A method for preparing an epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating

Abstract

This invention discloses a method for preparing an epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating. The coating is made from a self-made epoxy-modified polyurethane acrylate prepolymer, a photoinitiator, nano-scale thermally conductive fillers, and an active diluent. By adjusting the formulation of the prepared epoxy-modified polyurethane acrylate, it is made to have both UV and moisture curing methods. The introduction of epoxy groups enhances the mechanical properties and adhesion to the substrate of the coating. The addition of nano-scale thermally conductive fillers ensures both good thermal conductivity and light transmittance. The coating prepared by this method has the following characteristics: good mechanical properties, good adhesion to the substrate, dual UV / moisture curing methods, and high thermal conductivity. The preparation method of the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating disclosed in this invention can be applied to coating, encapsulation, and bonding of electronic materials.

Description

Technical Field

[0001] This invention discloses a method for preparing an epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating. It relates to the technical fields of thermally conductive materials and photocurable materials. Background Technology

[0002] Photocurable coatings are a new type of solvent-free coating composed of prepolymers, reactive diluent monomers, photoinitiators, and additives. Because of their special functional groups, under ultraviolet light irradiation and catalysis by the photoinitiator, the energy of ultraviolet light initiates a polymerization reaction between the prepolymer and reactive diluent monomer molecules, hence the name photocurable coatings. They offer advantages such as high efficiency, no pollution, and energy saving, and are widely used in optoelectronics and electrical engineering packaging.

[0003] In practical applications of UV-cured coatings in fields such as electrical and electronic engineering, there may be shaded areas that cannot be reached by ultraviolet light. The coating in these shaded areas cannot be fully cured. Therefore, while retaining the advantages of UV curing, the raw materials of the coating have been improved, and UV / moisture dual-curing coatings have emerged. In areas where UV light cannot reach, the coating can react with moisture in the air to cure. UV / moisture dual-curing coatings have solved the problem of the single curing method of traditional coatings, but there are still many performance issues to be resolved.

[0004] For coatings used in the electronics and electrical fields, thermal conductivity is a common requirement. Poor thermal conductivity in materials easily leads to heat accumulation, which not only reduces the lifespan of electronic components but also poses safety hazards to electronic devices in power equipment. Therefore, developing coatings with high thermal conductivity to reduce heat accumulation in electronic components and extend their lifespan is an important goal in the current coating industry.

[0005] The common method to increase thermal conductivity is to add thermally conductive fillers with good thermal conductivity to the material. However, this method of improving thermal conductivity by adding thermally conductive fillers to dual-curing coatings introduces the following problems: 1. Most thermally conductive fillers have a large particle size, which affects the efficiency of photocuring and makes it difficult to cure completely. 2. Thermally conductive fillers have a significant impact on the mechanical properties of the cured coating, with a noticeable decrease in tensile strength and shear strength. 3. Thermally conductive fillers reduce the adhesion of the coating to the substrate, making it prone to problems such as coating breakage and peeling.

[0006] Chinese patent CN111500181A discloses a method for preparing an acrylic-terminated polybutadiene UV moisture-curing adhesive, which solves the curing problem in shaded areas.

[0007] Chinese patent CN107964385A discloses a high thermal conductivity UV-curable adhesive. UV light can cure it quickly in a short time. The thermally conductive filler used has high light transmittance. However, diamond is expensive and not suitable for industrial production. Summary of the Invention

[0008] To address the problem of poor thermal conductivity in coatings used in electronic packaging materials, this invention proposes a method for preparing an epoxy-modified polyurethane UV / moisture dual-curing thermally conductive coating. This invention utilizes the residual NCO in the prepolymer to achieve moisture curing, solving the problem of difficult curing in shaded areas during UV curing in practical applications. The use of nanoscale thermally conductive fillers not only solves the heat accumulation problem caused by poor thermal conductivity but also addresses the issue of filler particles hindering UV light irradiation and affecting curing. Improving the polyurethane acrylate prepolymer with epoxy resin not only optimizes the mechanical properties of the cured coating but also enhances the adhesion of the coating to the substrate through the epoxy groups in the epoxy resin. The epoxy-modified polyurethane UV / moisture dual-curing thermally conductive coating prepared by this invention has the following characteristics: it can be cured by both UV and moisture, possesses good mechanical properties, thermal conductivity, and excellent adhesion to the substrate.

