KR101957476B1 - Dual cross-linkable low temperature cure blocked isocyanates and composition comprising the same - Google Patents

Abstract

The present invention relates to a novel block isocyanate of a bifunctional reaction type structure having different dissociation temperatures, and more particularly to an isocyanate group of a polyisocyanate compound which is an aliphatic, aromatic, alicyclic or aromatic aliphatic diisocyanate as a radical initiator Crosslinkable block isocyanate prepared by block polymerization and a monomer or oligomer having both block isocyanate and an ethylenic or acrylic unsaturated double bond and hydroxyl group at the same time. The block isocyanate according to the present invention can be rapidly worked by forming a curing reaction at the surface and interface first by dissociating the blocking group capable of dissociation at a low temperature. Thereafter, cross-linking inside the block isocyanate is prebonded And therefore, it is very useful in coatings, paints, and adhesive technologies that require surface hardening at the process level.

Description

[0001] The present invention relates to a low temperature crosslinkable block isocyanate capable of being cured at a low temperature, and a composition comprising the low temperature crosslinked block isocyanate and a composition comprising the same.

The present invention is directed to a novel block isocyanate of a dual cure reaction type structure having dissociation temperatures different from each other. More specifically, it is possible to use a double-curable low-temperature crosslinking agent prepared by blocking an isocyanate group of a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group with a radical initiator capable of generating a radical by heat or ultraviolet light Type block isocyanate and a low temperature crosslinking composition comprising such a block isocyanate and a monomer or oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group simultaneously.

Blocked isocyanate is blocked by an isocyanate group so that the reaction between the isocyanate group (-NCO) and the hydroxyl group (-OH) or the amine group (-NH ₂ ) does not proceed, thereby producing a one-part coating composition . Blocked isocyanates can be used in organic solvents and waterborne systems, and cross-linking reactions of isocyanate groups and hydroxyl groups are widely used in industry as paints, adhesives, coatings, and the like.

In recent years, automobile steel materials have been replaced by plastic materials, which are lightweight materials, in order to address climate change and environmental problems such as carbon dioxide reduction and fuel efficiency improvement. The mass production of automobiles using such lightweight plastic materials calls for a revolutionary change in the chemical structures of coatings, coatings and adhesives used as commercial products in existing production lines and the reaction processes that can control them. Especially, the conventional high temperature curing process is a low temperature curing process due to the problems of denaturation of plastic materials and various color matching. In addition, automotive coating systems based on existing high-temperature curing type crosslinking methods should avoid the regulation of carbon dioxide emissions due to enormous energy consumption, which is a major cause of warming while discharging a large amount of volatile organic compounds (VOC) and harmful substances In the developed countries, developed technologies are required to replace the existing technologies with original technology for automotive coating system based on environment-friendly low temperature curing technology to cope with new climate change.

Laromer® LR 9000, developed by BASF, has acryl and isocyanate groups at the same time, enabling dual-cure through radical and urethane reactions, resulting in a highly cured film with high scratch resistance . However, Laromer @ LR 9000 has a disadvantage that this liquid system requires separate addition of hardener or reaction initiator and poor storage stability.

In order to improve the storage stability of such isocyanates, a blocking group used in conventional block isocyanates has been used mainly for oxime, caprolactams, and pyrazole. Japanese Patent Publication JP 4879557B discloses a method for producing a block isocyanate compound using a pyrazole compound, and Korean Patent Publication No. KR2007-0064857A discloses an adhesive composition for a tire cord containing a blocked isocyanate compound And U.S. Patent No. US1988-290157A discloses a powder coating composition using a block diisocyanate using acetone oxime.

However, the existing isocyanate blocking group requires excessive high temperature energy due to high dissociation temperature, and when the blocking group is deblocked, the volatile organic compound (VOC) becomes volatile organic compounds (VOC) And the like. Therefore, the new block isocyanate system, which can cure at low temperatures and can compensate for the disadvantages of existing liquid-based systems and reduce VOCs, which are harmful chemicals, at the same time, contributes greatly to energy saving and carbon dioxide emission reduction in coating technology. .

