WO2016029452A1

WO2016029452A1 - Naphthalene based epoxy for halogen-free and flame retardant compositions

Info

Publication number: WO2016029452A1
Application number: PCT/CN2014/085580
Authority: WO
Inventors: Xiaomei Song; Hongyu Chen; Michael J. Mullins; Fujun LU
Original assignee: Blue Cube Ip Llc
Priority date: 2014-08-29
Filing date: 2014-08-29
Publication date: 2016-03-03
Also published as: TW201615739A; WO2016033074A1

Abstract

A curable composition comprising, consisting of, or consisting essentially of a) an epoxy component comprising a dinaphthalene epoxy having the structure (X) wherein each R₁ group is independently a C1-C20 hydrocarbon; a is an integer in the range of from 0 to 6; m is an integer in the range of 0 to 5; and b) a hardener component comprising i) a naphthol novolac which is a reaction product of I) from 1 to 99 weight percent 1-naphthol and II) from 1 to 99 weight percent 2-naphthol; ii) a phosphorus-containing composition which is the reaction product of an etherified resole with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; and iii) optionally a phenolic resin selected from the group consisting of a molecule having at least one substituted or unsubstituted naphthalene ring, a high functionality phenolic resin, and combinations thereof, is disclosed. The curable composition can be used to prepare prepregs and electrical laminates.

Description

NAPHTHALENE BASED EPOXY FOR HALOGEN-FREE AND FLAME RETARD ANT COMPOSITIONS

FIELD OF THE INVENTION The present invention is related to epoxy resin compositions. More particularly, the present invention is related to halogen- free or substantially halogen-free formulations.

INTRODUCTION

Epoxy resins are widely used in coatings, adhesives, printed circuit boards, semiconductor encapsulants, adhesives and aerospace composites thanks to the excellent mechanical strength; chemical, moisture, and corrosion resistance; good thermal, adhesive, and electrical properties.

The integrated circuit and printed circuit board industries are in need of low cost, highly reliable interconnect schemes that support the rapidly increasing input/output (I/O) count in ASICs and microprocessors. There is a growing interest in alternatives to the standard ceramic chip in conventional printed circuit boards for single and multichip carrier applications. However, the mismatch of the coefficient of thermal expansion (CTE) between printed wiring board (PWB) base materials in the x- axis and y- axis in a plane and silicon leads to stress between components and the PWB. The stress is released mainly by deformation of the solder ball and the PWB. On the other hand, the mismatch of the CTE between PWB base materials in z-axis and copper leads to a failure of the board, although the mechanism is different. Copper plated-through holes (PTH) and copper plate vias will suffer cracks within the copper due to the substantially higher expansion of the PWB. Thus, a composition having a lower CTE in x- and y- axis towards silicon and in z-axis towards copper resulting in lower stress between the PWB and its components is desirable. SUMMARY

The instant invention is a curable composition comprising, consisting of, or consisting essentially of: a) an epoxy component comprising a dinaphthalene epoxy having the structure

wherein each Ri group is independently a C1 -C20 hydrocarbon; a is an integer in the range of from 0 to 6; m is an integer in the range of from 0 to 5; b) a hardener component comprising i) a naphthol novolac which is a reaction product of I) from 1 to 99 weight percent 1 -naphthol and II) from 1 to 99 weight percent 2-naphthol; ii) a phosphorus- containing composition which is the reaction product of an etherified resole with 9, 10- dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO); and iii) optionally a phenolic resin selected from the group consisting of a molecule having at least one substituted or unsubstituted naphthalene ring, a high functionality phenolic resin, and combinations thereof.

DETAILED DESCRIPTION

The instant invention is a curable composition. The instant invention is a curable composition comprising, consisting of, or consisting essentially of a) an epoxy component comprising a dinaphthalene epoxy having the structure

wherein each Ri group is independently a C1 -C20 hydrocarbon; a is an integer in the range of from 0 to 6; m is an integer in the range of 0 to 5; b) a hardener component comprising i) a naphthol novolac which is a reaction product of I) from 1 to 99 weight percent 1 -naphthol and II) from 1 to 99 weight percent 2-naphthol; ii) a phosphorus-containing composition which is the reaction product of an etherified resole with 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO); and iii) optionally a phenolic resin selected from the group consisting of a molecule having at least one substituted or unsubstituted

naphthalene ring, a high functionality phenolic resin, and combinations thereof.

