A low temperature cured polyurethane clearcoat resin for automotive and a method for preparing the same

Abstract

The application discloses a low-temperature cured polyurethane varnish resin for automobiles and a preparation method thereof, and belongs to the technical field of chemical product processing, and comprises a resin matrix and a curing agent.The resin matrix comprises component A and component B.The component A comprises a crosslinking system A1, a crosslinking system A2 and an additive.The component B is a curing activity regulator of a double crosslinking system of the crosslinking system A1 and the crosslinking system A2.The curing agent is diethyl malonate blocked isocyanate.The crosslinking system A1 mainly comprises a hydroxyl acrylic resin containing a beta-diketone metal ligand and a bismuth neodecanoate catalyst.The bismuth neodecanoate catalyst and the beta-diketone metal ligand form a bismuth complex.The crosslinking system A2 mainly comprises a hydroxyl acrylic resin containing an alkoxysilane group.The component B comprises poly(decane 4,6-diacetylenic diacid) modified nano-porous fibers and a silane coupling agent.On the basis of guaranteeing low-temperature rapid curing, the service life of the varnish is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical product processing, and relates to a low-temperature curing polyurethane varnish resin for automobiles and a preparation method thereof. BACKGROUND

[0002] Traditional automobile polyurethane varnish usually needs to be baked and cured at a temperature of 120-140 DEG C or even higher, which is not friendly to heat-sensitive substrates, and high-temperature baking can accelerate the aging speed of metal substrates, therefore, at present, a large number of low-temperature curing varnishes appear, and low-temperature curing of the varnish means that the resin matrix has high reactivity after being mixed with a curing agent, so that the resin matrix and the curing agent must be used up within a short time, generally 2-3 hours (such as 9900 super varnish), because the resin matrix and the curing agent will continuously generate a curing reaction after being mixed, and the curing degree continuously increases with time, and when the curing degree increases to a certain extent, the performance index of the varnish does not meet the use standard, and the short use period leads to a large amount of varnish waste. SUMMARY

[0003] The application aims to provide a low-temperature curing polyurethane varnish resin for automobiles and a preparation method thereof, and solve the problem that the use period of the current low-temperature curing varnish is short and the use period and low-temperature curing cannot be balanced.

[0004] The technical scheme adopted by the application is as follows:

[0005] A low-temperature curing polyurethane varnish resin for automobiles, comprising a resin matrix and a curing agent, wherein the resin matrix comprises component A and component B, the component A comprises a crosslinking system A1, a crosslinking system A2 and an additive, the component B is a curing activity regulator of a double crosslinking system of the crosslinking system A1 and the crosslinking system A2, and the curing agent is diethyl malonate blocked isocyanate.

[0006] The crosslinking system A1 mainly comprises a hydroxyl acrylic resin containing a beta-diketone metal ligand and a bismuth neodecanoate catalyst, and the bismuth neodecanoate catalyst and the beta-diketone metal ligand form a bismuth complex.

[0007] The crosslinking system A2 mainly comprises a hydroxyl acrylic resin containing an alkoxysilane group.

[0008] The component B comprises poly(decane 4,6-diynedioic acid) modified nano-porous fiber and silane coupling agent.

[0009] In the application, the resin is rapidly cured at about 65 DEG C under the double crosslinking system and the bismuth neodecanoate catalyst-isocyanate catalytic curing system, and the low-temperature curing in the application mainly refers to a curing temperature lower than 100 DEG C, instead of the traditional low temperature (for example, 10 DEG C or below).

[0010] Due to the low-temperature rapid curing, the use period of the resin mixed with the curing agent is 2-3 hours, and it must be used completely within 2-3 hours, and it cannot be normally used after 2-3 hours. In order to prolong the use period, the bismuth complex-closed curing agent and the modified fiber synergistic system are introduced, the physical barrier of the fiber and the activity dormancy of the bismuth complex-closed curing agent are utilized, the contact between the resin matrix and the curing agent is reduced, and the reactivity of the resin matrix and the curing agent is reduced, and the use period of the resin mixed with the curing agent at room temperature is prolonged.

