WO1997004881A1

WO1997004881A1 - Polyester oligomer acrylates

Info

Publication number: WO1997004881A1
Application number: PCT/US1996/011832
Authority: WO
Inventors: Michael D. Mcdermott
Original assignee: Henkel Corporation
Priority date: 1995-07-28
Filing date: 1996-07-24
Publication date: 1997-02-13
Also published as: EP0847310A1; AU6547496A; EP0847310A4

Abstract

A compound having the formula: (x(CH2=CR1-C(O)O-)R2-(O-C(O)R3)y-O-C(O)-NH)n-R4, wherein R1 is hydrogen or methyl, R2 is an alkylene group or substituted alkylene group (typically having less than six carbon atoms, more typically two or three carbon atoms), R3 is an alkylene group or substituted alkylene group (typically having less than ten carbon atoms, more typically from four to six carbon atoms), R4 is the residue of an organic isocyanate (including trimerized isocyanates, but excluding isocyanate-functional prepolymers of active hydrogen compounds) having a functionality of n, n is an integer from two to four (typically two or three), x is an integer from one to three, and y is an integer from one to five, is provided. Also provided is a coating composition comprising a compound as set forth above and a method of coating a substrate comprising polymerizing a composition comprised of the compound set forth above while in contact with a substrate. Among the compounds which fall within the above formula are those in which R1 is hydrogen, R2 is an ethylene group, R3 is a pentamethylene group, and R4 is the residue of isophorone di-isocyanate (and n is two), tetramethylxylene di-isocyanate (and n is two), toluene di-isocyanate (and n is two), or trimerized hexamethylene di-isocyanate (and n is three), x is one and y is two.

Description

POLYESTEROLIGOMERACRYLATES

Field of the Invention

The present invention relates to radiation curable polyester oligomers, to polymerizable compositions, and to methods of coating.

Background of the Invention The technology for the production radiation curable coatings using acrylate-functional oligomers is known. The article "Coatings", Encyclopedia of Polymer Science and Engineering, supp. vol., p. 109 and 110 (John Wiley & Sons, Inc. N.Y., N.Y., 1989) notes the most widely used vehicle systems are oligomers substituted with multiple acrylate ester groups mixed with low molecular weight monofunctional, difunctional, or trifunctional acrylate monomers.

U.S. Patent No. 4,522,465 (Bishop, et. al.) discloses buffer-coated and overcoated optical glass fiber in which the topcoat has the high strength and high tensile modulus combined with good elongation and solvent resistance associated with extruded jacket coatings, but which is applied by ordinary coating procedures and cured by exposure to ultraviolet radiation. The coating compositions comprise 30% to about 80% of linear diethylenic polyester polyurethanes which are the linear polyurethane reaction product of an organic diisocyanate with hydroxy-functional polyester formed by reacting a diol, such as ethylene glycol, with certain dicarboxylic acids, such as adipic acid. This polyurethane is end capped with a monoethylenically unsaturated monohydric alcohol, e.g. the hydroxy-functional acrylate of caprolactone dimer derived from caprolactone and 2-hydroxyethyl acrylate supplied by Union Carbide Corporation under the designation Tone M-100.

U. S. Patent No. 4,581 ,407 (Schmid) discloses an essentially isocyanate-free polyurethane polyurea polyethylenic oligomer which is unusually strong and elastic and is thus useful as a binder for a coating containing a magnetic pigment. This oligomer is the reaction product of: (1) organic diisocyanate; (2) a stoichiometric deficiency of difunctional materials reactive therewith and consisting essentially of: (A) polyoxyalkylene glycol having a molecular weight of from 200 to 1000; (B) dihydric bisphenol-based alkylene oxide adduct containing from 2-10 alkylene groups per molecule; and (C) polyoxyalkylene diprimary amine having a molecular weight of from 150 to 800. In all of these, the alkylene groups contain from 2-4 carbon atoms. The polyurethane polyurea so-constituted is capped with monohydric ethylenic compound, such as the adduct of caprolactone dimer and 2-hydroxy ethyl acrylate, to provide a molecular weight in the range of about 5,000 to about 30,000. This polyethylenic oligomer is cured by radiation exposure, such as an electron beam, using from 5% to 25%, based on total polymer solids, of polyethylenic polyhydroxyalkyl melamine.

