CN113831456A - Composition comprising a hydroxy acrylic resin and two-component coating composition comprising the same - Google Patents
Composition comprising a hydroxy acrylic resin and two-component coating composition comprising the same Download PDFInfo
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- CN113831456A CN113831456A CN202010589480.5A CN202010589480A CN113831456A CN 113831456 A CN113831456 A CN 113831456A CN 202010589480 A CN202010589480 A CN 202010589480A CN 113831456 A CN113831456 A CN 113831456A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
- C08G18/6216—Polymers of alpha-beta ethylenically unsaturated carboxylic acids or of derivatives thereof
- C08G18/622—Polymers of esters of alpha-beta ethylenically unsaturated carboxylic acids
- C08G18/6225—Polymers of esters of acrylic or methacrylic acid
- C08G18/6229—Polymers of hydroxy groups containing esters of acrylic or methacrylic acid with aliphatic polyalcohols
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
- C09D175/04—Polyurethanes
Abstract
The present invention relates to a composition comprising a hydroxyacrylic resin and a two-component coating composition comprising the same, wherein the hydroxyacrylic resin is formed by solution polymerization of a monomer mixture comprising, relative to the total weight of the monomer mixture, a)1 to 10 wt. -% of a multifunctional melamine formaldehyde acrylic resin; b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate; and c)45 to 80% by weight of other ethylenically unsaturated monomers other than a) and b); wherein the composition has a solids content of at least 75 wt% based on the weight of the hydroxyacrylic resin. The invention furthermore relates to a two-component coating composition comprising the above-described hydroxyacrylic resin-containing composition and a polyisocyanate crosslinking agent.
Description
Technical Field
The invention relates to a resin composition with high solid content and low viscosity, in particular to a composition containing hydroxy acrylic resin. The invention also relates to a two-component coating composition comprising said resin composition.
Background
In recent years, with environmental concerns, environmental laws have been enacted in many countries and there is a demand for further reduction in the amount of VOCs that are allowed to be released into the air by coating compositions, particularly solvent-based coating compositions.
The aim of the coating industry is to develop various green environment-friendly coatings to replace the current solvent-based coatings; the current development of environment-friendly coatings has the following directions: high-solid low-viscosity paint, water-based paint, powder paint and UV light-cured paint. Compared with other solutions of environment-friendly coatings, the production of the high-solid low-viscosity coating can utilize the existing traditional solvent-based coating production equipment and can be matched with the traditional solvent-based coating system, so that the high-solid low-viscosity coating is rapidly developed at home and abroad in recent years.
The hydroxyl acrylic resin is a very important film-forming resin for a solvent type coating composition, can be cured by various modes, such as curing with an isocyanate curing agent at a low temperature and curing with an amino resin curing agent at a high temperature, has high curing speed without influencing gloss and color, and has higher hardness, weather resistance, color retention, adhesion and water resistance. Therefore, the hydroxyl acrylic resin has wide application in aviation, automobile, traffic, machinery and light industrial products.
The development of a high-solid low-viscosity (hereinafter simply referred to as "high-solid low-viscosity") hydroxyacrylic resin composition has rapidly progressed in recent years. However, most of the high-solid low-viscosity hydroxy acrylic resin compositions on the market at present have the disadvantages of slow curing speed, low hardness and the like.
Therefore, there is still a need in the coatings industry for a hydroxyacrylic resin composition that combines high solids, low viscosity, and high cure rate.
Disclosure of Invention
The present invention provides a composition comprising a hydroxyacrylic resin, wherein the hydroxyacrylic resin is formed by solution polymerization of a monomer mixture comprising, relative to the total weight of the monomer mixture,
a)1-10 wt% of a multifunctional melamine formaldehyde acrylic resin;
b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate; and
c)45 to 80% by weight of other ethylenically unsaturated monomers other than a) and b);
wherein the composition has a solids content of at least 75 wt% based on the weight of the hydroxyacrylic resin.
In an embodiment according to the invention, the composition comprising a hydroxyacrylic resin has a viscosity in the range of 500 to 5000mpa.s, measured at 25 ℃ with a BROOKFIELD viscometer.
In an embodiment according to the invention, the hydroxyl value of the hydroxyacrylic resin is in the range of 30-180mg KOH/g.
According to another aspect of the present invention, there is provided a two-component coating composition comprising,
(i) a film-forming resin composition comprising the composition comprising a hydroxyacrylic resin according to the present invention; and
(ii) a polyisocyanate crosslinking agent.
