Single-component UV-curable insulating protective coating with moisture-induced secondary curing function.

Abstract

A UV and moisture curable conformal coating composition comprising 25-65 wt% of an isocyanate functional acrylated polyurethane, 30-65 wt% of an acrylic monomer, 3.5-5.5 wt% of a photoinitiator, 0.1-1 wt% of an antifoaming agent, 0.5-1.5 wt% of a dehydrating agent, 0.2-1.5 wt% of a wetting agent, and 0.5-2.5 wt% of a coupling agent.

Description

[Technical Field]

[0001] The present invention relates to an insulating protective (conformal) coating composition, a method for insulating protective coating a substrate using the composition, and a substrate coated with the composition. [Background technology]

[0002] Insulating protective coating materials are thin polymer films that conform to the contours of printed circuit boards and protect the components of the board. They are typically applied to electronic circuits with a thickness of 25-250 μm to protect them from moisture, dust, chemicals, and extreme temperatures.

[0003] Coatings can be applied in many ways, including brushing, spraying, dispensing, and dip coating. Furthermore, many materials such as acrylic, silicone, polyurethane, and parylene can be used as insulating protective coatings. Polyurethane coatings are a common choice for insulating protective coatings due to their high chemical resistance, flexibility, and hardness.

[0004] Chemically beam-curable coatings (e.g., "UV coatings") are used as insulating protective coatings because such coatings can be cured relatively quickly by exposure to radiation sources, including conventional UV (arc and microwave types) and UV-LED light sources, typically UV. Rapid curing allows manufacturers to increase throughput. However, because circuit boards and other electronic components have highly contoured surfaces, such UV coatings, when used as insulating protective coatings, suffer from the problem of uncured areas of the coating (i.e., "shadow" areas) that cannot be easily exposed to UV light due to the contours.

[0005] U.S. Patent No. 4,424,252 describes the problem of "shade curing," and such a problem is solved using a bisulfide resin. Such a resin cures by two mechanisms: a) exposure to UV light and b) curing by atmospheric moisture. Atmospheric moisture reacts with free isocyanate groups in the bisulfide resin to form amine groups. The amine groups react with other isocyanate groups to form polyurea. Curing by atmospheric moisture allows the area of ​​the coating in the "shade" to cure completely.

[0006] However, double-sulfur polyurethane resins have been plagued by problems due to their relatively high viscosity. This problem, particularly in relation to the contoured shape of the substrate, is especially relevant to insulating protective coatings. From the viewpoint of fluidity, low-viscosity resins are preferable; that is, low-viscosity resins flow more easily around the contours of circuit boards, allowing for a more uniform coating of such circuit boards.

[0007] Previous attempts to reduce the viscosity of bisulfurized polyurethane resins involved adding a considerable amount of reactive diluent to the resin. While the addition of reactive diluent helped to reduce the viscosity of the resin, it also reduced the weight percentage of free isocyanate groups in the resin. This, in turn, reduces the effectiveness of the moisture curing mechanism, particularly in shaded areas, resulting in a coating with insufficient hardness and / or solvent resistance in such areas.

[0008] U.S. Patent No. 9,932,492 describes a one-component bi-sulfur insulating protective coating composition containing an isocyanate-functionalized urethane acrylate and a polyisocyanate containing an allophanate and / or uretdione group. The composition is described as providing a coating with high hardness and solvent resistance. Insulating protective coating compositions are also disclosed in U.S. Patent Application Publication No. 2014 / 199491(A1), Chinese Patent Publication Nos. 109321125(A), 111548726(A), and 111471337(A).

[0009] To date, conventional insulating protective coating compositions have shown undesirable changes in their properties after aging at high temperatures. As a result, when used in high-temperature environments, stress cracking may occur, leading to insulating protective coatings that provide inadequate protection to circuit boards or electronic components. [Overview of the Initiative]

[0010] This invention seeks to address at least some of the problems related to the prior art, or at least to provide commercially acceptable alternatives thereto. Furthermore, this invention discloses the construction / fabrication of new assemblies, devices, and components using the disclosed materials and processes.

[0011] In a first embodiment, the present invention provides a UV and moisture-curable insulating protective coating composition comprising: 25-65% by weight of isocyanate-functionalized acrylic polyurethane, 30-65% by weight of acrylic monomer, 3.5-5.5% by weight of photoinitiator, 0.1 to 1% by weight of defoaming agent, 0.5-1.5% by weight of dehydrating agent, 0.2 to 1.5% by weight of a wetting agent, and A coupling agent in a concentration of 0.5 to 2.5% by weight.

[0012] Each aspect or embodiment defined herein may be combined with any other aspect or embodiment unless otherwise expressly indicated. In particular, any feature shown to be preferred or advantageous may be combined with any other feature shown to be preferred or advantageous.

[0013] The inventors have surprisingly found that the composition of the present invention exhibits improved retention of properties during thermal aging tests at 130°C compared to conventional insulating protective coating compositions. Advantageously, this can result in improved thermal shock resistance compared to existing technologies. While not bound by theory, this is thought to be due to the combination of the enumerated amounts of acrylic polyurethane, acrylic monomer, and photoinitiator.

[0014] From the composition, preferably a low glass transition temperature (T g ) and preferably high elasticity (low modulus) can be formed to create an insulating protective coating. This may be particularly suitable for protecting circuit boards during use. Although not bound by theory, this is thought to be due to the combination of the listed amounts of acrylic polyurethane and acrylic monomer.