The curable composition can further include optionally a filler. The curable composition can further include optionally a catalyst and/or a solvent. The curable composition comprises an epoxy component and a hardener component, as described in further details herein below.

The curable composition may further include one or more fillers selected from the group consisting of natural silica, fused silica, alumina, hydrated alumina, talc, alumina trihydrate, magnesium hydroxide and combinations thereof. The curable composition may comprise 10 to 80 percent by weight of one or more fillers. All individual values and subranges from 10 to 80 weight percent are included herein and disclosed herein, for example, the weight percent of filler can be from a lower limit of 10, 12, 15, 20, or 25 weight percent to an upper limit of 62, 65, 70, 75, or 80 weight percent. For example, curable composition may comprise 15 to 75 percent by weight of one or more fillers; or in the alternative, curable composition may comprise 20 to 70 percent by weight of one or more fillers. Such fillers include, but are not limited to natural silica, fused silica, alumina, hydrated alumina, talc, alumina trihydrate, magnesium hydroxide and combinations thereof.

The curable composition may further include one or more catalysts. The curable composition may comprise 0.01 to 10 percent by weight of one or more catalysts. All individual values and subranges from 0.01 to 10 weight percent are included herein and disclosed herein, for example, the weight percent of catalyst can be from a lower limit of 0.01, 0.03, 0.05, 0.07, or 1 weight percent to an upper limit of 2, 6, or 10 weight percent. For example, the curable composition may comprise 0.05 to 10 percent by weight of one or more catalysts; or in the alternative, the curable composition may comprise 0.05 to 2 percent by weight of one or more catalysts. Such catalysts include, but are not limited to, 2-methyl imidazole (2MI), 2-phenyl imidazole (2PI), 2-ethyl-4-m ethyl imidazole (2E4MI), l-benzyl-2- phenylimidazole (1B2PZ), boric acid, triphenylphosphine (TPP), tetraphenylphosphonium- tetraphenylborate (TPP-k), and combinations thereof.

The curable composition may further include one or more tougheners. The curable composition may comprise 0.01 to 70 percent by weight of one or more tougheners. All individual values and subranges from 0.01 to 70 weight percent are included herein and disclosed herein, for example, the weight percent of toughener can be from a lower limit of 0.01, 0.05, 1, 1.5, or 2 weight percent to an upper limit of 15, 30, 50, 60, or 70 weight percent. For example, the curable composition may comprise 1 to 50 percent by weight of one or more tougheners; or in the alternative, the curable composition may comprise 2 to 30 percent by weight of one or more tougheners.

Such tougheners include, but are not limited to core shell rubbers. A core shell rubber is a polymer comprising a rubber particle core formed by a polymer comprising an elastomeric or rubbery polymer as a main ingredient and a shell layer formed by a polymer graft polymerized on the core. The shell layer partially or entirely covers the surface of the rubber particle core by graft polymerizing a monomer to the core. Generally the rubber particle core is constituted from acrylic or methacrylic acid ester monomers or diene

(conjugated diene) monomers or vinyl monomers or siloxane type monomers and

combinations thereof. The toughening agent may be selected from commercially available products; for example, Paraloid EXL 2650A, EXL 2655, EXL2691 A, each available from The Dow Chemical Company, or Kane Ace® MX series from Kaneka Corporation, such as MX 120, MX 125, MX 130, MX 136, MX 551, or METABLEN SX-006 available from Mitsubishi Rayon.

