POLYFUNCTIONAL ACRYLATE DERIVATIVES OF CAPROLACTONE-POLYOLS

Abstract: Described herein are polyfunctional acrylate derivatives of caprolactone-polyols. The derivatives have low viscosity, are thermally stable and impart toughness properties to radiation cured coatings utilizing them.

Description: BACKGROUND OF THE INVENTION This invention is directed to polyfunctional acrylate derivatives of caprolactone-polyol8. Polyfunctional acrylates have been used in a large number of. fields including coating and elastomers. Most ultraviolet (UV) light applications are based on binders containing acrylic unsaturations. These binders are generally classified as epoxy acrylates. urethane acrylates and polyester acrylates. Glycol acrylates are also extensively used to modify w curing systems. Acrylate-capped polycaprolactone polyol derivatives are described in U.S. Patent 3,700.643. The derivatives are described as useful in producing coating compositions that are readily cured to solid protective films. The acrylate-capped polycaprolactone compounds include those defined by the following formula:. EMI1.1 where Z is hydrogen or methyl. Q is the residue remaining after reaction of the caprolactone polyol and x is an integer having a value of from 1 to 4. In columns 6 and 7 the patent describes the production of nono-hydroxyl mono-acrylate-capped polycaprolactone and diacrylate capped polycaprolactoneJ i.e., when r in the above formula te 1 or 2. However, the zcrylate-capped Eplycaprolactone coapounds of U.S. Patent 3,780,643 have high viscosity and reduced compatibility with several tes of polymers. Accordingly, they have limited utility 9n coatings formulations. The process employed in U.ss. Patent 3.700.643 produces acrylate-capped polycaprolactones which are high in viscosity, which limits their use as diluents. The process of U. S. Patent 3,700.643 is conducted under a nitrogen atmosphere at elevated temperatures. when this process was repeated. gels formed due to polymerization of the acrylic acid and the acrylates which are used. In a commercial process. the excess acrylic acid is preferably removed by water washing. Using the conditions described in U. S. Patent 3,700.643 emulsions formed when water was added to the reaction mixture, due to the presence of polyacrylic acid. Further. the solvent in the products from U. S. Patent 3,700,643 (Example 13) was stripped off in an inert atmosphere causing an additional increase in viscosity. Finally, the process of U. S. Patent 3.700.643 employs p high level of the inhibitor. phenothiazine, which remains in the product. Phenothiazine at the levels used in Example 13 would interefere with photochemical curing procedures because of the high molar absorptivity of phenothiazine. The polyfunctional acrylate derivatives of this invention have generally lower viscosity. are thermally stable and impart toughness properties to compositions utilizing they. In particular, they are useful as polyurethane uodifiers. Also, they are compatible with a number of polymers and when polymerized, improve the flexibility and toughness of the polymer. Prior at polyester polyols are high in viscosity. - For example, an acrylated polyester.VPS-2700 manufactured by Degussa Corporation for general radiation cured coatings has a viscosity of 8,000 to 13,000 centipoise. In addition. they are difficult to manufacture in functionalities of three or greater since the use of trifunctional monomers in polyesters lead to network structures and gels. TElE lNYENTION The polyfunctional acrylate derivatives of caprolactone-polyol are characterized by the following formula: EMI3.1 wherein R1 is hydrogen or methyl, R2 is the residue remaining after reaction of caprolactone monomer with an organic functional initiator which can be any polyhydroxyl compound as shown in U.S. Patent 3.169,545, X is an integer of 2 to 6, and n is an integer of O to 2. with the proviso that m+n is greater than or equal to 3. and m is greater than n. The caprolactone polyols that can be used to prepare the polyfunctional acrylate derivatives of this invention include any of the known Caprolactone polyols that ace cotnercially available, in the molecular weight range of 300 to 2000, and that are fully described, for example, in U.s. Patent No. 3,169.945. As described in this patent the polycaprolactone polyols are produced by the catalytic polymerization of an excess of a caprolactone and an organic polyfunctional initiator having as least two reactive hydrogen atoms. The organic functional initiators can be any polyhydroxyl compound as is shown in U.S. Patent No. 3.169,g45. 