Preparation method of polyurethane surface coating material capable of rapid label removal

Abstract

A method for preparing a polyurethane topcoat material that can be quickly delabeled is characterized in that, with polycarbonate diol (PCDL) and isophorone diisocyanate (IPDI) in a mass ratio of 1:10 to 1:30 as raw materials, under the action of a composite catalyst bismuth neodecanoate and zinc gluconate, an adhesive dimethylolpropionic acid (DMPA) in a mass ratio of 1:1 to 1:10, a chain extender 1,4-butanediol (BDO) in a mass ratio of 1:10 to 1:10, a crosslinking modifier trimethylolpropane (TMP) in a mass ratio of 1:10 to 1:50, and a neutralizer triethylamine (TEA) in a mass ratio of 1:10 to 1:50 are added to prepare a polycarbonate-type waterborne polyurethane dispersion with a crosslinked network structure, wherein the dispersion solid content is 30 to 40%. A defoamer, a wetting agent, a leveling agent, and an extender are added to the dispersion to obtain a waterborne polyurethane topcoat material that can be quickly delabeled, and the delabeling time is less than 180 seconds. Compared with the prior art, the present invention has the following characteristics: excellent rapid label removal performance, excellent wear resistance, weather resistance and chemical stability, is suitable for a variety of substrate surfaces, and will not cause damage to the substrate surface after rapid label removal.

Description

Technical Field

[0001] The present invention relates to the technical field of water-based coatings, specifically to a method for preparing a polycarbonate-type water-based polyurethane dispersion having a cross-linked network structure, using polycarbonate diol (PCDL) and isophorone diisocyanate (IPDI) as raw materials, 1,4-butanediol (BDO) as a chain extender, and trimethylolpropane (TMP) as a cross-linking modifier, thereby preparing a polycarbonate-type water-based polyurethane dispersion having a cross-linked network structure, and further preparing a polyurethane topcoat material that can be quickly removed from the coating. Background Art

[0002] Polyurethane coatings are widely used in applications such as construction, automotive, furniture, and electronics due to their excellent wear resistance, weather resistance, and chemical stability. However, existing polyurethane topcoats on the market present significant challenges in removing signs and labels. This is primarily due to the high adhesion and durability of polyurethane coatings, which make it difficult to quickly remove labels and logos without damaging the coating. Traditional label removal methods, such as mechanical scraping and the use of solvents, are often time-consuming and labor-intensive, and can easily damage the substrate, failing to meet the demand for fast, efficient, and non-destructive label removal.

[0003] Prior art has improved label release performance by adding release agents to coatings. For example, silicone and fluoride release agents have been shown to reduce the adhesion between the coating and the label to a certain extent. However, this approach suffers from imprecise control of the release agent dosage, which leads to a decrease in the coating's mechanical properties and weather resistance. Many release agents gradually lose their effectiveness over long-term use, resulting in a short-lived label release effect. Furthermore, existing release agent systems exhibit significant variations in their effectiveness on different substrates, making it impossible to guarantee consistent label release performance.

[0004] Waterborne polyurethane is an environmentally friendly coating with advantages such as low volatile organic compound (VOC) emissions, excellent mechanical properties, ease of modification, and safety and reliability. Polycarbonate-based waterborne polyurethane has become an ideal choice for high-performance coatings due to its excellent chemical resistance, weather resistance, and flexibility. However, there is an urgent need to develop a waterborne polyurethane topcoat material that can quickly remove labels to meet market demand for fast, efficient, non-destructive, safe, and environmentally friendly label removal. Summary of the Invention

[0005] The purpose of the present invention is to prepare a polyurethane topcoat material that can quickly remove labels, replace traditional solvent-based label topcoat materials, and solve the problems of the prior art such as long label removal time, poor effect, and easy damage to the substrate.

[0006] Based on the above, the present invention relates to a method for preparing a polyurethane topcoat material that can be quickly removed from the label. The method is characterized in that polycarbonate diol (PCDL) and isophorone diisocyanate (IPDI) are used as raw materials, and under the catalysis of a composite catalyst of bismuth neodecanoate and zinc gluconate, dimethylolpropionic acid (DMPA) is used as an adhesive, 1,4-butanediol (BDO) is used as a chain extender, trimethylolpropane (TMP) is used as a cross-linking modifier, and triethylamine (TEA) is used as a neutralizer to prepare a polycarbonate-type waterborne polyurethane dispersion having a cross-linked network structure; a defoamer, a wetting agent, a leveling agent, and an extender are added to the dispersion and treated to obtain a waterborne polyurethane topcoat material that can be quickly removed from the label.

