Coating compositions, crosslinked polymers, hard coatings and articles comprising hard coatings

Abstract

To provide a molecular design that achieves both of high stretchability and high excoriation resistance and a coating composition that utilizes the same.SOLUTION: A composition for coating contains a polymerizable monomer represented by formula I. In the formula I, R1 is an organic group having a specific constitutional unit. R1 has n substituent(s) X bound thereto through a constitutional unit. n is an integer of 3 or greater. X is a group represented by formula II.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] Ying, H. et al. have reported a type of urea bond called the hindered urea bond (HUB) (Ying, H., Zhang, Y., & Cheng, J., (2014), “Dynamic urea bond for the design of reversible and self-healing polymers”, Nature communications, 5(1), 1-9). Summary of the Invention [Problem to be solved by the invention]

[0002] Many photocurable hard coatings with high scratch resistance based on polymer networks with high crosslink density have been reported. However, most of these coatings have poor elongation properties due to the formation of stable covalent bonds at the crosslinking points. The elongation limit is small, and phenomena such as cracking and peeling occur during elongation. It has also been reported that lowering the crosslink density improves elongation but reduces scratch resistance.

[0003] Against this background, there is a need for molecular designs that combine good elongation and scratch resistance, and the development of coating compositions using such designs. In particular, in the field of automotive decoration, there is a demand for environmentally friendly, thermoformable decorative films with hard coating properties as an alternative to conventional solvent-based coatings. [Means for solving the problem]

[0004] The present inventors have discovered a coating composition that combines good extensibility and scratch resistance by introducing "thermoreversible HUBs" as crosslinking points in the polymer network, which form covalent bonds at room temperature but exhibit a significant shift in equilibrium toward bond cleavage at high temperatures. The HUBs are formed from an isocyanate with a chain structure and a secondary amine with an alicyclic structure.

[0005] Disclosed herein are coating compositions that include polymerizable monomers of Formula I: [ka] [In formula I, R 1 represents an organic group containing at least one structural unit selected from the group consisting of a urethane bond, a urea bond, a biuret bond, an allophanate bond, an iminooxadiazinedione ring, and an isocyanurate ring; R 1 n substituents X are bonded to the structural unit n represents an integer of 3 or more, X is a group of formula II, [ka] In formula II, * denotes R in Formula I 1 represents the point of attachment to R 2 is selected from linear alkylene and substituted linear alkylene; A represents an alicyclic structure having a nitrogen atom; In the alicyclic structure, Each carbon atom adjacent to the nitrogen atom may have one or two alkyl groups; The carbon atoms adjacent to the nitrogen atom may be bonded to each other via an alkylene group to form a ring structure. R 3 is a group having at least one polymerizable unsaturated bond.

[0006] Also disclosed herein are crosslinked polymers comprising monomer units derived from polymerizable monomers as described above, hard coatings comprising such crosslinked polymers, and articles comprising such hard coatings. [Effects of the Invention]

[0007] Coatings with high crosslink density using polyfunctional monomers with specific HUB bonds exhibit high thermal elongation at high temperatures, as the equilibrium of the HUB bonds is heavily tilted toward cleavage at high temperatures. On the other hand, at room temperature, the equilibrium is heavily tilted toward HUB bond formation, resulting in high crosslink density and high scratch resistance. This allows for the simultaneous achievement of good scratch resistance and elongation, which was previously difficult. The ability to achieve both good scratch resistance and elongation makes it possible to apply the coating to decorative films for automobiles, for example, as a highly thermally elongated hard coating. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows IR spectra of the raw materials and the product in the synthesis of HUB monomer ID:2 in the Example. [Figure 2] FIG. 1 shows IR spectra of the raw materials and the product in the synthesis of HUB monomer ID:4 in Example. [Figure 3] FIG. 1 shows IR spectra of the raw materials and the product in the synthesis of HUB monomer ID:14 in Example. [Figure 4] FIG. 1 is a diagram showing the attenuation of the peak derived from NCO in the HUB film after the TOM molding test of the example. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following detailed description illustrates specific embodiments in which the present invention may be practiced. The illustrated embodiments are not intended to be exhaustive of all embodiments of the present invention. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0010] The coating composition of this embodiment contains a polymerizable monomer having a specific HUB. The polymerizable monomer is represented by the following formula I: [ka] [In formula I, R 1 represents an organic group containing at least one structural unit selected from the group consisting of a urethane bond, a urea bond, a biuret bond, an allophanate bond, an iminooxadiazinedione ring, and an isocyanurate ring; R 1 has n substituents X bonded to it via the structural unit, and n represents an integer of 3 or more.

