium dioxide in 100 mL of ethanol aqueous solution (volume fraction 50%) was performed, and then 3.5 g of silane coupling agent KH550 was added, and stirring was continued for 2 h. After suction filtration, washing, and drying, pretreated nano-titanium dioxide was obtained;

[0038] S2. Add 0.1 mol of 2,2,6,6-tetramethylpiperidinamine, 0.1 mol of triethylamine and 80 mL of acetone to a dry three-necked flask, place the flask in an ice bath, stir and mix, and when the system temperature is stabilized at 0-2°C, slowly drip 60 mL of acetone solution containing 0.1 mol of 4-chlorobutyric acid under stirring, react at 0-2°C for 3 h after the dropwise addition, and remove the solvent by vacuum rotary evaporation to obtain an intermediate product;

[0039] S3, remove the air in the four-necked flask with N2, add 24.2g of the intermediate product and 100mL of tetrahydrofuran, stir and mix evenly, place in an ice-water bath, slowly drop 70mL of tetrahydrofuran mixed solution containing 26.1g of cetyl chloride and 10.2g of triethylamine under stirring, after the addition is complete, heat to 40°C and react for 3h, and after the reaction is completed, distill under reduced pressure to obtain a modifier;

[0040] S4. Mix 10 g of pretreated nano titanium dioxide, 2 g of modifier and 50 mL of DMF, add 0.9 g of DCC and 0.08 g of DMAP, stir magnetically for 1 h, then place in a 60°C water bath for 2 h, remove the water bath and stir magnetically for 24 h at room temperature, filter, wash with anhydrous ethanol 3 times, dry, and grind to obtain modified nano titanium dioxide.

[0041] Embodiment 2

[0042] Preparation of modified nano-titanium dioxide:

[0043] S1. Ultrasonic dispersion of 10 g of nano-titanium dioxide in 150 mL of ethanol aqueous solution (volume fraction 50%) was performed, and then 4.5 g of silane coupling agent KH550 was added, and stirring was continued for 3 h. After suction filtration, washing, and drying, pretreated nano-titanium dioxide was obtained;

[0044] S2. Add 0.1 mol of 2,2,6,6-tetramethylpiperidinamine, 0.1 mol of triethylamine and 80 mL of acetone to a dry three-necked flask, place the flask in an ice bath, stir and mix, and when the system temperature is stabilized at 0-2°C, slowly drip 60 mL of acetone solution containing 0.1 mol of 4-chlorobutyric acid under stirring, react at 0-2°C for 4 h after the addition is complete, and remove the solvent by vacuum rotary evaporation to obtain an intermediate product;

[0045] S3, remove the air in the four-necked flask with N2, add 24.2g of the intermediate product and 100mL of tetrahydrofuran, stir and mix evenly, place in an ice-water bath, slowly dropwise add 70mL of tetrahydrofuran mixed solution containing 26.1g of cetyl chloride and 10.2g of triethylamine under stirring, after the addition is complete, heat to 40°C and react for 4h, and after the reaction is completed, distill under reduced pressure to obtain a modifier;

[0046] S4. Mix 10 g of pretreated nano titanium dioxide, 3 g of modifier and 50 mL of DMF, add 0.9 g of DCC and 0.08 g of DMAP, stir magnetically for 2 h, then place in a 60°C water bath for 3 h, remove the water bath and stir magnetically for 24 h at room temperature, filter, wash with anhydrous ethanol 4 times, dry, and grind to obtain modified nano titanium dioxide.

[0047] Embodiment 3

[0048] Preparation of polycarbonate sheets with enhanced weather resistance:

[0049] The first step is to use a high-pressure air gun to clean the dust on the surface of the polycarbonate sheet, and then use alcohol to clean the oil on the surface;

[0050] Step 2: Add 100 parts of polyvinylidene fluoride, 80 parts of toluene, 20 parts of toluene diisocyanate trimer, 12 parts of modified nano titanium dioxide prepared in Example 1, and 0.5 parts of dibutyltin dilaurate into a stirring tank by weight, stir and mix evenly, and then homogenize for 20 minutes to obtain a weather-resistant coating;

[0051] The third step is to apply the weather-resistant coating on the surface of the polycarbonate sheet body with a coating thickness of 20 μm, and dry and cure it at a temperature of 150° C. for 2 minutes to obtain the polycarbonate sheet.

[0052] Embodiment 4

[0053] Preparation of polycarbonate sheets with enhanced weather resistance:

[0054] The first step is to use a high-pressure air gun to clean the dust on the surface of the polycarbonate sheet, and then use alcohol to clean the oil on the surface;

[0055] Step 2: Add 100 parts of polytrifluorochloroethylene, 100 parts of xylene, 25 parts of toluene diisocyanate prepolymer, 14 parts of modified nano titanium dioxide prepared in Example 1, and 1.2 parts of stannous octoate into a stirring tank by weight, stir and mix evenly, and then homogenize for 25 minutes to obtain a weather-resistant coating;

[0056] The third step is to apply the weather-resistant coating on the surface of the polycarbonate sheet body with a coating thickness of 25 μm, and dry and cure it at a temperature of 165° C. for 2.5 minutes to obtain the polycarbonate sheet.