[0015] Advantageously, compared to conventional insulating protective coating compositions, the compositions of the present invention can undergo a slower and more controlled polymerization process during UV curing. This reduces the level of internal stress, which may improve the ability to withstand stress cracking during thermal shock excursion. However, curing can still be fast enough for use in conventional insulating protective coating production methods and assembly lines. While not bound by theory, this is thought to be due to the combination of the enumerated amounts of acrylic polyurethane, acrylic monomer, and photoinitiator.

[0016] As used herein, the term "insulating protective coating composition" may include, for example, a composition for forming an insulating protective coating on a circuit board.

[0017] The composition contains an isocyanate-functional acrylated polyurethane (an acrylated polyurethane containing isocyanate functional groups). As used herein, the term "polyurethane" may encompass a class of polymers composed of organic units linked by carbamate (urethane) bonds. As used herein, the term "acrylated polyurethane" may encompass a polyurethane containing acrylate functional groups in addition to free isocyanate functional groups. The acrylate functional groups may also include methacrylate functional groups. The isocyanate-functional acrylated polyurethane is preferably in the form of an oligomer.

[0018] The composition is both UV-curable and moisture-curable. The composition contains functional groups for secondary moisture curing to ensure curing of areas affected by exposure to actinic radiation. When exposed to actinic radiation (typically UV), the photoinitiator can cause a reaction between the acrylate functional groups on the acrylated polyurethane and the acrylic monomer. When exposed to moisture (typically moisture contained in the air), the isocyanate functional groups can form amine groups, which can then react with other isocyanate groups to form polyureas.

[0019] The composition contains 0.1 to 1.0% by weight of an antifoaming agent. The presence of the listed amount of antifoaming agent can inhibit the generation of bubbles during storage and / or use.

[0020] The composition contains 0.5 to 1.5% by weight of a dehydrating agent. The presence of the listed amount of dehydrating agent can inhibit undesirable moisture curing of the composition during storage.

[0021] The composition contains 0.2 to 1.5% by weight of a wetting agent. The presence of the listed amount of wetting agent can improve the ability of the composition to "wet" the substrate to which it is applied, such as a circuit board. In particular, the composition can "wet" all components of the circuit board.

[0022] The composition contains 0.5 to 2.5% by weight of a coupling agent. The presence of the recited amount of coupling agent can improve the adhesion of the final insulating protective coating to the substrate to which it is applied.

[0023] The composition is preferably a "one-component" composition.

[0024] The composition preferably contains 30 to 50% by weight of an isocyanate-functional acrylated polyurethane, more preferably 35 to 45% by weight of an isocyanate-functional acrylated polyurethane. The presence of such an amount of isocyanate-functional acrylated polyurethane can further improve the retention of properties during thermal aging, preferably a low glass transition temperature, preferably a high elasticity, and the property of a slower and more controlled polymerization process during UV curing.

[0025] The isocyanate-functional acrylated polyurethane is preferably thermoplastic. The isocyanate-functional acrylated polyurethane is preferably an elastomer. The isocyanate-functional acrylated polyurethane is preferably an isocyanate-functional acrylated thermoplastic polyurethane elastomer. This can result in a particularly preferably low glass transition temperature and / or high elasticity of the insulating protective coating formed by the composition.

[0026] The isocyanate-functional acrylated polyurethane preferably has a ratio of acrylate functional groups to isocyanate functional groups of 2:1 to 1:2. Such a ratio can provide a particularly preferred amount of crosslinking during curing, i.e., not too low to cause insufficient curing, nor too high to result in a hard and inflexible coating.

[0027] The isocyanate-functional acrylated polyurethane is preferably the reaction product of reactants including: at least one polyol, preferably an amorphous hydrophobic polyol, at least one diisocyanate, preferably a branched-chain diisocyanate, and At least one hydroxyalkyl acrylate.

[0028] Typically, a diisocyanate is reacted with a polyol to obtain an isocyanate-terminated "prepolymer," and then, in a second step, the prepolymer is further reacted with a hydroxyalkyl acrylate to form an isocyanate-functionalized acrylic polyurethane.

[0029] The polyol (preferably an amorphous hydrophobic polyol) preferably includes the following: One or more of hydroxy-terminated polybutadiene, hydroxy-terminated hydrogenated polybutadiene, hydroxy-terminated polyisoprene, hydroxy-terminated polyolefin, hydroxy-terminated polyfarnesene, hydroxy-terminated hydrogenated polyfarnesene, castor oil, hydrogenated castor oil, and dimer acid-based polyester polyols (preferably C36), more preferably one or more of hydroxy-terminated hydrogenated polybutadiene, hydroxy-terminated hydrogenated polyfarnesene, hydrogenated castor oil, and dimer acid-based polyester polyols, and / or 2-ethyl-1,3-hexanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, isosorbide, C 18 A diol selected from one or more of dimerol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol, preferably 2-ethyl-1,3-hexanediol, C 18 Diols selected from one or more dimerols and 2-butyl-2-ethyl-1,3-propanediols, and / or A triol selected from one or more of trimethylolpropane, triethanolamine, diethanolamine, 1,2,6-hexanetriol, phloroglucinol (1,3,5-trihydroxybenzene), and glycerol, more preferably 1,2,6-hexanetriol.

