Title of Invention

A PROCESS FOR MAKING A NANOPOROUS SUBSTRATE

Abstract ABSTRACT 3296/CHENP/2005 "A process for making a nanoporous substrate" This invention relates to a process of making a nonoporous substrate, such as the matrix in an electrical laminate, by grafting onto an organic resin backbone a thermolabile functionality by reacting hydrogen active groups of the organic resin with a compound containing thermolabile groups; then thermally degrading the thermolabile groups grafted on the organic resin to form a nonoporous laminate. Advantageously, the nanoporous electrical laminate has a low dielectric constant (Dk) because of the nonopores present in the laminate matrix.
Full Text

The present invention relates to a process for making a nanoporous substrate, such as electrical laminates having a low dielectric constant.
Background of the Invention
It is known to make electrical laminates and other composites from a fibrous reinforcement and an organic matrix resin such as an qpoxy-containing matrix. Examples of suitable processes usually contain the following steps:
(1) An epoxy-containing formulation is applied to, or impregnated into, a substrate by rolling, dipping, spraying, other known techniques and/or combinations thereof The substrate is typically a woven or nonwoven fiber mat containing, for instance, glass fibers or paper.
(2) The impregnated substrate is "B-staged" by heating at a temperature sufficient to draw off solvent in the epoxy formulation and optionally to partially cure the eqoxy formulation, so that the impregnated substrate can be handled easily. The "B-stagingl" step is usually carried out at a temperature of from 90oC to 210oC and for a time of from 1 minute to 15 minutes. The impregnated substrate that results from B-staging is called a "prqnieg" The temperature is most commonly 100°C for composites and 130oC to 200oC for electrical laminates.
(3) One or more sheets of prepreg are stacked or laid up in alternating layers with one or more sheets of a conductive material, such as copper foil, if an electrical laminate is desired.
(4) The laid-up sheets are pressed at high tonperature and pressure for a time sufficient to cure the resin and form a laminate. The temperature of this lamination step is usually between IWC and 230o0, and is most often between 165oC and 190oC. The lamination step may also be carried out in two or more stages, such as a first stage between
100oC and 150oC and a second stage at between 165o0 and 190oC. The pressure is usually between 50 N/cm2 and 500 N/cm'. The lamination step is usually carried out for a time of from 1 minute to 200 minutes, and most often for 45 minutes to 90 minutes. The lamination step may optionally be carried out at higher temperatures for shorter times (such as in

continuous laminatioa processes) or for longer times at lower temperatures (such as in low mergyprcss processes).
Optionally, the resulting laminate, for example, a copper-clad laminate, may be post-treated by heating for a time at high temperature and ambient pressure. The temperature of post-treatment is usually beween 120°C and 250*0. The post-treatment time usually is between 30 minutes and 12 hours.
The current trend of the electrical laminates industry requires materials with improved dielectric properties including lower dielectric constant (Dk) and loss factor (Df); superior thermal properties including high glass transition temperature (Tg) and decomposition temperature (Td); and good processability.
Heretofore, various methods have been used to try to improve the dielectric constant of electrical laminates made from epoxy-containing resin compositions including, for example, by adding various thermoplastic additives, such as polyphenylene oxide (PPG), polyphenylene ether (PPE), or allyiated polyphenylene ether (APPE), to the epoxy-containing resin composition.
It is desired to provide a new pathway to reduce the dielctric constant of electrical laminates made from organic resins. More particularly, it is desired to prepare modified organic resins, such as epoxy-containing resins, with thennolabile groups to lead to nanoporous matrixes upon curing.
Summary of the Invenion
The present invention is directed to a process of making a nanoporous matrix in an electrical laminate by grafting onto an organic resin backbone a thermolabile functionality by reacting the hydrogen active groups of the organic resin with a compound containing a thermolabile group; and then thermally degrading the thermolabile groups grafted on the organic resin, such that a nanoporous matrix is prepared. Such nanopores provide a low dielectric constant because of the air present in the nanopores and the lowest dielectric constant is for air.
In one embodiment, the present invention is directed to a process of making nanoporous epoxy-based electrical laminates by modifying the epoxy resin backbone with a thermolabile group through the reaction of the hydroxyl groups of the epoxy resin, and then by thermally degrading the thermolabile groups. Advantageously, the nanoporous electrical

laminate has a low dielectric constant (Dk) because of the nanopores present in the matrix. The process of the present invention also provides the following benefits: a nanoporous matrix with a controlled dispersion of nanopores; a controlled size of nanopores; a close porosity: and a standard processability of the laminate.
Brief Description of Drawing
Figure 1 is a scanning electron microscopy (SEM) image showing the inter-laminar fracture surface (resin-rich area) of a nanoporous epoxy-based electrical laminate.
Detailed Description of the Preferred Embodiments
Generally, the process of the present invention includes, as a first step, reacting (a) an organic resin having hydrogen active groups with (b) a compound containing a thermolabile group, so as to graft the thermolabile group onto the backbone of the organic resin by the reaction of the compound containing the thennolabile groups with the hydrogen active groups of the organic resin.
In a second step, the thennolabile group are degraded by subjecting the modified organic resin to a sufEicent temperature, typically temperatures of from about 120°C to about 220o0, to themally degrade the thennolabile groups, which in turn produces nano size voids in the organic resin matrix. In laminate production, heating the organic resin for thermolabile group degradation is typically carried out during the pressing step of the laminate.
In one embodiment of the present invoition, the organic resin may be selected from epoxy resins, phenolic resins, polimide resins, polyamide resins, polyester resins, polyether resins, bismaleimide triazine resins, cyanate ester resins, vinyl ester- resins, hydrocarbon resins, and mixture thereof. The hydrogen active groups can be selected from, for instance, amines, phenols, thiols, hydroxyls or alcohols, amides, lactams, carbamates, pyrroles, mercaptans, imidazoles, and guanidine.
In another embodiment of the present invention, the compound containing a thermolabile group may be a dicarbonate and its derivatives, a carbazate and its derivatives, and other compounds containing tert-buityi carbonate. Examples of compounds containing thermolabile group are, but not limited to, di-tert-butyl dicarbonate, di-tert-amyi dicarbonate, diallyl pyrocarbonate, diethyl pyrocarbonate, dimethyl dicarbonate, dibenzyl dicarbonate, tert-butyi carbazate and mixtures thereof The tert-butyl carbonate