[0007] The preparation method of the polycarbonate type waterborne polyurethane dispersion with a cross-linked network structure is as follows: after vacuum dehydrating PCDL at 100° C. and -0.095 MPa for 2 hours, cooling to 80° C., adding isophorone diisocyanate (IPDI) at a mass ratio of 1:10 to 1:50, adding a composite catalyst of bismuth neodecanoate and zinc gluconate at a mass ratio of 1:20 to 1:1000 to PCDL, stirring and reacting at 80° C. for 2 to 5 hours; adding dimethylolpropionic acid (DMPA) at a mass ratio of 1:1 to 1:10 to PCDL, stirring and reacting at 80° C. for 1 to 3 hours; cooling the reaction mixture to 40° C., adding bismuth neodecanoate at a mass ratio of 1:1 to 1:10 to PCDL, stirring and reacting at 80° C. for 1 to 3 hours; The reaction mixture is diluted with 1:10 acetone, 1,4-butanediol (BDO) as a chain extender is added at a ratio of 1:1 to 1:10 to PCDL by mass, and the temperature is raised to 60-80° C. for reaction for 2-4 hours. After the reaction, trimethylolpropane (TMP) as a crosslinker is added at a ratio of 1:10 to 1:50 to PCDL by mass and the reaction is carried out at 40-80° C. for 1-3 hours. Triethylamine (TEA) is then added at a ratio of 1:10 to 1:50 to PCDL by mass and the reaction is carried out at 35° C. for 0.5-1 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 30-40%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:1 to 1:4.

[0008] The preparation method of the water-based polyurethane topcoat material capable of rapid label removal comprises the following steps: at room temperature, while stirring an aqueous polyurethane dispersion at a stirring speed of 1000 rpm, sequentially adding a defoaming agent polyoxyethylene ether with a relative average molecular weight of 1500 at a mass ratio of 1:100 to 1:1000 to the aqueous polyurethane dispersion, a wetting agent polyethylene glycol monoacrylate with a relative average molecular weight of 1200 at a mass ratio of 1:100 to 1:500, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:500 to 1:1000, and stirring for reaction for 0.3 to 1 hour; finally, adding a post-chain extender ethylenediamine (EDA) with a mass ratio of 1:500 to 1:1000 to the aqueous polyurethane dispersion, and continuing to stir and react for 0.5 to 2 hours to prepare the polyurethane topcoat material capable of rapid label removal.

[0009] The present invention solves this technical problem through the following technical solutions:

[0010] The specific technical solution is illustrated by taking a polyurethane topcoat material prepared with a mass ratio of polycarbonate diol (PCDL) and isophorone diisocyanate (IPDI) of 1:20 as an example.

[0011] 1 part of PCDL was vacuum dehydrated at 100°C and -0.095MPa for 2h, then cooled to 80°C, 20 parts of isophorone diisocyanate (IPDI) were added, and a composite catalyst of bismuth neodecanoate and zinc gluconate in a mass ratio of 1:20 to PCDL was added, and stirred at 80°C for 2h; dimethylolpropionic acid (DMPA) in a mass ratio of 1:1 to PCDL was added and stirred at 80°C for 2h; the reaction mixture was cooled to 40°C, acetone in a mass ratio of 1:1 to PCDL was added to dilute the reaction mixture, and the reaction mixture was added. A chain extender, 1,4-butanediol (BDO), was added at a mass ratio of 1:1 to PCDL, and the temperature was raised to 80°C for reaction for 2 hours. After the reaction, a crosslinker, trimethylolpropane (TMP), was added at a mass ratio of 1:10 to PCDL and the reaction was carried out at 50°C for 2 hours. Then, triethylamine (TEA) was added at a mass ratio of 1:10 to PCDL and the reaction was carried out at 35°C for 0.5 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 35%. The mass ratio of the composite catalyst, bismuth neodecanoate and zinc gluconate, was 1:4.

