Background Of The Invention

1. Field of the Invention

The invention relates to certain novel blends of phenolic cyanate-phenolic triazine copolymers and epoxy resins, as well as to articles prepared from said blends. More particularly, the invention relates to such blends which have improved properties.

2. Prior Art

Phenolic resins are a class of synthetic materials which greatly vary in molecular structure. Therefore, a multitude of applications for these products exists as a result of the array of physical properties that arise from the synthetic options. However, phenolics disadvantageously exhibit less than desirable thermal oxidative stability and produce an extensive, uncontrollable amount of volatile by¬ products during cross-linking. In order to obviate certain of the disadvantages attendant to phenolics, U.S.

Patent No. 4,970,276 proposed a modified multifunctional phenolic cyanate/phenolic triazine copolymer ("PT resin") which had greater oxidative, mechanical, and thermal stability as compared to conventional phenolic resins, and did not produce volatile by-products during crosslinking. Further, these PT resins possessed better elongation properties and higher glass transition temperatures than the conventional phenolic resins. Additional examples of such PT resins are described in U.S. Patent Nos. 4,970,276, 4,978,727, and 5,126,412.

Another approach for producing thermosettable blends having improved mechanical properties is by blending dicyanate esters with epoxy resins as

disclosed in U.S. Patent Nos. 4,612,359, 4,506,603, 4,477,629, 4,546,131, 4,487,915, and 3,562,214, and in Shimp, et al., "Co-Reaction of Epoxide and Cyanate Resins," 33rd Int'l SAMPE Symposium and Exhibition 1 - 13 (Calif. March 7 - 10, 1988) and Shimp, AroCy* Cyanate Ester Resins Chemistry, Properties & Applications, (3rd Ed. May, 1991). These blends have been useful in the production of base materials for printed circuits as disclosed in Patent Nos. DE 4,022,255, DD 290,844, DE 4,125,420, and DE 4,224,835.

Although the above inventions provide thermosettable resin blends which, when cured, possess excellent thermal stability and mechanical properties, there is room for additional improvement in the overall mechanical properties, especially in glass transition temperature, as well as in water absorption.

It would be desirable to provide a thermosettable resin blend which, when cured, is superior to prior art phenolic resins and dicyanate blends in one or more of the properties selected from glass transition temperature, flexural strength, flexural modulus, elongation, and water absorption.

Summary Of The Invention

In accordance with this invention, there is provided a blend comprising: a) a multifunctional phenolic cyanate/phenolic triazine copolymer

comprising three or more phenolic moieties of formula I:

linked by way of at least one of the open valences to one or more triazine moieties of the formula II:

II and wherein the remainder of the open valences of said phenolic moieties are substituted with -OH, -OCN, or other triazine moieties, provided that at least one of said remaining open valences is substituted with a -OCN moiety; wherein: n is a positive whole number equal to or greater than 1; q and r are the same or different at each occurrence and are whole numbers from 0 to 3 with the proviso that the sum of q and r at each occurrence is equal to 3; o and p are the same or different at each occurrence and are whole numbers from 0 to 4, with the proviso that the sum of o and p is equal to 4;

-X- is a divalent organic radical; and

R ₃ is the same or different at each occurrence and is a substituent other than hydrogen which is unreactive under conditions necessary to completely cure the copolymer; and b) an epoxy resin.

Another aspect of the invention pertains to the article resulting from curing

the aforementioned blend with a curing quantity of a curing agent, catalyst or mixture of curing agent and catalyst therefor.

The blend of the invention and the products resulting therefrom exhibit one or more beneficial properties, such as, improved glass transition temperature and water absorption.

Description Of The Preferred Embodiments Component a of the present invention includes multifunctional phenolic cyanate/phenolic triazine copolymer resins or "PT resins" having at least three phenolic moieties of the formula I linked by at least one of said open valences to one or more triazine moieties of the formula II. The remainder of said open valences being substituted with -OCN, -OH or other triazine moieties, provided that at least one of said remaining open valences is substituted with a -OCN group, wherein R ₃ , n, q, r, o, p, and X are as described above.

In the structure of formula I, R ₃ is an inert substituent. Illustrative of suitable R ₃ groups are such inert substituents as halo, trihalomethyl, alkyl, alkoxy, phenyl, and the like.

