Low-energy-consumption polyurethane powder coating and preparation method thereof

Abstract

The invention discloses a low-energy-consumption polyurethane powder coating and a preparation method thereof, and belongs to the technical field of polyurethane powder coatings. Comprising the following raw materials in parts by weight: 60-70 parts of polyester polyol, 10-20 parts of a closed HDI tripolymer, 5-10 parts of a flame retardant aid, 1-2 parts of a flatting agent, 2-3 parts of an anti-yellowing agent, 0.5-1.5 parts of a dispersing agent, 0.4-0.8 part of a degassing agent and 8-12 parts of superfine barium sulfate. The low-hydroxyl-value polyester polyol and the closed HDI tripolymer are matched for use, so that the temperature and time required in the curing process are greatly reduced, and the energy consumption is reduced; the self-made flame-retardant additive can effectively improve the flame-retardant property of the coating, reduce the fire risk and prolong the service life; in conclusion, the prepared coating achieves the dual purposes of energy conservation, environmental protection, safety and flame retardance, and has important application value in the field of polyurethane powder coatings.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polyurethane powder coatings, and particularly relates to a low-energy-consumption polyurethane powder coating and a preparation method thereof. BACKGROUND

[0002] In the broad field of the paint industry, polyurethane powder coatings have long occupied an important position in demanding applications such as high-end household appliances, building materials, automotive parts, and outdoor facilities due to their excellent comprehensive performance, such as outstanding leveling, high decoration, excellent weather resistance, chemical corrosion resistance, and mechanical properties. The film-forming and curing mechanism of traditional polyurethane powder coatings mainly relies on the hydroxyl components in the system, such as the terminal hydroxyl groups of polyester resins or acrylic resins, which crosslink with blocked isocyanate as a curing agent under heating conditions. During the baking process, the blocking agent is first unblocked to release active isocyanate groups, which then react with the hydroxyl groups of the resin to form urethane bonds, thereby constructing a three-dimensional network crosslinked coating film. Although this technical route is mature and reliable in performance, it also has some inherent and urgent bottleneck problems.

[0003] One of the most prominent challenges is the high energy consumption. Since the unblocking process of blocked isocyanate requires the absorption of a considerable amount of heat and the reaction rate is relatively slow, this directly leads to the generally high curing temperature required for such powder coatings, usually reaching 180 degrees Celsius or even above 190 degrees Celsius, and the corresponding curing time is also relatively long, generally 15 to 30 minutes. Such high-temperature and long-time curing conditions mean that the production line needs to consume a large amount of electrical energy or natural gas to maintain the temperature of the baking channel, which not only constitutes a significant part of the production cost for the production enterprise, but also often accompanies a large amount of greenhouse gas emissions during the high-energy-consumption production process, which causes serious pollution to the environment and is contrary to the current global low-carbon and environmental protection concept.

[0004] In addition to the energy consumption problem, polyurethane, as an organic polymer material, is itself flammable when exposed to a fire source. If the flame retardance of the coating is insufficient, it will be more easily ignited once it encounters an open flame or high-temperature heat source, and the flame will spread rapidly along the surface of the coating. This not only accelerates the expansion of the fire, but also greatly shortens the valuable time for on-site personnel to discover the fire and safely evacuate, posing a direct threat to life and property. Therefore, it is urgent to solve the above problems to meet the higher demands in the field of polyurethane powder coatings. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provides a low-energy-consumption polyurethane powder coating and a preparation method thereof.

[0006] The object of the present application can be achieved by the following technical solutions: A low-energy-consumption polyurethane powder coating, comprising the following raw materials by weight: 60-70 parts of polyester polyol, 10-20 parts of blocked HDI trimer, 5-10 parts of flame retardant aid, 1-2 parts of leveling agent, 2-3 parts of anti-yellowing agent, 0.5-1.5 parts of dispersing agent, 0.4-0.8 parts of degassing agent, and 8-12 parts of superfine barium sulfate.