[0012] At room temperature, 100 parts of the polyurethane dispersion prepared above were stirred at a speed of 1000 rpm, and 1 part of a defoaming agent polyoxyethylene ether with a relative average molecular weight of 1500, 1 part of a wetting agent polyethylene glycol monoacrylate with a relative average molecular weight of 1200, and 0.2 parts of a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 were added in sequence. The mixture was stirred for 0.5 h, and finally 0.2 parts of a post-chain extender ethylenediamine (EDA) was added and the stirring reaction was continued for 0.5 h to obtain a polyurethane topcoat material that can be quickly removed from the label.

[0013] Compared with the existing method, the present invention is characterized in that: the method prepares a cross-linked modified polycarbonate type water-based polyurethane dispersion, and the polyurethane topcoat material prepared thereby accelerates the reaction and dissolution while quickly permeating alkaline water, has a fast label removal performance, and the label removal time is less than 180 seconds. Specific implementation methods

[0014] The method of the present invention is further described below with reference to the embodiments, which are not intended to limit the present invention.

[0015] Example 1: PCDL was vacuum dehydrated at 100°C and -0.095MPa for 2h, then cooled to 80°C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:10, and a composite catalyst of bismuth neodecanoate and zinc gluconate at a mass ratio of 1:20 to PCDL was added, and stirred at 80°C for 2h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:1 to PCDL, and stirred at 80°C for 1h; the reaction mixture was cooled to 40°C, and acetone was added at a mass ratio of 1:1 to PCDL to dilute the reaction mixture. The mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:1 to PCDL, and then the temperature is raised to 60°C for reaction for 2 hours. After the reaction, trimethylolpropane (TMP) is added as a crosslinker at a mass ratio of 1:10 to PCDL and the mixture is reacted at 40°C for 1.0 hour. Triethylamine (TEA) is then added at a mass ratio of 1:10 to PCDL and the mixture is reacted at 40°C for 0.5 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 30%; the mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:1.

[0016] At room temperature, the above-prepared aqueous polyurethane dispersion was stirred at a speed of 1000 rpm, and the following were added in sequence: a defoaming agent polyoxyethylene ether with a mass ratio of 1:100 to the aqueous polyurethane dispersion and a relative average molecular weight of 1500, a wetting agent polyethylene glycol monoacrylate with a mass ratio of 1:100 and a relative average molecular weight of 1200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a mass ratio of 1:500 and a relative average molecular weight of 1050. The mixture was stirred for 20 minutes, and finally, a post-chain extender ethylenediamine (EDA) with a mass ratio of 1:500 to the aqueous polyurethane dispersion was added and the stirring reaction was continued for 0.5 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 179 seconds.

[0017] Comparative Example 1: Neopentyl glycol, trimellitic anhydride, and dimethylolpropionic acid (DMPA) were added to a reactor, CO2 gas was introduced, the temperature was raised to 120°C, tetraisopropyl titanate was added, the temperature was stirred and the temperature was raised to 180°C, and the reaction was continued for 2 hours. The acid value was tested every 30 minutes until it reached 79 mgKOH / g and the hydroxyl value reached 79.5. The temperature was lowered to 130°C and xylene was added. The temperature was raised to 150°C and refluxed for dehydration. After the xylene was completely removed, the xylene was vacuum-cycled and recovered. The temperature was lowered to 80°C and acetone was added for dilution. The temperature was kept at 60°C. TDI was added dropwise for 1.5 hours. After the dropwise addition, 10% phosphoric acid (toluene) solution was stirred. The temperature was raised to 70°C for reaction. After 4 hours, the free TDI is tested to be less than 0.2%. 50% phenol (toluene) solution is added and the temperature is raised to 80°C for reaction for 15 minutes, then the temperature is raised to 90°C, 1 / 2 of the acetone fed is distilled out, and the mixture is kept warm at 70°C for standby use. In another reactor equipped with rapid stirring, N-toluenediethanolamine, triethylamine, ethylenediamine, and deionized water are added and the rapid stirring is started. The above-mentioned materials kept warm at 70°C are slowly added to the reactor, and the neutralization reaction is carried out at 60°C until transparent, then the temperature is raised to 70°C, the vacuum is applied to reduce the pressure, all the remaining acetone is distilled out, the temperature is lowered to 40°C, filtered, and the material is discharged to obtain a water-based polyurethane topcoat material with a de-labeling time of 235s.

