阅读说明：本技术 低voc水性uv固化单层涂料组合物、涂覆方法和经其涂覆的基底 (Low VOC aqueous UV-curable single layer coating composition, method of coating and substrates coated therewith ) 是由 苏福章 刘海峰 罗正松 于 2018-08-23 设计创作，主要内容包括：本发明提供一种低VOC水性UV固化单层涂料组合物,其包含基于碳酸酯的聚氨酯树脂和无离子HDI型聚氨酯-丙烯酸酯树脂。本发明还提供用所述涂料组合物涂覆基底的方法以及经其涂覆的基底。(The present invention provides a low VOC aqueous UV curable monolayer coating composition comprising a carbonate based polyurethane resin and an ionic HDI free polyurethane-acrylate resin. The invention also provides a method of coating a substrate with the coating composition and a substrate coated therewith.)

1. An aqueous UV-curable single-layer coating composition comprising a carbonate-based polyurethane resin and an ionic HDI-free polyurethane-acrylate resin.

2. The aqueous UV-curable monolayer coating composition of claim 1, wherein the carbonate-based polyurethane resin comprises 45-65 wt% polycarbonate in the carbonate-based polyurethane resin.

3. The aqueous UV-curable monolayer coating composition of claim 1, wherein the carbonate-based polyurethane resin has a viscosity of about 50-500cp at 25 ℃.

4. The aqueous UV-curable monolayer coating composition of claim 1, wherein the carbonate-based polyurethane resin comprises 20 to 25 wt% of the total weight of the coating composition.

5. The aqueous UV-curable monolayer coating composition of claim 1, wherein the ionic HDI-free polyurethane-acrylate resin comprises 48 to 67 wt% of the acrylate compound in the ionic HDI-free polyurethane-acrylate resin.

6. The aqueous UV-curable monolayer coating composition of claim 1, wherein the ionic HDI-free polyurethane-acrylate resin has a weight average molecular weight of about 500-4000.

7. The aqueous UV-curable monolayer coating composition of claim 1, wherein the ion-free HDI-based polyurethane-acrylate resin has a glass transition temperature of about 120-180 ℃.

8. The aqueous UV-curable monolayer coating composition of claim 1, wherein the ionic HDI-free polyurethane-acrylate resin comprises 10 to 15 wt% of the total weight of the coating composition.

9. An aqueous UV-curable monolayer coating composition according to any preceding claim, having a VOC content of less than 420 g/L.

10. The aqueous UV-curable monolayer coating composition of claim 9, having a VOC content in the range of 100-250 g/L.

11. A method of forming a coating on a substrate comprising applying an aqueous UV-curable monolayer coating composition onto at least a portion of a substrate, wherein the aqueous UV-curable monolayer coating composition comprises a carbonate-based polyurethane resin and a non-ionic HDI-type polyurethane-acrylate resin.

12. A coated substrate comprising a substrate and an aqueous UV-curable monolayer coating composition coated on at least a portion of the substrate, wherein the aqueous UV-curable monolayer coating composition comprises a carbonate-based polyurethane resin and a non-ionic HDI-type polyurethane-acrylate resin.

13. The coated substrate of claim 12, wherein the substrate comprises a substrate formed from: polycarbonate, polycarbonate + acrylonitrile/butadiene/styrene copolymer, polycarbonate + carbon fibers or polycarbonate + glass fibers.

14. The coated substrate of claim 12 or 13, wherein the substrate is a substrate for an in-vehicle display screen, a PET protective film for a cellular phone, and a computer display screen.

Technical Field

The present invention relates to an aqueous UV-curable coating composition having a low VOC content, in particular to an aqueous UV-curable coating composition comprising a carbonate-based polyurethane resin and an ionic HDI-free polyurethane-acrylate resin. The invention also relates to a method for coating a substrate with the aqueous UV-curable coating composition and to a substrate coated therewith.

