A multi-angle color-changing film for road signs and its preparation process

Abstract

The invention relates to the field of multi-angle color-changing films, and specifically discloses a multi-angle color-changing film for a road sign and a preparation process thereof; the preparation process of the multi-angle color-changing film comprises the following steps: S1: dissolving hydroxyethyl methacrylate in a solvent, adding diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine, stirring and reacting until the isocyanate content no longer decreases, and removing the solvent to obtain an anti-ultraviolet agent; S2: taking polyurethane acrylate, an anti-ultraviolet agent, styrene, ethyl acrylate, and methyl methacrylate, mixing them evenly, adding benzoyl peroxide, reacting and polymerizing, and obtaining an acrylic resin; S3: adding a metal pigment to butyl acetate and stirring evenly; adding a metal pigment directing agent and an acrylic resin, dispersing them evenly, and then adding a drying agent to disperse them, so as to obtain a multi-angle color-changing coating; applying the multi-angle color-changing coating on the surface of the road sign, and drying, so as to obtain a multi-angle color-changing film.

Description

Technical Field

[0001] The present invention relates to the field of multi-angle color-changing films, and specifically discloses a multi-angle color-changing film for road signs and its preparation process. Background Art

[0002] At present, road signs generally use fixed-color markings to indicate different lanes. However, for drivers, it may be difficult to quickly and accurately identify their own lanes under high-speed driving or complex traffic conditions, presenting certain safety hazards. Traditional solutions are to set more prominent markings or increase the number of markings on road signs to improve recognition. However, these methods do not fundamentally change the limitations of fixed-color markings.

[0003] Coating a multi-angle color-changing film on road signs can display different colors according to the viewing angle change, enabling drivers to quickly distinguish their lanes during rapid driving and reducing traffic safety hazards. Therefore, it is of great significance to study a multi-angle color-changing film for road signs with good weather resistance, wear resistance, and stain resistance and its preparation process. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-angle color-changing film for road signs and its preparation process to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A preparation process of a multi-angle color-changing film for road signs, characterized by comprising the following steps:

[0006] S1: Dissolve 2-hydroxyethyl methacrylate in a solvent, add diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine, stir and react until the isocyanate group content no longer decreases, remove the solvent, and obtain an ultraviolet light absorber.

[0007] S2: Take polyurethane acrylate, ultraviolet light absorber, styrene, ethyl acrylate, and methyl methacrylate, mix them evenly, add benzoyl peroxide, and react and polymerize to obtain an acrylic resin.

[0008] S3: Add metal pigments to butyl acetate and stir evenly; add metal pigment orienting agents and acrylic resin, disperse evenly, then add driers and disperse to obtain a multi-angle color-changing coating; coat the multi-angle color-changing coating on the surface of the road sign and dry it to obtain a multi-angle color-changing film.

[0009] Preferably, in the ultraviolet inhibitor, the molar ratio of hydroxyethyl methacrylate, diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidineamine is 1:(2-2.2):(0.8-1):(0.8-1); the diisocyanate is isophorone diisocyanate; the solvent is acetone; the addition amount of acetone is 12 times that of hydroxyethyl methacrylate;

[0010] The acrylic resin comprises the following raw materials in parts by mass: 30-35 parts of polyurethane acrylate, 10-15 parts of ultraviolet inhibitor, 20-25 parts of styrene, 30-35 parts of ethyl acrylate, 5-8 parts of methyl methacrylate, and 1.5-2 parts of benzoyl peroxide;

[0011] The multi-angle color-changing coating comprises the following raw materials in parts by mass: 5-8 parts of metal pigment, 15-20 parts of butyl acetate, 8-12 parts of metal pigment orienting agent, 70-80 parts of acrylic resin, and 0.01-0.02 parts of dryer; the dryer is dibutyltin dilaurate; the metal pigment orienting agent is cellulose acetate butyrate.