[0018] Comparative Example 2: Adipic acid, trimellitic anhydride, and dimethylolpropionic acid (DMPA) were added to a reactor, CO2 gas was introduced, the temperature was raised to 120°C, isophorone diisocyanate was added, the temperature was stirred and the temperature was raised to 180°C, and the reaction was continued for 2 hours. The acid value was tested every 30 minutes until it reached 79 mgKOH / g and the hydroxyl value reached 79.5. The temperature was lowered to 130°C and xylene was added. The temperature was raised to 150°C and refluxed for dehydration. After dehydration, the xylene was vacuumed and recovered. The temperature was lowered to 80°C and acetone was added for dilution. The mixture was kept warm at 60°C. TDI was added dropwise for 1.5 hours. After the dropwise addition, 10% phosphoric acid (toluene) solution was stirred and the temperature was raised to 70°C. After 5 hours of reaction, the free TDI was tested to be less than 0.2%. 50% phenol (toluene) solution was added and the temperature was raised to 80°C for reaction for 15 minutes, then the temperature was raised to 90°C, 1 / 2 of the acetone was distilled out, and the mixture was kept warm at 70°C for later use. In another reactor equipped with rapid stirring, N-toluenediethanolamine, triethylamine, ethylenediamine, and deionized water were added and rapid stirring was started. The above materials kept warm at 70°C were slowly added to the reactor, and after neutralization reaction at 60°C and transparency, the temperature was raised to 70°C, vacuumed and reduced in pressure, all the remaining acetone was distilled out, and the temperature was lowered to 40°C. The mixture was filtered and discharged to obtain a water-based polyurethane topcoat material with a de-labeling time of 208s.

[0019] Example 2: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:30. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:20 to PCDL, and the mixture was stirred at 80 ° C for 3.5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:1 to PCDL and stirred at 80 ° C for 2 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:1 to PCDL to dilute the mixture. The mixture was added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:1 to PCDL, and the temperature was raised to 60° C. for reaction for 3 hours. After the reaction, trimethylolpropane (TMP) was added at a mass ratio of 1:10 to PCDL as a crosslinker and the mixture was reacted at 40° C. for 2 hours. Triethylamine (TEA) was then added at a mass ratio of 1:10 to PCDL and the mixture was reacted at 35° C. for 0.5 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 33%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate was 1:2.

[0020] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:100 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a mass ratio of 1:200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:800 were added in sequence, and the mixture was stirred for 20 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:800 to the aqueous polyurethane dispersion and the stirring reaction was continued for 0.5 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 176 seconds.

[0021] Example 3: PCDL was vacuum dehydrated at 100°C and -0.095MPa for 2h, then cooled to 80°C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:50. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:20 to PCDL, and stirred at 80°C for 5h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:1 to PCDL and stirred at 80°C for 3h; the reaction mixture was cooled to 40°C, and acetone was added at a mass ratio of 1:1 to PCDL to dilute the reaction mixture. The mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:1 to PCDL, and then the temperature is raised to 60°C for reaction for 4 hours. After the reaction, trimethylolpropane (TMP) is added at a mass ratio of 1:10 to PCDL as a crosslinker and the mixture is reacted at 45°C for 3 hours. Triethylamine (TEA) is then added at a mass ratio of 1:10 to PCDL and the mixture is reacted at 35°C for 0.6 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 35%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:3.

[0022] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:300 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a mass ratio of 1:300, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:900 were added in sequence, and the mixture was stirred for 30 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:900 to the aqueous polyurethane dispersion and the stirring reaction was continued for 0.5 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 172 seconds.

[0023] Example 4: PCDL was vacuum dehydrated at 100°C and -0.095MPa for 2h, then cooled to 80°C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:10. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:20 to PCDL, and stirred at 80°C for 2h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:1 to PCDL and stirred at 80°C for 2h; the reaction mixture was cooled to 40°C, and acetone was added at a mass ratio of 1:1 to PCDL to dilute the reaction mixture. The mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:1 to PCDL, and then the temperature is raised to 60°C for reaction for 4 hours. After the reaction, trimethylolpropane (TMP) is added at a mass ratio of 1:10 to PCDL as a crosslinker and the mixture is reacted at 45°C for 1 hour. Triethylamine (TEA) is then added at a mass ratio of 1:10 to PCDL and the mixture is reacted at 35°C for 0.6 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 36%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:4.