Summary of the Invention

This invention relates to a compound having the formula:

(_x(CH₂=CR¹-C(O)O-)R²-(O-C(O)R³)_y-O-C(O)-NH)_n-R⁴

wherein:

R is hydrogen or methyl,

R² is an alkylene group or substituted alkylene group (typically having less than six carbon atoms, more typically two or three carbon atoms),

R³ is an alkylene group or substituted alkylene group (typically having less than ten carbon atoms, more typically from four to six carbon atoms),

R⁴ is an aliphatic, aromatic, cycloaliphatic or heterocyclic radical (i.e. the residue of an organic isocyanate, including trimerized isocyanates, but excluding isocyanate-functional prepolymers of active hydrogen compounds) having a functionality of n, n is an integer from two to four (typically two or three), x is an integer from one to three, and y is an integer from one to five.

This invention also relates to a polymerizable composition comprising a compound as set forth above and to a method of coating a substrate comprising polymerizing a composition comprised of the compound set forth above while in contact with a substrate.

Among the compounds which fall within the above formula are those in which R¹ is hydrogen, R² is an ethylene group, R³ is a pentamethylene group, and R⁴ is the residue of isophorone di-isocyanate (and n is two), tetramethylxylene di-isocyanate (and n is two), toluene di-isocyanate (and n is two), or trimerized hexamethylene di-isocyanate (and n is three), x is one and y is two.

Broadly speaking, this oligomer is prepared by forming a mixture of an acrylate- or methacrylate-functional and mono-hydroxyl-functional polyester oligomer and an isocyanate. These two components of the mixture then react in the presence of a urethane catalyst. The resulting product should contain essentially no unreacted isocyanate functionality.

Detailed Description of the Invention The olefinically unsaturated compounds employed for the preparation of the present acrylourethane oligomers may be monomeric or polymeric and are characterized by the presence of a single isocyanate-reactive moiety such as an active hydrogen group. Preferably, the active hydrogen group is hydroxy. Illustrative of unsaturated addition-polymerizable monomeric organic compounds having a single isocyanate-reactive active hydrogen group are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerine dimethacrylate, trimethylol propane dimethacrylate, reaction products of polyether glycols of acrylic or methacrylic acid and the like. The preferred olefinically unsaturated compounds are lactone-modified acrylate or methacrylate acid esters (hereinafter "lactone-acrylate adducts") prepared by reacting an appropriate lactone with an acrylate or methacrylate acid ester.

Lactones employed in the preparation of the lactone-acrylate adducts typically have the formula:

0-CH(R)-(CR₂)_z-C=0

wherein R is hydrogen or an alkyl group having from 1 to 12 carbon atoms, z is from 4 to 7 and at least (z - 2) of the R's is hydrogen. Preferred lactones are the epsilon-caprolactones wherein z is 4 and at least 6 of the R's are hydrogen with the remainder, if any, being alkyl groups. Preferably, none of the substituents contain more than 12 carbon atoms and the total number of carbon atoms in these substituents on the lactone ring does not exceed 12. Unsubstituted epsilon-caprolactone, i.e., where each R is hydrogen, is a derivative of 6-hydroxyhexanoic acid. Both the unsubstituted and substituted epsilon-caprolactones are available by reacting the corresponding cyclohexanone with an oxidizing agent such as peracetic acid.

Substituted epsilon-caprolactones found to be most suitable for preparing the present lactone-acrylate adducts are the various epsilon-monoalkylcaprolactones wherein the alkyl groups contain from 1 to 12 carbon atoms, e.g., epsilon-methyl-caprolactone, epsilon-ethyl-caprolactone, epsilon-propyl-caprolactone and epsilon-dodecyl-caprolactone. Useful also are the epsilon-dialkylcaprolactones in which the two alkyl groups are substituted on the same or different carbon atoms, but not both on the omega carbon atoms. Also useful are the epsilon-trialkylcaprolactones wherein 2 or 3 carbon atoms in the lactone ring are substituted provided, though, that the omega carbon atom is not di-substituted. The most preferred lactone starting reactant is the epsilon-caprolactone wherein z in the lactone formula is 4 and each R is hydrogen.

The acrylate or methacrylate acid esters utilized to prepare the lactone-acrylate adducts contain from 1 to 3 acrylyl or alpha-substituted acrylyl groups and one or two hydroxyl groups. Such esters are commercially available and/or can be readily synthesized. Commercially available esters include the hydroxyalkyl acrylates or hydroxyalkyl methacrylates wherein the alkyl group contains from 2 to 10 carbon atoms, preferably from 2 to 6 carbon atoms. The hydroxyalkyl acrylates and methacrylates have the following formula:

CH₂=CR¹-C(O)O-R²-OH

wherein R¹ is hydrogen or methyl and R² is a linear or a branched alkylene group having from 2 to 10 carbon atoms, preferably from 2 to 6 carbon atoms.

