WO1986004075A1

WO1986004075A1 - Epoxy novolac resins having reduced 2-functional components and a process for reducing 2-functional components in novolac resins

Info

Publication number: WO1986004075A1
Application number: PCT/US1986/000052
Authority: WO
Inventors: James L. Bertram; Louis L. Walker; Avis L. Mccrary; Fermin M. Cortez
Original assignee: The Dow Chemical Company
Priority date: 1985-01-11
Filing date: 1986-01-13
Publication date: 1986-07-17
Also published as: FI863663A0; NO900479D0; JPH0471927B2; NO164910C; DK435386A; DK435386D0; EP0209572A4; EP0209572A1; BR8604531A; NO164910B; JPS62501780A; FI863663A; NO863619D0; JPH0641262A; NO863619L; NO900479L

Abstract

Epoxy novolac resins having reduced 2-functional components and a process for reducing 2-functional components in novolac resin which may be used to prepare the epoxy novolac resins. When 2-functional and 3-functional components are present in an epoxy phenol-formaldehyde novolac resin, the weight ratio of the 2-functional component to the 3-functional component is less than 1.1:1. When 2-functional and 3-functional components are present in an epoxy cresol-formaldehyde novolac resin, the weight ratio of the 2-functional component to the 3-functional component is less than 0.5:1. The epoxy novolac resins of this invention when cured exhibit increased glass transition temperature. These resins are useful in the preparation of composites, molding, castings, coating, adhesives and laminates.

Description

EPOXY NOVOLAC RESINS HAVING REDUCED 2-FUNCTIONAL COMPONENTS AND A PROCESS FOR REDUCING 2-FUNCTIONAL COMPONENTS IN NOVOLAC RESINS

The present invention pertains to epoxy novolac resins and to a process for preparation of novolac resins which may be used to prepare the epoxy novolac resins.

High functional (average functionality of 5^* to 8) epoxy novolac resins have high Tg values when cured with sulfanilimide. However, they are very difficult to prepare due to the high viscosity of the novolac resin precursors. The present invention is directed to epoxy novolac resins having high Tg values when cured with typical epoxy curing agents such as, for example, meth lenedianiline, diaminodiphenylsulfone, sulfanilimide and the like while having a relatively low melt viscosity.

One aspect of the present invention pertains to an epoxy novolac resin having an average epoxide functionality from 3 to 12 represented by the formula

wherein each-A is independently a divalent hydrocarbon group having from 1 to 14, preferably from 1 to 8, carbon atoms; each R is independently hydrogen, a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9, preferably from 1 to 4, carbon atoms, each R' is independently hydrogen or an alkyl group having from 1 to 4 carbon atoms, and n has an average value of from 1 to 10, with the provisos that ' (a) when 2-functional and 3-functional components are present and R is hydrogen, then the weight ratio of 2-functional component to 3-functional component is less than 1.1:1, preferably less than 0.75:1, most preferably less than 0.5:1; (b) when 2-functional and 3-functional components are present and each R is independently a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9, preferably 1 to 4, carbon atoms, then the weight ratio of the 2-func¬ tional component to the 3-functional component is less than 0.5:1; (c) when the average epoxide functionality is from 3 to about 5, the resin contains less than 12.5, preferably less than 7, percent by weight of two functional component; and (d) when the average epoxide functionality is from about 5 to 12, the resin contains less than 9, preferably less than 5, percent by weight 2-functional component. Another aspect of the present invention concerns a process for preparing novolac resins repre¬ sented by the formula

wherein A, R and n are as previously defined, and hav¬ ing reduced quantities of the 2-functional component which process comprises (I) reacting in the presence of a suitable catalyst

(A) a material having at least one aromatic hydroxyl group per molecule with

(B) an aldehyde at a molar ratio of (B):(A) of from 0.3:1 to 0.95:1, preferably from 0.45:1 to 0.75:1;

(II) removing the excess aromatic hydroxyl- -containing material; and (III) subjecting the product from step (II) to extraction with water until the resultant product contains less than 25, preferably less than 50 percent by weight of the 2-functional component than was present after step II.

