CA1073593A

CA1073593A - Composition containing a monoethylenically unsaturated adduct and one of a polyisocyanate, polycarboxylic polyanhydride or polyepoxide

Info

Publication number: CA1073593A
Application number: CA261,597A
Authority: CA
Inventors: Marvin L. Kaufman
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1975-09-30
Filing date: 1976-09-20
Publication date: 1980-03-11
Also published as: BR7606527A; FR2326456B1; DE2643701A1; AU1776776A; JPS5242531A; ZA765647B; PT65614A; CH603772A5; FR2326456A1; IT1192128B; JPS6031228B2; NZ182003A; BE846643A; ES451960A1; NL7610755A; DK437476A; GB1564296A; GB1566114A; NL7610754A; CA1074046A

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention as disclosed provides a radiation curable coating composition comprising the addition reaction product of (i) a monoethylenically unsaturated adduct of a monoethylenically unsaturated carboxylic acid or a hydroxyalkyl ester thereof with an anhydride containing at least 3 carbon atoms and selected from monepoxides, lactones and mixtures thereof, said adduct containing an average of at least 1 mole of anhydride per mole of hydroxyester and an average of at least 2 moles of anhydride per mole of acid moiety, with (ii) an organic compound containing a plurality of groups capable of reacting with active hydrogen. The organic compound (ii) includes those (such as polyisocyanates) which form a urethane linkage, those (such as polycarboxylic polyanhydrides) which form an ester linkage, or those (such as polyexpoxides) which form an ether linkage.

Description

~ 3~j9~

The present invention relat~s to coatlng composltlons and more particularly to radlation curable coating composltlons.
Coatlng compositions normally contain a vehicle in addition to the actual film-forming resins. This vehlcle, which ls present only to assist the application of the film-forming resins, has to be removed usually by the application o~ heat. Thls ls energy-consuming and may also lead to atmospheric pollutlon i~
the solvent vapor~ are not recovered. The solvent ltself may be lost and this can represent an economic disadvantage. Emulsion type composltions ln which the film-~orming resln is suspended as a flne di~perslon ln water have been used in an attempt to avoid the use of solvents but again, the water has to be removed, usually by the use of heat, and this is even more energy-consuming than the remo~al o~ volatile hydrocarbon solvent because of the relatively hlgh boiling point and latent heat o~ vaporization of the water.
We have now found that extremely satlsfactory radiatlon curable coating compositions can be made using the reactlon products of (1) certain carboxyllc acld adducts with (il) compounds contalnlng a plurality of groups capable of reacting wlth actlve hydrogens.

