Fluorescent polyurethane primer as well as preparation method and application thereof

Abstract

The invention discloses a fluorescent polyurethane primer as well as a preparation method and application thereof. The fluorescent polyurethane primer is prepared from the following raw materials in parts by mass: 14 to 30 parts of isocyanate-terminated polyurethane resin, 4 to 8 parts of a cross-linking agent, 2 to 8 parts of a fluorescent modified adhesion promoter, 0.05 to 0.2 part of a catalyst, 0.5 to 2 parts of a water removal agent, 4 to 8 parts of carbon black and 50 to 75 parts of a first solvent. The isocyanate-terminated polyurethane resin is prepared by reaction of diisocyanate and polyester diol, the fluorescence modified adhesion promoter is prepared by reaction of a hydroxyl-containing fluorescence modified silane coupling agent and triisocyanate, and the hydroxyl-containing fluorescence modified silane coupling agent is prepared by reaction of an active hydrogen-containing fluorescent compound and an epoxy group-containing silane coupling agent. The fluorescent polyurethane primer disclosed by the invention contains the fluorescent modified adhesion promoter with a specific structure, so that the primer disclosed by the invention has the characteristics of excellent adhesion, durability and fluorescent effect stability.

Description

Technical Field

[0001] This invention relates to the field of primer technology, and in particular to a fluorescent polyurethane primer, its preparation method and application. Background Technology

[0002] In automobile manufacturing and repair, the reliable bonding between automotive glass and the vehicle body directly affects driving safety and sealing performance. Due to the polarity difference between glass (an inorganic material) and the vehicle body coating or adhesive (an organic material), direct bonding can easily lead to insufficient adhesion, causing the glass to loosen, detach, or fail to seal properly during driving. Therefore, a primer needs to be applied to the glass surface to improve the bonding strength at the interface, providing a good foundation for the subsequent curing and bonding of the adhesive.

[0003] As the automotive industry places increasing demands on production efficiency and quality control, traditional primers are gradually revealing numerous shortcomings. Regarding production efficiency, with advancements in technology, most OEMs now use intelligent machinery to apply primers. After application, the effectiveness still relies heavily on manual visual inspection, and solvent evaporation poses potential health risks to workers, contradicting increasingly stringent environmental regulations. In terms of application and quality control, most commercially available primers are non-fluorescent, making it difficult to visually assess the uniformity of coverage. Incomplete application or uneven thickness can lead to adhesion failure. Furthermore, some products require the use of activators, complicating the process and hindering automated continuous production.

[0004] To address the aforementioned issues, fluorescent primers have gradually entered the research field. By adding fluorescent components, they can achieve rapid and visual detection of coating coverage, improving quality control efficiency. However, existing fluorescent primers still have significant shortcomings: Chinese patent application CN116944002A introduces fluorescent agents through physical mixing, resulting in poor fluorescence stability. Long-term exposure to light, temperature, and humidity changes can easily lead to fluorescent agent loss and attenuation, affecting the accuracy of subsequent quality traceability. Chinese patent application CN120309614A introduces synthesized fluorescent small molecules into a two-component polyurethane primer, fixing the fluorescent molecules in the polyurethane molecular backbone through a curing reaction. However, these fluorescent molecules only impart fluorescence to the material; adhesion enhancement mainly relies on other silane coupling agents in the system. Furthermore, as a two-component system, thorough and uniform mixing is necessary in practical applications; otherwise, poor adhesion and uneven dispersion of fluorescent molecules can easily occur. Additionally, the two-component primer must be used within a short time after mixing; otherwise, it will solidify completely, causing equipment blockage and affecting construction efficiency.

[0005] Therefore, developing a fluorescent primer with stable fluorescence effect, excellent adhesion and convenient construction has important practical significance and application value. Summary of the Invention

[0006] In view of the above problems, the purpose of this invention is to provide a fluorescent polyurethane primer, its preparation method and application. The fluorescent polyurethane primer of this invention contains a fluorescent modified adhesive promoter with a specific structure, which makes the primer of this invention have excellent adhesion, durability and fluorescence effect stability.