Japanese Patent Publication JP 4879557B Korean Patent Publication JP2007-0064857A US Patent Publication No. US1988-290157A

The present invention has been developed in order to solve the above problems, and it is an object of the present invention to provide a novel block isocyanate capable of curing reaction at a low temperature and simultaneously reducing VOC which is a harmful chemical substance.

In the present invention, the isocyanate group of a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group is blocked with a radical initiator capable of generating a radical by heat or ultraviolet light, It is an object of the present invention to provide a crosslinked block isocyanate.

In the present invention, a composition capable of crosslinking at a low temperature is used as a monomer or oligomer having an ethylenic or acrylic unsaturated double bond or hydroxyl group, which can be mixed with the block isocyanate according to the present invention, or a monomer having an unsaturated double bond and a hydroxyl group simultaneously To provide a low temperature crosslinkable composition comprising an oligomer.

In order to solve the above-mentioned problems, the present invention provides a double-cured product obtained by reacting a compound of the following general formula (A) with a compound having at least one isocyanate-reactive group and at least one free radically polymerizable unsaturated group through a urea bond- Lt; RTI ID = 0.0 > isocyanate < / RTI >

≪ Formula (A)

In Formula A, R ₁ , R ₂ , R _{3, and} R ₄ independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or is a C 3 -C 12 cycloalkyl or aromatic.

In the present invention, the compound of formula (A) may preferably be represented by the following formula (1) or (2).

≪ Formula 1 >

(2)

In the low temperature crosslinkable block isocyanate according to the present invention, the compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group may be a C2-C40 aliphatic, aromatic, alicyclic or aromatic aliphatic compound May be a compound having at least one isocyanate-reactive group and at least one free radically polymerizable unsaturated group such as vinyl group, acryl group or methacryl group in the molecular structure. Preferably, the isocyanate functionalized unsaturated acrylic ester, the unsaturated urethane acrylate, or the free radical polymerizable unsaturated group such as a vinyl group, an acrylic group or a methacrylic group is added to the side chain of the molecular chain with two isocyanate groups at both ends of the molecular chain. May be monomers or oligomers. More preferably, it may be a urethane acrylate or urethane methacrylate oligomer having an isocyanate group at both terminal ends and an acrylic group or a methacrylic group in the side chain of the molecular chain.

Also, the present invention provides a low temperature crosslinkable block isocyanate capable of being cured with a chemical structure represented by the following formula (B).

≪ Formula B >

In formula (B), R ₁ , R ₂ , R ₃ , R ₄ independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or a cycloalkyl or aromatic group of C3-C12, n is an integer greater than or equal to 1, and X comprises at least one free radically polymerizable unsaturated group Or an aliphatic, aromatic, alicyclic or aromatic aliphatic group having from 2 to 20 carbon atoms.

In the low-temperature crosslinkable block isocyanate according to the present invention, the compound of the above formula (B) is a urea bond between a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group and a compound represented by the formula (A) Forming reaction. That is, in Formula B, X may be derived from a C2-C40 aliphatic, aromatic, alicyclic, or aromatic aliphatic compound containing at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group.

In the present invention, the low-temperature crosslinkable composition capable of being cured by double-curing comprises the double-curable low-temperature crosslinkable block isocyanate according to the present invention; And a monomer or oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group at the same time.

In the present invention, the low-temperature crosslinkable composition comprises the double-curable low-temperature crosslinkable block isocyanate according to the present invention; And monomers or oligomers containing only either an unsaturated double bond or a hydroxyl group.