In the structure of formula I, -X- is a divalent organic radical. Illustrative of suitable -X- groups are alkylene such as methylene, ethylmethylene, 2- ethylpentylmethylene, methylmethylene, isopropylmethylene, isobutylmethylene, pentylmethylene, furylmethylene, and the like; arylenes such as 1,3- benzenedimethylene, phenylmethylene, 1,4-benzenedimethylene, 2,2-bis-(4- phenylene)propane, 4,4-diphenylene dimethylenethane and the like; and cycloalkylenes such as cyclohexylene, cyclooctylene, 1,3-cyclohexanedimethylene,

and the like.

In the preferred embodiments of the invention:

-X- is a substituted or unsubstituted methylene or 1,4-benzenedimethylene wherein permissible substituents are alkyl or furyl; q and r are the same or different at each occurrence and are positive whole numbers from 0 to 3, with the proviso that the sum of q and r is 3;

R ₃ is alkyl; n is from 1 to about 20; and o and p are the same or different at each occurrence and are positive whole numbers from 0 to 4, with the proviso that the sum of o and p is 4; wherein up to about 30 mol percent of the phenyl moieties of said copolymer are substituted with said triazine moieties, up to about 90 mol percent of said phenyl moieties are substituted with -OH groups and up to about 90 mol percent of said phenyl moieties are substituted with -OCN groups, said mol percent being based on the total mols of phenyl groups in said copolymer. Unless indicated otherwise, all references herein are in terms of weight percent.

Among the preferred embodiments of the invention, particularly preferred are those embodiments of the invention in which: from about 2 to about 25 mol percent of said phenyl groups of the PT resin are substituted with triazine moieties, from about 40 to about 90 mol percent of said phenyl groups are substituted with -OCN groups and from about 2 to about 50 mol percent of said phenyl groups are substituted with -OH groups, said mol percent based on the total mols of phenyl group in said copolymer;

-X- is methylene, methylene substituted with alkyl having from about 1 to about 10 carbon atoms, halo or furfuryl, or xylene;

R ₃ is methyl or ethyl; o is 0 or 1; n is from about 1 to about 10; q is 0 or 1; r is 2 or 3; p is 3 or 4.

Among these particularly preferred embodiments, most preferred are those embodiments wherein: n is 3 to about 10; from about 5 to about 20 mol percent of the phenyl groups of the phenyl triazine/phenyl cyanate copolymer are substituted with -OCN groups and from about 5 to about 20 mol percent of said phenyl groups are substituted with -OH groups, said mol percent being based on the total mols of phenyl groups in said copolymer; q is 0;

or

r is 3; and p is 4.

Especially good results are obtained in the practice of the invention where

from about 10 to about 20 mol percent of the phenyl groups in the PT resin are substituted with triazine moieties, from about 10 to about 20 mol percent of said phenyl groups are substituted with -OH groups and from about 60 to about 80 mol percent of said phenyl groups are substituted with -OCN groups, said mol percent being based on the total mols of phenyl groups in said copolymer.

These especially preferred copolymers are preferably linear copolymers having recurring units of the formula HI:

wherein R ₃ , o, p, q, r, -X-, and n are as described above and wherein:

Z _j is -OH or -OCN at each occurrence; Z^ is a trivalent triazine moiety; with the proviso that from about 10 to about 20 mol percent of the phenyl groups of the copolymer are substituted with trivalent triazine moieties, from about 70 to about 75 mol percent of phenyl groups are substituted with -OCN groups, and from about 10 to about 20 mol percent of the phenyl groups are substituted with -OH groups, said mol percent based on the total mols of phenyl groups in the copolymer.

Suitable materials which can be employed in the preparation of the phenolic cyanate resin precursor to the PT resin of component a include phenolic salts of formula IV:

wherein R ₃ , q, r, o, p, n, and X are as described above, and V is hydrogen or a cation of an organic or inorganic base which is formed by reaction between said base and the protons of a phenol to form the corresponding basic salt, wherein the mol ratio of cations to hydrogen are sufficient to form the desired mol percent of - OCN groups in the desired phenolic cyanate.

These phenolic salts react with cyanogen halides via a nucleophilic displacement reaction in order to produce the phenolic cyanate resin precursor used in the preparation of the PT resins of component a, details of which are disclosed in U.S. Patent No. 4,970,276, which is incorporated by reference herein.

PT resins suitable for use in component a of the blend of the present invention may be prepared by the known method of controlled "polycyclotrimerization" of the phenolic cyanate precursor having formula V:

to the extent necessary to form the desired mol percent of trivalent triazine moieties, wherein R ₃ , n, q, r, o, p, Z and X are as described above, provided that the amount of Z _x group which are -OCN is sufficient to provide the desired mol percent of triazine moieties and -OCN moieties in the desired copolymer. Details of the method for PT resin production are also described in U.S. Patent No. 4,970,276.