[0011] The substituent X in the above formula I is represented by the following formula II. [ka] [In Formula II, * represents R in Formula I] 1 represents the point of attachment to R 2 is selected from a chain alkylene and a substituted chain alkylene, A represents an alicyclic structure having a nitrogen atom, in which each carbon atom adjacent to the nitrogen atom may have one or two alkyl groups, and each carbon atom adjacent to the nitrogen atom may be bonded to each other via an alkylene to further form a ring structure, R 3 is a group having at least one polymerizable unsaturated bond.

[0012] R in Formula I 1 R may be an organic group containing a urethane bond formed by the reaction of a polyalcohol with a polyisocyanate or a urea bond formed by the reaction of a polyamine with a polyisocyanate. The polyalcohol may have three or more hydroxy groups. The polyamine may have three or more amino groups. The polyisocyanate may have two or more isocyanate groups. 1 Examples of the alkyl group include organic groups containing a structural unit derived from the reaction of a triol represented by the following general formula with an isocyanate. [ka] [In the general formula, * represents the point of attachment to the substituent X.]

[0013] R 1 R in Formula I can be an organic group containing at least one structural unit selected from the group consisting of a biuret bond, an allophanate bond, an iminooxadiazinedione ring, and an isocyanurate ring. 1 R may be an organic group containing a structural unit derived from the reaction of a diisocyanate as disclosed in Golling, Florian E., et al. "Polyurethanes for coatings and adhesives—chemistry and applications." Polymer International 68.5 (2019):848-855. The structural unit may be a structural unit having three or more isocyanate groups, and may be, for example, at least one structural unit selected from the group consisting of a biuret bond, an iminooxadiazinedione ring, and an isocyanurate ring, as represented by the following general formula: 1 n substituents X may be bonded to R via at least one structural unit selected from the group consisting of a biuret bond, an iminooxadiazinedione ring, and an isocyanurate ring, which are represented by the following general formula: At least one structural unit selected from the group consisting of a biuret bond, an iminooxadiazinedione ring, and an isocyanurate ring formed by the reaction of a diisocyanate is not limited to a monomer, but may be contained in, for example, a dimer or trimer of the structural unit. In a dimer or trimer, the number of substituents X is greater than 3 and R 1 can be bonded to [ka] [In the general formula, * represents the point of attachment to the substituent X.]

[0014] R in Formula I 1 R can be an organic group containing at least one isocyanurate ring. 1n substituents X may be bonded to R via the isocyanurate ring. The isocyanurate ring formed by the reaction of diisocyanate is not limited to that of a monomer, but may be that contained in, for example, a dimer or trimer of isocyanurate. In the case of a dimer or trimer, the number of substituents X is greater than 3 and may be bonded to R. 1 can be bonded to

[0015] R in Formula I 1 may be an organic group further including a diol-derived structural unit derived from at least one diol selected from polyether diol, polyester diol, polycarbonate diol, and polycaprolactone diol. The diol-derived structural unit may be present as a soft segment component between the structural units having the substituent X bonded thereto. R in Formula I 1 may be an organic group further containing a diol-derived structural unit derived from polycaprolactone diol. For example, an organic group in which a diol-derived structural unit derived from polycaprolactone diol exists as a soft segment component between isocyanurate rings to which substituents X are bonded includes those represented by the following general formula: [ka] [In the general formula, * represents a bonding point to the substituent X, and n 1 and n 2 represent positive numbers that may be the same or different, and R 2 is selected from linear alkylene and substituted linear alkylene, and Z is a group derived from an initiator for polycaprolactone diol formation, such as a diol.

[0016] R in Formula II 2 or R in the general formula in the previous paragraph 2 can be a chain alkylene or a substituted chain alkylene having 1 to 22 carbon atoms. 2 can be a chain alkylene having 2 to 18 carbon atoms. 2can be a chain alkylene having 4 to 12 carbon atoms. Examples of the chain alkylene having 4 to 12 carbon atoms include tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, undecamethylene, and dodecamethylene. R 2 When R is a chain alkylene having 4 to 12 carbon atoms, scratch resistance and heat elongation can be improved. 2 can be a chain alkylene having 5 or 6 carbon atoms.