[0011] The complex dissociation temperature of the bismuth complex is generally greater than 65℃, and the bismuth complex in the prior art cannot quickly dissociate at a curing temperature of about 65℃, so it is difficult to realize the low-temperature rapid curing of the polyurethane varnish. Therefore, in the case of prolonging the use period of the varnish obtained by mixing the resin matrix and the curing agent at room temperature, in order to realize the low-temperature rapid curing (returning to the above low-temperature rapid curing requirement) during curing, the poly(decane 4,6-diynedioic acid) is introduced. The poly(decane 4,6-diynedioic acid) produces succinic acid in light and air, and the succinic acid promotes the rapid dissociation of the bismuth metal complex at about 65℃, releases bismuth ions, and re-forms the new bismuth neodecanoate catalyst. At the same time, the poly(decane 4,6-diynedioic acid) produces CO2, which causes the varnish layer to appear bubbles, pinholes and other phenomena. In order to avoid solving this problem, the fiber is used as a carrier of the poly(decane 4,6-diynedioic acid), and the fiber structure forms an internal exhaust passage, which effectively avoids the retention of CO2, causing the cured paint film to appear bubbles or pinholes and other defects.

[0012] The bismuth neodecanoate catalyst catalyzes the deblocking of diethyl malonate blocked isocyanate, releases -NCO, and performs crosslinking and curing reaction with the hydroxy acrylate resin. At the same time, the bismuth neodecanoate catalyst also catalyzes the crosslinking reaction of the double crosslinking system (crosslinking systems A1 and A2). The crosslinking systems A1 and A2 form a network interpenetrating structure during the crosslinking process. This interpenetrating structure can improve the performance of the varnish. In addition, the modified fiber can also enhance the performance of the varnish. Therefore, the present application can prepare a high-performance polyurethane varnish.

[0013] In summary, after the curing agent is mixed and diluted with the resin matrix to become a varnish, it is stable in the dark, the reactivity between the resin matrix and the curing agent-bismuth catalyst is low, and the use period is long. When the varnish is sprayed, the reactivity between the resin matrix and the curing agent-bismuth catalyst can be quickly improved under the conditions of air (oxygen), light, and heating, low-temperature rapid curing is realized, and a high-performance varnish layer is obtained.

[0014] Further, the crosslinking system A1 comprises the following components in parts by weight: 90-110 parts of a hydroxyl acrylate resin containing a β-diketone metal ligand, 20-25 parts of propylene glycol methyl ether acetate, 1.8-2.5 parts of a bismuth neodecanoate catalyst; the bismuth neodecanoate catalyst forms a bismuth complex with the β-diketone metal ligand;

[0015] The crosslinking system A2 comprises the following components in parts by weight: 90-110 parts of a hydroxyl acrylate resin containing an alkoxysilane group, 1-1.2 parts of a hindered amine light stabilizer, 0.8-1.2 parts of a silane hydrolysis inhibitor.

[0016] Further, the mass ratio of the component A to the component B is 100:6-8.

[0017] Further, the mass ratio of the poly(decane 4,6-diynedioic acid) modified nanometer porous fiber to the silane coupling agent in the component B is 5-7:1.

[0018] The poly(decane 4,6-diynedioic acid) modified nanometer porous fiber is prepared by the following method:

[0019] A, dissolve cellulose acetate in a mixed solvent of acetone-dimethylacetamide with a mass ratio of 8:2 to prepare a spinning solution; the spinning solution is obtained by an electrospinning process to obtain a porous fiber membrane; the porous fiber membrane is immersed in a 0.1 M NaOH ethanol solution for hydrolysis, washed with water and dried for standby;

[0020] B, under anaerobic and dark conditions, disperse poly(decane 4,6-diynedioic acid) microparticles, PEG-PPG block copolymer, and potassium perfluorooctylsulfonate in deionized water to obtain a suspension by ultrasonic treatment;

[0021] C, under anaerobic and dark conditions, immerse the standby porous fiber membrane in the suspension, vacuum infiltrate, freeze-dry, then immerse in an acetone solution containing 1-chloro-4-propoxythioxanthone, filter, dry, and shear to obtain poly(decane 4,6-diynedioic acid) modified nanometer porous fiber.

