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United States Patent (19) 11) Patent Number: 4,709,008 Shimp (45) Date of Patent: Nov

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United States Patent (19) 11) Patent Number: 4,709,008 Shimp (45) Date of Patent: Nov United States Patent (19) 11) Patent Number: 4,709,008 Shimp (45) Date of Patent: Nov. 24, 1987 (54) BLEND OF TRIS (CYANATOPHENYL) 3,448,079 5/1966 Grigat ................................... 260/59 ALKANE AND BIS(CYANATOPHENYL) 3,755,402 6/1970 Grigat ................................. 260/453 ALKANE 3,987,230 3/1975 Gaku ................................... 428/236 3,994,949 9/1975 Meyer ................................. 260/453 (75) Inventor: David A. Shimp, Prospect, Ky. 4,022,755 7/1975 Tanigaichi ............................ 260/59 4,330,658 12/1980 Ikeguchi............................... 528/73 73 Assignee: Interez, Inc., Louisville, Ky. 4,581,425 4/1985 Hefner .................................. 526/72 21 Appl. No.: 880,529 Primary Examiner-Harold D. Anderson 22 Filed: Jun. 30, 1986 Attorney, Agent, or Firm-Herbert P. Price 51) Int. Cl............................................... CO8G 83/00 (57) ABSTRACT 52 U.S. C. .................................... 528/422; 528/210; Blends of tricyanate esters and dicyanate esters when 528/211 cured exhibit excellent heat and moisture resistant prop 58 Field of Search ........................ 528/422, 210, 211 erties. The cured compositions are useful in structural 56 References Cited composites, filmed structural adhesive and printed wir ing boards. U.S. PATENT DOCUMENTS 3,403,128 8/1966 Berndt ................................ 260/45.8 14 Claims, No Drawings 4,709,008 1. 2 wherein the R's are H or methyl and can be the same or BLEND OF TRIS (CYANATOPHENYL) ALKANE different and wherein X is methylene, alkylidene having AND BIS(CYANATOPHENYL) ALKANE 2 to 4 carbon atoms, oxygen (-O-), or divalent sulfur (-S-). When properly cured, the blended resins pro BACKGROUND OF THE INVENTION duce thermoset plastics which, when tested in the mois The field of art to which this invention pertains is aryl ture saturated condition, have heat distortion tempera cyanate esters, i.e., cyanic acid esters of polyhydric tures of at least 230 C, moisture absorptions of no more phenols. than 3 percent, and flexure modulus of at least 0.4x 106 Industry is constantly searching for lighter, stronger psi at 75 F., and of at least 0.2x 106 psi at 325 F. and more resistant materials to be used in place of the O The compositions of this invention find uses in the materials used today. For example, the aerospace indus following areas: try is devoting considerable effort to utilizing structural a. Structural composites for military aircraft, particu composites in place of metals. Structural composites larly supersonic, and commercial aircraft, particularly based on thermoplastic or thermoset resins and glass or in the engine area; carbon fibers have been and are being used successfully 15 b. Structural film adhesive for military and commer in many parts of military and commercial aircraft. Ther cial aircraft; moset resins which are being used in such applications c. Filament winding or vacuum bag autoclave mold are epoxy resins, bismaleimide resins, and cyanate ester ing processes; resins. d. Tooling for structural composites; Cyanate ester resins, which are finding more and 20 e. Multilayer printed wiring boards; more uses, are based on the reaction products of poly f. Semi conductor encapsulants. hydric phenols and cyanogen halides. Such resins and their methods of preparation are described in U.S. Pat. DETAILED DESCRIPTION OF INVENTION Nos. 3,403,128 and 3,755,402. Additional patents which 25 The tricyanate esters useful in this invention are made describe cyanate esters are U.S. Pat. Nos. 3,448,079, by reacting a cyanogen halide with tris(hydroxypheny 3,987,230, 3,994,949, 4,022,755, and 4,330,658. Tris(- l)alkanes. The tris(hydroxyphenyl)alkanes have the cyanatophenyl)alkanes are described in U.S. Pat. No. formula: 4,581,425. Even though these cyanate esters have ex ceptional properties when cured, there is a need for 30 R R materials which have even better heat resistant proper ties and strength properties under adverse conditions. Therefore, there is a continuing effort to find materi HO C OH als which have even higher heat resistance, moisture resistance, and strength properties. 