The curable composition may further include one or more solvents. Solvents can be used to solubilize the epoxy and hardener component or to adjust the viscosity of the final varnish. The curable composition may comprise 0.01 to 50 percent by weight of one or more solvents. All individual values and subranges from 0.01 to 50 weight percent are included herein and disclosed herein, for example, the weight percent of catalyst can be from a lower limit of 0.01, 0.03, 0.05, 0.07, or 1 weight percent to an upper limit of 2, 6, 10, 15, 30, or 50 weight percent. For example, the curable composition may comprise 1 to 50 percent by weight of one or more solvents; or in the alternative, the curable composition may comprise 2 to 30 percent by weight of one or more solvents. Such solvents include, but are not limited to methanol, acetone, n-butanol, methyl ethyl ketone (MEK), benzene, toluene, xylene, cyclohexanone, dimethylformamide (DMF), ethyl alcohol (EtOH), propylene glycol methyl ether (PM), propylene glycol methyl ether acetate (DOWANOL™ PMA) and mixtures thereof.

The curable composition comprises a) an epoxy component; b) a hardener component comprising i) a naphthol novolac which is a reaction product of I) from 1 to 99 weight percent 1 -naphthol and II) from 1 to 99 weight percent 2-naphthol; and ii) an oligomeric compound comprising a phosphorus composition which is the reaction product of an etherified resole with DOPO; and iii) optionally a phenolic resin selected from the group consisting of a molecule having at least one substituted or unsubstituted naphthalene ring, a high functionality phenolic resin, and combinations thereof.

In various embodiments, the epoxy component is a dinaphthalene epoxy. An example of the epoxy component is depicted in Formula 1.

Formula 1

In Formula 1 , each Ri group is independently a hydrocarbon with 1 to 20 carbon atoms per molecule. All individual values and subranges from 1 to 20 are included herein and disclosed herein, for example Rl can be a hydrocarbon with 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms per molecule, a is an integer between 0 and 6. All individual values and subranges from 0 to 6 are included herein and disclosed herein, for example a can be 0, 1 , 2, 3, 4, 5, or 6. m is an integer in the range of 0 to 5. All individual values and subranges from 0 to 5 are included herein and disclosed herein, for example m can be 0, 1 , 2, 3, 4, or 5.

In an embodiment, the dinaphthalene epoxy is made by contacting a

dihydroxydinaphthyl with an epihalohydrin. The dihydroxydinaphthyl can be trans-isomers or cis-isomers or a mixture of cis and trans isomers. In various embodiments, the

epihalohydrin is epichlorohydrin (EPI). One example of the reaction scheme is depicted in Formula 2, below.

Formula 2

The curable composition may comprise 1 to 99 percent by weight of the epoxy component. All individual values and subranges from 1 to 99 weight percent are included herein and disclosed herein, for example, the weight percent of epoxy resin can be from a lower limit of 12, 17, 20, 30, or 35 weight percent to an upper limit of 55, 70, 86, 90, or 98 weight percent. For example, curable composition may comprise 20 to 98 percent by weight of one or more epoxy resins or in the alternative, curable composition may comprise 30 to 90 percent by weight of one or more epoxy resins.

The curable composition may comprise 1 to 99 percent by weight of one or more naphthol novolac resins. Such naphthol novolac resins ensure that the epoxy resin

composition in the cured state has a low coefficient of linear expansion and a high Tg in a temperature range from room temperature to equal to or above Tg. All individual values and subranges from 1 to 99 weight percent are included herein and disclosed herein, for example, the weight percent of naphthol novolac resin can be from a lower limit of 1, 1.2, 1.5, 12, 20 weight percent to an upper limit of 45, 50, 54, 60, or 70 weight percent.

In various embodiments, the naphthol novolac resin is formed by a naphthol component contacted with aldehyde. An example of the reaction scheme is depicted in Formula 3, below.

Formula 3

The naphthol novolac is a reaction product of I) from 1 to 99 weight percent 1 -naphthol and II) from 1 to 99 weight percent 2-naphthol. All individual values and subranges from 1 to 99 weight percent are included herein and disclosed herein, for example, the weight percent of 1- naphthol can be from a lower limit of 1, 10, 14, 25, 33, 50, 66, 71, or 80 weight percent to an upper limit of 25, 33, 55, 66, 75, 82, or 95 weight percent. Likewise, the weight percent of 2- naphthol can be from a lower limit of 1, 10, 14, 33, 50, 66, 71, or 80 weight percent to an upper limit of 25, 33, 55, 66, 82, or 95 weight percent.

In various embodiments, paraformaldehyde can be used as the aldehyde. Other aldehydes that can be used include, but are not limited to formaldehyde, aliphatic aldehydes, and aromatic aldehydes.