As described above, the new block isocyanate having a double-cure reaction structure having different dissociation temperatures according to the present invention dissociates the blocking group capable of dissociation at a low temperature and forms a hardening reaction at the surface and interface first, And since the internal cross-linking proceeds with the progress of the deblocked pre-isocyanate as the temperature rises, it is very advantageous in application to coatings, paints, and bonding technologies that require rapid surface hardening in the automobile mass production process .

In addition, a novel block isocyanate having a double-cure reaction structure having a dissociation temperature different from each other is prepared by mixing a monomer or an oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group at the same time to form a crosslinking reaction with both unsaturated double bonds and hydroxyl groups Double curing is possible. Also, it can be cured by mixing with a monomer or an oligomer containing only either an unsaturated double bond or a hydroxyl group, so that it can be applied to various coatings, paints, and bonding techniques.

FIG. 1 shows FT-IR spectra of a block isocyanate through reaction of a diisocyanate compound containing a radical initiator and an acrylic ester group according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a preparation example of a pre-mixture of a low-temperature crosslinking composition according to an embodiment of the present invention and a rheology analysis system for analyzing the curing behavior using the same.
FIG. 3 is a graph showing the results of measurement of curing behavior and storage elastic modulus of a pre-mixture using a rheology analysis system according to an embodiment of the present invention with respect to temperature and time.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

As used throughout this specification, the term "polyisocyanate" refers to an isocyanate having two or more isocyanate groups in its molecular structure. More specifically an aliphatic, aromatic, alicyclic, or aromatic aliphatic compound containing 2 to 6 isocyanate groups in the molecular structure. Further, a urea group, a urea group, a biuret group (-NH-CO-NR-CO-NH-) formed by the reaction of an isocyanate with a polyhydric alcohol and a polyhydric amine, A group having 2 to 6 isocyanate groups in the molecular structure and having an allophanate group (-OCONRCONH-) or a uretdine-2,4-dione group (-N (CO) ₂ N-) It means. It is also meant to include a dimer of an aliphatic diisocyanate, a symmetrical or asymmetric trimer, or a compound containing an oligomer in the molecular structure containing 2 to 6 isocyanate groups. In particular, in the case of a timer, it may be decomposed in the reaction to dissociate into three molecules containing two isocyanate groups to finally form six isocyanate groups.

The term " a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group " refers to a compound having at least one isocyanate-reactive group and a vinyl group, an acrylic group, a methacrylate group and a methacrylate group in the molecular structure of an aliphatic, aromatic, alicyclic, Acrylate, or an unsaturated urethane acrylate, or an unsaturated urethane acrylate or an unsaturated urethane acrylate, or a compound having two isocyanate groups at both ends of the molecular chain and having a side chain of a molecular chain Is a monomer or oligomer having at least one free radically polymerizable unsaturated group such as a vinyl group, an acryl group or a methacryl group. More preferably, it is a urethane acrylate or urethane methacrylate monomer or oligomer having an isocyanate group at both terminal ends and an acrylic group or methacryl group at the side chain of the molecular chain.

On the other hand, the term "derived " as used throughout the term is intended to mean that the isocyanate group is blocked by reaction of the polyisocyanate or the isocyanate group of the compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group with the radical initiator, Refers to the molecular structure of the corresponding polyisocyanate or a compound having at least one free radically polymerizable unsaturated group except for the urea group which is a bond.

The term "radical initiator" in the present invention includes both a thermal initiator that generates radicals by heat and a photo initiator that generates radicals by light such as ultraviolet light. In the present invention, The radical initiator is more preferably a thermal initiator, but may also be used as a radical initiator by mixing a thermal initiator and a photoinitiator as necessary.

The term " TRI " used throughout this specification is an abbreviation for a thermal radical initiator and means a thermal radical initiator.

In the present invention, in order to solve the above-mentioned problems, the present invention can be produced through a urea bond formation reaction of a compound of the following formula (A) with a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group.

≪ Formula (A)

In Formula A, R ₁ , R ₂ , R _{3, and} R ₄ independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or is a C 3 -C 12 cycloalkyl or aromatic.