35 R R SUMMARY OF THE INVENTION This invention relates to blends of cyanate esters. In one aspect, this invention pertains to blends of cyanate OH --- esters based on trihydric phenols with cyanate esters based on dihydric phenols. In still another aspect, this wherein the R's have the same designation as indicated invention relates to prepolymers of the cyanate ester herein above. blends and to thermoset polymers obtained therefrom. Such trihydric phenolic compounds are made by The tricyanate esters used in this invention are tris(- reacting 4-hydroxybenzaldehyde or 4-hydrox cyanatophenyl)alkanes having the structural formula: 45 yacetophenone with an excess of phenol under acidic conditions. Such trihydric phenols are disclosed in U.S. Pat. Nos. 3,579,542 and 4,394,496 which are hereby R R incorporated by reference. i In order to prepare the tris cyanate ester useful in this NCO C OCN invention, the trihydric phenols are reacted with a cy 50 anogen halide in the presence of an acid acceptor, i.e., a base. This reaction is well known and is described in R R U.S. Pat. No. 3,755,402 which is hereby incorporated by reference. The cyanogen halides useful in this inven tion are cyanogen chloride and cyanogen bromide, with 55 cyanogen chloride being preferred. OCN The acid acceptors which can be used to prepared the wherein the R's are H or methyl and can be the same or tris cyanate esters useful in this invention are inorganic different. These tri cyanate esters are blended with or organic bases such as sodium hydroxide, potassium 60 hydroxide, sodium methylate, potassium methylate, and dicyanate esters having the structural formula: various amines, preferably tertiary amines. Examples of useful amines are triethylamine, tripropylamine, die R R thylpropylamine, pyridine, and the like. A preferred base is triethylamine. 65 The reaction is carried out in an organic solvent such as ethyl acetate, toluene, xylene, chlorinated hydrocar bons, acetone, diethyl ketone and the like. A preferred R R solvent is methylene chloride. 4,709,008 3 4 The reaction is conducted under low temperatures, ized. The curing reaction can be conducted at one tem preferably between about -30° C. and 15 C. perature or can be conducted by heating in steps. If The dicyanate esters useful in this invention are made conducted at one temperature, the temperature will by reacting dihydric phenols with cyanogen halide vary from about 250 F. to about 450 F. When con using the procedure described in U.S. Pat. No. ducted by stepwise heating, the first step, or gelation 3,579,542 referred to hereinabove. Useful dihydric phe step is performed at a temperature of about 150 F. to nois are bis(4-hydroxyphenyl)methane, bis(4-hydroxy about 350 F. The curing step is conducted at a temper phenyl)-2,2-propane (Bisphenol A), bis(4-hydroxy-3,5- ature of about 300 F. to about 450 F., and the optional dimethylphenyl)methane, bis(4-hydroxy-3,5-dimethyl post-curing step is conducted at a temperature of about phenyl)-2,2-propane, bis(4-hydroxyphenyl)ether and O 400' F. to about 550 F. The overall curing reaction will bis(4-hydroxyphenyl)sulfide. take about 5 minutes to about 8 hours. The compositions of this invention are made by The tricyanate-ester dicyanate-ester blends of this blending the tricyanate ester and the dicyanate esters in invention have very good properties when cured. Sur the amounts of about 90 to about 10 parts by weight of prisingly, it has been found that the cured blends of the tricyanate ester with about 10 to about 90 parts by 15 tricyanate esters and dicyanate esters have properties weight of dicyanate ester. Preferred blends are made which exceed the properties of either of the esters when from 60 to about 20 parts by weight of tricyanate ester cured alone. with about 40 to about 80 parts by weight of dicyanate The tricyanate-dicyanate ester blends of this inven ester. tion can be blended with polyepoxide resins and can be The blends of tricyanate esters and dicyanate esters 20 cured to form useful thermoset compositions. Up to can be used as is or can be partially trimerized to form about 70 weight percent based on total blend weight prepolymers. Prepolymers are amorphous in form and can be polyepoxide resin. Such polyepoxide resins are are somewhat easier to use in prepregging operations the well-known glycidyl ethers of polyhydric phenols then the crystalline or semi-crystalline unpolymerized which are made by reacting an epihalohydrin, prefera blends. Prepolymers are made by heating the blends 25 bly epichlorohydrin, with a polyhydric phenol, prefera with or without catalyst at a temperature of about 140 bly bisphenol A. C. to about 220 C. for a time sufficient to cyclotrimer When formulating for particular end uses, additional ize from about 5 to about 50 percent of the cyanate components can be incorporated in the polycyanate functional groups. Useful prepolymers possesses melt compositions. Such components include minor amounts viscosities ranging from about 2,000 cps. at 50 C. up to 30 of thermoplastic resin tougheners, reinforcing fibers, 10,000 cps. measured at 150° C. Catalysts which can be colloidal silica flow modifiers, mineral fillers and pig used in preparing the prepolymers are mineral or Lewis ents. acids, bases such as alkali metal hydroxides, alkali metal The cured compositions of this invention can be used alcoholates or tertiary amines, salts such as sodium in vacuum bagged structural composites, transfer carbonate or lithium chloride, or active hydrogen con 35 molded encapsulants, filmed structural adhesives, taining compounds, such as bisphenols and monophen printed wiring boards and composites for aircraft pri ols.
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