CN115477895A

CN115477895A - Multi-curing conformal coating and preparation method thereof

Info

Publication number: CN115477895A
Application number: CN202211168755.3A
Authority: CN
Inventors: 尹翠蕾; 秦旺洋; 范从国; 姚上军; 张祥云
Original assignee: Itw Speciaty Material Suzhou Co ltd
Current assignee: Itw Speciaty Material Suzhou Co ltd
Priority date: 2022-09-24
Filing date: 2022-09-24
Publication date: 2022-12-16
Anticipated expiration: 2042-09-24
Also published as: CN115477895B

Abstract

The application relates to the technical field of circuit board printing, and particularly discloses a multi-curing conformal coating and a preparation method thereof. The multi-curing conformal coating is prepared from the following raw materials in parts by weight: 5-35 parts of organic silicon modified polyurethane acrylate, 5-35 parts of hybrid organic silicon resin, 40-53 parts of reactive diluent, 3-7 parts of photoinitiator and 0.1-0.5 part of auxiliary agent; the preparation method comprises the following steps: mixing the reactive diluent, the photoinitiator and the auxiliary agent, introducing nitrogen, adding the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin, and mixing to obtain the coating. The multi-curing conformal coating can be subjected to multi-curing, and the hybrid organic silicon resin and the organic silicon modified polyurethane acrylate are subjected to mutual synergistic reaction, so that the curing efficiency is improved. By adding the hybrid organic silicon resin, the wear resistance and strength of the coating are improved, the adhesive force between the coating and the base layer is further enhanced, and the comprehensive performance of the coating is improved.

Description

Multi-curing conformal coating and preparation method thereof

Technical Field

The application relates to the technical field of circuit board printing, in particular to a multi-curing conformal coating and a preparation method thereof.

Background

The circuit board is a common product in the electronic industry, the existing circuit board has higher requirement on the environment and poorer tolerance capability to the severe environment in the actual use process, and the conformal coating is a protective coating coated on the printed circuit board with the plug-in component, so that the electronic component can be prevented from being influenced by external factors, and the functions of dust prevention, moisture prevention, chemical prevention, mildew and corrosion prevention and the service life of a device are prolonged.

The UV curing conformal coating has the characteristics of high curing speed, suitability for thermosensitive base materials, no VOC (volatile organic compound) emission, environmental protection, energy conservation and high efficiency, and is more and more emphasized in the field of printed circuit board conformal coatings. At present, a double-hybrid curing technology can be adopted for a complex circuit board with a small number of shadow areas, namely UV moisture double curing, most areas on the circuit board are rapidly cured through UV light, and then moisture dark curing is used for continuously curing in a subsequent process, so that the small number of shadow areas are completely cured in a short period, the coating production efficiency of the circuit board is improved, and the comprehensive curing of a conformal coating is ensured.

However, this UV moisture dual curing technique has disadvantages in that the presence of oxygen inhibition makes the paint not sufficiently UV-cured, the shadow part or the bottom of the thick coating blocks moisture from entering due to surface drying too fast, so that the paint does not sufficiently moisture-cured, and the final properties of the coating are affected.

Disclosure of Invention

In order to solve the problems of insufficient UV curing of the coating due to the existence of oxygen inhibition and insufficient curing of the coating due to too fast surface drying of the coating for blocking moisture, the application provides a multi-curing conformal coating and a preparation method thereof.

In a first aspect, the application provides a multi-curing conformal coating, which adopts the following technical scheme:

the multi-curing conformal coating is prepared from the following raw materials in parts by weight: 5-35 parts of organic silicon modified polyurethane acrylate, 5-35 parts of hybrid organic silicon resin, 40-53 parts of reactive diluent, 3-7 parts of photoinitiator and 0.1-0.5 part of auxiliary agent; the organic silicon modified polyurethane acrylate comprises vinyl, epoxy, NCO group and alkoxy, and the hybrid organic silicon resin is prepared from the following raw materials in parts by weight: 3 to 9 parts of siloxane containing vinyl, 3 to 9 parts of siloxane containing epoxy and 5 to 13 parts of silica sol.

By adopting the technical scheme, the silica sol in the hybrid organic silicon resin is used as an inorganic phase to be hybridized with an organic phase of siloxane containing vinyl and siloxane containing epoxy, silica sol particles and the organic phase form a compact hybrid network structure, the crosslinking degree between coatings is increased, the inorganic rigid structure of the silica sol reduces the volume shrinkage rate of the organic silicon resin in the UV curing process, the adhesive force between the coatings and a base material is improved, and the wear resistance, hardness, flame retardance and electrical performance of the coatings are also improved by adding the inorganic nano silica sol material. The organosilicon modified urethane acrylate can be subjected to free radical photocuring, cationic photocuring and moisture curing simultaneously, so that the coating can be subjected to multiple curing simultaneously, and the synergistic effect of the organosilicon resin and the organosilicon modified urethane acrylate is hybridized simultaneously, thereby not only solving the problem of insufficient curing of the coating caused by oxygen inhibition, but also reducing the phenomenon that the coating is too fast dried on the surface and cannot be fully cured caused by moisture resistance, and by adding the hybridized organosilicon resin, the adhesive force of the coating and a base layer is enhanced, the hardness, wear resistance, flame retardance and electrical property of the coating are improved, and the comprehensive performance of the coating is improved.