[0007] As a further technical solution, the polyester polyol is a low-hydroxyl-value polyester polyol with a hydroxyl value < 60 mgKOH / g.

[0008] As a further technical solution, the anti-yellowing agent is a hindered amine anti-yellowing agent.

[0009] As a further technical solution, the dispersing agent is one of paraffin, calcium stearate, and zinc stearate.

[0010] As a further technical solution, the degassing agent is a benzotriazole-based degassing agent.

[0011] The present application uses a low-hydroxyl-value polyester polyol, which can provide stable hydroxyl groups and crosslink with a curing agent to form a dense coating, has good hydroxyl value matching, ensures moderate crosslinking density, and balances coating flexibility and hardness; the blocked HDI trimer has a low unblocking temperature, which can greatly reduce energy consumption during the curing stage.

[0012] As a further technical solution, the flame retardant aid is prepared by the following steps: A1, placing melamine in a double-necked flask, then adding ethanol as a solvent, opening the magnetic stirring, dispersing the melamine in the ethanol solvent, adding glycol aldehyde, heating to 70-75 DEG C, and continuously stirring at this temperature for 8-10 hours, the reaction is completed, and the product is separated by filtration and drying in an oven to obtain an aid intermediate; A2, placing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in a double-necked flask, then adding ethanol as a solvent, then placing the mixed solution containing DOPO in an ultrasonic machine for ultrasonic treatment, then heating the device to 80-85 DEG C, and opening the magnetic stirring, slowly adding the aid intermediate during stirring, continuously stirring for 10-12 hours, then rotary evaporation, then filtering, washing, and separating the obtained product to finally obtain the flame retardant aid.

[0013] As a further technical solution, the ratio of the amounts of melamine, ethanol, and glycol aldehyde in step A1 is 12.6 g:100 mL:20.3-21.7 g.

[0014] As a further technical solution, the ratio of the use amount of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanol and the intermediate of the auxiliary in step A2 is 68.7-71.5 g:100 mL:25.2 g.

[0015] The reaction formula for preparing the flame-retardant auxiliary is as follows: In the above process for preparing the flame-retardant auxiliary, the use amount of the raw materials in each step needs to be paid attention to. In step A1, the molar ratio of melamine and glycol aldehyde is controlled to be close to 1:3, and the latter is in excess, so as to form three C=N bonds (Schiff base). In step A2, DOPO reacts with the C=N bond in the intermediate of the auxiliary again, and attention also needs to be paid to controlling the molar ratio of the intermediate of the auxiliary and DOPO to be close to 1:3, and the latter is in excess, so as to ensure complete reaction.

[0016] As can be seen from the above reaction formula, the flame-retardant auxiliary prepared by the present application is constructed as a DOPO derivative, and the flame-retardant auxiliary contains N and P two kinds of flame-retardant elements at the same time, which can play a synergistic effect, can play a significant role in the condensed phase and gas phase of polymer combustion, and greatly enhances the flame-retardant performance of the matrix. Furthermore, the hydroxyl group is reserved in the process for preparing the flame-retardant auxiliary, so that the flame-retardant auxiliary can participate in the curing process of the polyurethane coating, improves the migration resistance and bleeding resistance of the small molecule flame-retardant auxiliary, and improves the service life of the flame-retardant auxiliary.

[0017] The present application also provides a preparation method of a low-energy-consumption polyurethane powder coating, which comprises the following steps: B1, drying the polyester polyol and the blocked HDI trimer in an oven to remove water to avoid the generation of bubbles during curing; B2, putting the dried polyester polyol and the blocked HDI trimer into a high-speed mixer, first stirring at low speed for 3-5 min, then sequentially adding the flame-retardant auxiliary, the leveling agent, the anti-yellowing agent, the dispersing agent and the degassing agent, stirring and mixing at medium speed for 5-10 min, finally adding the superfine barium sulfate, and stirring at high speed for 10-15 min to ensure uniform dispersion of the materials, to obtain a premix; B3, feeding the premix into a double-screw extruder, melting and blending the materials under the shearing action of the screw, extruding through the die head, pressing into a thin sheet, rapidly cooling to room temperature by cold air, and finally feeding into a pulverizer to be pulverized, to obtain the low-energy-consumption polyurethane powder coating.