Suitable epoxy resins for blending with the PT resin include bisphenol A based epoxy resins, halogenated epoxy resins, epoxy novolac resins, polyglycol epoxy resins, and mixtures and copolymers thereof. Illustrative of suitable bisphenol A based epoxy resins include compounds of the following formula:

CH

wherein the average value of m is from about 0J to about 1, preferably about OJ to about 0.2.

Illustrative of suitable epoxy novolac resins include compounds of the following formula:

9/1

wherein the average value of 1 is from about 0.1 to about 2, preferably about 0.1 to about 03.

Suitable halogenated epoxy resins include those epoxies substituted with chlorine, bromine, fluorine, and mixtures thereof. Illustrations of suitable brominated epoxy resins include compounds of the following formula:

10

wherein the average value of k is from about 2 to about 3, preferably about 2 to about 2.5. Uustrations of suitable polyglycol epoxy resins include compounds of the following formula:

10/1

wherein the average value of j is from about 1 to about 2, preferably about 1.9 to about 2.0, and R' is a hydrogen or an organic group, such as an alkyl group having from about 1 to about 5 carbons. These epoxy resins can be obtained from commercial sources, e.g., from The Dow Chemical Company. Other suitable epoxy resins include multifunctional epoxy resins, such as tetra- and tri-functional epoxy resins, which may be used alone, or mixed or copolymerized with the above-described epoxy resins. As used herein, "multifunctional epoxy resin" means a resin which may contain greater than about 1 to about 4, preferably 3 to about 4 epoxy groups, more preferably 4 epoxy groups. Illustrations of such tetra-functional and tri-functional multifunctional epoxy resins are

and

CH, CH - CH,

respectively, which can be obtained from commercial sources, e.g., from Ciba- Geigy Corporation under the tradename "Araldite".

11

In a preferred embodiment, an epoxy having, based upon the total weight of the epoxy resin, from about 15 percent to about 45 percent, preferably about 8 percent to about 12 percent, bromination is employed. Unless indicated otherwise, all references herein are with respect to weight percent. As the amount of brominated epoxy resin in the blend of the present invention is increased, various properties, such as adhesion and glass transition temperature ("T _g ") also increase.

In an alternative embodiment wherein a blend having a low viscosity is desired, the incorporation of a polyglycol epoxy resin is preferred. The blend of the present invention includes a mixture of, based upon the total weight of the blend, from about 5 to about 95 percent, preferably from about 15 to about 50 percent, and more preferably about 25 to about 30 percent PT resin with from about 5 to about 95 percent, preferably about 25 to about 70 percent, epoxy resin. The blend of the present invention may optionally contain, based upon the total weight of the blend, from about 0 to about 20, preferably about 3 to about 10 percent, of a multifunctional epoxy resin in addition to the amount of epoxy resin or resins employed in component b. Examples of suitable multifunctional epoxy resins include those described above. When a blend having high T _g and adhesion properties is desired, it is preferred that such multifunctional epoxy resins are used as a third component in the blend of the present invention.

The blend of the present invention may also optionally contain a catalyst for the purpose of increasing the cure rate of the blend. The amount of the

12

catalyst employed depends largely on the type of the catalyst, the curing conditions, and/or the use of the final cured product. Usually, the blend of the present invention contains, based upon the total weight of the blend, from about 0.01 percent to about 0.2 percent, preferably 0.08 percent to about 0J1 percent of a catalyst.

Suitable catalysts employed herein are the primary catalysts and/or the organic catalysts or "curing agents". Illustrations of the primary catalysts include, for example, transition metal salts of aliphatic and aromatic carboxylic acids, nitrogen and phosphorus compounds. Particularly suitable catalysts include, for example, lead naphthenate, manganese naphthenate, manganese octoate, manganic acetylacetonate, cobalt octoate, cobalt naphthenate, cobalt acetylacetonate, zinc octoate, zinc naphthenate, zinc acetylacetonate, copper acetylacetonate, cupric naphthenate, nickel acetylacetonate, titanyl acetylacetonate, ferric octoate, tin octoate, diazabicylo[2.2.2]octane, catechol, lJ-dimethyl-3-phenylurea, mixtures thereof and the like. Manganese octoate is most preferred. These catalysts are obtainable from commercial sources, e.g., from Aldrich Chemical Company, Inc., and Pfaltz & Bauer, Inc.