[0009] The technical solution of this invention is as follows:

[0010] An epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating, the formulation of which includes: epoxy-modified polyurethane acrylate prepolymer, reactive diluent, photoinitiator, nano-scale thermally conductive filler, defoamer, and fumed silica.

[0011] The epoxy-modified polyurethane acrylate prepolymer comprises 10-50% by weight, the reactive diluent comprises 20-40% by weight, the photoinitiator comprises 2-5% by weight, the nanoscale thermally conductive filler comprises 20-50% by weight, the defoamer comprises 0.2-0.5% by weight, and the fumed silica comprises 0.1-1% by weight, with the sum of the weight percentages of all components being 100%.

[0012] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: Add an appropriate amount of epoxy resin to a three-necked flask, fix the flask in a heated stirrer, set the temperature to 85℃, and the stirring speed to 100 rpm, and heat and stir for 30 minutes. Add an appropriate amount of isocyanate and catalyst to the three-necked flask, maintain the temperature and stirring speed, and continue stirring for 3 hours. Add an appropriate amount of epoxy resin to the three-necked flask and continue stirring for 3 hours. If the viscosity is too high during stirring, an appropriate amount of reactive diluent can be added to reduce the viscosity. Lower the temperature to 65℃, maintain the stirring speed, add an appropriate amount of end-capping agent, and continue stirring for 3 hours. Cool to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0013] The epoxy resin structure needs to simultaneously satisfy epoxy groups and hydroxyl groups, and can be one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, etc., preferably bisphenol A glycidyl ether, which has the following general formula.

[0014]

[0015] Where n is a natural number from 1 to 1000.

[0016] The polyol is a polyester or polyether diol with a molecular weight of 500-3000, and may be one or more of polytetrahydrofuran diol (PTMEG), polypropylene glycol (PPG1000), and polyester polyols, preferably polyester polyols, having the following general formula:

[0017]

[0018] Where R can be methyl, phenyl, carbon chain, etc., and n is a natural number from 1 to 1000.

[0019] The isocyanate is a diisocyanate, which may be one or more of isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), and hexamethylene diisocyanate (HDI), preferably IPDI. The isocyanate has the following general structural formula:

[0020] OCRCO

[0021] R can be a benzene ring, a carbon chain, or a combination of the two.

[0022] The catalyst is one or more of organobismuth catalysts, organotin catalysts, and organozinc catalysts, preferably dibutyltin dilaurate.

[0023] The reactive diluent is an acrylate with a viscosity-reducing effect and a double bond in its structure. It can be one or more of isobornyl methacrylate (IBOMA), tetrahydrofuran acrylate (THFA), acrylmorpholine (ACMO), etc., preferably IBOMA.

[0024] The capping agent is an acrylic hydroxy ester containing both hydroxyl and carbon-carbon double bonds in its structure. It can be one or more of hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), etc., with HEMA being preferred.

[0025] The NCO content of the prepared polyurethane acrylate prepolymer needs to be a certain residual amount, preferably 4-6 wt%.

[0026] The reaction for preparing epoxy-modified polyurethane acrylate prepolymers has the following general formula:

[0027] Phase 1:

[0028]

[0029] Phase Two:

[0030]

[0031] Phase Three:

[0032]

[0033] The photoinitiator is one or more of diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride (TPO) and diethyl benzoate (BDK), preferably TPO.

[0034] The nanoscale thermally conductive filler is one or more of nanoscale alumina, nanoscale aluminum nitride, and nanoscale aluminum hydroxide, preferably nanoscale alumina.

[0035] The defoamer is an organosilicon defoamer, preferably BYK-A530.

[0036] The fumed silica is nano-sized silica produced by fumed silica production, preferably Degussa A200.

[0037] The coating prepared by this invention has the following properties: it can be cured by light and moisture, and after curing, it has excellent thermal conductivity, good adhesion, high strength, and good toughness. This coating can be used in the fields of coating, encapsulation, and bonding of electronic materials.

[0038] The advantages of this invention are:

[0039] This invention proposes a method for preparing an epoxy-modified UV / moisture dual-curing thermal coating, involving the preparation of epoxy-modified polyurethane acrylate prepolymers. Applicable to fields such as electronic packaging and electrical engineering, the coating exhibits high strength, high toughness, good adhesion, and excellent thermal conductivity. The coating supports both UV and moisture curing methods, offering flexibility and allowing selection of the appropriate curing method based on the specific application. The coating contains no volatile solvents, offering advantages in environmental friendliness and energy conservation. The invention's formulation is simple and easy to operate, facilitating industrial production. Attached Figure Description

[0040] Figure 1 The FTIR infrared spectrum of the epoxy-modified polyurethane acrylate prepared in Case 1 is shown.