thermolabile group is advantageously stable to many nucleophiles and is not hydrolyzed under basic conditions, but it may be easily cleaved under mid-acidic conditions or by thennolysis.
In one particular example of the present invention, epoxy resins containing bydzoxyl groups or phenolic resins can be advantageously used as the organic resin because epoxy resins are widely used in the electrical laminates industry and epoxy resins offer good processability. Di-tert-butyl dicarbonate can be conveniently used as the theramolabile group-containing compound because it is commercially available in large volumes.
In the present invention, the initial unmodified epoxy resin used may be any known epoxy resin chosen for its expected perfotmance, for example, brominated or bromine-free standard or high Tg standard, or low Dk standard and the like. The thermolabile groups (also called "foaming agent') are grafted on the epoxy backbone tbrough the reaction with the hydroxyl groups. The modified resin is stable at ambient temperature. During polymerization, thermolabile groups degrade, leading to gas generation whidi, in turn, produce voids in the polymerized q>oxy resin matrix. Because the foaming agedt is directly grafted onto the epoxy molecule, the statistical repartition of the voids is highty improved in comparison to the addition of non-grafted foaming agents. As a consequence, the voids in the epoxy matrix are smallo: (for example, the diameta of the voids may be less than 200 nm) and well-dispersed within the laminate. The continuous q)oxy matrix gives thermal resistance and medianical integrity to the system, whereas the voids decrease the dielectric constant, resulting in low Dk electrical laminates. For example, genorally, laminates having a Dk measured at 1 GHz of less than 5 may be obtained, howevo:, laminates having a Dk measured at 1 GHz of less than 4.2, preferably less than 4.0, more preferably less than 3.8, evea more preferably less than 3.5, may be obtained.
In one embodiment of the present invention, an epoxy resin is reacted directly, in an aprotic solvent, with a compound containing a thermolabile group to form a modified epoxy resin.
In another embodiment of the present invention, the thermolabile group is first reacted with a phenolic compound and that the resulting reaction product, a modified phenolic compound, is used as a curing agent to react with an epoxy resin, such as to introduce the thermolalide groups into the epoxy resin and form a modified epoxy resin.

The amount of thermolabile group used is selected such that the weight percent of tthetmolabile groups in a final formulation or varnish composition is from about 0.01 weight perceat (wt perceot) to about 10 wt percent, preferably from about 0.1 wt percent to about 5 wt percent, and more preferably from about 0.2 wt percent to about 2.5 wt percent The weight percentage of the composition above is given based on solids.
Optionally, a catalyst can be added to the compsition to acceloate the reaction between the compound containing the thermolabile group and the hydrogen active groiips of the organic resin. For example, hydroxylamine is known to catalyze the tertiary butoxy carbonyiation of alkjdamines at room temperature (~25°C). In another example, dimethyl amiac^yridyne acts as a catalj^ for iht reaction between hydro^Qd groups or phaK>l5 and di-tert-butyi dicazbonate at room temperature. Other catalysts useful in the present invention include, for example, auxiliaiy bases such as tnethylamine or N,N-diisopropylefliylamine.
To prepare a modified epoxy resin of the present invention, an epoxy resin having an avoage of more than one epoxy grot^> per molecule and, on average, more than zero hydroxyi group per molecule may be used- The epoxy resin may be selected from (1) an epoxy resin having an average of more than one epoxy groups -pec molecule and, on average, one or more hydroxyl groups per molecule, (2) a mixture of (1) and an epoxy resin having an average of more than one epoxy group per molecule but no hydroxyi groups. The exact selection of the epoxy resin component is determined from the intended propoties of the final products. Suitable epoxy resins, as used herein, include, for example, those having an epoxy equivalent weight of about 170 to about 3,500. Such epoxy resins are well described in, for example, U.S. Patent Nos. 4,251,594; 4,661,568; 4,710,429; 4,713,137; and 4,868,059, and The Handbook of Epoxy Resins by H. Lee and BL Neville, published in 1967 by McGraw-Hill, New York, all of which are incorporated herein by reference.
Epoxy resins, which can be used as one epoxy resin component in the present invention, may be represented by the general Formula (I):


wherein A is independently a divalent chemical bond, a divalent hydrocaibon group stuitably having from 1 to about 10, preferably from 1 to about 5, more preferably from 1 to about 3 carbon atoms, -S-, -S-S-, -SO-, —802 ~, -CO- or -0-; eadi R is independaitly a hydrogen atom or an alkylgroup suitably having from 1 to about 3 carbon atoms; each X is independeady a hydrogen atom or an alkyl group suitably having from 1 to about 10, preferably fixxm I to about S, more preferably fix)m 1 to about3 caibon atoms, or a halogenated atom such as Br c»^ CI; and n is anmnber lower than about 12.
To farther ioqirove heat resistance, the q>oxy resin component used in the present invention may cominise a multi-frinctional epoxy resin having an average of more than two q>oxy gfroaps per molecule. Preferred multi-frmctional epoxy resins include, for example, cresol-fotmaldehyde novolac epoxy resin, phenol-formaldehyde novolac epoxy resin, bisphenol A novolac epoxy resin, dicydc^>entadiene phenol Novolac q>oxy resin, ttis(g}ycidyloxyphenyI>mediane, tetraIds(glycidyioxypbcn5i)ethane, tetra^ycadyldiaminod^henylmeaiane and nuxtures Ihereofl To prevoit the resultant reaction inx>duct from haviag hi£^ viscosity, tiisCg|ycid)4oxyphenyl)methane, tetralds(gJycid)4oxyphen>1)eihane and tetraglycidyldiaminodq>heoylmediane are preferred, hi view of cost perfonnance, a cresol-formaldehyde novolac epoxy resin, phenol-formaldehyde novolac epoxy resin and bispheool A novolac epoxy resin are prefored. In view of didectric performance, dicydopentadioie phenol novolac epoxy resin is prefened. In addition, it is preferable to use a multifunctional q)oxy resin having narrow molecular wei^t distribution (for example, a Mw/Mn value of from about 1.5 to about 3.0).
Optionally, a suitable organic solvent can be used during the prqparation of the modified organic resin of the present invention to lower the viscosity of flie resin. Suitable organic solvents useful in the present invention include solvents diat do not contain hydrogen active grot^s. Preferably, qjrotic solvents may be conveniently xised, sudi as, for exantple, ketones such as acetone, me&yi ethyl ketone (MEK), and methyl isobutyl ketone; acetate of gjycol rihers such as propjdeoe glycol monomefliyi ether acetate (DOWANOL

