Dual-cure polyisocyanate composition, process for its preparation and use

Abstract

The present application relates to a kind of dual-curing type polyisocyanate composition and preparation method and use.The polyisocyanate composition includes the product containing isocyanurate structure formed by the reaction of aliphatic diisocyanate and 3-isopropyl-dimethyl benzyl isocyanate, and it at least includes two isocyanurate mononuclears.The polyisocyanate composition prepared by the present application has UV-thermal dual-curing characteristics, product viscosity is low, heat storage stability is good and the like, and manufacturing process is simple, especially suitable for the protection of line board or 3C electronic product field.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a dual-curing polyisocyanate composition, its preparation method, and its uses. Background Technology

[0002] In recent years, UV-curable resins have experienced rapid growth due to their environmentally friendly and energy-efficient characteristics, resulting in an increasingly larger market share. Polyurethane acrylate (PUA) is a common and widely used UV-curable resin that combines the properties of both polyurethane and acrylate. It boasts high curing speed, good adhesion, flexibility, abrasion resistance, temperature resistance, and outstanding elasticity and elongation. These resins are widely used in metal, wood, and plastic coatings, ink printing, fabric printing, and optical fiber coating, demonstrating their broad application prospects and excellent performance. Aliphatic polyurethane acrylates, in particular, exhibit superior weather resistance compared to aromatic resins. However, the high viscosity of traditional polyurethane acrylates is due to the presence of numerous -NHCOO- groups in their molecular structure, which contribute to their excellent curing properties. To reduce the viscosity of the formulation, a large amount of reactive diluent is required. Especially in the UV curing field, excessive diluent introduction can negatively impact the product's shrinkage rate and thermal storage stability. CN114163972A and CN102498164A disclose compounds containing both isocyanate groups and double bonds that can be polymerized on free radicals. These compounds are first obtained by dimerizing or trimerizing industrially common aliphatic isocyanates to form urea diketones or isocyanurate counterparts, and then by reacting these counterparts with (meth)acrylate hydroxy esters. The advantage of this system is that it avoids the risk of polymerization during the removal of free monomers. However, they often have very high viscosity and require a large amount of solvent for dilution before use. Moreover, they are prone to turbidity or crystallization due to the precipitation of urethane during low-temperature storage. CN107629189A discloses a low-viscosity polyurethane acrylate oligomer. The prepared product has good weather resistance and compatibility, and the curing speed of the product is significantly improved. However, the product prepared by this method does not contain free NCO groups. All NCO groups are reacted during the preparation process, resulting in a still high viscosity of the product, and strictly speaking, it no longer possesses the dual-curing characteristics. CN115466568A discloses a UV / moisture dual-curing protective coating, its preparation method, and its application. This method directly uses TDI or MDI as raw materials to react with polypropylene glycol and HEMA. The product contains a large amount of urethane structure and a large amount of free TDI or MDI, which poses a significant challenge to the product's thermal storage stability and environmental hazards.

[0003] In some applications and under certain conditions, UV-cured acrylic coatings or polyurethane-modified acrylic copolymer coatings may experience polymerization inhibition during the curing process due to contact with oxygen in the air, or uneven surfaces may prevent certain areas from receiving UV light. This can lead to incomplete curing of the coating surface or even the entire coating, severely impacting the performance of the protective coating. Therefore, developing isocyanate compositions with dual curing properties has been a pressing issue for the industry, especially isocyanate products that simultaneously possess low viscosity and good thermal storage stability. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the deficiencies of the prior art and provide a polyisocyanate composition that not only ensures the product has dual curing characteristics, but also has the characteristics of low viscosity, good thermal storage stability and good application performance.

[0005] This invention is achieved through the following technical solution:

[0006] A polyisocyanate composition comprising a product containing an isocyanurate structure formed by reacting an aliphatic diisocyanate with 3-isopropyl-dimethylbenzyl isocyanate, and the composition comprising two isocyanurate mononuclear forms of structure (I) and structure (II):

[0007]

[0008] In formulas (I) and (II) above, R1 is the residual group of the aliphatic diisocyanate after removing the isocyanate group.