[0041] 2256cm -1 The absorption band is the contraction vibration peak of isocyanate, indicating that there are residual isocyanates during the prepolymer reaction, which are used for moisture curing. 1712 cm⁻¹ -1The absorption band is characterized by the absorption peak of ester bonds. Theoretically, there are many sources of ester bonds in the prepolymer, namely polyester polyols, urethane bonds (products of hydroxyl and isocyanate), and hydroxyl groups in acrylates. (3353 cm⁻¹) -1 The absorption band is characterized by the contraction vibration peak of NH at 3000 cm⁻¹. -1 -3500cm -1 This refers to the contraction vibrational region of OH and NH, and since excess isocyanate in the reactants cannot coexist with the hydroxyl group, this indicates that the 3353cm... -1 The peak is the contraction vibration peak of NH, which, combined with the ester bond, indicates the formation of a carbamate bond. 1602 cm⁻¹ -1 and 916cm -1 The absorption bands of the benzene ring and epoxy group, respectively, indicate that epoxy resin E-51 was successfully incorporated into the prepolymer. In conclusion, the analysis of this infrared spectrum leads to the conclusion that the prepolymer was successfully prepared. Detailed Implementation

[0042] To make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0043] Implementation Case 1

[0044] The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention comprises: epoxy-modified polyurethane acrylate prepolymer, reactive diluent IBOMA, photoinitiator TPO, nano-sized alumina powder, defoamer BYK-A530, and fumed silica Degussa A200.

[0045] The epoxy-modified polyurethane acrylate prepolymer comprises 30% by weight, IBOMA comprises 30% by weight, TPO comprises 2% by weight, the nano-alumina comprises 37.5% by weight, BYK-A530 comprises 0.3% by weight, and Degussa A200 comprises 0.2% by weight.

[0046] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: 30g of polycaprolactone diol (PCL) (molecular weight 2000) is added to a three-necked flask. The flask is fixed in a heated stirrer at 85℃ and a stirring speed of 100rpm for 30 minutes. 10g of IPDI and 0.03g of dibutyltin dilaurate are added to the flask. The temperature and stirring speed are maintained, and stirring continues for 3 hours. 15g of epoxy resin E-51 is added, and stirring continues for another 3 hours. If the viscosity is too high during stirring, 10g of IBOMA can be added. The temperature is lowered to 65℃, and while maintaining the stirring speed, 2g of HEMA is added, and stirring continues for 3 hours. The mixture is cooled to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0047] The raw materials described in the formula are added sequentially to a beaker and stirred at 100 rpm for 1 hour at room temperature to obtain the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention.

[0048] Implementation Case 2

[0049] The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention comprises: epoxy-modified polyurethane acrylate prepolymer, reactive diluent IBOMA, photoinitiator TPO, nano-sized alumina powder, defoamer BYK-A530, and fumed silica Degussa A200.

[0050] The epoxy-modified polyurethane acrylate prepolymer comprises 25% by weight, IBOMA comprises 35% by weight, TPO comprises 2% by weight, the nano-alumina comprises 37.5% by weight, BYK-A530 comprises 0.3% by weight, and Degussa A200 comprises 0.2% by weight.

[0051] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: Add 30g of polycaprolactone diol (PCL) (molecular weight 2000) to a three-necked flask. Fix the flask in a heated stirrer, set the temperature to 85℃, and the stirring speed to 100rpm, and heat and stir for 30min. Add 10g of IPDI and 0.03g of dibutyltin dilaurate to the three-necked flask, and continue stirring for 3h while maintaining the temperature and stirring speed. Add 15g of epoxy resin E-51, and stir for another 3h. If the viscosity is too high during stirring, add 10g of IBOMA. Lower the temperature to 65℃, maintain the stirring speed, add 2g of HEMA, and continue stirring for 3h. Cool to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0052] The raw materials described in the formula are added to a beaker in sequence and stirred at 100 rpm for 1 hour at room temperature to obtain the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention.

[0053] Implementation Case 3

[0054] The epoxy-modified UV / moisture dual-curing high thermal conductivity coating of the present invention comprises: epoxy-modified polyurethane acrylate prepolymer, reactive diluent IBOMA, photoinitiator TPO, nano-sized alumina powder, defoamer BYK-A530, and fumed silica Degussa A200.