When the novolac resin produced by the above process contains both 2-functional and 3-functional com¬ ponents and R is hydrogen, they are present in a weight ratio of 2-functional component to 3-functional compon¬ ent of less than 1.1:1, preferably less than 0.75:1, more preferably less than 0.5:1. When the novolac resin produced by the above process contains both 2-functional and 3-functional components and each R is independently a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9 carbon atoms, they are present in a weight ratio of 2-functional component to 3-functional component of less than 0.5:1. When the novolac resin has an average aromatic hydroxyl function¬ ality of from 3 to about 5, it contains less than 12.5, preferably less than 7, percent by weight 2-functional component. When the novolac resin has an average aro¬ matic hydroxyl functionality of from about 5 to 12, it contains less than 9, preferably less than 5, percent of weight 2-functional component.

By the expression "2-functional component" as employed herein it is meant that portion of the novolac resin or epoxy novolac resin wherein n has a value of zero.

By the expression "3-functional component" as employed herein, it is meant that portion of the novolac resin or epoxy novolac resin wherein n has a value of 1.

By the expression "average functionality" as employed herein, it means the average number of aro¬ matic hydroxyl groups per molecule.

Suitable monohydric aromatic materials which can be employed herein include, for example, those represented by the formula

wherein each R is as previously defined.

Particularly suitable materials include, for example, phenol, methylphenol, ethylphenol, propylphenol, butylphenol, nonylphenol, bromophenol, chlorophenol, resorcinol, hydroguinone, catechol or mixtures thereof.

Suitable aldehydes which can be employed herein include any aliphatic, cycloaliphatic or aromatic aldehyde having from 1 to 14, preferably from 1 to 8, carbon atoms. Particularly suitable such aldehydes include, for example, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde or mixtures thereof.

Suitable acid catalysts which can be employed herein include, for example, oxalic acid, p-toluene sulfonic acid, benzene sulfonic acid, hydrochloric acid, sulfuric acid or mixtures thereof.

The reaction between the aldehyde and the monohydric aromatic material can be carried out at any suitable temperature such as, for example, from 90°C to 150°C, preferably from 100°C to 120°C. The reaction is continued until the reaction is substantially complete, usually from 0.5 to 6 hours (1800-21600-s), preferably from 1 to 2 hours (3600-7200 s).

The water extraction step of the present invention can be multistage batch extractions or it can be by continuous co-current or counter-current extraction.

The water extraction is usually conducted at a temperature of from 60°C to 180°C, preferably from 90°C to 150°C and the number of extractions or the contact time is that which is sufficient to produce the desired result, i.e. produce a product containing less than 25, preferably less than 50, percent by weight of the 2-functional components than was originally present in the novolac resin prior to water extraction.

Other suitable methods for removing portions of the 2-functional component^' such as vacuum distillation have also been employed.

If desired, the efficiency of the water extraction can be enhanced by employing minor amounts of one or more organic solvents with the water. Suitable such organic solvents include, for example, ketones, alcohols and glycol ethers. Particularly suitable organic solvents include, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, amyl alcohol, monomethyl ether of dipropylene glycol or mixtures thereof.

Also, if desired, the two functional novolac resin can be removed from the aqueous extract by extrac¬ tion with a suitable organic solvent such as those mentioned above which are not miscible with water with methyl isobutyl ketone being particularly suitable.

The epoxy novolac resins of the present invention can be prepared from novolac resins having less than 25, preferably less than 50, percent by weight of two functional product than was originally present in the original novolac resin prior to water extraction. The novolac resin is reacted with an epihalohydrin and then subjected to dehydrohalogenation with a basic-acting material such as, for example, sodium hydroxide.

Epoxy resins can be cured with the novolac resins prepared by the process of the present invention. Suitable epoxy resins include, for example, the glycidyl epoxy resins of polyhydric phenols, bisphenols, novolac resins, aliphatic polyols and nitrogen-containing compounds. These and other suitable epoxy resins are disclosed in Handbook of Epoxy Resins by Lee and Neville, McGraw-Hill, 1967, particularly Chapters 2 and 3.

In curing epoxy resins with the novolac resins of the present invention, the usual quantity to be employed is that which provides a hydroxyl:epoxy ratio of from 0.8:1 to 1.1:1, preferably from 0.9:1 to 1:1. In some instances, a suitable curing quantity may be outside these enumerated quantities.

The epoxy novolac resins of the present invention can be employed, for example, in the prepara¬ tion of composites, moldings, castings, coatings, adhesives and laminates.

The following examples are illustrative of the present invention but are not to be construed as to limiting the scope thereof in any manner.

TEST METHODS The following test methods were employed in the Examples.

MOLECULAR WEIGHT was determined using standard gel permeation chromatography (GPC) methods using poly¬ styrene standards for molecular weight calibration. GLASS TRANSITION TEMPERATURE (Tg) was determined using a DuPont 1090 analyzer with a model 912 differential scanning calorimetry (DSC) for Tg up to about 250°C.