In various embodiments, the naphthol component can be added to a solvent before contact with the aldehyde. Any suitable solvent can be used such as, for example, toluene and xylene.

Optionally, phenolic resins can be added to the curable composition. The phenolic resin can be selected from the group consisting of a molecule having at least one substituted or unsubstituted naphthalene ring, a high functionality phenolic resin, and combinations thereof.

Phenolic resins that can be used include, but are not limited to novolac type phenolic resins (e.g., phenol novolac resins, cresol novolac resins), triphenolalkane type phenolic resins (e.g., triphenolmethane phenolic resins, triphenolpropane phenolic resins), phenol aralkyl type phenolic resins, biphenyl aralkyl type phenolic resins, biphenyl type phenolic resins. In an embodiment, the phenolic resin is a naphthalene type phenolic resin. These phenolic resins may be employed alone or in combination of two or more.

The curable composition may comprise 1 to 70 percent by weight of one or more optional phenolic resins. All individual values and subranges from 1 to 99 weight percent are included herein and disclosed herein, for example, the weight percent of phenolic resin can be from a lower limit of 1, 1.2, 1.5, 12, or 20 weight percent to an upper limit of 45, 50, 54, 60, or 70 weight percent.

The curable composition may comprise 1 to 80 percent by weight of one or more oligomeric compounds comprising a phosphorus composition which is the reaction product of an etherified resole with DOPO. Such DOPO containing resins can be selected from DOP- BN, DOPO-HQ, and/ or other reactive or non-reactive DOPO-containing resins. All individual values and subranges from 1 to 80 weight percent are included herein and disclosed herein, for example, the weight percent of DOPO compound can be from a lower limit of 1.5, 2, 3, 5, or 10 weight percent to an upper limit of 20, 40, 55, 60, or 70 weight percent. For example, curable composition may comprise 2 to 60 percent by weight of one or more DOPO compound or in the alternative, curable composition may comprise 5 to 40 percent by weight of one or more DOPO compound.

In an embodiment, the DOPO-containing compound is an oligomeric composition comprising a phosphorus-containing compound which is the reaction product of an etherified resole with DOPO. This reaction product, referred to hereinafter as 'DOP-BN,' is depicted in Formula 4, below.

8,124,716. The composition can be produced by any suitable process known to those skilled in the art. The components are prepared by any suitable method. In an embodiment, dihydroxydinapthyl is contacted with an epihalohydrin in a reaction zone under reaction conditions to form a dinaphthalene epoxy; and 1-naphthol and 2-naphthol are contacted in a reaction zone under reaction conditions to form a naphthol novolac composition. In an embodiment, solutions of the epoxy component, naphthol novolac, and phosphorus- containing composition are mixed together. Any other desired component, such as the optional components described above, are then added to the mixture.

Embodiments of the present disclosure provide prepregs that include a reinforcement component and the curable composition, as discussed herein. The prepreg can be obtained by a process that includes impregnating a matrix component into the reinforcement component. The matrix component surrounds and/or supports the reinforcement component. The disclosed curable compositions can be used for the matrix component. The matrix component and the reinforcement component of the prepreg provide a synergism. This synergism provides that the prepregs and/or products obtained by curing the prepregs have mechanical and/or physical properties that are unattainable with only the individual components. The prepregs can be used to make electrical laminates for printed circuit boards.

The reinforcement component can be a fiber. Examples of fibers include, but are not limited to, glass, aramid, carbon, polyester, polyethylene, quartz, metal, ceramic, biomass, and combinations thereof. The fibers can be coated. An example of a fiber coating includes, but is not limited to, boron.

Examples of glass fibers include, but are not limited to, A-glass fibers, E-glass fibers, C-glass fibers, R-glass fibers, S-glass fibers, T-glass fibers, and combinations thereof.