[0009] The polyisocyanate composition of this invention uses aliphatic diisocyanates because the aliphatic isocyanate structure itself has good weather resistance and moderate reactivity. Through a unique isocyanurate polymerization process, the inventors surprisingly discovered that, on the one hand, direct polymerization of the urea ring of traditional isocyanates introduces double-bonded groups, forming a six-membered ring structure with good mechanical properties and thermal stability, while avoiding the introduction of thermally unstable urethane structures. On the other hand, the moderate increase in the asymmetric structure formed by the aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate results in a product with good operating viscosity, avoiding or reducing the amount of solvent or reactive diluent used.

[0010] In addition, it was unexpectedly discovered that the cross-polymerization reaction of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate resulted in a certain amount of isocyanurate mononuclear structure with double bond groups in the reaction system. Compared with the prior art, this composition not only has highly adjustable UV-thermal dual curing characteristics, but also avoids the introduction of thermally unstable carbamate or urethane structures, thus ensuring good storage stability.

[0011] In one embodiment of the present invention, the polyisocyanate composition comprises an aliphatic diisocyanate oligomer, two isocyanurate mononuclear molecules, a free aliphatic diisocyanate monomer, and a free 3-isopropyl-dimethylbenzyl isocyanate; preferably, the ratio of structure (I) to structure (II) of the isocyanurate mononuclear molecules is (10-50):100, more preferably (15-40):100; preferably, the sum of the contents of the free aliphatic diisocyanate monomer and the free 3-isopropyl-dimethylbenzyl isocyanate monomer is less than 0.5% based on the total mass of the composition.

[0012] In one embodiment of the present invention, the aliphatic diisocyanate is selected from any carbon number between C4 and C5 containing two terminal isocyanate groups, wherein the isocyanate groups are not directly connected to the benzene ring. 30 The compound is preferably at least one of pentamethylene diisocyanate, hexamethylene diisocyanate, phenyl diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and methylcyclohexyl diisocyanate, and more preferably one or more of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0013] Another object of the present invention is to provide a method for preparing a polyisocyanate composition.

[0014] A method for preparing a polyisocyanate composition, wherein the composition is the above-mentioned polyisocyanate composition, the preparation method comprising the following steps:

[0015] Aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate react under catalytic conditions, the reaction is terminated to obtain a solution of isocyanate mixture, unreacted aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate are removed to obtain the target polyisocyanate composition.

[0016] In one embodiment of the present invention, the reaction temperature is 45-100°C.

[0017] In one embodiment of the present invention, the catalyst is a catalyst capable of simultaneously catalyzing the reaction of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate to form structure I and structure II, preferably an organic amine compound and / or an organophosphorus compound, more preferably one or more of trimethylhydroxyethylammonium, triethylhydroxypropylammonium, tetramethylammonium acetate, tetrabutylammonium acetate, tetramethylammonium propionate, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriphenylphosphine chloride, and 2,4,6-tris(dimethylaminomethyl)phenol; preferably, the amount of catalyst added is 20-1500 ppm based on the total mass of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate.

[0018] Optionally, in order to make the reaction process have good reaction selectivity and high catalytic activity, a co-catalyst may be added. The co-catalyst is not particularly limited, but preferably has good inducing activity for hybrid polymerization processes, such as one or more of five- or six-membered heterocyclic organic compounds containing nitrogen, phosphorus, oxygen or sulfur atoms, preferably one or more of pyrazole, imidazole, pyrrole, thiophene, furan, pyridine or pyridazine.

[0019] Optionally, in order to reduce the tendency of the system to gel due to the free radical polymerization of 3-isopropyl-dimethylbenzyl isocyanate itself, a free radical polymerization inhibitor can be added. The free radical polymerization inhibitor is not particularly limited and can be at least one of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, phenothiazine, and p-benzoquinone, with phenothiazine being preferred.

[0020] In one embodiment of the present invention, the termination reaction is achieved by adding a terminator; preferably, the reaction is terminated when the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reaches 20-60%, more preferably 25-50%. The terminator is an acidic compound, preferably at least one selected from dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, 2-ethylhexyl phosphate, phosphoric acid, hydrochloric acid, benzenesulfonic acid, p-toluenesulfonic acid, benzoyl chloride, and acetyl chloride. The terminator and its method of use are techniques commonly used in the art.

[0021] Another object of the present invention is to provide a use of a polyisocyanate composition.

[0022] Use of a polyisocyanate composition, wherein the composition is the polyisocyanate composition described above, or a composition prepared by the preparation method described above, wherein the composition is used in coatings or adhesives, preferably in two-component coatings having dual curing properties, and more preferably in coatings on circuit boards or plastic substrates.