In an embodiment according to the present invention, the cured coating obtained from the two-component coating composition according to the present invention has a pencil hardness of at least 3B, preferably at least 2B after baking at 60 ° for 20 minutes according to GB/T6739-2006.
In the present invention, the applicant has utilized a specific multifunctional melamine formaldehyde acrylic resin as a monomer, mixed with other common acrylic resin monomers, and solution polymerized to obtain a high-solid low-viscosity hydroxy acrylic resin-containing composition. The hydroxy acrylic resin has a three-dimensional highly branched structure, does not undergo chain entanglement among molecules, and has a viscosity much lower than that of a linear analogue having a similar molecular weight, so that the composition has a solid content of 75% by weight or more and a viscosity as low as 500 mPas-5000 mPas. The composition containing the hydroxyl acrylic resin synthesized by the invention has the characteristics of simple preparation process, low cost, high curing speed, high hardness and the like, and can be applied to the fields of heavy machinery coating and the like.
The details of one or more embodiments of the invention are set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
Definition of
As used herein, "a", "an", "the", "at least one" and "one or more" and the instances where no numerical word is used, are used interchangeably. Thus, for example, a component that contains "an" additive can be interpreted to mean that the component contains "one or more" additives.
Optional components not contemplated by the present invention are not contemplated to be excluded from the composition where the composition is described as including or comprising specific components, and the composition is contemplated to be comprised or consisting of the components involved, or optional process steps not contemplated by the present invention are contemplated to be excluded from the method where the method is described as including or comprising specific process steps, and the method is contemplated to be comprised or consisting of the process steps involved.
For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.
In the context of the present invention, "hydroxyacrylic resins" refers to the class of resins obtained by polymerizing (meth) acrylate-based monomers and hydroxyalkyl (meth) acrylate monomers, and optionally other ethylenically unsaturated monomers, in the presence of an initiator.
The term "high solids" when used in reference to a "resin composition" means that the resin composition has a solids content of at least 75 percent by weight or greater, wherein the solids content is based on the weight of the resin components in the resin composition.
In the context of the present invention, the term "solvent-borne coating composition" refers to a coating composition having a water content of less than 2g/L, preferably substantially free, more preferably substantially completely free, still more preferably completely free of water, with an organic solvent as the dispersing medium.
The term "substantially free of water when used with respect to a" solvent-borne coating composition "means that the solvent-borne coating composition of the present invention comprises less than 1000 parts per million (ppm) of water; the term "essentially free of water means that the solvent borne coating composition of the present invention comprises less than 100ppm water; the term "essentially completely free of water means that the solvent borne coating composition of the present invention contains less than 5ppm water; the term "completely free of water means that the solvent borne coating compositions of the present invention contain less than 20 parts per billion (ppb) of water.
In the context of the present invention, the term "ethylenically unsaturated monomer" refers to a monomer having an ethylenically unsaturated group comprising a reactive carbon-carbon double bond unsaturated group in cis-or trans-configuration, but not comprising an aromatic unsaturated group, a carbon-carbon triple bond, a carbon-heteroatom unsaturated group.
In the context of the present invention, the term "monomer mixture" means a mixture of monomers having reactivity, excluding solvents which do not participate in the reaction.
The terms "comprise" and "comprise," and variations thereof, when appearing in the specification and claims, have no limiting meaning.
The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits under certain circumstances. However, other embodiments may be preferred, under the same or other circumstances. In addition, recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
Detailed Description
In one aspect, the present invention provides a composition comprising a hydroxyacrylic resin, wherein the hydroxyacrylic resin is formed by solution polymerization of a monomer mixture comprising, relative to the total weight of the monomer mixture,
a)1-10 wt% of a multifunctional melamine formaldehyde acrylic resin;
b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate; and
c)45 to 80% by weight of other ethylenically unsaturated monomers other than a) and b);
wherein the composition has a solids content of at least 75 wt% based on the weight of the hydroxyacrylic resin.