Background

Aqueous UV-curable single-coat paints for plastic substrates such as Polycarbonate (PC), polycarbonate + acrylonitrile/butadiene/styrene copolymer (PC + ABS), polycarbonate + carbon fiber (PC + CF), and polycarbonate + glass fiber (PC + GF) are very rare in 3C coatings including computer, communication and consumer electronics coatings. Such aqueous UV-curable single-coat paints have many problems, if any, such as poor adhesion, poor abrasion resistance, poor performance and appearance after boiling, and the like. Thus, there is a need for waterborne UV-curable single coat coatings that can reduce VOC content and meet the various performance requirements described above.

Disclosure of Invention

The present invention provides a low VOC aqueous UV curable monolayer coating composition comprising a carbonate based polyurethane resin and an ionic HDI free polyurethane-acrylate resin.

The present invention also provides a method of forming a coating on a substrate comprising applying a low VOC aqueous UV curable monolayer coating composition onto at least a portion of a substrate, wherein the low VOC aqueous UV curable monolayer coating composition comprises a carbonate based polyurethane resin and a non-ionic HDI polyurethane-acrylate resin.

The present invention also provides a coated substrate comprising a substrate and a low VOC aqueous UV curable monolayer coating composition coated on at least a portion of the substrate, wherein the low VOC aqueous UV curable monolayer coating composition comprises a carbonate based polyurethane resin and an ionic HDI free polyurethane-acrylate resin.

Drawings

FIGS. 1A-1D show schematic diagrams of coating delamination after adhesion testing on PC substrates.

Detailed Description

Other than in the examples, or where otherwise explicitly indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently has certain errors. This error is a corollary to the standard deviation found in its corresponding measurement method.

Moreover, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges (and inclusive of the endpoints) between the recited minimum value of 1 and the recited maximum value of 10, that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

As used in this specification and the appended claims, the articles "a," "an," and "the" include plural referents unless expressly limited to one referent.

As used herein, the weight average molecular weight (Mw) of a polymer is determined by gel permeation chromatography using appropriate standards, such as polystyrene standards.

The present invention aims to provide a single-layer aqueous coating composition with a low VOC content for PC, PC + ABS, PC + CF, PC + GF and other plastic substrates, which is UV-cured. UV curing has the advantages of short curing time, simple application equipment, high energy utilization rate, no harm to the environment and the like, so the UV curing agent is widely applied to the rapid curing of coatings, printing inks, cross-linking agents and structural materials, and is particularly suitable for surface coatings of electronic consumer products.

As used herein, the term "waterborne" means that the coating composition comprises water in an amount of at least more than 50% by weight, based on the total solvent weight in the composition.

As used herein, the term "low VOC" refers to coating compositions having a VOC content of less than 420 g/L (23 ℃, atmospheric pressure, 101.3 kPa.) preferably, the waterborne UV-curable monolayer coating compositions of the present invention have a VOC content in the range of 100 g/L (anhydrous basis).

In the present invention, the term "Volatile Organic Compound (VOC)" refers to any organic compound having a boiling point of 250 ℃ (482 ° F) or less, as measured at a standard atmospheric pressure of 101.3 kPa. Organic solvents are a typical source of VOCs.

The aqueous UV-curable single-layer coating composition according to the present invention comprises a carbonate-based polyurethane resin and an ionic HDI-free polyurethane-acrylate resin.

In the coating composition, the carbonate-based polyurethane resin is an aqueous polyurethane resin modified with polycarbonate. Typically, to prepare the coating compositions of the present invention, a carbonate-based polyurethane is used in the form of a dispersion having a solids content of about 30-40%, for example about 35% (by weight). The carbonate-based polyurethane resin includes 45 to 65 wt%, preferably 50 to 60 wt%, and more preferably 53 to 57 wt% of polycarbonate. The carbonate-based polyurethane resin has a viscosity of about 50 to 500cp at 25 ℃. The viscosity is measured using a Brookfield RVT viscometer using spindle 3 at a speed of 100rpm and at a temperature of 25 ℃.

Typically, the carbonate-based polyurethane resin is present in the coating composition in an amount of about 20 to 25 wt.%, based on the weight of the coating composition. When the content of the resin is out of this range, the rework adhesion (defined below) becomes poor.

For example, examples of such resins that may be used in the present invention include, but are not limited to, Hauthane L-3685 from Hauthaway.

