KR20240049082A - An amine derivative-based isocyanate blocking agent, an amine derivative-based block isocyanate, a double-curable composition comprising an amine derivative-based block isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and the method coated clear coat layer - Google Patents

Abstract

The present invention relates to an amine derivative-based isocyanate blocking agent, an amine derivative-based blocked isocyanate, a dual-cure composition containing an amine derivative-based blocked isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and a clear coating coated by the method. Start the coat layer.

Description

An amine derivative-based isocyanate blocking agent, an amine derivative-based blocked isocyanate, a dual-cure composition containing an amine derivative-based blocked isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and a clear coat layer coated by the method { An amine derivative-based isocyanate blocking agent, an amine derivative-based block isocyanate, a double-curable composition comprising an amine derivative-based block isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and the method coated clear coat layer}

The present invention relates to an amine derivative-based isocyanate blocking agent, an amine derivative-based blocked isocyanate, a dual-cure composition containing an amine derivative-based blocked isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and a clear coating coated by the method. It's about the coat layer.

Blocked isocyanate is a blocking agent with active hydrogen and urea to prevent the isocyanate group (-NCO) from reacting with moisture or other reactive groups such as hydroxyl group (-OH) and amine group (-NH ₂ ) at room temperature. It is a curing agent (crosslinker) that improves storage stability through (urea) bonding.

In general, blocked isocyanates are deblocked at high temperatures and a crosslinking reaction (or hardening reaction) occurs through a urethane reaction between the isocyanate group and the hydroxyl group of the binder.

Block isocyanate curing agents can provide high mechanical and chemical properties by forming a cross-linking network through a high-temperature curing reaction process, and in particular, can provide excellent storage stability. Accordingly, block isocyanate curing agents can be applied to one-component coating compositions and are applied to various industrial fields such as paints and coatings, films, and surface protection.

Automotive coatings are being developed to enhance various functions and are composed of multiple layers including electrocoat, primer, basecoat and clearcoat.

Each coating layer has its own role, and in particular, the clear coat layer, which is transparent and coated on the outermost surface, protects not only the car body but also the internal coating layer from external damage. Therefore, the clearcoat layer must be densely crosslinked to ensure sufficient resistance to chemical stress and physical damage.

The high-temperature curing process applied to existing clear coat coating systems for automobiles is carried out at a high temperature of over 150°C to form a dense cross-linking network, and these clear coat coating systems for automobiles contain a large amount of volatile organic compounds (VOCs). It emits harmful substances such as , and at the same time, it emits excessive amounts of carbon dioxide, a representative greenhouse gas, due to enormous energy consumption, causing various environmental problems and warming issues. There is a need to develop countermeasure technologies for this.

Therefore, the development of low-temperature curing coating material technology to replace this high-temperature curing process is very important, and many various studies have been conducted.

Basically, research is mainly conducted in the technical direction of lowering the dissociation temperature of block isocyanate, which is applied to low-temperature curing coating material technology.

Blocking agents used in blocked isocyanate for low-temperature curing processes include pyrazole, imidazole, amine, and oxime. However, in the case of coating films cured in this low-temperature curing process, the dissociated blocking agent simply volatilizes without participating in a separate reaction to a level that provides lower mechanical and chemical properties compared to the existing high-temperature curing process, forming volatile organic compounds (VOC). As it is released into the atmosphere, it is causing environmental problems.

Republic of Korea Patent Publication 10-2022-0094864

In order to solve the problems of the prior art described above, the present invention includes not only a urethane crosslinking reaction between hydroxyl groups and isocyanate groups, but also a radical crosslinking reaction of a double bond methacrylate functional group to create a more dense crosslinking network even at low temperatures compared to the single curing type. An amine derivative-based isocyanate blocking agent capable of forming an amine derivative-based blocked isocyanate, a dual-cure composition containing an amine derivative-based blocked isocyanate, a one-component clear coat composition for automobiles, a coating method using the same, and coating by the method. I would like to propose a clear coat layer.

In order to achieve the above-mentioned object, according to one embodiment of the present invention, an isocyanate blocking agent based on an amine derivative capable of radical crosslinking reaction, which has the chemical structure of the following formula (1), is provided.

<Formula 1>

In Formula 1, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

According to one embodiment of the present invention, a block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction is provided, which is prepared through a urea bond formation reaction between a compound of the following formula (2) and a polyisocyanate compound.

<Formula 2>

In Formula 2, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

The polyisocyanate compound is an aliphatic, aromatic, alicyclic, or araliphatic compound and may contain two or more isocyanate groups in its molecular structure.

The polyisocyanate compound may be in the form of a multimer including a dimer and a trimer.

The polyisocyanate compound may be hexamethylene diisocyanate trimer.

The polyisocyanate compounds include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, dodecamethylene diisocyanate, and 2,2-dimethylpentane diisocyanate. Isocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, 1, 6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanate methyl caproate, bis(2-isocyanate ethyl)fumarate, bis(2-isocyanate) Ethyl) carbonate, 2-isocyanate ethyl-2,6-diisocyanate hexanoate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanato-4-isocyanatomethyl octane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane, bis(isocyanatoethyl) carbonate, bis(isocyanatoethyl) ether, 1,4-butylene glycol di. Propyl ether-ω,ω'-diisocyanate, lysine diisocyanato methyl ester, lysine triisocyanate, 2-isocyanatoethyl-2,6-diisocyanato ethyl-2,6-diisocyanato hexanoate, 2 -Isocyanato propyl-2,6-diisocyanato hexanoate, 2,6-di(isocyanatomethyl) furan, 1,3,-bis(6-isocyanato hexyl)-uretidine- It may be one or more aliphatic isocyanates selected from the group consisting of 2,4-dione, 1,3,5-tris(6-isocyanato hexyl)isocyanurate.

The polyisocyanate compounds include thiodiethyl diisocyanate, thiopropyl diisocyanate, thiodihexyl diisocyanate, dimethylsulfone diisocyanate, dithio dimethyl diisocyanate, dithio diethyl diisocyanate, dithio propyl diisocyanate, and dicyclohexyl sulfide. It may be one or more sulfur-containing aliphatic isocyanates selected from the group consisting of -4,4'-diisocyanate.

The polyisocyanate compound includes diphenyl sulfide-2,4'-diisocyanate, diphenyl sulfide-4,4'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanato dibenzyl thioether, Aromatic sulfide isocyanates such as bis(4-isocyanatomethyl benzene) sulfide, 4,4'-methoxy benzene thioethylene glycol-3,3'-diisocyanate, diphenyl disulfide-4,4'-diisocyanate, 2,2'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-6,6' -Diisocyanate, 4,4'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethoxy diphenyl disulfide-4,4'-diisocyanate, 4,4'-dimethoxy diphenyl It may be one or more aromatic disulfide-based isocyanates selected from the group consisting of disulfide-3,3'-diisocyanate.

The polyisocyanate compounds include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, and 4,4'-diisocyanate. Phenylenemethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate, ethyl phenylene diisocyanate, 4,4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4'-diisocyanate biphenyl , 3,3'-dimethyl-4,4'-diisocyanate, diphenylmethane, naphthalene diisocyanate, methyl naphthalene diisocyanate, trizine diisocyanate, bis (isocyanatophenyl) ethylene, 3,3'-dimethoxy ratio. Phenyl-4-4'-diisocyanate, isopropylenephenylene diisocyanate, dimethylphenylene diisocyanate, diethylphenylene diisocyanate, diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate, benzene triisocyanate, triisocyanate Phenylmethane triisocyanate, naphthalene triisocyanate, diphenylmethane-2,4,4'-triisocyanate, 3-methyl diphenylmethane-4,6,4'-triisocyanate, 4-methyl-diphenylmethane-3, 5,2',4',6'-pentisocyanate, xylylene diisocyanate, bis(isocyanatoethyl)benzene, bis(isocyanato propyl)benzene, α,α, α',α'-tetramethyl 1 selected from the group consisting of xylylene diisocyanate, bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene, bis(isocyanatomethyl)diphenyl ether, and bis(isocyanatoethyl)phthalate It may be more than one type of aromatic isocyanate.