The hydroxyacrylic resin-containing compositions according to the present invention not only have a high solids content, but also have a very low viscosity, and thus can be used to formulate solvent-borne coating compositions without introducing excessive amounts of VOCs. In an embodiment according to the invention, the composition comprising a hydroxyacrylic resin has a solids content of at least about 75 wt. -%, preferably of at least 78 wt. -%, more preferably of at least 80 wt. -%, based on the weight of the hydroxyacrylic resin. The inventors have surprisingly found that the composition of the hydroxyacrylic resins of the present invention has a significantly lower viscosity while maintaining a high solids content. In an embodiment according to the present invention, the hydroxyacrylic resin composition has a viscosity of 5000mpa.s or less, more preferably 4000mpa.s or less, more preferably 3000mpa.s or less, measured at 25 ℃ using a BROOKFIELD viscometer.
Preferably, in some embodiments according to the invention, the composition comprising a hydroxyacrylic resin has a viscosity in the range of 500 to 5000mpa.s, preferably in the range of 600 to 3500mpa.s, more preferably in the range of 800 to 2500mpa.s, measured at 25 ℃ using a BROOKFIELD viscometer.
The viscosity of the composition comprising a hydroxyacrylic resin according to the invention is related to the molecular weight and the molecular weight distribution of the hydroxyacrylic resin. Thus, in some embodiments according to the present invention, the number average molecular weight (Mn) of the hydroxyacrylic resin is in the range of 800-8000g/mol, preferably in the range of 1000-3000 g/mol; and a molecular weight distribution coefficient (PDI ═ Mw/Mn) in the range of 1.5 to 4. The molecular weight and the molecular weight distribution coefficient may be determined using Gel Permeation Chromatography (GPC), such as Agilent 1260.
In the composition comprising a hydroxyacrylic resin according to the invention, the hydroxyacrylic resin is hydroxyl-functional. Thus, according to an embodiment of the present invention, the hydroxyl value of the hydroxy acrylic resin is greater than 30mg KOH/g. In one embodiment of the invention, the hydroxy acrylic resin has a hydroxyl number of 30 to 180mg KOH/g, preferably 70 to 120mg KOH/g. The hydroxyl number is determined by titration according to ISO 4629-1998.
In the composition comprising a hydroxyacrylic resin according to the present invention, the hydroxyacrylic resin is formed by solution polymerization of a monomer mixture, and thus the composition comprising a hydroxyacrylic resin according to the present invention comprises a certain amount of an organic solvent. However, the composition is again high in solids and low in viscosity and therefore contains a relatively small amount of organic solvent, for example not more than 25% by weight, preferably not more than 23% by weight, of organic solvent, relative to the total weight of the composition comprising the hydroxyacrylic resin.
The composition comprising the hydroxyacrylic resin is prepared by using a solvent, which may be selected from those commonly used in the art, and examples thereof include, but are not limited to, aromatic hydrocarbons such as benzene, toluene, xylene, etc.; alcohols such as ethanol, isopropanol, n-butanol, t-butanol, and ethylhexanol, etc.; esters such as ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and the like. Other suitable solvents include ketones such as methyl ethyl ketone, methyl n-amyl ketone, methyl isobutyl ketone, and the like; glycols, such as propylene glycol and diethyl glycol; glycol ethers, such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether. Of course, various mixtures of solvents may be used. According to the invention, the amount of organic solvent can be very low, for example not more than 25% by weight of organic solvent, preferably not more than 23% by weight of organic solvent, relative to the total weight of the composition comprising the hydroxyacrylic resin, without affecting the preparation of the composition comprising the hydroxyacrylic resin.
According to the invention, the monomer mixture comprises, relative to the total weight of the monomer mixture, a)1 to 10% by weight of a polyfunctional melamine formaldehyde acrylic resin; b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate; and c) from 45 to 80% by weight of other ethylenically unsaturated monomers which are different from components a) and b).
The inventors of the present invention have surprisingly found that a high solids low viscosity hydroxy acrylic resin containing composition is obtained by solution polymerization using a specific multifunctional melamine formaldehyde acrylic resin (hereinafter referred to as "first monomer") as a monomer in the presence of an initiator and a very small amount of an organic solvent, in combination with other conventional acrylic monomers. In an embodiment according to the invention, the multifunctional melamine formaldehyde acrylic resin has a functionality of 3 to 6. The hydroxy acrylic resin produced by copolymerizing the multifunctional melamine formaldehyde acrylic resin with the hydroxy C1-C20 alkyl (meth) acrylate and other ethylenically unsaturated monomers has a high degree of branching, does not undergo intermolecular chain entanglement due to a three-dimensional highly branched structure of the molecules, and has a viscosity much lower than that of a linear analog having a similar molecular weight to that of the hydroxy acrylic resin, so that a composition comprising the hydroxy acrylic resin can have a solid content of 75% by weight or more and a viscosity as low as 1000-5000 mPas based on the weight of the hydroxy acrylic resin.