Preferably, the siloxane containing vinyl is at least one of vinyltrimethoxysilane and vinyltriethoxysilane.

By adopting the technical scheme, the vinyltrimethoxysilane and the vinyltriethoxysilane can provide double bonds for free radical photocuring, and the vinyltrimethoxysilane and the vinyltriethoxysilane can be used as vinyl silane coupling agents, so that the crosslinking degree of the coating is improved, and the curing efficiency is further improved.

Preferably, the epoxy-containing siloxane comprises at least one of 3- (2,3-glycidoxy) propyltrimethoxysilane, 3- (2,3-glycidoxy) propylmethyldimethoxysilane, and 3- (2,3-glycidoxy) propyltriethoxysilane.

By adopting the technical scheme, the 3- (2,3-epoxypropoxy) propyl trimethoxy silane, the 3- (2,3-epoxypropoxy) propyl methyl dimethoxy silane and the 3- (2,3-epoxypropoxy) propyl triethoxy silane can provide epoxy groups to carry out cationic photocuring, and can be used as epoxy silane coupling agents, so that the adhesive force between a coating and a base material is improved, and the wear resistance of the coating is further improved.

Preferably, the silica sol is acidic silica sol with the particle size of 10nm-50nm or alkaline silica sol with the particle size of 10nm-50 nm.

By adopting the technical scheme, when the particle size of the silica sol is 10nm-50nm, the agglomeration phenomenon of the particles can be reduced, the crosslinking degree between the silica sol and siloxane is improved, the hardness and the wear resistance of the coating are further improved, and meanwhile, both the alkaline silica sol and the acidic silica sol can be used as inorganic phases to be hybridized with organic silicon resin.

Preferably, the hybrid organic silicon resin raw material further comprises 1-5 parts of citric acid, 1-5 parts of cellulose and 0.5-2 parts of sodium hypophosphite, and the silica sol is mixed with the citric acid, the cellulose and the sodium hypophosphite in advance to form silica sol composite liquid.

By adopting the technical scheme, under the high-temperature condition, the carboxyl group of the citric acid and the-OH group of the cellulose form a firm ester bond under the catalytic action of the citric acid and the cellulose in the presence of sodium hypophosphite. The residual free carboxyl of the citric acid has hydrogen bond action with-OH groups of the silica sol, so that a 'cellulose-citric acid-silica sol' network structure is formed, the interaction force of the silica sol and cellulose is enhanced, the silica sol particles can be dispersed by the hydrogen bond action of the citric acid and the silica sol, the agglomeration phenomenon of the silica sol particles is reduced, the dispersibility of the silica sol in a coating system is improved, and the wear resistance of the coating is further improved. Meanwhile, the crosslinking degree between the silica sol and the siloxane is improved, and the adhesive force between the coating and the base layer is further enhanced.

Preferably, the preparation method of the hybrid organic silicon resin comprises the following steps: dissolving siloxane containing vinyl and siloxane containing epoxy in a solvent, adjusting the pH to 2-4, then adding a pH buffer to form a mixed solution, mixing the mixed solution with silica sol for reaction for 5-8h, and finally performing dehydration treatment to obtain the hybrid organic silicon resin.

By adopting the technical scheme, the siloxane containing vinyl and the siloxane containing epoxy are mixed in advance, and the mixed solution is neutralized by adding the PH buffering agent, so that the mixed solution is thickened. And adding silica sol, and hydrolyzing and condensing to prepare the hybrid organic silicon resin, so that the inorganic nano silica sol is uniformly dispersed in the hybrid organic silicon resin, and finally the hybrid organic silicon resin with excellent performance is obtained.

Preferably, the organosilicon modified polyurethane acrylate is prepared from the following raw materials in parts by weight: 40-70 parts of polyol, 0.05-1 part of catalyst, 48-78 parts of isocyanate trimer, 3-10 parts of hydroxyl acrylate monomer, 3-10 parts of hydroxyl-containing oxetane, 5-15 parts of amino-containing silane coupling agent and 0.05-1 part of polymerization inhibitor.

By adopting the technical scheme, double bonds introduced by the reaction of partial NCO groups in the isocyanate tripolymer structure and hydroxyl acrylate monomers can be subjected to free radical photocuring, epoxy groups introduced by the reaction of partial NCO groups in the isocyanate tripolymer structure and hydroxyl-containing oxetane can be subjected to cationic photocuring, and alkoxy groups introduced by the reaction of partial NCO groups in the isocyanate tripolymer structure and amino-containing silane coupling agents can be subjected to moisture curing, so that the organosilicon modified polyurethane acrylate can be subjected to free radical photocuring, cationic photocuring and moisture curing simultaneously.