The polyisocyanate compounds include diphenyl sulfone-4,4'-diisocyanate, diphenyl sulfone-3,3'-diisocyanate, diphenylmethane sulfone-4,4'-diisocyanate, and 4-methyl diphenylmethane sulfone- 2,4'-diisocyanate, 4,4'-dimethoxy diphenyl sulfone-3,3'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanate dibenzyl sulfone, 4,4' -Dimethyldiphenylsulfone-3,3'-diisocyanate, 4,4'-di-tert-butyl diphenyl sulfone-3,3'-diisocyanate, 4,4'-methoxy benzene ethylene disulfone-3, It may be one or more aromatic sulfone isocyanates selected from the group consisting of 3'-diisocyanate and 4,4'-dichlorophenylsulfone-3,3'-diisocyanate.

The polyisocyanate compounds include isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, and bis(2-isocyanate ethyl)-4. -Cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, 2,2-dimethyl dicyclohexylmethane diisocyanate, 2-isocyanato Methyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)- 6-Isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2,2 ,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo [2,2,1]-heptane, 2-isocyanatomethyl- 3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl )-6-(2-isocyanatoethyl)-bicyclo [2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanate natoethyl)-bicyclo[2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2, It may be one or more alicyclic isocyanates selected from the group consisting of 2,1]-heptane and norbornane bis(isocyanatomethyl).

The polyisocyanate compound is 1,3-bis (isocyanatomethyl) benzene (m-xylene diisocyanate, m-XDI), 1,4-bis (isocyanatomethyl) benzene (p-xylene diisocyanate, p- XDI), 1,3-bis (2-isocyanato propan-2-yl) benzene (m-tetramethyl xylene diisocyanate, m-TMXDI), 1,4-bis (2-isocyanato propan-2- 1) Benzene (p-tetramethyl xylene diisocyanate, p-TMXDI), 1,3-bis(isocyanatomethyl)-4-methylbenzene, 1,3-bis(isocyanatomethyl)-4-ethylbenzene , 1,3-bis(isocyanatomethyl)-5-methylbenzene, 1,3-bis(isocyanatomethyl)-4,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2 ,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetramethylbenzene, 1,3-bis(isocyanatomethyl)-5-tert-butyl benzene, 1 ,3-bis(isocyanatomethyl)-4-chlorobenzene, 1,3-bis(isocyanatomethyl)-4,5-dichlorobenzene, 1,3-bis(isocyanatomethyl)-2,4 ,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl)-2,3,5 , It may be one or more aromatic aliphatic isocyanates selected from the group consisting of 6-tetrabromo benzene, 1,4-bis (2-isocyanatoethyl) benzene, and 1,4-bis (isocyanatomethyl) naphthalene. .

The block isocyanate may have the chemical structure of Formula 3 below.

<Formula 3>

In Formula 3, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

According to one embodiment of the present invention, the above-mentioned block isocyanate; At least one polyol selected from acrylic polyols, polyester polyols, polyurethane polyols, acrylic carbamate polyols, and polyester carbamate polyols in which a double bond oligomer group is bonded to some hydroxyl groups; and a thermal radical initiator.

The polyol may be an acrylic polyol as represented by Chemical Formula 4 below.

<Formula 4>

Said R is an alkyl group.

The thermal radical initiator has a typical 1h half-life temperature in the range of 90 to 100°C, and includes tert-Butyl peroxy-isobutyrate, tert-Butyl peroxydiethylacetate, tert-Butyl peroxy-2-ethylhexanoate, Dibenzoyl peroxide, and tert-Amyl peroxy. It may be any one of -2-ethylhexanoate or a combination thereof.

The dual-cure composition may have a crosslinking reaction temperature of 100 to 130°C.

According to one embodiment of the present invention, the above-mentioned block isocyanate; 30 to 45% by weight of at least one polyol selected from acrylic polyols, polyester polyols, polyurethane polyols, acrylic carbamate polyols, and polyester carbamate polyols in which a double bond oligomer group is bonded to some hydroxyl groups; and 25 to 40% by weight of a mixture containing a reactive diluent, an ultraviolet absorber or stabilizer, a leveling agent, and a solvent. A dual-cure one-component clear coat composition for automobiles is provided.

The polyol may have a double bond oligomer content of 20 to 60% by weight based on solid content and a hydroxyl value in the range of 100 to 200 mg KOH per gram of polyol.

The crosslinking reaction temperature of the dual-cure one-component clear coat composition for automobiles may be 100 to 130°C.

According to one embodiment of the present invention, applying the above-described dual-cure one-component clear coat composition for automobiles on a substrate and performing a first thermal curing process in a preset temperature range; performing a first photocuring process by irradiating light having a preset amount of light to the substrate immediately after the first thermal curing process is completed; and performing a second thermal curing process in the same temperature range as the first thermal curing process after the first photo curing process is completed.

The coating method may further include performing an additional thermal curing process at the same temperature range as the first thermal curing process between the first thermal curing process and the first photo curing process.

The light used for photocuring may include at least one of UV, EB, and LED.

The coating method may further include performing a second photocuring process by irradiating light having a preset amount of light to the substrate immediately after the second thermal curing process is completed.

According to one embodiment of the present invention, a clear coat coating layer manufactured through the above method is provided.

The present invention has the advantage of enabling a low-temperature curing process using a blocking agent based on an amine derivative that dissociates at low temperatures.

In addition, according to the present invention, a dual-cure system was constructed by introducing a methacrylate-functionalized blocking agent, which not only forms a more dense cross-linking network even at low temperatures, but also removes the blocking agent that was previously released into the atmosphere during the heat curing process. It has the advantage of being able to dramatically control volatile organic compounds (VOC) by directly participating in the crosslinking reaction.

Through this, the reactivity of the crosslinking reaction can be increased by including the blocking agent as a monomer in the reaction, and the mechanical/chemical properties can be improved by controlling the structure and crosslinking density of the crosslinking network.

In addition, in addition to this thermal dual curing process, more improved crosslinking properties can be provided through the introduction of a thermal-light multiple curing mechanism.

Figure 1 is a diagram showing the dual curing process of methyl acrylate functionalized block isocyanate according to this embodiment.
Figure 2 is a diagram showing the dissociation characteristics of various block isocyanates.
Figure 3 is a diagram showing the real-time rheological behavior of the clear coat depending on the presence or absence of TRI under various thermal curing conditions.
Figure 4 is a diagram showing the real-time crosslinking behavior of a thin transparent coating film depending on the presence or absence of TRI using a rigid pendulum tester under various thermal curing conditions.
Figure 5 is a diagram showing VOCs generated by a clear coat under thermal curing conditions of (a) 120°C and (b) 150°C through TGA analysis.
Figure 6 is a diagram showing the logarithmic damping ratio of the clear coat thin film cured at (a) 120 °C, (b) 130 °C, and (c) 150 °C measured using a rigid pendulum physical property tester in physical mode.
Figure 7 is a diagram showing the storage modulus of clearcoat films cured at (a) 120°C, (b) 130°C, and (c) 150°C through DMA analysis.
Figure 8 is a diagram showing the indentation curve and (d) surface strength (HIT) of clearcoat films cured at (a) 120 °C, (b) 130 °C, and (c) 150 °C.
Figure 9 is a diagram showing scratch patterns of clear coat films cured at (a) 120°C, (b) 130°C, and (c) 150°C.
Figure 10 is a diagram showing scratch panoramic images and critical load (Lc1) of clearcoat films cured under various thermal curing conditions.
Figure 11 is a diagram showing changes in mechanical properties according to various heat and photocuring process conditions.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

This example proposes a new amine derivative-based isocyanate blocking agent capable of urethane and radical crosslinking reactions to effectively reduce VOC emissions and improve crosslinking density.