[0017] A in Formula II may be a 5- to 7-membered alicyclic structure having a nitrogen atom. Examples of the 5- to 7-membered alicyclic structure having a nitrogen atom include a pyrrolidine structure, a piperidine structure, and a hexamethyleneimine structure. A may be a 6-membered alicyclic structure having a nitrogen atom. The one or two alkyl groups on each carbon atom adjacent to the nitrogen atom in the alicyclic structure of formula II may be alkyl groups having 1 to 20 carbon atoms. The alkyl groups may also be alkyl groups having 1 to 10 carbon atoms. The alkyl groups may also be alkyl groups having 1 to 5 carbon atoms. The alkyl groups are preferably methyl, ethyl, or propyl, and more preferably methyl. The carbon atoms adjacent to the nitrogen atom in the alicyclic structure of Formula II may be bonded to each other via an alkylene group to form a ring structure. The alkylene group may be an alkylene group having 1 to 5 carbon atoms. The alkylene group is preferably methylene, ethylene (an alkylene group having 2 carbon atoms), or propylene, and more preferably ethylene.

[0018] R in Formula II 3 R is a group having at least one polymerizable unsaturated bond and bonded to any position of A in formula II. 3 R may be a group having 2 to 10 carbon atoms containing an ethylenically unsaturated structural unit such as vinyl or (meth)acrylate. 3 is preferably a (meth)acrylate group.

[0019] X in formula I may be a group represented by formula III: 2 and R 3The embodiment described in formula II can be applied to [ka] [In formula III, * denotes R in Formula I 1 represents the point of attachment to R 2 is selected from linear alkylene and substituted linear alkylene; R 3 is a group having at least one polymerizable unsaturated bond, Each R 4 is H or methyl, Each R 5 are H, methyl, or groups bonded together to form an alkylene having two carbon atoms.

[0020] X in formula I can be a group represented by formula IV: 2 The embodiment described in formula II can be applied to [ka] [In formula IV, * denotes R in Formula I 1 represents the point of attachment to R 2 is selected from linear alkylene and substituted linear alkylene; R 6 is H or methyl.

[0021] X in formula I may be a group represented by formula V: 2 The embodiment described in formula II can be applied to [ka] [In formula V, * denotes R in Formula I 1 represents the point of attachment to R 2 is selected from linear alkylene and substituted linear alkylene; R 6 is H or methyl.

[0022] The polymerizable monomer represented by Formula I can be prepared by mixing a polyfunctional isocyanate raw material and a secondary amine raw material in a solvent. Examples of polyfunctional isocyanate raw materials include HDI (1,6-hexamethylene diisocyanate) trimers (trade names: Desmodur N3300, Desmodur N3800, etc.) available from Sumika Covestro Urethane Co., Ltd., and PDI (1,6-pentamethylene diisocyanate) trimers (trade names: TAKENATE D-370N, TAKENATE D-376N, TAKENATE D-3725N, etc.) available from Mitsui Chemicals, Inc. Based on NMR analysis, "Desmodur N3800" has the following chemical structure: [ka] [In the general formula, * represents the point of attachment to the HDI residue, and n 1 and n 2 represent positive numbers which may be the same or different, and Z is a group derived from an initiator for polycaprolactone formation, such as a diol. It is believed to include molecules having the formula:

[0023] Examples of polyfunctional isocyanate raw materials include the reaction product of substituted or unsubstituted linear alkylene diisocyanates, the reaction product of linear alkylene diisocyanates with polyols having three or more hydroxy groups, or mixtures thereof. Examples of reaction products of linear alkylene diisocyanates include biuret, iminooxadiazinedione, and isocyanurate. Examples of linear alkylene diisocyanates include 1,4-diisocyanatobutane, 1,6-hexamethylene diisocyanate, 1,8-diisocyanatooctane, and 1,12-diisocyanatododecane. Examples of polyols having three or more hydroxy groups include glycerin and trimethylolpropane. The polyfunctional isocyanate raw material is not limited to monomers such as isocyanurates, but can also be a mixture of reaction products of diisocyanates, including dimers, trimers, etc.

[0024] The polyfunctional isocyanate raw material may have an NCO% of 5 to 30% based on the solid content. The lower limit of the NCO% based on the solid content of the polyfunctional isocyanate raw material may be 7%, 9%, or 10%, and the upper limit of the NCO% based on the solid content of the polyfunctional isocyanate raw material may be 25%, 23%, 21%, or 15%.