For Tg's >250°C a DuPont model 943 thermal mechanical analyzer (TMA) was employed.

SOFTENING POINTS were determined employing a Mettler model FP-53 softening point apparatus (MSP).

FRACTURE TOUGHNESS MEASUREMENT (G_lg)

The method for measuring^"G-,_c (fracture tough- ness or "critical strain energy release rate") is an adaptation of ASTM E-399 for plastics materials from the original usage with metals. The compact tension test is now widespread in usage and is described in the J. Mater. Sci., Vol. 16, 2657, 1981. An individual test piece is cut to an approximate 1" (25.4 mm) square from a flat casting usually of 1/8" (3.175 mm) thickness. A dovetail notch is cut into one edge, centered, about 1/4" (6.25 mm) in depth. Next, a razor blade is inserted into this notch and tapped to produce a precrack. Two holes are then drilled adjacent to the dovetail as indicated in ASTM E-399, allowing the test piece to be pinned into position in the Instron test machine. Extension of the sample now allows the force required to propagate opening of the precrack to be measured, using a test speed of 0.02 inches/minute (0.0085 mm/sec). This force is used in the equation given in ASTM E-399, along with the required sample dimensions and actual precrack length, to calculate a "stress intensification factor" K_Q. This is then combined with the tensile modulus (in those instances where the tensile modulus was not measured, a value of 300,000 psi (2.07 GPa) was used) and Poisson's ratio for the material to give the value for G-,_c, usually reported in ergs/cm² x 10⁶. A scale comparing typical values for G,_ for various plastics and metals is given in reference Lee, L.H., "Physicochemical Aspects of Polymer Surfaces", K.L. Mittal, ed. Plenum Press, New York, N.Y., 1983.

EXAMPLE 1

A. Preparation of Phenol-Formaldehyde Novolac Resin

A novolac resin was prepared by reacting 2.89 parts phenol, 1.0 part of 37 percent formalin, and 0.0018 parts oxalic acid to produce a resin with a Mettler softening point of 74.1, melt viscosity at 150°C of 100 cps. Analysis by gel permeation chroma- tography (GPC) showed the product to have a wt. average M.W. of 813, a no. average M.W. of 583, with a polydispersity of 1.40. The product contained 24.98 percent by weight of 2-functional components and 17.18 percent by weight of 3-functional components for a ratio of 2-functional to 3-functional components of 1.24:1.

B. Removal of 2-Functional Product

The above prepared phenol-formaldehyde novolac resin was repeatedly extracted with boiling water until the 2-functional content was less than about 1 percent by weight.

C. Preparation of Epoxy Novolac Resin

The product from Example 1-B, 206 grams, was dissolved in 925 grams of epichlorohydrin, 484.7 grams of isopropanol and 78.6 grams of water. This mixture was then heated to 70°C and 360 grams of 20 percent aqueous sodium hydroxide was added during approximately 45 minutes (2700 s). The reaction mixture was digested at this temperature for an additional 15 minutes (900 s). Then the aqueous phase separated and was discarded. Twenty percent aqueous sodium hydroxide, 160 grams, was added to the mixture at 70°C during approximately 20-30 minutes (1200-1800 s). The reaction was digested for an additional 15-20 minutes (900-1200 s) at 70°C, then cooled. The aqueous layer was separated and the organic layer was repeatedly washed with water until free of salt and sodium hydroxide. Additional epichlorohydrin, 462 grams, was added during the washing steps to aid separation. The product was obtained by removing the excess epichlorohydrin and solvent via vacuum distilla¬ tion. The semi-solid epoxy resin product had an epoxy content of 23.3 percent, an epoxide equivalent weight of 184.5 and a hydrolyzable chloride content of 51 ppm.

D. Curing ό^*f Epoxy Novolac Resin

The epoxy resin from Example 1-C, 35.0 grams, was heated to about 150°C, and 6.93 grams of sulfanilamide added. The mixture was stirred until homogenous, then poured into an aluminum mold, 1/8 x 5 x 4 inches (0.3175 x 12.7 x 10.16 cm), and cured as follows: 16 hours (57600 s) at 150°C, followed by 2 hours (7200 s) at 200°C, and an additional 2 hours (7200 s) at 225°C. The casting was then cooled and analyzed for Tg by DSC. The product gave an inflection at 273°C with the onset of an exotherm indicating an incomplete cure. After post curing for 2 hours (3600 s) at 260°C, the Tg was >300°C.