Aramids are organic polymers, examples of which include, but are not limited to, Kevlar®, Twaron®, and combinations thereof. Examples of carbon fibers include, but are not limited to, those fibers formed from polyacrylonitrile, pitch, rayon, cellulose, and combinations thereof. Examples of metal fibers include, but are not limited to, stainless steel, chromium, nickel, platinum, titanium, copper, aluminum, beryllium, tungsten, and combinations thereof. Examples of ceramic fibers include, but are not limited to, those fibers formed from aluminum oxide, silicon dioxide, zirconium dioxide, silicon nitride, silicon carbide, boron carbide, boron nitride, silicon boride, and combinations thereof. Examples of biomass fibers include, but are not limited to, those fibers formed from wood, non-wood, and combinations thereof. The reinforcement component can be a fabric. The fabric can be formed from the fiber, as discussed herein. Examples of fabrics include, but are not limited to, stitched fabrics, woven fabrics, and combinations thereof. The fabric can be unidirectional, multiaxial, and combinations thereof. The reinforcement component can be a combination of the fiber and the fabric.

The prepreg is obtainable by impregnating the matrix component into the

reinforcement component. Impregnating the matrix component into the reinforcement component may be accomplished by a variety of processes. The prepreg can be formed by contacting the reinforcement component and the matrix component via rolling, dipping, spraying, or other such procedures. After the prepreg reinforcement component has been contacted with the prepreg matrix component, the solvent can be removed via volatilization. While and/or after the solvent is volatilized the prepreg matrix component can be cured, e.g. partially cured. This volatilization of the solvent and/or the partial curing can be referred to as B-staging. The B-staged product can be referred to as the prepreg.

For some applications, B-staging can occur via an exposure to a temperature of 60 °C to 250 °C; for example B-staging can occur via an exposure to a temperature from 65 °C to 240 °C , or 70 °C to 230 °C. For some applications, B-staging can occur for a period of time of 1 minute (min) to 60 min; for example B-staging can occur for a period of time from, 2 min to 50 min, or 5 min to 40 min. However, for some applications the B-staging can occur at another temperature and/or another period of time.

One or more of the prepregs may be cured (e.g. more fully cured) to obtain a cured product. The prepregs can be layered and/or formed into a shape before being cured further. For some applications (e.g. when an electrical laminate is being produced) layers of the prepreg can be alternated with layers of a conductive material. An example of the conductive material includes, but is not limited to, copper foil. The prepreg layers can then be exposed to conditions so that the matrix component becomes more fully cured.

One example of a process for obtaining the more fully cured product is pressing. One or more prepregs may be placed into a press where it subjected to a curing force for a predetermined curing time interval to obtain the more fully cured product. The press has a curing temperature in the curing temperature ranges stated above. For one or more

embodiments, the press has a curing temperature that is ramped from a lower curing temperature to a higher curing temperature over a ramp time interval. During the pressing, the one or more prepregs can be subjected to a curing force via the press. The curing force may have a value that is 10 kilopascals (kPa) to 350 kPa; for example the curing force may have a value that is 20 kPa to 300 kPa, or 30 kPa to 275 kPa. The predetermined curing time interval may have a value that is 5 s to 500 s; for example the predetermined curing time interval may have a value that is 25 s to 540 s, or 45 s to 520 s. For other processes for obtaining the cured product other curing temperatures, curing force values, and/or predetermined curing time intervals are possible. Additionally, the process may be repeated to further cure the prepreg and obtain the cured product.

The prepregs can be used to make composites, electrical laminates, and coatings. Printed circuit boards prepared from the electrical laminates can be used for a variety of applications. In an embodiment, the printed circuit boards are used in smartphones and tablets. In various embodiments, the electrical laminates have a copper peel strength in the range of from 4 lb/in to 12 lb/in.

EXAMPLES

Synthesis of Naphthol Novolac Hardener (mNPN)

All materials used in synthesizing naphthol novolacs were from Sinopharm Co. (Shanghai, China) except as mentioned otherwise. 1-Naphthol (24g, 0.17mol) and 2-naphthol (12g, 0.083mol) were dissolved in toluene

(75ml) at 50 °C (using a 250ml 3-neck round bottom flask equipped with a stirrer, condenser and a tube for introduction of N₂). After the solids disappeared, oxalic acid (300mg, 5mmol) was added followed by paraformaldehyde (6.75g, 0.225mol). The reaction mixture was slowly heated to 90 °C and many bubbles appeared. After the mixture was stabilized, it was refluxed with stirring for 6.5 hours. Then it was cooled to 50 °C and the upper toluene solution was removed. The residue was then dissolved with cyclohexanone (30ml) at 80 °C for 1 hour. The solution could be used without further purification. A small portion was removed and dried at 80 °C in a vacuum oven for 3 hours to calculate the concentration of mNPN in cyclohexanone. Synthesis of Dinaphthanlene Epoxy (EN-1)

All materials used in synthesizing dinaphthalene epoxy were from Sinopharm Co. (Shanghai, China) except as mentioned otherwise.