The blocking agent according to this embodiment preferably has a methacrylate functionalized moiety.

Furthermore, we propose a blocked isocyanate based on a dual-curable amine derivative that is manufactured through a urea coupling reaction between the above-described blocking agent and a polyisocyanate compound and is capable of urethane and radical crosslinking reactions.

In addition, this embodiment is a dual-curable composition comprising at least one polyol selected from the block isocyanate, acrylic polyol, polyester polyol, polyurethane polyol, acrylic carbamate polyol, and polyester carbamate polyol and a thermal radical initiator. suggests.

The dual-cure composition according to this embodiment can be used as a one-component clear coat composition for automobiles, and as a low-temperature cure type, the crosslinking reaction temperature may range from 100 to 130°C.

In addition, the dual-curable composition according to this embodiment can form a clear coat layer for automobiles through not only a thermal curing process, but also a thermal curing process and a photo-curing process sequentially.

Hereinafter, a dual-curable composition containing an amine derivative-based isocyanate blocking agent, an amine derivative-based block isocyanate, and an amine derivative-based block isocyanate according to this embodiment, and a coating method using the same will be described in detail.

In this embodiment, an isocyanate blocking agent based on an amine derivative capable of radical crosslinking reaction is provided, which has the chemical structure of the following formula (1).

<Formula 1>

In Formula 1, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

In addition, this embodiment provides a block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, which is prepared through a urea bond formation reaction between the compound of Formula 2 and a polyisocyanate compound.

<Formula 2>

In Formula 2, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

According to this embodiment, the polyisocyanate compound may be an aliphatic, aromatic, alicyclic, or araliphatic compound containing two or more isocyanate groups in the molecular structure, and in this case, the polyisocyanate compound is a dimer. , it may have a multimer form such as a trimer, and a representative trimer form includes hexamethylene diisocyanate trimer.

According to this embodiment, the polyisocyanate compound is ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, dodecamethylene diisocyanate, 2 ,2-dimethylpentane diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethyl hexamethylene Methylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanate methyl caproate, bis(2-isocyanate ethyl) fumarate , bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-diisocyanate hexanoate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanato-4- Isocyanatomethyl octane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane, bis(isocyanatoethyl) carbonate, bis(isocyanatoethyl) ether, 1, 4-Butylene glycol dipropyl ether-ω,ω'-diisocyanate, lysine diisocyanato methyl ester, lysine triisocyanate, 2-isocyanatoethyl-2,6-diisocyanato ethyl-2,6-diisocyanate Natto hexanoate, 2-isocyanato propyl-2,6-diisocyanato hexanoate, 2,6-di(isocyanatomethyl) furan, 1,3,-bis(6-isocyanato hexyl )-Uretidine-2,4-dione, 1,3,5-tris(6-isocyanato hexyl)isocyanurate may be at least one type of aliphatic isocyanate selected from the group consisting of.

Alternatively, the polyisocyanate compound may be thiodiethyl diisocyanate, thiopropyl diisocyanate, thiodihexyl diisocyanate, dimethylsulfone diisocyanate, dithio dimethyl diisocyanate, dithio diethyl diisocyanate, dithio propyl diisocyanate, dicyclo It may be one or more sulfur-containing aliphatic isocyanates selected from the group consisting of hexyl sulfide-4,4'-diisocyanate.

Alternatively, the polyisocyanate compound may be diphenyl sulfide-2,4'-diisocyanate, diphenyl sulfide-4,4'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanato dibenzyl thio. Aromatic sulfide isocyanates such as ether, bis(4-isocyanatomethyl benzene) sulfide, 4,4'-methoxy benzene, thioethylene glycol-3,3'-diisocyanate, and diphenyl disulfide-4,4'-di. Isocyanate, 2,2'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-6, 6'-diisocyanate, 4,4'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethoxy diphenyl disulfide-4,4'-diisocyanate, 4,4'-dimethoxy It may be one or more aromatic disulfide isocyanates selected from the group consisting of diphenyl disulfide-3,3'-diisocyanate.

According to this embodiment, the polyisocyanate compound is 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, 4,4'-Diphenylenemethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate, ethyl phenylene diisocyanate, 4,4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4 '-diisocyanate biphenyl, 3,3'-dimethyl-4,4'-diisocyanate diphenylmethane, naphthalene diisocyanate, methyl naphthalene diisocyanate, trizine diisocyanate, bis(isocyanatophenyl) ethylene, 3, 3'-dimethoxybiphenyl-4-4'-diisocyanate, isopropylenephenylene diisocyanate, dimethylphenylene diisocyanate, diethylphenylene diisocyanate, diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate , Benzene triisocyanate, triphenylmethane triisocyanate, naphthalene triisocyanate, diphenylmethane-2,4,4'-triisocyanate, 3-methyl diphenylmethane-4,6,4'-triisocyanate, 4-methyl- Diphenylmethane-3,5,2',4',6'-pentisocyanate, xylylene diisocyanate, bis(isocyanatoethyl)benzene, bis(isocyanatopropyl)benzene, α,α, α' ,α'-tetramethyl xylylene diisocyanate, bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene, bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl)phthalate It may be one or more aromatic isocyanates selected from the group consisting of

Alternatively, the polyisocyanate compound may be diphenyl sulfone-4,4'-diisocyanate, diphenyl sulfone-3,3'-diisocyanate, diphenylmethane sulfone-4,4'-diisocyanate, or 4-methyl diphenylmethane. Sulfone-2,4'-diisocyanate, 4,4'-dimethoxy diphenyl sulfone-3,3'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanate dibenzyl sulfone, 4, 4'-Dimethyldiphenylsulfone-3,3'-diisocyanate, 4,4'-di-tert-butyl diphenyl sulfone-3,3'-diisocyanate, 4,4'-methoxy benzene ethylene disulfone- It may be one or more aromatic sulfone isocyanates selected from the group consisting of 3,3'-diisocyanate and 4,4'-dichlorophenylsulfone-3,3'-diisocyanate.

According to this embodiment, the polyisocyanate compound is isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2 -Isocyanate ethyl)-4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, 2,2-dimethyl dicyclohexylmethane diisocyanate , 2-isocyanatomethyl-3-(3-isocyanato propyl)-5-isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-(3- Isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl- Bicyclo[2,2,1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2,2,1]-heptane,2 -Isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-( 3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5 -(2-isocyanatoethyl)-bicyclo[2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl) -It may be one or more alicyclic isocyanates selected from the group consisting of bicyclo[2,2,1]-heptane and norbornane bis(isocyanatomethyl).