[0023] Another object of the present invention is to provide a curing agent with dual curing properties.

[0024] A curing agent with dual curing properties, wherein the curing agent is the above-described polyisocyanate composition, or a composition prepared by the above-described preparation method, wherein the curing agent contains a polyisocyanate composition.

[0025] Another object of the present invention is to provide a two-component coating with dual curing properties.

[0026] A two-component coating with dual curing properties, wherein the coating uses the above-mentioned polyisocyanate composition, or a composition prepared by the above-mentioned preparation method, or uses the above-mentioned curing agent, wherein the coating uses the polyisocyanate composition as the curing agent component.

[0027] The method for preparing two-component coatings from polyisocyanates is well known to those skilled in the art. This method primarily uses polyisocyanates as curing agents, polyester polyols containing active hydrogen or hydroxyl acrylic resins as main agents, and selectively adds certain functional additives and active monomers according to actual needs to produce a two-component curing product. The present invention preferably uses the following method to prepare a UV-thermal curable two-component coating from a polyisocyanate composition: At 15-35°C and relative humidity below 40%, select weights of hydroxyl acrylic resin, n-butyl acetate, trimethylolpropane triacrylate, photoinitiator, and other coating additives are added to a mixing container. After mechanical stirring and mixing evenly, the prepared polyisocyanate composition is added according to an NCO / OH ratio of 1.01-1.08. The mixture is mechanically stirred for 3-8 minutes to ensure uniform mixing. Vacuuming is then performed at room temperature to remove air bubbles, resulting in a UV-thermal dual-curable polyurethane coating.

[0028] The additives may be one or a mixture of any of the following: defoamers, wetting agents, dispersants, leveling agents, silane coupling agents, etc.

[0029] Unless otherwise specified, all percentages in this invention are in wt%.

[0030] Unless otherwise specified, the inert gas is preferably nitrogen.

[0031] The technical solution provided by this invention has the following beneficial effects:

[0032] The products prepared using this technical solution can significantly improve the product's fast-drying performance and application performance while ensuring that the final composition has a relatively low operating viscosity. In particular, the improvement is significant in high-temperature and high-humidity hydrolysis resistance and damp heat aging resistance. Therefore, it is especially suitable for applications requiring dual curing, such as circuit boards and 3C electronic plastic substrates. Detailed Implementation

[0033] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0034] The raw materials used in the following embodiments and comparative examples of this invention and their sources are as follows:

[0035] Isophorone diisocyanate (IPDI) was purchased from Wanhua Chemical Group Co., Ltd.

[0036] Hexamethylene diisocyanate (HDI) was purchased from Wanhua Chemical Group Co., Ltd.

[0037] Hexamethylene diisocyanate trimer (HT-100), an aliphatic isocyanurate, was purchased from Wanhua Chemical Group Co., Ltd.

[0038] Phenothiazine, a polymerization inhibitor, was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0039] UV-1173, a photoinitiator, was purchased from Jiangxi Lote Chemical Co., Ltd.

[0040] 3-Isopropyl-dimethylbenzyl isocyanate (TMI), a specialty isocyanate, purchased from Merck Chemicals AG;

[0041] AC1260, hydroxyl acrylic resin, is a commonly used resin in polyurethane two-component varnishes, purchased from Foshan Gaoming Tongde Chemical Co., Ltd.

[0042] BYK306, a commonly used leveling agent in polyurethane coatings, was purchased from BYK Chemical AG, Germany.

[0043] Imidazole, a co-catalyst, was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0044] Unless otherwise specified, all contents in this invention refer to mass content.

[0045] The relevant test methods in the following embodiments and comparative examples of this invention are as follows:

[0046] (1) The NCO content test shall be performed in accordance with standard GB / T 12009.4;

[0047] (2) Viscosity testing shall be performed according to the dynamic viscosity at 25°C using a slab viscometer (Brookfield DT-2);

[0048] (3) The method for analyzing the mononuclear structure of isocyanurate is as follows:

[0049] Using an AVANCE 600 FT-NMR spectrometer manufactured by Bruker, with deuterated chloroform (CDCl3) as solvent, and at a sample concentration of 5% (mass concentration of the prepared isocyanurate product), the NMR was performed at 600 MHz for 48 hours. 13 Qualitative analysis using C10 NMR spectroscopy revealed that the characteristic shifts of the six-membered ring isocyanurate structure I, prepared using hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate as bases, were approximately δ148.3 ppm, δ150.7 ppm, and δ150.7 ppm, respectively. Structure II, a standard six-membered ring isocyanurate structure, showed characteristic shifts of approximately δ148.5 ppm for the C10 NMR spectroscopy of structure II prepared using hexamethylene diisocyanate as a raw material.