[0030] In contrast, prior art isocyanate-functionalized polyurethanes are typically formed from polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, and polylactone polyols. Polyether and polyester polyols have been shown to yield unsatisfactory results when incorporated into insulating protective coatings because of their poor electrical properties, particularly surface insulation resistance (SIR), at 85% RH and 85°C, conditions commonly used to test insulating protective coatings for automotive applications. Polyether and polyester polyol-based polyurethane acrylate oligomers tend to decompose primarily by oxidation and hydrolysis under these automotive test conditions. Furthermore, their low-temperature performance is generally unacceptable for use in insulating protective coatings. Insulating protective coatings for automotive and aerospace applications need to maintain flexibility at temperatures as low as -60°C. In the automotive industry, -40°C is the accepted standard test temperature for evaluating low-temperature performance. Current insulating protective coatings utilizing polyester polyol-based polyurethane acrylate oligomers tend not to retain their mechanical properties (elongation (flexibility), tensile strength, and modulus) when aged below ambient temperature, especially at high temperatures. Relatively low initial elongation values ​​of approximately 50% (in samples aged and tested at ambient temperature) degrade to unacceptable levels during thermal aging / testing below ambient temperature. As observed by the inventors of this application, elongation values ​​below 50% generally lead to premature failure of insulating protective coatings when subjected to thermal shock testing. As the flexibility of the insulating protective coating is lost, widespread cracking of the coating becomes apparent, often after only a few hundred cycles.

[0031] The glass transition temperature of the final insulating protective coating is also of great importance. A glass transition temperature significantly higher than -40°C can also cause stress cracking during thermal shock testing. The isocyanate-functionalized acrylic polyurethanes of this application, formed from the polyols listed above, may exhibit improved properties compared to commercially available polyurethane acrylate oligomers (which are recommended and / or used in current radiation-curable insulating protective coatings) due to their inherent composition and low glass transition temperatures. In particular, compositions containing isocyanate-functionalized acrylic polyurethanes formed from the polyols listed above may exhibit particularly excellent flexibility and low-temperature performance, along with improved SIR performance. The compositions can still be cured via a primary curing mechanism in the "line of sight" region (UV / UV-LED light polymerizing the acrylate groups) and via a secondary curing mechanism in the "shadow region" of the circuit board (isocyanate moisture reaction).

[0032] The polyol is preferably present in an amount of 500 to 3000 gmol. -1 , comfortably 1000~2000 gmol -1 More preferably, about 2000 gmol -1 It has a number-average molar mass.

[0033] The polyol preferably has a functional value of 1.9 to 2.5 and / or a hydroxyl value of 50 to 250 mg KOH / g.

[0034] The diisocyanates are preferably 1,3-bis(1-isocyanato-1-methylethyl)benzene (TMXDI, tetramethylxylylene diisocyanate), 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane (IPDI, isophorone diisocyanate), 1,6-diisocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI, trimethylhexamethylene diisocyanate), 1,6-diisocyanatohexane (HDI, hexamethylene diisocyanate), and 4,4'-diisocyanatodicyclohexylmethane (H 12The compound comprises one or more of MDI and 1,5-diisocyanatopentane (PDI, 1,5-pentamethylene diisocyanate), preferably 1,6-diisocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI, trimethylhexamethylene diisocyanate). This, along with improved SIR, can result in a cured composition exhibiting particularly excellent flexibility and low-temperature performance. Prior art isocyanate-functionalized acrylic polyurethanes are typically formed from aromatic diisocyanates (e.g., TDI, toluene diisocyanate). This exacerbates problems of insufficient retention of tensile properties / insufficient thermal shock (also due to the prior art polyol type), as the aromatic properties of the resulting polymers mean they are more susceptible to oxidative degradation during aging at high temperature / high humidity.

[0035] The hydroxyalkyl acrylate preferably comprises one or more of 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate, more preferably 4-hydroxybutyl acrylate. Such hydroxyalkyl acrylates have longer carbon chains than hydroxyalkyl acrylates used to form conventional isocyanate-functionalized acrylic polyurethanes used for insulating protective coatings. This, along with improved SIR, can result in cured compositions exhibiting particularly excellent flexibility and low-temperature performance.

[0036] In a particularly preferred embodiment, the isocyanate-functionalized acrylic polyurethane is a reaction product of reactants comprising: Hydroxy-terminated hydrogenated polybutadiene, hydroxy-terminated hydrogenated polyfarnesene, hydrogenated castor oil, dimer acid-based polyester polyol, 2-ethyl-1,3-hexanediol, C 18 One or more dimer ols and 1,2,6-hexanetriols; 1,6-Diisocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI, trimethylhexamethylene diisocyanate); and 4-Hydroxybutyl acrylate.

[0037] To form isocyanate-functionalized acrylic polyurethanes from the reaction products of the above species, a catalyst is preferably used to increase the reaction rate and / or selectivity, or to lower the temperature that may be required. Suitable catalysts are known in the art and include, for example, metal complexes and tertiary amines. Among metal catalysts, organotin compounds (such as DBTL, DOTL, and tin carboxylates) are very commonly used in the synthesis of polyurethanes. While they offer very good performance, they have an undesirable toxicity profile. Other metal catalysts have been developed that exhibit similar performance / reactivity to tin-based materials while being far more user- and environmentally friendly. Notable examples include zirconium, zinc, and bismuth compounds. Preferred catalysts include bismuth carboxylate to catalyze the reaction between isocyanate and hydroxyl-containing reagents. Examples of commercially available such catalysts include K-Kat XC-B221, K-Kat XK651, and K-Kat 6212 from King Industries, and Tibkat 716 and Tibkat 720 from Tib Chemicals.

[0038] The composition preferably contains 45-60% by weight of acrylic monomer, more preferably 50-60% by weight of acrylic monomer. The presence of such an amount of acrylic monomer can further improve the properties of the material, including retention of properties during thermal aging, preferably a low glass transition temperature, preferably high elasticity, and a slower and more controlled polymerization process during UV curing. The acrylic monomer can be considered a reactive diluent.