2, 2'-hydroxy- Ι,Γ-binaphthalene (14.32 g, 50 mmol), poly( ethylene glycol) (PEG- 400) (1 g), and epichlorohydrin (110 ml) were added to a 250 ml three-necked bottle. The bottle was equipped with a modified dean-stark trap with a condenser and a vacuum controller. The reaction system was heated to 65°C. Then, 8.6 grams of 48 wt% aqueous sodium hydroxide was added to the above solution via a metering pump over a period of 6 hours while maintaining the temperature at 65°C under reduced pressure. During the reaction, water generated by the reaction and water that was contained in the aqueous solution of sodium hydroxide were removed continuously from the reaction system by azeotropic distillation, and the distilled epichlorohydrin was returned to the reaction system. After the reaction ended, the reaction mixture was filtered and subsequently distilled to remove salt and excess epichlorohydrin. 100 ml of ethyl acetate was added to dissolve the resulting crude resin. The obtained solution was washed with water several times to remove PEG-400. The ethyl acetate was then evaporated to yield the final product.

Varnish Formulations

Ingredients

Epoxy EN-1 (dinaphthalene epoxy, 60% in methyl ethyl ketone), from the above process

Epoxy D.E.N. 438 (3.6 functionality epoxy, 60% in methyl ethyl ketone), from The Dow Chemical Company eBPAN (Bisphenol A type phenolic novolac epoxy resin, EEW=200), from The Dow Chemical Company mNPN (5 functionality naphthol novolac), synthesized compound from the above process

DOP-BN (60% in methyl ethyl ketone), from The Dow Chemical Company

HF-1M (phenol novolac resin, HEW=106), from Meiwa Plastic Industries LTD

X.Z. 92535 (phenol novolac resin 50% in Propylene Glycol Monomethyl Ether), from The Dow Chemical Company MEH7000 (Cresol /Naphthol / Aldehyde type resin, HEW=143), from Meiwa Plastic Industries LTD

MEH7500 (triphenylmethane type phenol resin, HEW=97), from Meiwa Plastic Industries LTD MEH7600-4H (high functionality phenol resin, HEW=100), from Meiwa Plastic

Industries LTD

BPAN (Bisphenol A type phenolic novolac resin, HEW=125), from The Dow Chemical Company

2-methylimidazole (2-MI): curing catalyst (10% in Propylene Glycol Monomethyl Ether), from Sinopharm Chemical and Reagent Company

The above ingredients were mixed according to the corresponding formulations and shaken to form a uniform solution on a shaker. The catalyst was then added to the varnish, and gel time of the varnish was tested on a hot plate maintained at 171°C. The gelled material was recovered from the hot plate surface and post-cured in an oven at 220°C for 2 hours. Then the thermal properties of the cured material were measured by DSC and CTE was measured by TMA. The formulations and results are shown in Tables 1 and 2.

Table 1. Varnish Formulations and Thermal Properties of Cured Epoxy Resins (Inventive Examples)

Table 2. Varnish Formulations and Thermal Properties of Cured Epoxy Resins (Comparative Examples)

Results in Tables 1 and 2 show that:

From the comparison between Inventive Examples 1-11 and Comparative Examples A-L, it can be found that EN-1 is a good building block to decrease the CTE values of cured resins. Also, higher content of EN-1 in the formulation (higher EEW/HEW) resulted in lower CTE. For conventional high functional epoxy resin D.E.N. 438, the EEW/HEW ratio provided minimal influence on CTE (Comparative Ex. B-I).