[0022] Further, the silane coupling agent is γ-glycidyl ether propyltrimethoxysilane KH-560 or γ-aminopropyltriethoxysilane KH-550.

[0023] Further, the hindered amine light stabilizer is light stabilizer UV-292 or light stabilizer XH-622LD; the silane hydrolysis inhibitor is 1,3-divinyltetramethyldisiloxane.

[0024] Further, the auxiliary agent includes a defoaming agent, a leveling agent, and a dispersing agent.

[0025] A preparation method of a low-temperature cured polyurethane clear resin for automobiles, comprising the following steps:

[0026] S1, preparing component A

[0027] S1.1, preparing crosslinking system A1: in a light-proof reaction kettle, the hydroxyl acrylic resin containing β-diketone metal ligand and propylene glycol methyl ether acetate are added in proportion, stirred and dispersed uniformly at 25-30℃, then bismuth neodecanoate catalyst is added, heated to 50-60℃ to form bismuth complex, and crosslinking system A1 is obtained;

[0028] S1.2, preparing crosslinking system A2: under dry nitrogen protection, the hydroxyl acrylic resin containing alkoxysilane group is added in proportion, and the hindered amine light stabilizer and silane hydrolysis inhibitor are added under stirring, and reacted at 40-45℃ for 20-30 minutes to obtain crosslinking system A2;

[0029] S1.3, mixing crosslinking systems: the crosslinking systems A1 and A2 are mixed at 35-40℃, and then the additives are added after uniform stirring for 30-40 minutes to obtain component A;

[0030] S2, preparing component B: the poly(decane 4,6-diynedioic acid) modified nanoporous fiber is uniformly mixed with the silane coupling agent to obtain component B;

[0031] S3, under high-speed stirring, component B is added to component A, and the resin matrix is obtained after uniform mixing, and the resin matrix is independently stored with the curing agent, and the resin matrix is stored in vacuum and light-proof.

[0032] Further, the hydroxyl acrylic resin containing β-diketone metal ligand is prepared by the following method: acetylacetone and glycidyl methacrylate in a mass ratio of 1:1 are reacted at 60-65℃ to obtain an intermediate monomer with triethylamine as a catalyst, and then the intermediate monomer is reacted with hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene under the action of an initiator to obtain the hydroxyl acrylic resin containing β-diketone metal ligand.

[0033] Further, the hydroxyl acrylic resin containing alkoxysilane group is prepared by the following method: γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene are reacted under the action of an initiator to obtain the hydroxyl acrylic resin containing alkoxysilane group.

[0034] As described above, due to the adoption of the above technical solutions, the application has the following beneficial effects:

[0035] 1. The low-temperature cured polyurethane clearcoat resin for automobiles of the present application, after mixing and diluting the curing agent with the resin matrix into a clearcoat, is stable in the dark, the reactivity between the resin matrix and the curing agent-bismuth catalyst is low, and the shelf life is long, and after the clearcoat is sprayed, the reactivity between the resin matrix and the curing agent-bismuth catalyst can be quickly increased under the conditions of air (oxygen), light, and heat, realizing low-temperature rapid curing and obtaining a high-performance clearcoat layer.

[0036] 2. The present application realizes rapid curing of the resin at about 65°C by using a double crosslinking system and a bismuth neodecanoate catalyst-isocyanate catalytic curing system.