PMA): aromatic organic solvents such as tohieae and xylene; aliphatic hydrocarbons; cyclic eOxTs; halogenated hydrocarbons; and mixtures thoeof.
hi one specific embodiment for illustration purposes, thennolabile t-butjdoxycaibonyi groi5>s may be grafted onto an epoxy backbone through the reaction with hydroxyL groups. For example, brominated epoxy resins sudi as D.E JL 560 or D.E.R. 539-EK80 and non-brominated q)oxy resms such as D.E.R. 669E, all conmiercially available from The Dow Chemical Coiiq>any, maybe SDccessfuUy modified in industrial solvents such as MEK or DOWANOL PMA.
hi another specific embodiment, phenolic resins and phenoHc derivatives may also be modified according to the present invention. A few examples of commercially available phenoUc resin include cresol novolac; bisphenol A novolacsuch as BFN17, commercially available from Arakawa; and mixtures thereof. Examples of phenoUc derivatives indude bisphenol A, bisphenol F, bisphenol S, tetrabromo bisphenol A, hydroquinone, and mixtures tho^ol Other phoiolic resins and phenolic derivatives including dihydric phenols, halogoiated dihydlric phoiols, pol>^ydric phenols, and halogenated polyhydric phenols usefiil in the present invoition are described in PCT Application WO 01/42359A1 and The Handbook of Epoxy Resins by H. Lee and K. Neville, published in 1967 by McGraw-Hill, New York, all of which are incorporated herein by reference.
It is noteworthy that the organic resin shows generally a lower viscosity in organic solvent after modification. Although not wishing to be bound by any theory, it would appear that the lower solution viscosity could be due to the decrease of the hydrogen-bonding efifect, because of the grafting of the thermolabile ffoup of the hj^oxyl ftmcdonalities.
In another spedfic ranbodiment for illustration purposes, epoxy resins are partly or fiiUy modified to q)oxy carbonate resins, for example, by carbonation of the epoxy group of an ^oxy resin undo* CO2 pressure at the s^propiiate temperature, such as, for example, 80°C with an adequate ion exchange resin. Sudi epoxy carbonate resins can be used as the epoxy resin component to obtain modified epoxy resins with thermolabile groups.
The modified epoxy resins are advantageously used in producing a laminate. During the pressing stage of a laminate, for example, at 180'*C, the thermolabile groups

degrade and gmerste volatile products, creaUng a porous matrix within the laminate resulting in a laminate with a reduced dielectric constant Most of the key properties of systems using the present invoition are not d&anged by the modified resins, such as varnish reactivity, prqneg processability, and laminate performances, such as thermal properties, flame retardancy, drillahility, diemical cleaning, and etching, and the like. However, the dielectric constant of the resulting laminate is advantageously reduced. Nanoporous laminates of the present invention may show an improvement of iq> to 20 percent compared to the same epoxy system wiHiout nanopores. Because the foaming agent is directly grafted onto the q>oxy molecule, voids are small (for example, 60 nm or less) and well-dispersed within the laminate. For c^timized processing conditions, the resulting laminate is homogeneous and, dqtending on the formulation, may be transparent, opalescent or opaque. When pores are adequately dispersed within the laminate and when &e pore diameter is optimized, the tou^ess of the laminate can be improved compared to the same organic system without nanores. Althou^ not wishing to be bound to any theory, the nanovoids may act as energy disperser for cracks, by inoreasing the radius at the cradk front line when the pores size is adequate. Becaxise the resin matrix is not altered by the nanoporous structure, the glass transition temperature shoi^ld not be negatively impacted.
Additional advantages for laminators using the modified epoxy resins of the present invoition are that laminators can produce laminates with unproved dielectric constants, while at the same time, laminators can carry on their expertise geno-ated with previously eustmg epoxy products, that is, same requiremeats for material handling, same formulation techniques, and same production conditions. Moreover, lanoinators can use current ^ass reinforcements and copper foils. The registration of the laminates remains the same.
Additional advantages for producers of printed circuit boards, which incorporate the modified epoxy resins of the present invention, are that producers can use production conditions that are similar to previously existing q)oxy systems. Producers can also obtain higher flexibility in systems design because they can tailor tiie dielectric constants of the same base material depending on Ihe level of porosity.
The q>oxy resm cooiposltions of the present invention may comprise, as an optional component, catalysts for catalyzing the reaction of the ^oxy groups of the epoxy resin and the hydroxyl groiqps of the curing agait. Sudi catalysts are described in, for