The type of phenol novolac hardener influenced Tg performance. Comparing Inventive Examples 5-6 and Inventive Examples 7-11 shows that using high functional hardeners result in higher Tg while maintaining comparative CTE performance. Properties of the laminates

An inventive and two comparative laminates were prepared. The detailed varnish formulations are listed in Table 3. First, the polymer ingredients were mixed to form a uniform 60% solution in MEK and shaken for 1 hour. The varnish was then painted on the glass sheets (Hexcel 21 16) and partially cured at 171 °C in a ventilated oven to make prepregs. Finally, 8 prepreg pieces were hot pressed with copper clad at 220 °C for two hours to make a laminate. The properties of the laminates were then tested and detailed results were shown in Table 4.

Table 3. Varnish Formulations for the Laminates

Table 4. Performance of Laminates

The results in Table 4 show that compared with the control laminates prepared with high- functional epoxy resins, Inventive Example 12 showed a lower z-axis coefficient of thermal expansion, higher Tg, lower water absorption and good flame retardant performance.

Testing Methods

The reactivity of the different varnish formulations was determined in terms of time required for the material to gel. The gel point is the point at which the resin turns from a viscous liquid to an elastomer. The gel time was measured and recorded using approximately 0.7 ml of liquid dispensed on a hot plate maintained at 171°C, stroking the liquid back and forth after 60s on the hot-plate until it gels.

Hand lay-up technique

The hand lay-up technique was developed to make prepreg on a small scale quickly and easily. A single sheet of glass fabric approximately twelve inches square was stapled to a wood frame. The frame with e-glass fabric was placed on a fiat surface that was covered with a disposable plastic sheet. About 25-35 g varnish was poured onto the e-glass fabrics and then evenly spreaded with a paint brush two inches in width. The frame with wetted glass fabrics was subsequently suspended in an air circulating oven at a temperature of 171°C to remove solvent. After one minute, the frame was removed and allowed to cool to room temperature. The prepreg was crushed to obtain powder for further testing. Thermogravity analysis (TGA) of the cured resins was performed with Instrument TGA Q5000 V3.10 Build 258. The test temperature ranges from room temperature to 600°C; the heating rate is 20°C/min, nitrogen flow protection. The decomposition temperature (Td) was determined through selecting the corresponding temperature at 5% of weight loss (residual weight 95%) of materials.

Glass transition temperature (Tg) of the cured resins was determined by both DSC and DMTA.

The DSC testing condition is as follows:

N2 environment

Cycle one:

Initial Temp: room temperature

Final Temp: 180 °C

Ramp Rate = 20 °C/min

Cycle two:

Initial Temp: 180 °C

Final Temp: Room temperature

Ramp Rate = - 20 °C/min

Cycle three:

Initial Temp: 23 °C

Final Temp: 200 °C

Ramp Rate = 10 °C/min

DMTA Tg of the cured resins was determined with RSA III dynamic mechanical thermal analyzer (DMTA). Samples were heated from -50 to 250°C at 3°C/min heating rate. Test frequency was 6.28 rad/s. The Tg of the cured epoxy resin was obtained from the tangent delta peak.

CTE test Samples for CTE test were prepared and tested according to IPC-TM-650 2.4.41 by following steps:

1 : Ramp 10.00°C/min to Tg;

2: Isothermal for 5.00 min;

3: Ramp 10.00°C/min to 30.00°C; 4: Ramp 5.00°C/min to above Tg20°C;

5: Jump to 30.00°C UL94 Testing

The prepreg sheets were molded into a laminate and cured at 220°C for 3 hrs by a regular hot press machine. The final laminate was cut into the standard samples for UL-94 FR testing. UL94 vertical flame testing was conducted in a CZF-2 vertical/horizontal burning tester made by Nanjing Jiangning Analytical Equipment Company. The chamber size was 720 mm ^χ 370 mm x 500 mm, with natural gas as the burner gas resource. The chamber was opened during the whole testing process, with air flow around the testing device prohibited. Each specimen was ignited twice, with after flame time (AFT) tl and t2 recorded. AFT tl and t2 were obtained as follows: The test flame was applied to the specimen for 10 seconds and then removed. The length of time (tl) was the duration between the flame removal and the time at which the flame on the specimen extinguished. Once the flame had extinguished, the test flame was applied for another 10 seconds and then removed. The duration of the burning of the specimen (t2) was again recorded.