E. Curing of Epoxy Novolac Resin

Example 1-D was exactly repeated, with the exception that 0.1 ml of a 70 percent solution of butyl triphenyl phosphonium acetate*acetic acid complex in methanol was added along with the sulfanilamide. The cured casting had the following properties: Tg of >300°C, G_lc of 0.11 kJ/m².

COMPARATIVE RUN A

A. Curing of Commercially Available Epoxy Novolac Resin For Comparative Purposes

A nominally 3.6 average f nctionality epoxy novolac resin (available from The Dow Chemical Company as D.E.N. 438, epoxide equivalent weight - 179.7, a wt. avg. M.W. of 1,123, a no. avg. M.W. of 618 with a polydispersity of 1.7 and containing about 20.6 percent by weight of 2-functional product with a weight ratio of 2-functional to 3-functional components of 1.39:1), 35.0 grams, was heated to about 150°C and mixed with

7.12 grams sulfanilamide .exactly as described in Example (1-D). The cured resin had the following properties: Tg of 172°C and G_lc of 0.15 kJ/m².

B. Curing of a Commercially Available Epoxy Novolac Resin for Comparative Purposes

Example 1-F was exactly repeated, except the catalyst as described in Example (1-E) was also added. The cured resin had the following properties: Tg of 209.7°C, G_lc of 0.21 kJ/m² and a notched Izod Impact of 0.18 ft. lbs. per inch of notch (9.6 J per m of notch).

EXAMPLE 2

A. Preparation of Phenol-Formaldehyde Novolac Resin A portion of the novolac resin prepared in Example 1-A was employed. B. Removal of 2-Functional Product

The above prepared novolac resin was continu¬ ously extracted with 99°C water until the 2-functional content was 14.1 percent by wt. as measured by GPC. The 3-functional content was 17.21 percent by wt. for a ratio of 2-functional to 3-functional of 0.82:1. The wt. avg. M.W. was 922, the no. avg. M.W. was 654, and the polydispersity was 1.40. The solid product had a Mettler softening point of 84.3°C, and a melt viscosity at 150°C of 165 cps (0.165 Pa-s).

C. Preparation of Epoxy Novolac

Using the procedure as described in Example 1-C, a portion of the above extracted novolac resin prepared in Example 2-B, (206 grams) was reacted with 925 grams of epichlorohydrin in 498 grams of isopropanol and 80.4 grams of water. After separating the aqueous phase, an additional 32 grams of sodium hydroxide dissolved in 128 grams of water was added in the second step. The epoxy product had an epoxide equivalent weight of 179.4, a hydrolyzable chloride content of 768 ppm, a Mettler softening point of 53.5°C, and a melt viscosity of 100 cps (0.1 Pa-s) at 150°C. The wt. avg. M.W. was 1,106, no. avg. M.W. was 719, and the polydis¬ persity was 1.54. The average epoxide functionality was calculated as 4.0. The 2-functional and 3-functional content was 10.50 percent and 12.65 percent by weight, respectively to give a ratio of 0.83:1.

D. Curing of Epoxy Novolac Resin

A portion of the epoxy resin prepared in Example 2-C, 10.0 grams was mixed at 150°C with 2.76 grams of methylene dianiline till homogenous, then cured via the following schedule: 2 hours (7200 s) at 150°C, 1 hour (3600 s) at 200°C, 1 hour (3600 s) at 250°C, and 3/4 hour (2700 s) at 270°C. The glass transition temperature (Tg) was determined by expansion using a DuPont model 943 thermal mechanical analyzer (TMA) to be 306.0°C.

COMPARATIVE RUN B

A. Curing of a Commercially Available Epoxy Novolac with Methylenedianiline

The resin described in Comparative Run A-A, 10.0 grams was cured as described in Example 2-D. The Tg as measured by TMA was 184.3°C.

B. Solvent Extraction of a Commercially Available Epoxy Novolac Resin

A portion of the resin described in Comparative Run A-A was treated with xylene exactly as described in U.S. 3,928,288, Example VIII. The product had an epoxide equivalent weight of 204, a wt. average molecular weight of 2,043, a no. average molecular weight of 1,106, with a polydispersity of 1.85, a 2-functional content of 6.23, with a ratio of 2-functional to

3-functional. content of 1.12:1.0. The average epoxide functionality was calculated as 5.4.