The present invention, therefore, resides in a radiation curable coating composition comprising the addition reaction product of (i) a monoethylenically unsaturated adduct of a monoethylenically unsaturated carboxylic acid or hydroxyalkyl ester thereof with an anhydride containing at least 3 carbon atoms and selected from monoepoxides, lactones, and mixtures thereof, said adduct containing an average of at least l mole of anhydride per mole of hydroxyester and an average of at least 2 moles of anhydride per mole of acid moiety, with (ii) an organic compound containing a plurality of groups capable -of reacting with active hydrogen, said organic compound being a polyisocyanate, polycarboxylic polyanhydride or polyepoxide.
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~ he composltions can be cured by radiation (preferably ultra-vlolet or electron beam) and form good coatings. .i photo-sensitizer may be present when an ultra-violet cure is used although lt is not necessary when an electron beam cure is employed.
The adduct is an adduct of a monoethylenically un-saturated acid or its hydroxyalkyl ester and an anhydride (epoxide or lactone). In preparing the adduct, the monoethylenlcally unsaturated carboxylic acid or its hydroxyalkyl derivative is reacted wlth an appropriate proportion of an anhydride of a dihydrlc la-, 1~3~j.9;3 alcohol or an hydr xy acid ti.e. a monoepoxide or a lactone) containlng at leas' three carbon atoms. These are partlcularly illustrated by 1,2-propylene oxide, which ~s the anhydride of 1,2-propylene diol, or by epsilon-caprolactone, which is the anhydride of the corresponding hydroxy acid. The use of other similar anhydrides will be discussed below.
Preferably a hydroxyaIkyl est~r of the mcnoethylenically unsaturated carboxylic acld is reacted (adducted) wlth at least 1 mole of the monoepoxide or lactone. The reaction is preferably carried out in the presence o~ a Lewis acid catalyst, such as BF3 etherate or stannic chloride, and at a typical temperature of 30 to 70C.
Under these conditions, an ether or ester forms, the a~erage number of added groups corresponding to the number of moles of monoepoxide or lactone employed. In order to produce a product whlch wlll be reactlve in the coatlngs, the unsaturatlon must be malntained and thls llmits the temperature of the reaction which is exothermic.
By slow addition of the monoepoxide or lactone, and in the presence of inhibitors, higher temperatures up to 120C. may be used, but practical operation suggests an upper llmlt of 80C.
Very low temperatures are useful, but the reaction slows with decreasing temperature. In the same way, the adduction reaction can be carried out with the mon oe thylenically unsaturated acid itself, but in this case at least 2 moles of the monoepoxide or lactone must be used for each mole of acld. The monoe~oxide reactant or the lactone reactant can be constituted by a mi~ture of monoepo~ides, a mlxture of lactones, or a mixture of the two.
It is preferred to react at least 3 moles of the mon oepoxide and~or la~'one with the mon oe thylenically unsaturated carboxylic B-lOt~3~9..~

acid or its hydroxyalkyl ester because this maximizes water resistance and ultraviolet sensitivity. It also significantly reduces volatility and toxicity. The polyethers provide the best ultraviolet sensitivity, and are preferred.
There is normally little purpose served by using more than 10 moles of the monoepoxide and/or lactone on the basis noted above, but so long as the reaction is substantlally complete or if unreacted monoepoxide or lactone is removed, the product will be useful.
Various monoepoxides may be used herein, such as propylene oxide, butylene oxide, butyl glycidyl ether, phenyl glycldyl ether, cyclohexene oxide, and the llke. The oxirane group i8 preferably carried by an aliphatic group. While other functionallty whlch ls lnert under the conditions of reactlon may be present, such as the halogen group as in epichlorohydrin, lt is usually preferred that a single 1,2-epoxide group be the 801e functional group present. Propylene oxide is the preferred monoepoxide. Whlle the 1,2-epoxlde group is preferred, thls is not essential and tetrahydrofuran and 1,3-dioxolane are fully useful to illustrate this. In some instances, and to provide polyacrylates directly, glycidyl acrylate may be used, particularly to~ether with a conventlonal monoepoxlde such as propylene oxide.
While ethylene oxide produces undesired water solubility when used alone, it is possible to have some of it present herein where other agents overcome or minimize the problem o~ water sensitivity.
Various lactones may be used, such as butyrolactone or caprolactone. Epsilon caprolactone is the preferred lactone.
When the acid itself is used (as distinct from the hydroxyalkyl .

1073~9~3 ester), the lactone is not reacted with the unsaturated acld in the abse~ce of an epoxide since hydroxy functlonal derivatives are desired.
Ihe mDnoethylenically unsaturat~ carbcxylic add is preferably acrylic acid, but other slmilar acids, such as methacryllc acld, and crotonlc acid are also useful. The acld is preferably monocarboxylic~ but polycarboxylic aclds may be used, such as ltaconlc acld or fumarlc acld. Monobutyl maleate and monohydro~y-propyl,maleate will further lllustrate use~ul monoethylenically unsaturated carboxylic acids.
Ihese sr~noe ~ylenically ~sa~rat~d acids can ~e used as such, or they can be employed ln the form of hydroxy alkyl ester3 in which the alkyl group preferably contains ~rom 2 to 4 carbon atoms.
These esters are typlfled by hydroxyethyl acrylate. The mono-functional acids noted before and their hydro2y esters provide mono~unctional adducts.
The adduct ls reacted with a compound which contains a plurality of groups which are reacti~e wlth active hydrogens.
Such reactive groups lnclude isocyanate (~orms a urethane linkage), carboxylic acid anhydrlde (forms an ester llnkage), or epoxide (~or,ms an ether llnkage). Suitable compounds for reactlon with the adduct therefore lnclude polyisocyanates e.g.dllsocyanates such a~ tolylene diisocyanate, polyanhydrides e.g. dianhydrides such as benzophenone tetracarboxylic acld dianhydride, styrene~
maleic anhydride copolymers or ethylene/malelc anhydrlde copolymers especlally low molecular welght styrene/maleic anhydrlde copolymers, polyepoxldes e.g. Epon 828 (trade mark), dimethyl dichlorosllane, methyl trichlorosilane.
.