Preferably, the isocyanate trimer comprises at least one of HDI trimer, IPDI trimer, and TDI trimer.

By adopting the technical scheme, the HDI tripolymer, the IPDI tripolymer and the TDI tripolymer are subjected to trimerization reaction under the catalytic action to form the tripolymer containing an isocyanurate ring. HDI tripolymer, IPDI tripolymer and TDI tripolymer can react with corresponding components to introduce double bond, epoxy group and alkoxy.

Preferably, the hydroxy acrylate monomer comprises at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxybutyl methacrylate;

the hydroxyl-containing oxetane comprises at least one of 3-methyl-3-hydroxymethyl oxetane, 3-ethyl-3-hydroxymethyl oxetane, 3-hydroxyoxetane and 3-phenyl-3-hydroxy-1-oxetane;

the silane coupling agent containing amino comprises at least one of gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropylmethyldiethoxysilane and gamma-aminopropylmethyldimethoxysilane.

In a second aspect, the application provides a preparation method of a multi-curing conformal coating, which adopts the following technical scheme: a preparation method of a multi-curing conformal coating comprises the following steps: mixing the reactive diluent, the photoinitiator and the auxiliary agent, introducing nitrogen, adding the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin into the mixture, and stirring to obtain the coating.

By adopting the technical scheme, the reactive diluent reduces the viscosity of a system in the reaction, improves the crosslinking degree of the hybrid organic silicon resin and the organic silicon modified polyurethane acrylate, and plays a toughening role in the coating. The photoinitiator can initiate a curing reaction, and under the protection of nitrogen, the organosilicon modified urethane acrylate, the hybrid organosilicon resin and the mixture are mixed and reacted, so that the stability of the coating can be improved.

In summary, the present application has the following beneficial effects:

1. because the organosilicon modified urethane acrylate and the hybrid organosilicon resin are used, free radical photocuring and cationic photocuring can be simultaneously carried out under the condition of UV illumination, the cationic photocuring reduces the influence of oxygen inhibition on the free radical photocuring, and the free radical photocuring efficiency is improved. The cationic photocuring has lower volume shrinkage, reduces the influence of the free radical photocuring volume shrinkage on the adhesive force, and simultaneously, the alkoxy in the organosilicon modified polyurethane acrylate and the hybrid organosilicon resin can be subjected to moisture curing and multiple curing simultaneously, so that the curing efficiency and the curing degree of the coating are improved, and the comprehensive performance of the coating is improved.

2. In the application, the inorganic nano silica sol hybrid organic silicon resin is preferably adopted, and the hydroxyl on the surface of the silica sol and the silane coupling agent are subjected to hydrolysis condensation reaction to form a hybrid network structure, so that the hardness, the wear resistance, the flame retardance and the electrical property of the coating are improved. And the coupling structure of the hybrid organic silicon resin also plays a role in coupling the coating and the base material, and the adhesive force of the coating to the base material is enhanced.

3. According to the preparation method, citric acid and cellulose are added into silica sol in advance to form silica sol composite liquid, so that the citric acid, the cellulose and the silica sol form a cellulose-citric acid-silica sol network structure, the dispersibility of the silica sol in a coating system is improved, the phenomenon of silica sol particle agglomeration is reduced, the adhesion of a coating to a base material is enhanced, and the wear resistance and the strength of the coating are further improved.

Detailed Description

The present application will be described in further detail with reference to examples.

In this embodiment, there are no other special cases, and the following components are used:

the photoinitiator is prepared by mixing a free radical photoinitiator and a cationic photoinitiator, wherein the free radical photoinitiator is selected from the group consisting of a free radical photoinitiator 184 and a free radical photoinitiator TPO; the cationic photoinitiator was chosen to be a triarylsulfonium salt. The mass ratio of the radical photoinitiator 184 to the radical photoinitiator TPO to the triarylsulfonium salt is 3.

The reactive diluent is a mixed solution of isobornyl acrylate, tetrahydrofuran acrylate and butyl vinyl ether, and the mass ratio of isobornyl acrylate to tetrahydrofuran acrylate to butyl vinyl ether is 29.

The auxiliary agents include, but are not limited to, defoamers, wetting agents, leveling agents, water scavengers, fluorescent agents, and mildewcides.

Furthermore, the auxiliary agent is preferably a mixed solution of a defoaming agent BYK-110 and a wetting agent BYK-378, and the mass ratio of the defoaming agent BYK-110 to the wetting agent BYK-378 is 0.2.

The catalyst includes, but is not limited to, dibutyltin dilaurate, dibutyltin diacetate, tin naphthenate, stannous octoate, dibutyltin bis (dodecylthio) and dibutyltin dithiolate, and dibutyltin dilaurate is more preferable.

The polyol includes, but is not limited to, polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, and further preferably polytetrahydrofuran ether glycol PTMEG1000.

The pH buffer is triethanolamine.

The solvent is ethanol.

Hydroquinone is selected as the polymerization inhibitor.

