A HALOGENATED DIHYDRIC PHENOL AND IMPREGNATED

SUBSTRATES AND LAMINATES PREPARED THEREFROM

The present invention pertains to curable compositions containing polyglycidyl ethers of a poly- phenol and halogenated bisphenols.

Compositions containing glycidyl ethers of bisphenols and halogenated bisphenols have been employed in the preparation of electrical laminates. However, they are usually lacking in one or more properties such as, for example, thermal performance, moisture resistance and high temperature mechanical strength.

The present invention provides a curable compo¬ sition which results in cured compositions having an improvement in one or more of the properties selected from thermal stability, glass transition temperature, elevated temperature mechanical strength, moisture resistance, chemical resistance and toughness.

The present invention pertains to a curable composition characterized by comprising (A) at least one of

(1) at least one epoxy resin represented by formula I, II, III, IV, V or VI wherein each A and A' is independently a divalent hydrocarbyl group having from 1 to 12 carbon

0 0 0

II II II atoms , -S- , -S-S- , -S- , -S- , -C- or -0- ;

II

10 0 preferably each A is independently a divalent hydrocarbyl group having from 1 to 6 carbon atoms and each A' is independently a divalent hydrocarbyl 15 group having from 1 to 4 carbon atoms; each B is represented by the formula

each B ^* is represented by the formula

each B" is represented by the formula

each R is independently hydrogen or an alkyl group having from 1 to 4 carbon atoms; each is independently hydrogen ³⁵ or a hydrocarbyl group having from 1 to

10 carbon atoms; each R ^* is independently

hydrogen, a hydrocarbyl or hydrocarbyloxy group having from 1 to 10 carbon atoms or a halogen; m has a value of n-1; m' has a value of n'-l; m" has a value of n"-l; 5 each n, n' and n" independently has a value from zero to 3; preferably n is 1; g has a value from zero to 4, preferably from 0.1 to 2 and more preferably from 0.5 to 1.5; each y independently has an 10 average value from 1 to 5; y' has an average value of from zero to 3 and each z and z' independently has a value from zero to 3; (2) the reaction product of 15 (a) at least one epoxy resin represented by formula (I) as defined in component (A-l); and (b) at least one dihydric phenol represented by formulas VII or VIII 20 wherein A is a divalent hydrocarbon group having from 1 to 12 carbon

0 0 0

II II II atoms, -S-, -S-S-, -S-, -S-, -C- or

25 "

^Δ 0

-0-; each Y is independently hydrogen, a halogen or a hydrocarbyl or hydro¬ carbyloxy group having from 1 to 10

30 carbon atoms; and n has a value of zero or 1; and wherein components (a) and (b) are present in quantities such that the ratio of phenolic hydroxyl groups to epoxide groups is

³⁵ from 0.01:1 to 0.5:1, preferably from

0.05:1 to 0.25:1, most preferably from 0.1:1 to 0.2:1; or

(3) mixtures thereof; and (B) at least one halogenated dihydric phenol represented by formulas IX or X wherein A is a divalent hydrocarbyl group having from 1 to 12, preferably from 1 to 6

0 0 0

II II II carbon atoms, -S-, -S-S-, -S-, -S-, -C- or

II

O

-0-; each X is a halogen, preferably bromine; each Y is independently hydrogen, a halogen or a hydrocarbyl or hydrocarbyloxy group having from 1 to 10 carbon atoms; and n has a value of zero or 1; and wherein components (A) and (B) are present in quantities such that the ratio of phenolic hydroxyl groups to epoxide groups is from 0.7:1 to 1.1:1, preferably from 0.85:1 to 1:1, most preferably from 0.9:1-to 0.95:1.

Optionally, the composition additionally comprises

(C) a catalytic quantity of at least one catalyst for effecting the reaction between components (A) and (B); and (D) from zero to 50, preferably from 10 to 45, most preferably from 30 to 40, percent by weight based on the combined weight of components (A), (B), (C) and (D) of at least one solvent.