[0018] As a further technical solution, the drying temperature is 80-90℃, and the time is 2-3h.

[0019] As a further technical solution, the stirring speed of the low-speed stirring is 300-500 r / min.

[0020] As a further technical solution, the rotation speed of the medium-speed stirring is 800-1000 r / min.

[0021] As a further technical solution, the rotation speed of the high-speed stirring is 1200-1500 r / min.

[0022] As a further technical solution, in the double-screw extruder, the extrusion temperature is set as follows: 90 DEG C for the first zone, 105 DEG C for the second zone, 110 DEG C for the third zone, and 108 DEG C for the die head, and the screw rotation speed is 35 r / min.

[0023] The beneficial effects of the present application are as follows: 1. The present application uses low-hydroxyl value polyester polyol in combination with blocked HDI trimer, which has a relatively low unblocking temperature, thereby greatly reducing the required temperature and time during curing and reducing energy consumption. 2. By using the self-made flame-retardant additive, N and P two flame-retardant elements are introduced to play a synergistic flame-retardant effect, effectively improve the flame-retardant performance of the coating, reduce the risk of fire, and improve the safety in use. 3. The flame-retardant additive retains hydroxyl groups during synthesis, so that it can participate in the polyurethane curing reaction to form chemical bonds, thereby improving its stability in the coating, avoiding the migration and exudation problems of small molecule flame retardants, and prolonging the service life. In summary, the coating prepared by the present application realizes the dual goals of energy saving, environmental protection and safe flame retardation, and has important application value in the field of polyurethane powder coatings. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Embodiment one Preparation of flame-retardant additive: A1, 12.6g of melamine is placed in a double-necked flask, then 100mL of ethanol is added as a solvent, magnetic stirring is started to disperse the melamine in the ethanol solvent, 20.3g of glycol aldehyde is added, heated to 70 DEG C, and stirred at this temperature for 8h, the reaction is completed, and the product is separated by filtration and drying in an oven to obtain the additive intermediate. A2, 68.7g 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is placed in a double-necked flask, then 100ml of ethanol is added as a solvent, then the mixed solution containing DOPO is placed in an ultrasonic machine for ultrasonic treatment, then the device is heated to 80°C, and magnetic stirring is started, 25.2g of the auxiliary intermediate is slowly added during stirring, after 10h of continuous stirring, rotary evaporation is performed, then the obtained product is filtered, washed and separated, and finally the flame retardant auxiliary agent is obtained; A method for preparing a low-energy-consumption polyurethane powder coating, comprising the following steps: B1, 60 parts of polyester polyol (OD-X-2108) and 10 parts of blocked HDI trimer (Trixene BI7982) are dried in an oven at 80°C for 2h to remove water and avoid bubble formation during curing; B2, the dried polyester polyol and blocked HDI trimer are placed in a high-speed mixer, first stirred at low speed (300r / min) for 3min, then 5 parts of flame retardant auxiliary agent, 1 part of leveling agent (BYK-333), 2 parts of anti-yellowing agent (Tinuvin770), 0.5 parts of dispersing agent and 0.4 parts of methyl benzotriazole are added in sequence, mixed at medium speed (800r / min) for 5min, and finally 8 parts of ultra-fine barium sulfate is added, stirred at high speed (1200r / min) for 10min to ensure uniform dispersion of the materials, and a premix is obtained; B3, the premix is sent into a double-screw extruder (set the extrusion temperature: zone 1 90°C, zone 2 105°C, zone 3 110°C, die head 108°C, screw speed 35r / min), the material is melt blended under the shearing action of the screw, extruded through the die head, pressed into a thin sheet, rapidly cooled to room temperature by cold air, and finally sent into a pulverizer for pulverization to obtain a low-energy-consumption polyurethane powder coating.