[0055] The epoxy-modified polyurethane acrylate prepolymer comprises 20% by weight, IBOMA comprises 40% by weight, TPO comprises 2% by weight, the nano-alumina comprises 37.5% by weight, BYK-A530 comprises 0.3% by weight, and Degussa A200 comprises 0.2% by weight.

[0056] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: Add 30g of polycaprolactone diol (PCL) (molecular weight 2000) to a three-necked flask. Fix the flask in a heated stirrer, set the temperature to 85℃, and the stirring speed to 100rpm, and heat and stir for 30min. Add 10g of IPDI and 0.03g of dibutyltin dilaurate to the three-necked flask, and continue stirring for 3h while maintaining the temperature and stirring speed. Add 15g of epoxy resin E-51, and stir for another 3h. If the viscosity is too high during stirring, add 10g of IBOMA. Lower the temperature to 65℃, maintain the stirring speed, add 2g of HEMA, and continue stirring for 3h. Cool to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0057] The raw materials described in the formula are added to a beaker in sequence and stirred at 100 rpm for 1 hour at room temperature to obtain the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention.

[0058] Comparison Case 4

[0059] The epoxy-modified UV / moisture dual-curing high thermal conductivity coating of the present invention comprises: epoxy-modified polyurethane acrylate prepolymer, reactive diluent IBOMA, photoinitiator TPO, nano-sized alumina powder, defoamer BYK-A530, and fumed silica Degussa A200.

[0060] The epoxy-modified polyurethane acrylate prepolymer comprises 10% by weight, IBOMA comprises 30% by weight, TPO comprises 2% by weight, the nano-alumina comprises 57.5% by weight, BYK-A530 comprises 0.3% by weight, and Degussa A200 comprises 0.2% by weight.

[0061] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: Add 30g of polycaprolactone diol (PCL) (molecular weight 2000) to a three-necked flask. Fix the flask in a heated stirrer, set the temperature to 85℃, and the stirring speed to 100rpm, and heat and stir for 30min. Add 10g of IPDI and 0.03g of dibutyltin dilaurate to the three-necked flask, and continue stirring for 3h while maintaining the temperature and stirring speed. Add 15g of epoxy resin E-51, and stir for another 3h. If the viscosity is too high during stirring, add 10g of IBOMA. Lower the temperature to 65℃, maintain the stirring speed, add 2g of HEMA, and continue stirring for 3h. Cool to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0062] The raw materials described in the formula are added to a beaker in sequence and stirred at 100 rpm for 1 hour at room temperature to obtain the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention.

[0063] Comparison Case 5

[0064] The epoxy-modified polyurethane UV / moisture dual-curing coating of the present invention comprises: epoxy-modified polyurethane acrylate prepolymer, reactive diluent IBOMA, photoinitiator TPO, BYK-A530, and fumed silica Degussa A200.

[0065] The epoxy-modified polyurethane acrylate prepolymer comprises 30% by weight, IBOMA comprises 67.5% by weight, TPO comprises 2% by weight, ZJ-800 comprises 0.3% by weight, and Degussa A200 comprises 0.2% by weight.

[0066] The preparation process of the epoxy-modified polyurethane acrylate prepolymer is as follows: Add 30g of polycaprolactone diol (PCL, molecular weight 2000) to a three-necked flask. Fix the flask in a heated stirrer, set the temperature to 85℃, and the stirring speed to 100rpm, and heat and stir for 30min. Add 10g of IPDI and 0.03g of dibutyltin dilaurate to the three-necked flask, and continue stirring for 3h while maintaining the temperature and stirring speed. Then add 15g of epoxy resin E-51 and stir for another 3h. If the viscosity is too high during stirring, add 10g of IBOMA. Lower the temperature to 65℃, maintain the stirring speed, add 2g of HEMA, and continue stirring for 3h. Cool to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer.

[0067] The raw materials are added sequentially according to the formula, and stirred at 100 rpm for 1 hour at room temperature to obtain the epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating of the present invention.

[0068] Performance tests were conducted on implementation cases 1-3 and comparison cases 4-5 respectively:

[0069] Tensile shear strength was tested according to GB / T 7124-2008, with 304 stainless steel and translucent polycarbonate plastic as the substrates. Curing conditions included a 365nm wavelength UV LED light source at 250mw / cm². 2 Irradiate for 30 seconds, then cure under humidity conditions at room temperature for three days.