C. Cure of Epoxy Novolac

A portion of the resin from Comparative Run B-B, 10.0 grams, was reacted with 2.42 grams of methylenedianiline exactly as described in Example 2-D. The cured resin had a Tg as measured by TMA of 312.3°C.

D. Curing of an Epoxy Novolac Resin with a Phenolic Novolac A portion of the epoxy novolac resin described in Comparative Run A-A, 10.0 grams was mixed at 177°C with 5.76 grams of the phenolic novolac resin described in Example 1-A and 0.12 grams of a 70 wt. percent solution of tetrabutylphosphonium acetate-acetic acid complex in methanol. The mixture was cured 3 hours (10800 s) at 177°C, 2 hours (7200 s) at 200°C, and 1 hour (3600 s) at 225°C. The cured product had a Tg as measured by DSC of 154.4°C.

E. Curing of an Epoxy Novolac Resin with a Phenolic Novolac A portion of the epoxy novolac resin described in Comparative Run A-A, 10 grams was mixed with 5.76 grams of the phenolic resin described in Example 2-B and treated exactly as described in Comparative Run B-D. The product had a Tg as measured by DSC of 153.4°C.

EXAMPLE 3

A. Preparation of Phenol-Formaldehyde Novolac

A portion of the novolac resin from Example • 1-A was employed.

B. Removal of 2-Functional Product The above prepared novolac resin was continu¬ ously extracted with 99°C water until the 2-functional content was 2.55 percent by wt. as determined by GPC. The resin had a wt. avg. molecular weight of 1,038, a no. avg. M.W. of 814, with a polydispersity of 1.28. The weight ratio of 2-functional to 3-functional was less than 0.5:1.

C. Preparation of Epoxy Novolac

Using the same procedure as described in Example 1-C, 425.9 grams of the above novolac was reacted with 1894.0 grams of epichlorohydrin in 1019.8 grams of isopropanol using 1065.2 grams of 20 percent aqueous sodium hydroxide. The epoxy novolac had an epoxide equivalent weight of 177.9. The wt. avg. M.W. was 1309, no. avg. M.W. 862, and the polydispersity was 1.46. The average epoxide functionality was calculated as 4.8. The 2-functional content was 2.29 percent vs. 9.9 percent for the 3-functional product to give a weight ratio of 2-functional to 3-functional of 0.23:1.

D. Curing of Epoxy Novolac A portion of the epoxy novolac resin prepared in Example 3-C, 10.0 grams was reacted with 2.78 grams of methylenedianiline exactly as described in Example 2-D. The cured product had a Tg of 356.9°C as measured by TMA.

E. Curing of Epoxy Novolac

A portion of the epoxy resin prepared in Example 3-C, 34.3 grams was mixed at 150°C with 10.16 grams of diaminodiphenylsulfone until homogenous, then degas in a vacuum oven and poured into a 1/8 inch (0.3175 cm) aluminum mold. The casting was cured for 2 hours (7200 s) at 150°C, 1 hour (3600 s) at 200°C, 1 hour (3600 s) at 250°C and 3/4 hour (2700 s) at 270°C. The casting had the following properties: Tg >360°C, Flexural Strength 15,100 psi (104 MPa) and a Flexural Modulus of 533,000 psi (3672 MPa).

EXAMPLE 4

A. Preparation of Phenol-Formaldehyde Novolac Resin

A glass reactor equipped with a stirrer, reflux condenser, addition funnel, and a device for controlling temperature was charged with 550 grams

(5.85 moles) of phenol and 2.75 grams (0.03 moles) of oxalic acid. This mixture was heated to 110°C, and 298.8 grams (3.68 moles) of 37 percent formalin was slowly added during approximately 60 minutes (3600 s). The reaction mixture was allowed to reflux during the formalin addition, and for about 60 minutes (3600 s) thereafter. A vacuum was then applied, and the excess phenol and water were removed by vacuum distillation at a final temperature of 180°C.

The solid novolac resin had a Mettler softening point of 87.9°C, analysis by gel permeation chromato- graphy (GPC) showed the product to have a wt. avg. M.W. of 1,044, a no. avg. M.W. of 700, with a polydispersity of 1.49. The product contained 16.3 percent 2-functional components, and the ratio of 2-functional to 3-functional was 1.2 to 1.0.

_*

B. Removal of 2-Functional Product

The above prepared novolac resin was continu¬ ously extracted with 99°C water until the 2-functional content was less than 0.5 percent by weight as measured by GPC. The weight ratio of 2-functional to 3-functional components was less than 0.5:1.