[0026] Example two Preparation of flame retardant auxiliary agent: A1, 12.6g of melamine is placed in a double-necked flask, then 100ml of ethanol is added as a solvent, magnetic stirring is started to disperse the melamine in the ethanol solvent, 21.7g of glycol aldehyde is added, heated to 75°C, and stirred at this temperature for 10h, the reaction is completed, the product is naturally cooled at room temperature, filtered and separated, and the obtained product is dried in an oven to obtain an auxiliary intermediate; A2, 71.5g 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is placed in a double-necked flask, then 100mL ethanol is added as a solvent, then the mixed solution containing DOPO is placed in an ultrasonic machine for ultrasonic treatment, then the device is heated to 85°C, and magnetic stirring is started, 25.2g of the auxiliary intermediate is slowly added during stirring, after continuous stirring for 12h, rotary evaporation is performed, then the obtained product is filtered, washed and separated, and finally a flame retardant auxiliary agent is obtained; A method for preparing a low-energy-consumption polyurethane powder coating, comprising the following steps: B1, 65 parts of polyester polyol (OD-X-2108), 15 parts of blocked HDI trimer (Trixene BI7982) are dried in an oven at 90°C for 3h to remove water to avoid bubbles during curing; B2, the dried polyester polyol and blocked HDI trimer are placed in a high-speed mixer, first stirred at low speed (500r / min) for 5min, then 7.5 parts of flame retardant auxiliary agent, 1.5 parts of leveling agent (BYK-333), 2.5 parts of anti-yellowing agent (Tinuvin770), 1.0 parts of dispersing agent and 0.6 parts of methyl benzotriazole are added in turn, mixed at medium speed (1000r / min) for 10min, then 10 parts of superfine barium sulfate is added, and high-speed stirring (1500r / min) is carried out for 15min to ensure uniform dispersion of the material, and a premix material is obtained; B3, the premix material is sent into a double-screw extruder (set the extrusion temperature: zone 1 90°C, zone 2 105°C, zone 3 110°C, die head 108°C, screw speed 35r / min), the material is melted and blended under the shearing action of the screw, extruded through the die head, pressed into a thin sheet, rapidly cooled to room temperature by cold air, and finally sent into a pulverizer for pulverization to obtain a low-energy-consumption polyurethane powder coating.

[0027] Example three The difference between this example and example two is that in this example, a method for preparing a low-energy-consumption polyurethane powder coating, comprising the following steps: B1, 65 parts of polyester polyol (OD-X-2108), 15 parts of blocked HDI trimer (Trixene BI7982) are dried in an oven at 90°C for 3h to remove water to avoid bubbles during curing; B2, the dried polyester polyol, blocked HDI trimer is put into a high-speed mixer, first low-speed stirring (500 r / min) for 5 min, then 10 parts of the flame retardant aid, 2 parts of the leveling agent (BYK-333), 3 parts of the anti-yellowing agent (Tinuvin770), 1.5 parts of the dispersing agent and 0.8 parts of the methyl benzotriazole are added in turn, and then mixed at a medium speed (1000 r / min) for 10 min, and finally 12 parts of the superfine barium sulfate is added, and high-speed stirring (1500 r / min) is carried out for 15 min to ensure uniform dispersion of the material, and a premix material is obtained; B3, the premix material is sent into a double screw extruder (the extrusion temperature is set as: 90℃ in the first zone, 105℃ in the second zone, 110℃ in the third zone, and 108℃ in the die head, and the screw speed is 35 r / min), the material is melt blended under the shearing action of the screw, extruded through the die head, pressed into a thin sheet, rapidly cooled to room temperature by cold air, and finally sent into a pulverizer for pulverization, and a low-energy-consumption polyurethane powder coating is obtained.