[0024] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:300 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a ratio of 1:500, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a ratio of 1:1000 were added in sequence, and the mixture was stirred for 30 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:1000 to the aqueous polyurethane dispersion and the stirring reaction was continued for 0.8 hours to obtain a polyurethane topcoat material that can be quickly removed, and the removal time was 176 seconds.

[0025] Example 5: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:30. Then, a composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:500 to PCDL, and the mixture was stirred at 80 ° C for 3.5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:5 to PCDL and stirred at 80 ° C for 2 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:5 to PCDL to dilute the mixture. The reaction mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:5 to PCDL, and then heated to 70°C for reaction for 2 hours. After the reaction is completed, trimethylolpropane (TMP) is added as a crosslinker at a mass ratio of 1:30 to PCDL and reacted at 50°C for 2 hours. Triethylamine (TEA) is then added at a mass ratio of 1:30 to PCDL and reacted at 35°C for 0.7 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 38%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:1.

[0026] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 were added in sequence at a mass ratio of 1:500 to the aqueous polyurethane dispersion. The mixture was stirred for 40 minutes, and finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:500 to the aqueous polyurethane dispersion and the stirring reaction was continued for 0.8 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 171 seconds.

[0027] Example 6: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:50. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:500 to PCDL, and the mixture was stirred at 80 ° C for 5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:5 to PCDL and stirred at 80 ° C for 3 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:5 to PCDL to dilute the mixture. The mixture was added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:5 to PCDL, and the temperature was raised to 70°C for reaction for 3 hours. After the reaction, trimethylolpropane (TMP) was added at a mass ratio of 1:30 to PCDL as a crosslinker and the mixture was reacted at 55°C for 3 hours. Triethylamine (TEA) was then added at a mass ratio of 1:30 to PCDL and the mixture was reacted at 35°C for 0.7 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 38%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate was 1:2.

[0028] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:500 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a mass ratio of 1:200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:800 were added in sequence, and the mixture was stirred for 40 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:800 to the aqueous polyurethane dispersion and the stirring reaction was continued for 0.8 hours to obtain a polyurethane topcoat material that can be quickly removed, and the removal time was 162 seconds.

[0029] Example 7: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:10. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:500 to PCDL, and the mixture was stirred at 80 ° C for 2 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:5 to PCDL and stirred at 80 ° C for 1 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:5 to PCDL to dilute the mixture. The mixture was added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:5 to PCDL, and the temperature was raised to 70°C for reaction for 4 hours. After the reaction, trimethylolpropane (TMP) was added at a mass ratio of 1:30 to PCDL as a crosslinker and the mixture was reacted at 60°C for 1 hour. Triethylamine (TEA) was then added at a mass ratio of 1:30 to PCDL and the mixture was reacted at 60°C for 0.8 hour to finally obtain a polycarbonate-type aqueous polyurethane dispersion with a solid content of 35%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate was 1:2.

[0030] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:700 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a ratio of 1:300, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a ratio of 1:900 were added in sequence. The mixture was stirred for 45 minutes, and finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:900 to the aqueous polyurethane dispersion and the stirring reaction was continued for 1 hour to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 172 seconds.

[0031] Example 8: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:30. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:500 to PCDL, and the mixture was stirred at 80 ° C for 3.5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:5 to PCDL and stirred at 80 ° C for 2 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:5 to PCDL to dilute the mixture. The reaction mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:5 to PCDL, and then heated to 70°C for reaction for 4 hours. After the reaction is completed, trimethylolpropane (TMP) is added as a crosslinker at a mass ratio of 1:30 to PCDL and reacted at 65°C for 2 hours. Triethylamine (TEA) is then added at a mass ratio of 1:30 to PCDL and reacted at 65°C for 0.8 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 37%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:4.

[0032] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:700 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a ratio of 1:500, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a ratio of 1:1000 were added in sequence. The mixture was stirred for 45 minutes, and finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:1000 to the aqueous polyurethane dispersion and the stirring reaction was continued for 1 hour to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 167 seconds.

[0033] Example 9: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:50. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:1000 to PCDL, and the mixture was stirred at 80 ° C for 5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:10 to PCDL and stirred at 80 ° C for 3 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:10 to PCDL to dilute the mixture. The reaction mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:10 to PCDL, and then heated to 80°C for reaction for 2 hours. After the reaction, trimethylolpropane (TMP) is added at a mass ratio of 1:50 to PCDL as a crosslinker and reacted at 70°C for 3 hours. Triethylamine (TEA) is then added at a mass ratio of 1:50 to PCDL and reacted at 35°C for 0.9 hours to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 36%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:1.