C. Preparation of Epoxy Novolac Resin

Using the exact same procedure as described in Example 1-C, 307 grams of the product from Example 4-B was reacted with 767.0 grams of 20 percent aqueous caustic in 1365.3 grams of epichlorohydrin, 735.1 grams of isopropanol and 118.7 grams of water. The product had a MSP of 81.3°C, a melt viscosity of 589 cps (0.589 pa-s) measured at 150°C, and an epoxide equivalent weight of 186.1. The ratio of 2-functional to 3-functional components was less than 0.5:1. EXAMPLE 5

A. Preparation of Phenol-Formaldehyde Novolac Resin

Using the procedure as described in Example 4-A. 1506.6 grams (16.03 moles) of phenol was reacted with 831.56 grams (10.26 moles) of 37 percent formalin using 7.53 grams (0.084 moles) of oxalic acid. The solid product had a Mettler softening point of 90.7°C. The 2-functional content was 15.27 percent as measured by GPC. The wt. avg. M.W. was 1,098, no. avg. M.W. 714 with a polydispersity of 1.54. The product contained 15.27 percent by weight 2-functional components, and a 3-functional component content of 12.67 percent by weight for a ratio of 2-functional to 3-functional components of 1.2:1.

B. Removal of 2-Functional Product

A portion of the above prepared product was continuously extracted with about 99°C water until the 2-functional content was 4.26 percent by weight as measured by GPC. The solid product had a Mettler softening point of 108.9°C. The wt. 'avg. M.W. was 1,263, no. avg. M.W. 895, with a polydispersity of 1.41. The ratio of 2-functional to 3-functional components was 0.40:1.

C. Removal of 2-Functional Product A second portion of the novolac resin prepared in Example 5-A was continuously extracted with water until the 2-functional content was less than 0.5 percent by weight as measured by GPC. The Mettler softening point was 128°C. The wt. avg. M.W. was 1,446,^' no. avg. M.W. 1,138, and the polydispersity was 1.27. The ratio of 2-functional to 3-functional components was less than 0.25 to 1.0. D. Preparation of Epoxy Novolac

A portion of the resin prepared in Example 5-B, 402.5 grams was reacted with 1789.9 grams of epichlorohydrin in 963.8 grams of isopropanol and 155.6 grams of water using 1006.4 grams of 20 percent aqueous caustic as described in Example 1-C. The product had an epoxide equivalent weight of 185. The wt. avg. M.W. was 1,481, the no. avg. M.W. was 935, with a poly¬ dispersity of 1.58. The average epoxide functionality was calculated at 5.1. The 2-functional content was 3.81 percent. The weight ratio of 2-functional to 3-functional components was less than 0.25:1.

E. Preparation of Epoxy Novolac

A portion of the resin prepared in Example 5-C, 385.3 grams was reacted with 1713.6 grams^' of epichlorohydrin in 922.7 grams of isopropanol and 149 grams of water using 964.6 grams of 20 percent aqueous caustic as described in Example 1-C. The product was a friable, non-sintering solid with a MSP of 85°C, and an' ^' epoxide content of 23 percent (an epoxide equivalent weight of 187). The wt. avg. M.W. was 1,719, no. avg. M.W. 1,234, with a polydispersity of 1.39. The average epoxide functionality was calculated as 6.6. The 2-functional content was less than 0.5 percent. The ratio of 2-functional to 3-functional components was less than 0.25 to 1.0.

EXAMPLE 6

A. Preparation of Phenol-Formaldehyde Novolac Resin

Using the procedure described in Example 4-A, 3000 grams (31.88 moles) of phenol was reacted with

1655.96 grams (20.4 moles) of 37 percent formalin using 15.0 grams (0.167 moles) of oxalic acid. The solid resin obtained had a Mettler softening point of 92.7, and a melt viscosity of 380 cps at 150°C. By GPC analysis, the wt. avg. M.W. was 1,168, no. avg. M.W. 753, with a polydispersity of 1.55. The resin contained 16.67 percent by weight 2-functional component and 13.43 percent by weight 3-functional component. The weight ratio of 2-functional to 3-functional components was 1.24:1.

B. Removal of 2-Functional Product A portion of the above product was continuously extracted with approximately 99°C water until the 2-functional content was 0.36 by weight as measured by HPLC. By GPC analysis, the wt. avg. M.W. was 1,452, no. avg. M.W. 1,123, -with a polydispersity of 1.29. The ratio of 2-functional to 3-functional components was less than 0.25:1.