Therefore, in the preparation of the composition comprising a hydroxyacrylic resin according to the present invention, the first monomer is necessary. As described above, the inventors have surprisingly found that by introducing a first monomer, namely a multifunctional melamine formaldehyde acrylic resin (preferably having a functionality of 3 to 6) during the preparation of the resin composition, the viscosity of the resin composition can be significantly reduced while maintaining a high solids content of the resin composition, so that the resin composition can be formulated into solvent-borne coating compositions having low VOC emissions without the need for additional reactive diluents.
Examples of suitable hydroxy C1-C20 alkyl (meth) acrylates include, but are not limited to, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, or any combination thereof. Preferably, the hydroxy C1-C20 alkyl (meth) acrylate is selected from at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, more preferably, from hydroxyethyl methacrylate.
In the present invention, hydroxy C1-C20 alkyl (meth) acrylates are present so that the final resin composition obtained is hydroxy-functional. Preferably, the hydroxy C1-C20 alkyl (meth) acrylate is present in an amount of 10 to 45 wt. -%, preferably 15 to 40 wt. -%, based on the total weight of the monomer mixture. The presence of hydroxy C1-C20 alkyl (meth) acrylate monomers ensures that the resulting composition comprising a hydroxy acrylic resin according to the present invention can be used to formulate two-component solvent borne coating compositions.
In the composition comprising a hydroxy acrylic resin according to the invention, the monomer mixture also comprises other ethylenically unsaturated monomers other than the above multifunctional melamine formaldehyde acrylic resin and hydroxy C1-C20 alkyl (meth) acrylates, which can be used to adjust the mechanical strength of the resulting resin composition. Examples of suitable other ethylenically unsaturated monomers different from a) and b) include, but are not limited to, C1-C20 alkyl (meth) acrylates, vinyl aromatic compounds having up to 20 carbon atoms, and optionally unsaturated carboxylic acids. The unsaturated carboxylic acid refers to an unsaturated carboxylic acid having a double bond structure, preferably acrylic acid and/or methacrylic acid.
Thus, according to one embodiment of the present invention, the monomer mixture comprises, relative to the total weight of the monomer mixture,
a)1-10 wt% of a multifunctional melamine formaldehyde acrylic resin;
b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate;
c1) 35-60% by weight of a C1-C20 alkyl (meth) acrylate;
c2) 10-50% by weight of a vinylaromatic compound having up to 20 carbon atoms; and
c3) 0-5% by weight of (meth) acrylic acid.
Examples of suitable C1-C20 alkyl methacrylates suitable for use in the present invention include, but are not limited to, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate (also known as isooctyl methacrylate), nonyl methacrylate, 2-methyloctyl methacrylate, 2-t-butyl heptyl methacrylate, 3-isopropylheptyl methacrylate, decyl methacrylate, undecyl methacrylate, 5-methylundecyl methacrylate, dodecyl methacrylate, 2-methyldodecyl methacrylate, tridecyl methacrylate, 5-methyltrodecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, 2-methylhexadecyl methacrylate, heptadecyl methacrylate, 5-isopropylheptadecyl methacrylate, 5-ethyloctadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, cycloalkyl methacrylates (e.g., cyclopentyl methacrylate, cyclohexyl methacrylate, 3-vinyl-2-butylcyclohexyl methacrylate, cycloheptyl methacrylate, and the like), Cyclooctyl methacrylate), bornyl methacrylate, and isobornyl methacrylate. Preference is given to methyl methacrylate, ethyl methacrylate, butyl methacrylate, tert-butyl methacrylate or isobornyl methacrylate, particular preference to methyl methacrylate or isobornyl methacrylate.
Examples of suitable C1-C20 alkyl acrylates suitable for use in the present invention include, but are not limited to, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate (also known as isooctyl acrylate), nonyl acrylate, 2-methyl-octyl acrylate, 2-tert-butyl heptyl acrylate, 3-isopropyl heptyl acrylate, decyl acrylate, undecyl acrylate, 5-methyl undecyl acrylate, dodecyl acrylate, 2-methyl dodecyl acrylate, tridecyl acrylate, and mixtures thereof, 5-methyltrodecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, 2-methylhexadecyl acrylate, heptadecyl acrylate, 5-isopropylheptadecyl acrylate, 5-ethyloctadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, cycloalkyl acrylates (e.g., cyclopentyl acrylate, cyclohexyl acrylate, 3-vinyl-2-butylcyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate), bornyl acrylate, and isobornyl acrylate. Preference is given to ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate or cyclohexyl acrylate, particular preference to ethyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate.
