URETHANE MODIFIED VINYL ESTER RESINS HAVING SECONDARY HYDROXYL GROUPS

Abstract: Curable reaction product of a vinyl ester resin having secondary hydroxyl groups and from 0.05 to 1 equivalent based on the secondary hydroxyls of isocyanatoethyl methacrylate. The products are useful as neat resins and in reinforced plastics.

Description: URETHANE MODIFIED VINYL ESTER RESINS HAVING SECONDARY HYDROXYL GROUPS In many resin applications, low viscosity and good physical properties after a minimal heat cure are necessary. Frequently, however, those objectives are antithetical♦ Certain polymer systems that are based 5 on a polyglycidyl ether, such as the vinyl ester resins, have hydroxyl groups along the molecular structure. Those hydroxyl groups cause an appreciable increase in viscosity which requires extensive dilution with a monomer to permit facile fabrication. 10 It would be desirable to have a procedure for reducing the viscosity of hydroxyl containing polymers while at least retaining the properties of the polymer when cured. This invention is directed to a curable 15 reaction product of a vinyl ester resin having secondary hydroxyl groups and from 0.05 to 1 equivalent based on ^ the secondary hydroxyls of isocyanatoethyl methacrylate. In the uncured state, the reaction product has a lower f viscosity than the corresponding unmodified resin. In 20 the cured state, the increased cross-linking density provides improved heat distortion temperatures and hardness and a decrease in water and solvent sorption. The vinyl ester resins useful in making the reaction product must have more than one secondary hydroxyl group in the polymer chain. Bowen in U.S. Patent Nos. 3,066,112 and 3,179,623 describes the preparation of vinyl ester resins by esterifying acrylic or methacrylic acid with a polyepoxide. That patentee also describes the alter- nate procedure wherein a glycidyl acrylate or meth¬ acrylate is reacted with the sodium salt of bisphenols. Vinyl ester resins based upon epoxy novolacs are taught in U.S. Patent. No. 3,301,743. For use herein, the vinyl ester resin can be prepared from any glycidyl polyether. Useful glycidyl ethers are those of polyhydric alcohols and phenols. Such glycidyl polyethers are commercially available or are readily prepared by reacting at least two moles of an epihalohydrin or glycerol dihalohydrin with one mole of the polyhydric alcohol or phenol together with a sufficient amount of caustic to react with the halogen of the halohydrin. The products are characterized by the presence of more than one glycidyl ether group per molecule. The useful acids for making the vinyl ester resins are those ethylenically unsaturated monocar- boxylic acids such as acrylic, methacrylic, cinnamic acids and their halogenated isomers. Also included are the hydroxyalkyl acrylate or methacrylate half esters of dicarboxylic acids as described in U.S. Patent No. 3,367,992 wherein the hydroxyalkyl group preferably contains from 2 to 6 carbon atoms. The glycidyl ether and the acid are reacted in about stoichiometric equivalency generally with 5 heating in the presence of a catalyst, such as a tri- valent chromium salt, as, for example, chromium tri¬ chloride or a tertiary amine, as, for example, tris- (N,N-dimethylaminomethyl phenol). Vinyl polymerization inhibitors are also commonly included to prevent pre- 10 mature polymerization. It is commonplace in the vinyl ester resin art to adjust the viscosity of the liquid uncured resin with a reactive diluent, usually a copolymerizable monomer. Suitable monomers for this use include vinyl 15 aromatic monomers, such as styrene and vinyltoluene, and acrylate or methacrylate esters of lower alkanols. The reactive diluent may be an amount of up to 60 weight percent of the combined resin/monomer weight. The isocyanatoethyl methacrylate is employed 20 in an amount of 0.05 to 1.00 equivalent per equivalent of hydroxyl. Less than about 0.05 equivalent imparts little observable change in the cured product. Any isocyanate in excess of 1.0 equivalent has no place to react and thus could detract from the desired proper- 25 ties of the cured product. *^ The reaction of the isocyanate with the s secondary hydroxyl is conducted using known techniques. In a typical reaction, the polymer or polymer precur¬ sor, the reactive diluent and a catalyst, such as 30 stannous octoate, are thoroughly mixed together and f OMP brought to a mildly elevated temperature of, for