[0025] The secondary amine raw material may be a compound represented by the following general formula: 3 The embodiment described in formula II can be applied to [ka]

[0026] An example of a secondary amine raw material is 2,2,6,6-tetramethyl-4-piperidyl methacrylate (trade name: FANCRYL FA-712HM) available from Showa Denko Materials Co., Ltd. (formerly Hitachi Chemical Co., Ltd.). FANCRYL FA-712HM is a secondary amine raw material that has steric hindrance due to the alicyclic structure and methyl group. In addition to this example, a secondary amine raw material having an alicyclic structure to which a group having at least one polymerizable unsaturated bond is attached can be used to form a thermoreversible HUB that forms a covalent bond at room temperature due to the steric hindrance from the alicyclic structure, but at high temperatures the equilibrium is significantly shifted toward bond cleavage. Furthermore, when, in addition to the alicyclic structure, substituents that cause steric hindrance are present on each carbon atom adjacent to the nitrogen atom, a thermoreversible HUB can be formed in which the equilibrium is significantly shifted toward bond cleavage at high temperatures.

[0027] The solvent may be a single organic solvent or a blend of solvents. The solvent is appropriately selected depending on the polyfunctional isocyanate raw material and secondary amine raw material used. Suitable solvents include alcohols (e.g., isopropyl alcohol (IPA), 2-methoxypropanol, ethanol, etc.), ketones (e.g., methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), etc.), cyclohexanone or acetone, aromatic hydrocarbons (e.g., toluene, etc.), isophorone, butyrolactone, N-methylpyrrolidone, tetrahydrofuran, esters (e.g., lactates, acetates such as butyl acetate, for example, propylene glycol monomethyl ether acetate, such as that commercially available from 3M under the trade name "3M Scotchcal Thinner CGS10" ("CGS10"), and propylene glycol monomethyl ether acetate, such as that commercially available from 3M under the trade name "3M Scotchcal Thinner CGS10" ("CGS10"). 2-butoxyethyl acetate, such as commercially available as "CGS50" ("CGS50"), diethylene glycol ethyl ether acetate (DE acetate), ethylene glycol butyl ether acetate (EB acetate), dipropylene glycol monomethyl ether acetate (DPMA), iso-alkyl esters (e.g., isohexyl acetate, isoheptyl acetate, isooctyl acetate, isononyl acetate, isodecyl acetate, isododecyl acetate, isotridecyl acetate, or other iso-alkyl esters), or combinations thereof.

[0028] The polyfunctional isocyanate raw material and the secondary amine raw material may be mixed so that 1 to 1.5 equivalents of amino groups are present relative to the isocyanate groups. It is preferable to mix the polyfunctional isocyanate raw material and the secondary amine raw material so that 1 equivalent of amino groups is present relative to the isocyanate groups. It is believed that when the polyfunctional isocyanate raw material and the secondary amine raw material are mixed, a HUB is formed and the polymerizable monomer represented by Formula I is synthesized. However, the reaction to form the HUB is essentially an equilibrium reaction, and the HUB may be cleaved depending on conditions such as temperature.

[0029] The concentration of the polymerizable monomer represented by Formula I can typically be 10, 15, or 20% by weight or more, and 100, 90, 80, 70, 60, 50, or 40% by weight or less, in the total coating composition. The coating composition containing the polymerizable monomer represented by Formula I may optionally contain various additives. For example, it may contain a curing accelerator (polymerization initiator), a crosslinking agent, a slip agent, an antifouling agent, a light stabilizer, a colorant, a solvent, etc.

[0030] To promote curing, the coating composition may further comprise at least one free-radical thermal initiator and / or photoinitiator. When such initiators are present, they typically comprise less than about 10 wt. % of the coating composition, more typically less than about 5 wt. % of the coating composition, based on the total weight of the coating composition. Free-radical curing techniques can be employed as appropriate, including methods well known in the art (e.g., thermal curing and radiation curing, such as electron beam or ultraviolet light). Useful free-radical photoinitiators include those known to be useful in UV curing of acrylate polymers, such as those described in WO 2006 / 102383.

[0031] The coating composition may contain a (meth)acrylate monomer other than the polymerizable monomer represented by Formula I as a crosslinking agent. For example, a crosslinkable silicone (meth)acrylate additive or a crosslinkable fluorinated (meth)acrylate additive may be added. The addition of a crosslinkable silicone additive or a crosslinkable fluorinated additive can reduce the surface energy of the hard coat. The concentration of the crosslinker can typically be 0.1 wt % or more and 2 wt % or less in the total coating composition.