[0050] (4) The method for determining the ratio of isocyanurate mononuclear structures (I) / (II) is as follows: The terminal isocyanate group in the polyisocyanate composition is derivatized with methanol and analyzed by liquid chromatography-mass spectrometry (LC / MS). The preparation and testing methods are as follows:

[0051] (a) Sample preparation method: Weigh a quantitative amount of polyisocyanate composition and dilute it with an excess of stoichiometric methanol. Allow the mixture to stand for three days to allow the isocyanate groups to react completely with the methanol, thereby preparing a methanol-derived solution.

[0052] (b) Measurement method:

[0053] The methanol-derived solution obtained above was measured using the following apparatus.

[0054] Agilent LC (Liquid Chromatograph), Agilent 1100 series

[0055] Column: Phenomenex, Kinetex 2.6μXB-C18 100A (inner diameter 2.1mm, length 50mm)

[0056] Column temperature: 40℃

[0057] Detection: 205nm

[0058] Flow rate: 0.35 mL / mins

[0059] Mobile phase: a gradient between solutions A and B, where A = water (0.05% formic acid) and B = methanol.

[0060] Injection volume: 2μL

[0061] Thermo MS (mass spectrometer)

[0062] Device: Thermo Electron, LCQ

[0063] Ionization: APCI

[0064] Mode: Positive ion

[0065] Scan range: m / z 150~2000.

[0066] The ratio of the methanol adduct of structure (I) to the methanol adduct of structure (II) is taken as the ratio of isocyanurate mononuclear structure (I) / (II).

[0067] (5) The sum of the contents of free aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was tested using high performance liquid chromatography (HPLC) to establish an external standard curve. The key parameters are as follows:

[0068] Column: Waters XSelect HSS T3 5um 4.6*250mm;

[0069] Automated Sampler: SIL-20A

[0070] Column temperature: 40℃

[0071] Injection volume: 10 μL

[0072] Detection wavelength: 281nm

[0073] Derivatizing reagent: 4% 1-methoxyphenylpiperazine-acetonitrile solution.

[0074] The concentrations of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were determined separately based on their respective peak areas and external standard curves. The sum of these two concentrations was then used as the total monomer content of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate in the polyisocyanate composition.

[0075] (6) Thermal storage stability of polyisocyanates: The isocyanate composition sample was placed in a 120ml brown glass bottle with a ground glass stopper, and the air atmosphere was replaced with nitrogen. After replacement, it was sealed and stored at 80°C. The viscosity growth rate was tested after 30 days.

[0076] Evaluation criteria: A viscosity growth rate of <10% indicates excellent thermal storage stability;

[0077] If the viscosity growth rate is less than 20% and the growth rate is less than 10%, the thermal storage stability is rated as good.

[0078] If the viscosity growth rate is greater than 20%, its thermal storage stability is rated as poor.

[0079] Preparation of polyisocyanate compositions.

[0080] Example 1

[0081] Under an inert gas atmosphere, 500g of hexamethylene diisocyanate and 200g of 3-isopropyl-dimethylbenzyl isocyanate were weighed into a reaction vessel and heated to 80°C. Then, 0.07g of phenothiazine was added and stirred until evenly dispersed. Next, 0.32g of tetrabutylammonium hydroxide catalyst and 0.10g of imidazole were added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reached 20%. The reaction was terminated by adding 0.1g of dibutyl phosphate to obtain an isocyanate mixture solution. Unreacted hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were further removed by thin-film distillation under conditions of 150°C and vacuum <500Pa. Analysis showed that the NCO content was 18.2%, the viscosity was 4810 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 15.1%, the sum of the contents of free hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.32%, and the thermal storage stability of the polyisocyanate composition was rated as excellent.

