Styrene Terminated Multifunctional Oligomeric Phenols as New Thermosetting Resins for Composites

Preparation of Styrene Terminated Bisphenol-A Formaldehyde (STBPA-F). Bisphenol-A formaldehyde resin was prepared as follows. 150.0 g (0.658 moles) of bisphenol-A was dissolved in 500 ml of ethanol in a 1 liter round bottom flask equipped with condenser and magnetic stirrer. To his reaction mixture was added 0.5 ml of concentrated sulfuric acid. The solution was heated to reflux and then 14.5 g (0.151 moles) of paraformaldehyde was added gradually to the reaction. The reaction was heated at reflux with stirring for 48 hours and then allowed to cool to room temperature. The reaction was neutralized with aqueous sodium hydroxide solution and then concentrated under vacuum, yielding 130.3 g of viscous syrup, with a M.sub.w =362.

50.0 g (0.1062 moles) of bisphenol-A formaldehyde resin and 71.35 g (0.4675 moles) vinylbenzyl chloride (60/40 meta/para isomer ratio) were dissolved in 110 ml of acetone in a three neck-round bottom flask equipped with condenser, addition funnel, thermometer, mechanical stirrer and nitrogen purge. The reaction mixture was heated at reflux (65-70.degree.C. temperature) for a period of one hour, following which a solution of 41.83 g (0.746 moles) of potassium hydroxide in 93 ml of methanol was added to the warm reaction mixture over an internal of one hour. The reaction was stirred thereafter ambient temperature for a period of 24 hours. The reaction mixture was recovered, dried over magnesium sulfate, filtered, and concentrated under vacuum. The resulting oil was dried in a vacuum oven at ambient temperature overnight and yielded 24.5 g of resin.

Preparation of Cured STBPA-F. 3.3 g of STBPA-F of Example 1 was placed in a flat casting dish and cured by heating in an oven at a temperature of 120.degree.C. for a period of 2 hours, followed by a 16 hour cure at 160.degree.C. and a 2 hour cure at 200.degree.C. Following this, the sample was then post-cured for a period of 2 hours at 225.degree.C. and recovered. The cured polymer was found to have a glass transition temperature (Tg) of greater than 300.degree.C., a minor softtening point (Tsp) (measured via Thermal Mechanical Analysis (TMA)) at 165 .+-.5.degree.C., a coefficient of thermal expansion from 25.degree.to 165.degree.C. of 40.+-.2 ppm/.degree.C and from 25.degree.to 260.degree.C. of 65.+-.3 ppm/.degree.C. The dielectric constant at 1 MHz and dissipation factor at 0% and 50% relative humidity are summarized in the following table.

Preparation of Cured STBPA-F from chloroform Solution. 2.0 g of STBPA-F resin of Example 1 was dissolved in about 10 milliliters of ochloroform. The resulting solution was transferred to a flat castingn dish and heated on a hot plate to remove a major portion of the chloroform solvent. The sample was then cured in an oven at 120.degree.C. for 2 hours, followed by 16 hours at 160.degree.C. and 2 hours at 200.degree.C.. The sample was post cured at 225.degree.C. for 1 hour. The cured polymer was found to have the following properties: glass transition temperature (Tg) >300.degree.C., coefficient of thermal expansion from 25 to 260.degree.C. (.alpha..sub.260) of 59.+-.4 ppm/.degree.C. and a dielectric constant and dissipation factor (1 MHz) at 0% relative humidity of 2.63 .+-.0.17 and 0.007.+-.0.001, respectively.