[0012] Preferably, the preparation of the polyurethane acrylate comprises the following steps: taking polytetrahydrofuran diol, 5-heneicosylresorcinol, acetone, and water, stirring evenly, heating up, adding diisocyanate and dibutyltin dilaurate, stirring and reacting to obtain a prepolymer; adding trimethylolpropane, reacting at 60-65°C for 1-2 h, adding modified sodium alginate and hydroxyethyl methacrylate, and continuing to stir and react until the content of isocyanate group no longer decreases, and rotary evaporating to remove the solvent to obtain polyurethane acrylate.

[0013] Preferably, the polyurethane acrylate comprises the following raw materials in parts by mass: 10-15 parts of polytetrahydrofuran diol, 5-8 parts of 5-heneicosylresorcinol, 20-25 parts of acetone, 5-8 parts of water, 10-15 parts of diisocyanate (isophorone diisocyanate), 0.5-0.8 parts of dibutyltin dilaurate, 5-6 parts of trimethylolpropane, 2-3 parts of modified sodium alginate, and 6-10 parts of hydroxyethyl methacrylate.

[0014] Preferably, the preparation of the modified sodium alginate comprises the following steps: taking sodium alginate, adding a mixed solvent, adding 2,4-difluorophenyl isocyanate, mixing evenly, stirring and reacting until the content of isocyanate group no longer decreases, and removing the mixed solvent to obtain modified sodium alginate.

[0015] Preferably, the molar ratio of sodium alginate to 2,4-difluorophenyl isocyanate is 1:(1-1.2); the mixed solvent is water and acetone with a volume ratio of 3:1, and the addition amount is 10 times the mass of sodium alginate.

[0016] Preferably, the coating thickness of the multi-angle color-changing coating is 20-30 μm.

[0017] Preferably, the specific drying process is: baking at 75-80 °C for 110-120 min.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The acrylic resin used to prepare the multi-angle color-changing coating of the present invention is obtained by polymerizing a certain number of parts of polyurethane acrylate, ultraviolet inhibitor, styrene, ethyl acrylate, and methyl methacrylate;

[0019] Among them, polyurethane acrylate has good wear resistance. The raw materials also include 5-heneicosylresorcinol, which has hydrophobicity and can effectively improve the anti-corrosion performance and waterproof and anti-fouling performance of the coating; adding trimethylolpropane makes it have a hyperbranched structure, improves the mechanical properties and has good fluidity and film-forming properties. Its end is also grafted with sodium alginate modified with 2,4-difluorophenyl isocyanate. Due to the presence of fluorine and benzene, the hydrophilic and hydrophobic properties of the modified sodium alginate are adjusted, and it has emulsifying ability and can help the dispersion of metal pigments; therefore, there is no need to additionally add leveling agents, dispersants and other additives;

[0020] The ultraviolet inhibitor prepared by the present invention is obtained by compounding hydroxyethyl methacrylate, diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidineamine. It contains double bonds and can participate in the polymerization reaction, improving the problems of poor dispersibility and compatibility when directly adding ultraviolet auxiliary agents, and also improving the problem that the direct addition of small molecule additives will precipitate and cause performance degradation. Specific Embodiments

[0021] The following are the preferred embodiments of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. For those of ordinary skill in the art in this technical field, without departing from the principle of the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0022] Unless otherwise specified, the following parts are all parts by mass;

[0023] Example 1: S1: Take sodium alginate, add a mixed solvent, add 2,4-difluorophenyl isocyanate, mix evenly, stir and react at 55 °C until the isocyanate group content no longer decreases, remove the mixed solvent, and obtain modified sodium alginate; the molar ratio of sodium alginate to 2,4-difluorophenyl isocyanate is 1:1;

[0024] S2: Add 12 parts of polytetrahydrofuran diol, 6 parts of 5 - hentriacontylresorcinol, 25 parts of acetone, and 5 parts of water into a three - necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit. Stir evenly. After heating to 70 °C, add 12 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer; add 5 parts of trimethylolpropane, react at 65 °C for 2 h, add 3 parts of modified sodium alginate and 8 parts of 2 - hydroxyethyl methacrylate, continue to stir and react until the content of isocyanate groups no longer decreases, stop the reaction, and remove the solvent by rotary evaporation to obtain polyurethane acrylate;