[0028] Comparative Example One The difference between the present comparative example and Example Five is that, in the present comparative example, an equal amount of melamine is used to replace the flame retardant aid to prepare the coating.

[0029] Comparative Example Two A commercially available powder coating, Interpon 600, is used.

[0030] Examples One, Two and Three and Comparative Examples One and Two are tested for the following properties: The lowest curing temperature is determined by differential scanning calorimetry (DSC) according to the GB / T 18593-2001 standard, and the shortest curing time is determined by combining the constant temperature baking test; The flame retardant performance of the sample is determined according to the GB / T 2408-2021 standard, and the flame retardant performance of the sample is determined again after being static for 300 days; The test results are shown in Table One: Table One As can be seen from the test results in Table One, the coating prepared in the present application has low curing conditions, high flame retardant grade and stable performance, and therefore the present application has important application value in the field of polyurethane powder coatings.

[0031] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A low energy polyurethane powder coating, characterized in that, The raw materials include the following components by weight: 60-70 parts of polyester polyol, 10-20 parts of blocked HDI trimer, 5-10 parts of flame-retardant aid, 1-2 parts of leveling agent, 2-3 parts of anti-yellowing agent, 0.5-1.5 parts of dispersing agent, 0.4-0.8 parts of degassing agent, and 8-12 parts of superfine barium sulfate.

2. A low energy polyurethane powder coating according to claim 1, characterized in that, The flame-retardant aid is prepared by the following steps: A1, placing melamine in a flask, then adding ethanol, starting stirring, dispersing melamine in the ethanol solvent, adding glycol aldehyde, heating to 70-75 DEG C, and continuously stirring for 8-10 hours until the reaction is completed to obtain an aid intermediate; A2, placing 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in a flask, then adding ethanol, ultrasonic treatment, then heating to 80-85 DEG C, and starting stirring, adding the aid intermediate during stirring, and continuously stirring for 10-12 hours to obtain the flame-retardant aid.

3. A low energy polyurethane powder coating according to claim 2, characterized in that, The ratio of the amounts of melamine, ethanol and glycol aldehyde in step A1 is 12.6 g:100 mL:20.3-21.7 g.

4. A low energy polyurethane powder coating according to claim 2, characterized in that, The ratio of the amounts of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanol and aid intermediate in step A2 is 68.7-71.5 g:100 mL:25.2 g.

5. A low energy polyurethane powder coating according to claim 1, characterized in that, The polyester polyol is a low-hydroxyl-value polyester polyol with a hydroxyl value <60 mgKOH / g.

6. A low energy polyurethane powder coating according to claim 1, characterized in that, The anti-yellowing agent is a hindered amine anti-yellowing agent.

7. A low energy polyurethane powder coating according to claim 1, characterized in that, The dispersing agent is one of paraffin, calcium stearate and zinc stearate.

8. A low energy polyurethane powder coating according to claim 1, characterized in that, The degassing agent is a benzotriazole-based degassing agent.

9. A process for the preparation of a low energy polyurethane powder coating according to any one of claims 1 to 8, characterized in that The method includes the following steps: B1, drying the polyester polyol and blocked HDI trimer in an oven to obtain dried polyester polyol and blocked HDI trimer; B2, placing the dried polyester polyol and blocked HDI trimer into a high-speed mixer, first stirring at low speed for 3-5 minutes, then adding the flame-retardant aid, leveling agent, anti-yellowing agent, dispersing agent and degassing agent in sequence, stirring at medium speed for 5-10 minutes, and finally adding the superfine barium sulfate, stirring at high speed for 10-15 minutes to obtain a premix; B3, feeding the premix into a twin-screw extruder, melt blending the material, extruding, pressing into a thin sheet, cooling to room temperature, crushing, and obtaining a low-energy-consumption polyurethane powder coating.

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