Other suitable catalysts include organic catalysts or curing agents, such as alkyl phenols, imidazoles and mixtures thereof. These organic catalysts or curing agents are employed for the purpose of further accelerating the cure, and may be used alone or in combination with the above-mentioned metal catalysts. Preferable organic catalysts may be selected from the group consisting of nonylphenol, 1-methyl-imidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,

13

and 2-methylimidazole ("2-MI"), with 2-MI being most preferred. These organic catalysts are also obtainable from commercial sources, e.g., from Aldrich Chemical Company, Inc.

In a preferred embodiment, based upon the total weight of the blend, from about 0.025% to about 0.06% of manganese octoate with about 0.06% to about

0.07% 2-MI may be employed.

If desired, the blend, i.e., the PT resin and/or epoxy resin component, can be blended with other compounds, such as solvents, fillers, mold release agents, pigments, dyes, flow modifiers, combinations thereof and the like. Examples of such compounds are described in U.S. Patent No. 4,496,695, which is incorporated herein by reference.

Suitable such solvents include, for example, aromatic hydrocarbons, ketones, halogenated hydrocarbons, combinations thereof and the like. Particularly suitable solvents include, for example, dimethylformamide, tetrahydrofuran, acetone, l-methyl-2-pyrrolidinone, methylethylketone, methylene chloride, combinations thereof and the like.

The PT resin and/or epoxy resin may contain fillers for use in where the structural strength and integrity of a structure has to be maintained, and for other purposes known to those of skill in the art. Any suitable filler known to those of skill in the art may be used. Such fillers may be selected from a wide variety of organic and inorganic materials such as polymers, minerals, metals, metal oxides, siliceous materials, and metal salts. Illustrative of useful fillers are kevlar fibers, rock-wool, slag wool, fiberglass, phenolic fibers, aramide, boron, and carbon fibers,

14

as well as plate-like, fibrous and paniculate forms of alumina, brass powder, aluminum hydrates, iron oxide, feldspar, lead oxides, asbestos, talc, barytes, calcium carbonates, clay, carbon black, quartz, novaculite and other forms of silica, kaolinite, aluminum silicate, bentonite, garnet, mica, saponite, baddeleyite, calcium oxide, fused silica, calcium hydroxide, synthetic fibers such as paper, pulp, wood flour, cotton, linter and polyimide fibers, and the like. Other useful fillers include thermoplastic polymers, as for example, polyesters, polyimides, polyamides, polysulfones, polyaramids, polyester carbonates, polyphenylene ether, polyethersulfones, polyethylene, polypropylene, polycarbonates, polyetherimides, polysulfides, polyacrylates, polyvinyls and the like. Methods for producing reinforced and/or filled blends include melt blending, extrusion and molding processes, simple mixing and dispersion of both materials in suitable medium by methods known in the art.

For coloring purposes, a curable resin blend of this invention may include white pigments such as titanium dioxide, and coloring pigments or various organic dyes and pigments, such as lead yellow, carbon black, iron black, molybdenium red, prussian blue, navy blue, cadmium yellow, and cadmium red.

The curable resin blends of the present invention may be prepared by either a wet process or a dry process, both of which are conventionally known in the art. Choice of the process is determined by the proportion of components and final use of the blend.

In the wet process, each component is individually dissolved in a solvent, then all of the components are blended so as to obtain a curable resin blend

15

having the desired proportion. Alternatively, at least one of the components is dissolved in a solvent, and the other components are added thereto. In view of the high viscosity of both the PT resin and epoxy, it is preferred that, when selecting the latter embodiment, at least these two components are initially dissolved in a solvent before other components are added thereto. Otherwise, it may be necessary to heat the PT resin-epoxy mixture to temperatures ranging from about 65°C to about 75°C in order to lower the viscosity and improve the mixing thereof, and thus reduce the likelihood of non-uniformities in the end product. The blends prepared according to the wet process contain a solvent or solvents. The solvent may be removed by heating the blend or by keeping the blend under a reduced pressure.

Solvents suitable for dissolving the components employed in the wet process include, for example, ketones, such as acetone, methyl ethyl ketone, and the like, as well as tetrahydrofuran, methylene chloride, dimethylformamide, l-methyl-2- pyrrolidinone, and the like.