In the present invention, the compound of formula (A) may preferably be represented by the following formula (1) or (2).

≪ Formula 1 >

(2)

In the low temperature crosslinkable block isocyanate according to the present invention, the compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group may be a C2-C40 aliphatic, aromatic, alicyclic or aromatic aliphatic compound Means a compound having at least one isocyanate-reactive group and at least one free radically polymerizable unsaturated group such as vinyl group, acryl group or methacryl group in the molecular structure, and is preferably an isocyanate-functionalized unsaturated acrylate ester, an unsaturated urethane acrylate, May be a monomer or oligomer having two isocyanate groups at both ends of the molecular chain and having at least one free radically polymerizable unsaturated group such as a vinyl group, an acrylic group and a methacrylic group in the side chain of the molecular chain. More preferably, it may be a urethane acrylate or urethane methacrylate monomer or oligomer having an isocyanate group at both terminal ends and an acrylic group or methacryl group at the side chain of the molecular chain.

In the low temperature crosslinkable block isocyanate capable of being cured in accordance with the present invention, the compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group may have a chemical structure represented by the following formula (3).

(3)

In Formula 3, n is an integer of 1 to 5.

The present invention provides a low temperature crosslinkable block isocyanate capable of being cured with a chemical structure represented by the following chemical formula (B).

≪ Formula B >

In formula (B), R ₁ , R ₂ , R ₃ , R ₄ independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or a cycloalkyl or aromatic group of C3-C12, n is an integer greater than or equal to 1, and X comprises at least one free radically polymerizable unsaturated group Or an aliphatic, aromatic, alicyclic or aromatic aliphatic group having from 2 to 30 carbon atoms.

In the low temperature crosslinkable block isocyanate according to the present invention, the formula (B) is a urea bond forming reaction between a compound of the formula (A) and a compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group Wherein X in formula (B) is at least one isocyanate-reactive group in the molecular structure of an aliphatic, aromatic, alicyclic or aromatic aliphatic compound of C2-C40 and at least one isocyanate-reactive group and a free radically polymerizable unsaturated group such as a vinyl group, May be derived from compounds having one or more groups. Preferably, the isocyanate functionalized unsaturated acrylic ester, the unsaturated urethane acrylate, or the free radical polymerizable unsaturated group such as a vinyl group, an acrylic group or a methacrylic group is added to the side chain of the molecular chain with two isocyanate groups at both ends of the molecular chain. Or more may be derived from monomers or oligomers. More preferably, it may be derived from a urethane acrylate or urethane methacrylate monomer or oligomer having an isocyanate group at both ends and an acrylic group or methacryl group at the side chain of the molecular chain.

The low temperature crosslinkable block isocyanate capable of being cured according to the present invention may have a chemical structure represented by the following formula (4).

≪ Formula 4 >

In Formula 4, n is an integer of 1 to 5.

In the present invention, low temperature crosslinkable block isocyanate capable of being cured at a low temperature; And a low-temperature crosslinkable composition comprising a monomer or an oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group simultaneously.

Meanwhile, monomers or oligomers which can be used in the low-temperature crosslinkable composition according to the present invention have ethylenic or acrylic unsaturated double bonds in their branching structure or monomers or oligomers having hydroxyl groups can be used. However, for effective low- Or an acrylic unsaturated double bond and a hydroxyl group at the same time. Such monomers or oligomers can be used as the main resin of the low-temperature crosslinkable composition, and the block isocyanate according to the present invention can simultaneously serve as a radical generating initiator and as a crosslinking agent for effective crosslinking.

The monomer or oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group according to an embodiment of the present invention may be used as a main resin and may have a chemical structure represented by Chemical Formula 5 below.