According to this embodiment, the polyisocyanate compound is 1,3-bis (isocyanatomethyl) benzene (m-xylene diisocyanate, m-XDI), 1,4-bis (isocyanatomethyl) benzene (p- Xylene diisocyanate, p- Cyanato propan-2-yl) benzene (p-tetramethyl xylene diisocyanate, p-TMXDI), 1,3-bis (isocyanatomethyl) -4-methylbenzene, 1,3-bis (isocyanatomethyl )-4-ethylbenzene, 1,3-bis(isocyanatomethyl)-5-methylbenzene, 1,3-bis(isocyanatomethyl)-4,5-dimethylbenzene, 1,4-bis(iso Cyanatomethyl)-2,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetramethylbenzene, 1,3-bis(isocyanatomethyl)-5- tert-butyl benzene, 1,3-bis(isocyanatomethyl)-4-chlorobenzene, 1,3-bis(isocyanatomethyl)-4,5-dichlorobenzene, 1,3-bis(isocyanato) Methyl)-2,4,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl) -One or more types selected from the group consisting of 2,3,5,6-tetrabromo benzene, 1,4-bis (2-isocyanatoethyl) benzene, and 1,4-bis (isocyanatomethyl) naphthalene It may be an aromatic aliphatic isocyanate.

According to this embodiment, the block isocyanate may be a dual-curable block isocyanate based on urethane and an amine derivative capable of radical crosslinking reaction, which has the chemical structure of the following formula (3).

<Formula 3>

In Formula 3, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms.

In addition, in this embodiment, a block isocyanate based on the urethane and a dual-curable amine derivative capable of radical crosslinking reaction; and at least one polyol selected from acrylic polyol, polyester polyol, polyurethane polyol, acrylic carbamate polyol, and polyester carbamate polyol, characterized in that a double bond oligomer group is bonded to some hydroxyl group; and a thermal radical initiator.

The polyol according to this example may be an acrylic polyol as shown in Chemical Formula 4 below.

<Formula 4>

In Formula 4, R is an alkyl group.

In the composition according to this embodiment, the thermal radical initiator may be any as long as the typical 1h half-life temperature is in the range of 90 to 100°C (tert-Butyl peroxy-isobutyrate, tert-Butyl peroxydiethylacetate, tert -Butyl peroxy-2-ethylhexanoate, Dibenzoyl peroxide, tert-Amyl peroxy-2-ethylhexanoate, etc. can be used), but tert-Amyl peroxy-2-ethylhexanoate is most preferred. do.

Additionally, in this embodiment, the low-temperature and dual-cure composition preferably has a crosslinking reaction temperature of 100 to 130°C.

Additionally, in this example, 30 to 45% by weight of the acrylic polyol of Formula 3; A dual-curable blocked isocyanate based on urethane and an amine derivative capable of radical crosslinking reaction, which is prepared through a urea bond formation reaction between the blocking agent of Formula 1 and a polyisocyanate compound; and 25 to 40% by weight of a mixture containing a reactive diluent, an ultraviolet absorber or stabilizer, a leveling agent, and a solvent.

In the dual-cure one-component clear coat composition for automobiles according to this embodiment, the polyisocyanate compound may be an aliphatic, aromatic, alicyclic, or araliphatic compound containing two or more isocyanate groups in the molecular structure, The acrylic polyol preferably has a double bond oligomer content of 20 to 60% by weight based on solid content and a hydroxyl value in the range of 100 to 200 mg KOH per gram of polyol.

The low-temperature and dual-cure one-component clear coat composition for automobiles according to this embodiment is characterized in that the crosslinking reaction temperature is 100 to 130°C.

In the dual-cure one-component clear coat composition for automobiles according to this embodiment, an additional photocuring process is introduced in the middle of the thermal curing process and immediately after the thermal curing process to heat-heat-light or heat-light-heat, heat. -It is characterized by the possibility of multiple curing processes such as light-heat-light.

Additionally, according to this embodiment, a clear coat layer manufactured through the above-described multiple curing process is provided.

Hereinafter, the manufacturing method of the blocking agent, blocked isocyanate, and dual-cure composition according to this embodiment and the performance evaluation process for the clear coat layer will be described in detail.

<Example 1 and Comparative Example> Synthesis of amine derivative-based block isocyanate

Hexamethylene diisocyanate trimer (HDI trimer, Desmodur®N3300, Covestro, Germany) was used as a free isocyanate crosslinker without a blocking agent.

Methacrylate-functionalized blocked isocyanate (BI _TBEMA ) was synthesized by blocking the isocyanate groups in the HDI trimer with 2-(tert-butylamino) ethyl methacrylate (TBEMA), which each has a methyl acrylate functional group.

Figure 1 is a diagram showing the dual curing process of methyl acrylate functionalized block isocyanate according to this example, and the chemical structure of BI _TBEMA is shown in Figure 1.

First, TBEMA was diluted with xylene (0.58 g of TBEMA, 1.05 g of xylene) at 40 °C in a nitrogen atmosphere to obtain a diluted blocking agent with a solid content of 60%.

Then, a specific amount of HDI was added to the diluted blocking agent, with the molar ratio of the active hydrogen of the NH group of the blocking agent and the NCO group in HDI being 1.1:1.

The mixture was then stirred for 6 hours to completely block the free isocyanate functional groups.

For comparison, an amine derivative-based blocked isocyanate (BI _NtBEA ) was synthesized by blocking the isocyanate group in the HDI trimer with n-tert-butylehtylamine (NtBEA), which does not have a methyl acrylate functional group.

NtBEA (Merck, Germany) is diluted with xylene (NtBEA 1.04 g, xylene 1.36 g) at 40 °C in a nitrogen atmosphere to obtain a diluted blocking agent with a solid content of 60%.

The mixture was then stirred for 6 hours to completely block the free isocyanate functional groups.

<Example 2 and Comparative Example> Preparation of dual-cure one-component clear coat composition for automobiles

To determine the applicability of BI _TBEMA for eco-friendly automotive coating systems, block isocyanate and hydroxyl functionalized urethane methacrylate oligomer (HFUMO) resin were mixed with double bonds (C=C) and 150 mg KOH/ Transparent clearcoat samples (C _TBEMA ) were prepared by mixing with a 60% acrylate backbone containing g of hydroxyl (OH).

The amounts of resin and blocked isocyanate were based on a molar ratio of 1:1.1 between the OH group of HFUMO resin and the NCO group of the cross-linking agent to ensure a complete cross-linking network.

Clearcoat samples (C _NtBEA and C _PL350 ) containing single-cure BI _NtBEA and commercial BI _PL350 (Desmodur®PL350, Covestro, Germany) crosslinkers were also prepared to compare crosslinking properties.

The radical crosslinking reaction was initiated using a thermal radical initiator (TRI) (t-armyl peroxy 2-ehtylhexanonate, Luperox 575, Arkema, France). A small amount of BYK 306 (BYK Chemie, Germany) was added to the clearcoat as a surface-leveling control agent.

The detailed formulations of the three clear coats are listed in Table 1.

C _PL350 was formulated without TRI to confirm whether BI _TBEMA according to this example shows better performance than the commercial crosslinker BI _PL350 .

As shown in Figure 1, after the blocking agent was dissociated during the heat curing process, the NCO group of the free isocyanate reacted with the OH group of the HFUMO resin. The TBEMA blocking agent with methacrylate functional group can directly participate in the C=C bond and radical cross-linking reaction of both HFUMO resin or itself after thermal radical initiation with TRI.

<Experimental Example 1> Blocking of blocking agent and bond dissociation energy (BDE) of blocked isocyanate

To confirm that the amine derivative-based isocyanate blocking agent is fully attached to the NCO group in HDI, the characteristic peak at 2280-2250 cm ^-1 of the free isocyanate group was analyzed by attenuated total reflectance FT-IR spectroscopy (ATR-FT). -IR, Agilent Technology, Santa Clara, USA).

The bond dissociation energy of the amine derivative-based isocyanate blocking agent was theoretically predicted through density functional theory (DFT) simulation to evaluate the dissociation efficiency.