~' lO~S9;1 The reactive compound is reacted with the adduct in amounts up to the stoichiometric requirement. More of the compound may be used but since it will not take part in the reaction, this will not be economically favored.
The selection of benzophenone-tetracarboxylic acid dlanhydrlde is particularly preferred since this leads directly to ultraviolet curable reaction products, especially polyacrylates, whlch are lnternally sensitized to ultraviolet light. This permits omission of photo~ensitizers such as benzophenone. For an electron beam cure there is no need of a photosensitiser.
The reactlon of the adducts with the organic-poly-isocyanates or the polycarboxylic acid polyanhydrides or other compounds is a slmple addition reaction which proceeds at moderate temperature (20C. - 100C., preferably 50CC. - 80C.).
The unsaturatlon is not destroyed in this reaction so that a compound wlth polyethylenic unsaturation ls produced.
It should be observed that the reactlon product o~

2 moles of hydroxyethyl acrylate and 1 mole of toluene diisocy-anate is a solid. Replacing the hydroxyethyl acrylate with the 5 mole propylene oxide adduct thereof produces a liquid diacrylate, and the liquid form is much more attractive, since it can be used wlthout solvents. Also, the final cured products are less brittle.
By virtue of the polyether or polyester structure of the adduct, the compo~itions have lowered volatlllty, reduced toxicity, are easily handled and cure excellently. Particularly where the polyether structure is present, amine cosensitizers are not needed, and while they wlll still benefit the cure some-what, the amines create yellowing or extraction problems, and 10'~3.~

their omission can be important in certain instances.
The polyethylenically unsaturated derivatives of the adduct can be used alone, or they can be combined with other ethyleni-cally unsaturated monomers and polymers to provide radiation curable systems which are particularly useful for coating.
Other ethylenically unsaturated materials which may be used are illustrated by styrene, acrylonitrile, the polyacrylates such as butylene glycol diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, epoxy polyacrylates (both di- and tetraacrylates) and maleic polyesters.
Radiation curable coatings are also described and claimed in related copending Canadian Patent Application No. 261,598 of Kaufman, filed September 20, 1976. m e coatings therein described comprise a monoethylenically unsaturated adduct of a monoethylenically unsaturated carboxylic acid or hydroxyalkyl ester thereof with an anhydride containing at least 3 carbon atoms and selected from the group consisting of monoepoxides, lactones, and mixtures thereof, said adduct containing an average of at least 1 mole of said anhydricle per mole of said hydroxy ester or an average of at least 2 moles of said anhydride per mole of ~aid acid, said monoethylenically unsaturated adduct being in admixture with a polyacrylate providing a plurality of ethylenically unsaturated acrylic acid ester groups.
The present invention is illustrated in the Examples which follow. Examples 1 to 7 and 16 illustrate the preparation of the adducts. Examples 8 to 12 illustrate the preparation and use of the reaction products and Examples 13 to 15 illustrate coatings containing the products. ; -- . . ~ . .. . -. ..