≪ Formula 5 >

In addition, the low-temperature crosslinkable composition according to the present invention may contain various additives depending on the specific use, such as a reactive diluent such as diacrylate and an inorganic filler, if necessary. Preferably, the reactive diluent according to one embodiment of the present invention may be 1,6-hexanediol diacrylate.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. In particular, the technical idea of the present invention and its core structure and action are not limited by this. In addition, the content of the present invention can be implemented by various other types of equipment, and is not limited to the embodiments and examples described herein.

Preparation Example 1: Preparation of compound of formula (1)

The compound of formula (1), which is a thermal radical initiator (TRI) according to one embodiment of the present invention, can be prepared according to the following reaction formula (1).

≪ Formula 1 >

<Reaction Scheme 1>

First, 30.0 g (265 mmol) of cyclohexanone oxime was stirred in 300 ml of tetrahydrofuran in an argon atmosphere, and then 1.06 g (26.5 mmol) of sodium hydroxide and 45.6 g (221 mmol) of dicyclohexylmethaneindiimine were added thereto. Lt; / RTI &gt; at room temperature. After completion of the reaction, dichloromethane was added, followed by stirring for 30 minutes, followed by vacuum filtration. The solvent was removed by concentration under reduced pressure, and the residue was dissolved in hexane, followed by addition of acetonitrile, followed by stirring for 1 hour. Thereafter, only a hexane layer was obtained and concentrated under reduced pressure to remove the solvent to obtain 50.47 g (158 mmol) of the compound of the formula (1).

Preparation Example 2: Preparation of the compound of formula (2)

The compound of Formula 2, which is a thermal radical initiator (TRI) according to one embodiment of the present invention, can be prepared according to the following Reaction Scheme 2.

(2)

<Reaction Scheme 2>

After 30.0 g (303 mmol) of cyclopentanone oxime was stirred in 300 ml of tetrahydrofuran in an argon atmosphere, 1.21 g (30.3 mmol) of sodium hydroxide and 52.0 g (252 mmol) of dicyclohexylmethaneindiimine were added and the mixture was stirred for 24 hours The mixture was stirred at room temperature. After completion of the reaction, dichloromethane was added, followed by stirring for 30 minutes, followed by vacuum filtration. The solvent was removed by concentration under reduced pressure, and the residue was dissolved in hexane, followed by addition of acetonitrile, followed by stirring for 1 hour. Thereafter, only a hexane layer was obtained, and the solvent was removed by concentration under reduced pressure to obtain 44.8 g (147 mmol) of the compound of the formula (2).

Preparation Example 3: Preparation of compound of formula (4)

The compound of formula (4) according to one embodiment of the present invention can be prepared according to the following reaction formula (3).

&Lt; Formula 4 >

In Formula 4, n is an integer of 1 to 5.

<Reaction Scheme 3>

2.59 g (36.9 mmol) of the compound of the formula (1) are stirred in 250 ml of dichloromethane in an argon atmosphere. Then 2 g of Laromer LR 9000 of formula (3) was added and stirred at 35 ° C for 24 hours. As the reaction proceeded, the disappearance of the NCO peak was confirmed by IR spectrum as shown in FIG. 1, and after completion of the reaction, the reaction mixture was concentrated under reduced pressure to remove the solvent to obtain 4.6 g of the compound of Formula 4.

Example 1. Preparation and curing of pre-mixture

In order to test the low temperature crosslinking of the low temperature crosslinking block isocyanate according to one embodiment of the present invention, the compound of the formula (4) prepared according to Preparation Example 3 was used as the low temperature crosslinking type block isocyanate capable of double curing and the acrylic unsaturated double (DCR-4274: Formula 5), 1,6-hexanediol diacrylate as a reactive diluent and a rotation rheometer (MCR-301, Anton Paar, Austria) was used to measure the storage modulus with curing temperature and time.