The present invention also pertains to substrates impregnated with the aforementioned compo¬ sitions and to laminates prepared therefrom.

FORMULA I

-C- By

FORMULA IV

Q Q

B-C-C-B

I I

B B

FORMULA V

H

B- ?C- ?C-B'.-O- ?C- ?C- ?C-O-B'.- ?C- ?C-B

I t I I I I I

B B H R H B B

FORMULA VI

^• *#

Particularly suitable epoxy resins which can be employed herein include, for example, the trigly- cidyl ether of tris(hydroxyphenyl)methane, higher molecular weight homologs thereof, trisepoxides advanced with dihydric phenols, phenol-formaldehyde epoxy novolac resins, cresol-for aldehyde epoxy novolac resins, resorcinol-formaldehyde epoxy novolac resins, phenol-glyoxal epoxy novolac resins, and mixtures thereof.

Particularly suitable dihydric phenols and halogenated dihydric phenols include, for example, bisphenol A, tetrabromobisphenol A, bisphenol S, tetra¬ bromobisphenol S, biphenol, tetrabromobiphenol, tetra- bromodihydroxybenzophenone, resorcinol, tetrabromo- resorcinol, and mixtures thereof.

Multifunctional phenolic compounds, those having an average functionality of greater than 2, can be employed in this invention together with the dipheno- lic compounds, if desired, so as to change the cure behavior of the composition. Particularly suitable multifunctional phenolic compounds include, for example, phenol-formaldehyde condensation products having an average functionality of from 3 to 8, phenol-hydroxy- benzaldehyde condensation products having an average functionality of from 3 to 7 and cresol-formaldehyde condensation products having an average functionality of from 3 to 8.

Suitable catalysts for effecting the reaction between the epoxy resin and the phenolic hydroxyl- -containing compound include, for example, those disclosed in U.S. Patents 3,306,872; 3,341,580; 3,379,684; 3,477,990; 3,547,881; 3,637,590; 3,843,605;

3,948,855; 3,956,237; 4,048,141; 4,093,650; 4,131,633; 4,132,706; 4,171,420; 4,177,216; 4,302,574; 4,320,222; 4,358,578; 4,366,295; and 4,389,520.

Particularly suitable catalysts are those quaternary phosphonium and ammonium compounds such as, for example, ethyltriphenylphosphonium chloride, ethyl- triphenylphosphonium bromide, ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium acetate, ethyltri¬ phenylphosphonium diacetate (ethyltriphenylphosphonium acetate* cetic acid complex), ethyltriphenylphosphonium tetrahaloborate, tetrabutylphosphonium chloride, tetra¬ butylphosphonium acetate, tetrabutylphosphonium diacetate (tetrabutylphosphonium acetate-acetic acid complex), tetrabutylphosphonium tetrahaloborate, butyltriphenyl- phosphonium tetrabromobisphenate, butyltriphenylphosphon¬ ium bisphenate, butyltriphenylphosphonium bicarbonate, benzyltrimethylammonium chloride, benzyltrimethylammonium hydroxide, benzyltrimethylammonium tetrahaloborate, tetrameth 1ammonium hydroxide, tetrabutylammonium hydroxide, tetrabutylammonium tetrahaloborate, and mixtures thereof.

The catalyst, when used, is employed in any suitable catalytic quantity; however, the preferred quantity is from 0.001 to 10, more preferably from 0.05 to 5, percent by weight based upon the weight of the reactants.

Other suitable catalysts include tertiary amines such as, for example, triethylamine, tripropyl- a ine, tributylamine, 2-methylimidazole, benzyldimethyl- amine, and mixtures thereof.

Other suitable catalysts include ammonium compounds such as, for example, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, triethylammonium tetrahaloborate, tributyl- ammonium chloride, tributylammonium bromide, tributyl- ammonium iodide, tributylammonium tetrahaloborate, N,N'-dimethyl-l,2-diaminoethane--tetrahaloboric acid complex, and mixtures thereof.