C. Removal of 2-Functional Product

A second portion of the novolac resin prepared in Example 6-A was continuously extracted with hot water until the 2-functional content was 0.73 percent by wt. as measured by HPLC. The resin had a wt. avg. M.W. of 1,427, a no. avg. M.W. of 1,090, with a poly¬ dispersity of 1.31. The product had a weight ratio of 2-functional to 3-functional components of 0.25:1.

D. Preparation of Epoxy Novolac

A portion of the novolac resin from Example 6-B, 425 grams was reacted with epichlorohydrin using the exact same ratios of reactants and conditions as described in Example 8-B. The product was a non-sintering, friable solid with a MSP of 86.0°C. The melt viscosity was 850 cps measured at 150°C. The product had an epoxide equivalent weight of 184.0. The wt. avg. M.W. was 1775, no. avg. M.W. 1203, with a polydispersity of 1.48. The average epoxide function¬ ality was calculated as 6.5. The ratio of 2-functional to 3-functional content was less than 0.25:1.

E. Preparation of Epoxy Novolac

A portion of the novolac resin from Example 6-C, 425.0 grams was reacted exactly as described in Example 9-D to give a friable solid resin with an epoxide equivalent weight of 184.6. The wt. avg. M.W. was 1,789, no. avg. M.W. 1,187, with a polydispersity of 1.41. The average epoxide functionality was calculated as 6.4. The 2-functional content was 0.73 percent by weight and the weight ratio of 2-functional to 3-functional content was less than 0.25:1.

F. Curing of Epoxy Novolac Resin

A portion of the resin from Example 6-E, 35.0 grams was mixed at 150°-160°C with 6.93 grams of sulfanilamide and 0.2 ml of a 70 wt. percent solution of ethyltriphenylphosphonium acetate-acetic acid complex in methanol. After curing for 16 hours (57,600 s) at 150°C, 2 hours (7200 s) at 200°C, and 2 hours (7200 s) at 225°C, the product had a Tg greater than 255°C.

G. Curing of an Epoxy Novolac Resin with a Novolac Resin

A portion of the resin from Example 6-E, 30.0 grams was mixed at 150°-160°C with 16.9 grams of the phenolic novolac from Example 6-C, and 0.075 grams of 2-methylimidazole. The mixture was cured 16 hours (57,600 s) at 150°C, followed by 2 hours (7200 s) at

200°C and .2 hours (7200 s) at 225°C. The cured product had a Tg greater than 240°C as measured by DSC. H. Curing of Epoxy Novolac Resin

A portion of the resin from Example 6-E, 10.0 grams was mixed with 2.68 grams of methylenedianiline at 150°C and treated exactly as described in Example 2-D. The Tg via TMA was 311.8°C.

COMPARATIVE RUN C

A. Preparation of Epoxy Novolac Resin

A portion of the resin from Example 6-A, 104 grams was dissolved in 462.5 grams of epichlorohydrin and 2.3 grams of 60 percent aqueous benzyltrimethyl- ammonium chloride solution added. This solution was stirred under a nitrogen atmosphere for 72 hours (259,200 s) at 70°C, then cooled to 20°C, and 312.5 grams of a 16 percent solution of sodium hydroxide/9 percent sodium carbonate and stirred at 20°C for 90 minutes (5400 s). The aqueous layer separated, and an additional 312.5 grams of 16 percent sodium hydroxide/9 percent sodium carbonate solution and stirred for 30 minutes (1800 s) at 20°C. The aqueous layer was separated, and the organic layer washed with water until free of salt and caustic. The excess epichloro¬ hydrin was then removed via vacuum distillation at 150°C. The product had an epoxide content of 24.9 percent (an epoxide equivalent weight of 172.7). The 2-functional content was 13.4 percent. The wt. avg. M.W. was 1,531 and the no. avg. M.W. was 729, with a polydispersity of 1.71. The average epoxide functionality was calculated as 4.2. The ratio of 2-functional to 3-functional components was 1.30.

B. Solvent Extraction of Epoxy Novolac Resin

The procedure described in U.S. 3,928,288 was duplicated using 80.0 grams of the resin prepared in Comparative Run C-A. C. Curing of an Epoxy Novolac Resin with a Phenolic Novolac Resin

The procedure described in Comparative Run B-D was repeated using the phenolic novolac resin described in Example 6-B. The cured product had a Tg of 195.4°C.