DFT calculations were performed using Gaussian 09 software at the B3LYP/6-31G(d) level. First, geometric optimization of block isocyanate was performed to obtain an optimized structural configuration. Then, the BDE for dissociating the blocking agent from the blocked isocyanate was calculated by frequency calculation to predict the relative dissociation reactivity.

The reactivity and dissociation efficiency of various block isocyanates, BI _TBEMA and BI _NtBEA , and the commercial BI _PL350 crosslinker were predicted through DFT simulation.

The BDE required to dissociate the simplified blocked isocyanate structure and blocking agent through the optimized geometric configuration is shown in Table 2.

The BDE for BI _TBEMA and BI _NtBEA was significantly lower than that of BI _PL350 , indicating that the NH and NCO groups of the amine derivative-based isocyanate blocking agent effectively improve the dissociation efficiency. This result suggests that the amine derivative-based isocyanate blocking agent effectively improves the dissociation efficiency in low-temperature curing technology. This suggests potential applications of BI.

The BDE of BI _TBEMA was slightly higher than that of BI _NtBEA , because the methacrylate group of TBEMA, which is an electron donating group, strengthens the negative charge of the blocking agent, and the bonding strength between the NCO group and NH group is increased according to the enhanced charge difference. Because it increased.

To quantitatively analyze the dissociation properties of blocked isocyanates, we used ATR-FT-IR in the range of 3200-3600 cm ^-1 to monitor the change in OH group absorbance of the resin under various thermal conditions (110, 120, 130, and 150°C). did.

Figure 2 is a diagram showing the dissociation characteristics of various block isocyanates.

As shown in Figure 2, the dissociation characteristics of various block isocyanates were confirmed by FT-IR analysis of clear coats containing each block isocyanate before and after heat curing.

Referring to Figure 2, the change in OH stretching vibration of the clear coat was observed from 3200 to 3600 cm ^-1 at 110, 120, 130, and 150 °C. Since the wide absorbance peak of unreacted OH groups in HFUMO resin includes a sharp NH absorbance peak from 3300 to 3450 cm ^-1 , the change in absorbance of OH groups through urethane reaction is clearly in the range of 3450-3600 cm ^-1. could be observed.

In relation to the lower BDE values in DFT calculations, C _TBEMA and C _NtBEA showed a greater decrease in OH absorbance than C _PL350 at low curing temperatures of 110, 120 and 130 °C (Figure 2(a)-2(c) )).

By comparing the OH stretching before and after heat curing, the conversion rate of the urethane reaction was estimated using the following equation.

where A is the area of OH stretching absorbance and the subscripts 0 and f indicate the initial and final heat setting states, respectively.

Using the above equation, the conversion rate of the urethane reaction was estimated from the change in OH stretching absorbance area before and after heat curing (Figure 2(d)).

At 150°C, all clearcoat samples showed a high level of urethane reaction, providing sufficient thermal energy to promote the urethane reaction. At low temperatures of 120 and 130 °C, the conversion rates of C _TBEMA and C _NtBEA were much higher than those of C _PL350 , indicating better dissociation performance of the amine derivative-based blocked isocyanate.

In addition, the clear coat composition C _TBEMA containing methacrylate-functionalized block isocyanate among amine derivative-based block isocyanates shows better dissociation performance at low temperatures compared to the clear coat composition C _NtBEA without a methacrylate functional group.

<Experimental Example 2> Cross-linking characteristics of clear coat

As described above, the macroscopic double-cure behavior of clearcoats containing various blocked isocyanates was investigated using an MCR-302 rotational rheometer (Anton Paar, Graz, Austria) equipped with a temperature control chamber.

In particular, the effect of additional radical cross-linking reaction was investigated by comparing a single-cure process and a dual-cure process involving only the urethane reaction of the clear coat without TRI.

Storage modulus G' was measured in real time in small amplitude oscillatory shear (SAOS) mode with an angular frequency of 5 Hz and 1% strain.

Clearcoat samples were loaded between parallel plates with a diameter of 8 mm and a measuring gap of 500 μm. The temperature in the temperature control chamber was raised from 30°C to the target temperatures of 120, 130, and 150°C at a heating rate of 10°C and then maintained. A rigid-body pendulum tester (RPT, RPT-3000 W, AND, Japan) was used to further investigate the thermal curing behavior of the clearcoat film.

A clear coat with a wet thickness of 100 μm was applied on the steel plate using the bar coating method. The target thickness of the cured film was in the range of 30-40 μm, which is often adopted in the automotive coating industry due to solvent evaporation during thermal curing. The RBE-160 blade type attached to the FRB-300 pendulum body was placed on a wet clear coat film and shaken by external electromagnetic force. The pendulum oscillation period, which represents the curing behavior of the reactive clearcoat, was measured under the same thermal curing conditions as in the rheological measurements.

Figure 3 is a diagram showing the real-time rheological behavior of the clear coat depending on the presence or absence of TRI under various thermal curing conditions.

As shown in Figure 3, the influence of radical cross-linking of TRI on the macroscopic curing behavior of clearcoats containing amine derivative-based blocked isocyanates was investigated using a rotational rheometer.

Real-time storage modulus (G') was measured at three different curing temperatures (120, 130 and 150 °C). First, to evaluate the dissociation performance of amine derivative-based blocked isocyanates at low curing temperatures, a single curing process in which only the urethane reaction occurs was analyzed for a TRI-free clearcoat (see open symbols in Figure 3).

C _TBEMA and C _NtBEA showed some degree of G' evolution even at 120 and 130°C. This means that the amine derivative-based isocyanate blocking agent was effectively dissociated from the blocked isocyanate at a lower temperature (Figure 3 (a) and (b)).

Meanwhile, the crosslinking reaction of C _PL350 did not occur at 120°C and 130°C. C _TBEMA has a slightly faster onset time than C _NtBEA at 120°C and 130°C, which is consistent with the BDE results in Table 2.

Addition of TRI to clearcoats with amine derivative-based blocked isocyanates dramatically changed the evolution of G' at all temperatures (see closed symbols in Figure 3), accelerating the onset of cross-linking and increasing G' compared to the single cure case. increased. In the case of C _NtBEA without the methacrylate functional group of the blocking agent, the storage modulus gradually increased due to the urethane reaction after initial rapid radical crosslinking, and as the temperature increased, the storage modulus increased.

In contrast, the macroscopic cure behavior of C _TBEMA showed the fastest onset time and highest G' at all temperatures regardless of temperature conditions. This is due to the high-density cross-linking network resulting from the additional participation of TBEMA blocking agent in radical cross-linking. Real-time rheological results show that additional radical cross-linking reaction by the TBEMA blocking agent with methacrylate functional group contributes to improving the cross-linking properties of the clear coat under low-temperature curing conditions.

Figure 4 is a diagram showing the real-time crosslinking behavior of a thin transparent coating film depending on the presence or absence of TRI using a rigid pendulum tester under various thermal curing conditions.

As shown in Figure 4, the real-time curing behavior of clearcoat film samples with various bar-coated blocked isocyanates is shown in terms of pendulum oscillation period under the same thermal curing conditions as in the rheological tests.

In the case of single cure with only urethane reaction, similar to the rheological results, crosslinking of C _NtBEA was faster than crosslinking of C _TBEMA through urethane reaction at 120 and 130 °C (Figure 4 (a) and (b)). . Additionally, C _PL350 exhibited cure initiation behavior only at 150°C and exhibited higher oscillatory cycles due to low cross-linking density.

Interestingly, in the case of dual curing, the pendulum oscillation period of C _TBEMA first decreased rapidly through radical cross-linking and then gradually decreased with increasing temperature due to the subsequent urethane reaction.