Examples of vinyl aromatic compounds having up to 20 carbon atoms include, but are not limited to, styrene, vinyl toluene, o-methyl styrene, p-methyl styrene, α -butyl styrene, 4-n-decyl styrene, halogenated styrenes (e.g., monochlorostyrene, dichlorostyrene, tribromostyrene, or tetrabromostyrene), with styrene being preferred.
Accordingly, the present invention also relates to a process for preparing a composition comprising a hydroxyacrylic resin according to the present invention, said process comprising: initiating polymerization of the monomer mixture with an initiator in the presence of an organic solvent in an amount of no more than 25% by weight, preferably no more than 23% by weight, relative to the total weight of the hydroxyacrylic resin-containing composition, and a chain transfer agent, thereby forming the hydroxyacrylic resin-containing composition. The composition thus obtained has a solids content of at least 75% by weight, based on the weight of the hydroxyacrylic resin.
Suitable conditions for the above reaction depend on various factors including the type of the monomer to be polymerized and the type of the initiator, etc., which can be determined empirically by those skilled in the art.
Any known thermal initiator may be used to initiate the polymerization reaction. Examples of suitable thermal initiators include persulfates, such as ammonium persulfate or alkali metal persulfates (including potassium, sodium or lithium); peroxides, such as benzoyl peroxide, cumyl hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, di-tert-amyl peroxide, 1-bis (tert-amyl peroxy) cyclohexane, dioctyl peroxide, tert-butyl pervalerate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl perisononanoate, tert-butyl peroctoate, tert-butyl perneodecanoate, di (2-ethylhexyl) peroxydicarbonate, di (isotridecyl) peroxydicarbonate; azo compounds, such as azobisisobutyronitrile), azobisisovaleronitrile, and azobis (4-cyanovaleric acid). Preferably, oil-soluble thermal initiators azo-type initiators or peroxides are used, such as azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile, azobisdicyclohexylcarbonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl 2-ethylhexanoate peroxide, 1-bis (tert-amylperoxy) cyclohexane, di-tert-butyl peroxide, di-tert-amylperoxide. More specifically, azobisisobutyronitrile, di-t-butyl peroxide or di-t-amyl peroxide is used as the thermal initiator. Preferably, the thermal initiator is present in an amount of 0.1 to 10% by weight relative to the total charge.
Particularly, the initiator is added in a manner that the initiator and a reactant needing to be reacted are uniformly mixed, and then the mixture is added into the solvent in a dropwise manner, or the initiator and the reactant needing to be reacted are separately stored and are added into the solvent dropwise at the same time, wherein the dropwise adding time is 1-8 hours, preferably 3-6 hours.
According to the invention, during the preparation of the composition comprising a hydroxyacrylic resin, a chain transfer agent is added, said chain transfer agent being selected from one or more of isopropanol, halogenated compounds, linear or branched C2-C22 alkyl mercaptans, mercaptoalkanols, mercaptoalkanoic acids and alkyl mercaptoalkanoates, preferably from one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoethanol and mercaptopropionic acid, preferably present in an amount of 0.1 to 10% by weight relative to the total charge. The chain transfer agent may be added in one or more portions or continuously, linearly or non-linearly over most or all of the reaction period.
The inventors have surprisingly found that the composition comprising a hydroxyacrylic resin according to the present invention can be used alone or as a film-forming resin composition in combination with a crosslinker capable of crosslinking therewith to give a two-component coating composition curable under high temperature baking conditions. The invention obtains the composition containing the hydroxy acrylic resin with specific molecular weight, molecular weight distribution and hydroxyl value by selecting specific polymerizable monomers and specific process conditions. Two-component coating compositions formulated from such a composition comprising a hydroxyacrylic resin exhibit a high hardness after curing to a lacquer film, for example a pencil hardness of at least 3B, preferably at least 2B after baking at 60 ° for 20 minutes according to GB/T6739-2006.
Thus, according to another aspect of the present invention, there is provided a two-component coating composition comprising:
(i) a film-forming resin composition comprising a hydroxyacrylic resin according to the present invention; and
(ii) a polyisocyanate crosslinking agent.
