Near-infrared light curing matte coating and preparation method thereof

Abstract

The invention provides a near-infrared light curing matte coating and a preparation method thereof, and relates to the technical field of functional coatings. The near-infrared light curing coating is irradiated and cured by near-infrared light, and the infrared light curing matte coating is prepared; the near-infrared light curing coating is prepared from the following raw materials: 20 to 70 weight percent of light curing oligomer resin, 20 to 30 weight percent of reactive diluent, 5 to 30 weight percent of filler, 1 to 8 weight percent of up-conversion particles, 0.5 to 5 weight percent of photoinitiator and 0.5 to 5 weight percent of adhesion promoter. According to the invention, the matte coating can be prepared without additionally adding a delustering agent or combining a 172nm excimer lamp and a UV electrodeless mercury lamp, and the near-infrared light curing coating is less affected by the filler and has high curing depth.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional coatings, and in particular relates to a near-infrared light-cured matte coating and a preparation method thereof. Background Art

[0002] In recent years, with the continuous improvement of people's living standards and the change of aesthetic concepts, consumption has tended to be personalized and leisure-oriented. Matte coatings, with their unique touch and high-end appearance, are widely used in wood and leather surfaces, automotive interior parts, electronic equipment casings, metal and plastic coatings, and other fields.

[0003] UV curing technology is a new energy-saving, efficient, low-pollution, and fast-curing technology. However, because UV curing is essentially solvent-free and shrinkage stress is difficult to release during the curing process, resulting in minimal coating shrinkage (less than 10%), creating a matte finish is extremely difficult. Currently, matting agents (microwax powders, inorganic powders) are primarily added to the system to achieve a matte effect. However, large matting agents often have adverse effects on coating performance. Furthermore, matting agents typically absorb or reflect UV light, hindering the curing process of the UV-curable resin and leading to incomplete crosslinking. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention proposes a near-infrared light-curable matte coating and its preparation method. The coating of the present invention has the advantages of low gloss and strong designability, and avoids the problem of existing UV-curable matte coatings that are difficult to cure due to excessive matting agents.

[0005] The technical solutions of the present invention are as follows: The first object of the present invention is to provide a near-infrared light-cured matte coating, wherein the near-infrared light-cured coating is cured by near-infrared light irradiation to obtain the infrared light-cured matte coating; the infrared light-cured matte coating has a glossiness of less than 20 at 60°; The raw material composition of the near-infrared light curing coating includes: In one embodiment, the photocurable oligomer resin is one or more of epoxy acrylate oligomer, polyurethane acrylate oligomer, and polyester acrylate oligomer; The filler is one or more of silica particles, mica powder, montmorillonite, boron nitride, talc, barium sulfate, titanium dioxide, composite iron titanium powder, zinc phosphate, aluminum tripolyphosphate, polyaniline, and calcium ion exchange silica gel; The upconversion particle is NaYF4:Yb,Tm, wherein the molar proportions of Y, Yb, and Tm elements are 70-85%, 15-30%, and 0.5-15%, respectively; The reactive diluent is one or more of isobornyl acrylate (IBOA), tetrahydrofuran acrylate (THFA), 2-hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), tripropylene glycol diacrylate (TPGDA), 1,6-hexanediol diacrylate (HDDA), and trimethylolpropane triacrylate (TMPTA); The photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (BPO), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), benzoin dimethyl ketal (BDK), bis(1-(2,4-difluorophenyl)-3-pyrrolyl) titanocene (784), and isopropylthioxanthone (ITX); The adhesion promoter is one or more of acrylated phosphate, silane coupling agent and titanate coupling agent.

[0006] In one embodiment, the raw material composition of the infrared light curing coating includes: In one embodiment, the epoxy acrylate oligomer is difunctional bisphenol A epoxy acrylate or difunctional modified epoxy acrylate; The polyurethane acrylate oligomer is a difunctional aliphatic polyurethane acrylate; The polyester acrylate oligomer is a difunctional polyester acrylate.

[0007] In one embodiment, the reactive diluent is isobornyl acrylate.

[0008] In one embodiment, the epoxy acrylate oligomer is difunctional bisphenol A epoxy acrylate; preferably, the epoxy acrylate oligomer is RY1101 produced by Kailin Ruiyang Chemical.

[0009] In one embodiment, the polyurethane acrylate oligomer is a difunctional aliphatic polyurethane acrylate; preferably, the polyurethane acrylate oligomer is 6185 produced by Changxing Chemical.