According to the dry process, the PT resin and epoxy resin components are continuously mixed via conventional means at temperatures of about 65°C to about 75°C until homogeneous. An effective amount of a solution comprised of from about 15 to about 25 percent, based upon the total weight of the solution, of catalyst predissolved in an alkyl phenol solvent, such as nonylphenol, dodecylphenol, o-cresol, 2-sec-butylphenol and 2,6-dinonylphenol, most preferably nonylphenol, may optionally be added thereto such that the amount of catalyst in the homogeneously blended blend is from about 0.06 to about 0.07 percent, based

16

upon the total weight of the blend. The resulting blend is continuously stirred for about 20 minutes to about 1 hour until homogeneous.

Further details regarding both the wet process and the dry process are described in "Formulating with Dow Epoxy resins Electrical Laminates" by The Dow Chemical Company (Feb. 1990).

The method of curing the resin blend of this invention is not restricted in particular. Usually it is performed by heating. Generally a temperature of about 18°C to about 400°C, preferably a temperature of about 100°C to about 300°C, is selected. The time required for curing differs depending upon the form in which the resin blend of this invention is used, i.e., depending on whether it is a thin film, or a relatively thick molded article or laminate. Usually, a period sufficient for curing the resin may be selected from the range of from about 1 hour to about 2 hours. When the resin blend of this invention is to be used in molded articles, such as those produced via resin transfer molding, compression molding, injection molding, and the like, laminates or bonded structures, it is desirable to apply pressure during the heat curing mentioned above.

Other curing methods involve use of microwave, radio frequency, ionizing radiation, electron beams from various types of accelerators, gamma-rays from isotopes such as cobalt 60, sunlight, and active energy, for example, light radiated from a light source such as a tungsten lamp, or a low-pressure or high-pressure mercury lamp. In the case of photocuring, the resin blend of this invention may contain up to 5 percent, based upon the total weight of the blend, of a known photosensitizer, for example, an organic carbonyl compound such as benzoin,

17

O 96/17020 PCI7US95/14560

benzoin methyl ether, benzanthrone, anthraquinone and benzophenone, or a combination of a sensitizing dye such as eosine, erythrosine or acridine with an amine. Such a photocurable resin blend containing a photosensitizer is effective in coating applications. The blends of the present invention are preferably employed to prepare articles including, but not limited to, composites and laminates, i.e., electrical laminates such as printed circuit boards or rigid substances suitable for the production of printed circuit boards. In preparing the boards, one or more plies, preferably about 4 to about 8 plies, of a fibrous substrate are coated and/or impregnated with the blend of the present invention and laminated. Conventional coating equipment can be employed. Subsequent to coating and/or impregnating and laminating, the substrate is cured at a temperature of about 100°C to about 300°C for about 1 hour to about 2 hours to form a rigid substrate. The blends can be used to coat and/or impregnate fibrous substrates such as fiberglass, nylon, paper such as that obtainable from DuPont under the tradename "Thermount", polyimides, graphite, and the like. The substrate can be in the form of woven fabric, mat, monofilament, multifilament rovings, and the like.

The ratio of the blend of the present invention to the substrate in a prepreg may vary from, based upon the total weight of the preimpregnated substrate or "prepreg", about 20:80 to about 50:50, and preferably from about 35:65 to about

40:60. As used herein, "prepreg" shall refer to the substrate coated with the uncured resin blend of the present invention.

After the rigid substrate is formed, at least one ply, preferably 1 to about 2

18

plies, of a sheet of copper or other electrically conductive material, e.g., gold, silver, aluminum and the like, can then be laminated to the rigid substrate using laminating conditions such as pressure of about 0.34 MPa to about 2.76 MPa and temperatures of about 50°C to about 300°C applied for about 30 to about 300 minutes. Then a circuit can be etched into the conductive layer using techniques well-known to form circuit boards.

The following non-limiting examples are presented to further illustrate the present invention.

The following properties of the blends produced in the Examples were determined as follows: a) The glass transition temperatures were determined by using differential scanning calorimetry ("DSC) via the method described in Interconnecting Packaging Circuitry 2.4.25 (1986)("IPC), as well as by using thermal mechanical analysis ('TMA") via the method described in IPC 2.4.24. b) The flammability was determined via the method described in the

Underwriters Laboratory UL94 Flame Test. c) The dielectric constant and dissipation factor was determined via the methods described in ASTM D-5109, respectively, using 5J cm by 5J cm by 0.07 cm specimens at 1 MHz. d) The percent water absorption was determined via the dip in method described in IPC 2.6.2J at temperatures of 23°C and 100°C, respectively, using specimens having a thickness of 0.07 cm for Examples 1 to 3 and Comparative Examples 1 to 3, and via the method described in ASTM-D570, at a temperature

19

of 23°C using specimens having a thickness of 0.32 cm for Examples A - C. e) The flexural modulus was determined via the method described in ASTM-D790, using 1.3 cm x 7.6 cm x 0.32 cm specimens. f) The compressive strength was determined via the method described in ASTM-D695, using 0.635 cm x 0.635 cm x 1.905 cm specimens.