[0034] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:800 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a mass ratio of 1:100, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:500 were added in sequence, and the mixture was stirred for 50 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:500 to the aqueous polyurethane dispersion and the stirring reaction was continued for 1 hour to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 158 seconds.

[0035] Example 10: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:10. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:1000 to PCDL, and the mixture was stirred at 80 ° C for 2 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:10 to PCDL and stirred at 80 ° C for 1 h; the reaction mixture was cooled to 40 ° C, and acetone was added at a mass ratio of 1:10 to PCDL to dilute the mixture. The reaction mixture is added with a chain extender 1,4-butanediol (BDO) at a mass ratio of 1:10 to PCDL, and then heated to 80°C for reaction for 3 hours. After the reaction, trimethylolpropane (TMP) is added at a mass ratio of 1:50 to PCDL as a crosslinker and reacted at 70°C for 1 hour. Triethylamine (TEA) is then added at a mass ratio of 1:50 to PCDL and reacted at 35°C for 0.9 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 35%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:2.

[0036] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500 at a mass ratio of 1:800 to the aqueous polyurethane dispersion, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200 at a mass ratio of 1:200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 at a mass ratio of 1:800 were added in sequence, and the mixture was stirred for 50 minutes. Finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:800 to the aqueous polyurethane dispersion and the stirring reaction was continued for 1.5 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 164 seconds.

[0037] Example 11: PCDL was vacuum dehydrated at 100°C and -0.095MPa for 2h, then cooled to 80°C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:30. Then, a composite catalyst of bismuth neodecanoate and zinc gluconate at a mass ratio of 1:1000 to PCDL was added, and the mixture was stirred at 80°C for 3.5h; dimethylolpropionic acid (DMPA) at a mass ratio of 1:10 to PCDL was added and stirred at 80°C for 2h; the reaction mixture was cooled to 40°C, and propane at a mass ratio of 1:10 to PCDL was added. The reaction mixture is diluted with ketone, and a chain extender 1,4-butanediol (BDO) is added at a mass ratio of 1:10 to PCDL, and the temperature is raised to 80°C for 4 hours. After the reaction is completed, a cross-linking agent trimethylolpropane (TMP) is added at a mass ratio of 1:50 to PCDL and the reaction is carried out at 75°C for 2 hours. Then, triethylamine (TEA) is added at a mass ratio of 1:50 to PCDL and the reaction is carried out at 35°C for 1 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 35%; the mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate is 1:3.

[0038] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 were added in sequence at a mass ratio of 1:1000 to the aqueous polyurethane dispersion. The mixture was stirred for reaction for 1 hour, and finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:900 to the aqueous polyurethane dispersion and the stirring reaction was continued for 1.5 hours to obtain a polyurethane topcoat material that can be quickly debonded, and the debonding time was 159 seconds.

[0039] Example 12: PCDL was vacuum dehydrated at 100 ° C and -0.095 MPa for 2 h, then cooled to 80 ° C, and isophorone diisocyanate (IPDI) was added at a mass ratio of 1:50. A composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:1000 to PCDL, and the mixture was stirred at 80 ° C for 5 h; dimethylolpropionic acid (DMPA) was added at a mass ratio of 1:10 to PCDL and stirred at 80 ° C for 3 h; the reaction mixture was cooled to 40 ° C, and acetone diluted at a mass ratio of 1:10 to PCDL was added. The reaction mixture was diluted, and a chain extender 1,4-butanediol (BDO) was added at a mass ratio of 1:10 to PCDL, and the temperature was raised to 80° C. for reaction for 4 hours. After the reaction, a cross-linking agent trimethylolpropane (TMP) was added at a mass ratio of 1:50 to PCDL and the reaction was carried out at 80° C. for 3 hours. Then, triethylamine (TEA) was added at a mass ratio of 1:50 to PCDL and the reaction was carried out at 35° C. for 1 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 36%; the mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate was 1:4.