[0082] Example 2

[0083] Under an inert gas atmosphere, 500g of hexamethylene diisocyanate and 400g of 3-isopropyl-dimethylbenzyl isocyanate were weighed into a reaction vessel and heated to 60°C. Then, 0.09g of phenothiazine was added and stirred until evenly dispersed. Next, 0.32g of tetrabutylammonium hydroxide catalyst and 0.35g of imidazole were added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reached 50%. The reaction was terminated by adding 0.2g of dibutyl phosphate to obtain an isocyanate mixture solution. Unreacted hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were further removed by thin-film distillation under conditions of 150°C and vacuum <500Pa. Analysis showed that the NCO content was 15.1%, the viscosity was 6891 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 44.5%, the sum of the contents of free hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.35%, and the thermal storage stability of the polyisocyanate composition was rated as excellent.

[0084] Example 3

[0085] Under an inert gas atmosphere, 500g of isophorone diisocyanate and 200g of 3-isopropyl-dimethylbenzyl isocyanate were weighed into a reaction vessel and heated to 80°C. Then, 0.07g of phenothiazine was added and stirred until evenly dispersed. Next, 0.45g of tetrabutylammonium hydroxide catalyst and 0.25g of imidazole were added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reached 35%. The reaction was terminated by adding 0.2g of dibutyl phosphate to obtain an isocyanate mixture solution. Unreacted isophorone diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were further removed by thin-film distillation under conditions of 150°C and vacuum <500Pa. Analysis showed that the NCO content was 15.7%, the viscosity was 11326 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 25.6%, the sum of the contents of free isophorone diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.43%, and the thermal storage stability of the polyisocyanate composition was rated as excellent.

[0086] Example 4

[0087] Under an inert gas atmosphere, 500 g of hexamethylene diisocyanate and 100 g of 3-isopropyl-dimethylbenzyl isocyanate were weighed into a reaction vessel and heated to 80 °C. Then, 0.06 g of phenothiazine was added and stirred until evenly dispersed. Next, 0.40 g of trimethylhydroxyethylammonium catalyst and 0.10 g of imidazole were added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reached 35%. The reaction was terminated by adding 0.2 g of dioctyl phosphate to obtain an isocyanate mixture solution. Unreacted hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were further removed by thin-film distillation under conditions of 150 °C and vacuum degree <500 Pa. Analysis showed that the NCO content was 18.9%, the viscosity was 3798 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 11.2%, the sum of the contents of free hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.12%, and the thermal storage stability of the polyisocyanate composition was rated as excellent.

[0088] Comparative Example 1

[0089] Comparative Example 1 differs from Example 4 above only in that it is a product with dual curing properties prepared without diisocyanate monomers, and therefore contains only Structure II but not Structure I.

[0090] The preparation method of this comparative polyisocyanate composition includes the following steps: Under an inert gas atmosphere, 500g of hexamethylene diisocyanate trimer (HT-100) and 100g of 3-isopropyl-dimethylbenzyl isocyanate are weighed into a reaction vessel, heated to 80°C, and directly blended for modification. Then, 0.06g of phenothiazine is added and stirred to disperse evenly, so that it meets the requirements of dual curing characteristics. After analysis, the NCO content is 21.8%, the viscosity is 489cP / 25°C, the ratio of isocyanurate mononuclear structure (I) to structure (II) is 0, and the thermal storage stability of the polyisocyanate composition is evaluated as poor.

[0091] Comparative Example 2

[0092] Compared with Example 2, the only difference is that the amount of 3-isopropyl-dimethylbenzyl isocyanate added is increased.

[0093] The preparation method of this comparative polyisocyanate composition includes the following steps: Under an inert gas atmosphere, 500g of hexamethylene diisocyanate and 700g of 3-isopropyl-dimethylbenzyl isocyanate are weighed into a reaction vessel and heated to 60°C. Then, 0.09g of phenothiazine is added and stirred to disperse evenly. Next, 0.32g of tetrabutylammonium hydroxide catalyst and 0.35g of imidazole are added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reaches 50%. The reaction is terminated by adding 0.2g of dibutyl phosphate to obtain an isocyanate mixture solution. Further, unreacted hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate are removed by thin-film distillation under conditions of 150°C and vacuum degree <500Pa. Analysis showed that the NCO content was 12.2%, the viscosity was 8691 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 65.7%, the sum of the contents of free hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.22%, and the thermal storage stability of the polyisocyanate composition was rated as good.

[0094] Comparative Example 3

[0095] Compared with Example 4, the only difference is the reduction in the amount of 3-isopropyl-dimethylbenzyl isocyanate added.