Water uptake

Water uptake was performed by exposing 4 or 5 coupons in steam (121 °C, 2atm) for 1 hour in an autoclave. The coupon was removed and quickly baked, then weighed to determine the water uptake.

Copper peel strength test

Copper peel strength was tested by an IMASS SP-2000 Slip/Peel Tester according to the method described in IPC TM-650 2.4.8.1. The 35 μηι standard copper foils were used for preparing laminates. Dk and Df Measurements

Samples were analyzed at room temperature with an Agilent 4991 A Impendence/Material Analyzer equipped with Agilent 16453 A test fixture. Calibration was done using an Agilent Teflon standard plaque using Dj/Df parameters provided by vendor. Thickness of Teflon standard plaque and all samples was measured by micrometer. Clear cast or Board pressing protocol:

a) Increase temperature to 220°C

b) Exert force with 24000 Pounds at 220°C, repeat several times to exhaust bubbles c) Keep constant pressure at 220°C for 2 hrs

d) Cool down to room temperature

Claims

1. A curable composition comprising:

a) an epoxy component comprising a dinaphthalene epoxy having the structure

wherein each Ri group is independently a C1-C20 hydrocarbon;

a is an integer in the range of from 0 to 6;

m is an integer in the range of from 0 to 5; and

b) a hardener component comprising

i) a naphthol novolac which is a reaction product of

I) from 1 to 99 weight percent 1 -naphthol and

II) from 1 to 99 weight percent 2 -naphthol;

ii) a phosphorus-containing composition which is the reaction product of an etherified resole with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; and iii) optionally a phenolic resin selected from the group consisting of a molecule having at least one substituted or unsubstituted naphthalene ring, a high functionality phenolic resin, and combinations thereof.

2. A curable composition in accordance with claim 1 further comprising a filler selected from the group consisting of natural silica, fused silica, alumina, hydrated alumina, talc, alumina trihydrate, magnesium hydroxide and combinations thereof.

3. A curable composition in accordance with any one of the preceding claims wherein the phosphorus composition is DOP-BN.

4. A curable composition in accordance with any one of the preceding claims further comprising a catalyst.

5. A curable composition in accordance with any one of the preceding claims further comprising a toughener.

6. A curable composition in accordance with any one of the preceding claims wherein the epoxy component is present in an amount in the range of from 20 weight percent to 80 weight percent, the naphthol novolac is present in an amount in the range of from 1 weight percent to 60 weight percent, and the phosphorus-containing compound is present in an amount in the range of from 1 weight percent to 60 weight percent, based on the total weight of the curable composition.

7. A curable composition in accordance with any of the preceding claims wherein the phenolic resin is present in an amount in the range of from 1 weight percent to 60 weight percent.

8. A curable composition in accordance with any one of claims 2-7 wherein the filler is present in an amount in the range of from 10 weight percent to 80 weight percent.

9. A curable composition in accordance with any one of claims 4-8 wherein the catalyst is present in an amount in the range of from 0.01 weight percent to 10 weight percent.

10. A curable composition in accordance with any one of claims 5-9 wherein the toughener is present in an amount in the range of from 0.01 weight percent to 70 weight percent.

11. A process for preparing the curable composition of any one of the preceding claims comprising:

a) contacting dihydroxydinaphthyl with an epihalohydrin in a reaction zone under reaction conditions to form a dinaphthalene epoxy;

b) contacting I) from 1 to 99 weight percent 1-naphthol; and

II) from 1 to 99 weight percent 2-naphthol;

in a reaction zone under reaction conditions to form a naphthol novolac composition; and

c) admixing i) the dinaphthalene epoxy

ii) the naphthol novolac composition; and

iii) an oligomeric compound comprising a phosphorus composition which is the reaction product of an etherified resole with 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide.

12. A prepreg prepared from the curable composition of any one of claims 1-10.

13. An electrical laminate prepared from the curable composition of any one of claims 1-10.

14. A printed circuit board prepared from the electrical laminate of claim 13.