[0037] 3. In the present application, the poly(decane 4,6-diynedioic acid) modified nano-porous fiber not only can quickly increase the reactivity between the resin matrix and the curing agent, but also can form an internal exhaust passage to avoid the gas generated by the poly(decane 4,6-diynedioic acid) affecting the quality of the clearcoat layer.

[0038] 4. By introducing a bismuth complex-closed curing agent and a modified fiber synergistic system, the contact between the resin matrix and the curing agent is reduced and the reactivity between the resin matrix and the curing agent is reduced by using the physical barrier of the fiber and the active dormancy of the bismuth complex-closed curing agent, and the shelf life of the resin and the curing agent after mixing at room temperature is significantly prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor, wherein:

[0040] Figure 1 is the preparation process flow chart of the low-temperature cured polyurethane clearcoat resin for automobiles of the present application;

[0041] Figures 2-3 is the actual picture of the low-temperature cured polyurethane clearcoat resin for automobiles of the present application used as a clearcoat. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the following will further illustrate the present application in combination with the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application, that is, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the protection of the application.

[0044] It should be noted that the relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements recited, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the phrase "comprising a" does not exclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0045] The features and performances of the application are further described in detail below in conjunction with the embodiments.

[0046] Embodiment 1: A low-temperature cured polyurethane varnish resin for automobiles provided by a preferred embodiment of the application comprises a resin matrix and a curing agent, the resin matrix comprises component A and component B, the component A comprises a crosslinking system A1, a crosslinking system A2, and an auxiliary agent, the component B is a curing activity regulator of the double crosslinking system of the crosslinking system A1 and the crosslinking system A2; the curing agent is diethyl malonate blocked isocyanate;

[0047] The crosslinking system A1 comprises the following components in parts by weight: 90 parts of a hydroxy acrylic resin containing a β-diketone metal ligand, 20 parts of propylene glycol methyl ether acetate, and 1.8 parts of a bismuth neodecanoate catalyst; the bismuth neodecanoate catalyst forms a bismuth complex with the β-diketone metal ligand;

[0048] The crosslinking system A2 comprises the following components in parts by weight: 90 parts of a hydroxy acrylic resin containing an alkoxysilane group, 1 part of a hindered amine light stabilizer, and 0.8 parts of a silane hydrolysis inhibitor; the hindered amine light stabilizer is light stabilizer UV-292 or light stabilizer XH-622LD, and light stabilizer UV-292 is selected in this embodiment; the silane hydrolysis inhibitor is 1,3-divinyltetramethyldisiloxane;

[0049] The component B comprises poly(decane 4,6-diynedioic acid) modified nanoporous fibers and a silane coupling agent.

[0050] The mass ratio of the component A to the component B is 100:6.

[0051] The mass ratio of the poly(decyne-4,6-dioic acid) modified nanometer porous fiber in the component B to the silane coupling agent is preferably 6:1, and the silane coupling agent is γ-glycidoxypropyltrimethoxysilane KH-560 or γ-aminopropyltriethoxysilane KH-550, and γ-glycidoxypropyltrimethoxysilane KH-560 is selected in this embodiment;

[0052] The poly(decyne-4,6-dioic acid) modified nanometer porous fiber is prepared by the following method:

[0053] A. Cellulose acetate is dissolved in a mixed solvent of acetone-dimethylacetamide with a mass ratio of 8:2 to prepare a spinning solution; the spinning solution is obtained by an electrospinning process to obtain a porous fiber membrane; the porous fiber membrane is immersed in a 0.1 M NaOH ethanol solution for hydrolysis, and after washing and drying, it is ready for use;

[0054] B. Under anaerobic and dark conditions, poly(decyne-4,6-dioic acid) microparticles, PEG-PPG block copolymer (the mass ratio of PEG to PPG in the PEG-PPG block copolymer is 3:1), and potassium perfluorooctanesulfonate are dispersed in deionized water to obtain a suspension by ultrasonic treatment;

[0055] C. Under anaerobic and dark conditions, the ready-to-use porous fiber membrane is immersed in the suspension, vacuum infiltrated, freeze-dried, then immersed in an acetone solution containing 1-chloro-4-propoxythioxanthone, filtered, dried, and cut to obtain poly(decyne-4,6-dioic acid) modified nanometer porous fiber.