Preparation of Styrene Terminated Polybrominated Bisphenol-A Formaldehyde (STBBPA-F). 40.57 (0.086 moles) of bisphenol-A formaldlehyde resin, 40 milliliters of carbon tetrachloride, 84 milliliters of methanol and 1.99 g of potassium bromide were charged into 500 ml three neck-round bottom flask equipped with condenser, addition funnel, nitrogen purge and magnetic stirring bar. The reaction vessel was placed in a water bath and heated to a temperature of about 50.degree.C. To this 2-phase reaction mixture was added 41.25 milliliters (0.800 moles) of bromine dropwise over a 4 hour period. At the end of this time 80 milliliters of water was added to the reaction mixture and a distillation head attached to the reaction vessel, and the volatile products were distilled off at atmospheric pressure. The remaining residue was taken up in 160 milliliteres of dichloromethane and the organic phase was washed three times with 80 milliliters of water and then twice with 80 milliliteres of 10% aqueous sodium bisulfite to remove any residual bromine which may be present. The organic phase was washed with 80 milliliters of water and dried over sodium sulfate. The methylene chloride was removed under vacuum and then azeotropic drying with ethanol gave 80.70 grams of product.

40.0 g (0.425 moles) of the above polybrominated bisphenol-A formaldehyde resin and 28.54 g (0.187 moles) of vinylbenzyl chloride (60/40 meta/para isomer ratio) were dissolved in 90 ml of acetone in a three neck-round bottom flask equipped with condenser, addition funnel, thermometer, mechanical stirrer and nitrogen purge. The reaction mixture was heated to reflux (65-70.degree.C. temperature) for a period of one hour, following which a solution of 12.54 g (0.224 moles) of pottassium hydroxide in 28 milliliteres of methanol was added to the warm reaction mixture over a period of one hour. Thereafter the reaction was stirred at ambient temperature for a period of 24 hours. The reaction mixture was recovered, dried over magnesium sulfate, filtered and concentrated under vacuum. The resulting oil was dried in a vacuum oven at ambient temperature overnight and yielded 30.8 g of resin.

Preparation of Cured STBBPA-F. 5.0 gof STBBPA-F resin of Example 4 wazs placed in a flat casting dish and cured by heating in an oven at a temperature of 120.degree.C. for 2 hours, followed by a 16 hour cure at 160.degree. C. and a 2 hour cure at 200.degree.C. The sample was post-cured for a period of 2 hours at 225.degree.C. and recovered. The cured polymer was found to have the following properties: glass transition temperature (Tg)>250.degree.C., and dielectric constant (1 MHz) and dissipation factor at 0 to 50% relative humidity as tabulated in Table 2.

EXAMPLE 6

Preparation of Cured STBBPA-F from chloroform Solution. 2.0 g of STBBPA-F resin of Example 4 was dissolved in 10 milliliters of chloroform. The resulting solution was transferred to a flat casting dish and heated on a hott plate to remove the majority of the solventt, the sample was then cured in an oven at 120.degree.C. for 2 hours, followed by 16 hours at 160.degree.C. and 2 hours at 200.degree.C. The sample was post-cured at 225.degree.C. for 1 hour. The cured polymer was found to have the following properties: glass transition temperature (Tg)>250.degree.C., and dielectric constant and dissipation factor at 0% and 50% relative humidity as tabulated in table 3.

Preparation of Cured STBPA; Comparison of Selected Propeties. Styrene terminated bisphenol-A was prepared according to the method of Steiner (U.S. Pat. No. 4,116,936) by reacting vinylbenzyl chloride with bisphenol-A. This resin was cured by taking 2.0 g of STBPA and was dissolved in about 10 milliliters of chloroform in a flat casting dish and heated on a hot plate to remove the majority of the solvent. The sample was then cured in an oven at 120.degree.C. for 2 hours, followed by 16 hours at 160.degree.C. and 2 hours at 200.degree.C.. The sample was postcured for 1.5 hours at 225.degree.C.. The cured polymer had the following properties: glass transition tempeature (Tg)>250.degree. C, minor softening point (Tsp) (measured via TMA) at 168 .+-.11.degree. C., a coefficient of thermal expansion from 25.degree.to 168.degree. C. of 57 .+-.8 ppm/.degree.C. and from 25.degree.to 260.degree. C. of 71 .+-.23 ppm/.degree.C.. The dielectric constant at 1 MHz and dissipation factor at 0% and 50% relative humidity are summarized in the following table.