example, 50°C. The isocyanate is slowly added with stirring. Heating is maintained until absence of the isocyanate band in the infrared spectrum is attained which indi- cates the reaction to be complete. The potential for cross-linking in the iso- cyanato product can be adjusted in several ways. The amount of unsaturation in the polymer or precursor can be varied. The number of hydroxyls in that starting material can vary. The amount of unsaturated isocyanate can be adjusted to that providing the desired number of cross-links. Some of the hydroxyls can be reacted with a saturated aliphatic isocyanate. The products have improved, properties, par- ticularly heat distortion temperature, hardness and low solvent sorption. The products find use as neat resins and in reinforced plastics. Of particular note are their use in fiberglass reinforced filament wound pipe, electrical laminates, electrical insulating varnishes and coatings, bulk and sheet molding compounds, and corrosion resistant vessels and linings for vessels. The concept of the invention will be more apparent from the following illustrative examples wherein all parts and percentages are by weight. Example 1 One hundred parts of the trimethacrylate of tris(4-glycidylphenyl)methane, 25 parts of styrene and 0.1 part stannous octoate were mixed while heated to 50°C. To that mix while stirred was slowly added 47.02 - ϊmϊ -5- parts isocyanatoethyl methacrylate (IEM) and the temper¬ ature raised to 60°C. Heating and stirring were con¬ tinued until the absence of the isocyanate band in the IR spectrum at 2280 cm " indicated the reaction to be complete. The IEM was employed in the amount of 0.7 equivalent per equivalent of hydroxyl. To the product was added 11.75 grams styrene. The resin was cured with 1.5 parts benzoyl peroxide per 100 parts resin at a temperature schedule of 2 hours at 90°C, 4 hours at 165°C and 16 hours at 200°C. For comparison, the trimethacrylate with 20 percent styrene was cured in an identical manner. The samples were tested according to standard methods with the following results. Nonmodified IEM Modified Viscosity*, cstks 11,510 7,565 (mVs) (0.01151) (0.007565) HDT, °C at 264 psi >230 >230 (1820 kPa) T °C 245 266 Flex. Mod. , psi 9.38 x 10 5 8.03 x 10 (GPa) (6.47) (5.54) Flex. Strength, psi 17,470 9,466 (MPa) (120.45) (65.27) Barcol Hardness 41 53 Gardner Color 17 17 * Before cure Other samples of the above-described resins were cured with 1.5 parts benzoyl peroxide at 2 hours -6- at 90°C and 4 hours at 165°C. The heat distortion temperature of the nonmodified resin was 203°C and of the IEM modified resin was greater than 230°C. The Barcol Hardness of the former was 42 and of the latter was 50. Example 2 A resin was prepared according to the pro¬ cedure and stoichiometry of Example 1 using the di eth- acrylate of the diglycidyl ether of bisphenol A as the polymer and vinyltoluene as the reactive diluent. The resin was cured with 1.5 parts benzoyl peroxide per 100 parts of resin for one-half hour at 150°C. The samples were tested according to standard procedures with the following results. Nonmodified IEM Modified Viscosity cstks >1,646 1,445 (mVs) (>.001646) (0.001445) HDT, °C at 264 psi 110 137 (1820 kPa) Flex. Mod., psi 4.99 x 10 5 5.29 x 10 5 (GPa) (3.44) (3.65) Flex. Strength, psi 21,510 17,240 (MPa) (148.31) (118.87) Tensile Strength, psi 9,100 6,460 (kPa) (62.74) (44.54) 24 Hr. H„0 Boil, % Δ wt. 1.827 1.758 Barcol Hardness 45 49 Gardner Color >1 1

Claims: CLAIMS 1. A curable reaction product of a vinyl ester resin having secondary hydroxyl groups and from 0.05 to 1 equivalent based on the secondary hydroxyls of isocyanatoethyl methacrylate. 2. The reaction product of Claim 1 wherein the vinyl ester resin is the diester of a polyglycidyl ether with an unsaturated monocarboxylic acid. 3. The reaction product of Claim 1 wherein the vinyl ester resin is the diester of a diglycidyl ether of bisphenol A and a monocarboxylic acid. 4. The reaction product of either Claim 2 or 3 wherein the monocarboxylic acid is methacrylic acid. 5. The reaction product of Claim 1 addi¬ tionally containing up to 60 weight percent of an ethylenically unsaturated monomer. 6. The reaction product of Claim 5 wherein the unsaturated monomer is styrene. OMPI

Inventors: BURTON LAWRENCE BRUCE, BURTON, LAWRENCE, BRUCE
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1982
Main classification: C08L63
IPC codes: C08F290, C08F299, C08G18