[0056] The auxiliary agents include defoaming agents, leveling agents, and dispersants, and the use amount of the auxiliary agents is dynamically adjusted according to the use amount in the prior art and the actual situation

[0057] As shown in Figure 1 A method for preparing a low-temperature cured polyurethane varnish resin for automobiles, comprising the following steps:

[0058] S1, preparing component A

[0059] S1.1, preparing a crosslinking system A1: in a light-proof reaction kettle, β-diketone metal ligand-containing hydroxy acrylate resin and propylene glycol methyl ether acetate are added in proportion, and after being uniformly dispersed by stirring at 25-30°C, bismuth neodecanoate catalyst is added, and the temperature is raised to 50-60°C to form a bismuth complex by reaction, thereby obtaining the crosslinking system A1;

[0060] S1.2, Preparation of crosslinking system A2: under the protection of dry nitrogen, the hydroxy acrylate resin containing alkoxysilane group was added proportionally, the hindered amine light stabilizer and the silane hydrolysis inhibitor were added under stirring, and the reaction was carried out at 40-45℃ for 20-30 minutes to obtain the crosslinking system A2;

[0061] S1.3, Mixing of crosslinking system: the crosslinking systems A1 and A2 were mixed at 35-40℃, and the additives were added after uniform stirring for 30-40 minutes to obtain component A;

[0062] S2, Preparation of component B: the poly(decane 4,6-diynedioic acid) modified nanoporous fiber was uniformly mixed with the silane coupling agent to obtain component B;

[0063] S3, Under high-speed stirring, component B was added into component A, and the resin matrix was obtained after uniform mixing, and the resin matrix and the curing agent were independently stored and the resin matrix was stored in vacuum and light-proof.

[0064] The hydroxy acrylate resin containing β-diketone metal ligand is prepared by the following method: acetylacetone and glycidyl methacrylate with a mass ratio of 1:1 are reacted at 60-65℃ to obtain an intermediate monomer with triethylamine as a catalyst, and then the intermediate monomer is reacted with hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene under the action of an initiator to obtain the hydroxy acrylate resin containing β-diketone metal ligand; wherein the mass ratio of the intermediate monomer to hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene is 1:2:3:2:1.

[0065] The hydroxy acrylate resin containing alkoxysilane group is prepared by the following method: γ-methacryloyloxypropyl trimethoxysilane, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene are reacted under the action of an initiator to obtain the hydroxy acrylate resin containing alkoxysilane group; wherein the mass ratio of γ-methacryloyloxypropyl trimethoxysilane, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene is 8:25:30:20:8.

[0066] Example 2: This example is based on example 1, and the difference between example 1 and example 2 is that: the crosslinking system A1 includes the following components in parts by weight: 100 parts of the hydroxy acrylate resin containing β-diketone metal ligand, 23 parts of propylene glycol methyl ether acetate, and 2.3 parts of bismuth neodecanoate catalyst; the bismuth neodecanoate catalyst forms a bismuth complex with the β-diketone metal ligand.

[0067] The crosslinking system A2 includes the following components in parts by weight: 100 parts of the hydroxy acrylate resin containing alkoxysilane group, 1.1 parts of hindered amine light stabilizer, and 1 part of silane hydrolysis inhibitor. The rest is consistent.

[0068] Example 3: This example is based on Example 1, except that the crosslinking system A1 comprises the following components in parts by weight: 110 parts of a hydroxyl acrylate resin containing a beta-diketone metal ligand, 25 parts of propylene glycol methyl ether acetate, 2.5 parts of a bismuth neodecanoate catalyst; the bismuth neodecanoate catalyst forms a bismuth complex with the beta-diketone metal ligand.