Preparation example of Silicone-modified urethane acrylate

Preparation example 1

An organosilicon modified urethane acrylate is prepared from the following raw materials in parts by weight: 58g of polyol, 0.1g of catalyst, 58g of isocyanate trimer, 6g of hydroxyl acrylate monomer, 6g of hydroxyl-containing oxetane, 10g of amino-containing silane coupling agent and 0.1g of polymerization inhibitor.

Wherein the polyalcohol is polytetrahydrofuran ether glycol PTMEG1000, the catalyst is dibutyltin dilaurate, the isocyanate tripolymer is HDI tripolymer, the hydroxy acrylate monomer is hydroxyethyl acrylate, the hydroxyl-containing oxetane is 3-methyl-3-hydroxymethyl oxetane, the amino-containing silane coupling agent is 3-aminopropyltrimethoxysilane, and the polymerization inhibitor is hydroquinone.

The preparation method of the organic silicon modified polyurethane acrylate comprises the following steps:

s1: polyol and catalyst were added to the reactor and the temperature was raised to 45 ℃.

S2: isocyanate tripolymer is added dropwise, reaction is carried out for 1 hour, and the temperature is increased to 75 ℃ after the NCO value is measured to be 10 percent.

And S3, respectively dropwise adding 3g of hydroxyl acrylate monomer, 5g of amino-containing silane coupling agent, 3g of hydroxyl-containing oxetane and 0.1g of hydroquinone, and carrying out heat preservation reaction until the NCO value reaches 5% to obtain the organosilicon modified polyurethane acrylate.

Preparation example 2

An organosilicon modified urethane acrylate is prepared from the following raw materials in parts by weight: 40g of polyol, 0.05g of catalyst, 48g of isocyanate trimer, 3g of hydroxyl acrylate monomer, 3g of hydroxyl-containing oxetane, 5g of amino-containing silane coupling agent and 0.05g of polymerization inhibitor.

Wherein the polyalcohol is polytetrahydrofuran ether glycol PTMEG1000, the catalyst is dibutyltin dilaurate, the isocyanate tripolymer is IPDI tripolymer, the hydroxyl acrylate monomer is hydroxyethyl acrylate, the hydroxyl-containing oxetane is 3-methyl-3-hydroxymethyl oxetane, the amino-containing silane coupling agent is 3-aminopropyltrimethoxysilane, and the polymerization inhibitor is hydroquinone.

s1: polyol and catalyst 0 were added to the reactor and the temperature was raised to 45 ℃.

S2: isocyanate tripolymer is added dropwise, reaction is carried out for 1 hour, and the temperature is increased to 75 ℃ after the NCO value is measured to be 8 percent.

And S3, respectively dropwise adding a hydroxyl acrylate monomer, an amino-containing silane coupling agent, hydroxyl-containing oxetane and hydroquinone, and carrying out heat preservation reaction until the NCO value is measured to be 4% to obtain the organic silicon modified polyurethane acrylate.

Preparation example 3

An organosilicon modified urethane acrylate is prepared from the following raw materials in parts by weight: 70g of polyol, 0.05g of catalyst, 78g of isocyanate trimer, 10g of hydroxyl acrylate monomer, 10g of hydroxyl-containing oxetane, 15g of amino-containing silane coupling agent and 0.1g of polymerization inhibitor.

Wherein the polyalcohol is polytetrahydrofuran ether glycol PTMEG1000, the catalyst is dibutyltin dilaurate, the isocyanate tripolymer is TDI tripolymer, the hydroxyl acrylate monomer is hydroxyethyl acrylate, the oxetane containing hydroxyl is 3-methyl-3-hydroxymethyl oxetane, the silane coupling agent containing amino is 3-aminopropyl trimethoxy silane, and the polymerization inhibitor is hydroquinone.

S2: isocyanate tripolymer is added dropwise, reaction is carried out for 1 hour, and the temperature is increased to 75 ℃ after the NCO value is measured to be 5 percent.

And S3, respectively dropwise adding a hydroxyl acrylate monomer, an amino-containing silane coupling agent, hydroxyl-containing oxetane and hydroquinone, and carrying out heat preservation reaction until the measured NCO value reaches 2% to obtain the organosilicon modified polyurethane acrylate.

Preparation example 4

The organic silicon modified polyurethane acrylate is prepared from the following raw materials in parts by weight: 58g of polyol, 0.1g of catalyst, 58g of isocyanate trimer, 6g of hydroxyl acrylate monomer, 6g of hydroxyl-containing oxetane, 10g of amino-containing silane coupling agent and 0.1g of polymerization inhibitor.

Preparation of hybrid Silicone resin

Preparation example 5

The hybrid organic silicon resin is prepared from the following raw materials in parts by weight: 5g of vinyl-containing siloxane, 5g of epoxy-containing siloxane and 10g of silica sol.

Wherein, the siloxane containing vinyl is vinyltrimethoxysilane, the siloxane containing epoxy is 3- (2,3-glycidoxy) propyltrimethoxysilane, and the particle size of the silica sol is 10nm-20nm.