Examples of suitable hydroxyalkyl acrylates and methacrylates include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxypentyl acrylate, 6-hydroxynonyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-hydroxypentyl methacrylate, 5-hydroxypentyl methacrylate, 7-hydroxy heptyl methacrylate and 5-hydroxydecyl methacrylate.

Preferred lactone-acrylate adducts have the formula: CH₂=CR¹-C(O)O-R²-(O-C(O)R³)₂-OH wherein R\ R², and R³ are as described above.

The lactone-acrylate adduct is prepared by reacting the lactone with the hydroxyalkyl acrylate in the presence of less than about 200 parts per million of a catalyst. The catalysts which may be used include one or more organometallic compounds and other metallic compounds such as stannic chloride or ferric chloride and other Lewis or protonic acids. Preferred catalysts include stannous octoate, dibutyltin dilaurate, and other tin compounds; titanates such as tetraisopropyl titanate and butyl titanate; and the like.

The reaction is carried out at a temperature of from about 100°C to about 400°C, preferably from about 120°C to about 130°C. The reaction may be carried out at atmospheric pressure, although higher or lower pressures may be used. The reaction is generally carried out in the presence of oxygen to inhibit polymerization of the hydroxyalkyl acrylate. The reaction is generally carried out for a period of from about 2 to about 20 hours. The reaction is carried out in the presence of a suitable inhibitor to prevent polymerization of the hydroxyalkyl acrylate double bond. These inhibitors include the monomethyl ether of hydroquinone, benzoquinone, phenothiazine, methyl hydroquinone, 2,5-di-t-butylquinone, hydroquinone, benzoquinone and other common free radical inhibitors known in the art. The level of inhibitor used is less than 1000 parts per million, preferably less than 800 parts per million, and most preferably, less than 600 parts per million. A molar ratio of the lactone to hydroxyl groups in the ester of from about 1 :0.1 to about 1 :5, preferably from about 1 :0.3 to about 1:3 is typically utilized.

An example of a lactone-acrylate adduct preferred for use in the present invention is a caprolactone-2-hydroxyethyl acrylate adduct supplied by Union Carbide Corporation under the tradename TONE M-100, which has the formula CH₂=CH-C(O)O-CH₂-CH₂-(O-C(O)(CH₂)₅)₂-OH.

A polyfunctional aromatic and aliphatic isocyanate is reacted with the lactone-acrylate adduct to introduce the isocyanate residue into the compound. The R⁴ is thus an aliphatic, aromatic, cycloaliphatic or heterocyclic radical. Typically, R⁴ will contain from about 6 to about 36 carbon atoms, more typically from about 7 to about 24 carbon atoms. R⁴ will typically be a hydrocarbon group or a heterocyclic group and is typically essentially free of urethane groups.

Suitable polyfunctional isocyanates preferably contain on average 2 to at most 4 NCO groups. Examples of suitable isocyanates are 1 ,5-naphthalene di- isocyanate, 4,4'-diphenyl methane di-isocyanate (MDI), hydrogenated MDI (H12MDI), xylylene di-isocyanate (XDI), tetramethyl xylylene di-isocyanate (TMXDI), 4,4'-diphenyl dimethyl methane di-isocyanate, di- and tetraalkyl diphenyl methane di-isocyanate, 4,4 -dibenzyl di-isocyanate, 1 ,3-phenylene di¬ isocyanate, 1 ,4-phenylene di-isocyanate, the isomers of tolylene di-isocyanate (TDI), optionally in admixture, 1-methyl-2,4-di-isocyanatocyclohexane, 1 ,6-di- isocyanato-2,2,4-trimethyl hexane, 1 ,6-di-isocyanato-2,4,4-trimethyl hexane, 1- isocyanatomethyl-3-isocyanato-1 ,5,5-trimethyl cyclohexane (IPDI), chlorinated and brominated di-isocyanates, phosphorus-containing di-isocyanates, 4,4'-di- isocyanatophenyl perfluoroethane, tetramethoxybutane-1 ,4-di-isocyanate, 1 ,4- butane di-isocyanate, 1,6-hexane di-isocyanate (HDI), dicyclohexyl methane di¬ isocyanate, cyclohexane-1 ,4-di-isocyanate, ethylene di-isocyanate, phthalic acid bis-isocyanatoethyl ester; polyisocyanates containing reactive halogen atoms, such as 1-chloromethylphenyl-2,4-di-isocyanate, 1-bromomethylphenyl-2,6-di- isocyanate, 3,3-bis-chloromethylether-4,4'-diphenyl di-isocyanate. Sulfur- containing polyisocyanates are obtained, for example, by reaction of 2 mol hexamethylene di-isocyanate with 1 mol thiodiglycol or dihydroxydihexyl sulfide. Other di-isocyanates are trimethyl hexamethylene di-isocyanate, 1 ,4-di- isocyanatobutane, 1 ,2-di-isocyanatododecane and dimer fatty acid di-isocyanate. Tri-isocyanate isocyanurates can be prepared by trimerizing di-isocyanates at elevated temperatures, e.g. at about 200°C and/or in the presence of a catalyst such as an amine, metal alkyl, or carboxylate zwitterion. For reaction with the isocyanate, the lactone-acrylate adduct is typically heated to a temperature of about from 40 to 100°C and typically about 60°C. At this time, a catalytic amount of a urethane catalyst, e.g. dibutyl tin dilaurate, is added followed by addition of an isocyanate compound the formula:

R⁴- (NCO)_n in which R' is as defined and n is typically 2 to 4, at a rate which maintains the desired reaction temperature. The amount of the isocyanate will be essentially equal (e.g. 1.01 :1 to 1 :1.01), on an equivalents basis, to the hydroxyl equivalents of the lactone-acrylate adduct.

When the addition is complete, the reaction is typically heated, e.g. to a temperaure of about 80°C to about 100 °C, and held for about from 2 to about 4 hours or until the NCO content is <0.5% by weight as measured for example by titration with dibutyl amine. Thereafter, the product is cooled prior to storage. The reaction with the isocyanate is entirely conventional being usually carried out at moderate temperature in the presence of a catalyst which promotes the urethane-forming reaction, such as dibutyl tin dilaurate. It is customary to limit the temperature, at least during the initial stages of the reaction, to about 60°C, and this can be done by slowing the rate of addition of one ofthe components. The temperature may be raised in the later stages ofthe reaction to promote completion of the reaction as measured by the consumption of the isocyanate functionality. The order of reaction is largely immaterial, it being possible to bring in the monohydric ethylenic compound either at the beginning, during the middle of the procedure, or as the last reactant. All of these variations are known in the art. It is usual herein to employ the di-isocyanate and the materials reactive therewith in stoichiometric amounts and to continue the reaction until the isocyanate functionality is substantially undetectable. As will be understood, these reactions are conveniently carried out neat with reactants that are liquid at the reaction temperature or in solvent solution, this being illustrated using the preferred tetrahydrofuran to maintain the liquid condition as the reaction proceeds.

The compound of the present invention can be applied to a variety of substrates. These include, for example, porous stock such as paper and cardboard, wood and wood products, metals such as aluminum, copper, steel, and plastics such as P.V.C, polycarbonates, acrylic and the like. After addition of a suitable photoinitiator, e.g., PHOTOMER 51 ® brand photoinitiator (benzyl dimethyl ketal), the compound is applied by methods such as spraying, rollcoating, flexo and gravure processes onto a selected substrate. The resulting coated substrate, e.g., a paper, is typically cured under a UV or electron beam radiation. The compound may optionally be mixed with other substances such as pigments, resins, monomers and additives such as anti-oxidants and rheological modifiers.

In order to further illustrate the practice of this invention, the following examples are included.

Example 1 Isophorone di-isocyanate in an amount of 24.42 parts by weight (0.219 equivalents) is mixed with 0.9 parts by weight of butylated hydroxy toluene and heated to 60°C with a dry air sparge. After heating to 60°C, heating is discontinued and a catalytic amount (0.04 parts by weight) of dibutyl tin dilaurate is then added. Caprolactone-2-hydroxyethyl acrylate adduct supplied by Union Carbide Corporation under the tradename TONE M-100, is added to the reaction mixture in small increments, the total amount of adduct being 75.46 parts by weight (0.219 equivalents). The rate of addition is such that the reaction temperature is maintained at about 60°C. After adduct addition is complete and the exotherm has subsided, the reaction temperature is raised to and held at about 90°C for 2 to 4 hours. The reaction is allowed to continue until no NCO groups are detectable by Fourier Transform Infra-red spectroscopy, i.e. less than 0.1% by weight NCO groups. The compound should exhibit a viscosity of 6,500 to 7,500 cps and should appear as a transparent, water-white liquid. When a suitable photoinitiator is added, the compound is drawn down on paper to effect a 1 mil dry film thickness and photocured.