[0039] The acrylic monomer preferably comprises a linear alkyl acrylate containing 4 to 12 carbon atoms, more preferably 6 to 12 carbon atoms, and even more preferably 8 to 10 carbon atoms. Preferably, the linear alkyl acrylate comprises an octadecyl acrylate.

[0040] In addition to linear alkyl acrylates, the acrylic monomer may further comprise diacrylates, preferably selected from one or both of 1,6-hexanediol diacrylate and 3-methyl-1,5-pentanediol diacrylate. Such species are particularly effective reactive diluents when combined with other components of the composition.

[0041] The acrylic monomers may also include cyclic acrylates, more preferably tetrahydrofurfuryl acrylate, cyclic trimethylolpropane formal acrylate, t-butylcyclohexanol acrylate, 3,3,5-trimethylcyclohexyl acrylate, isobornyl acrylate, and 2-phenoxyethyl acrylate, and even more preferably tetrahydrofurfuryl acrylate. Such species are particularly effective reactive diluents when combined with other components of the composition.

[0042] The photoinitiator preferably includes the following: Alpha-hydroxyketone photoinitiators, and / or Phenylphosphine oxide-based photoinitiators, and / or Ethylphenylglyoxylate type photoinitiator.

[0043] More preferably, the photoinitiator includes: Alpha-hydroxyketone photoinitiators, Phenylphosphine oxide-based photoinitiators, and Ethylphenylglyoxylate type photoinitiator.

[0044] Such combinations of photoinitiators can result in a particularly controlled polymerization process during UV curing. Alpha-hydroxyketone photoinitiators can result in surface curing of the composition. Suitable commercially available examples of alpha-hydroxyketone photoinitiators include Darocur® / Irgacure 1173® and Doublecure® 173. Phenylphosphine oxide photoinitiators can result in through-curing / deep curing of the composition. Suitable commercially available examples of phenylphosphine oxide photoinitiators include Irgacure® 819 and Doublecure® 1819. Methylphenylglyoxylate photoinitiators can be particularly effective in controlling the degree of curing to minimize internal stress during curing and prevent yellowing and excessive odor after curing. A commercially available example of a methylphenylglyoxylate photoinitiator is Doublecure® 200.

[0045] The alpha-hydroxyketone photoinitiator preferably contains 2-hydroxy-2-methyl-1-phenyl-propan-1-one. Such photoinitiators may be particularly effective in bringing about surface hardening of the composition.

[0046] Phenylphosphine oxide-based photoinitiators preferably include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphineate, and / or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. Such photoinitiators may be particularly effective in bringing through-curing / deep-curing of compositions.

[0047] Ethylphenylglyoxylate-type photoinitiators preferably contain methyl benzoylformate. Such photoinitiators can be particularly effective in regulating the curing rate to minimize internal stress during curing and prevent yellowing and excessive odor after curing.

[0048] The photoinitiator preferably comprises a thioxanthone-type initiator containing 2-isopropylthioxanthone, and preferably a tertiary amine synergist containing ethyl-4-(dimethylamino)benzoate. The combination of the photoinitiator and synergist may be particularly effective in providing a good balance between surface curing and through- (deep) curing of the composition. Examples of commercially available thioxanthone-type photoinitiators and synergists are Ominrad® ITX, Speedcure® ITX, and Omnirad® EDB.

[0049] The composition preferably contains 3.8 to 5.2% by weight of a photoinitiator, more preferably 4 to 4.5% by weight of a photoinitiator.

[0050] The defoaming agent preferably contains a polyethersiloxane. Polyethersiloxane is a particularly effective defoaming agent when used in combination with other components of the composition.

[0051] The composition preferably contains 0.2 to 0.8% by weight of an antifoaming agent, more preferably 0.3 to 0.7% by weight of an antifoaming agent.

[0052] The dehydrating agent preferably contains p-toluenesulfonyl isocyanate. p-toluenesulfonyl isocyanate is a particularly effective dehydrating agent when used in combination with other components of the composition.

[0053] The composition preferably contains 0.7 to 1.3% by weight of a dehydrating agent, more preferably 0.8 to 1.2% by weight of a dehydrating agent.

[0054] The wetting agent preferably includes poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene glycol)methyl ether. Poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene glycol)methyl ether is a particularly effective wetting agent when used in combination with other components of the composition.

[0055] The composition preferably contains 0.5 to 1.3% by weight of a wetting agent, more preferably 0.8 to 1.2% by weight of a wetting agent.

[0056] The coupling agent preferably comprises an acrylate-functionalized silane and / or a (meth)acrylate-functionalized silane. Such silanes are particularly effective coupling agents when used in combination with other components of the composition.

[0057] The composition preferably contains 1 to 2% by weight of a coupling agent, more preferably 1.0 to 1.5% by weight of a coupling agent.

[0058] Traditionally, lower viscosity insulating protective coating compositions have been considered to flow better onto PCB surfaces than higher viscosity alternatives. However, reducing the viscosity of insulating protective coating compositions can promote excessive flow under the components, which can make complete secondary curing difficult.

[0059] However, the inventors have found that adjusting the rheology of the insulating protective coating composition, rather than merely adjusting the viscosity, is highly beneficial. The insulating protective coating compositions described herein preferably contain a rheology modifier.