eacaniple,U.S. PatentNos. 3,306,872; 3,341,580; 3,379,684; 3,477,990; 3,547,881; 3,637,590; 3,843,605; 3,948,855; 3,956,237; 4,048,141; 4,093.650; 4,131,633; 4,132,706; 4,171,420; 4,177.216; 4,302,574; 4,320,222; 4,358,578; 4,366,295; and 4,389,520.
Examples of the suitable catalysts are imidazoles sudi as 2-metiiylimidazole; 2-phen)d imidazole and 2-etb34-4-meth}d imidazole; tertiary amines sudi as triethylamine, triprop)damine and tribulyiamine; phosphomnm salts such as ethyltriphenylphosphonium chloride, eth>4tnphai}dphosphoniimi bromide and ethyltriphaiyl-phosphoninm acetate; and ammonium salts such as beazyltrimethylammoxiimn chloride and benzyitrimeth>4ammoni\mi hydroxide, and mixtures tha:eo£ The amoimt of the catalysts used in &e present invention generally ranges from about 0.001 wei^ percent to about 2 weight pearceot, and preferably from about 0.01 to about 0.5 weight percent, based on the total weight of the reaction mixture.
In another spedfic embodiment for illustration purposes, imidazoles may be partly or fully modified with a compound containing a thermolabile group to form a latent catalyst
The q)oxy resin coniposition of flie presait invention may comprise known curing agents. Sudi curing agents include, for exanq>le, amine-curing ag«its such as dicyandiamide, diaminodiphenylmetiiane and dianainodiphenyisulfone; anhydrides such as hexahydroxyphthalic anhydride and styrene-maleic azihydride copolymers; imidazoles; and phoiohc curing agents sudi as phenol novolac resins; and mixtures thareo£ Such curing agents can be added to the composition immediately before curing, or can be included in the composition from the beginning if they are latent The amount of the curing agents used may normally range from about 0.3 to about 1.5 equivalent per epoxy equivalent of the epoxy components, and preferably from about 0.5 to about 1.1 equivalent p« epoxy equivalent oftbe epoxy components.
Imidazoles can be used to promote q>oxy homopolymerization. Depending on the varnish composition, a pure homopolymerized epoxy netwoiic can be obtained, or a hybrid network can be formed between the homopolymerized epoxy and the epoxy/hardener network.
The epoxy resin composition may also include a suitable organic solvent component to make handling of the ^>oxy resin varnish easier, and such solvents are added to Iowa: the viscosity of the above compositions. Known organic solvents can be used. The

solvents iiseful in the present invention indude, for example, ketones such as acetone and methyl ethyl ketone; alcohols sudi as medianol and ethanol; glycol ethers such as ethylene glycol method e&er and propylene glycol monometh^d e&er, acetate of glycol ethers sucdi as propyleQe glycol monomethyl ether acetate; amides such as N^N-dimethjdformamide; aromatic organic solvents sudi as toluene and x>4ene; aliphatic hydrocarbons; cyclic ethers; and halogeoated hydrocarbons.
In the practice of the present invention, the amount of the organic solvent CTopIoyed may range from about 10 to about 60 parts by weigjit, and preferably from about 20 to about 40 parts by wdgjht, based on 100 parts by wei^t of the above epoxy resin composition.
To inqffove storage stability, the epoxy resin coo^KJsitions of the presait invention may comprise a suitable stabilizer. Suitable stabilizers, as used herein, include, for example, alkylphenylsulfbnates or halogoiated alkylphoiylsulfonates such as mdhyl-p-toluenesulfonate, etbyl-p-toluenesulfonate and metbyl-p-dilorobenzenesulfonate. A preferred suitable stabilizer iised in the present invention is methyl-p-tolu«iesulfonate. Tbe stabilizer may suitably be used in an amount of from about 0.001 to about 10 weij^t percent, and more suitably frcnn about 0.01 to about 2 wd03t percent, based on the total amount of the composition.
As desired, the epoxy resin compositions of the present invaition may comprise an effective amount of other commonly employed additives for epoxy resins, for example, a reaction accelerator, pigment, dye, filler, sur&ctant, viscosity controUa, flow modifier, flame retardant and mixtures thereof
A process for preparing an electrical laminate using an organic resin composition of the present invention will be described below.
In a first step, the organic resin composition of the present invention is prq}ared by contacting an ^rpropriate amount of the organic resin with the compound containing the thennolabile groiq>, and with optional additives, such as solvent and catalyst; and reacting tiie mixture to modify the organic resin to introduce the thetmolabile groups into the back bone of the organic resin resulting in a modified organic resin.
Ths reaction conditions for the above reaction are selected to insure an e£5cient reaction between the compoimd containing &e thennolabile groiip and the

hydrogai active groiq) of the organic resin. The reaction temperature is usually limited by the thermal stability of the fbamolabile compound. Tlie reaction generally processes artjund room temperature (about 25°C), but can be from about 10°C to about 50°C, preferably between about 15°C and about 40°C, and more preferably between about 20*C and about 35X; for a period of from about 0.1 hour (h) to about 72 h, preferably fit)m about 0^ h to about 24 h, and more prderably fix}m aibout 0.5 h to about 12 h.
In a subsequent step, the above-modified organic resin, a curing agent and o&er desired additives are mixed to prq>are a vamish. The varnish is then inqnregoated into a substrate or web. The obtained impregnated substrate is dried at, for Gnamplc, from about 90°C to about 210*C, and preferably about 130*0 to about 200*0; for about 0.5 minute to about 60 minutes, and preferably from about 0.5 minute to about 30 minutes to obtain an organic resin-based ptepreg. As used herein, the substrate may include, for example, glass doth, ^ass fiber, glass piq>er, papa-, and similar organic substrates sudi as polyethylene, polypropylene, aramid fibers and polytetrafluoroeth>dene ^TFE) fibers.
In one specific embodiment of the present invention, the impregnated substrate is dried below the decomposition temperature of tiie grafted tbermolabile group. Consequently, no foaming or very limited foaming occurs during the drying stage, resulting in a pR^ireg with an improved cosmetic aspect
The obtained prqpr^ is then cut into a desired size. One singje cut prepreg or a plurality of cut prq>regs (desired number, for example, 2 to 10 pieces) are laminated and subjected to pressing at a pressure ot for example, from about 1 kgf'cm^ to about 50 kgfi'cm^, and preferably fiiom about 2 kgfcm^ to about 40 kgCan^; at a temperature ot for example, from about 120*0 to about 220*0; for a paiod of time of^ for example, from about 0.5 hoxir to about 3 hours to obtain a laminate. During this heating step the tiiomolabile groups are degraded and nanopores are formed in the laminate.
In one embodiment, multi-stage pressing can be advantageously used during lamination. As an illustration, a lower pressure of^ for example, from about 1 kgf'cm^ to about 10 kg£'erature o^ for example, from about 160*0 to about 220*C, for a period of time 0^ for example, from about 0.5 h to about 2 h. Multi-stage pressing can be used to control