A preparation method of hybrid organic silicon resin comprises the following steps:

5g of vinyl-containing siloxane and 5g of epoxy-containing siloxane were dissolved in ethanol, acetic acid was added to adjust the pH to 3, and then 0.2g of triethanolamine was added to form a mixed solution. And adding 10g of silica sol into the mixed solution, reacting for 7 hours at the temperature of 40 ℃, and dehydrating to obtain a transparent solution, thus obtaining the hybrid organic silicon resin.

Preparation examples 6 to 7

Preparation examples 6 to 7 differ from preparation example 5 in the content of each component in the raw material of the hybrid silicone resin, which is specifically shown in table 1.

Table 1: ingredient content tables of preparation examples 5 to 7

Preparation example 8

Preparation example 8 differs from preparation example 5 in that vinyltrimethoxysilane and 3- (2,3-glycidoxy) propyltrimethoxysilane were replaced by the same amount of 3- (2,3-glycidoxy) propyltriethoxysilane, respectively, and the particle size of the silica sol was 40nm to 50nm.

Preparation example 9

Preparative example 9 differs from preparative example 5 in that vinyltrimethoxysilane in the starting material of the hybrid silicone resin is replaced with an equal amount of vinyl-terminated polydimethylsiloxane having a molecular weight of 186.4, cas number: 68083-19-2.

Preparation example 10

Preparation example 10 differs from preparation example 5 in that 3- (2,3-glycidoxy) propyltrimethoxysilane in the raw material of the hybrid silicone resin was replaced with the same amount of epoxy-modified polydimethylsiloxane having a molecular weight of 10000.

Preparation example 11

Preparation example 11 differs from preparation example 5 in that the silica sol in the raw material of the hybrid silicone resin is replaced with an equal amount of silica sol having a particle size of 80nm to 90 nm.

Preparation example 12

Preparation 12 differs from preparation 5 in that:

the raw materials of the hybrid organic silicon resin also comprise 3g of citric acid, 3g of cellulose solution and 1.5g of sodium hypophosphite solution.

A method for preparing a hybrid silicone resin, comprising the steps of:

s1, mixing 3g of citric acid, 3g of cellulose and 1.5g of sodium hypophosphite in advance, reacting for 5min at 160 ℃, then mixing with 10g of silica sol, and stirring for 10min at the speed of 300r/min to form the silica sol composite solution.

S2: 5g of a vinyl-containing siloxane and 5g of an epoxy-containing siloxane were dissolved in ethanol, acetic acid was added to adjust the pH to 3, and then 0.2g of triethanolamine was added to form a mixed solution. And finally, mixing the mixed solution with the silica sol composite solution, reacting for 7 hours at the temperature of 40 ℃, and dehydrating to obtain the hybrid organic silicon resin.

Preparation examples 13 to 14

Preparation examples 13-14 differ from preparation example 12 in the content of each component in the raw material of the hybrid silicone resin, as shown in table 2.

Table 2: ingredient content tables of preparation examples 12 to 14

Preparation example 15

Preparation 15 differs from preparation 12 in that the hybrid silicone resin raw material does not use citric acid and sodium hypophosphite, and cellulose is directly mixed with silica sol.

Preparation example 16

Preparation 16 differs from preparation 12 in that cellulose and sodium hypophosphite were not used in the hybrid silicone resin raw material and citric acid was directly mixed with the silica sol.

Preparation example 17

Preparation 17 differs from preparation 12 in that sodium hypophosphite is not used in the hybrid silicone resin raw material, and the preparation method of the hybrid silicone resin comprises the following steps:

s1, mixing citric acid and cellulose, reacting for 5min at 160 ℃, then mixing with silica sol, and stirring for 10min at the speed of 300r/min to form silica sol mixed liquor.

S2: dissolving siloxane containing vinyl and siloxane containing epoxy in ethanol, adding acetic acid to adjust pH to 3, and adding triethanolamine to obtain a mixed solution. And finally, mixing the mixed solution with the silica sol mixed solution, reacting for 7 hours at the temperature of 40 ℃, and dehydrating to obtain the hybrid organic silicon resin.

Preparation example 18

Preparation 18 differs from preparation 12 in that the amount of cellulose added to the hybrid silicone resin raw material was 10g.

Preparation example 19

Preparation 19 differs from preparation 12 in that the amount of citric acid added to the hybrid silicone resin starting material was 10g.

Example 1

A multi-curing conformal material comprises the following raw materials: 35g of organic silicon modified polyurethane acrylate, 5g of hybrid organic silicon resin, 53g of reactive diluent, 6.5g of photoinitiator and 0.5g of auxiliary agent; the organic silicon modified polyurethane acrylate in the embodiment 1 is prepared by the preparation example 1, and the hybrid organic silicon resin in the embodiment 1 is prepared by the preparation example 5. The active diluent is preferably a mixed solution of isobornyl acrylate, tetrahydrofuran acrylate and butyl vinyl ether, the photoinitiator is a mixed solution of a radical photoinitiator 184, a radical photoinitiator TPO and triarylsulfonium salt, and the auxiliary agent is a mixed solution of an antifoaming agent and a wetting agent.