[0025] S3: Dissolve 2 - hydroxyethyl methacrylate in acetone, add isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine, stir evenly, and stir and react at 55 °C until the content of isocyanate groups no longer decreases, then remove the solvent to obtain an ultraviolet - resistant agent; the molar ratio of 2 - hydroxyethyl methacrylate, isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine is 1:2.2:0.8:1;

[0026] S4: Take 32 parts of polyurethane acrylate, 12 parts of ultraviolet - resistant agent, 25 parts of styrene, 30 parts of ethyl acrylate, and 6 parts of methyl methacrylate, mix evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain an acrylic resin;

[0027] S5: Take 6 parts of metal pigment, add 20 parts of butyl acetate, and stir evenly; add 10 parts of cellulose acetate butyrate and 75 parts of acrylic resin, disperse at a rotation speed of 2000 r / min for 20 minutes, then add 0.01 part of the drying agent dibutyltin dilaurate and disperse for 20 min to obtain a multi - angle color - changing coating; coat the multi - angle color - changing coating on the surface of a road sign, with a coating thickness of 25 μm, and bake at 80 °C for 120 min to obtain a multi - angle color - changing film.

[0028] Example 2: S1: Take sodium alginate, add a mixed solvent, add 2,4 - difluorophenyl isocyanate, mix evenly, and stir and react at 55 °C until the content of isocyanate groups no longer decreases, then remove the mixed solvent to obtain modified sodium alginate; the molar ratio of sodium alginate to 2,4 - difluorophenyl isocyanate is 1:1.2;

[0029] S2: Add 15 parts of polytetrahydrofuran diol, 8 parts of 5 - hentriacontylresorcinol, 25 parts of acetone, and 5 parts of water into a three - necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit. Stir evenly. After heating to 70 °C, add 15 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer; add 6 parts of trimethylolpropane, react at 65 °C for 2 h, add 3 parts of modified sodium alginate and 10 parts of 2 - hydroxyethyl methacrylate, continue to stir and react until the content of isocyanate groups no longer decreases, stop the reaction, and remove the solvent by rotary evaporation to obtain polyurethane acrylate;

[0030] S3: Dissolve 2 - hydroxyethyl methacrylate in acetone, add isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine, stir evenly, and stir and react at 55 °C until the content of isocyanate groups no longer decreases, then remove the solvent to obtain an ultraviolet - resistant agent; the molar ratio of 2 - hydroxyethyl methacrylate, isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine is 1:2.2:1:0.8;

[0031] S4: Take 35 parts of polyurethane acrylate, 10 parts of ultraviolet - resistant agent, 20 parts of styrene, 35 parts of ethyl acrylate, and 5 parts of methyl methacrylate, mix evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain an acrylic resin;

[0032] S5: Take 8 parts of metallic pigment, add 20 parts of butyl acetate, and stir evenly; add 12 parts of cellulose acetate butyrate and 80 parts of acrylic resin, disperse at a rotation speed of 2000 r / min for 20 minutes, then add 0.01 part of the drying agent dibutyltin dilaurate and disperse for 20 min to obtain a multi - angle color - changing coating; coat the multi - angle color - changing coating on the surface of a road sign, with a coating thickness of 25 μm, and bake at 80 °C for 120 min to obtain a multi - angle color - changing film.

[0033] Example 3: S1: Take sodium alginate, add a mixed solvent, add 2,4 - difluorophenyl isocyanate, mix evenly, and stir and react at 55 °C until the content of isocyanate groups no longer decreases, then remove the mixed solvent to obtain modified sodium alginate; the molar ratio of sodium alginate to 2,4 - difluorophenyl isocyanate is 1:1;

[0034] S2: Add 10 parts of polytetrahydrofuran diol, 5 parts of 5 - hentriacontylresorcinol, 25 parts of acetone, and 5 parts of water into a three - necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit. Stir evenly. After heating to 70 °C, add 10 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer; add 6 parts of trimethylolpropane, react at 65 °C for 2 h, add 2 parts of modified sodium alginate and 6 parts of 2 - hydroxyethyl methacrylate, continue stirring and reacting until the content of isocyanate groups no longer decreases, stop the reaction, and remove the solvent by rotary evaporation to obtain polyurethane acrylate;