tibe morpliology of the nanoporoiis laminate. It has been generally observed that, for a given vohone faction of voids, smaller and better dispersed pores lead to lower Dk than bigger and more aggregated pores.
An electrical conductive layo*maybe formed on the laminate witb an eldctrical conductive materiaL As used herein, suitable electrical conductive materials include, for example, electrical conductive metals such as copper, gold, silver, platinum and aluminum.
la another specific embodiment of the present invention, metal foil, such as copper foil, may be coated by Ihe organic resin varnish of the present invention. The varnish then may be partly cured (B-stage) or fiilly cured (C-stage) to obtain a resin coated metal foil, sudi as resin coated copper foil.
The electrical laminatfis manufactured, as desoibed above, can be preferably used as copper dad laminates and multi-layer printed circuit boards for electrical or electronics equipment
The present invention will be described in more detail with reference to the following Examples and Comparative Bxamples, whidb are not to be construed as limiting. Unless otherwise indicated, "part" means "part by weigjit".
The raw materials used for the chemical modifications and for the vanish formulati(»is in the Examples which follow were as follows:
D.E.iL 560 is a brominated epoxy resin, with an q)0xy equivalent wei^t (EEW) of 450, commoxdally available fix>m The Dow Qi«nical Company.
MEK stands for me^yi d3ayl k D.E.R. 539-EK80 is a brominated epoxy resin (80 percent nonvolatile (N.V.) in MEK), with an EEW of 450, commercially available fix)m The Dow Chemical Company.
DIBOC stands for di'tert-butjii dicatbonate, and is commercially available fiom Aldrich.
DMAP stands for dimethyl amino pyridine, and is commercially available from Aldrich.
DOWANOL PM is a propylene glycol monomethyl ether, commercially available firom The Dow Chemical Company.

DOWANOL PMA is a propyieae glycol monomethyl ether acetate, commcnaally available fiom The Dow Chemical Company.
DMF stands for dimeth^ifonnamide.
MeOH stands for methanol.
DICY stands for dicyandiamide (10 percent N.V. in DOWANOL PM/DMF 50/50).
2-MI stands for a-mdhjdimidazole (20 percent N.V. in MeOH).
2E-4MI stands for 2-ethyl-4-meaiyliimdazole (20 percent N.V. in MEK or MeOH).
2-PhI stands for 2-phfflrydimidazole (20 percent N.V. in MeOH).
Boric add (H3BO3) is used as 20 percent N.V. in MeOH.
Perstotp 85.36^8 is a phenol novolac (n = 4.5-5) (50 percent N.V. in DOWANOL PMA), with a hydroxyl equivalent wei^t (HEW) of 104, commercially available from Perstorp.
D.E.N. 438 is an qwxy novolac (n = 3.6) (80 percent N.V. in MEK), with an EEW of 180, commercially available from The Dow Chemical Company.
EPPN502H is an cpaxy novolac (80 percent N.V. in MEK), with an EEW of 170, commercially available from Nippon Ka3'akn.
MDI stands for 4,4'-methylaiebis(phaiyi isocyanate).
XZ 92505 is an epoxy/MDI flow modifier (50 percoit N.V. in DMF), with an EEW of 850, commercially available from The Dow Chemical Company.
XZ 92528 is a bromine-free epoxy resin (75 percoit N.V. in MEK/DOWANOL PM), with an EEW of 325, commercially available from The Dow Chonical Company.
SMA 3000 is a styrene-maleic anhydride copolymer solution (50 percent N.V. in DOWANOL PMA/MEK), with an anhydride equivalent wa^t (AnhEW) of 393, commercially available fix^m Atofrna.
RICON 130MA13 is a malemized polybutadiene, with an average molecular weight (Mn) of 2900, and an AnhEW of 762, commercially available from Sartomer.

SBM 1A17 is a styrene-butadiaie-inethyl methaCTjdate triblock polymer, commercially available fiom Atofina.
E.R,L. 4299 is a cycloaliphatic epoxy resin, with an EEW of 195, commercially available fix)m The Dow Chanical Company.
BPN17 is a bispheaol A phenol novolac, with a phenol equivalent weigjit of 120, commercially available from Arakawa Chemicals.
E-BPAPN is an epoxydized bisphenol-A phenol novolac, 79.6 percent solids in acetone with an EEW of 197 (based on solids), commercially available from The Dow Chemical Company.
TBBA stands for tetrabromo bisphenol-A.
D.E JL 330 is a di^yddjd ether of bisphenol-A, with an EEW of 180, commercially available from Tlie Dow Chemical Company.
D.E.R. 6615 is a solid epoxy resin, with an EEW of 550, commercially available from The Dow Chemical Con^any.
XZ-92535 is a phenol novolac solution, 50 percent solids in DOWANOL PMA, with a hydroxjd equivalent wagjbt (OHEW) of 104, commercially available from TTie Dow Chemical Company.
D.E.R. 592-A80 is a brominated q?oxy resin solution, 80 percent solids in acetone, with an EEW of 360 (based on solids), commercially available from ITie Dow Chemical Compsoiy.
D.E.R- 669E is a hight molecular wei^t diglyddyl ethw of bisphenol-A, wifri an EEW of 3245, commCTcially available from The Dow Chemical Company.
XZ-92567.01 is a brominated epoxy resin solution, EEW of 385, commercially available from The Dow Chemical Company.
XZ-92568.01 is an anhydride hardaier solution, with an EW of 398, commercially available from The Dow Chemical Company.
DMTA stands for dynamic mechanical themial analysis.
The anhydride hardener solution ("AHl") used in the examples was prqpared as follows:

An anhydride hardener solution (AHl) was prepared in a 10 L stainless steel reactor, equipped wilh a medianical stirrer, aad a heating jadc^ and fitted wifk a N2 inlet and a dropping funnel. 3671.9 Grams of DOWANOL PMA and 36232 grams of solid SMA 3000 were charged into the reactor and the mixture was heated to 90'C. After complete dilution, 730.7 grams of RICON 130MA13 was incorporated into the resulting solution. The resultii^ solution turned white turbid. After 30 minutes, the resulting solution was allowed to cool down to SO^C and 974.2 grams of an SBM 1A17 solution in MEJH (15 percent non-volatile) was introduced into the solution in the reactor at 80°C. A&et CQnq>lete cooling at anabient temperature, the resulting anhydride hardoier solution was turbid whitish homogeneous. The theoretical anhydride equivalent weight was 439 (based on solids).
The properties of the resultant laminates were tested iising die £3llowing testing methods and e^aratuses:
(IL\ Dielectric Measurements
A Hewlett Padcard Analyzer was used to measure Dk and Df in air, at ambient tempoature, from 1 MHz to 1 GHz. Sample size was about 10 cm x 10 cm with a thickness of about l.S mm.
(h\ Nuclear Magnetic j^^^napce (NMR^ Measiiremmts
A Brucker appaatas operating at 250 MHz was used to determine ^H- and "C-NMR spectra.
(c^ Thmnogravimetrv Analysis rPGA^
A DuPont apparatus TGA V5.1A was used to detennine the wei^t loss of modified apoxy resins fiom ambient temperature to SOO^C.
(£) Optical Microscopv
100 fun tiun sections were prepared with a rotating diamond saw. The sections were studied with a LEICA POLYYAR 2 li^t microscope operating with transmitted li^t and difBwaitial interference contrast according Nomarski. hnages were c£^tured with a Polaroid DMC digital camera.

(e\ Transmission Electron MiCTOScopv (TFM)
A glass fiber fi«e epoxy area ^vas sectioned petpeDdicular to the ^ass bundles wifli a LEICA ULTRACUT E ultramicrotome using a 45 degrees diamond knife. The section Hudmess was 120 ran (setting). Sections were studied witii a CM12 transmission electron microscope operating at 120 kV. Sections weare collected onto cleaned, 300 mesh copper grids. Imaging was recorded digitally in a Hitachi H-600 TEM at 100 kV. TEM rmaogcaphs were made of representative areas of the sections.
(f) Mode 1 laminate fracture toug^ess
Mode 1 laminate fracture toughness was d^eimined by controlled crack propagation in accordance with ASTM D5528. Toughness was measured by the strain energy release rate, Gfc, which is an intrinsic material property, non geometry-dependent A servo-hydraulic MTS 810 test frame was used to perform the test The fracture surfece analysis was done by SJ^l
(g) Scanning Electron Microscopy (SEM)
Samples were studied with a I£tachi S-4100 FEG SEM instrument with 4pi/NIH hnage digital image acquisitioa Samples were prepared as follows: The fracture regions of the mode 1 laminate fracture toug^ess samples were isolated from the ped test bars using a coping saw and one of the faces was selected for SEM. These smaller pieces of the fracture sur&ces were mounted on aluminum SEM stubs using carbon tape and carbon paint The mounts were sputter coated with Cr prior to imaging wi& the SEM. Images were acquired digitally at 5KV.
The standard methods used in the Examples to measure certain properties are as follows:
D>C Test Method PippfftyM^^gured
IPC-TM-650-2.3.10B Flammability of laminate [UL94]
IPC-TM-650-2.3.16.1C Resin content of prepeg, by treated weight [resin
content]
IPC-TM-650-2.3.17D Resin flow percent of prepreg [resin flow]
IPC-TM-650-2.3.18A Gel time, prepreg mataials [piepreg gel time]
IPC-TM-650-2.3.40 Thermal stability [Td]

ff C-TM-650-2.4.8C Peel strength of metallic clad laminates [copper peel
strengtiL]
PC-TM-650-2.4.24C Glass transition temperature and z-axis Thermal
expansion by Thennal Medvanical Analysis (TMA)
[Coefficient ofThemial Expansion (CTE)]
IPC-TM-650r2.4.24.1 Tmie to delamination (TMA Method) [T260, T288,
T300]
IPC-TM-650-2.4.25C Glass tramsition temperature and cure fector by DSC
[Tg]
ffC-TM-650-2.5.5.9 Permittivity and loss tangent, parallel plate, 1 MHz to
1.5 GHz [Dk/Df measurements]
IPC-TM-650-2.6.8.1 Thennal stress, laminate [solder float test]
IPC-TM-650-2.6.16 Pressure vessd method for glass epoxy laminate
integrity [high pressure cooker test (HPCT)]
Example 1
A brominated qx>xy resin, D.E.R. 560, was chemically modified with di-tert-butyl dicaibonate groups using the following composition'
Component Amount
D.E.R.560 250 g
DIBOC 30.4 g
DMA? 1.01 g
didiloromethane 200 g
A. Procedure of the chemical modification
The epoxy resin was first dissolved in dichloromethane (CH2CI2) at 25°C m an Erlemneyer flask with a magnetic stirrer. After complete dilution, solid di-ter-butyl dicaibonate was added to the resulting solution. Then a solution of dimethyl amino pyridine in dichloromethane was slowly charged into the solution in the flask. The resulting solution was stirred at ambient temperature for about 18 hours to ensure complete conversion.
The didiloromethane was evaporated in a ROTAVAPOR under vacuum, fi"om ambient temperature to 50'C. The dry resin was solid at room tanpCTature.

B. Nuclear Maiaigtic Resnnanre fNMR^ dbaracteaizatiog of the modified bromited epoxy resin
The 'H-NMR and "C-NMR spectra confinned that diendcal modification of the
brominated epoxy resin and the grafting of the di-tert-butyl dicarbonate groups onto the
resin had occurred.

These peaks are not due to free di-ter-buty! dicarbonate because the caibonyl would appesac at 146.5 ppm instead of 152.8 ppm.
^ T^q-m^l fJ^fff-a^erir-ation of Ifae modified brominated eooxv resin The thennal diaractecization was done by TGA.
Before modification, D.E.R. 560 was stable to > 200*'C. D.E.R. 560 started to decompose around 230'*C-250'C because of the standard thermolysis of the bromine grox^.
Modified D.E.R. 560 started to decompose at lower temperatare because of the thramolabile groups. A significant weigjit loss was seai between IVO^C and 220'C (4.77 percent), before the degradation of the bromine groups. The weight loss was due to the theimal breakdown of the thermolabile carbonate groups grafted onto the resin badcbone, leading to CO2 and isobutcne evqxnration. At higher temperature (T > 230'C-250°C), the standard thetmolysis of the bromine groups finally occuired.
Three other TGA nms were p^ormed with diffo-ent isotherm profiles. The resin weight loss was measured at the end of the isotherm:

- (1) At the ead of the isothetm at ISC^C for 4 nmiutes,.t3ie weight loss
was 0.72 percent;
- (2) At the Old of the isoth«ni at 1 SS^C for 60 minutes, the wei^t loss
was 4.48 percent; and
- (3) At the end of the isotham at 160'C for 60 minutes, the weight loss
was 1.14 percent
A brominabed epoxy resin, D,E.R. 560, was modified with di-tert-butjd dicarbonate groups using the same diemical modification procedure used in Exan^le 1, except with &e compositions as show in Table I below.