[0040] At room temperature, the above-prepared dispersion was stirred at a speed of 1000 rpm, and a polyoxyethylene ether defoamer with a relative average molecular weight of 1500, a polyethylene glycol monoacrylate wetting agent with a relative average molecular weight of 1200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a relative average molecular weight of 1050 were added in sequence at a mass ratio of 1:1000 to the aqueous polyurethane dispersion. The mixture was stirred for 1 hour, and finally, a post-chain extender ethylenediamine (EDA) was added at a mass ratio of 1:1000 to the aqueous polyurethane dispersion and the stirring reaction was continued for 2 hours to obtain a polyurethane topcoat material that can be quickly removed, and the removal time was 154 seconds.

[0041] Label removal time test method:

[0042] 1. Take a 50×70mm sample, prepare a 20wt% casein glue aqueous solution, and evenly apply it on the back of the sample with a 3# stick, then stick it on a clean glass bottle and place it in a laboratory environment for 7 days.

[0043] 2. Prepare 0.7 wt% NaOH solution and heat to 75°C;

[0044] 3. Pour warm water into the glass bottle and immerse it in the alkali solution. Set the stirring speed to 350 rpm, press the timer to start timing, and record the time it takes for the sample to completely fall off the bottle body, which is the label removal time.

[0045] Experimental results: The results are shown in Table 1. The topcoat of the present invention has a fast label removal performance after contacting alkaline water, and the label removal time is less than 180s.

[0046] Table 1 Test results of label removal time

[0047] sample Label removal time Example 1 179s Comparative Example 1 235s Comparative Example 2 208s Example 2 176s Example 3 172s Example 4 176s Example 5 171s Example 6 162s Comparative Example 7 172s Comparative Example 8 167s Example 9 158s Example 10 164s Example 11 159s Example 12 154s

Claims

1. A method for preparing a polyurethane topcoat material capable of rapid label removal, characterized in that: Specifically include the following preparation methods: Preparation of polycarbonate-based waterborne polyurethane dispersion with cross-linked network structure After dehydrating polycarbonate diol PCDL under vacuum at 100°C and -0.095MPa for 2h, the temperature was lowered to 80°C, and isophorone diisocyanate IPDI was added at a mass ratio of 1:10-1:

50. Then, a composite catalyst of bismuth neodecanoate and zinc gluconate was added at a mass ratio of 1:20-1:1000 to PCDL, and the mixture was stirred and reacted at 80°C for 2-5h. Dimethylolpropionic acid DMPA was added at a mass ratio of 1:1-1:10 to PCDL, and the mixture was stirred and reacted at 80°C for 1-3h. After the reaction mixture was cooled to 40°C, acetone was added at a mass ratio of 1:1-1:10 to PCDL to dilute the reaction mixture. After adding the chain extender 1,4-butanediol (BDO) at a mass ratio of 1:1 to 1:10 to PCDL, the temperature was raised to 60-80°C for reaction for 2-4 hours. After the reaction, trimethylolpropane (TMP) was added at a mass ratio of 1:10 to 1:50 to PCDL as a crosslinker and the reaction was carried out at 40-80°C for 1-3 hours. Then, triethylamine (TEA) was added at a mass ratio of 1:10 to 1:50 to PCDL and the reaction was carried out at 35°C for 0.5-1 hour to finally obtain a polycarbonate-type waterborne polyurethane dispersion with a solid content of 30-40%. The mass ratio of the composite catalyst bismuth neodecanoate and zinc gluconate was 1:1 to 1:

4. Preparation of polyurethane topcoat material capable of rapid label removal At room temperature, a polycarbonate type waterborne polyurethane dispersion is stirred at a stirring speed of 1000 rpm, and a defoaming agent polyoxyethylene ether with a relative average molecular weight of 1500 at a mass ratio of 1:100-1:1000 to the waterborne polyurethane dispersion, a wetting agent polyethylene glycol monoacrylate with a mass ratio of 1:100-1:500 and a relative average molecular weight of 1200, and a leveling agent poly(dimethylsiloxane-3-hydroxypropylmethylsiloxane) polyoxyethylene polyoxypropylene ether with a mass ratio of 1:500-1:1000 and a relative average molecular weight of 1050 are added in sequence. The mixture is stirred for 0.3-1 hour. Finally, a post-chain extender ethylenediamine (EDA) is added at a mass ratio of 1:500-1:1000 to the waterborne polyurethane dispersion, and the stirring reaction is continued for 0.5-2 hours to prepare a polyurethane topcoat material that can be quickly removed.