[0035] S3: Dissolve 2 - hydroxyethyl methacrylate in acetone, add isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine, stir evenly, and stir and react at 55 °C until the content of isocyanate groups no longer decreases, then remove the solvent to obtain an ultraviolet - resistant agent; the molar ratio of 2 - hydroxyethyl methacrylate, isophorone diisocyanate, 4,4' - dihydroxybenzophenone, and 2,2,6,6 - tetramethylpiperidineamine is 1:2:0.8:0.8;

[0036] S4: Take 30 parts of polyurethane acrylate, 10 parts of ultraviolet - resistant agent, 20 parts of styrene, 30 parts of ethyl acrylate, and 5 parts of methyl methacrylate, mix evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain an acrylic resin;

[0037] S5: Take 5 parts of metal pigment, add 15 parts of butyl acetate, and stir evenly; add 8 parts of cellulose acetate butyrate and 70 parts of acrylic resin, disperse at a rotation speed of 2000 r / min for 20 minutes, then add 0.01 part of drier dibutyltin dilaurate and disperse for 20 min to obtain a multi - angle color - changing coating; coat the multi - angle color - changing coating on the surface of a road sign, with a coating thickness of 25 μm, and bake at 80 °C for 120 min to obtain a multi - angle color - changing film.

[0038] Comparative Example 1 (without introducing modified sodium alginate, and the other method steps are the same as those in Example 1): S1: Add 12 parts of polytetrahydrofuran diol, 6 parts of 5 - hentriacontylresorcinol, 25 parts of acetone, and 5 parts of water into a three - necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit. Stir evenly. After heating to 70 °C, add 12 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer; add 5 parts of trimethylolpropane, react at 65 °C for 2 h, add 11 parts of 2 - hydroxyethyl methacrylate, continue stirring and reacting until the content of isocyanate groups no longer decreases, stop the reaction, and remove the solvent by rotary evaporation to obtain polyurethane acrylate;

[0039] S2: Dissolve hydroxyethyl methacrylate in acetone, add isophorone diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine, stir evenly, and react with stirring at 55 °C until the isocyanate group content no longer decreases. Remove the solvent to obtain an ultraviolet protection agent; the molar ratio of hydroxyethyl methacrylate, isophorone diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine is 1:2.2:0.8:1;

[0040] S3: Take 32 parts of polyurethane acrylate, 12 parts of ultraviolet protection agent, 25 parts of styrene, 30 parts of ethyl acrylate, and 6 parts of methyl methacrylate, mix evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain an acrylic resin;

[0041] S4: Take 6 parts of metal pigment, add 20 parts of butyl acetate, and stir evenly; add 10 parts of cellulose acetate butyrate and 75 parts of acrylic resin, and disperse at a rotation speed of 2000 r / min for 20 minutes. Then add 0.01 part of drier dibutyltin dilaurate and disperse for 20 min to obtain a multi-angle color-changing coating; coat the multi-angle color-changing coating on the surface of the road sign, with a coating thickness of 25 μm, and bake at 80 °C for 120 min to obtain a multi-angle color-changing film.

[0042] Comparative Example 2 (without introducing trimethylolpropane, and the rest of the method steps are the same as in Example 1): S1: Take sodium alginate, add a mixed solvent, add 2,4-difluorophenyl isocyanate, mix evenly, and react with stirring at 55 °C until the isocyanate group content no longer decreases. Remove the mixed solvent to obtain modified sodium alginate; the molar ratio of sodium alginate to 2,4-difluorophenyl isocyanate is 1:1;

[0043] S2: Add 12 parts of polytetrahydrofuran diol, 6 parts of 5-heneicosylresorcinol, 25 parts of acetone, and 5 parts of water into a three-necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit, stir evenly, heat up to 70 °C, then add 12 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, stir and react for 4 h, add 3 parts of modified sodium alginate and 8 parts of hydroxyethyl methacrylate, continue to stir and react until the isocyanate group content no longer decreases, stop the reaction, and remove the solvent by rotary evaporation to obtain polyurethane acrylate;