[0069] The crosslinking system A2 comprises the following components in parts by weight: 110 parts of a hydroxyl acrylate resin containing an alkoxysilane group, 1.2 parts of a hindered amine light stabilizer, 1.2 parts of a silane hydrolysis inhibitor. The rest is uniform.

[0070] Example 4: This example is based on Example 2, except that the mass ratio of component A to component B is 100:7. The rest is uniform.

[0071] Example 5: This example is based on Example 2, except that the mass ratio of component A to component B is 100:8. The rest is uniform.

[0072] Comparative Example 1: Based on Example 1, this comparative example differs from Example 1 in that the crosslinking system A1 is not contained in this comparative example, and the crosslinking system A2, the auxiliary agent, and component B are the main components for preparing the resin matrix, and the rest is adaptively adjusted.

[0073] Comparative Example 2: Based on Example 1, this comparative example differs from Example 1 in that the crosslinking system A2 is not contained in this comparative example, and the crosslinking system A1, the auxiliary agent, and component B are the main components for preparing the resin matrix, and the rest is adaptively adjusted based on Example 1.

[0074] Comparative Example 3: Based on Example 1, this comparative example differs from Example 1 in that the crosslinking system A1 in this comparative example is mainly composed of a hydroxyl acrylate resin and a bismuth neodecanoate catalyst, the hydroxyl acrylate resin does not contain a beta-diketone metal ligand, the crosslinking system A1 contains the bismuth neodecanoate catalyst, and does not form a bismuth complex, and the rest is adaptively adjusted based on Example 1.

[0075] Comparative Example 4: Based on Example 1, this comparative example differs from Example 1 in that the hindered amine light stabilizer is not contained in the crosslinking system A2 in this comparative example, and the rest is adaptively adjusted based on Example 1.

[0076] Comparative Example 5: Based on Example 1, this comparative example differs from Example 1 in that the silane hydrolysis inhibitor is not contained in the crosslinking system A2 in this comparative example, and the rest is adaptively adjusted based on Example 1.

[0077] Comparative Example 6: Based on Example 1, the difference between this comparative example and Example 1 is that this comparative example does not contain a curing agent, and the rest is adaptively adjusted based on Example 1.

[0078] Comparative Example 7: Based on Example 1, the difference between this comparative example and Example 1 is that the curing agent in this comparative example is an unblocked isocyanate curing agent, and the rest is adaptively adjusted based on Example 1.

[0079] Comparative Example 8: Based on Example 1, the difference between this comparative example and Example 1 is that this comparative example does not contain Component B, and the rest is adaptively adjusted based on Example 1.

[0080] Comparative Example 9: Based on Example 1, the difference between this comparative example and Example 1 is that Component B in this comparative example only includes poly(decane 4,6-diynedioic acid), and the rest is adaptively adjusted based on Example 1.

[0081] Comparative Example 10: Based on Example 1, the difference between this comparative example and Example 1 is that Component B in this comparative example is only nanoporous fiber and silane coupling agent, and does not contain poly(decane 4,6-diynedioic acid), and the rest is adaptively adjusted based on Example 1.

[0082] Comparative Example 11: Based on Example 1, the difference between this comparative example and Example 1 is that Component B in this comparative example does not contain a silane coupling agent.

[0083] Test Example 1: The resin matrix and curing agent in Examples 1-5 and Comparative Examples 1-11 are mixed to prepare a varnish for automobiles, and the apparent characteristics of the varnish before and after curing and the shelf life at room temperature in the dark are detected, and the results are shown in Table 1.

[0084] The apparent characteristics of the varnish before and after curing include visible color, transparency, and the presence or absence of precipitation, etc.

[0085] Shelf life at room temperature: samples were taken every half hour, and viscosity was tested according to the paint viscosity determination method (GB / T 1723-1993); end of shelf life: viscosity > 50 s or appearance of gel, precipitation, turbidity, etc.