[0007] To achieve the above objectives, the first aspect of the present invention provides a fluorescent polyurethane primer, wherein the raw materials for preparation, by weight, include 14-30 parts of terminal isocyanate polyurethane resin, 4-8 parts of crosslinking agent, 2-8 parts of fluorescent modified adhesive accelerator, 0.05-0.2 parts of catalyst, 0.5-2 parts of dehydrating agent, 4-8 parts of carbon black and 50-75 parts of first solvent; Among them, the isocyanate-terminated polyurethane resin is prepared by reacting diisocyanate and polyester diol, the fluorescent modified adhesive promoter is prepared by reacting hydroxyl-containing fluorescent modified silane coupling agent with triisocyanate, the hydroxyl-containing fluorescent modified silane coupling agent is prepared by reacting fluorescent compound containing active hydrogen with epoxy-containing silane coupling agent, and the molar ratio of hydroxyl groups in the hydroxyl-containing fluorescent modified silane coupling agent to isocyanate groups in the triisocyanate is 1.0~1.8:3.0.

[0008] Compared with the prior art, the fluorescent polyurethane primer of the present invention contains a fluorescent modified adhesion promoter with a specific structure, which gives the primer of the present invention excellent adhesion, durability and stability of fluorescence effect, as specifically manifested as follows: (1) The fluorescent modified adhesive promoter of the present invention is first prepared by reacting a fluorescent compound containing active hydrogen and a silane coupling agent containing epoxy group to prepare a hydroxyl-containing fluorescent modified silane coupling agent, and then reacted with triisocyanate to obtain the product. The molar ratio of hydroxyl groups in the hydroxyl-containing fluorescent modified silane coupling agent to isocyanate groups in the triisocyanate is controlled to be 1.0~1.8:3.0. Through the aforementioned chemical reaction, fluorescent molecules are grafted into the structure containing isocyanate groups, so that the fluorescent modified adhesive promoter of the present invention simultaneously possesses fluorescent properties and adhesive promotion function, thereby enabling the primer of the present invention to exhibit fluorescence properties and adhesive promotion function at a specific wavelength of violet light. It exhibits obvious fluorescence under external light, enabling rapid identification of whether the primer has been applied to the substrate and the uniformity of primer application during automated rapid production processes, reducing manual operation and quality uncertainty. At the same time, the isocyanate groups contained in the fluorescent modified adhesion promoter can form chemical bonds with the -OH on the substrate surface through a dehydration condensation reaction, which can effectively improve the adhesion performance of the primer of this invention. More importantly, the fluorescent molecules will not migrate or be lost due to harsh weather conditions such as exposure to sunlight and rain, exhibiting excellent durability and stability of fluorescence effect, which helps to ensure the accuracy of subsequent quality traceability.

[0009] (2) The fluorescent modified adhesive promoter prepared by the present invention through epoxy ring-opening and grafting reaction has an isocyanate group as its end group, which has good compatibility with the terminal isocyanate resin of the present invention. It does not need to be formulated into a two-component system, and the construction is simple and convenient. The equipment maintenance is simple and convenient, and it is easy to automate the operation.

[0010] Specifically, the mass fraction of the isocyanate-terminated polyurethane resin can be, but is not limited to, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 26, 28, or 30 parts. Preferably, the mass fraction of the isocyanate-terminated polyurethane resin is 18 to 30 parts. If the mass fraction of the isocyanate-terminated polyurethane resin is too low, it may lead to a decrease in the water resistance and damp heat resistance of the primer. The mass fraction of the crosslinking agent can be, but is not limited to, 4, 5, 6, 7, or 8 parts. The mass fraction of the fluorescently modified adhesive accelerator can be, but is not limited to, 2, 3, 4, 5, 6, 7, or 8 parts. Preferably, the mass fraction of the fluorescently modified adhesive accelerator is 3 to 8 parts. If the mass fraction of the fluorescently modified adhesive accelerator is too low, it may lead to a decrease in the water resistance and damp heat resistance of the primer. The mass fraction of the catalyst may be, but is not limited to, 0.05 parts, 0.08 parts, 0.1 parts, 0.12 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.18 parts, or 0.2 parts. The mass fraction of the dehydrating agent may be, but is not limited to, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.8 parts, or 2 parts. The mass fraction of the carbon black may be, but is not limited to, 4 parts, 5 parts, 6 parts, 7 parts, or 8 parts. The mass fraction of the primary solvent may be, but is not limited to, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, or 75 parts.

[0011] As a preferred technical solution, the molar ratio of active hydrogen in the fluorescent compound containing active hydrogen to epoxy group in the silane coupling agent containing epoxy group is 1:1. Controlling the ratio within this range yields a product with higher purity.