[0044] S3: Dissolve hydroxyethyl methacrylate in acetone, add isophorone diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine, stir evenly, and react with stirring at 55 °C until the isocyanate group content no longer decreases. Remove the solvent to obtain an ultraviolet protection agent; the molar ratio of hydroxyethyl methacrylate, isophorone diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine is 1:2.2:0.8:1;

[0045] S4: Take 32 parts of polyurethane acrylate, 12 parts of ultraviolet inhibitor, 25 parts of styrene, 30 parts of ethyl acrylate, and 6 parts of methyl methacrylate. Mix them evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain acrylic resin.

[0046] S5: Take 6 parts of metallic pigment, add 20 parts of butyl acetate, and stir evenly. Add 10 parts of cellulose acetate butyrate and 75 parts of acrylic resin, and disperse at a rotation speed of 2000 r / min for 20 minutes. Then add 0.01 part of drying agent dibutyltin dilaurate and disperse for 20 min to obtain a multi-angle color-changing coating. Coat the multi-angle color-changing coating on the surface of the road sign with a coating thickness of 25 μm, and bake at 80 °C for 120 min to obtain a multi-angle color-changing film.

[0047] Comparative Example 3 (using 4,4'-dihydroxybenzophenone and 2,2,6,6-tetramethylpiperidineamine as ultraviolet inhibitors and adding them directly, and the remaining method steps are the same as those in Example 1): S1: Take sodium alginate, add a mixed solvent, add 2,4-difluorophenyl isocyanate, mix evenly, and stir and react at 55 °C until the isocyanate group content no longer decreases. Remove the mixed solvent to obtain modified sodium alginate. The molar ratio of sodium alginate to 2,4-difluorophenyl isocyanate is 1:1.

[0048] S2: Add 12 parts of polytetrahydrofuran diol, 6 parts of 5-heneicosylresorcinol, 25 parts of acetone, and 5 parts of water into a three-necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit, and stir evenly. After heating to 70 °C, add 12 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer. Add 5 parts of trimethylolpropane, react at 65 °C for 2 h, add 3 parts of modified sodium alginate and 8 parts of 2-hydroxyethyl methacrylate, and continue to stir and react until the isocyanate group content no longer decreases, then stop the reaction. Rotate and evaporate to remove the solvent to obtain polyurethane acrylate.

[0049] S3: Take 0.8:1 part of 4,4'-dihydroxybenzophenone and 2,2,6,6-tetramethylpiperidineamine in molar ratio, and mix them to obtain an ultraviolet inhibitor.

[0050] S4: Take 32 parts of polyurethane acrylate, 12 parts of ultraviolet inhibitor, 25 parts of styrene, 30 parts of ethyl acrylate, and 6 parts of methyl methacrylate. Mix them evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain acrylic resin.

[0051] S5: Take 6 parts of metallic pigment, add 20 parts of butyl acetate, and stir evenly; add 10 parts of cellulose acetate butyrate and 75 parts of acrylic resin, and disperse for 20 minutes at a rotation speed of 2000 r / min. Then add 0.01 part of the drying agent dibutyltin dilaurate and disperse for 20 min to obtain the multi-angle color-changing coating; coat the multi-angle color-changing coating on the surface of the road sign with a coating thickness of 25 μm and bake at 80 °C for 120 min to obtain the multi-angle color-changing film.