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Example l Charge a dry reaction vessel fitted with a stirrer, thermometer, condenser, drying tube and two additional funnels with 928g hydroxyethyl acrylate (8.o moles). Add enough boron-trifluoride etherate to initiate the-reaction, approximately 1 ml.
Then, with suitable cooling, add 2320g propylene oxide (40.0 moles) and additional BF3 etherate (15-20 ml.) at such a rate 80 as to maintain react~on temperature at 50~C. Total ~ddition time i8 2-2.5 hours. Maintain the temperature as high as pos-sible by decreasing cooling. When the temperature drops to about 40C., sample the reaction for gas chromatography. When gas chromatography shows no propylene oxide, add 0.32g hydro-qu~none (lO0 parts per million) and 2 ml. triethylamine to stabilize the product. The product is a clear, light yellow ~5 liquid of 35-40 centipoise viscosity. A complete gas chroma-tography analysis indicates the product is a mixture of hydroxy-ethyl acrylate (~u2%) and adducts thereof having the formula shown below in which x ranges from 1 to about lO, and has an ~ average value of 5. NMR analysis of the products shows the j 20 correct ratlo oi vinyl protons to the remaining types of pro-¦ tons and lnfrared analysis shows the presence ce hydroxyl, acrylate unsaturation and ether bands, all consistent with the I following structure:
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CH2= C-C OCH2CH2-O ~CH-CH2-~0~ XH AV1--05 .

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Ex~ple 2 Following the procedure of Example 1, except using 10 moles of propyl~ne oxide to 1 mole of hydrox~ethyl acrylate, the product is a li~ht colored liquid of 70-75 centipoise vi~cosity ~ith the st~ucture noted in Exa~ple 1, but with x .
averaging 10.
Example 3 Following the procedure of Fxample L, except using 6 moles of propylene oxide to 1 mole of acrylic acid, the product ha~ the structure noted below:

x=6 (average) Example 4 .
Following the procedure of Example l, except using

3 moles of butylglycidyl ether to l mole of hydroxyethyl acrylate yields an adduct having an average of three butylglycidyl ether groups per molecule of hydroxyethyl acrylate.
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Example 5 Following the procedure o~ Example 1, eXcept using ~our moles o~ propylene oxide and 1 mole of phenyl glycidyl ether to 1 le of hydroxyethyl acrylate yields an adduct having an average of 4 propylene oxide group~ and 1 phenyl glycidyl ether group per molecule of hydroxyethyl acrylate.

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Example 6 Following the procedure of Example 1, except using'

4 ~oles of propylene oxide and 1 mole of tetrahydrofuran to 1 mole of hydroxyethyl acrylate yields an adduct having an average of 4 propylene oxide groups and l tetrahydrofur~n group per mo~ecule of hydroxyethyl acrylate.

.
Example 7 ':
Followi~g the procedure of Example 1, except using 4 moles of propylene oxide and t mole o epsilon-capro~actone to ~0 1 mole of hydroxyethyl acrylate yields an adduct having an a~erage of 4 propylene oxide groups a~d 1 caprolactone group per molecule of hydroxyethyl acrylate.
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Example 8 ,;'' ' To 406 grams of the hydroxy~ethyl acrylate-propylene oxide adduct produced in Example l,are added 28.7 grams o the commercial 80l20 i~omeric mixture o~ toluene diisocyanates, 0.17 gra~
hydroquinone and 3 drops dibutyl tin dilau~at,e catalyst. The ' reaction mixture is heated at 60-65C. for about 2 hours after which the infrared spectrum show~ complete reaction of the ' ~socyanate. The product is a l~w viscosity li~uit ~(Gardner-Holdt ~G! (165 centipoise)] containing a mixture of a diacrylate resin li and unreacted monoacrylate monomer. The ~tructure of ~he i diacrylate resin i8 shown below:
: CH3 H 0 . ~ ~-C-HEA.5P0 , ~ N-C-HEA.5P0 HEA identifies hydroxyethyl acrylate P0 identifies propylene oxide.