[0012] As a preferred technical solution, the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polyester diol of the present invention is 1.4~1.8:1. Specifically, the molar ratio of isocyanate groups to hydroxyl groups can be, but is not limited to, 1.4:1, 1.5:1, 1.6:1, 1.7:1, or 1.8:1. Controlling the molar ratio of isocyanate groups to hydroxyl groups within this range ensures complete reaction of the hydroxyl groups, resulting in a polyurethane resin with isocyanate groups at the ends of the molecular chains.

[0013] As a preferred technical solution, the fluorescent compound containing active hydrogen of the present invention is selected from at least one of 3-carboxycoumarin, 4-carboxycoumarin, 6-carboxycoumarin, 7-hydroxycoumarin-3-carboxylic acid, 7-methoxycoumarin-3-carboxylic acid, 8-bromo-3-carboxycoumarin, rhodamine B, fluorescein, fluorescein derivatives, 4-aminophthalimide, and fluorescein amine.

[0014] As a preferred technical solution, the epoxy-containing silane coupling agent of the present invention is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0015] As a preferred technical solution, the triisocyanate of the present invention is selected from at least one of HDI trimer, TDI trimer, IPDI trimer, triphenyl triisocyanate thiophosphate, and triphenylmethane triisocyanate.

[0016] As a preferred technical solution, the polyester diol of the present invention is selected from at least one of phthalic anhydride polyester diol, polycarbonate diol, and polycaprolactone diol. Specifically, the molecular weight of the polyester diol is 500~2000 g / mol.

[0017] As a preferred technical solution, the diisocyanate of the present invention is selected from at least one of TDI (toluene diisocyanate), MDI (diphenylmethane diisocyanate), HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), NDI (naphthalene diisocyanate), and XDI (m-phenylenedimethyl isocyanate).

[0018] As a preferred technical solution, the crosslinking agent of the present invention is selected from at least one of HDI trimer, TDI trimer, IPDI trimer, triphenyl triisocyanate thiophosphate, and triphenylmethane triisocyanate.

[0019] As a preferred technical solution, the catalyst of the present invention is selected from at least one of organotin catalysts and titanate catalysts. Specifically, the organotin catalyst may be, but is not limited to, dibutyltin dilaurate, dibutyltin diacetate, or di(dodecyl sulfide)dibutyltin; the titanate catalyst may be, but is not limited to, tetraisopropyl titanate or tetrabutyl titanate. Preferably, the catalyst of the present invention is dibutyltin dilaurate.

[0020] As a preferred technical solution, the dehydrating agent of the present invention includes p-toluenesulfonyl isocyanate.

[0021] As a preferred technical solution, the first solvent of the present invention is selected from at least one of ethyl acetate, butyl acetate, acetone, butanone, and xylene.

[0022] A second aspect of the present invention provides a method for preparing the aforementioned fluorescent polyurethane primer, comprising: (1) Preparation of fluorescent modified adhesion promoter A fluorescent compound containing active hydrogen, an epoxy-containing silane coupling agent, triethylamine, and a second solvent are placed in a reactor and reacted until the epoxy infrared peak disappears to obtain a hydroxyl-containing fluorescent modified silane coupling agent. Triisocyanate is then added and reacted until NCO reaches the theoretical value. (2) Preparation of isocyanate-terminated polyurethane resin The dehydrated polyester diol, diisocyanate and third solvent are placed in a reactor to react until NCO reaches the theoretical value; (3) Preparation of fluorescent polyurethane primer The formulated amounts of terminal isocyanate polyurethane resin, crosslinking agent, fluorescent modified adhesive accelerator, catalyst, dehydrating agent, carbon black, and first solvent are placed in a ball mill and ground.

[0023] As a preferred technical solution, in step (1), the molar ratio of active hydrogen in the fluorescent compound containing active hydrogen to epoxy group in the silane coupling agent containing epoxy group is 1:1.

[0024] As a preferred technical solution, in step (1), the molar ratio of the hydroxyl groups in the hydroxyl-containing fluorescent modified silane coupling agent to the isocyanate groups in the triisocyanate is 1.0~1.8:3.0. Specifically, the molar ratio of the hydroxyl groups to the isocyanate groups can be, but is not limited to, 1.0:3.0, 1.1:3.0, 1.2:3.0, 1.3:3.0, 1.4:3.0, 1.5:3.0, 1.6:3.0, 1.7:3.0, or 1.8:3.0.

[0025] As a preferred technical solution, in step (1), the amount of triethylamine added is 0.1% to 0.5% of the mass of the fluorescent compound containing active hydrogen. Specifically, the amount of triethylamine added is 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% of the mass of the fluorescent compound containing active hydrogen, but is not limited thereto, and other values ​​not listed within the scope of this invention are also applicable.