[0086] Table 1 Varnish Test Results

[0087]

[0088] The isocyanate sealing curing agent, bismuth complex and fiber barrier in the application can delay the crosslinking of the resin and prolong the service life; the release of isocyanate and bismuth catalyst seriously affects the curing speed and the quality of the paint layer, the longer the curing time is, the greater the influence of the environment on the paint layer is, and the poorer the quality is, the release of isocyanate and bismuth catalyst can be affected by component B, therefore, the component B in the application is very important, which not only affects the curing speed, but also affects the quality of the paint layer.

[0089] Test Example 2: Based on Test Example 1, the curing time and the performance of the varnish layer without abnormal macroscopic characteristics of the varnish in Test Example 1 under air, 65 DEG C, white light irradiation were detected, and the detection results are shown in Table 2.

[0090] Curing time: according to GB / T 1728-2020 “Paint film, putty film drying time determination method”, the open time and the real dry time were determined;

[0091] Adhesion detection: according to GB / T 9286-2021, the adhesion performance of the varnish was detected, the falling area ratio was determined according to 0-5 levels, and a unified test basis was provided for quality control in the paint industry;

[0092] Weather resistance: the cured varnish layer sample was placed in an ultraviolet accelerated aging test machine for accelerated aging for 2000 hours, and whether abnormal phenomena such as cracking, chalking, falling off, etc. occurred was observed; the cured varnish layer sample was placed in a xenon lamp aging oven for accelerated aging for 2000 hours, and whether abnormal phenomena occurred was observed; both of them had good weather resistance;

[0093] Gasoline resistance: the cured varnish layer test sample was immersed in 90# gasoline at room temperature for 48 hours, and whether abnormal phenomena occurred was observed, including whitening, blistering, paint peeling, wrinkling, cracking, rusting and obvious loss of gloss, softening of the coating, etc.;

[0094] Hardness detection: according to GB / T 6739-2022 “Paint and varnish pencil method for determining paint film hardness”, the hardness of the varnish layer was detected.

[0095] Table 2: Performance detection results of varnish

[0096]

[0097] The application has shorter curing time, and better hardness, weather resistance, gasoline resistance and adhesion.

[0098] Test Example 3: For the actual application of a certain plate, the varnish prepared in the range of Example 4 was used in combination with black paint, and the physical diagram is shown in Figure 2 、 3 , Figure 2 is a paint layer without varnish spraying, Figure 3For the color paint layer of the spray varnish, the varnish of the present application does not affect the black color development and can improve the gloss.

[0099] The above merely describes the preferred embodiments of the present application and is not used to limit the protection scope of the present application, and any modification, equivalent replacement and improvement made by any skilled person in the art within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low temperature cured polyurethane clearcoat resin for automotive applications, characterized in that: The resin matrix comprises component A and component B, the component A comprises crosslinking system A1, crosslinking system A2, and an auxiliary agent, and the component B is a curing activity regulator of the crosslinking system A1 and crosslinking system A2 double crosslinking system; The curing agent is diethyl malonate blocked isocyanate; The crosslinking system A1 comprises the following components in parts by weight: 90-110 parts of a hydroxyl acrylate resin containing a β-diketone metal ligand, 20-25 parts of propylene glycol methyl ether acetate, and 1.8-2.5 parts of a bismuth neodecanoate catalyst; the bismuth neodecanoate catalyst forms a bismuth complex with the β-diketone metal ligand; The crosslinking system A2 comprises the following components in parts by weight: 90-110 parts of a hydroxyl acrylate resin containing an alkoxysilane group, 1-1.2 parts of a hindered amine light stabilizer, and 0.8-1.2 parts of a silane hydrolysis inhibitor; The mass ratio of the component A to the component B is 100:6-8; The mass ratio of the poly(decane 4,6-diynedioic acid) modified nanometer porous fiber to the silane coupling agent in the component B is 5-7:1; The poly(decane 4,6-diynedioic acid) modified nanometer porous fiber is prepared by the following method: A. Cellulose acetate is dissolved in a mixed solvent of acetone-dimethylacetamide with a mass ratio of 8:2 to prepare a spinning solution; the spinning solution is obtained by an electrospinning process to obtain a porous fiber membrane; the porous fiber membrane is immersed in a 0.1 M NaOH ethanol solution for hydrolysis, washed with water, and dried for standby; B. Under anaerobic and dark conditions, poly(decane 4,6-diynedioic acid) microparticles, PEG-PPG block copolymer, and potassium perfluorooctylsulfonate are dispersed in deionized water to obtain a suspension by ultrasonic treatment; C. Under anaerobic and dark conditions, the standby porous fiber membrane is immersed in the suspension, vacuum infiltrated, and freeze-dried; then the porous fiber membrane is immersed in an acetone solution containing 1-chloro-4-propoxy thioxanthone, filtered, dried, and sheared to obtain the poly(decane 4,6-diynedioic acid) modified nanometer porous fiber.