[0032] As described in International Publication No. 2009 / 029438, which is incorporated herein by reference, certain silicone additives have also been found to provide ink repellency combined with low lint attraction. Such silicone (meth)acrylate additives generally comprise a polydimethylsiloxane (PDMS) backbone and at least one alkoxy side chain terminating in a (meth)acrylate group. The alkoxy side chain may optionally contain at least one hydroxyl substituent. Such silicone (meth)acrylate additives are commercially available from various sources, such as Tego Chemie, under the trade names TEGO Rad, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500, and TEGO Rad 2700. The chemical structures of TEGO Rad 2100 and TEGO Rad 2500, believed to be based on NMR analysis, are described in International Publication No. 2015 / 108834. The concentration of the crosslinkable silicone (meth)acrylate additive can typically be 0.1% or more and 2% or less by weight of the total coating composition.

[0033] An exemplary crosslinkable fluorinated (meth)acrylate additive is available from Shin-Etsu Chemical Co., Ltd. as the KY-1200 series (such as under the trade name "KY1203"). The KY-1200 series also functions as an antifouling agent. The concentration of the crosslinkable fluorinated (meth)acrylate additive can typically be 0.1 wt % or more and 2 wt % or less in the total coating composition.

[0034] The coating composition may further comprise at least 0.005, preferably at least 0.01 wt. % of one or more perfluoropolyether urethane additives, such as those described in U.S. Patent No. 7,178,264. The total amount of perfluoropolyether urethane additives, alone or in combination with other fluorinated additives, may typically be up to 0.5 or 1 wt. %.

[0035] The perfluoropolyether urethane material is preferably prepared from an isocyanate-reactive HFPO- material. Unless otherwise specified, "HFPO-" refers to the methyl ester F(CF(CF)CFO). a CF(CF3)C(O)OCH3 (where "a" is an average of 2 to 15) terminal group F(CF(CF3)CF2O) a "a" refers to CF(CF3)-. In some embodiments, a averages 3 to 10, or 5 to 8. Such species generally exist as a dispersion or mixture of oligomers having a range of values ​​for a, such that the average value of a may be a non-integer. For example, in one embodiment, "a" averages 6.2. The molecular weight of HFPO-perfluoropolyether materials varies from about 940 g / mol to about 1600 g / mol, depending on the number of repeating units ("a"), with a range of about 1100 g / mol to about 1400 g / mol typically being preferred.

[0036] Exemplary light stabilizers include hindered amine light stabilizers (HALS). Note that, in this disclosure, HALS as an additive is defined as being different from the secondary amine source of the polymerizable monomer described above. For example, FANCRYL FA-712HM may also be used as a photopolymerizable HALS, but in this disclosure, HALS as an additive is defined as being different from the secondary amine source of the polymerizable monomer described above. HALS are effective stabilizers against light-induced degradation of most polymers. HALS generally do not absorb UV light but act to inhibit polymer degradation. HALS typically include tetraalkylpiperidines such as 2,2,6,6-tetramethyl-4-piperidinamine and 2,2,6,6-tetramethyl-4-piperidinol. Other suitable HALS include compounds available from Ciba as TINUVIN 123, 144, and 292. The concentration of the light stabilizer can typically be 0.1% by weight or more and 5% by weight or less of the total coating composition.

[0037] The coating composition can be prepared by dissolving the polymerizable monomer represented by Formula I, optionally together with various additives, in a compatible organic solvent, and a single organic solvent or a blend of solvents can be used. When preparing the coating composition, the polymerizable monomer may be provided in the form of a solution containing a solvent. The solvent is appropriately selected depending on the polymerizable monomer used. Suitable solvents include alcohols (such as isopropyl alcohol (IPA), 2-methoxypropanol, or ethanol), ketones (such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), and the like), cyclohexanone or acetone, aromatic hydrocarbons (such as toluene), isophorone, butyrolactone, N-methylpyrrolidone, tetrahydrofuran, esters (such as lactates, acetates such as butyl acetate, for example, propylene glycol monomethyl ether acetate, such as that available from 3M under the trade name "3M Scotchcal Thinner CGS10" ("CGS10")), and propylene glycol monomethyl ether acetate, such as that available from 3M under the trade name "3M Scotchcal Thinner CGS10" ("CGS10"). Examples of suitable coating compositions include 2-butoxyethyl acetate, such as that commercially available as "CGS50" ("CGS50"), diethylene glycol ethyl ether acetate (DE acetate), ethylene glycol butyl ether acetate (EB acetate), dipropylene glycol monomethyl ether acetate (DPMA), iso-alkyl esters (e.g., isohexyl acetate, isoheptyl acetate, isooctyl acetate, isononyl acetate, isodecyl acetate, isododecyl acetate, isotridecyl acetate, or other iso-alkyl esters), and combinations thereof. The coating composition may be provided as a solution, or may be provided as a solvent-free solid by removing the solvent. The solid content of the coating composition may be 10 to 100% by weight.