[0026] As a preferred technical solution, in step (1), after the reaction reaches the theoretical value of NCO, the reaction solution is further subjected to vacuum distillation to remove the second solvent.

[0027] As a preferred technical solution, in step (1), the reaction temperature is 60℃~70℃. For example, the reaction temperature is specifically, but not limited to, 60℃, 62℃, 64℃, 65℃, 66℃, 68℃, and 70℃, with 65℃ being the most preferred.

[0028] As a preferred technical solution, in step (2), the dehydration treatment includes vacuum distilling the polyester diol at 100℃~110℃ until the moisture content is less than 0.03%. The vacuum degree during the vacuum distillation process is ≤-0.098MPa. As a preferred technical solution, in step (2), the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polyester diol is 1.4~1.8:1. Specifically, the molar ratio of isocyanate groups to hydroxyl groups can be, but is not limited to, 1.4:1, 1.5:1, 1.6:1, 1.7:1, or 1.8:1.

[0029] As a preferred technical solution, in step (2), the reaction temperature is 60℃~70℃. Specifically, the reaction temperature can be, but is not limited to, 60℃, 62℃, 64℃, 65℃, 66℃, 68℃, or 70℃, with 65℃ being the most preferred. As a preferred technical solution, in step (2), after the reaction reaches the theoretical value of NCO, the reaction solution is further subjected to vacuum distillation to remove the third solvent.

[0030] As a preferred technical solution, in step (3), the grinding time is 6 to 10 hours. For example, the grinding time can be, but is not limited to, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, with 8 hours being the most preferred.

[0031] As a preferred technical solution, the second solvent and the third solvent are each independently selected from at least one of ethyl acetate, butyl acetate, acetone, butanone, and xylene. Furthermore, the second solvent and the third solvent may be the same as or different from the first solvent.

[0032] A third aspect of this invention provides the application of the aforementioned fluorescent polyurethane primer, or the fluorescent polyurethane primer prepared according to the aforementioned method, in automotive glass installation. The fluorescent polyurethane primer of this invention exhibits excellent adhesion and durability to windshields (ceramic glass), sheet metal (painted panels), etc. Simultaneously, this primer displays significant fluorescence under ultraviolet light, allowing for rapid identification of whether the primer has been applied to the substrate and detection of coating uniformity in automated production. It has promising application prospects in modern automated industry. Detailed Implementation

[0033] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0034] The raw materials used in the embodiments and comparative examples of this invention are all industrial grade. Please refer to Table 1 for the material source description.

[0035] Table 1 Material Source Description

[0036] Example 1 This embodiment provides a fluorescent polyurethane primer, which, by mass, comprises 22 parts of terminal isocyanate polyurethane resin, 6 parts of crosslinking agent, 4 parts of fluorescent modified adhesive accelerator, 0.1 parts of catalyst, 1 part of dehydrating agent, 6 parts of carbon black, and 60.9 parts of first solvent; wherein the crosslinking agent is HDI trimer, the catalyst is dibutyltin dilaurate, the dehydrating agent is p-toluenesulfonyl isocyanate, the carbon black is SB250 carbon black, and the first solvent is ethyl acetate.

[0037] The preparation of the fluorescent modified adhesive accelerator includes: placing 190.15 parts by mass of 6-carboxycoumarin, 236.34 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane, 0.95 parts by mass of triethylamine, and 427.44 parts by mass of ethyl acetate in a reactor, heating to 65°C and holding the reaction at that temperature until the epoxy infrared peak disappears, then adding 504.58 parts by mass of HDI trimer, holding the reaction at 65°C until the NCO reaches 6.18%, removing the solvent by vacuum distillation to obtain the fluorescent modified adhesive accelerator.

[0038] The preparation of the terminal isocyanate polyurethane resin includes: placing 100 parts by mass of phthalic anhydride polyester diol HDPOL-310P (number average molecular weight of 1000, water content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 40 parts by mass of MDI, maintaining the temperature until NCO reaches 2.10%, removing the solvent by vacuum distillation to obtain the terminal isocyanate polyurethane resin.

[0039] The preparation of the fluorescent polyurethane primer includes: grinding 22 parts by weight of isocyanate-terminated polyurethane resin, 6 parts of HDI trimer, 4 parts of fluorescent modified adhesive accelerator, 0.1 parts of dibutyltin dilaurate, 1 part of p-toluenesulfonyl isocyanate, 6 parts of SB250 carbon black, and 60.9 parts of ethyl acetate in a ball mill for 8 hours to obtain the fluorescent polyurethane primer, which is then sealed and stored for later use.