[0057] Embodiment 5

[0058] Preparation of polycarbonate sheets with enhanced weather resistance:

[0059] The first step is to use a high-pressure air gun to clean the dust on the surface of the polycarbonate sheet, and then use alcohol to clean the oil on the surface;

[0060] Step 2: Add 100 parts of polytetrafluoroethylene, 120 parts of ethyl acetate, 30 parts of hexamethylene diisocyanate trimer, 16 parts of modified nano titanium dioxide prepared in Example 1, and 2 parts of dibutyltin dilaurate into a stirring tank, stir and mix evenly, and then homogenize for 30 minutes to obtain a weather-resistant coating;

[0061] The third step is to apply the weather-resistant coating on the surface of the polycarbonate sheet body with a coating thickness of 30 μm, and dry and cure it at a temperature of 180° C. for 3 minutes to obtain the polycarbonate sheet.

[0062] Comparative Example

[0063] Polycarbonate body.

[0064] The following performance tests were performed on Examples 3-5 and the comparative example:

[0065] Hardness test: According to GB / T 6739-2006 standard: Pencil hardness (manual method), the specific method is: fix the polycarbonate sheet with the paint film facing up on the experimental platform, fix the pencil at a 45-degree angle to the object to be tested and scratch the paint film.

[0066] Weathering test: GB / T 14522-2008 Fix the sheet with the paint film facing upward in a QUV aging test chamber to test the UV aging performance;

[0067] The measured results are shown in the following table:

[0068] Embodiment 3 Embodiment 4 Embodiment 5 Comparative Example Pencil hardness 3H 3H 3H 2H Weather resistance / h 99 105 108 72

[0069] It can be seen from the above test results that the polycarbonate sheet obtained by the present invention has good physical properties and weather resistance.

[0070] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A polycarbonate sheet with enhanced weather resistance, characterized in that: It comprises a polycarbonate sheet body and a weather-resistant coating coated on the surface of the polycarbonate sheet body, wherein the weather-resistant coating comprises the following raw materials in parts by weight: 100 parts of fluorocarbon resin, 80-120 parts of organic solvent, 20-30 parts of curing agent, 12-16 parts of modified nano titanium dioxide, and 0.5-2 parts of catalyst.

2. The polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The fluorocarbon resin is one or a mixture of any proportion of polyvinylidene fluoride, polychlorotrifluoroethylene, polytetrafluoroethylene, ethylene / tetrafluoroethylene copolymer, and ethylene / trichlorofluoroethylene copolymer.

3. The polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The organic solvent is one of toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl isobutyl ketone, isopropanol and N-methylpyrrolidone, or a mixture of the above in any proportion.

4. The polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The curing agent is one of toluene diisocyanate trimer, toluene diisocyanate prepolymer, hexamethylene diisocyanate trimer, diphenylmethane diisocyanate trimer and isophorone diisocyanate trimer, or a mixture of several of them in any proportion.

5. The polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The catalyst is an organotin catalyst.

6. The polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The modified nano titanium dioxide is prepared by the following steps: S1. Ultrasonic dispersion of nano-titanium dioxide in an ethanol aqueous solution according to a solid-liquid ratio of 1 g: 10-15 mL, then adding silane coupling agent KH550, stirring continuously for 2-3 hours, filtering, washing, and drying to obtain pretreated nano-titanium dioxide; S2. Add 2,2,6,6-tetramethylpiperidinamine, triethylamine and acetone to a dry three-necked flask, place the flask in an ice bath, stir and mix, and when the system temperature is stabilized at 0-2°C, slowly drip 4-chlorobutyric acid in acetone under stirring. After the dropwise addition is completed, react at 0-2°C for 3-4h, and remove the solvent by vacuum rotary evaporation to obtain an intermediate product; S3, remove the air in the four-necked flask with N2, add the intermediate product and tetrahydrofuran, stir and mix evenly, place in an ice water bath, slowly drop into a tetrahydrofuran mixture containing cetyl chloride and triethylamine under stirring, after the dropwise addition is complete, heat to 40°C and react for 3-4h, and after the reaction is completed, perform reduced pressure distillation to obtain a modifier; S4. Mix the pretreated nano-titanium dioxide, modifier and DMF, add DCC and DMAP, stir magnetically for 1-2 hours, then place in a 60°C water bath for ultrasonication for 2-3 hours, remove the water bath and stir magnetically for 24 hours at room temperature, filter, wash, dry and grind to obtain modified nano-titanium dioxide.

7. The polycarbonate sheet with enhanced weather resistance according to claim 6, characterized in that: In step S2, the molar ratio of 2,2,6,6-tetramethylpiperidinamine, triethylamine and 4-chlorobutyric acid is 1:1:

1.

8. The polycarbonate sheet with enhanced weather resistance according to claim 6, characterized in that: In step S3, the ratio of the intermediate product, cetyl chloride and triethylamine used is 24.2 g:26.1 g:10.2 g.

9. The polycarbonate sheet with enhanced weather resistance according to claim 6, characterized in that: In step S4, the ratio of the amount of pretreated nano titanium dioxide, modifier, DCC and DMAP is 10g:2-3g:0.9g:0.08g.

10. The method for preparing a polycarbonate sheet with enhanced weather resistance according to claim 1, characterized in that: The following steps are involved: The first step is to use a high-pressure air gun to clean the dust on the surface of the polycarbonate sheet, and then use alcohol to clean the oil on the surface; Step 2: Add the components of the coating into a stirring kettle according to the proportion, stir and mix evenly, and then homogenize for 20-30 minutes to obtain a weather-resistant coating; The third step is to apply the weather-resistant coating on the surface of the polycarbonate sheet body, dry and solidify it, and obtain the polycarbonate sheet.

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