[0038] The coating composition can be applied to the substrate using conventional film application techniques. Various techniques can be used to form thin films, including dip coating, forward and reverse roll coating, wire-wound rod coating, and die coating. Die coaters include, for example, knife coaters, slot coaters, slide coaters, fluid bearing coaters, slide curtain coaters, drop die curtain coaters, and extrusion coaters. Many types of die coaters are described in the literature. Typically, the substrate is conveniently in the form of a roll of continuous web, although the coating composition can also be applied to individual sheets.

[0039] The coating composition applied to a substrate may be dried in an oven to remove the solvent and then cured, for example, by heat treatment at a predetermined temperature. Alternatively, the coating composition applied to a substrate may be dried in an oven to remove the solvent and then cured, for example, by exposure to ultraviolet light using an H bulb or other lamp of the desired wavelength, preferably in an inert atmosphere (oxygen less than 50 ppm). This reaction mechanism crosslinks the polymerizable monomer represented by Formula I to form a crosslinked polymer containing monomer units derived from the polymerizable monomer, and a hard coating containing the crosslinked polymer is formed.

[0040] Hard coating, head area 2.7 x 2.7 cm 2 The change in haze Δhaze between before and after 10 cycles of a steel wool abrasion test using #0000 steel wool under the conditions of a load of 350 grams, a speed of 60 cycles / minute, and a stroke length of 85 mm is preferably 20.00 or less. Furthermore, Δhaze is more preferably 10.00 or less, even more preferably 7.00 or less, and particularly preferably 5.00 or less.

[0041] The hard coating preferably can be stretched without breaking or peeling when stretched at a temperature of 80 to 160°C, preferably 120°C, and more preferably can be stretched to 300% or more of the original length of the hard coating. Hard coatings with good thermal extensibility are suitable for vacuum thermoforming. Various known methods can be used for vacuum thermoforming. Preferably, the hard coating can be applied to objects such as vehicle parts using the three-dimensional overlay method (TOM) to create a decorative coating. Vacuum thermoforming can also be used to emboss the hard coating or create a relief. The hard coating can retain its shape after cooling.

[0042] The hard coating preferably also has good chemical resistance. Specifically, it is preferably insoluble in solvents such as IPA. It is also preferable that the hard coating maintains good resistance to acids and bases. Furthermore, it is preferable that the hard coating maintains good scratch resistance even after thermal vacuum forming. Scratch resistance after thermal vacuum forming can be evaluated using a nano-scratch test according to the following procedure. First, the gloss of a hard-coated test piece is measured before the test. Next, a thin layer of a mixture of JIS Z8901 Class 3 dust and water in a weight ratio of 1:3 is applied to the test piece and allowed to dry for one day. The test piece is then scrubbed with a 500 mm diameter car wash brush from an automatic car wash at 100 rpm for one minute, rinsed with water, and wiped dry. The gloss is then measured and the gloss retention is calculated. It is preferable that the gloss retention at 20° before and after the nano-scratch test be 90% or higher.

[0043] The hard coating of the present embodiment has a HUB derived from an isocyanate having a chain structure and a secondary amine having an alicyclic structure, thereby achieving both good thermal elongation and scratch resistance, which was previously difficult to achieve. Furthermore, good scratch resistance can be maintained even after thermoforming. For example, articles such as vehicle parts equipped with the hard coating of the present embodiment can be obtained by thermovacuum forming the hard coating. [Example]

[0044] The objects and advantages of the present disclosure are further illustrated in the following examples. The specific materials and amounts, as well as other conditions and details, recited in these examples should be used in a manner that does not unduly limit the present disclosure. Table 1 lists the names and descriptions of the raw materials used in the examples.

[0045] [Table 1]

[0046] [Synthesis of HUB monomer] The HUB monomers for each ID were synthesized using the isocyanates and amine (meth)acrylates listed in Table 2 below. Specifically, the isocyanates and solvents were first mixed in a glass container. The amino (meth)acrylates were then added. The reaction was monitored by IR measurement (using a Thermo Scientific NICOLET iS10) until equilibrium was reached. The HUB monomer solutions were prepared as stoichiometric mixtures of the isocyanates and amine (meth)acrylates. The reaction is essentially an equilibrium reaction. Typically, 30.0 g of Desmodur N3800, 17.70 g of FANCRYL FA-712HM, and 20.4 g of BuAc were used to prepare the HUB monomer solution for ID:2.