[0040] Example 2 The difference between this embodiment and Embodiment 1 is that: The preparation of the fluorescent modified adhesive accelerator includes: placing 479.01 parts by mass of Rhodamine B, 236.34 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane, 2.40 parts by mass of triethylamine, and 717.75 parts by mass of ethyl acetate in a reactor, heating to 65°C and maintaining the temperature until the epoxy infrared peak disappears, then adding 504.58 parts by mass of HDI trimer, maintaining the temperature at 65°C until the NCO reaches 4.33%, removing the solvent by vacuum distillation to obtain the fluorescent modified adhesive accelerator.

[0041] Everything else is the same as in Example 1.

[0042] Example 3 The difference between this embodiment and Embodiment 1 is that: The preparation of the fluorescent modified adhesive accelerator includes: placing 190.15 parts by mass of 6-carboxycoumarin, 246.38 parts by mass of β-(3,4-epoxycyclohexane)ethyltrimethoxysilane, 0.95 parts by mass of triethylamine and 437.48 parts by mass of ethyl acetate in a reactor, heating to 65°C and holding the reaction at that temperature until the epoxy infrared peak disappears, then adding 504.58 parts by mass of HDI trimer, holding the reaction at 65°C until the NCO reaches 6.09%, removing the solvent by vacuum distillation to obtain the fluorescent modified adhesive accelerator.

[0043] Everything else is the same as in Example 1.

[0044] Example 4 The difference between this embodiment and Embodiment 1 is that: The preparation of the fluorescent modified adhesive accelerator includes: placing 190.15 parts by mass of 6-carboxycoumarin, 236.34 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane, 0.95 parts by mass of triethylamine, and 427.44 parts by mass of ethyl acetate in a reactor, heating to 65°C and maintaining the temperature until the epoxy infrared peak disappears, then adding 465.38 parts by mass of triphenyl triisocyanate thiophosphate, maintaining the temperature at 65°C until the NCO reaches 6.36%, removing the solvent by vacuum distillation to obtain the fluorescent modified adhesive accelerator.

[0045] Everything else is the same as in Example 1.

[0046] Example 5 The difference between this embodiment and Embodiment 1 is that: The preparation of the fluorescent modified adhesive accelerator includes: placing 190.15 parts by mass of 6-carboxycoumarin, 236.34 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane, 0.95 parts by mass of triethylamine, and 427.44 parts by mass of ethyl acetate in a reactor, heating to 65°C and maintaining the temperature until the epoxy infrared peak disappears, then adding 367.36 parts by mass of triphenylmethane triisocyanate, maintaining the temperature at 65°C until the NCO reaches 6.87%, removing the solvent by vacuum distillation to obtain the fluorescent modified adhesive accelerator.

[0047] Everything else is the same as in Example 1.

[0048] Example 6 The difference between this embodiment and Embodiment 1 is that: The preparation of isocyanate-terminated polyurethane resin includes: placing 100 parts by mass of polycarbonate diol PCDLT6001 (number average molecular weight of 1000, water content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 40 parts by mass of MDI, maintaining the temperature until NCO reaches 2.10%, removing the solvent by vacuum distillation to obtain isocyanate-terminated polyurethane resin.

[0049] Everything else is the same as in Example 1.

[0050] Example 7 The difference between this embodiment and Embodiment 1 is that: The preparation of isocyanate-terminated polyurethane resin includes: placing 100 parts by mass of polycaprolactone diol PCL210N (number average molecular weight of 1000, moisture content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 40 parts by mass of MDI, maintaining the temperature until NCO reaches 2.10%, removing the solvent by vacuum distillation to obtain isocyanate-terminated polyurethane resin.

[0051] Everything else is the same as in Example 1.

[0052] Example 8 The difference between this embodiment and Embodiment 1 is that: The preparation of the terminal isocyanate polyurethane resin includes: placing 100 parts by mass of polyester diol HDPOL-310P (number average molecular weight of 1000, moisture content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 27.87 parts by mass of TDI, maintaining the temperature until the NCO reaches 2.21%, removing the solvent by vacuum distillation to obtain the terminal isocyanate polyurethane resin.

[0053] Everything else is the same as in Example 1.

[0054] Example 9 The difference between this embodiment and Example 1 is that the crosslinking agent is triphenyl triisocyanate thiophosphate, while the rest are the same as in Example 1.