The modified resins in MEK or DOWANOL PMA could be used directly after modification, without stripping the reaction solvent
TGA and NMR results on dried sanq>les confirmed the modification of die q>oxy resins.
A brominated epoxy resin, D.E.R. 560, was chemically modified with di-tert butyl dicarbonate groups using the same chemical modification procedure as the one descaibed in Example 1, exc^t using the following composition:


lA'ten-hatyi dicazbonate was diarg6d to a reactor at ambient tempoature within 3 hoiits, and &en the solution was kept at ambient temperature for 4 hours.
The modified resin was used without further purification, and witiiout stripping the DOWANOL PMA fix)m the resin.
^■jgamples 4^ ^A 4p
A brominated qpoxy resin, D.EJR- 539-EK80, was partially modified \vi1h di-tert-but>i dicarbonate groups using the composition as shown in Table n below.

The KMR spectra showed that the chemical modification was successful and that no residual di-tert-butyl dicaibonate remained in the solution. NMR spectra also showed a portion of uoreacted secondary hydroxyl groups because of the under-stochiometric amount of di-tert-butyl dicaibonate.
Examples
In this Example, bisphenol A, a phenolic compound, was diemically modified with di-t«t-butyl dicaibonate groups according to the procedure described in Example 1. The composition used was as follows:
C^mpfflpt^t Amount
bisphenol-A 114 g
DBBOC 109 g
DMAP 3.66 g
dicbloromethane 200 g

NMR, DSC and TGA characterization confinned that bisphaxol-A was legenerated after heating to 220^0 and ihat degradation of the carbonate groups occurred.
•pxamnle 6
In this Example, a multifunctional phenol novolac resin, Perstorp 85.36^8, was cfaonically modified in ME^ with di-tert-butjd dicarbonate groups, using ihe procedure described in Example 1. Di-tert-butyl dicaibonate was diarged with an under-stochiometric ratio, therefore, only part of the phenolic groups were modified. The conq)Osition was as follows:
QomTwnent AmQUftt
Perstorp 85.36,28 2.03 g
DIBOC 0.24 g
DMAP 0.67 mg
MEK 2.9 g
Hie successful modification was confinned by NMR measurement After heafing to 220°C and degradation of the carbonate groups, phenolic -OH groups are regmerated.
In these Comparative Examples, azodicaibonamide, a known foaming agent, was used as an additive foaming agent and not grafted onto the organic resin; and compared with a reference material without azodicaibonamide or any other foaming agoit as desoibed in Table in below.
The incorporation of azodicarbonamide as a foaming agent into a resin leads to a non-stable varnish (precipitation ovemi^t) and a non-homogoieous laminate (macrobubbles whidi leads to ddamination).


Rxanmles 7A and 7B
In these Examples, a modified brominated epoxy resin, modified D.E.R. 560, was used to prepare electrical laminate formulations, as desoibed in the following Table IV.


The above results show that the modified D.E.R. 560, pi^ared according to Example 1, did not diange the reactivity of the resin and Tg remained similar. Also, no thermal degradation was observed during a DSC scan of the fully cured laminate sairple vq) to 230'Q wfaidi means that all themiolabile groups were degraded during the pressing stage. By increasing the amomit of modified D.E.R. 560, the appearance of &e laminate changed from whitish translucent to white opaque because of bigg^ and more numerous pores.

F?tqn?!« %\ fln^ ^? P"tl Comparative Example m
In these Examples, various amoxiiits of modified D.E.R. 560, prepared according to Example 1, were used in resin formulations, as described in Table V below.


The above results show that the use of modified D.E.R. 560, prq)ared according to Example 1, did not change die reactivity of the vamish and fhennal stability remained similar. The modified brominated epoxy resin D.E.R. 560 still acted as an efficient fire retardant (UL94 V-0). The increase of modified D.E.R. 560 dianged the appearance of the laminate, from clear yellow to white opaque, due to larger and more numerous pores. The dielectric constant of the nanoporous matedals in Examples 8 A and SB is much lower than the reference in Comparative Example m.
Bubbles in Example 8B are visible under the optical microscope. These bubbles are about 10-100 pm in diameter. Bubbles in tiie two olher samples were not visible under these conditions.
Transmission election noicroscopy of Example 8A showed very small bubbles in the range of from 0.01 \sm to 0.15 (xm, with a number mean average diameter of 0.059 ^m. The reference Comparative Example m shows no bubbles under these conditions.

ET^ffl^pl? 9 m4 C9mpw?tivg ffTimrp)^ TV
In these Examples, modified D.E.R. 560, prq>ared according to Example 2D, was used in a formulation of the present invention and compared to Comparative Example IV witiiout the modified D.E.R. 560, as described in the following Table VI.



The above results show that the use of modified D.E.R. 560, prepared according to Example 2D, did not change the reactivity of the varnish; and Tg, thermal stability and flame retaidancy remained similar, llie dielectric constant of the nanoporous matraial in Example 9 is mudi lower tiian the reference in Comparative Example IV.
Examples lOA and lOB and Comparative Example V
D.E JL 560 was modified according to the procedure described in Example 2D and used in the formulations descdbed in Table VII below.
Thin (0.40 mm thidc) laminates wore pressed with and without applying vaoram. Laminates pressed under vacuum and laminates pressed without vacuum showed similar thickness and resin contoit




Examples 12A and 12B and Comparative Example Vn
IQ these Examples, varying amoimts of modified D.E.R, 539, prepared according to the i«ocedure described in Example 4B, were used. As shown ia Table DC below, the use of modified D.E.R. 539 did not change the reactivity of the varnish and Tg remained similar. The increase of modified D.E.R. 539 changed the appearance of the laminate, fix>m clear yellow to white opaque, due to larger pores or due to a hight^ volume firaction of voids.