The preparation method and measurement conditions of the specific pre-mixture are as follows. First, 2 g of HFUMO (DCR-4274, Formula 18), which is the main resin containing a 60% double bond (-C═C-) and 80 mg of KOH / g hydroxy (-OH) group, 1 g of hexanediol diacrylate) and 0.42 g of a block isocyanate of formula (4) were added and mixed to prepare a pre-mixture. To measure the curing behavior and modulus of the resulting mixture according to the temperature, temperature rise rate conditions at 20 ℃ for 25 min to 170 ℃ as rotation under (UV light: 6.0 mW / cm 2, Temperature: 25 ℃, Strain:: 2%, Frequency 5Hz) rheometer (MCR-301, Anton Paar, Austria) and the results are summarized in FIG.

The low temperature cross-linkable block isocyanate according to the present invention can rapidly accelerate the curing time, thereby rapidly providing surface hardness and hardening, thereby minimizing contact with various dusts and deterioration of physical properties under processing conditions As a double cure, it provides a higher degree of crosslinking of the polymer to give a high modulus, and it has an advantage that it can provide relatively excellent characteristics even in the mechanical / chemical properties externally applied. In addition, while the existing Laromer 9000 is applied to this liquid type system, the present invention can be used as a one-pack type, which is easy to use and applicable to various fields.

As described above, the block isocyanate according to the present invention and the composition containing the block isocyanate having a dissociation temperature different from each other have a double curing reaction structure, and the blocking group capable of dissociation at a low temperature is dissociated and the curing reaction at the surface and interface It is possible to perform a quick coating process by first forming and then cross-linking in the inside, since the prebonded pre-isocyanate progresses as the temperature rises, so that coatings and paints that require rapid surface hardening at the process level, Is very large.

Claims (8)

A compound having at least one isocyanate group and at least one free radically polymerizable unsaturated group blocked with a compound having a chemical structure represented by the following formula (A)
A low temperature cross-linkable block isocyanate capable of being cured at a low temperature,
&Lt; Formula (A)

R ₁ , R ₂ , R _{3 and} R ₄ in the above formula (A) independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or a cycloalkyl or aromatic group of C 3 -C 12,
&Lt; Formula B &gt;

In formula (B), R ₁ , R ₂ , R ₃ , R ₄ independently form a normal alkyl, cyclic ring together with the carbon to which they are attached, or a cycloalkyl or aromatic group of C3-C12, n is an integer greater than or equal to 1, and X comprises at least one free radically polymerizable unsaturated group Or an aliphatic, aromatic, alicyclic or aromatic aliphatic group having from 2 to 20 carbon atoms. delete The method according to claim 1,
Wherein the compound of formula (A) is a double-curable low-temperature crosslinking block isocyanate represented by the following formula (1) or (2).
&Lt; Formula 1 >

(2)

The method according to claim 1,
The compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group may be an isocyanate-functionalized unsaturated acrylic ester, an unsaturated urethane acrylate, or a compound having two isocyanate groups at both ends of the molecular chain, Crosslinkable block isocyanate capable of being cured at a low temperature, characterized by being a monomer or an oligomer having at least one free radical polymerizable unsaturated group of an acryl group or a methacryl group. The method according to claim 1,
The compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group is a urethane acrylate or urethane methacrylate monomer or oligomer having an isocyanate group at both terminals and an acrylic group or methacryl group at the side chain of the molecular chain Low-temperature cross-linkable block isocyanate capable of double curing. The method according to claim 1,
Wherein the compound having at least one isocyanate reactive group and at least one free radically polymerizable unsaturated group has the chemical structure represented by the following formula (3).
(3)

In Formula 3, n is an integer of 1 to 5. The method according to claim 1,
Wherein the block isocyanate has a chemical structure represented by the following formula (4).
&Lt; Formula 4 >

In Formula 4, n is an integer of 1 to 5. A low temperature crosslinkable block isocyanate as claimed in any one of claims 1 to 7; And
A low temperature crosslinkable composition capable of being cured by double-curing, which comprises a monomer or an oligomer having both an ethylenic or acrylic unsaturated double bond and a hydroxyl group.

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