[0060] The rheological modifier preferably comprises a polyamide wax, preferably in the form of crystalline fibers (polyamide wax containing crystalline fibers). Advantageously, the use of polyamide wax allows the composition to be applied to PCBs by selective spray coating. This is because polyamide wax can introduce thixotropy into the system. Thixotropy is a shear-thinning property that imparts low viscosity at high shear rates and high viscosity at low shear rates. Selective spray application is a high-shear process, meaning the coating is applied to the PCB at low viscosity, allowing for good flow and perfect fit to the PCB surface. After application, if low-shear conditions prevail, the coating viscosity may undergo a time-dependent recovery to an initial high-viscosity system. This minimizes excessive flow (splatter, spray spray) under the components and at the substrate edges, i.e., results in controlled flow. This feature can also ensure complete and reliable coverage of the edges of the PCB components, a problem that has plagued many conventional insulating protective coatings. Sharp edges / legs of components are generally not coated sufficiently well with low-viscosity coating compositions, and these become thin and weak areas in the insulating protective coating, leading to PCB damage. The insulating protective coating composition of the present invention aims to address this. Although not bound by theory, it is thought that the crystalline fibers of the polyamide wax form an interacting network within the insulating protective coating composition. This network can be broken under high shear conditions, but quickly re-establishes itself and returns to its original state when their shear forces are removed. In this regard, the composition preferably exhibits a thixotropy index of 1.5 to 3.5. This can be achieved by the use of polyamide wax.

[0061] The composition preferably further comprises a UV tracer, which can advantageously result in a composition that glows blue under black light.

[0062] The UV tracer preferably contains 2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole). 2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole) is a particularly effective UV tracer when combined with other components of the composition.

[0063] The composition preferably contains 0.1 to 0.5% by weight of UV tracer, more preferably 0.2 to 0.4% by weight of UV tracer.

[0064] The composition preferably includes an odor masking agent. This makes the composition more comfortable to use.

[0065] The odor masking agent preferably comprises one or both, preferably both, of dimethylocta-7-en-2-ol and butylcyclohexyl acetate. Such species are particularly effective odor masking agents when combined with other components of the composition.

[0066] In a further embodiment, the present invention relates to a method for insulating protective coating a substrate, To provide a base material, To provide the compositions described herein, Depositing the composition on at least a portion of the substrate, Exposing a coated substrate to chemical radiation, This provides a method that includes [something].

[0067] The advantages and preferred features of the first embodiment apply equally to this embodiment.

[0068] Depositing the composition onto at least a portion of the substrate may include one or more of the following methods: brushing, spraying, dispensing, and dip coating.

[0069] The chemical beam preferably includes UV light, such as a UV-LED.

[0070] The base material preferably includes a circuit board or electronic components.

[0071] In a further embodiment, the present invention provides a substrate coated with the composition described herein. The advantages and preferred features of the first embodiment are equally applicable to this embodiment.

[0072] In a further embodiment, the present invention provides a UV and moisture-curable insulating protective coating composition comprising an isocyanate-functionalized acrylic polyurethane, wherein the isocyanate-functionalized acrylic polyurethane is a reaction product of reactants comprising the following species: Polyols, preferably amorphous polyols, Diisocyanates, preferably branched diisocyanates, and Hydroxyalkyl acrylate.

[0073] The advantages and preferred features of the first embodiment apply equally to this embodiment.

[0074] In a further embodiment, the present invention provides UV and moisture-curable insulating protective coating compositions comprising: 25-65% by weight of isocyanate-functionalized acrylic polyurethane, 30-65% by weight of acrylic monomer, In addition, you may choose one or more of the following: 3.5-5.5% by weight of photoinitiator, 0.1 to 1% by weight of defoaming agent, 0.5-1.5% by weight of dehydrating agent, 0.2-1.5% by weight of wetting agent, A coupling agent in an amount of 0.5 to 2.5% by weight, and A rheological modifier in a concentration of 0.1 to 2.5% by weight.

[0075] The advantages and preferred features of the first embodiment apply equally to this embodiment.

[0076] The present invention will now be further described with respect to the following numbered clauses.

[0077] 1. UV and moisture-curable insulating protective coating composition comprising the following: 52-75% by weight of isocyanate-functionalized acrylic polyurethane, 20-43% by weight of acrylic monomer, 3.5-5.5% by weight of photoinitiator, 0.5-1% by weight of defoaming agent, 0.2-0.5% by weight of dehydrating agent, 0.3 to 0.5% by weight of a wetting agent, and A coupling agent in a concentration of 0.1 to 0.3% by weight.

[0078] The composition according to item 1, comprising 2.55 to 70% by weight of isocyanate-functionalized acrylic polyurethane, preferably 57 to 65% by weight of isocyanate-functionalized acrylic polyurethane.

[0079] 3. The composition according to paragraph 1 or 2, wherein the isocyanate-functionalized acrylic polyurethane is thermoplastic.

[0080] 4. The composition according to any one of the preceding items, wherein the isocyanate-functionalized acrylic polyurethane is an elastomer.

[0081] A composition according to any one of the preceding items, comprising 5.25 to 41% by weight of an acrylic monomer, preferably 30 to 40% by weight of an acrylic monomer.

[0082] 6. The photoinitiator is Alpha-hydroxyketone photoinitiators, and / or Phenylphosphine oxide-based photoinitiators, and / or Ethylphenylglyoxylate type photoinitiator A composition according to any one of the preceding items, including:

[0083] 7. The photoinitiator is Alpha-hydroxyketone photoinitiators, Phenylphosphine oxide-based photoinitiators, and Ethylphenylglyoxylate type photoinitiator A composition according to any one of the preceding items, including:

[0084] 8. The composition according to paragraph 6 or 7, wherein the alpha-hydroxyketone photoinitiator comprises 2-hydroxy-2-methyl-1-phenyl-propan-1-one.

[0085] 9. The composition according to any one of paragraphs 6 to 8, wherein the phenylphosphine oxide-based photoinitiator comprises phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0086] 10. The composition according to any one of paragraphs 6 to 9, wherein the ethylphenyl glyoxylate type photoinitiator comprises methyl benzoylmate.