D. Curing of Epoxy Novolac Resin

A portion of the resin from Comparative Run C-A, 10.0 grams was reacted with 2.86 grams of methylenedianiline exactly as described in Example 2-D. The cured resin had a Tg of 284.2 as measured by TMA.

E. Curing of Epoxy Novolac Resin

A portion of the resin from Comparative Run C-B, 10.0 grams was reacted with 2.41 grams of methylenedianiline as described in Example 2-D. The cured resin had a Tg of 302.5 as measured by TMA.

F. Curing of an Epoxy Novolac Resin with a Phenolic Novolac Resin

The procedure described in Comparative Run B-D was repeated using the phenolic novolac resin described in Example 6-A. The cured product had a Tg of 166.6°C.

Claims

1. An epoxy novolac resin having an average epoxide functionality of from 3 to 12 represented by the formula

wherein A is independently a divalent hydrocarbon group ^•having from 1 to 14 carbon atoms; each R is independ¬ ently hydrogen, a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9 carbon atoms; each R' is independently hydrogen or an alkyl group having from 1 to 4 carbon atoms, and n has an average value of from 1 to 10, with the provisos that (a) when 2-func¬ tional and 3-functional components are present and R is hydrogen, then the weight ratio of the 2-functional component to the 3-functional component is less than 1.1:1; (b) when 2-functional and 3-functional compon¬ ents are present and each R is independently a halogen atom, a hydroxyl group or a hydrocarbon group having fro 1 to 9 carbon atoms, then the weight ratio of the 2-functional component to the 3-functional component is less than 0.5:1; (c) when the average epoxide function¬ ality is from 3 to about 5, the resin contains less than 12.5 percent by weight of the 2-functional compon¬ ent; and (d) when the average epoxide functionality is from about 5 to 12, the resin contains less than 9 percent by weight of the 2-functional component.

2. The epoxy novolac resin of Claim 1 with the provisos that (a) when 2-functional and 3-functional components are present and R is hydrogen, then the weight ratio of the 2-functional component to the 3-functional component is less than 0.75:1; (b)^' when 2-functional and 3-functional components are present and each R is independently a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9 carbon atoms, then the weight ratio of the 2-functional com¬ ponent to the 3-functional component is less than 0.5:1; (c) when the average epoxide functionality is from 3 to about 5, the resin contains less- than 7 percent by weight of the 2-functional component; and (d) when the average epoxide functionality is from about 5 to 12, the resin contains less than 5 percent by weight of the 2-functional component.

3. The epoxy novolac resin of Claim 2 with the proviso that when 2-functional and 3-functional components are present and R is hydrogen, the weight ratio of the 2-functional component to the 3-functional component is less than 0.5:1.

4. A process for preparing a novolac resin represented by the formula

wherein A is independently a divalent hydrocarbon group having from 1 to 14 carbon atoms, each R is independ¬ ently hydrogen, a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9 carbon atoms, and n has an average value of from 1 to 10, having reduced quantities of 2-functional component, which process comprises

(I) reacting in the presence of a suitable catalyst

(A) a material having at least one aromatic hydroxyl group per molecule with

(B) an aldehyde at a molar ratio of (B):(A) of from 0.3:1 to 0.95:1;

(II) removing the excess aromatic hydroxyl- -containing material; and (III) subjecting the product from step (II) to extraction with water until the resultant product contains less than 25 percent by weight of 2-functional component than was present after step II.

5. The process of Claim 4 wherein

(i) said material having an average of at least one aromatic hydroxyl group is represented by the formula

(III)

wherein each R is independently hydrogen, a halogen atom, a hydroxyl group or a hydrocarbon group having from 1 to 9 carbon atoms; and (ii) said aldehyde is an aliphatic, cycloali- phatic or aromatic aldehyde having from 1 to 14 carbon atoms.

6. The process of Claim 5 wherein (i) said material having at least one aromatic hydroxyl group per molecule is phenol, methylphenol, butylphenol, bromophenol, chlorophenol, resorcinol or mixture thereof; (ii) said aldehyde is formaldehyde; (iϋ) said catalyst is oxalic acid; and

(iv) the resultant product containing less than 50 percent by weight of the 2-func¬ tional component than was present after step (II).

7. The process of Claim 6 wherein said material having at least one aromatic hydroxyl group per molecule is phenol.

8. The process of Claim 4 wherein in step (III), a minor amount of at least one organic solvent selected from ketones, alcohols and glycol ethers is employed with the water.