The cured coating obtained from the two-component coating composition according to the invention has a pencil hardness of at least 3B, preferably at least 2B after baking at 60 ° for 20 minutes according to GB/T6739-2006.
Polyisocyanate crosslinking agent
The term "polyisocyanate crosslinker" as used herein refers to a polyisocyanate compound, an isocyanate oligomer, or a combination thereof. The polyisocyanate crosslinker contains two or more isocyanate functional groups that are capable of undergoing chain extension and crosslinking reactions with the film-forming resin composition to form a three-dimensional network structure in the coating.
Examples of polyisocyanate crosslinkers are blocked or unblocked aliphatic, cycloaliphatic or aromatic di-, tri-or polyvalent isocyanates, such as hexamethylene diisocyanate, cyclohexyl 1, 4-diisocyanate and the like. Other non-limiting examples of generally suitable blocked polyisocyanates include isomers of isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, tetramethylxylene diisocyanate, xylylene diisocyanate, and mixtures thereof.
As examples of suitable isocyanate oligomers, polyurethane prepolymers of any of the above-listed polyisocyanate compounds, polyester prepolymers of any of the above-listed polyisocyanate compounds, or polyether prepolymers of any of the above-listed polyisocyanate compounds, and any combination thereof may be used. The polyurethane, polyester or polyether prepolymer may be made by any suitable method known to those of ordinary skill in the art. For example, the polyurethane-type prepolymer can be prepared by: reacting a polyol monomer with one or more of polyisocyanate compounds under suitable conditions; the polyester-type prepolymer or polyether-type prepolymer can be prepared by: the polyester polyol or polyether polyol is reacted with one or more of the polyisocyanate compounds under suitable conditions. Alternatively, as the polyurethane type prepolymer, polyester type prepolymer or polyether type prepolymer, any suitable commercial product may be used.
Preferred polyisocyanate crosslinkers are unblocked or blocked polyisocyanates, more preferably blocked polyisocyanates, even more preferably polymeric.
Polymeric blocked polyisocyanates may be used in certain embodiments. Some examples of suitable polymeric blocked polyisocyanates include biurets or isocyanurates of diisocyanates, trifunctional "trimers," or mixtures thereof. Examples of suitable trimers may include trimers made from an average of three diisocyanate molecules, or trimers made from an average of three moles of a diisocyanate (e.g., HDMI) reacted with one mole of another compound, such as a triol (e.g., trimethylolpropane).
As an example of a polyisocyanate crosslinking agent, any suitable commercially available product can be used, such as DESMODUR N3600 (polymeric blocked polyisocyanate based on Hexamethylene Diisocyanate (HDI) trimer by Bayer).
According to the invention, the amounts of polyisocyanate crosslinker and film-forming resin composition are chosen such that the molar ratio of hydroxyl (OH) groups to isocyanate groups (NCO) in the resulting system varies from 1:1 to 1: 2.5. In general, when the molar ratio of hydroxyl (OH) groups to isocyanate groups (NCO) is less than 1:2.5, then the performance of the resulting two-component coating composition and/or the mechanical properties of the resulting coating may be degraded. When the molar ratio of hydroxyl (OH) groups to isocyanate groups (NCO) is more than 1:1, the curing properties of the resulting coating are poor. According to the actual need, additional inert diluents which do not affect the reactivity of the above film-forming resin composition and polyisocyanate crosslinker can be added during the preparation of the film-forming resin composition and/or polyisocyanate crosslinker, for example to reduce the viscosity of the components. Therefore, the amounts of the film-forming resin composition and the polyisocyanate curing agent are not limited to the above ranges, and can be adjusted as needed.
In the two-component coating composition according to the invention, the film-forming resin composition may also comprise conventional additives which do not adversely affect the two-component coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those agents that improve the processability or manufacturability of the composition, enhance the aesthetics of the composition, improve certain functional properties or characteristics of the coating composition or cured composition resulting therefrom (such as adhesion to a substrate), or reduce cost. Additives that may be included are, for example, fillers, lubricants, film forming aids, wetting agents, plasticizers, defoamers, colorants, antioxidants, flow control agents, thixotropic agents, dispersants, adhesion promoters, thickeners, pH adjusters, solvents, curing catalysts, or combinations thereof. The individual optional ingredients are present in amounts sufficient for their intended purpose, but preferably such amounts do not adversely affect the two-component coating composition or the cured coating resulting therefrom. In a preferred embodiment, the film-forming resin composition may include a catalyst (e.g., a dialkyl tin salt of a fatty acid), a coalescent, a leveling agent, a solvent, or any combination thereof as conventional additives. According to the invention, the total amount of conventional additives is from 0.1% to about 40% by weight relative to the total weight of the film-forming resin composition.