[0087] 11. The composition according to any one of the preceding items, wherein the defoaming agent comprises a polyethersiloxane.

[0088] 12. The composition according to any one of the preceding items, wherein the dehydrating agent comprises p-toluenesulfonyl isocyanate.

[0089] 13. The composition according to any one of the preceding items, wherein the wetting agent comprises poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene glycol)methyl ether.

[0090] 14. The composition according to any one of the preceding items, wherein the coupling agent comprises an acrylate-functionalized silane.

[0091] 15. The composition according to any one of the preceding items, further comprising a reactive diluent.

[0092] 16. The composition according to item 15, wherein the reactive diluent comprises one or both, preferably both, of 3,3,5-trimethylcyclohexyl acrylate and tricyclodecanedimethanol diacrylate.

[0093] 17. The composition according to any one of the preceding items, further comprising a UV tracer.

[0094] 18. The composition described in item 17, wherein the UV tracer comprises 2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole).

[0095] 19. The composition according to any one of the preceding items, further comprising an odor masking agent.

[0096] 20. The composition according to item 19, wherein the odor masking agent comprises one or both, preferably both, of dimethylocta-7-en-2-ol and butylcyclohexyl acetate.

[0097] 21. A method for insulating protective coating a substrate, To provide a base material, To provide the composition described in any one of the preceding paragraphs, Depositing the composition on at least a portion of the substrate, Exposing a coated substrate to chemical radiation, Methods that include...

[0098] 22. The method according to paragraph 21, wherein the substrate includes a circuit board or electronic components.

[0099] 23. A substrate coated with any one of the compositions described in paragraphs 1 to 20.

[0100] The advantages and preferred features of the preceding embodiments apply equally to the subject matter of these provisions. [Brief explanation of the drawing]

[0101] [Figure 1] The results of the SIR test for sample 1 and two commercially available oligomers are shown. [Figure 2] This shows the value of the growth. [Figure 3] The value of the modulus of elasticity is shown. [Examples]

[0102] The present invention will be further described by reference to the following examples.

[0103] General synthesis of isocyanate-functionalized acrylic polyurethane oligomers: In the first step, a diisocyanate is reacted with a polyol (and / or diol / triol) at high temperature and under nitrogen using a catalyst to obtain an isocyanate-terminated "prepolymer." In the second step, this prepolymer is further reacted with a hydroxyalkyl acrylate under air to form an isocyanate-functional polyurethane acrylate oligomer. High temperature and catalysts are used to shorten the total reaction time, lower the temperature required for the reaction, and / or to improve the selectivity of the reaction between the isocyanate group in the diisocyanate and the hydroxyl group of the other reactants.

[0104] An example reaction scheme is as follows:

[0105] [ka]

[0106] The above reaction scheme shows steps 1 and 2, as well as the idealized structure of the product, an isocyanate-functionalized polyurethane acrylate oligomer.

[0107] In the reaction scheme (step 2, acrylication), the R3 group of the hydroxyalkyl acrylate may be as follows: -CH2CH2- 2-hydroxyethyl acrylate -CH2CH2CH2- in the case of 3-hydroxypropyl acrylate -CH2CH2CH2CH2- in the case of 4-hydroxybutyl acrylate

[0108] In reaction scheme (step 1), representative structures of the reagents used are as follows: Polyol / diol: C36 dimer acid-based polyester polyol:

[0109] [Chemical formula] Hydrogenated polybutadiene:

[0110] [Chemical formula] C36 dimer diol:

[0111] [Chemical formula] 0000443Isocyanate: TMDI

[0112] [Chemical formula]

[0113] Oligomer synthesis, sample 1: 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate (0.21 mol, 44.10 g) and bismuth carboxylate catalyst (0.1 wt% based on the total batch) were added to a round-bottom reaction flask equipped with a thermometer, a stirrer, and a nitrogen line. Nitrogen was introduced into the flask as an initial purge and then continuously introduced at a constant flow rate of about 1 mL / min to maintain an inert atmosphere. C with a molar mass of 2000 gmol -1 of[[ID=A dimer acid-based polyester polyol (0.1 mol, 200 g) was added to the flask. The reaction was carried out at 80°C for 2 hours, thereby forming an isocyanate-terminated prepolymer. The endpoint of this reaction was when the theoretical isocyanate % was achieved (measured by back titration with di-n-butylamine according to ISO 14896), and the FTIR spectrum showed bands characteristic of the isocyanate-terminated polyurethane prepolymer, coupled by the absence of bands associated with hydroxyl groups. After this step was completed, the nitrogen line was replaced with a dry air line. Here again, an oxygen-rich atmosphere was maintained by applying a constant flow rate of approximately 1 mL / min following an initial purge. The temperature was reduced from 80°C to 50°C, and then 100 ppm of a polymerization inhibitor, such as phenothiazine or MEHQ, was added to the flask (to prevent self-polymerization of acrylate groups). After this was completely dissolved / dispersed in the isocyanate-terminated polyurethane prepolymer, 4-hydroxybutyl acrylate (0.11 mol, 15.86 g) was added to the flask. This reaction was carried out at 50-60°C for 1 hour. Again, the endpoint of this reaction was when the theoretical isocyanate % was achieved, and the FTIR spectrum showed bands characteristic of the isocyanate-terminated polyurethane prepolymer, coupled with the presence of bands associated with the acrylate group. A colorless isocyanate-functionalized urethane acrylate oligomer with viscosity (625,000 mPa·s at 20°C) was obtained in high yield (>95%). The final isocyanate content was 1.78%, and the acrylate:isocyanate ratio was 1:1.