[0055] Example 10 The difference between this embodiment and Example 1 is that the crosslinking agent is triphenylmethane triisocyanate, while the rest are the same as in Example 1.

[0056] Example 11 The difference between this embodiment and Example 9 is that the solvent is butanone, while all other aspects are the same as in Example 9.

[0057] Example 12 The difference between this embodiment and embodiment 9 is that the fluorescent modified adhesive accelerator is 8 parts, while the rest are the same as in embodiment 9.

[0058] Example 13 The difference between this embodiment and embodiment 9 is that the fluorescent modified adhesive accelerator is 2 parts, while the rest are the same as in embodiment 9.

[0059] Example 14 The difference between this embodiment and Embodiment 9 is that the amount of isocyanate-terminated polyurethane resin is 30 parts, while the rest are the same as in Embodiment 9.

[0060] Example 15 The difference between this embodiment and Embodiment 9 is that the amount of isocyanate-terminated polyurethane resin is 14 parts, while the rest are the same as in Embodiment 9.

[0061] Comparative Example 1 This comparative example provides a fluorescent polyurethane primer, which, by mass, comprises 22 parts of isocyanate-terminated polyurethane resin, 6 parts of crosslinking agent, 4 parts of adhesion promoter, 0.1 parts of catalyst, 1 part of dehydrating agent, 6 parts of carbon black, and 60.9 parts of a first solvent; the crosslinking agent is HDI trimer, the adhesion promoter is 3-glycidyl etheroxypropyltrimethoxysilane, the catalyst is dibutyltin dilaurate, the dehydrating agent is p-toluenesulfonyl isocyanate, the carbon black is SB250 carbon black, and the first solvent is ethyl acetate.

[0062] The preparation of the terminal isocyanate polyurethane resin includes: placing 100 parts by mass of polyester diol HDPOL-310P (number average molecular weight of 1000, water content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 40 parts by mass of MDI, maintaining the temperature until NCO reaches 2.10%, removing the solvent by vacuum distillation, and obtaining the terminal isocyanate polyurethane resin.

[0063] The preparation of the fluorescent polyurethane primer includes: grinding 22 parts by weight of isocyanate-terminated polyurethane resin, 6 parts of HDI trimer, 4 parts of 3-glycidyl etheroxypropyltrimethoxysilane, 0.1 parts of dibutyltin dilaurate, 1 part of p-toluenesulfonyl isocyanate, 6 parts of SB250 carbon black, and 60.9 parts of ethyl acetate in a ball mill for 8 hours to prepare the fluorescent polyurethane primer, which is then sealed and stored for later use.

[0064] Comparative Example 2 This comparative example provides a fluorescent polyurethane primer, which, by mass, comprises 22 parts isocyanate-terminated polyurethane resin, 6 parts crosslinking agent, 4 parts adhesion promoter, 2 parts hydrogen-free fluorescent agent, 0.1 parts catalyst, 1 part dehydrating agent, 6 parts carbon black, and 58.9 parts solvent. The crosslinking agent is HDI trimer, the adhesion promoter is 3-glycidyl etheroxypropyltrimethoxysilane, the hydrogen-free fluorescent agent is 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, the catalyst is dibutyltin dilaurate, the dehydrating agent is p-toluenesulfonyl isocyanate, the carbon black is SB250 carbon black, and the solvent is ethyl acetate.

[0065] The preparation of the terminal isocyanate polyurethane resin includes: placing 100 parts by mass of polyester diol HDPOL-310P (number average molecular weight of 1000, water content ≤300ppm) and 100 parts by mass of ethyl acetate in a reactor, heating to 65°C, adding 40 parts by mass of MDI, maintaining the temperature until NCO reaches 2.10%, removing the solvent by vacuum distillation, and obtaining the terminal isocyanate polyurethane resin.

[0066] The preparation of the fluorescent polyurethane primer includes: grinding 22 parts by weight of isocyanate-terminated polyurethane resin, 6 parts of HDI trimer, 4 parts of 3-glycidyl etheroxypropyltrimethoxysilane, 2 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, 0.1 parts of dibutyltin dilaurate, 1 part of p-toluenesulfonyl isocyanate, 6 parts of SB250 carbon black, and 60.9 parts of ethyl acetate in a ball mill for 8 hours to obtain the fluorescent polyurethane primer, which is then sealed and stored for later use.

[0067] The fluorescent polyurethane primers prepared in Examples 1-15 and Comparative Examples 1-2 were subjected to peel adhesion, tensile shear, fluorescence, and aging resistance tests. The test conditions and methods are as follows: (1) Peel adhesion: Tested according to DVS 1618-2002 Elastic thick film adhesion in rail locomotives and rolling stock.