In one embodiment of the invention, the film-forming resin composition comprises, relative to the weight of the film-forming resin composition, from 55 to 90% by weight of a composition comprising a hydroxyacrylic resin according to the invention; 5-20% by weight of a solvent; 5-20 wt% of a film-forming aid; 0-5 wt% of a leveling agent; and 0-5 wt% of a catalyst.
As examples of the film-forming assistant, alcohols such as ethylene glycol, propylene glycol, hexylene glycol, benzyl alcohol and the like; alcohol esters such as lauryl alcohol ester; alcohol ethers such as ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol n-propyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, tripropylene glycol n-butyl ether and the like; alcohol ether esters such as hexylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and the like. As examples of leveling agents, BYK300 and BYK358N, available from bib, germany, can be used.
According to the invention, a two-component coating composition can be prepared by: before application, the film-forming resin composition is simply mixed with the polyisocyanate crosslinking agent in a predetermined weight ratio in a mixing device. The resulting coating composition can be applied using a variety of methods familiar to those skilled in the art, including spraying (e.g., air-assisted, airless or electrostatic spraying), brushing, rolling, flood coating, and dipping. In one embodiment of the present invention, the mixed coating composition is applied by spraying. The coating composition can be applied to various wet film thicknesses. In embodiments of the invention, the wet film thickness preferably provides a dry film thickness of about 13 to about 260 μm, and more preferably about 75 to about 150 μm. The applied coating may be cured by air drying it or by accelerated curing using various drying devices (e.g., ovens) familiar to those skilled in the art.
The two-component coating compositions of the present invention have utility in a variety of applications. Accordingly, embodiments of the present invention also include a coated article comprising a substrate having at least one major surface; and a coating layer coated directly or indirectly on a major surface of the substrate, the coating layer formed from the two-component coating composition of an embodiment of the present invention.
In certain embodiments of the present invention, the two-component coating composition of the present invention may be used in conjunction with a primer, in which case the coated article of the present invention comprises a substrate, a primer layer, and a coating layer formed from the two-component coating composition of the present invention.
In other embodiments of the present invention, the two-component coating composition of the present invention may be applied without a primer, directly on a major surface of a substrate.
Substrates that may benefit from application of the two-component coating composition of the present invention to their surfaces are typically metal substrates, non-limiting examples of which include hot rolled steel, cold rolled steel, hot dip galvanized sheet, electro galvanized sheet, aluminum sheet, tin sheet, various grades of stainless steel, and aluminum-zinc alloy coated steel sheet (e.g., GALVALUME steel sheet or GAL panel).
The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available and can be used directly without further treatment.
Examples
Test method
Adhesion force
The cross-hatch method was used according to GB/T9286-1998 standards, with a rating of 0-5, where 0 is the best and 5 is the worst.
Hardness of pencil
This test is used to measure the hardness of the cured coating. The cured coatings were baked at 60 ℃ for 20 minutes or at 80 ℃ for 30 minutes before evaluation of pencil hardness using GB/T6739-2006, where the coating thickness was 30-40 microns.
Examples
Hereinafter, the present disclosure will be described more specifically by examples. These examples are for illustrative purposes only and are not to be construed as limiting the scope of the invention, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art.
All parts, percentages, and ratios reported in the following examples are on a weight basis unless otherwise stated, and all reagents used in the examples are commercially available and can be used directly without further treatment.
Preparation of a composition comprising a hydroxy acrylic resin
Mixing monomers for preparing the hydroxyl acrylic resin, adding an initiator and a chain transfer agent, and dropwise adding the mixture into a reaction kettle filled with a solvent within 3 hours, wherein the reaction temperature is 100 ℃. After the dripping is finished, the temperature is kept for 1h at 110 ℃, and the mixture is cooled and discharged, thus obtaining the composition containing the hydroxyl acrylic resin with high solid content and low viscosity.
Compositions containing hydroxyacrylic resins of samples 1-3 were prepared according to the procedure as indicated above, using the formulations shown in Table 1, respectively.