A preparation method of a multi-curing conformal coating comprises the following steps:

s1, adding 29g of isobornyl acrylate, 9g of tetrahydrofuran acrylate, 15g of butyl vinyl ether, 3g of radical photoinitiator 184, 2g of radical photoinitiator TPO, 1.5g of triarylsulfonium salt, 0.2g of defoaming agent and 0.3g of wetting agent into a reactor to form a mixed solution, and stirring at the speed of 300r/min for 30min.

And S2, under the protection of nitrogen, adding 35g of organic silicon modified polyurethane acrylate and 5g of hybrid organic silicon resin into the mixed solution, mixing, and stirring at the speed of 300r/min for 30min to obtain the coating.

Examples 2 to 5

Examples 2-5 differ from example 1 in the amounts of the components in the raw materials of the multi-cure conformal coating material, as shown in Table 3.

Table 3: ingredient content tables of examples 1 to 5

Examples 6-19 differ from example 3 in the source of the silicone-modified urethane acrylate and hybrid silicone resin, as shown in table 4.

Table 4: component Source tables in examples 6-19

Comparative example 1

This comparative example differs from example 3 in that the silicone-modified urethane acrylate in the coating stock was replaced with an equal amount of hybrid silicone resin.

Comparative example 2

This comparative example differs from example 3 in that the hybrid silicone resin in the coating feedstock was replaced with an equal amount of silicone-modified urethane acrylate

Comparative example 3

This comparative example differs from example 3 in that the silicone-modified urethane acrylate in the coating raw material was replaced with an equivalent amount of a commercially available UV moisture dual cure urethane acrylate, model number basf LR9000.

Comparative example 4

This comparative example differs from example 3 in that the silicone-modified urethane acrylate in the coating raw material was replaced with an equal amount of a commercially available UV moisture dual cure urethane acrylate, model basf LR9000, and the hybrid silicone resin was replaced with an equal amount of a commercially available UV moisture dual cure urethane acrylate, model basf LR9000.

Comparative example 5

The difference between the comparative example and example 3 is that the hybrid silicone resin in the coating raw material does not use silica sol, but vinyl-containing siloxane and epoxy-containing siloxane are directly dissolved in ethanol, acetic acid is added to adjust the pH to 3, then 0.2g triethanolamine is added to form a mixed solution, and finally the mixed solution is dehydrated to prepare the silicone resin.

Comparative example 6

This comparative example differs from example 3 in that the amount of silica sol added to the hybrid silicone resin in the coating raw material was 30g.

Performance test

The following property tests were performed on the coatings provided in examples 1 to 19 and comparative examples 1 to 6 of the present application, and the test data are shown in Table 5.

1. Hardness of

Uniformly coating a film with the thickness of 100 mu m on a metal sample plate with the thickness of 10cm multiplied by 10cm to serve as a sample, curing for 10s by UV, curing for 72h at normal temperature, and then testing the hardness of the sample by a Baige method, recording data and analyzing, wherein the test method adopts GB2411-2008 "Plastic and hard rubber to measure indentation hardness (Shore hardness) by using a hardness tester.

2. Efficiency of curing

A film with the thickness of 100 mu m is uniformly coated on a metal template with the thickness of 10cm multiplied by 10cm to be used as a sample, after the sample is cured for 10s by UV, the sample is cured for 24h, 48h and 72h at normal temperature, the hardness of the coating film is tested according to the hardness test method, and data are recorded and analyzed. So as to ensure that the hardness does not change along with the time, and the required time represents the curing efficiency of the coating film, and the unit is h.

3. Adhesion force

A film with the thickness of 100 microns is uniformly coated on a metal sample plate with the thickness of 10cm multiplied by 10cm by adopting ASTM D3359 Method B adhesion test standard to be used as a sample, the sample is cured for 10 seconds by UV and then cured for 72 hours at normal temperature, and then the sample is respectively tested by a Baige Method, and data are recorded and analyzed.

4. Flexibility

According to GB/T6742-2007 Standard for bending tests of colored paint and varnish, a cylindrical bending tester of the paint film is selected to test the flexibility of the paint film.

5. Environmental resistance

1. High temperature and high humidity

The test was carried out according to the test method of section 2.6.11.1 in the handbook of IPC-TM-650 test methods. And (3) testing temperature: the coating service time was checked at 85 ℃ and 95% humidity.

2. Thermal shock

The samples were tested according to the test method of section 2.6.7.1 in the manual of IPC-TM-650 test methods, under the following test conditions: temperatures-65-125 [ -85 ° F-257 ° F ], test the paint cycle life. After the temperature cycling test is completed, the coated test carrier should be placed under a baseline condition of temperature 25 + -5 deg.C [77 + -9F ] and humidity 50 + -5% for 24 hours. Finally, the appearance is evaluated, and the dielectric withstand voltage is tested.