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~ 10~3~3 Example 9 To 406 grams of the hydroxyethyl acrylate-propylene oxide additian product o~ Example 1 are added 40.3 grams benzophenone-tetracarboxylic dianhydride, 2.2 grams triethyl amine, and 0.178 grams hydroquinone. The reaction mixture is heated ~t 70C. for 3-4 hours after which the in~rared spectrum shGws no anhydride re-maining. At thls point the reae~ion mixture consists o~ a diiu~c-t~onal acrylate resin and a mono~unctional acrylate moncmer of low ~is~osity ~(Gardner-Holdt = J (250 centipoise)~. The structure o~ ~he diacrylate 18 shown below:

5 ~ ,0 ~ - EA. 5'0 _ EEA identiiies hydroxyèthyl acrylate P0 ident~ies pro~ylene oxide.
The benzophenonetetracarboxylic dia~hydride, as will be ~hown.hereina~ter, pro~ides photosensit~e characteristics, rendering the product intrinsically sensiti~e to ul~ra~lolet light in the ab-sence cr any addition~ photosensitizer.
Example 10 Slmple coating ~ormulations based on the products described in the prev~ous examples, pentaerythritol triacrylate and a photosensitizer, were drawn down on metal panels using a ~3 wire wound rod. Ihe coatlngs were cured by ~ osure to 2 x 200 watt/l~ch medium pressure mercury lamps at aspeed of 2~ fe~ per minute ln air. The compositions and surface characteristics of the coatings are shown in Table I which also shows how much of the film remains arter baking 5 minutes at 350 F. ~ :

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Pentaerythritol Hydroxypolyoxyalkylene Film Triacrylate Acrylate: ,Sensitizer Surface Yield % % (note 1) Tack %
HEA.5P0 63% - 7% Tack Free 85 28 HEA.4PO.lC1 65% 7% Tack Free 77 27 HEA.4PO.lPGE 66% . 7% Tack Free 88 26 HEA.3BGE 67%, 7% Slight Tack 82 , HEA.4PO.lT,HF 63% . 77O Tack Free 85 ~ote 1 The sensitizer i~ a weight ratio mixture of S parts benzophenone to 2 parts methyldiethanol amine HEA identified hydroxyethyl acrylate P0 identified propylene oxide L5 PGE identifies phenyl glycidyl ether . . ' , Cl identifies caprolactone(epsilon) .
~, BGE identifies butyl glycidyl ether THF identifies.tetrahydrofuran ' Example 11 '' 20:. ,.' ,' , T~i9 ,example describes a unique advantage,when using the.
products of thi~ invent~on. For example, in Table I above, t~ë
I sensitizer is shown to be a combination of benzophenone (5 parts) ' ¦ and methyldiethanol amine (2 parts). It is also possible to use benzophenone alone without the methyldiethanol amine cosen~itizer.
2a A formulation identical to that in Table I with HEA.4PO.lPGE without . methyldiethanol amine cured to a yield of 87% vs. 88% with methyl-. diethanol amine present. Thu5, the products o~ this invention surprisingly cure well in the absence of amine sensitizers which are usuall~ needed for a good ultraviolet cure in an air atmosphere.

1 .

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Example 12 In the previous example, the products of this inven-tion were used without resins, but it is also possible to use these in admixture with other resinous materials, including other radiation curable materials. The formulating latitudes available are illustrated in Table II be~ow. These materials were appl~ed and cured under the conditions set forth in Example 10.
Table II
Trimethylol Sensitizer Polymer Propane HEA.5P0 Note 1 o~ Sur~ace Yield Type % Trlacrylate ~ % Table I Tack _ %
A-Urethane 21~ 21% 51% 7% Slight 89 B-Urethane 21~ 21% 51% 7% Tacky 87 C-Urethane 21% 21% 51~ 7% Slight 88 D-Urethane 21~ 21% 51% 7~ Slight 90 E-Epoxyacrylate 23% 21% 49% 7~ Tac~ Free 88 A = Polycapr~lactone Diol-Toluene Diisocyanate-Diacrylate B = Dimer Acid Diisocyanate-Diacrylate C 5 Polyether Diol-Toluene Di~socyanate-Diacrylate D - Isophoronedii~ocyanate-Diac~Ylate E = Epon 828-Diacrylate Example 13 To the composition of Example 8 (30 grams) was added 5 3 grams tr~methylolpropane triacrylate, 1.8 gram benzo-`~ phenone and 0.74 gram methyldiethanol amine. The coatlng was j drawn down on aluminum panels with #3 wire wound r~d and cured 1 by paaslng the coated panel at 25 feet per m~nute under 2 x 200 watt/inch medium pressure mercury lamps. The coating cured to a hard, tack free, mar resistant surface with a yield o~ 90+%
after baking 5 minutes at 350F.