In the coating composition, the non-ionic HDI type polyurethane-acrylate resin is an acrylate-modified aqueous polyurethane resin, and/or a mixture of a polyurethane resin and an acrylate compound. The term "HDI" is an abbreviation for hexamethylene diisocyanate. The nonionic HDI urethane-acrylates used herein are synthesized from materials comprising Hexamethylene Diisocyanate (HDI). Generally, to prepare the coating compositions of the present invention, the ionic HDI-free polyurethane-acrylate resin is used in the form of a dispersion having a solids content of about 45-55%, for example about 50% (by weight). The non-ionic HDI type polyurethane-acrylate resin contains 48 to 67 wt%, preferably 50 to 65 wt%, and more preferably 53 to 61 wt% of the acrylate compound in the non-ionic HDI type polyurethane-acrylate resin. The non-ionic HDI-based polyurethane-acrylate resin has a weight average molecular weight of about 500-4000, preferably about 1000-3000 (as determined by gel permeation chromatography using polystyrene standards), which imparts excellent abrasion resistance and boiling resistance to the coating composition of the present invention. The non-ionic HDI based polyurethane-acrylate resin also has a glass transition temperature (Tg) of about 120-180 deg.C, preferably about 140-160 deg.C. The glass transition temperature was determined by Dynamic Mechanical Analysis (DMA) using a TA Instruments Q800 apparatus, using a frequency of 10Hz, an amplitude of 5mm, a temperature ramp of-100 ℃ to 250 ℃ and a Tg as determined by ASTM D7028 as the peak of the tan curve.

Typically, the nonionic HDI polyurethane-acrylate resin is present in the coating composition in an amount of about 10 to 15 wt%, based on the weight of the coating composition. When the amount of the resin is less than 10% by weight, the water-boiling property of a coating layer formed from the coating composition is deteriorated. When the amount of the resin is more than 15 wt%, the hardness of a coating layer formed from the coating composition may be deteriorated.

Many commercially available ion-free HDI-type urethane-acrylate resins are useful in the present invention. Example (b)Examples of such resins useful in the present invention include, but are not limited to, O L ESTER from Mitsui^TMRA7011, and the like.

The low VOC aqueous UV curable single layer coating composition according to the present invention further comprises 1 to 3 wt% of a photoinitiator based on the weight of the coating composition, the photoinitiator used is not particularly limited as long as it can be cleaved upon light irradiation to generate radicals to initiate photopolymerization, and useful photoinitiators include, but are not limited to, benzoin derivatives, benzil ketal derivatives, dialkoxyacetophenones, α -hydroxyalkylphenones, α -aminoalkylphenones, acylphosphine hydrides, esterified oxime ketone compounds, aryl peroxide compounds, halogenated methyl aryl ketones, organic sulfur compounds, benzoic acid esters, etc., two or more photoinitiators may be selected as necessary.

Many commercially available photoinitiators are useful in the present invention. For example, examples of photoinitiators useful in the present invention include, but are not limited to: 819DW from IRGACURE, 2959 from IRGACURE, 184/TPO/BP/MBF from Ciba, KIP160 from IGM, and any combination thereof.

The low VOC aqueous UV curable single layer coating composition according to the present invention comprises about 45-60 wt% water. The low VOC aqueous UV curable single layer coating composition according to the present invention further comprises a co-solvent. The solvent used is not particularly limited and can be any organic solvent known to those skilled in the art including, but not limited to, aliphatic or aromatic hydrocarbons such as Solvesso 100^TMAlcohols, such as butanol, isopropanol or 2-butoxyethanol, esters, such as ethyl acetate, butyl acetate or isobutyl acetate, ketones, such as acetone, methyl isobutyl ketone or butanone, ethers, ether alcohols or ether esters, such as ethyl 3-ethoxypropionate, or any mixtures of the above. The solvent is generally used in an amount of about 5 to 15 weight percent of the coating composition.

The low VOC aqueous UV curable single layer coating composition according to the present invention further comprises one or more other additives including, but not limited to, wetting agents, dispersants, pH adjusters, pigments, fillers, defoamers, rheology modifiers, and the like. The types of these additives are well known to those skilled in the art and the amounts used are readily determined by those skilled in the art according to the actual requirements.