3. Mould-proof

The ability of the sample to resist the growth of mold is determined according to subsection 2.6.1.1 of IPC-TM-650 test methods handbook.

6. Flammability of

The cured conformal coating layer should be tested for flame retardancy as detailed in the UL94 flame retardancy test method. Flame retardancy is rated according to its flame retardancy. The flame retardant grade (from weak to strong according to the flame retardant property) is gradually increased from HB, V-2,V-1 to V-0.

7. Electrical performance

1. Volume resistivity

The volume resistivity of the conformal coating was tested according to ASTM D257-2021 Standard test methods for direct Current resistance or conductivity of insulating materials.

2. Insulation resistance in humid environment

The test method is as in section 2.6.3.4 of IPC-TM-650 test method. After completion of the temperature and humidity test cycle, the coated test specimens were placed under the reference conditions of a temperature of 25. + -. 5 ℃ and a relative humidity of 50. + -. 5% for 24 hours. The appearance was evaluated and the medium was tested for withstand voltage during the humidity test, after the humidity test was completed and left under the reference condition for another 1 to 2 hours, and after being left under the reference condition for 24 hours, after being left under the reference condition for 24 hours.

3. Dielectric strength

The dielectric strength of the samples was tested according to HG/T3330-2012 "insulating paint film breakdown Strength test" standard.

Table 5: paint detection data sheet

The detection results of the examples 1 to 7 show that the coating has good service performance, the comprehensive performance of the coating is improved along with the increase of the addition amount of the hybrid organic silicon resin, and the coating has higher hardness, more excellent flame retardance and electrical performance and more excellent adhesive force.

Compared with the example 3, in the example 8, the HDI trimer in the organosilicon modified polyurethane acrylate is replaced by the same amount of IPDI trimer, the vinyltrimethoxysilane in the hybrid organosilicon resin is replaced by the same amount of vinyltriethoxysilane, and the 3- (2,3-glycidoxy) propyltrimethoxysilane is replaced by the same amount of 3- (2,3-glycidoxy) propyltriethoxysilane, and according to the detection result, the IPDI has higher rigidity than the HDI, so that the hardness of the coating is improved. The curing time of the coating of example 8 was increased because the vinyl ethoxy silane coupling agent was selected in preparation 8, and the curing efficiency of vinyltrimethoxysilane was higher than that of vinyltriethoxysilane, probably because the steric hindrance of methoxysilane was smaller than that of ethoxysilane.

Compared with example 3, example 9 adopts other vinyl-containing siloxanes, and example 10 adopts other epoxy-containing siloxanes, and the detection results show that the comprehensive performance of the coating is reduced and the curing efficiency is reduced, which is probably because vinyl polydimethylsiloxane and epoxy-modified polydimethylsiloxane cannot form an effective organic-inorganic hybrid structure with silica sol, but a physically blended compound structure, so that the effect of improving the performance of the coating is low, and the organic-inorganic hybrid structure can obviously improve the comprehensive performance of the coating. In example 11, the particle size of the silica sol was changed, and the results of the test showed that the performance of the coating material was deteriorated, indicating that the selection of the silica sol having an appropriate particle size is also important for the performance of the coating material.

Compared with the embodiment 3, the organic silicon resin adopted in the embodiments 12 to 14 is hybridized by the inorganic nano silica sol, and the silica sol is modified by citric acid and cellulose. According to the detection result, the combination of citric acid and cellulose and the modification of silica sol have better comprehensive performance of the coating, the network structure formed by the citric acid, the cellulose and the silica sol improves the curing efficiency, the adhesive force between the coating and the base material is increased, and the high-temperature environment resistance of the coating is further enhanced.

Compared with the example 12, the lack of any one of the citric acid, the cellulose and the sodium hypophosphite in the examples 15 to 17 can cause poor coating performance, which shows that the citric acid, the cellulose and the sodium hypophosphite can be better combined with the silica sol only through the mutual combination action of the citric acid, the cellulose and the sodium hypophosphite, the crosslinking degree of the silica sol and a coating system is improved, the adhesion force of the coating and a base material is enhanced, and the wear resistance and the hardness of the coating are further improved.

Compared with example 12, the excessive citric acid and cellulose used in the hybrid organic silicon resin in examples 18-19 can be found from the detection result that the coating performance is not improved, but the coating performance is slightly influenced, and the coating prepared by using the citric acid and cellulose in example 12 has better performance.

The raw material in comparative example 1 did not use silicone-modified urethane acrylate, and the raw material in comparative example 2 did not use hybrid silicone resin, as in example 3. According to the detection result, the coating simultaneously added with the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin has more excellent comprehensive performance, higher curing efficiency, stronger adhesive force between the coating and the base material and better environmental resistance of the coating.