'Lllnstrative thereof are the triols such as glycerol, trimethyloipropane, .2.6-hexanetriol. triethanolamine, triisopropanolamine, and the like: tetrols such as erythritol. pentaerythritol, N,N,N',Nt-tetrakis(2-hydrosyethyllethylene diamine, and the like. When the organic functional initiator is reacted with the caprolactone a reaction occurs that can be represented in its simplest form by the equation: EMI4.1 In this equation the organic functional initiator is the R3-(OH) compound and the caprolactone is the following compound: EMI4.2 this can be caprolactone itself or a substituted caprolactone wherein R4 is independently halogen. an alkyl, alkoxy, acryl4 cycloalkyl. alkaryl or aralkyl group having up to twelve carbon atoms and wherein at least six of the h groups are hydrogen atoms. as shown in U.S. Patent No. 3,169,945. The polycaprolactone polyols that are used are shown by the formula on the right band side of the equation; they can have an average molecular weight of from 200 to about 2,000. The preferred polycaprolactone polyol compounds are those having an average molecular weight of from about 300 to about 1000. The most preferred are the polycaprolactone triol and tetrol compounds having an average molecular weight of from about 300 to about 900; these are most preferred because of their low viscosity properties. In the formula a is an integer representing the average number of repeating units needed to produce the compound having said molecular weights. The hydroxyl number of the polycaprolactone polyol can be from about 15 to 600, preferably from 200 to 500: and the polycaprolactone polyol can have an average of from 3 to 6, preferably 3 to X, hydroxyl groups. lllu6trative of polycaprolactone polyols that can be used in this invention. one can mention the reaction products of a polyhydroxyl compound having an average from 3 to 6 hydroxyl groups with caprolactone. The manner in which these type polycaprolactone polyols is produced is shown in U.S. Patent No. 3,169.945 and many such compositions aze commercially available. In the following table there are listed illustrative polycaprolactone polyols. The first column lists the organic functional tnitiator that is reacted with the caprolactone and the average molecular weight of the polycaprolactone polyol is shown in the second column. Knowing the molecular weights of the initiator and of the polycaprolactone polyol one can readily determine the average number of molecules of caprolactone (CPL Units) that reacted to produce the compounds: this figure is shown in the third column. POLYCAPROLACTONE POLYOLS Average Average No. )PI lit. of of CPL units Initiator polyol in molecules 1 1.2,6-Hexanetriol 476 3 2 Trimethylolethane 577 4 3 Trimethylolpropane 590 4 4 Trimethylolpropane 750 5.4 5 Trimethyloipropane 1.103 8.5 6 Triethanolamine 890 6.5 7 Erythritol 920 920 7 8 Pentaerythritol it 219 9.5 9 Dipentaerythritol 938 6 10 Fructose 865 865 6 The structures of the compounds in the above tabulation are obvious to one skilled in the art based on the information given. Polycaprolactone hexols can be prepared from the addition of caprolactone monomer to hexafunctional starters such as dipentaerythritol. The polyfunctional acrylate derivative may be prepared by reacting the caprolactone polyol with acrylic or methacrylic acid in the presence of a strong acid catalyst. The strong acid catalyst may be sulfuric, methane sulfonic, or p-toluene sulfonic acid. or ion exchange resins, and the like. The catalyst is used in amounts of from about 0.1 to about 5.0. preferably from about 0.5 to about 2.0 percent. The reaction to prepare the polyfunctional acrylate monomer is carried out at a temperature of tror about 60 to about 1200C, preferably from about 80 to about 1050C. The reaction may be carried out at atmospheric pressure, although higher or lower pressures say be nosed. The