The low VOC aqueous UV curable monolayer coating composition according to the present invention can be applied to at least a portion of a substrate by any technique known in the art including, for example, spray, roll, flow, dip/dip, brush or flow coating methods. Then, UV curing is applied to the formed coating film, which can be achieved, for example, by the following steps: baking at 60-80 deg.C for about 10-15min to volatilize solvent and water, and then applying UV energy of 700 mJ/cm²The light intensity is 100-300mW/cm²The UV irradiation is performed at the irradiation intensity of (a). The coating film thickness is typically in the range of 15-20 μm.

The low VOC aqueous UV curable single layer coating composition according to the present invention can be applied to any substrate. The substrate may include, but is not limited to, tile, wood, leather, stone, glass, alloys, paper, plastic, fiber, cotton, and the like, preferably including a plastic substrate. The plastic substrate is especially used for electronic displays of electronic products, such as vehicle-mounted display screens, mobile phones, computers and the like. The plastic substrate may be formed of: polycarbonate (PC), polycarbonate + acrylonitrile/butadiene/styrene copolymer (PC + ABS), polycarbonate + carbon fibers (PC + CF) or polycarbonate + glass fibers (PC + GF).

The following numbered clauses outline some aspects of the invention:

1. an aqueous UV-curable single-layer coating composition comprising a carbonate-based polyurethane resin and an ionic HDI-free polyurethane-acrylate resin.

2. The aqueous UV-curable monolayer coating composition of aspect 1, wherein the carbonate-based polyurethane resin comprises 45-65 wt% polycarbonate in the carbonate-based polyurethane resin.

3. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, wherein the carbonate-based polyurethane resin has a viscosity of about 50 to 500cp at a temperature of 25 ℃.

4. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, wherein the carbonate-based polyurethane resin comprises 20-25 wt% of the total weight of the coating composition.

5. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, wherein the ionic HDI-free polyurethane-acrylate resin comprises 48-67 wt% of the acrylate compound in the ionic HDI-free polyurethane-acrylate resin.

6. The aqueous UV-curable monolayer coating composition according to any preceding aspect, wherein the weight average molecular weight of the ionic HDI-free polyurethane-acrylate resin is from about 500 to 4000.

7. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, wherein the glass transition temperature of the ionic HDI-free polyurethane-acrylate resin is from about 120 to 180 ℃.

8. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, wherein the ionic HDI-free polyurethane-acrylate resin comprises 10-15 wt% of the total weight of the coating composition.

9. The aqueous UV-curable monolayer coating composition according to any one of the preceding aspects, having a VOC content of less than 420 g/L.

10. The aqueous UV-curable single-layer coating composition according to aspect 9, having a VOC content of 100-250 g/L.

11. A method of forming a coating on a substrate comprising applying an aqueous UV-curable monolayer coating composition onto at least a portion of a substrate, wherein the aqueous UV-curable monolayer coating composition comprises a carbonate-based polyurethane resin and a non-ionic HDI-type polyurethane-acrylate resin.

12. The method of aspect 11, wherein the aqueous UV-cured monolayer coating composition is the coating composition of any one of aspects 1 to 10.

13. A coated substrate comprising a substrate and an aqueous UV-curable monolayer coating composition coated on at least a portion of the substrate, wherein the aqueous UV-curable monolayer coating composition comprises a carbonate-based polyurethane resin and an ionic HDI-free polyurethane acrylate resin.

14. The coated substrate of aspect 13, wherein the substrate comprises a substrate formed from the group consisting of polycarbonate, polycarbonate + acrylonitrile/butadiene/styrene copolymer, polycarbonate + carbon fibers, or polycarbonate + glass fibers.

15. The coated substrate of aspect 13 or 14, wherein the substrate is a substrate useful for vehicle display screens, PET protective films for mobile phones, and computer displays.

16. The coated substrate of any one of aspects 13-15, wherein the aqueous UV-curable monolayer coating composition is the coating composition of any one of aspects 1-10.