In contrast to example 3, comparative example 3 used a conventional UV curable coating with the addition of a hybrid silicone resin. Comparative example 4 used a conventional UV curable coating, not containing a hybrid silicone resin. According to the detection result, the comprehensive performance of the paint added with the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin is more excellent, and the paint prepared by combining the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin can be subjected to free radical photocuring, cationic photocuring and moisture curing simultaneously, so that the curing efficiency is improved, and the problem that the free radical photocuring shadow part of the paint cannot be cured is solved. And the organic silicon resin is hybridized by the inorganic nano silica sol, so that the coating has the performance of a nano coating, the hardness and the wear resistance of the coating are improved, and the coating has more excellent environmental resistance, flame retardance and electrical performance.

Compared with example 3, the hybrid organic silicon resin in the comparative example 5 does not contain silica sol, and the detection result shows that the comprehensive performance of the coating is reduced, and the adhesion between the coating and the base material is obviously reduced. The hybrid organic silicon resin obtained by mixing and reacting the organic silicon resin with the silica sol nano material has higher hardness, and an inorganic phase and an organic phase hybrid network structure is formed by crosslinking and combining an inorganic phase of the silica sol and an organic phase in the organic silicon resin, so that the curing efficiency is improved, the adhesive force between the coating and the base material is increased, and the coating has higher wear resistance and more excellent environment resistance.

Compared with example 3, the hybrid organic silicon resin in comparative example 6 uses excessive silica sol, and the detection result shows that the hardness of the coating is too high, the coating with the too high hardness is easy to generate cracking phenomenon after long-time use, and the comprehensive performance is lower than that of example 3.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The multi-curing conformal coating is characterized by being prepared from the following raw materials in parts by weight: 5-35 parts of organic silicon modified polyurethane acrylate, 5-35 parts of hybrid organic silicon resin, 40-53 parts of reactive diluent, 3-7 parts of photoinitiator and 0.1-0.5 part of auxiliary agent; the organic silicon modified polyurethane acrylate contains vinyl, epoxy, NCO group and alkoxy, and the hybrid organic silicon resin is prepared from the following raw materials in parts by weight: 3-9 parts of siloxane containing vinyl, 3-9 parts of siloxane containing epoxy and 5-13 parts of silica sol.

2. The multi-cure conformal coating of claim 1, wherein: the siloxane containing vinyl is at least one of vinyl trimethoxy silane and vinyl triethoxy silane.

3. The multi-cure conformal coating of claim 1, wherein: the siloxane containing epoxy groups comprises at least one of 3- (2,3-epoxypropoxy) propyltrimethoxysilane, 3- (2,3-epoxypropoxy) propylmethyldimethoxysilane and 3- (2,3-epoxypropoxy) propyltriethoxysilane.

4. The multi-cure conformal coating of claim 1, wherein: the silica sol is acidic silica sol with the particle size of 10nm-50nm or alkaline silica sol with the particle size of 10nm-50 nm.

5. The multi-cure conformal coating of claim 4, wherein: the hybrid organic silicon resin raw material also comprises 1-5 parts of citric acid, 1-5 parts of cellulose and 0.5-2 parts of sodium hypophosphite, and the silica sol is mixed with the citric acid, the cellulose and the sodium hypophosphite in advance to form silica sol composite liquid.

6. The multi-cure conformal coating of any one of claims 1-4, wherein: the preparation method of the hybrid organic silicon resin comprises the following steps: dissolving siloxane containing vinyl and siloxane containing epoxy in a solvent, adjusting the pH to 2-4, then adding a pH buffer to form a mixed solution, mixing the mixed solution with silica sol for reaction for 5-8h, and finally performing dehydration treatment to obtain the hybrid organic silicon resin.

7. The multi-cure conformal coating of claim 1, wherein: the organic silicon modified polyurethane acrylate is prepared from the following raw materials in parts by weight: 40-70 parts of polyol, 0.05-0.1 part of catalyst, 48-78 parts of isocyanate trimer, 3-10 parts of hydroxyl acrylate monomer, 3-10 parts of hydroxyl-containing oxetane, 5-15 parts of amino-containing silane coupling agent and 0.05-0.1 part of polymerization inhibitor.

8. The multi-cure conformal coating of claim 7, wherein: the isocyanate trimer comprises at least one of HDI trimer, IPDI trimer and TDI trimer.

9. The multi-curing conformal coating of claim 7, wherein the hydroxy acrylate monomer comprises at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxybutyl methacrylate, the hydroxyl-containing oxetane comprises at least one of 3-methyl-3-hydroxymethyl oxetane, 3-ethyl-3-hydroxymethyl oxetane, 3-hydroxyoxetane and 3-phenyl-3-hydroxy-1-oxetane, and the amino-containing silane coupling agent is at least one of 3-aminopropyltrimethoxysilane and 4-amino-3,3-dimethylbutyltrimethoxysilane.

10. A method of preparing a multi-cure conformal coating of any one of claims 1-9, wherein: the method comprises the following steps: mixing the reactive diluent, the photoinitiator and the auxiliary agent, introducing nitrogen, adding the organic silicon modified polyurethane acrylate and the hybrid organic silicon resin into the mixture, and stirring to obtain the coating.