Other suitable catalysts include quaternary and tertiary ammonium phosphonium, and arsonium adducts or complexes with suitable non-nucleophilic acids such as, for example, fluoboric, fluoarsenic, fluoantimonic, fluophosphoric, perchloric, perbromic, periodic, and mixtures thereof.

Suitable solvents which can be employed herein include, for example, ketones, alcohols, glycol ethers and amides, such as, for example, acetone, methyl ethyl ketone, methanol, propylene glycol mono methyl ether and dimethyl formamide.

The compositions of the present invention may also contain, if desired, stabilizers, pigments, dyes, mold release agents, flow control agents, reinforcing agents, fillers, fire retardant agents, rubber modifiers, surfactants, accelerators, reactive diluents, and mixtures thereof.

Suitable stabilizers which can be employed herein include, for example, those represented by the formula

wherein each R ¹ is independently hydrogen, a hydrocarbyl group having from 1 to 10 carbon atoms or a halogen and R ² is a hydrocarbyl group having from 1 to 10 carbon atoms.

0 Particularly suitable stabilizers include, for example, methyl p-toluene sulfonate, ethyl p-toluene sulfonate, methyl chlorobenzene sulfonate, and combina¬ tions thereof. Preferably the stabilizer is methyl p-toluene sulfonate.

5 The stabilizer component, when used, is employed in any suitable stabilizing quantity; however, the preferred quantity is from 0.001 to 10, more prefer¬ ably from 0.01 to 2, percent by weight based upon the weight of the epoxy resin component.

0 The compositions of the present invention are suitable for such applications as impregnating substrates and as coatings, adhesives, castings, moldings, electronic encapsulations and in potting compositions.

5 Suitable substrates which can be employed herein include, for example, fibers or filaments in woven, matt or non-woven form of glass, carbon, graphite, synthetic fibers, quartz, and combinations thereof. The impregnated substrates can be cured employing conditions known in the art.

Structural or electrical laminates or composites can be prepared from one or more layers of cured impregnated substrates or a combination of substrates. The electrical laminates usually have at least one external layer of an electrically conductive material. The electrically conductive material is preferably copper.

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

Fracture Toughness Measurement (G,-,)

The method for measuring G _lc (fracture toughness 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 as 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 . This is then combined with the tensile modulus and Poisson's ratio

for the material to give the value for G _lc , usually reported in ergs/cm ² x 10 ⁶ or kJ/m ² . 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.

The Tg was determined by Differential Scanning Calorimetry using a calibrated DuPont Instrument (Model No. 912 with a 1090 controller). Samples were run under a nitrogen atmosphere with a heat-up rate of 10°C per min. (0.1667°C/sec. ) .

Coefficient of thermal expansion (CTE) was determined using a calibrated DuPont Thermal Mechanical Analyzer (Model No. 943 with a 1090 controller).

Decomposition properties were determined using a DuPont Thermal Gravimetric Analyzer (Model No. 951 with a DuPont 1090 controller).

Dynamic mechanical properties were measured on a DuPont Dynamic Mechanical Analyzer (Model No. 982 with a DuPont 1090 controller).

The following components were employed in the Examples and Comparative Experiments.

Epoxy Resin A was a polyglycidyl ether of a phenol-hydroxybenzaldehyde condensation product having an EEW of 220 and an average functionality of 3.5.

Epoxy Resin B was a polyglycidyl ether of a phenol-hydroxybenzaldehyde condensation product having an EEW of 162 and an average functionality of 3.2.

Epoxy Resin C was an advanced epoxy resin made by advancing Epoxy Resin B with tetrabromobis¬ phenol A to an EEW of 215.

Epoxy Resin D was a polyglycidyl ether of a phenol-hydroxybenzaldehyde condensation product having an EEW of 204 and an average functionality of 3.4.

Epoxy Resin E was an advanced epoxy resin made by advancing Epoxy Resin B with tetrabromobis¬ phenol A to an EEW of 239.