[0096] Under an inert gas atmosphere, 500 g of hexamethylene diisocyanate and 30 g of 3-isopropyl-dimethylbenzyl isocyanate were weighed into a reaction vessel and heated to 80 °C. Then, 0.06 g of phenothiazine was added and stirred until evenly dispersed. Next, 0.40 g of trimethylhydroxyethylammonium catalyst and 0.10 g of imidazole were added to carry out a trimerization reaction until the conversion rate of 3-isopropyl-dimethylbenzyl isocyanate reached 35%. The reaction was terminated by adding 0.2 g of dioctyl phosphate to obtain an isocyanate mixture solution. Unreacted hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate were further removed by thin-film distillation under conditions of 150 °C and vacuum degree <500 Pa. Analysis showed that the NCO content was 19.8%, the viscosity was 3489 cP / 25℃, the ratio of isocyanurate mononuclear structure (I) to structure (II) was 2.8%, the sum of the contents of free hexamethylene diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate monomers was 0.11%, and the thermal storage stability of the polyisocyanate composition was rated as excellent.

[0097] Examples of applications of polyisocyanate compositions.

[0098] Using the above-mentioned polyisocyanate composition as raw material, a UV-thermal curable two-component coating was prepared according to the following process: At 25°C and with a relative humidity of less than 40%, 50 parts of hydroxyl acrylic resin AC-1260, 45 parts of butyl acetate, 5 parts of trimethylolpropane triacrylate, 150 ppm of photoinitiator UV-1173, and 50 ppm of BYK306 were added to a mixing container. After mechanical stirring and mixing evenly, the above-prepared polyisocyanate composition was added according to an NCO / OH ratio of 1.05. The mixture was mechanically stirred for 5 minutes to ensure uniform mixing. The air bubbles were removed by vacuuming at room temperature to obtain a UV-thermal dual-curable polyurethane coating.

[0099] The coating composition obtained above was uniformly sprayed onto circuit boards, PET films, and tetrafluoroethylene molds, respectively, and then cured in a UV curing machine for 10 seconds. The UV curing machine used in the experiment had a main wavelength of 365nm and a power density of 60W / cm². 2 After UV curing, the sample is placed at 50℃ for 3 hours to achieve complete curing, thus obtaining the test sample for performance testing.

[0100] (1) The surface drying time shall be tested in accordance with GB / T 1728-2020.

[0101] (2) High temperature and high humidity hydrolysis resistance test: The test sample was cut into 15mm*200mm pieces, placed in a pressure cooker, and treated at 120℃ and 0.1Mpa for 25 hours. After taking it out, it was aged at room temperature for 1 day. Then, a tensile strength tester was used to perform a 180° peel test at a test speed of 50mm / min.

[0102] Evaluation criteria: Peel strength ≥10N / 15mm is considered excellent;

[0103] A peel strength of 6N / 15mm ≤ peel strength ≤ 10N / 15mm is considered good.

[0104] A peel strength of 1N / 15mm ≤ peel strength ≤ 6N / 15mm is considered poor.

[0105] (3) Weather resistance test: The test sample was cut into 50mm*150mm pieces, and the composite layer was accelerated aging test using a xenon lamp weather resistance tester. The appearance after light aging was observed according to ASTM G155 standard.

[0106] Evaluation criteria: No change is considered excellent;

[0107] Slight discoloration or cracks are acceptable;

[0108] Significant discoloration or cracking indicates a poor result;

[0109] (4) Moist heat aging resistance test: Cut the test sample into 15mm*200mm pieces and put them into a high temperature and high humidity test chamber. The test conditions are: humidity 85%, temperature 85℃, time 1000h. Moist heat aging resistance test is carried out. Observe whether the coating layer has powdering, bubbles, etc. At the same time, the adhesion is tested by cross-cut method. 95% or more without peeling is qualified, and the rest are unqualified.

[0110] The performance test results of the coating samples prepared from the polyisocyanate compositions obtained from the examples and comparative examples are shown in Table 1.

[0111] Table 1. Performance test results of test samples prepared from polyisocyanates in the examples and comparative examples.