In the case of C _NtBEA, the vibration period rapidly decreased due to molecular mobility before urethane crosslinking began due to the dissociation of block isocyanate, and then the vibration period slightly increased. This clearly shows the formation of a weak radical cross-linking network.

<Experimental Example 3> Measurement of VOC emissions during heat curing process

Thermogravimetric analysis (TGA Q500, TA Instruments, USA) was performed to investigate VOC emissions (e.g. solvents and blocking agents) of the clearcoat during the thermal curing process. The weight loss of the clearcoat samples was measured under the same thermal conditions as for the curing behavior test, and the temperature was increased from 30°C to 120, 130, and 150°C at a heating rate of 10°C.

Figure 5 is a diagram showing VOCs generated by a clear coat under thermal curing conditions of (a) 120°C and (b) 150°C through TGA analysis.

VOCs (e.g. solvents and blocking agents) are generated in the clearcoat during the thermal curing process.

As shown in Figure 5, the weight loss of the clear coat, which represents VOCs emitted into the atmosphere, was quantitatively analyzed using TGA by comparing the results of a double-cure process using both urethane and radical reactions with the results of a single-cure process using only urethane reaction. did.

Clearcoats using amine derivative-based blocked isocyanates in a single cure process (open symbols in Figure 5) show approximately the same weight loss at all cure temperatures due to low levels of BDE. In the case of C _PL350 , which has a higher BDE and dissociation temperature, the weight loss was much less than the other clearcoats due to lower evaporation of the blocking agent. Not surprisingly, at high curing temperatures (e.g. 150°C), all clearcoats showed relatively high weight loss considering their high dissociation efficiencies.

In the dual cure process, C _NtBEA and C _PL350 showed similar weight loss as in the single cure process. Because the TBEMA blocking agent dissociated from C _TBEMA directly participates in the radical cross-linking reaction with TRI, the weight loss was significantly reduced at a given temperature. The significant reduction in VOCs of C _TBEMA through the dual curing process indicates that the newly developed BI _TBEMA can be applied to an eco-friendly automotive clearcoat coating system.

<Experimental Example 4> Mechanical properties of cured clearcoat film

To analyze the mechanical properties of the clear coat film, it was cured at 120, 130, and 150°C and left at room temperature overnight. Thermodynamic properties were analyzed by measuring the logarithmic damping ratio of the swinging pendulum in dynamic physical test mode using a rigid pendulum tester. A FRB-200 pendulum body with RBP-020 round edges was applied to the cured film surface.

The temperature was increased from 20°C to 200°C at a heating rate of 3°C. The glass transition temperature (T _g ) of the coating film was determined as the temperature at the maximum logarithmic damping ratio.

The storage modulus (G') of the clear coat film cured at various temperatures was measured using DMA (DMA Q800, TA Instruments, USA) to evaluate viscoelastic properties and T _g values. For DMA testing, clear coating films were prepared in Teflon molds (4.0 cm × 1.0 cm × 0.1 cm) and cured in a convection oven at 120, 130, and 150 °C for 1 h. The temperature range is -50 °C to 150 °C and the heating rate is 5°C. A vibration strain of 0.05% was applied at a frequency of 1 Hz. The average molecular weight between cross-linking sites was determined from viscoelasticity results through DMA testing by the following equation:

where ρ, R, T, G ⁰ _N are the density of the cured clearcoat film, the gas constant (8.3145 J/mol·K), the absolute temperature, and the rubbery plateau regime at a specific temperature of 120°C. is the modulus of elasticity. each. Crosslinking density (X _c ) was calculated from the reciprocal of M _c .

The surface hardness of the cured clearcoat film was evaluated using a nano-indentation tester (NHT ³ , Anton Paar, Switzerland) by applying normal force. The Berkovich-type indentation tip was applied to the surface of the cured film by applying a vertical force of up to 40 mN at a loading speed of 80 mN/min, and unloaded at the same speed after a 30-second pause at the maximum force. From the load-displacement curve of the cured clearcoat film, the indentation hardness (HIT) value, which represents the surface hardness of the cured film, was obtained by the Oliver and Pharr method as follows.

Here, F and A _p represent the maximum force and expected contact area, respectively.

The scratch resistance of the cured film under horizontal load was investigated using a nano scratch tester (NST ³ , Anton Paar, Switzerland). During the scratch test, the cured film surface was scratched with a diamond spherical conical tip with a radius of 2 μm.

The applied scratch load gradually increased from 0.1 mN to 40 mN at a rate of 79.8 mN/min. To compare the mechanical properties of the clear coat films in more detail, the critical load (Lc1) at the first fracture, which indicates plastic deformation, was set from a panoramic image of the scratch pattern taken with an optical microscope.

Figure 6 is a diagram showing the logarithmic damping ratio of the clear coat thin film cured at (a) 120 °C, (b) 130 °C, and (c) 150 °C measured using a rigid pendulum physical property tester in physical mode.

As shown in Figure 6, to investigate the thermodynamic properties of the cured clear coat film, the logarithmic damping ratio was determined using the dynamic scanning mode of a rigid body pendulum physical property tester.

The cross-linked polymer chain motion response to thermal energy is represented by a logarithmic damping ratio peak. The glass transition temperature (T _g ), which is related to the thermal stability of the crosslinked film, was determined at the maximum peak temperature of the logarithmic damping ratio, as shown in Table 3.

C _PL350 was excluded from the measurements because it hardly cured at the lower curing temperatures of 120 and 130 °C.

At all temperatures, C _TBEMA and C _NtBEA films showed peak logarithmic attenuation ratios, confirming that they exhibit a dense cross-linking network even at low curing temperatures.

As the curing temperature increased, the T _g value of the clearcoat film cured using amine derivative-based blocked isocyanate increased due to higher crosslinking reaction conversion.

In addition, the thermodynamic properties of the C _TBEMA film surpass those of the C _NtBEA film, showing that TBEMA can auxiliaryly participate in the radical cross-linking reaction and improve the cross-linking properties.

Figure 7 is a diagram showing the storage modulus of clearcoat films cured at (a) 120°C, (b) 130°C, and (c) 150°C through DMA analysis.

As shown in Figure 7, the viscoelastic properties of the clearcoat film cured at 120, 130, and 150°C were evaluated by measuring the storage modulus (G') by DMA in the temperature range of -50 to 150°C. . At low curing temperatures of 120 and 130 °C, the C _PL350 film was excluded from DMA measurements due to its weak cross-linking network.

In all measurements, C _TBEMA showed a higher storage modulus in the rubbery plateau region than C _NtBEA due to the additional radical cross-linking reaction. Because C _TBEMA can be densely cross-linked through dual curing even at low temperatures, its elastic behavior was similar at all temperatures, unlike C _NtBEA .

Tg, M _c and X _c values for clear coat films are described in Table 3.

T _g values obtained from a rigid pendulum physical property tester and DMA are slightly different due to differences in cured film thickness and testing methods.

As mentioned in the viscoelastic properties in Figure 7, the M _c values of C _TBEMA cured at all temperatures were not significantly different due to the similar storage modulus in the rubbery plateau region.

C _TBEMA exhibits significantly lower M _c and larger X _c than other films, indicating that all thermal and mechanical properties of C _TBEMA are superior through active radical cross-linking reaction.

The surface hardness of the cured clear coat film prepared from the rigid pendulum physical property tester was measured using a nano indentation tester.

Figure 8 is a diagram showing the indentation curve and (d) surface strength of clear coat films cured at (a) 120 °C, (b) 130 °C, and (c) 150 °C.