The following components are employed in the Examples: Component A is a cyanate ester resin available from AlliedSignal Inc., Morristown, New Jersey under the tradename "Primaset", having a molecular weight of about 480, a viscosity at 80°C of about 0.3 Pa«S to about 0.35 Pa»S and a gel time of 15 to 20 minutes at 200°C.

Component B is a brominated epoxy resin available from The Dow Chemical Company having an epoxide equivalent weight ("EEW) of about 425 to about 440, a bromine content of about 20 percent by weight, and a viscosity at 25°C of about 1.5 Pa ^« S to about 2.5 Pa«S. Component C is a tetrafunctional epoxy resin available from Shell

Chemical Company under the tradename Εpon 1031" having the following formula:

20

and an EEW of about 200 to about 240.

Component D is a brominated epoxy resin available from The Dow Chemical Company under the tradename "DER 592" having an EEW of about 345 to about 375, a bromine content of about 17 percent by weight, and a viscosity at 171°C of about 0.8 Pa- S.

Component E is a tetrafunctional epoxy resin available from Ciba-Geigy Corporation under the tradename "MY-720", having an EEW of about 117 to about 134 and a viscosity at 50°C of about 8 to 18 Pa»S.

Component F is an epoxy novolac resin available from The Dow Chemical Company under the tradename 'OEN 431", having an EEW of about 172 to about

179, and a viscosity at 52°C of about 1.1 to about 1.7 Pa ^» S.

Component G is a liquid Bisphenol-A type epoxy resin available from The

21

Dow Chemical Company under the tradename "DER 331", having an EEW of about 182 to about 192, an average molecular weight of about 378, and a viscosity at 25°C of about 11 to about 14 Pa» S.

Component H is a catalytic solution of manganese octoate (6 percent active manganese) in mineral spirits available from Pfaltz & Bauer, Inc.

The relative amounts of Components A, B, C, and D, as used in Examples 1 to 3 and Comparative Examples 1 to 3 are illustrated in Table I. The relative amounts of Components A, E, F, G, and H as used in Examples A, B, and C and Comparative Examples A and C are illustrated in Table II.

Table I

Ex. 1 Ex. 2 Ex. 3 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3

Component % by weight

A 20.5 24.19 26.0

B 59.81 45.44 59.80 45.44

C 7.63 8.03 7.62 8.03

D 48.9 48.84

BADCY 20.49 24.20 25.96

% Br by weight 12.0 9.1 8.3 12.0 9J 8.3 | in blend

22

Table II

Example Comp. Example Example Comp.

A Example B C Example A C

Component % by weight

A 49.98 49.97 49.97

E 49.98 53

F 49.97

G 49.97 43

BADCY 47 57

H 0.049 0.054 0.058

Example It Substrate Coated With Blend of PT Resin and Brominated Epoxv Resin

About 328 parts of PT30 resin (Component A) is dissolved in about 313 parts of acetone in a 3.79 liters tin container. To this mixture is added about 957 parts of brominated epoxy resin (Component B), followed by, based upon the total weight of the mixture, about 0.03 percent of a catalytic solution of manganese octoate (6% active manganese) in mineral spirits and about 0.07% of 2-MI under room temperature conditions, and then the resulting mixture is stirred for about 2 hours until homogeneous.

A glass fabric is then impregnated with the resulting mixture and cured at 177°C with 1.03-138 MPa pressure for 15 minutes, and then for about 1 hour at

220°C under the same pressure conditions.

23

Example 2; Substrate Coated With Blend of PT Resin. Epoxv Resin With 20% Bromination. and Tetrafunetional Enoxv Resin

About 395 parts by weight of PT30 resin (Component A) is dissolved in about 239 parts of acetone. To this mixture are added about 741 parts by weight of brominated epoxy resin (Component B) and about 125 parts by weight of tetrafunetional epoxy resin (Component C), followed by, based upon the total weight of the mixture, about 0.024 percent of a solution of manganese octoate (6% active manganese) in mineral spirits and 0.064% of 2-MI under room temperature conditions, and then the resulting mixture is stirred for about 2 hours until homogeneous.