Epoxy Resin F was a polyglycidyl ether of a dimethyl phenol-hydroxybenzaldehyde condensation product having an EEW of 185 and an average functionality of 3.

Epoxy Resin G was a polyglycidyl ether of a dimethyl phenol-dimethylbenzaldehyde condensation product having an EEW of 189 and an average function¬ ality of 3.

Epoxy Resin H was a phenol-formaldehyde epoxy novolac resin having an average functionality of 3.6 and an EEW of 178.

Epoxy Resin I was a phenol-formaldehyde epoxy novolac resin having an average functionality of 5.6 and an EEW of 203.

Epoxy Resin J was a brominated phenol- -formaldehyde epoxy novolac resin having an average functionality of 3.5, an EEW of 285 and a total percent bromine of 36.

Epoxy Resin K was a cresol-formaldehyde epoxy novolac resin having an average functionality of 3.5 and an EEW of 211.

Epoxy Resin L was a cresol-formaldehyde epoxy novolac resin having an average functionality of 5 and EEW of 211.

Epoxy Resin M was a cresol-formaldehyde epoxy novolac resin having an average functionality of 7.5 and an EEW of 210.

Epoxy Resin N was a phenol/glyoxal epoxy novolac resin having an average functionality of 4.2 and an EEW of 231.

EXAMPLE 1

56.87 Grams (0.209 equiv.) of tetrabromobis- phenol A (TBBPA) was stirred into 50 grams (0.227 equiv.) of Epoxy Resin A at 150°C until the TBBPA had completely dissolved (about 180 seconds). Then 0.214 g of a 70 percent methanol solution of tetrabutylphosphonium acetate•acetic acid complex was added and mixed. The solution was then degassed. The resultant mixture was then poured into an aluminum mold which had been treated with Fluoroglide release agent and which had been preheated to about 175°C. The mold was clamped together at 1/8" (3.175 mm) spacing. The filled mold was then placed in a 200°C oven for 2 hours (7200 s). After cooling to room temperature, the casting was removed and physical properties obtained. The results were as follows:

G _lc = .51 kJ/m ²

Tg = 180°C coefficient of thermal expansion below 100°C was 65 ppm/°C.

EXAMPLE 2

A. VARNISH FORMULATION

2917 grams (9.944 equiv.) of a 75 percent solution of the trisepoxide employed in Example 1 in methyl ethyl ketone; 4048 grams (8.929 equiv.) of a 60 percent solution of TBBPA in methyl ethyl ketone; 3.3 grams of 2-methyl imidazole; and 200 grams of acetone.

The above mixture had a viscosity of 21 seconds measured in a No.. 2 Zahn cup at 75°F (23.9°C).

B. PREPARATION OF PREIMPREGNATED SUBSTRATE

Burlington style 7628 glass cloth with an 1617 finish was impregnated with the varnish formulation of Example 2-A in a forced air vertical treater having a total length of 26 feet (7.9 meters) with the first 19.5 feet (5.9 meters) heated to 350°F (176.7 °C) at a rate of 12 feet per min. (61 mm/sec). The resin contained in the impregnated glass cloth had a 73 second gel time at 171°C. The resultant impregnated glass cloth had a resin content of 47 percent by weight.

C. PREPARATION OF LAMINATE

Both unclad (no copper) and one sided copper clad, 0.062" (1.57 mm) thick laminates were pressed from aforementioned prepreg. Eight 12 inch by 12 inch (304.8 mm x 304.8 mm) plies were pressed into laminate form. The copper foil was a 1 ounce zinc oxide treated

aterial. The laminates were pressed in a preheated Wabash press at 350°F (176.7°C) and 500 psi (3.45 MPa) for 1 hour (3600 s). There was no post-cure.

The unclad laminate had the following properties.