Referring to Figure 8, the C _PL350 film was not fully cured at the low curing temperatures of 120 °C and 130 °C, so the indentation depth profile had poor mechanical properties and the normal force did not reach the maximum force of 40 mN.

At a high curing temperature of 150 °C, where the thermal energy is high enough to form a densely cross-linked network for both cross-linking reactions, the C _TBEMA and C _NtBEA films showed similar indentation curves. However, the C _TBEMA film showed a shallower indentation penetration depth than the C _NtBEA film at lower curing temperatures of 120 and 130 °C.

These results clearly show that the TBEMA blocking agent can participate in radical cross-linking reactions to improve surface resistance to external stress even at low temperatures. Additionally, the surface indentation hardness data of the clearcoat films were compared in terms of the HIT values calculated from the indentation curves based on the Oliver and Pharr methods (Figure 8(d)).

The HIT value of the C _PL350 film decreased significantly from 82.36 MPa to 11.71 MPa as the curing temperature decreased from 150°C to 130°C because BI _PL350 hardly dissociated at low temperatures.

Similar to the results of the indentation curve, the HIT value of C _TBEMA was higher than that of other films at all curing temperature conditions, indicating greater surface hardness. In particular, the HIT value of C _TBEMA at 120°C was better than that of C _PL350 at 150°C, which is the reference level for the clearcoat coating industry.

To evaluate the scratch resistance of the heat-cured clearcoat film, the scratch penetration depth profile was measured using a nano-scratch tester.

Figure 9 is a diagram showing scratch patterns of clearcoat films cured at (a) 120°C, (b) 130°C, and (c) 150°C.

The scratch penetration depth profile of C _PL350 showed very poor scratch resistance and a large variation pattern with respect to external normal force (Figures 9 (a) and (b)). This fluctuation pattern indicates severe fracture strain directly linked to low cross-linking density.

Unlike the NHT results in Figure 8 at all curing temperatures, C _TBEMA and C _NtBEA films showed similar scratch resistance under load and were much better than C _PL350 .

Figure 10 is a diagram showing scratch panoramic images and critical load (Lc1) of clearcoat films cured under various thermal curing conditions.

As shown in Figure 10, a panoramic image of the scratch pattern of the clearcoat film was captured using an optical microscope to visualize the scratch resistance behavior and determine the critical load at first failure (Lc1). As shown in the scratch penetration depth profile (Figure 9), C _PL350 had the least resistance to horizontal scratches and showed highly variable scratch patterns due to fracture strain at low cure temperatures. The scratch pattern of clearcoat films using amine derivative-based blocked isocyanates is smooth and exhibits the Lc1 point at all temperatures. All Lc1 points of C _TBEMA were relatively higher compared to C _NtBEA , confirming lower crack distribution and higher scratch resistance. These results demonstrate that appropriately modified and functionalized blocking agents can improve crosslinking properties and thermal and mechanical properties through a densely crosslinked polymer network through a dual curing process even under low temperature conditions.

In order to use it in the actual automobile coating industry, the base coat was painted first before the clear coat was applied, and then the clear coat was painted.

According to this embodiment, in order to prevent the physical properties from being impaired by the base coat, not only the simple thermal curing process conditions but also additional photocuring (heat-light, heat-light-heat, heat-light-heat-light, etc.) process is added to improve the physical properties. reinforce.

Here, the light used in photocuring may include UV (Ultra Violet), EB (Electron Beam), and LED.

In this embodiment, since photocuring was introduced in the hot coating film immediately after thermal curing, which is an essential process, the fluidity of the unreacted material was secured, allowing additional reaction through photocuring to occur, thereby increasing the crosslinking density.

To confirm this, the mechanical properties of the coating film made under various heat and photocuring process conditions were measured and compared and analyzed using a nano-indentation tester and a nano-scratch tester.

Figure 11 is a diagram showing changes in mechanical properties according to various heat and photocuring process conditions.

Referring to Figure 11, it can be seen that compared to performing only the thermal curing process, when the photo curing process is introduced after the thermal curing process, higher crosslinking density and better mechanical properties of the coating film can be secured. In particular, when the heat curing process and the photo curing process are sequentially repeated (T+UV+T+UV), very high crosslinking density and mechanical properties can be secured.

The above-described embodiments of the present invention have been disclosed for illustrative purposes, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions will be possible. should be regarded as falling within the scope of the patent claims below.

Claims (25)

Isocyanate blocking agent based on an amine derivative capable of radical crosslinking reaction, characterized by having the chemical structure of the following formula (1):
<Formula 1>

In Formula 1, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms. A block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, which is prepared through a urea bond formation reaction between a compound of the following formula (2) and a polyisocyanate compound:
<Formula 2>