reaction is generally carried out in the presence of air (oxygen) to prevent polymerization of the acrylate function. Oxygen is generally sparged through the reaction during the course of the reaction. The reaction is carried out for a period of time until the theoretical water is removed or until no further water is produced. This period is generally from about 3 to about ss hours. The reaction is generally carried out in the presence of a solvent of the type which removes water formed during the reaction as an azeotrope. Among the suitable solvents which can be used are the hydrocarbons such as octane. heptane, hexane. benzene. toluene or the tylenes, etc. The reaction is generally carried out in the presence of a suitable inhibitor or combination of inhibitors to prevent polymerization of the acrylic or methacrylic acid double bonds. These inhibitors include the monomethyl ether of hydroquinone. benzoquinone. phenothiazine. rethylhydroquinone. methylene blue, 2,5-di-t-butylhydroquinone, hydroquinone. and other common free radical inhibitors known in the art. The level of inhibitor used is from about 50, parts per million to about 2.0 percent. In the reaction. one hydroxyl equivalent of the caprolactone polyol is reacted with excess of acrylic acid or methacrylic acid to form the caprolactone polyol acrylate. A hydroryl containing acrylated polyol can also be prepared by reacting an excess equivalent of polyol with acrylic acid. The process of this invention may be carried out by adding the caprolactone polyol. and solvent and then adding the acrylic or methacrylic acid. inhibitor and catalyst to a reaction vessel and then heating this to the reflux temperature. During the reaction. oxygen (or air) is continually bubbled through the reaction. After the reaction is complete. the excess acid may be removed by, for example. neutralization by adding a strong base such as sodium or potassium hydroxide, or stripping it off by conventional techniques, or by an ion exchange resin. Excess water may be removed from the reaction by, for example, adding a conventional drying agent such as magnesium sulfate, or by the use of vacuum stripping which also removes the solvent, Air must be sparged into the reaction mixture during stripping. The acrylic esters may also be produced by other methods such as transesterification or acid chloride reaction. The polyfunctional acrylate monomer produced has a viscosity of from about 10 to about 2000 centipoise at 25it. Mixtures of the polyfunctional acrylate derivatives may be used herein. Also, the polyfunctional acrylate monomers. either alone or in combination. may be mixed with the acrylate-capped polycaprolactone compounds of formula (I) wherein x is 1 or 2. EXAMPLES The following exaapleo serve to illustrate specific embodiments of this invention and it is not intended that the invention shall be limited by the examples. The following designations used in the Examples and Controls have the following meaning: Caprolactone Poltol (I)- A trihydroxyfunctional polycaprolactone polyol with an average hydroxyl number of 310 and an average molecular weight of 540 (TONE-0305 obtained from Union Carbide Corporation). raorolactone aolvol (II) - A trihydroxyfunctional polycaprolactone polyol with an average hydroxyl number of 187 and an average molecular weight of 900 tTONE-0310 obtained from Union Carbide Corporation). Caprolactone polyol (III) - A tetrahydroxyfunctional polycaprolactone polyol produced by reacting pentaerythritol and caprolactone with an average hydroxyl number of 360 and an average molecular weight of 622. Caprolactone Dolsol (IV) - A trihydroxyfunctional polycaprolactone polyol with an average hydroxyl number of 560 and an average molecular weight of 300 (TONE-301 obtained from Union Carbide Corporation). Example 1 A 2000 ml glass reaction flask was equipped with a stirred. thermometer and condenser, Dean-Stark trap. air inlet and heating matle and used as the reaction vessel. 300 grams of Caprolactone polyol < 1). 