[0114] Oligomer synthesis, Sample 2: This polyurethane acrylate oligomer was prepared using the same process as described in Example 1. 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate (1.356 mol, 284.76 g) and bismuth carboxylate catalyst (0.1 wt% of the total batch) were added in approximately 540 gmol by mass. -1 C 36A dimer acid-based polyol (0.645 mol, 349.59 g) was reacted to form an isocyanate-terminated prepolymer. Then, 4-hydroxybutyl acrylate (0.71 mol, 102.41 g) was added to the flask and reacted to form a polyurethane acrylate oligomer. A viscous (103,000 mPa.s at 20°C) straw-colored isocyanate-functionalized urethane acrylate oligomer was obtained in high yield (>95%). The final isocyanate content was 4.31%, and the acrylate:isocyanate ratio was 1:1.

[0115] Oligomer synthesis, Sample 3: This polyurethane acrylate oligomer was prepared using the same process as described in Example 1. 2,2,4(2,4,4)-trimethylhexamethylene diisocyanate (0.21 mol, 44.10 g) and bismuth carboxylate catalyst (0.01 wt%) relative to the total batch were added in a molar mass of 2000 gmol. -1 Hydrogenated polybutadiene polyol (0.1 mol, 200 g) was reacted to form an isocyanate-terminated prepolymer. Then, 2-hydroxyethyl acrylate (0.11 mol, 12.77 g) was added to the flask and reacted to form a polyurethane acrylate oligomer. A straw-colored isocyanate-functionalized urethane acrylate oligomer with viscosity (750,000 mPa.s at 20°C) was obtained in high yield (>95%). The final isocyanate content was 1.73%, and the acrylate:isocyanate ratio was 1:1.

[0116] Testing of isocyanate-functionalized acrylic polyurethane oligomers: Improvement of surface insulation resistance (SIR) This is a critical property of insulating protective coatings and is routinely evaluated under harsh conditions to check (a) the initial SIR value, (b) any trend in the SIR value over time, and (c) any evidence of corrosion on the PCB. A downward trend indicates degradation of the insulating protective coating, which can lead to premature failure of the PCB via corrosion, dendrite formation, tin whiskers, etc.

[0117] Laboratory testing of oligomer samples 1-3 suggests that higher SIR values ​​(single-digit) can be achieved than those of commercially available oligomers. Figure 1 shows the results of SIR tests for sample 1 and two commercially available oligomers. Commercial example 1 is an isocyanate aliphatic functional urethane acrylate. Commercial example 2 is an oligomer with UV, isocyanate, and siloxane functional groups. As can be seen from the figure, sample 1 achieved an average SIR value of 9.31 with a stable linear response over the test period, indicating that the coating is functioning well and showing no signs of degradation. Both commercially available oligomers returned lower average SIR values ​​of 8.42 and 7.98 for commercial example 1 and commercial example 2, respectively. Furthermore, the responses of these oligomers were not stable and showed a clear downward trend. The stable response of sample 1 at 85% relative humidity and 85°C is excellent. The minimum SIR value acceptable for automotive applications is 8 Log 10 Sample 1 slightly exceeds this. Conversely, none of the commercially available oligomers performed adequately in this test and, based on the trend of decreasing values ​​over time, were able to meet this criterion during the extended test.

[0118] Improvement in maintaining tensile properties The tensile properties of oligomers 1-3 and commercial examples were measured initially (after primary and secondary curing) and after aging at 130°C. Tests were conducted at ambient temperature and -40°C. Sample 1 showed higher elongation and lower modulus initially, and retained these initial properties to a higher degree after aging. The elongation and modulus values ​​are shown in Figures 2 and 3. Regarding elongation, samples 1, 2, and 3 showed higher levels of elasticity / flexibility than both commercial materials when tested initially. They retained their elasticity after thermal aging and when tested below ambient temperature. When both of these conditions are met, samples 1-3 perform exceptionally well.

[0119] The oligomer in Commercial Example 2 has a lower initial elongation value, but tends to improve in terms of retaining this elongation during thermal aging. However, the combination of thermal aging and testing below ambient temperature yields unsatisfactory results, with elongation decreasing by approximately 50%. The oligomer in Commercial Example 1 appears to be far inferior to samples 1-3 in terms of retaining elasticity. The initial elongation value of approximately 50% decreases tenfold (to approximately 5%) after thermal aging and testing below ambient temperature. The test sample breaks almost immediately upon starting the test. Commercial Examples 1 and 2 appear to mainly exhibit plastic deformation when tested below ambient temperature and do not recover noticeably when returned to room temperature (they do not return to their original dimensions). Samples 1-3 appear to mainly exhibit elastic deformation and recover quickly (the samples return to their original dimensions in less than 1 minute at room temperature).

[0120] Regarding the modulus of elasticity, a measure of the "stiffness" of a sample, a higher modulus indicates a stiffer material with lower elasticity. All oligomers tested started with very low modulus of elasticity, indicating they are flexible elastic materials. Upon aging, samples 1-3 showed a moderate increase of one order of magnitude in modulus values ​​from 0.5-1.0 MPa to 15-45 MPa, but as mentioned above, this did not appear to have a significant effect on elasticity / recovery. However, both commercially available materials showed a significant increase in modulus of elasticity when tested below ambient temperature, which worsened when aged at high temperatures before testing. Unaged samples (stored at 25°C before testing) showed a double-order-of-magnitude increase when tested at -40°C, and samples aged at the same test temperature also showed a double-order-of-magnitude increase.