1. Tg = 180°C.

2. Dynamic decomposition temperature was 314°C (run at 3°C/min., 0.05°C/sec. ).

3. Decomposition stability at 250°C over a 60 in. (3600 s) period was excellent.

4. Z-axis coefficient of thermal expansion was 46.7 (ppm/°C (_<i)).

5. Maintained 95 percent of original storage modulus up to 157°C. 6. The relative moisture resistance was deter¬ mined by placing 3 2" x 4" (50.8 x 101.6 mm unclad laminate coupons in a pressure pot at 15 psi (103 kPa) steam pressure for 2 hours (7200 s). After 2 hours (7200 s), the com- pounds were removed, externally dried and dipped in molten solder at 500°F (260°C) for 20 seconds. Each side of the 3 coupons was then inspected for any delamination blisters. The results were reported as No. of sides with no blisters divided by total No. of sides. This system had a perfect 6/6 or 100 percent passed.

The clad laminate had a copper peel strength of 4 to 4.8 lbs/in (700 to 841 N/m).

EXAMPLE 3

A. VARNISH FORMULATION

A varnish formulation was prepared from the following. 2532 grams (8.833 equiv.) of a 75 percent solution of Epoxy Resin C in methyl ethyl ketone; 3808 grams (8.40 equiv.) of a 60 percent solution of TBBPA in methyl ethyl ketone; 8.55 grams of ethyltriphenylphosphonium acetate

The above mixture had a viscosity of 20 seconds measured in a No. 2 Zahn cup at 75°F (23.9°C).

B. PREPARATION OF PREIMPREGNATED SUBSTRATE Burlington style 7628 glass cloth with an 1617 finish was impregnated with the varnish formulation of Example 3-A in a forced air vertical treater having a total length of 26 feet (7.9 meters) with the first 19.5 feet (5.9 meters) heated to 350°F (176.7°C) at a rate of 10 feet per min. (50.8 mm/sec). The resin contained in the impregnated glass cloth had a 97 second gel time at 171°C. The resultant impregnated glass cloth had a resin content of 44.4 percent by weight.

C. PREPARATION OF LAMINATE Laminates, both unclad and one sided copper clad, were prepared in the same manner described in Example 2-C.

The unclad laminate had the following properties:

1. Tg = 184°C

2. the relative moisture resistance was determined in the same manner noted in Example 2, property no. 6. This system had a perfect 8/8 or 100 percent pass for 4 coupons.

The clad laminate had a copper peel strength of 4.8 to 5.6 lbs/in (841 to 981 N/m).

EXAMPLES 4-16

These examples were prepared in a manner similar to Example 1 employing the components and conditions of the following Table I. The properties of the resultant product are also given in the Table I.

TABLE I

COMPONENTS,

CONDITIONS

AND RESULTS EXAMPLE 4 EXAMPLE 5 EXAMPLE 6 EXAMPLE 7

Epoxy Resin, type/grams/equiv. D/5.013/0.0246 D/5.050/0.0248 B/7.482/0.462 E/5.447/0.0288

Tetrabromobisphenol A, grams/equiv. 6.682/0.0246 6.733/0.0248 12.562/0.0462 6.204/0.0228

Catalyst, type/grams BDMAV0.015 None BDMA/0.22 BDMA/0.016

Mixing Conditions, °C/sec. 175/120 175/120 175/120 175/120

Curing Conditions ³ , °C/sec. 180/3600 180/3600 180/3600 180/3600 225/9000 225/9000 225/9000 225/9000

Tg, 189.4 175 178 178

¹ BDMA is benzyldimethylamine (10 percent solution in methanol)

² TBPA is a 70 percent solution of tetrabutylphosphonium acetate*acetic acid complex in methanol ³ After mixing, the clear resin system was poured into a small aluminum mold for curing

TABLE I (Cont. )

COMPONENTS,

CONDITIONS

AND RESULTS EXAMPLE 8 EXAMPLE 9 EXAMPLE 10 EXAMPLE 11

Epoxy Resin, type/grams/equiv. F/5.819/0.0315 G/5.176/0.0273 H/6.178/0.0347 1/5.384/0.0265