[0010] In one embodiment, the polyester acrylate oligomer is a difunctional polyester acrylate; preferably, the polyester acrylate oligomer is DR-E524 produced by Changxing Chemical.

[0011] In one embodiment, the thickness of the near-infrared light-cured matte coating is 30-1000 μm; The conditions for the near-infrared light curing are: 15-50W / cm 2 Irradiate with 980nm near-infrared light for 3-60s; The dosage of the upconversion particles is 4%; The amount of the photoinitiator is 1-2%; The amount of the adhesion promoter is 1-2%.

[0012] A second object of the present invention is to provide a method for preparing the above-mentioned near-infrared light-cured matte coating, the preparation method comprising the following steps: Step 1: Add a photoinitiator to a mixture of a photocurable oligomer resin and a reactive diluent, and after the mixture is completely dissolved, add an adhesion promoter, upconversion particles, and a filler, and disperse them uniformly to obtain a near-infrared light-curable coating; Step 2: Apply the near-infrared light-curing coating prepared in step 1 on a substrate, and cure it after irradiation with near-infrared light to form a near-infrared light-cured matte coating.

[0013] In one embodiment, in step 2, the coating method is one of roller coating, blade coating, dip coating, and shower coating; The substrate is a steel plate, a tinplate, an aluminum plate or a galvanized aluminum plate.

[0014] Beneficial effects: The present invention is a near-infrared light curing technology based on upconversion materials. The upconversion particles dispersed inside the system absorb near-infrared light and then emit ultraviolet light to induce cross-linking and curing of the photosensitive resin. The internal upconversion particles serve as light sources, dividing the curing material into countless polymerization regions centered on the particles. Only when the conversion rate of the polymerization region reaches a certain level can the overall curing of the material be achieved. This mechanism can effectively prolong the arrival of the solid-liquid conversion point, so that the curing system remains liquid and has fluidity at a higher double bond conversion rate, dissipating stress. In the process of dissipating stress, the coating produces uneven volume shrinkage, and micro-roughness is thus generated on the surface, so that the coating exhibits a matte texture. It is worth noting that the present invention does not require the additional addition of a matting agent, nor does it require the use of a 172nm excimer lamp in conjunction with a UV electrodeless mercury lamp to prepare a matte coating, and the near-infrared light-cured coating is less affected by the filler and has a higher curing depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Double bond conversion rate diagram of near infrared light curing matte coating of Examples 2, 4 and 6 Figure 2 SEM photos of the coatings of Example 2, Example 4, Comparative Example 2 and Comparative Example 4 Figure 3 The real-time double bond conversion rate and modulus of Example 2, Example 4, Comparative Example 2 and Comparative Example 4 are DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0017] Example 1 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0018] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 1000 rpm / min for 5 minutes. The mixture was then placed in a 50°C oven to accelerate the dissolution of the photoinitiator. After the photoinitiator was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 80%, 19%, and 1%, respectively), and a filler were added. The mixture was then dispersed in a high-speed disperser at 1000 rpm / min for 10 minutes, and the mixture was uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980nm near-infrared light for 60 seconds to obtain a near-infrared curing coating.

[0019] Example 2 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0020] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 1500 rpm / min for 4 minutes. The mixture was then placed in a 55°C oven to accelerate the dissolution of the photoinitiator. After the photoinitiator was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 81.5%, 18%, and 0.5%, respectively) and fillers were added. The mixture was then dispersed in a high-speed disperser at 1100 rpm / min for 4 minutes and uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980nm near-infrared light for 80 seconds to obtain a near-infrared curing coating.

[0021] Example 3 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0022] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 2000 rpm / min for 3 minutes. The mixture was then placed in a 60°C oven to accelerate the dissolution of the photoinitiator. After the mixture was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 78.5%, 20%, and 1.5%, respectively), and a filler were added. The mixture was then dispersed in a high-speed disperser at 1200 rpm / min for 4 minutes, and the mixture was uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980 nm near-infrared light for 100 seconds to obtain a near-infrared curing coating.

[0023] Example 4 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0024] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 2500 rpm / min for 2 minutes. The mixture was then placed in a 65°C oven to accelerate the dissolution of the photoinitiator. After the photoinitiator was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 76%, 22%, and 2%, respectively), and a filler were added. The mixture was then dispersed in a high-speed disperser at 1500 rpm / min for 3 minutes, and the mixture was uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980 nm near-infrared light for 120 seconds to obtain a near-infrared curing coating.