[0070] Curing time test: The substrate was a single-layer PVC board, and the curing conditions were a 365nm wavelength UV LED light source with a power of 250mW / cm². 2 Observe the curing status of the coating every 5 seconds and record the time to complete curing.

[0071] Thermal conductivity test: Tested in accordance with ISO22007-2.

[0072] Tensile test: The elongation at break was tested according to GB / T13022-1991, the test method for tensile testing of plastic films.

[0073] The specific experimental results of implementing Case 1-3 and comparing Case 4-5 are shown in the table below.

[0074]

[0075]

[0076] The experimental results from Case Studies 1-3 and Comparative Case Studies 4-5 show that the coatings all exhibit good thermal conductivity after the addition of thermally conductive fillers. Comparative Case Study 4, with its higher filler content, also has a relatively higher thermal conductivity. However, compared to Case Studies 1-3, Comparative Case Study 4 has a longer curing time. This is not because the addition of thermally conductive fillers affects light transmittance, but rather because the higher filler content reduces the double bond content, thus increasing the curing time. The comparison of shear strength and elongation at break in Case Studies 1-3 leads to the following conclusions: under the same filler content, a higher proportion of reactive diluent results in lower shear strength and elongation at break. When the filler content changes, the filler content becomes the primary influencing factor; a higher filler content leads to poorer mechanical properties of the coating. In Comparative Case Study 5, which did not add thermally conductive fillers, despite sacrificing thermal conductivity, the curing speed was faster and the overall mechanical properties were stronger.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating, characterized in that, Includes: epoxy-modified polyurethane acrylate prepolymer, reactive diluent, photoinitiator, nano-scale thermally conductive filler, defoamer, and fumed silica; The epoxy-modified polyurethane acrylate prepolymer comprises 10-50% by weight, the reactive diluent comprises 20-40% by weight, the photoinitiator comprises 2-5% by weight, the nanoscale thermally conductive filler comprises 20-50% by weight, the defoamer comprises 0.2-0.5% by weight, and the fumed silica comprises 0.1-1% by weight, with the sum of the weight percentages of all components being 100%. The epoxy-modified polyurethane acrylate prepolymer was prepared by the following steps: A suitable amount of polyol was added to a three-necked flask, which was then fixed in a heating stirrer at 85°C and 100 rpm for 30 minutes. A suitable amount of isocyanate and catalyst were added to the flask, and stirring was continued for 3 hours while maintaining the temperature and stirring speed. A suitable amount of epoxy resin was added to the flask, and stirring was continued for 3 hours. If the viscosity was too high during stirring, a suitable amount of reactive diluent could be added to reduce the viscosity. The temperature was lowered to 65°C, and while maintaining the stirring speed, a suitable amount of end-capping agent was added, and stirring was continued for 3 hours. The mixture was cooled to room temperature to obtain the epoxy-modified polyurethane acrylate prepolymer. The epoxy resin structure needs to simultaneously satisfy both epoxy groups and hydroxyl groups, including one or more of bisphenol A glycidyl ether and bisphenol F glycidyl ether; The reactive diluent is one or more of isobornyl methacrylate, tetrahydrofuran acrylate, and acryloylmorpholine; the end-capping agent is one or more of hydroxyethyl acrylate and hydroxyethyl methacrylate. The residual NCO content of the prepared epoxy-modified polyurethane acrylate prepolymer was 4-6 wt%. The nanoscale thermally conductive filler is one or more of nanoscale alumina and nanoscale aluminum nitride.

2. The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating according to claim 1, characterized in that: The polyol is one or more of the following: polyester, polyether diol, polytetrahydrofuran diol, polypropylene glycol, and polyester polyol, with a molecular weight of 500-3000.

3. The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating according to claim 2, characterized in that: The polyol is a polyester polyol, which has the following general formula: ； Where R represents methyl, phenyl, or carbon chain, and n is a natural number from 1 to 1000.

4. The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating according to claim 1, characterized in that: The isocyanate is one or more of isophorone diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate; the catalyst is one or more of organobismuth catalyst, organotin catalyst, and organozinc catalyst.

5. The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating according to claim 1, characterized in that, The reactive diluent is one or more of isoborneol methacrylate, tetrahydrofuran acrylate, and acryloylmorpholine; the photoinitiator is one or more of diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride and benzoin diethyl ether.

6. The epoxy-modified polyurethane UV / moisture dual-curing high thermal conductivity coating according to claim 1, characterized in that, The defoamer is an organosilicon defoamer; the fumed silica is fumed silica nano-sized silica.

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