A glass fabric substrate is then impregnated with the resulting blend and cured in the same manner and under the same pressure conditions as described in Example 1. Example 3: Substrate Coated With Blend of PT Resin. Epoxy

Resin With 17% Bromination. and Tetrafunetional Epoxy Resin About 390 parts by weight of a PT30 resin (Component A) is dissolved in about 255 parts of acetone. To this mixture are added about 735 parts of a brominated epoxy resin (Component D) and about 121 parts by weight of a tetrafunetional epoxy (Component C), followed by, based upon the total weight of the mixture, about 0.04% of the catalytic solution of Example 1 under room temperature conditions, and then the resulting mixture is stirred for about 2 hours until homogeneous.

24

A glass fabric substrate is then impregnated with the resulting blend and cured in the same manner and under the same conditions described in Example 1.

Comparative Example 1 About 49.2 parts by weight of a bisphenol A dicyanate ester (BADCY, available from Lonza Ltd.) having a melting point of about 79°C, a viscosity at

80°C of about 35 MPa«S, a specific gravity at 25°C of about 1.27 g/cm ³ , and a cyanate equivalent weight of about 139 is dissolved in a mixture of about 47J parts of acetone and about 143.6 parts of brominated epoxy resin (Component B). Based upon the total weight of the mixture, about 0.03% of a catalytic solution of manganese octoate (6% active manganese) in mineral spirits and 0.07% of 2-MI under room temperature conditions are added thereto, and then the resulting mixture is stirred for about 2 hours until homogeneous.

A glass fabric is then impregnated with the resulting blend mixture and cured at 177°C for 15 minutes with about 1.38 MPa pressure, and then for about 1 hour at 220°C under the same pressure conditions.

Comparative Example 2 About 58J parts of bisphenol A dicyanate ester from Comparative Example 1 is dissolved in a mixture of about 54.4 parts by weight of acetone, about 109J parts of brominated epoxy polymeric material (Component B), and about 18.3 parts of tetrafunetional epoxy resin (Component C). About 0.024% by weight of a catalytic solution of manganese octoate (6% active manganese) in mineral spirits and 0.064% of 2-MI by weight is added thereto under room temperature conditions, and the resulting mixture is stirred for about 2 hours until

25

homogeneous.

A glass fabric is then impregnated with the resulting blend and cured in the same manner and under the same conditions described in Comparative Example 1. Comparative Example 3

About 62.4 parts by weight of bisphenol A dicyanate ester from Comparative Example 1 is dissolved in a mixture of about 41 parts of acetone, about 117.4 parts of brominated epoxy polymeric material (Component B) and about 193 parts of tetrafunetional epoxy resin (Component C). About 0.04% of the catalytic solution of Comparative Example 2 is added thereto, then the resulting mixture is stirred for about 2 hours until homogeneous.

A glass fabric is then impregnated with the resulting blend and cured in the same manner and under the same conditions described in Comparative Example 1. The thermal, electrical, and moisture absorption properties of laminates described in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 are illustrated in Table I-Q.

26

Table Hi

Property Ex. 1 Ex. 2 Ex. 3 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3

T _β (TMA),°C 200 245 225 182 168-174 208-220

T _z (DSC),°C 208 222 218 170-172 183-185 206-207

UL94 Flame vo NO VO VO VO VI Rating

Dielectric 4.88 432 4.54 4.29 4.26 4.30 Constant @ l MHz

Dissipation 0.0128 0.0150 0.0158 0.0112 0.0119 0.0139

Factor @ 1 MHz

% Water Absorption

D24/23°C 0.25 0.33 0.37 0.25 0.35 0.38 D24/100°C 0.66 0.99 0.92 0.89 1.21 1.49

It can be seen from Table III that substrates coated with the blend of the present invention have excellent thermal, electrical, and moisture absorbance properties. In particular, the glass transition temperature and the water absoφtion properties possessed by the multicyanate ester-containing blend of the present invention are superior to those properties possessed by prior art compositions employing a bisphenol A dicyanate ester. Further, as the amount of multicyanate ester in the blend of the present invention is increased, the glass transition temperature and other mechanical properties will also increase. Example At Blend of PT Resin With Tetrafunetional Enoxv Resin

About 202.7 parts by weight of a PT-30 resin (Component A) and about 202.7 parts of a tetrafunetional epoxy resin (Component E) are combined in a 500

27

ml beaker. The beaker is heated in an oil bath at ambient pressure for about 20 minutes until the temperature of the mixture is about 75°C, while the mixture contained therein is simultaneously stirred until homogeneous. About 0.2 parts of a catalytic solution (Component H) was added thereto, and the resulting mixture is stirred until the catalyst completely dissolves.