Example 2

Trimerized hexamethylene di-isocyanate (available as Desmodur N-3300, Miles, Inc.) in an amount of 36.01 parts by weight (0.185 equivalents) is mixed with 0.9 parts by weight of butylated hydroxy toluene and heated to 60°C with a dry air sparge. After heating to 60°C, heating is discontinued and a catalytic amount (0.04 parts by weight) of dibutyl tin dilaurate is then added. Caprolactone-2-hydroxyethyl acrylate adduct supplied by Union Carbide Corporation under the tradename TONE M-100, is added to the reaction mixture in small increments, the total amount of adduct being 63.86 parts by weight (0.185 equivalents). The rate of addition is such that the reaction temperature is maintained at about 60°C. After adduct addition is complete and the exotherm has subsided, the reaction temperature is raised to and held at about 90°C for 2 to 4 hours. The reaction is allowed to continue until no NCO groups are detectable by Fourier Transform Infra-red spectroscopy, i.e. less than 0.1% by weight NCO groups. The compound should exhibit a viscosity of 30,000 to 34,000 cps and should appear as a transparent, water-white liquid. When a suitable photoinitiator is added, the compound is drawn down on paper to effect a 1 mil dry film thickness and photocured.

Claims

WHAT IS CLAIMED IS:

1. A compound having the formula:

(_x(CH₂=CR¹-C(O)O-)R²-(O-C(O)R³)_y-O-C(O)-NH)_n-R⁴

wherein: R is hydrogen or methyl,

R² is an alkylene group or substituted alkylene group, R³ is an alkylene group or substituted alkylene group,

R⁴ is an aliphatic, aromatic, cycloaliphatic or heterocyclic radical having a functionality of n, n is an integer from two to four, x is an integer from one to three, and y is an integer from one to five.

2. A compound according to claim 1 wherein R⁴ is essentially free of urethane groups.

3. A compound according to claim 1 wherein R⁴ is a hydrocarbon radical or a heterocyclic radical.

4. A compound according to claim 1 wherein R⁴ has from about 6 to about 36 carbon atoms.

5. A compound according to claim 1 wherein R⁴ has from about 7 to about 24 carbon atoms.

6. A compound according to claim 1 wherein R⁴ is the residue of isophorone di¬ isocyanate, tetramethylxylene di-isocyanate, toluene di-isocyanate, or trimerized hexamethylene di-isocyanate.

7. A compound according to claim 1 wherein n is two or three.

8. A compound according to claim 1 wherein R³ is an alkylene group having less than ten carbon atoms.

9. A compound according to claim 1 wherein R³ is an alkylene group having from four to six carbon atoms.

10. A compound according to claim 1 wherein R³ is an alkylene group having five carbon atoms.

11. A compound according to claim 1 wherein R² is an alkylene group having less than six carbon atoms.

12. A compound according to claim 1 wherein R² is an alkylene group having two or three carbon atoms.

13. A compound according to claim 1 wherein R² is an alkylene group having two carbon atoms.

14. A compound according to claim 1 wherein x is one.

15. A compound according to claim 1 wherein y is from two to four.

16. A compound according to claim 1 wherein y is two.

17. A compound according to claim 1 wherein R¹ is hydrogen.

18. A compound according to claim 1 wherein R¹ is hydrogen, R² is an ethylene group, R³ is a pentamethylene group, x is one, and y is 2.

19. A compound according to claim 18 wherein R⁴ is the residue of isophorone di-isocyanate.

20. A compound according to claim 18 wherein R⁴ is the residue of trimerized hexamethylene di-isocyanate.

21. A compound having the formula:

(_x(CH₂=CR¹-C(O)O-)R²-(O-C(O)R³)_y-O-C(O)-NH)_n-R⁴

wherein: R¹ is methyl,

R² is an alkylene group having less than six carbon atoms, R³ is an alkylene group having less than ten carbon atoms, R⁴ is a hydrocarbon radical or a heterocyclic radical having from about 6 to about 36 carbon atoms and a functionality of n, n is two or three, x is one, and y is two

22. A compound according to claim 21 wherein R² has two or three carbon atoms and R³ has from four to six carbon atoms.

23. A compound according to claim 22 wherein R² has two carbon atoms, R³ has five carbon atoms.

24. A compound according to claim 23 wherein R⁴ has from 7 to 24 carbon atoms.

25. A polymerizable composition comprising a compound of claim 1 and a member selected from the group consisting of pigments, resins, and mono-ethylenic monomers.

26. A method of coating a substrate comprising polymerizing a composition comprised of a compound according to claim 1 while said composition is in contact with a substrate.