[0121] This manifests as increased stiffness and insufficient recovery in these samples. While not theoretically bound, these changes in tensile properties are likely due to increased crystallinity (and associated intermolecular bonding) in the commercial material compared to oligomers 1-3. This, too, contributes to insufficient thermal shock performance. The test regime described above is designed to simulate the exposure of the insulating protective coating (in this case, the oligomer) to actual usage conditions.

[0122] Improvement of thermal shock resistance Thermal shock tests showed that samples 1-3 exhibited improved thermal shock resistance compared to commercially available oligomers.

[0123] Decrease in Tg (glass transition temperature) The Tg test showed that samples 1-3 exhibited lower Tg temperatures compared to commercially available oligomers.

[0124] The detailed description provided herein is provided by description and illustration and is not intended to limit the scope of the appended claims. Many modifications of the currently preferred embodiments shown herein will be obvious to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A UV and moisture-curable insulating protective coating composition, 25-65% by weight of isocyanate-functionalized acrylic polyurethane, 30-65% by weight of acrylic monomer, 3.5 to 5.5% by weight of photoinitiator, 0.1 to 1% by weight of an antifoaming agent, and 0.5 to 2.5% by weight of coupling agent, A UV and moisture-curable insulating protective coating composition comprising the following:

2. Containing 30-50% by weight of isocyanate-functionalized acrylic polyurethane, and / or The isocyanate-functionalized acrylic polyurethane is thermoplastic, and / or The composition according to claim 1, wherein the isocyanate-functionalized acrylic polyurethane is an elastomer.

3. The composition according to claim 1 or 2, wherein the isocyanate-functionalized acrylic polyurethane has an acrylate functional group to isocyanate functional group ratio of 2:1 to 1:

2.

4. The isocyanate-functionalized acrylic polyurethanes are of the following types: polyol, Diisocyanates, and Hydroxyalkyl acrylate The composition according to claim 1 or 2, which is a reaction product of a reactant containing

5. The polyol has a molar mass of 500 to 3000 gmol-1, and / or The polyol has a functional value of 1.9 to 2.5 and / or a hydroxyl value of 50 to 250 mg KOH / g, and / or The diisocyanates mentioned above are 1,3-bis(1-isocyanato-1-methylethyl)benzene (TMXDI, tetramethylxylylene diisocyanate), 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane (IPDI, isophorone diisocyanate), 1,6-diisocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI, trimethylhexamethylene diisocyanate), 1,6-diisocyanatohexane (HDI, hexamethylene diisocyanate), 4,4' - Diisocyanatodicyclohexylmethane (H １２ A compound comprising one or more of MDI, and 1,5-diisocyanatopentane (PDI, 1,5-pentamethylene diisocyanate), and / or The composition according to claim 4, wherein the hydroxyalkyl acrylate comprises one or more of 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate.

6. Containing 45-60% by weight of acrylic monomer, and / or The aforementioned acrylic monomer Containing linear alkyl acrylates containing 4 to 12 carbon atoms, and / or The aforementioned acrylic monomer The composition according to claim 1 or 2, comprising one or both of 1,6-hexanediol diacrylate and 3-methyl-1,5-pentanediol diacrylate.

7. The aforementioned acrylic monomer The composition according to claim 1 or 2, comprising a cyclic acrylate.

8. The aforementioned photoinitiator, Alpha-hydroxyketone photoinitiators, and / or Phenylphosphine oxide-based photoinitiators, and / or Ethylphenylglyoxylate type photoinitiator A composition according to claim 1 or 2, comprising:

9. The alpha-hydroxyketone photoinitiator comprises 2-hydroxy-2-methyl-1-phenylpropan-1-one, and / or The phenylphosphine oxide-based photoinitiator includes phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphineate, and / or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and / or The ethylphenylglyoxylate type photoinitiator comprises methyl benzoylmate and / or The aforementioned photoinitiator, Thioxanthone-type initiators containing 2-isopropylthioxanthone, and Tertiary amine synergistic agent containing ethyl-4-(dimethylamino)benzoate The composition according to claim 8, comprising:

10. The composition according to claim 1 or 2, comprising 3.8 to 5.2% by weight of a photoinitiator.

11. The defoaming agent includes and / or polyethersiloxane. The composition contains 0.2 to 0.8% by weight of an antifoaming agent, and / or The composition comprises 0.5 to 1.5% by weight of a dehydrating agent, wherein the dehydrating agent comprises p-toluenesulfonyl isocyanate, and / or The composition according to claim 1 or 2, wherein the composition comprises 0.2 to 1.5% by weight of a wetting agent, and the wetting agent comprises poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene glycol)methyl ether.

12. The coupling agent includes an acrylate or methacrylate-functionalized silane, and / or The composition contains 1 to 2% by weight of a coupling agent, and / or The composition according to claim 1 or 2, wherein the composition further comprises a rheological modifier, the rheological modifier comprising a polyamide wax, and / or the composition comprising 0.1 to 2.5% by weight of the rheological modifier.

13. The composition further comprises a UV tracer, wherein the UV tracer comprises 2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole, and the composition comprises 0.1 to 0.5% by weight of the UV tracer, and / or The composition according to claim 1 or 2, wherein the composition further comprises an odor masking agent, the odor masking agent comprising one or both of dimethylocta-7-en-2-ol and butylcyclohexyl acetate.

14. A method for applying an insulating protective coating to a substrate, To provide a base material, To provide the composition according to claim 1 or 2, Depositing the composition on at least a portion of the substrate, Exposing a coated substrate to chemical radiation, Methods that include...

15. A substrate coated with the composition according to claim 1 or 2.

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