[0047] [Table 2]

[0048] 1 to 3 show the IR spectra of the isocyanates used in IDs 2, 4, and 14 and the HUB monomers synthesized in IDs 2, 4, and 14, respectively. The starting material for the HUB monomers exhibited a peak (2270 cm) derived from the isocyanate group. -1 In the synthesized HUB monomer, the peak due to the isocyanate group was very small, and the peak due to the urea bond (around 1650 cm -1near the center of the urea bond.

[0049] [Preparation of Coating Composition] Coating compositions C1 to C18 were prepared by adding Irgacure 184, TEGO Rad 2250, KY1203, and Tinuvin 123 to a BuAc solution of HUB monomer in the amounts shown in Table 3. Note that "parts" in Table 3 refer to "parts by weight," and are values ​​calculated assuming the total weight of the coating composition is 100. MP-OH was added as a solvent to adjust the solids content to 30% by weight. The mixture was mixed in a speed mixer in an amber vial to obtain a homogenized solution. The homogenized solution was filtered through a 1 μm glass fiber filter before the coating process described below.

[0050] [Table 3]

[0051] [Application and UV curing] The prepared coating compositions C1 to C18 were applied to S014G (Sumika Acrylic Sales Co., Ltd., PMMA) using a bar coater (Meyer rod #30) and dried in an oven at 60°C for 2 minutes. The dried surface layer was then cured using an H bulb under a nitrogen atmosphere to produce hard coatings H1 to H18 corresponding to each composition.

[0052] [Analysis and Characterization of Hard Coatings] (Scratch resistance test) The prepared hard coatings H1 to H18 were subjected to a scratch resistance test. 2The hard coating was evaluated for surface changes after 10 cycles of a steel wool abrasion test using #0000 steel wool under conditions of a load of 350 grams, a speed of 60 cycles / minute, and a stroke length of 85 mm. An abrasion tester (Imoto Manufacturing Co., Ltd., product name "IMC-157C") was used for the test. After the steel wool abrasion test was completed, the haze of the hard coating was measured using a haze meter (BYK-Gardner, product name "Haze-Gard Plus"), and the change in haze (Δhaze) before and after the abrasion test was evaluated. The evaluation results are shown in Table 4. A hard coating with a Δhaze of 20.00 or less has good scratch resistance.

[0053] (Thermal elongation test) The prepared hard coatings H1 to H18 were subjected to a hot ductility test. A heat gun (Ishizaki Electric Manufacturing Co., Ltd., product name "Plajet PJ-206A1") was used to apply hot air to the hard coating from a position 5 to 10 cm away, heating it to 100°C. The hard coating was then stretched while still being exposed to hot air from the heat gun. Hard coatings that were elongated to 300% or more of their original length without fracture or peeling were rated A; those that were elongated but fracture or peeling occurred at elongations of less than 300% were rated B; and those that showed almost no elongation were rated C. The evaluation results are shown in Table 4.

[0054] (Chemical resistance test) The prepared hard coatings H1 to H18 were subjected to chemical resistance tests. Chemical resistance was evaluated by applying ink to the hard coating with an oil-based marker and wiping the ink off with cotton soaked in IPA. A rating of O was given to samples where wiping with IPA significantly reduced or eliminated the ink on the hard coating surface and the hard coating surface did not dissolve or become cloudy. A rating of X was given to samples where wiping with IPA dissolved the hard coating surface and caused it to become cloudy. The evaluation results are shown in Table 4.

[0055] [Table 4]

[0056] Hard coatings H4, H6 to H9, H13 to 16, and H18 formed from coating compositions C4, C6 to C9, C13 to C16, and C18 were confirmed to have good scratch resistance and good thermal elongation. In particular, hard coating H7 had a Δhaze of 0.77, confirming particularly good scratch resistance.

[0057] [Three-dimensional surface decoration molding (Three-dimensional Overlay Method: TOM) test] Three-dimensional surface decoration molding (TOM) testing was performed on hard coating (HUB film) H7 prepared using coating composition C7. Testing was performed using equipment manufactured by Fuse Vacuum Co., Ltd. The TOM test was performed on two test samples, H7-A, on the same day the composition was cured, and H7-B, one week after the composition was cured. The TOM test was performed at two different temperatures (H7-A: 155°C, 142°C; H7-B: 142°C, 120°C). Both samples were thermoformable without cracking, demonstrating their potential as a TOM material.