2. A low temperature cured polyurethane clearcoat resin for automotive use according to claim 1, characterized in that: The silane coupling agent is γ-glycidyl ether oxypropyl trimethoxysilane KH-560 or γ-aminopropyl triethoxysilane KH-550.

3. A low temperature cured polyurethane clearcoat resin for automotive use according to claim 1, characterized in that: The hindered amine light stabilizer is light stabilizer UV-292 or light stabilizer XH-622LD; and the silane hydrolysis inhibitor is 1,3-divinyl tetramethyl disiloxane.

4. A cryogenically cured polyurethane clearcoat resin for automotive use according to claim 1, characterized in that: The auxiliary agent comprises a defoaming agent, a leveling agent, and a dispersant.

5. A process for the preparation of a low temperature cured polyurethane clearcoat resin for automotive applications according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1, preparing component A S1.1, preparing crosslinking system A1: in a light-proof reaction kettle, β-diketone metal ligand-containing hydroxyl acrylate resin and propylene glycol methyl ether acetate are added in proportion, stirred and uniformly dispersed at 25-30°C, and then bismuth neodecanoate catalyst is added; the temperature is raised to 50-60°C to form a bismuth complex by reaction, and crosslinking system A1 is obtained; S1.2, preparing crosslinking system A2: under dry nitrogen protection, β-diketone metal ligand-containing hydroxyl acrylate resin is added in proportion, and a hindered amine light stabilizer and a silane hydrolysis inhibitor are added under stirring; the temperature is raised to 40-45°C to react for 20-30 minutes to obtain crosslinking system A2. S1.3, mixed crosslinking system: mixing crosslinking system A1, A2 at 35-40℃, continue to stir evenly, then add auxiliary agent, stir for 30-40 minutes to obtain component A; S2, preparation of component B: uniformly mixing poly (decane 4, 6-diacetylene diacid) modified nanoporous fiber and silane coupling agent to obtain component B; S3, under high speed stirring, adding component B in component A, mixing evenly to obtain resin matrix, and the resin matrix is independently stored with curing agent, and the resin matrix is stored in vacuum and away from light.

6. A process for the preparation of a low temperature cured polyurethane clearcoat resin for automotive applications as claimed in claim 5, wherein: The hydroxyl acrylic resin containing β-diketone metal ligand is prepared by the following method: acetylacetone and glycidyl methacrylate with a mass ratio of 1:1 are reacted at 60-65℃ to obtain an intermediate monomer with triethylamine as a catalyst, and then the intermediate monomer is reacted with hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene under the action of an initiator to obtain the hydroxyl acrylic resin containing β-diketone metal ligand.

7. The method for preparing a low-temperature curing automotive polyurethane clear varnish resin according to claim 5, characterized in that: The hydroxyl acrylic resin containing alkoxysilane group is prepared by the following method: γ-methacryloyloxypropyl trimethoxysilane, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and styrene are reacted under the action of an initiator to obtain the hydroxyl acrylic resin containing alkoxysilane group.

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