Table 1: preparation and Performance characterization of compositions comprising hydroxyacrylic resins
Preparation and Performance testing of two-component coating compositions
The 3 kinds of hydroxyl-containing acrylic resin compositions prepared above and a commercially available hydroxyl-containing acrylic resin (Setalux 27-1550) were formulated into two-component coating compositions in the following proportions.
The raw materials in the formula are uniformly mixed by a dispersion machine to obtain a two-component coating composition, the two-component coating composition is coated on tinplate, the two-component coating composition is baked and dried under the conditions of 60 ℃, 20min and 80 ℃ and 30min respectively, and then the pencil hardness test is carried out according to GB/T6739-2006. Furthermore, the adhesion was tested by cross-hatch according to GB/T9286-1998. The test results are shown in the following table:
table 2: composition of two-component coating composition and test results
As can be seen from the results of tables 1 and 2, the hydroxyacrylic resin composition comprising according to the present invention is high in solid content and low in viscosity by itself, the two-component coating composition formulated after combining with the polyisocyanate crosslinking agent has both high curing rate and high hardness, and the curing rate and hardness of the resulting two-component coating composition are comparable to or even better than those of the two-component coating composition formulated with the conventional commercial hydroxyacrylic resin, and thus can be applied to the fields of heavy machinery coating and the like.
The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, and variations apparent to those skilled in the art are intended to be included within the invention defined by the claims.
In some embodiments, the invention illustratively disclosed herein may be practiced in the absence of any element which is not specifically disclosed herein. While the invention has been described with reference to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the invention as disclosed herein.
Claims (10)
1. A composition comprising a hydroxyacrylic resin, wherein the hydroxyacrylic resin is formed by solution polymerization of a monomer mixture comprising, relative to the total weight of the monomer mixture,
a)1-10 wt% of a multifunctional melamine formaldehyde acrylic resin;
b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate; and
c)45 to 80% by weight of other ethylenically unsaturated monomers other than a) and b);
wherein the composition has a solids content of at least 75 wt% based on the weight of the hydroxyacrylic resin.
2. The composition according to claim 1, characterized in that the viscosity of the composition comprising a hydroxyacrylic resin ranges from 500 to 5000mpa.s, measured at 25 ℃ with a BROOKFIELD viscometer.
3. Composition according to any one of claims 1 or 2, characterized in that the hydroxyl value of the hydroxyacrylic resin is in the range of 30-180mg KOH/g.
4. A composition according to any of claims 1 to 3, characterized in that the multifunctional melamine formaldehyde acrylic resin has a functionality of 3 to 6.
5. Composition according to any one of claims 1 to 4, characterized in that the other ethylenically unsaturated monomers comprise C1-C20 alkyl (meth) acrylates, vinylaromatic compounds having up to 20 carbon atoms and optionally (meth) acrylic acid.
6. The composition according to claim 5, wherein the monomer mixture comprises, relative to the total weight of the monomer mixture,
a)1-10 wt% of a multifunctional melamine formaldehyde acrylic resin;
b) 10-45% by weight of a hydroxy C1-C20 alkyl (meth) acrylate;
c1) 35-60% by weight of a C1-C20 alkyl (meth) acrylate;
c2) 10-50% by weight of (meth) acrylic acid or a vinyl aromatic compound having up to 20 carbon atoms; and
c3) 0-5% by weight of (meth) acrylic acid.
7. The composition according to any one of claims 1 to 6, characterized in that it is prepared by: initiating polymerization of the monomer mixture using an initiator in the presence of a chain transfer agent and a solvent to form the hydroxyacrylic resin-containing composition.
8. Composition according to claim 7, characterized in that the chain transfer agent is selected from one or more of isopropanol, halogenated compounds, linear or branched C2-C22 alkyl mercaptans, mercaptoalkanols, mercaptoalkanoic acids and alkyl mercaptoalkanoates, preferably from one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoethanol and mercaptopropionic acid.
9. A two-component coating composition comprising, in combination,
(i) a film-forming resin composition comprising the hydroxyacrylic resin-containing composition according to any one of claims 1 to 8; and
(ii) a polyisocyanate crosslinking agent.
10. A cured coating obtained from the two-component coating composition of claim 9, which has a pencil hardness of at least 3B, preferably at least 2B after baking at 60 ° for 20 minutes according to GB/T6739-2006.
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| CN114591470A (en) * | 2022-04-13 | 2022-06-07 | 广东华润涂料有限公司 | Waterborne emulsion for woodware, preparation method thereof, coating composition and product |
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