Tetrabromobisphenol A, grams/equiv. 8.574/0.0315 7.433/0.0273 9.441/0.0347 7.214/0.0265

Catalyst, type/grams BDMA/0.017 BDMA/0.015 BDMA/0.019 BDMA/0.016

Mixing Conditions, °C/sec. .175/120 175/120 175/120 175/120

Curing Conditions ³ , °C/sec. 180/3600 180/3600 180/3600 180/3600 225/9000 225/9000 225/9000 225/9000

Tg, 180 191 153 160

¹ BDMA is benzyldimethylamine (10 percent solution in methanol)

² TBPA is a 70 percent solution of tetrabutylphosphonium acetate-acetic acid complex in methanol ³ After mixing, the clear resin system was poured into a small aluminum mold for curing

TABLE I (Cont. )

COMPONENTS, CONDITIONS AND RESULTS EXAMPLE 12 EXAMPLE 13 EXAMPLE 14

Epoxy Resin, type/grams/equiv. J/5.039/0.0177 K/5.595/0.0265 L/5.359/0.0254

Tetrabromobisphenol A, grams/equiv. 4.807/0.0177 7.206/0.0265 6.897/0.0254

Catalyst, type/grams BDMA/0.015 BDMA/0.017 BDMA/0.017

Mixing Conditions, °C/sec. 175/120 175/120 175/120

Curing Conditions ³ , °C/sec. 180/3600 180/3600 180/3600 225/9000 225/9000 225/9000

Tg, 178 161 166

¹ BDMA is benzyldimethylamine (10 percent solution in methanol)

² TBPA is a 70 percent solution of tetrabutylphosphonium acetate*acetic acid complex in methanol ³ After mixing, the clear resin system was poured into a small aluminum mold for curing

TABLE I (Cont. )

COMPONENTS, CONDITIONS AND RESULTS EXAMPLE 15 EXAMPLE 16

Epoxy Resin, type/grams/equiv. M/4.970/0.0236 N/5.045/0.0218

Tetrabromobisphenol A, grams/equiv. 5.943/0.0218 5.938/0.0218

Catalyst, type/grams TBPA ² /0.22 BDMA/0.015

Mixing Conditions, °C/sec. 175/120 175/120

Curing Conditions ³ , °C/sec. 180/3600 180/3600 225/9000 225/9000

Tg, 178 184

^{■■^} BDMA is benzyldimethylamine (10 percent solution in methanol)

² TBPA is a 70 percent solution of tetrabutylphosphonium acetate•acetic acid complex in methanol ³ After mixing, the clear resin system was poured into a small aluminum mold for curing

EXAMPLE 17

A formulation was made consisting of 100 g (0.4545 equiv.) of Epoxy Resin A, 114 g (0.41829 equiv.) of tetrabromobisphenol A and 110 g of methyl ethyl ketone. The resin solution was studied to determine its stability at 25°C and at 50°C. The stability was related to changes in the percent epoxide over a period of time. Also, methyl-p-toluene sulfonate was added to portions of the solution to determine its effects to the stability of the resin system. The results are given in Table II.

TABLE II

STABILITY AT 25°C (NO STABILIZER)

Time % Epoxide

0 6.3 2 days (172,800 s) 6.2

27 days (2,332,800 s) 6.0

90 days (7,776,000 s) 5.6

STABILITY AT 50°C (NO STABILIZER)

Time % Epoxide 0 - 6.3

2 days (172,800 s) 6.1

27 days (2,332,800 s) 4.8

90 days (7,776,000 s) Gelled

STABILITY AT 50°C (WITH STABILIZER*)

Time % Epoxide

0 6.3

2 days (172,800 s) 6.2

27 days (2,332,800 s) 6.1

90 days (7,776,000 s) 5.6

240 days (20,736,000 s) 4.9

*0.1 g of methyl-p-toluene sulfonate was added to 40 g of resin solution