The resulting blend is poured into a 20.3 cm x 17.78 cm x 0.32 cm glass mold preheated to about 80°C, which was pretreated with a silicone release agent available from Chemlease Inc. under the tradename "Chemlease 70", and then the filled mold is degassed in a vacuum oven set at about 70°C to 80°C with about 4000 Pa vacuum pressure (30 torr). After 18 hours of curing at 120°C, the sample is removed from the glass mold and postcured for another 30 minutes at 150°C, 105 minutes at 180°C, 30 minutes at 200°C, followed by 4 hours at 220°C. Example B; Blend of PT Resin With Epoxy Novolac Resin About 200 parts of a PT-30 resin (Component A) and about 200 parts of an epoxy novolac resin (Component F) are combined in a 500 ml beaker, which was heated in the same manner and under the same conditions described in Example A. About 0.22 parts of the catalytic solution of Example A was added thereto, then the resulting mixture is degassed and molded in the manner described in Example A. After 18 hours of curing at 120°C, the sample was removed from the glass mold and post cured for another 0.5 hours at 150°C, 2 hours at 180°C, 0.5 hours at 200°C, followed by 4 hours at 220°C.

Example C; Blend of PT Resin With Bis A Type Epoxy Resin About 174.9 parts of a PT-30 resin (Component A) and about 174.9 parts

28

of a bisphenol A type epoxy resin (Component G) are combined in a 500 ml beaker, which is heated in the same manner and under the same conditions described in Example A. About 0.20 parts of the catalytic solution of Example A is added thereto in the manner described in Example A. The resulting mixture is molded and cured in the manner described in Example A.

Comparative Example A The PT resin of Example A is replaced with about 47 parts of the bisphenol A dicyanate of Comparative Example 1. Then, 53 parts of a tetrafunetional epoxy resin (Component E) is added thereto according to the method described in Shimp et al., "Co-Reaction of Epoxide and Cyanate Resins",

33rd Int'l SAMPE Symposium and Exhibition 1-13 (Calif. March 7-10, 1988).

Comparative Example C The PT resin of Example C is replaced with about 57 parts of the bisphenol A dicyanate of Comparative Example 1. Then, 43 parts of an epoxy resin (Component G) is added thereto according to the method described in Shimp,

"AroCy ^® Cyanate Ester Resins Chemistry, Properties & Applications," (3rd Edition, May 1991).

The thermal, electrical, and moisture absoφtion properties of the blends described in Examples A, B, and C and Comparative Examples A and C are illustrated in Table IV.

29

Table IV

Ex, A Comp. Ex. B Ex. C Comp. Ex. A Ex. C

Cure Temp., °C 220 235 220 220 200

Properties

HDT, °C 237 190

T _κ (DMA), °C 273.7 216.7 221.6

T _κ (TMA), °C 291.3 185.8 263.4

Flexural Strength, ASTM D790 MPa 90 73 87 126 132

Flexural Modulus GPa 3.9 3.0 3.8 3.7 2.8

Elongation, % 2.4 2J 2.4 3.81 53

Dielectric 339 3.3 3.0 3J7 3J Constant at 1 MHz

Dissipation 0.0181 0.017 0.0133 0.0246 0.013 Factor at 1 MHz 4 3 3

H ₂ 0 Absoφtion, 0.47 ^(a 2.1 ^w 036 ^a) 032 ^{( )} 1.2 ^a) % (ASTM D570)

Compressive Strength, MPa 339 331 265

Compressive Modulus, GPa 2.8 2.6 2.4

(a) Immersed in RT water for 24 hours, (b) Conditioned 64 hours at 92°C and >95% RH.

30

ΗDT', as used herein, refers to heat distortion temperature, which for puφoses herein, is comparable to the glass transition temperature ("T _g "). It can be seen in Table IV that the blend of the present invention has a higher T _g and an improved water absoφtion than those of the prior art dicyanate ester-epoxy blends. This is because the multifunctional cyanate esters of the present invention possess greater than two cyanate groups, which results in blends having a greater percentage of cured bonds and thus upon subsequent reaction, a greater percentage of triazines. The presence of a large amount of triazines contributes to a higher T _g and a lower water absoφtion.

31