[0052] Comparative Example 4 (using modified polyurethane acrylate to replace polyurethane acrylate and ultraviolet absorber, and the remaining method steps are the same as those in Example 1): S1: Take sodium alginate, add a mixed solvent, add 2,4-difluorophenyl isocyanate, and mix evenly. Stir and react at 55 °C until the isocyanate group content no longer decreases, and remove the mixed solvent to obtain modified sodium alginate; the molar ratio of sodium alginate to 2,4-difluorophenyl isocyanate is 1:1;

[0053] S2: Add 10 parts of polytetrahydrofuran diol, 5 parts of 5 - hentriacontylresorcinol, 3 parts of 4,4'-dihydroxybenzophenone, 25 parts of acetone, and 5 parts of water into a three-necked flask equipped with a polytetrafluoroethylene stir bar, a condenser, and a nitrogen conduit, and stir evenly. After heating to 70 °C, add 12 parts of isophorone diisocyanate and 0.6 part of dibutyltin dilaurate, and stir and react for 2 h to obtain a prepolymer; add 5 parts of trimethylolpropane, react at 65 °C for 2 h, add 3 parts of modified sodium alginate, 5 parts of 2-hydroxyethyl methacrylate, and 3 parts of 2,2,6,6-tetramethylpiperidineamine, and continue to stir and react until the isocyanate group content no longer decreases, then stop the reaction, and remove the solvent by rotary evaporation to obtain modified polyurethane acrylate;

[0054] S3: Take 44 parts of modified polyurethane acrylate, 25 parts of styrene, 30 parts of ethyl acrylate, and 6 parts of methyl methacrylate, mix evenly, add 1.5 parts of benzoyl peroxide, and react at 80 °C for 6 h to obtain acrylic resin;

[0055] S4: Take 6 parts of metallic pigment, add 20 parts of butyl acetate, and stir evenly; add 10 parts of cellulose acetate butyrate and 75 parts of acrylic resin, and disperse for 20 minutes at a rotation speed of 2000 r / min. Then add 0.01 part of the drying agent dibutyltin dilaurate and disperse for 20 min to obtain the multi-angle color-changing coating; coat the multi-angle color-changing coating on the surface of the road sign with a coating thickness of 25 μm and bake at 80 °C for 120 min to obtain the multi-angle color-changing film.

[0056] In the above embodiments, unless otherwise specified, the test methods used are all conventional methods; unless otherwise specified, the raw materials used can all be obtained through commercial channels, and the raw material sources are as follows: acetone (CAS: 67-64-1); 2,4-difluorophenyl isocyanate (S48727, Yuanye Bio-Technology Co., Ltd., Shanghai); sodium alginate (S11053, Yuanye Bio-Technology Co., Ltd., Shanghai); polytetrahydrofuran diol (PTMG-1000, Shandong Suihua Biotechnology Co., Ltd.); 5-heneicosylresorcinol (B32973, Yuanye Bio-Technology Co., Ltd., Shanghai); isophorone diisocyanate (CAS: 4098-71-9); dibutyltin dilaurate (CAS: 77-58-7); trimethylolpropane (CAS: 77-99-6); 2-hydroxyethyl methacrylate (CAS: 868-77-9); 4,4'-dihydroxybenzophenone (CAS: 611-99-4); 2,2,6,6-tetramethylpiperidinamine (CAS: 36768-62-4); styrene (CAS: 100-42-5); ethyl acrylate (CAS: 140-88-5); methyl methacrylate (CAS: 80-62-6); benzoyl peroxide (CAS: 94-36-0); metallic pigments (Merck colorstream series, Autumn Mystery); butyl acetate (CAS: 123-86-4); cellulose acetate butyrate (CAS: 9004-36-8).

[0057] Experiment: Take the multi-angle color-changing coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 4, coat them on a mold with a coating thickness of 25 μm to obtain a sample film; (1) Refer to GBT14522-2008, conduct artificial accelerated aging for 1000 h, and test the gloss retention rate; (2) Refer to GB / T1768-2006, test the abrasion resistance; (3) Use a contact angle measuring instrument to measure the water contact angle; the specific data are shown in the following table;

[0058]

[0059] Conclusion: In Comparative Example 1, modified sodium alginate was not introduced, resulting in a performance decline; in Comparative Example 2, trimethylolpropane was not introduced, reducing the polyurethane acrylate branched structure, and the performance was inferior to that of the examples; in Comparative Example 3, 4,4'-dihydroxybenzophenone and 2,2,6,6-tetramethylpiperidinamine were directly added as ultraviolet absorbers. Due to their small molecular weights, there were problems of uneven dispersion or migration, leading to a performance decline; in Comparative Example 4, modified polyurethane acrylate was used instead of polyurethane acrylate and ultraviolet absorber. Due to problems such as grafting rate and steric hindrance, the performance was inferior to that of the examples; in summary, the multi-angle color-changing film for road signs prepared by the present invention has good weather resistance, good abrasion resistance, and good hydrophobic and anti-fouling properties.