[0068] The specific implementation steps are as follows: First, thoroughly clean the substrate surface with a cleaning agent and let it dry. Then, use a brush to evenly apply a layer of primer to the substrate surface. After the primer is completely dry, use a glue gun to apply 5 polyurethane adhesive strips with a width of about 10 mm and a length of at least 50 mm to the substrate surface with the primer applied. Place the substrate with the adhesive strips in standard conditions (23℃ / 50%RH) for 7 days. After 7 days of curing, use a knife to cut the adhesive strips to the adhesion surface, and at the same time, use needle-nose pliers to peel off the adhesive (peeling angle 130~160°). During the peeling process, make transverse cuts to the adhesion surface every 5~10 mm, with a cutting interval of about 3 seconds. Continue to apply load to the material. The test length is at least 50 mm. The test sample adhesive is a single-component moisture-curing polyurethane adhesive with a shear strength of about 6.0 MPa.

[0069] (2) Tensile shear: The test shall be conducted in accordance with GB / T 7124-2008 Determination of tensile shear strength of adhesives (rigid material to rigid material)

[0070] (3) Fluorescence: After cleaning and drying the substrate surface, apply a layer of primer evenly to the substrate surface with a brush, and then observe the fluorescence of the substrate surface under a UV lamp.

[0071] (4) Aging resistance: Tested in accordance with QC / T 1024-2015 Single-component polyurethane sealant for automobiles.

[0072] The primers prepared in Examples 1-15 and Comparative Examples 1-2 were tested for peel adhesion, tensile shear, fluorescence, and aging resistance. The results are shown in Table 2 below.

[0073] Table 2 Performance test results of the examples and comparative examples

[0074] Note: CF indicates cohesion failure.

[0075] Continued from Table 2

[0076] Note: CF indicates cohesion failure.

[0077] Continued from Table 2

[0078] Note: CF indicates cohesion failure.

[0079] Please refer to the test results in Table 2 for details. As can be seen from the comparison between Examples 1-15 and Comparative Examples 1-2, the shear strength of the fluorescent polyurethane primer of the present invention is above 5.88 MPa, which indirectly proves that it has better adhesion performance, and its heat resistance (120℃ / 3h, 90℃ / 300h), water resistance (40℃ / 72h), and damp heat resistance (70℃ / 95%RH / 300h) are even better. In Comparative Example 1, no fluorescent molecules were introduced; only 3-glycidyl etheroxypropyltrimethoxysilane was used as a bonding promoter. Its tensile shear properties and aging resistance were significantly worse than those of Examples 1-15. This indicates that the fluorescent modified bonding promoter of the present invention, in addition to providing fluorescent properties, can effectively improve the tensile shear properties and aging resistance of the primer system of the present invention. In Comparative Example 2, 3-glycidyl etheroxypropyltrimethoxysilane was used as a bonding promoter, and 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene was used as a fluorescent agent. The tensile shear properties and aging resistance of the prepared primer were significantly worse than those of Examples 1-15. This may be because the fluorescent agent molecule does not contain curing crosslinking groups (such as isocyanate groups) in its structure, resulting in poor compatibility with terminal isocyanate polyurethane resins. It only undergoes simple physical mixing with other components in the primer and cannot form strong chemical bonds with the substrate. During testing (especially aging resistance testing), migration occurs, leading to structural instability of the primer and thus affecting its performance.