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10~3S

. ~ Exam~le 14 ~ o the composition of Example g (30 grams) was added 5.3 grams trimethylolpropane triacrylate, 1.8 gram benzo-phenone, and 0.74 gram methyldiethanol amine. The coating was cured as in Example 13 above. The coating cured to a hard, : tack free, mar resistant surface, with an a~ter-bake yield of . ` 77Z.
Example 15 . To the composition of Example 4 (20 grams) was added 6.7 grams.pentaerythritol triacrylate. The coating wa~
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cused a~ ~n Example ~3 above. The coating cured to a tack free, . mar re8istant surface with an after-bake yield of 76%. This . example il~ustrates a unique property, namely, that a photo-sénsitizer can bé incorporated into the resin component, . . . .
. 15 thereby rendering it completely reactive. That is, it cannot be extracted from the cured composition because it is an integral part of this coating~
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Example 16 ~ . . Follow~ng the procedure of Example.l, except i . using 4 moles of propylene oxide and 1 mole of glycidyl ac~yl~t~ to 1 mola of acryl-c.~.id, ~h~ produc~ uas a' . . .
liquid containing an average of 4 propylene ether g~oups . . . . . . . . . ........... . . . . . . ................ .. . . ..
. ~ -and l ,, . ' . group per molecule,' CH2=CH-C-O-C~2-C~I-O- - . .

f pro~iding a liquid polyacrylate'in a quick and convenient mannerO Thi8 product cures in the same manner as the . . . .... . . . .
, , pr'oduc't of Example'l, but'ultraviolet cure superiority , ' 10, can be expected to flow out of the presence of the second : acrylate moiety.
, , The invent~on is de~ined in the claim~ which follow.
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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A radiation curable coating composition comprising the addition reaction product of (i) a monoethylenically unsaturated adduct of a monoethylenically unsaturated carboxylic acid or hydroxyalkyl ester thereof with an anhydride containing at least 3 carbon atoms and selected from monoepoxides, lactones, and mixtures thereof, said adduct containing an average of at least 1 mole of anhydride per mole of hydroxy-ester and an average of at least 2 moles of anhydride per mole of acid moiety, with (ii) an organic compound containing a plurality of groups capable of reacting with active hydrogen, said organic compound being a polyisocyanate, polycarboxylic polyanhydride or polyepoxide.

2. A radiation curable coating composition as recited in claim 1 in which the monoethylenically unsaturated adduct is a polyether.

3. A radiation curable coating composition as recited in claim 1 in which the organic compound is benzophenone-tetracarboxylic add dianhydride, said composition including a photosensitiz--r.

4. A radiation curable coating composition as recited in claim 1 in which the adduct is derived from a hydroxyalkyl ester of acrylic acid containing from 2 to 4 carbon atoms in the alkyl group.

5. A radiation curable coating composition as recited in claim 1 in which the anhydride of the adduct is propylene oxide, butylene oxide, butyl glycidyl ether, cyclohexene oxide, phenyl glycidyl ether, tetrahydrofuran, ar epsilon caprolactone, and the monoethylenically unsaturated carboxylic acid is acrylic acid.

6. A radiation curable coating composition as recited in claim 3 in which the benzophenone-tetracarboxylic acid dianhydride moiety is the only photosensitizer present.

7. A radiation curable coating composition as recited in any of claims 1, 4 or 5 in which the adduct contains an average of from 3 to 10 moles of anhydride per mole of acid or hydroxyalkyl ester.