[0058] (Evaluation of HUB connection after TOM test) The successfully thermoformed HUB film was attached to an ATR sampler and the HUB bond was evaluated using an ATR-IR measurement device (Thermo SCIENTIFIC, NICOLET iS10). In the HUB film after the TOM test, a peak due to dissociated NCO was observed at 2270 cm -1 The residual NCO content after the TOM test was clearly observed. The residual NCO content after the TOM test depended on the TOM test temperature (155, 142, or 120°C). The decay of the NCO-derived peak was also monitored over a 3-week period. The results are shown in Figure 4. In both H7-A and H7-B, the NCO content decreased during the first week. This indicates that the isocyanate of the HUB, which had been thermally cleaved, recrosslinked with the amine derived from the amino methacrylate (FANCRYL FA-712HM).

[0059] (Scratch resistance test after TOM test) Nano-scratch tests were performed on H7-A (142°C) and H7-B (120°C) HUB films one week after the TOM test. First, the gloss of the hard-coated test specimens was measured before the test. Then, a thin layer of a 1:3 mixture of JIS Z8901 Class 3 dust and water by weight was applied to the test specimens and allowed to dry for one day. The specimens were then scrubbed with a 500mm diameter car wash brush at 100 rpm for one minute, rinsed with water, and wiped dry. The gloss was then measured and the gloss retention was calculated. For both samples, the gloss retention at 20° before and after the nano-scratch test was over 92%, confirming excellent scratch resistance.

[0060] (Chemical resistance test after TOM test) The chemical resistance of HUB film H7-A (142°C) and H7-B (120°C) was evaluated one week after the TOM test. Chemical resistance was evaluated using a chemical spot test. At room temperature, a 1% by weight aqueous solution of hydrochloric acid or a 1% by weight aqueous solution of sodium hydroxide was dropped onto the HUB film sample, which was then exposed to an oven at 85°C for 30 minutes. The sample was then lightly rinsed with water at room temperature and visually evaluated for color change, cloudiness, and tearing. Both samples showed good resistance to hydrochloric acid and sodium hydroxide solutions.

[0061] [Testing coatings with different molar ratios of isocyanate and amine] Coating compositions C7-1, C7-2, and C7-3 were prepared using the same procedure as for hard coating H7, except that the molar ratio (NCO / NH2) of isocyanate and amine (meth)acrylate was changed when preparing the HUB monomer. These compositions were used to form hard coatings H7-1, H7-2, and H7-3, as shown in Table 5. Note that hard coating H7-1 is a reproduction of hard coating H7. Scratch resistance tests, thermal elongation tests, and chemical resistance tests were then performed on hard coatings H7-1, H7-2, and H7-3 according to the methods described above. The results are shown in Table 5.

[0062] [Table 5]

Claims

1. A coating composition comprising a polymerizable monomer of formula I. 【Chemistry 1】 [In formula I, R １ is an isocyanurate ring, R １ n substituents X are bonded to n is 3; X is a group of formula II, 【Chemistry 2】 In formula II, * denotes R in formula I １ represents the point of attachment to R ２ is selected from linear alkylene and substituted linear alkylene; A represents a 5- to 7-membered alicyclic structure having a nitrogen atom; In the alicyclic structure, Each carbon atom adjacent to the nitrogen atom may have one or two alkyl groups; The carbon atoms adjacent to the nitrogen atom may be bonded to each other via an alkylene group to form a ring structure. R ３ is a group having at least one polymerizable unsaturated bond.

2. R ２ 2. The coating composition according to claim 1, wherein is a chain alkylene having 4 to 12 carbon atoms.

3. 3. The coating composition according to claim 1, wherein X is a group represented by formula III. 【Transformation 3】 [In formula III, * denotes R in formula I １ represents the point of attachment to R ２ is selected from linear alkylene and substituted linear alkylene; R ３ is a group having at least one polymerizable unsaturated bond, Each R ４ is H or methyl, Each R ５ are H, methyl, or groups which combine with each other to form an alkylene having 2 carbon atoms.

4. The coating composition according to any one of claims 1 to 3, wherein X is a group represented by formula IV: 【Chemistry 4】 [In formula IV, * denotes R in formula I １ represents the point of attachment to R ２ is selected from linear alkylene and substituted linear alkylene; R ６ is H or methyl.

5. A crosslinked polymer comprising a monomer unit derived from the polymerizable monomer according to any one of claims 1 to 4.

6. A hard coating comprising the crosslinked polymer of claim 5.

7. An article comprising the hard coating of claim 6.

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