[0080] Furthermore, a comparison between Examples 1 and 2 shows that the fluorescent modified adhesive accelerator prepared using 6-carboxycoumarin as a raw material can give the primer superior shear strength and aging resistance. A comparison between Examples 1 and 3 shows that using β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane as the raw material for preparing the fluorescent modified adhesive accelerator results in a primer with better aging resistance. This may be because β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane has a saturated cyclic structure and does not contain ether bonds, giving it superior properties compared to γ-glycidoxypropyltrimethoxysilane. The fluorescent modified adhesive exhibits superior heat resistance, water resistance, and damp heat resistance. A comparison between Examples 1 and 4-5, and between Examples 1 and 9-10, shows that when triphenyl triisocyanate thiophosphate or triphenylmethane triisocyanate is used as a raw material for preparing the fluorescent modified adhesive accelerator or as a crosslinking agent in the primer, it exhibits superior shear strength, heat resistance, water resistance, and damp heat resistance compared to HDI trimer. A comparison between Examples 1 and 6-7 shows that when phthalic anhydride polyester diol is used as a raw material for preparing the isocyanate-terminated polyurethane resin, it exhibits superior shear strength, heat resistance, water resistance, and damp heat resistance. A comparison between Examples 9, 13, and 15 shows that when the mass fraction of the fluorescent modified adhesive accelerator or the isocyanate-terminated polyurethane resin is small, the cohesive breakdown in water resistance and damp heat resistance deteriorates to some extent.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A fluorescent polyurethane primer, characterized in that, The raw materials for preparation, by mass, include 14-30 parts of terminal isocyanate polyurethane resin, 4-8 parts of crosslinking agent, 2-8 parts of fluorescent modified adhesive accelerator, 0.05-0.2 parts of catalyst, 0.5-2 parts of dehydrating agent, 4-8 parts of carbon black and 50-75 parts of first solvent; The isocyanate-terminated polyurethane resin is prepared by reacting diisocyanate and polyester diol. The fluorescent modified adhesive promoter is prepared by reacting a hydroxyl-containing fluorescent modified silane coupling agent with triisocyanate. The hydroxyl-containing fluorescent modified silane coupling agent is prepared by reacting a fluorescent compound containing active hydrogen with an epoxy-containing silane coupling agent. The molar ratio of hydroxyl groups in the hydroxyl-containing fluorescent modified silane coupling agent to isocyanate groups in the triisocyanate is 1.0~1.8:3.

0.

2. The fluorescent polyurethane primer according to claim 1, characterized in that, The molar ratio of the active hydrogen in the fluorescent compound containing active hydrogen to the epoxy group in the silane coupling agent containing epoxy group is 1:

1.

3. The fluorescent polyurethane primer according to claim 1, characterized in that, The molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the polyester diol is 1.4~1.8:

1.

4. The fluorescent polyurethane primer according to claim 1, characterized in that, The fluorescent compound containing active hydrogen is selected from at least one of 3-carboxycoumarin, 4-carboxycoumarin, 6-carboxycoumarin, 7-hydroxycoumarin-3-carboxylic acid, 7-methoxycoumarin-3-carboxylic acid, 8-bromo-3-carboxycoumarin, rhodamine B, fluorescein, fluorescein derivatives, 4-aminophthalimide, and fluorescein amine.

5. The fluorescent polyurethane primer according to claim 1, characterized in that, The epoxy-containing silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

6. The fluorescent polyurethane primer according to claim 1, characterized in that, The triisocyanate is selected from at least one of HDI trimer, TDI trimer, IPDI trimer, triphenyl triisocyanate thiophosphate, and triphenylmethane triisocyanate.

7. The fluorescent polyurethane primer according to claim 1, characterized in that, The polyester diol is selected from at least one of phthalic anhydride polyester diol, polycarbonate diol, and polycaprolactone diol, and the diisocyanate is selected from at least one of TDI, MDI, HDI, IPDI, NDI, and XDI.

8. The fluorescent polyurethane primer according to claim 1, characterized in that, The crosslinking agent is selected from at least one of HDI trimer, TDI trimer, IPDI trimer, triphenyl triisocyanate thiophosphate, and triphenylmethane triisocyanate; the catalyst is selected from at least one of organotin catalysts and titanate catalysts; and the first solvent is selected from at least one of ethyl acetate, butyl acetate, acetone, butanone, and xylene.

9. A method for preparing a fluorescent polyurethane primer according to any one of claims 1 to 8, characterized in that, include: (1) Preparation of fluorescent modified adhesion promoter The fluorescent compound containing active hydrogen, the silane coupling agent containing epoxy group, triethylamine, and a second solvent are placed in a reactor and reacted until the infrared peak of the epoxy group disappears to obtain the fluorescent modified silane coupling agent containing hydroxyl group. Then, the triisocyanate is added and reacted until NCO reaches the theoretical value. (2) Preparation of isocyanate-terminated polyurethane resin The dehydrated polyester diol, the diisocyanate, and the third solvent are placed in a reactor and reacted until NCO reaches the theoretical value. (3) Preparation of fluorescent polyurethane primer The formulated amounts of the terminal isocyanate polyurethane resin, the crosslinking agent, the fluorescent modified adhesive accelerator, the catalyst, the dehydrating agent, the carbon black, and the first solvent are placed in a ball mill and ground.

10. The application of a fluorescent polyurethane primer prepared according to any one of claims 1 to 8 or according to the preparation method of the fluorescent polyurethane primer according to claim 9 in automotive glass installation.

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