In Formula 2, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms. According to paragraph 2,
The polyisocyanate compound is an aliphatic, aromatic, alicyclic, or araliphatic compound, and is a block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, characterized in that it contains two or more isocyanate groups in the molecular structure. According to paragraph 2,
The polyisocyanate compound is a block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, characterized in that it is in the form of a multimer including dimer and trimer. According to paragraph 4,
The polyisocyanate compound is a block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reactions, characterized in that it is a hexamethylene diisocyanate trimer. According to paragraph 2,
The polyisocyanate compounds include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, dodecamethylene diisocyanate, and 2,2-dimethylpentane diisocyanate. Isocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, 1, 6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanate methyl caproate, bis(2-isocyanate ethyl)fumarate, bis(2-isocyanate) Ethyl) carbonate, 2-isocyanate ethyl-2,6-diisocyanate hexanoate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanato-4-isocyanatomethyl octane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane, bis(isocyanatoethyl) carbonate, bis(isocyanatoethyl) ether, 1,4-butylene glycol di. Propyl ether-ω,ω'-diisocyanate, lysine diisocyanato methyl ester, lysine triisocyanate, 2-isocyanatoethyl-2,6-diisocyanato ethyl-2,6-diisocyanato hexanoate, 2 -Isocyanato propyl-2,6-diisocyanato hexanoate, 2,6-di(isocyanatomethyl) furan, 1,3,-bis(6-isocyanato hexyl)-uretidine- A double aliphatic isocyanate capable of urethane and radical crosslinking reaction, characterized in that it is one or more aliphatic isocyanates selected from the group consisting of 2,4-dione, 1,3,5-tris (6-isocyanato hexyl) isocyanurate Block isocyanate based on hardenable amine derivatives. According to paragraph 2,
The polyisocyanate compounds include thiodiethyl diisocyanate, thiopropyl diisocyanate, thiodihexyl diisocyanate, dimethylsulfone diisocyanate, dithio dimethyl diisocyanate, dithio diethyl diisocyanate, dithio propyl diisocyanate, and dicyclohexyl sulfide. A block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, characterized in that it is one or more sulfur-containing aliphatic isocyanates selected from the group consisting of -4,4'-diisocyanate. According to paragraph 2,
The polyisocyanate compound includes diphenyl sulfide-2,4'-diisocyanate, diphenyl sulfide-4,4'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanato dibenzyl thioether, Aromatic sulfide isocyanates such as bis(4-isocyanatomethyl benzene) sulfide, 4,4'-methoxy benzene thioethylene glycol-3,3'-diisocyanate, diphenyl disulfide-4,4'-diisocyanate, 2,2'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethyldiphenyl disulfide-6,6' -Diisocyanate, 4,4'-dimethyldiphenyl disulfide-5,5'-diisocyanate, 3,3'-dimethoxy diphenyl disulfide-4,4'-diisocyanate, 4,4'-dimethoxy diphenyl A block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, characterized in that it is at least one aromatic disulfide-based isocyanate selected from the group consisting of disulfide-3,3'-diisocyanate. According to paragraph 2,
The polyisocyanate compounds include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, and 4,4'-diisocyanate. Phenylenemethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate, ethyl phenylene diisocyanate, 4,4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4'-diisocyanate biphenyl , 3,3'-dimethyl-4,4'-diisocyanate, diphenylmethane, naphthalene diisocyanate, methyl naphthalene diisocyanate, trizine diisocyanate, bis (isocyanatophenyl) ethylene, 3,3'-dimethoxy ratio. Phenyl-4-4'-diisocyanate, isopropylenephenylene diisocyanate, dimethylphenylene diisocyanate, diethylphenylene diisocyanate, diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate, benzene triisocyanate, triisocyanate Phenylmethane triisocyanate, naphthalene triisocyanate, diphenylmethane-2,4,4'-triisocyanate, 3-methyl diphenylmethane-4,6,4'-triisocyanate, 4-methyl-diphenylmethane-3, 5,2',4',6'-pentisocyanate, xylylene diisocyanate, bis(isocyanatoethyl)benzene, bis(isocyanato propyl)benzene, α,α, α',α'-tetramethyl 1 selected from the group consisting of xylylene diisocyanate, bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene, bis(isocyanatomethyl)diphenyl ether, and bis(isocyanatoethyl)phthalate A block isocyanate based on a dual-curable amine derivative capable of radical crosslinking and urethane, which is characterized as being one or more aromatic isocyanates. According to paragraph 2,
The polyisocyanate compounds include diphenyl sulfone-4,4'-diisocyanate, diphenyl sulfone-3,3'-diisocyanate, diphenylmethane sulfone-4,4'-diisocyanate, and 4-methyl diphenylmethane sulfone- 2,4'-diisocyanate, 4,4'-dimethoxy diphenyl sulfone-3,3'-diisocyanate, 3,3'-dimethoxy-4,4'-diisocyanate dibenzyl sulfone, 4,4'-Dimethyldiphenylsulfone-3,3'-diisocyanate,4,4'-di-tert-butyl diphenyl sulfone-3,3'-diisocyanate, 4,4'-methoxy benzene ethylene disulfone-3, A dual-curable amine capable of urethane and radical crosslinking reaction, characterized in that it is at least one aromatic sulfone isocyanate selected from the group consisting of 3'-diisocyanate and 4,4'-dichlorophenylsulfone-3,3'-diisocyanate. Derivative-based block isocyanate. According to paragraph 2,
The polyisocyanate compounds include isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, and bis(2-isocyanate ethyl)-4. -Cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, 2,2-dimethyl dicyclohexylmethane diisocyanate, 2-isocyanato Methyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)- 6-Isocyanatomethyl-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2,2 ,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo [2,2,1]-heptane, 2-isocyanatomethyl- 3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl )-6-(2-isocyanatoethyl)-bicyclo [2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanate natoethyl)-bicyclo[2,1,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2, A block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reaction, characterized in that it is one or more alicyclic isocyanates selected from the group consisting of 2,1]-heptane and norbornane bis(isocyanatomethyl). According to paragraph 2,
The polyisocyanate compound is 1,3-bis (isocyanatomethyl) benzene (m-xylene diisocyanate, m-XDI), 1,4-bis (isocyanatomethyl) benzene (p-xylene diisocyanate, p- XDI), 1,3-bis (2-isocyanato propan-2-yl) benzene (m-tetramethyl xylene diisocyanate, m-TMXDI), 1,4-bis (2-isocyanato propan-2- 1) Benzene (p-tetramethyl xylene diisocyanate, p-TMXDI), 1,3-bis(isocyanatomethyl)-4-methylbenzene, 1,3-bis(isocyanatomethyl)-4-ethylbenzene , 1,3-bis(isocyanatomethyl)-5-methylbenzene, 1,3-bis(isocyanatomethyl)-4,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2 ,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetramethylbenzene, 1,3-bis(isocyanatomethyl)-5-tert-butyl benzene, 1 ,3-bis(isocyanatomethyl)-4-chlorobenzene, 1,3-bis(isocyanatomethyl)-4,5-dichlorobenzene, 1,3-bis(isocyanatomethyl)-2,4 ,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetrachlorobenzene, 1,4-bis(isocyanatomethyl)-2,3,5 Characterized by being at least one aromatic isocyanate selected from the group consisting of 6-tetrabromo benzene, 1,4-bis (2-isocyanatoethyl) benzene, and 1,4-bis (isocyanatomethyl) naphthalene. Block isocyanate based on a dual-curable amine derivative capable of urethane and radical crosslinking reactions. According to paragraph 2,
The block isocyanate is a block isocyanate based on urethane and a dual-curable amine derivative capable of radical crosslinking reaction, characterized in that it has the chemical structure of the following formula (3):
<Formula 3>

In Formula 3, R ₁ is hydrogen or a methyl group, and R ₂ is an alkyl group having 1 to 8 carbon atoms. Block isocyanate according to any one of claims 2 to 13;
At least one polyol selected from acrylic polyols, polyester polyols, polyurethane polyols, acrylic carbamate polyols, and polyester carbamate polyols in which a double bond oligomer group is bonded to some hydroxyl groups; and
A dual-curable composition comprising a thermal radical initiator. According to clause 14,
A dual-curable composition wherein the polyol is an acrylic polyol represented by the following formula (4):
<Formula 4>

Said R is an alkyl group. According to clause 15,
The thermal radical initiator has a typical 1h half-life temperature in the range of 90 to 100°C, and includes tert-Butyl peroxy-isobutyrate, tert-Butyl peroxydiethylacetate, tert-Butyl peroxy-2-ethylhexanoate, Dibenzoyl peroxide, and tert-Amyl peroxy. A dual curable composition characterized in that it is any one of -2-ethylhexanoate or a combination thereof. According to clause 15,
The dual-cure composition is a dual-cure composition, characterized in that the crosslinking reaction temperature is 100 to 130°C. The block isocyanate of any one of claims 2 to 13;
30 to 45% by weight of at least one polyol selected from acrylic polyols, polyester polyols, polyurethane polyols, acrylic carbamate polyols, and polyester carbamate polyols in which a double bond oligomer group is bonded to some hydroxyl groups; and
A dual-cure one-component clear coat composition for automobiles, comprising 25 to 40% by weight of a mixture containing a reactive diluent, an ultraviolet absorber or stabilizer, a leveling agent, and a solvent. According to clause 18,
The polyol has a double bond oligomer content of 20 to 60% by weight based on solid content and a hydroxyl value in the range of 100 to 200 mg KOH per gram of polyol. A dual-cure one-component clear coat composition for automobiles. According to clause 18,
A one-component clear coat composition for dual-cure automobiles, characterized in that the crosslinking reaction temperature of the one-component clear coat composition for dual-cure automobiles is 100 to 130°C. Applying the dual-cure one-component clear coat composition for automobiles of claim 18 on a substrate and performing a first thermal curing process in a preset temperature range;
performing a first photocuring process by irradiating light having a preset amount of light to the substrate immediately after the first thermal curing process is completed; and
A clear coat coating method comprising performing a second thermal curing process in the same temperature range as the first thermal curing process after the first photo curing process is completed. According to clause 21,
The light used for photocuring includes at least one of UV, EB, and LED. Clearcoat coating method. According to clause 21,
A clearcoat coating method further comprising performing an additional thermal curing process at the same temperature range as the first thermal curing process between the first thermal curing process and the first photo curing process. According to clause 21,
A clearcoat coating method further comprising performing a second photocuring process by irradiating light having a preset amount of light to the substrate immediately after the second thermal curing process is completed. A clear coat layer manufactured through the method according to claim 21.