147.3 g. of glacial acrylic acid, 600 ml. 6f benzene, 5 ml. of concentrated sulfuric acid and 4 g. of hydroquinone were added to the reactlon flask at room temperature. The contents of the flask were then heated to about 850C over a period of one hour and maintained at reflux at atsospheric pressure until no further water was produced (about 4.S hours). During the reaction, air was continually'bubbled through the reaction. The reaction mixture uas cooled to about 60 C in a separator funnel and about¯50 ml of benzene added. Then. about 200 g of a 15 percent aqueous sodium hydroxide solution was dripped through the separator funnel. A second aliquot of 200g of a 15 percent aqueous sodium hydroxide solution was added and then the contents shaken. Excess acid and hydroquinone inhibitor were washed out by shaking the solution three times with 50g of a 15 percent aqueous sodium hydroxide solution. After the contents settled, 10 g of magnesium sulfate were added while stirring to remove any remaining water, then the contents filtered to remove the magnesium sulfate. 100 parts per million of mono methyl ether of hydroquinone based on the final product was added and the contents were then stripped of solvent using an air bleed. A 60 to 70S yield was obtained. The product had a viscosity of 250 centipoise at room temperature. Example 2 The The procedure of Example 1 was repeated except that the reaction flask was charged with the following: 300 g Caprolactone polyol (11) BB.4 g Glacial acrylic acid 150 ml Benzene 5 g Hydroquinone 3 ml Concentrated sulfuric acid The product had a viscosity of 442 centipoise at room temperature. ExamPle 3 The procedure of Example 1 was repeated except that the-rtac-tion flask was charged with the following: ali g Caprolactone polyol (III) 174 g Glacial acrylic acid 600 ml Benzene 1 g Hydroquinone 2 ml Concentrated sulfuric acid The product had a viscosity of 624 centipoise at room temperature. Example 4 The procedure of Example 1 was repeated ercept that air was not used and the reaction flask was charged with the following: 150 g Caprolactone polyol (IV) 155 g Methacrylic acid 300 ml Heptane 0.05 g Methylene blue 5 ml Concentrated sulfuric acid The product had a viscosity of 50 centipoise at room temperature. In the above formulae R4 may be halogen, e.g., F, C1, Br or J; the alkyl residue contains 1 to 12, especially 1 to 8, carbon atoms, e.g. methyl, ethylt n-propyl, i-propyl, n-butyl, i-butyl, sec.-butyl, tert.-butyl, n-pentyl, 1-pentyl, n-hexyl, i-hexyl, octyl, nonyl, decyl and dodecyl; alkyl in the alkoxy groups is defined as above; the aryl residue contains 6 to 12 carbon atoms, e.g. phenyl and naphthalene; the alkaryl residue contains 7 to 12 carbon atoms, e.g. methyiphenyl, dimethylphenyl, trimethylphenyl, ethyl phenyl, diethylphenyl, propylphenyl and butylphenyl; the aralkyl residue contains 7 to 12 carbon atoms, e.g. benzyl, propylphenyl, butylphenyl; the cycloalkyl residue contains 3 to 1w2, preferably 5 to 6, carbon atoms, e.g. cyclobutane, cyclopentane, cyclohmzne, cycloheptane and cyclooctane.

Claims: WHAT IS CLAIMED IS: 1. A polyfunctional acrylate derivative of a caprolactone-polyol characterized by the following formula: EMI13.1 wherein R1 is hydrogen or aethyl. R2 is the residue remaining after teaction of a caprolactone monomer with an initiator ra is an integer of 2 to 6, and n is an integer of 0 to 2, with the proviso that m+n is greater than or equal to 3 and m is greater than n. 2. A polyfunctional acrylate derivative as defined in claim 1 wherein R2 is the residue remaining after the reaction of epsilon caprolactone and trimethylolpropane. 3. A polyfunctional acrylate derivative as defined in claim 1 wherein R2 is the residue remaining after the reaction of epsilon caprolactone and pentaerythritol. 4. A polyfunctional acrylate derivative as defined in claim 1 wherein R1 is hydrogen and n is 3. 5. A polyfunctional acrylate derivative as defined in claim 1 wheren R1 is hydrogen and n is 4. 6. A polyfunctional acrylate derivative as defined in claim 1 wherein R1 is hydrogen and n is 5. 7. A polyfunctional acrylate derivative as defined in claim 1 wherein g1 is hydrogen and n is 6. 8. A radiation curable coating composition containing the polyfunctional acrylate derivative as defined in Claim 1.

Inventors: CORNELL, JOHN ALSTON, KUBISEN, STEVEN JOSEPH JR.
Applicants: UNION CARBIDE CORPORATION
Application year: 1985
Main classification: C07C69
IPC codes: C07C69, C08G63, C07C67