[0112]

[0113] The macroscopic properties of the polyisocyanate compositions prepared in Examples 1-4 and Comparative Examples 1-3, as well as the performance test results of the products in Table 1, show that the polyisocyanate compositions prepared in Examples 1-4 have relatively low viscosity and excellent thermal storage stability. At the same time, the test samples prepared in Examples 1-4 exhibit excellent performance in terms of hydrolysis resistance and resistance to damp heat aging under high temperature and high humidity, and have the advantage of short surface drying time. However, the polyisocyanates prepared in Comparative Examples 1-4 cannot simultaneously meet the conditions of low viscosity and good overall product performance, and therefore cannot meet the actual needs.

[0114] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polyisocyanate composition, characterized in that, The polyisocyanate composition comprises a product containing an isocyanurate structure formed by reacting an aliphatic diisocyanate with 3-isopropyl-dimethylbenzyl isocyanate, and the composition contains two isocyanurate mononuclear forms, structure (I) and structure (II): In formulas (I) and (II) above, R1 is the residual group of the aliphatic diisocyanate after removing the isocyanate group; The polyisocyanate composition comprises an aliphatic diisocyanate oligomer, two isocyanurate mononuclear molecules, a free aliphatic diisocyanate monomer, and a free 3-isopropyl-dimethylbenzyl isocyanate. Wherein, the ratio of structure (I) to structure (II) of the isocyanurate mononuclear body is (10-50):100; The sum of the contents of free aliphatic diisocyanate monomer and free 3-isopropyl-dimethylbenzyl isocyanate monomer is less than 0.5% based on the total mass of the composition.

2. The polyisocyanate composition according to claim 1, characterized in that, The ratio of structure (I) to structure (II) of the isocyanurate mononuclear body is (15-40):

100.

3. The polyisocyanate composition according to claim 1 or 2, characterized in that, The aliphatic diisocyanate is selected from any carbon number between C4 and C5 containing two terminal isocyanate groups, wherein the isocyanate groups are not directly connected to the benzene ring. 30 Compounds between.

4. The polyisocyanate composition according to claim 3, characterized in that, The aliphatic diisocyanate is selected from at least one of pentamethylene diisocyanate, hexamethylene diisocyanate, phenyl diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and methylcyclohexyl diisocyanate.

5. The polyisocyanate composition according to claim 4, characterized in that, The aliphatic diisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

6. A method for preparing a polyisocyanate composition, wherein the composition is the polyisocyanate composition according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate react under catalytic conditions, the reaction is terminated to obtain a solution of isocyanate mixture, unreacted aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate are removed to obtain the target polyisocyanate composition.

7. The preparation method according to claim 6, characterized in that, The reaction temperature is 45-100℃; And / or, the catalyst is a catalyst capable of simultaneously catalyzing the reaction of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate to form structure I and structure II; And / or, the terminating reaction is terminated by adding a terminating agent.

8. The preparation method according to claim 7, characterized in that, The catalyst is an organic amine compound and / or an organophosphorus compound; The catalyst addition amount is 20-1500 ppm based on the total mass of aliphatic diisocyanate and 3-isopropyl-dimethylbenzyl isocyanate; The reaction is terminated when the conversion of 3-isopropyl-dimethylbenzyl isocyanate reaches 20-60%.

9. The preparation method according to claim 8, characterized in that, The catalyst is one or more of the following: trimethylhydroxyethylammonium, triethylhydroxypropylammonium, tetramethylammonium acetate, tetrabutylammonium acetate, tetramethylammonium propionate, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriphenylphosphine chloride, and 2,4,6-tris(dimethylaminomethyl)phenol; The reaction was terminated when the conversion of 3-isopropyl-dimethylbenzyl isocyanate reached 25-50%.

10. Use of a polyisocyanate composition, said composition being the polyisocyanate composition of any one of claims 1-5, or a composition prepared by any one of claims 6-9, said composition being used in coatings or adhesives.

11. The use according to claim 10, wherein the composition is used in a two-component coating having dual curing properties.

12. The use according to claim 11, wherein the composition is used for coating on a circuit board or a plastic substrate.

13. A curing agent with dual curing properties, said curing agent being a polyisocyanate composition according to any one of claims 1-5, or a composition prepared by any one of claims 6-9, characterized in that, The curing agent contains a polyisocyanate composition.

14. A two-component coating with dual curing properties, said coating comprising a polyisocyanate composition according to any one of claims 1-5, or a composition prepared by any one of claims 6-9, or a curing agent according to claim 13, characterized in that, The coating uses a polyisocyanate composition as a curing agent component.

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