[0025] Example 5 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0026] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 2800 rpm / min for 2 minutes. The mixture was then placed in a 70°C oven to accelerate the dissolution of the photoinitiator. After the mixture was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 75%, 22%, and 3%, respectively), and a filler were added. The mixture was then dispersed in a high-speed disperser at 2000 rpm / min for 3 minutes, and the mixture was uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980 nm near-infrared light for 140 seconds to obtain a near-infrared curing coating.

[0027] Example 6 The near-infrared curing coating was prepared according to the raw material composition and parameters shown in Table 1.

[0028] A photoinitiator was added to a mixture of a photocurable oligomer resin and a reactive diluent, and the mixture was dispersed in a high-speed disperser at 3000 rpm / min for 2 minutes. The mixture was then placed in a 75°C oven to accelerate the dissolution of the photoinitiator. After the photoinitiator was completely dissolved, an adhesion promoter, upconversion particles NaYF4:Yb,Tm (the molar proportions of Y, Yb, and Tm elements were 70%, 25%, and 5%, respectively), and a filler were added. The mixture was then dispersed in a high-speed disperser at 3000 rpm / min for 2 minutes and uniformly dispersed to obtain a near-infrared light-curing coating. The prepared near-infrared light-curing coating was formed into a film on a steel plate using a film scraper, and irradiated under 980 nm near-infrared light for 160 seconds to obtain a near-infrared curing coating.

[0029] raw material Table 1 Raw material formula Comparative Example 1 The steps are the same as in Example 1, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0030] Comparative Example 2 The steps are the same as those in Example 2, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0031] Comparative Example 3 The steps are the same as those in Example 3, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0032] Comparative Example 4 The steps are the same as those in Example 4, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0033] Comparative Example 5 The steps are the same as those in Example 5, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0034] Comparative Example 6 The steps are the same as those in Example 6, except that the curing light source is changed to a UV light source with a light intensity of 500 mW / cm 2 .

[0035] Example 7 Glossiness Test The coatings prepared in Examples 1-6 and Comparative Examples 1-6 were tested for glossiness using the GB / T9754 standard. Each sample was tested five times, and the average value was used to generate the coating gloss data. The results are shown in Table 2. As can be seen, the gloss at 60° for the coatings cured with near-infrared (NIR) treatment was lower than that for the UV-cured coatings. This demonstrates that NIR curing eliminates the need for a matte agent when producing matte coatings, and that the addition of functional fillers does not affect the matte effect of NIR curing.

[0036] Table 2 Example 8 Coating upper and lower surface conversion rate test The cured coating was peeled off from the substrate, and the infrared absorption spectra of the upper and lower surfaces of the coating were measured using a total reflection Fourier transform infrared spectrometer. The double bond absorption peak areas of the cured coating and the uncured coating were compared to obtain the double bond conversion rate. The conversion rates of the upper and lower surfaces of the coatings of Examples 2, 4, and 6 were tested, and the results were as follows: Figure 1 As shown. Figure 1The conversion rates of the upper and lower surfaces of the NIR-cured coating were both greater than 85%, with a difference of less than 5%, indicating that NIR curing is minimally affected by fillers. Combined with the results in Table 2, it is clear that adding functional fillers to the system can enable the coating to maintain a matte finish while also acquiring additional functionalities such as corrosion resistance and aging resistance.

[0037] Example 9 SEM photo of coating The cured coating was peeled off from the substrate and the coating surface was observed using SEM. Figure 2 As shown. Figure 2 It is known that the surface microstructure of the coating cured by near-infrared light is uneven, while the surface microstructure of the coating cured by UV light is smooth. This indicates that the surface roughness of the near-infrared light-cured coating is high and the coating has strong diffuse reflection of the incident light.

[0038] Example 10 Study on the coating gel process The real-time double bond conversion rate and modulus of UCAP during the curing process were characterized using a modified infrared spectrometer-rheometer test equipment (Nicolet iS10 Fourier infrared spectrometer-MARS60 rheometer). The total reflection (ATR) test platform of the infrared spectrometer is shared with the rheological table (with a Peltier temperature control module), and the rheological rotor is specially designed to reflect 980 nm near-infrared light. During the test, the cured sample (150 μL) was dropped on the center of the ATR panel, and the rotor height was lowered to keep the gap between the rotor and the base plate at 300 μm. By using the oscillation time scanning mode, shearing was performed at an oscillation frequency of 1 Hz and a strain of 5%, and the storage modulus, loss modulus, normal stress and other parameters of the cured material during near-infrared light irradiation were measured. During the measurement, the 1638 cm -1 The change of double bond content was continuously monitored by observing the decrease of the double bond peak area of ​​acrylate at 1600 cm -1 The benzene ring peak was used as an internal standard.