[0060] Finally, it should be noted that the above are only the preferred embodiments of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application, within the spirit and principle of the present invention, should be covered by the protection scope of this application; without conflict, the implementation manners of this application and the features in the implementation manners can be combined with each other. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

1. A process for preparing a multi-angle color-changing film for a road sign, characterized in that: The following steps are involved: S1: dissolving hydroxyethyl methacrylate in a solvent, adding diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine, stirring and reacting until the isocyanate content no longer decreases, and removing the solvent to obtain a UV protector; S2: Take polyurethane acrylate, UV protection agent, styrene, ethyl acrylate, and methyl methacrylate, mix them evenly, add benzoyl peroxide, react and polymerize to obtain acrylic resin; S3: adding metallic pigment to butyl acetate and stirring evenly; adding metallic pigment directing agent and acrylic resin, dispersing evenly, and then adding drying agent, dispersing evenly, to obtain multi-angle color-changing paint; applying the multi-angle color-changing paint to the surface of the road sign, drying, to obtain a multi-angle color-changing film; In the anti-ultraviolet agent, the molar ratio of hydroxyethyl methacrylate, diisocyanate, 4,4'-dihydroxybenzophenone, and 2,2,6,6-tetramethylpiperidinamine is 1:(2-2.2):(0.8-1):(0.8-1); The acrylic resin comprises the following raw materials, calculated by weight: 30-35 parts of polyurethane acrylate, 10-15 parts of UV protection agent, 20-25 parts of styrene, 30-35 parts of ethyl acrylate, 5-8 parts of methyl methacrylate, and 1.5-2 parts of benzoyl peroxide; The multi-angle color-changing paint comprises the following raw materials, calculated by weight: 5 to 8 parts of metallic pigment, 15 to 20 parts of butyl acetate, 8 to 12 parts of metallic pigment directing agent, 70 to 80 parts of acrylic resin, and 0.01 to 0.02 parts of drying agent; The preparation of the polyurethane acrylate comprises the following steps: taking polytetrahydrofuran diol, 5-henedecylresorcinol, acetone and water, stirring evenly, heating, adding diisocyanate and dibutyltin dilaurate, stirring and reacting to obtain a prepolymer; adding trimethylolpropane, reacting at 60-65° C. for 1-2 hours, adding modified sodium alginate and hydroxyethyl methacrylate, continuing to stir and react until the content of isocyanate no longer decreases, and removing the solvent by rotary evaporation to obtain polyurethane acrylate; The polyurethane acrylate comprises the following raw materials, calculated by weight: 10-15 parts of polytetramethylene glycol, 5-8 parts of 5-henedecylresorcinol, 20-25 parts of acetone, 5-8 parts of water, 10-15 parts of diisocyanate, 0.5-0.8 parts of dibutyltin dilaurate, 5-6 parts of trimethylolpropane, 2-3 parts of modified sodium alginate, and 6-10 parts of hydroxyethyl methacrylate; The preparation of the modified sodium alginate comprises the following steps: taking sodium alginate, adding a mixed solvent, adding 2,4-difluorophenyl isocyanate, mixing evenly, stirring to react until the isocyanate content no longer decreases, and removing the mixed solvent to obtain the modified sodium alginate; the molar ratio of the sodium alginate to the 2,4-difluorophenyl isocyanate is 1: (1-1.2); The coating thickness of the multi-angle color-changing coating is 20-30 μm.

2. The process for preparing a multi-angle color-changing film for a road sign according to claim 1, characterized in that: The specific drying process is: baking at 75-80°C for 110-120 minutes.

3. A multi-angle color-changing film obtained according to the preparation process of a multi-angle color-changing film for road signs according to any one of claims 1 to 2.

Images