[0039] The state of a polymerization system can be determined based on the magnitude of G' and G". When G' is greater than G", the system is in a gel state, and when G' is less than G", the system is in a fluid state. The intersection of G' and G" is defined as the gel point, representing the transition point from liquid resin to solid polymer. The gel point conversion rate (the intersection of G' and G") can indicate how well the coating dissipates shrinkage stress during the curing process. A high gel point conversion rate indicates that shrinkage stress in the coating has been fully dissipated.

[0040] Depend on Figure 3It can be seen that the gel point conversion rates of Examples 2 and 4 were 19% and 14.1%, respectively, while the gel point conversion rates of Comparative Examples 2 and 4 were only 7.3% and 4.9%. This indicates that the near-infrared light-cured coating can fully dissipate shrinkage stress during the curing process. Combined with the results in Example 9, it can be inferred that the high surface roughness of the near-infrared light-cured coating is due to the coating's ability to fully dissipate shrinkage stress during the curing process, resulting in wrinkles on the coating surface. The high roughness of the coating causes strong diffuse reflection of incident light, giving the coating a matte finish.

Claims

1. A near-infrared light-cured matte coating, characterized in that: The near-infrared light-cured coating is cured by irradiating near-infrared light to obtain the infrared light-cured matte coating; The glossiness of the infrared light-cured matte coating at 60° is less than 20; The raw material composition of the near-infrared light curing coating includes:

2. The near-infrared light-cured matte coating according to claim 1, characterized in that: The photocurable oligomer resin is one or more of epoxy acrylate oligomer, polyurethane acrylate oligomer, and polyester acrylate oligomer; The filler is one or more of silica particles, mica powder, montmorillonite, boron nitride, talc, barium sulfate, titanium dioxide, composite iron titanium powder, zinc phosphate, aluminum tripolyphosphate, polyaniline, and calcium ion exchange silica gel; The upconversion particle is NaYF4:Yb,Tm, wherein the molar proportions of Y, Yb, and Tm elements are 70-85%, 15-30%, and 0.5-15%, respectively; The active diluent is one or more of isobornyl acrylate, tetrahydrofuran acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate; The photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ketal, bis(1-(2,4-difluorophenyl)-3-pyrrolyl)titanocene, and isopropylthioxanthone; The adhesion promoter is one or more of acrylated phosphate, silane coupling agent and titanate coupling agent.

3. The near-infrared light-cured matte coating according to claim 2, characterized in that: The epoxy acrylate oligomer is difunctional bisphenol A epoxy acrylate or difunctional modified epoxy acrylate; The polyurethane acrylate oligomer is a difunctional aliphatic polyurethane acrylate; The polyester acrylate oligomer is a difunctional polyester acrylate.

4. The near-infrared light-cured matte coating according to claim 1, characterized in that: The thickness of the near-infrared light-cured matte coating is 30-1000 μm; The conditions for the near-infrared light curing are: 15-50W / cm 2 Irradiate with 980nm near-infrared light for 3-60s; The upconversion particles are used in an amount of 4 wt %; The amount of the photoinitiator is 1-2 wt%; The amount of the adhesion promoter is 1-2%.

5. A method for preparing a near-infrared light-curable matte coating according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: Step 1: Add a photoinitiator to a mixture of a photocurable oligomer resin and a reactive diluent, and after the mixture is completely dissolved, add an adhesion promoter, upconversion particles, and a filler, and disperse them uniformly to obtain a near-infrared light-curable coating; Step 2: Apply the near-infrared light-curing coating prepared in step 1 on a substrate, and cure it after irradiation with near-infrared light to form a near-infrared light-cured matte coating.

6. The method for preparing a near-infrared light-cured matte coating according to claim 5, characterized in that: In step (2), the coating method is one of roller coating, blade coating, dip coating, and shower coating; The substrate is a steel plate, a tinplate, an aluminum plate or a galvanized aluminum plate.

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