A modified biominated epoxy resin solution was prqiared in a S L glass reactor, equipped wi& a medhaoica] stirrer, and a heating jacket; and fitted with a N2 inlet and an addition fbnnel. 1225.4 Grams of DOWANOL PMA, 2275.8 g of solid D.E.R. 560 and 310.3 g of £ JLL. 4299 were charged into the reactor, and the solution was heated to 90^. After complete dilution, the solution was cooled down to 25"C. 136.5 Grams of di-tert-butyl dicaibonate and 0.38 g of dimethyl aminopyridine were added to the solution in 4 portions over a period of 2 hours. Foaming occurred after multiple charges of di-tert-butyi dicarbonate and dimethyl aminopyridine. After all of the di-tect-butyl dicarbonate and dimethyl aminopyridine was added, the solution was stirred for an extra 2 hours at 25°C. No foaming was noticed after this period of time. The solution was transparait. Then, 51.7 g of boric add solution (20 percent non-volatile in methanol) was added to the solution. The solution was stirred for an extra hour. The theoretical epoxy equivalent wei^t for the resultant resin was 401 (based on solids).

Examples 1SA.15D
Modified bisphenol-A phenol novolac solutions were prepared in a glass reactor, equipped with a medianical stiirer, and a heating jacket; and fitted with a N2 inlet and an addition fiinnel. The percentage of modification of BPN17 was 5.3 percent, 10 percent, 50 percent and 100 percent for Example 15A, Example 15B, Example 15C and Example 15D, respectively, as shown in Table XI below. The solutions of BPNl 7 were charged into tiie reactcn- and di-tert-butyi dicarbonate and dimethyl aminopyndine were incorporated into the solutions in portions over a penod of 2 h. Foaming occurred a&ex the charges of di-tol-butyi dicarbonate and dimediyl aminqpyridine were introduced into the reactor. After all of the di-tert-butjd dicarbonate and dimethyl aminopyridine were incorporated into the reactor, the solution was stirred fat an extra 2 hours. No foaming was noticed after this period of time. The solutions were transparent



This Example illustrates that the final morphology of the epoxy matrix varies ■vvitb the conceDtration of thermolabile groups.
f TJimplfts 17A-T 7n and Comparative Rxamnle TX
In these Exan^les, various concentrations of thennolabile groups were used to prepare the formulations as described in the following Table XIIL

This Example illustrates that the final morphology of the epoxy matrix varies with the concentration of thermolabile groups. A comparison betweea Example 16 and Example 17 shows that the final morphology of the epoxy matrix varies with the processiug conditions, sudh as the curing tanperature.

gTgmpl^ ? ^ ^d Comparative Example X
In these Examples, fommlations as described in the following Table XTV were compaied.

A modified hrominated epoxy resin solution was prepared in a 5 L glass Feactcn-, equipped with a mechanical stiirar, and a beating jacket; and fitted witii a N2 inlet and an addition funnel. 1131.9 Grams of DOWANOL PMA and 2102.1 g of solid D.E.R. 560 were charged into the reactor and the solution was heated to 90°C. After complete dilution, the solution was cooled down to SS'^C. 254.6 Grams of di-tert-bulyi dicafbonate solution (80 percent solids in toluene) and 11.4 g of dimethyl aminopyridine solution (5 percait solids in MEK) were added to the solution drop-wise over a period of 30 minutes. After all of the di-tert-butji dicarbonate and dimethyl aminopyridine w^e incorporated into Ifae reactor, the solution was stirred for an extra hour at 35°C. No foaming was noticed after this paiod of time. The theoretical epoxy equivalent wei^t of the resultant product was 470 (based on solids).
Examples 2QA-20E and Comparative Example XI
An epoxy resin solution was prepared by Maiding 608 g of D.E.R. 330, 392 g of D.E.R. 6615 and 420 g of acetone (herein "Epoxy Blend"). 28.4 Grams of the Epoxy Blend resin solution were weigjied in glass bottles. Magnetic stirrers were placed in the

bottles and the tanpoature was controlled at 22°C. Dicad^onate and dimethyl aminopyridine were incoiporated into the solution over a period of 30 minutes. The table below describes the compositions used. The solutions were stirred for 24 h at 22°C. After ibis period of time, solvajt was removed in a vacuum oven at 22'*C for 24 h. Clear, very viscous liquids wa-e finally obtained.
The teaq)erature at 1 wt percent loss was measured by Ihenno-gravimetry analysis (TGA). The results are shown in the following Table XV.

Example 20C gelled during heating to IPCC. This could be due to reactive multifunctional molecules coming from the decomposition product released during the cleavage of the thennolabile gro\^.

In these Examples, the formulations, as described in the table below, were prepared; and the properties of the prepregs aad laminates pr^>ared there&om were measured. The results are shown in the following Table XVL

In these Examples, &e formulations, as descaibed in the table below, were prepared; and the piopaties of the prqpregs and laminates prepared therefrom were measured. The results are shown in the following Table XVn.



Example 23
A modified 2-efliyi-4-methyl imidazole solution was prepared in a glass botde, equipped with a msgn^c stirrer. 11.0 Grams of 2-efcyl-4-meth}d imidazole solution (20 percent solids in DOWANOL PMA) was weired in the glass botfle; and 5.45 g of di-tert-butyl dicaibonate solution (80 percent solids in toluene) was incorporated into the solution drop-wise over a period of 5 minutes, at 20°C. Foaming happened during &e incorporation of di-tert-butyi dicarbonate. After all of the di-tat-butyi dicsarbonate had been incorporated into the bottle, the solution was stirred for 48 h at 20*'C. No foaming was noticed alter &is pedod of time. The solution was transparent
g-Ttgrnrl'^ 7A^-2^'P and Comparative Examples XH-XIV
ID these Exanq)Ies, the formulations, as described ia the table below, were prepared; and the ivc^>erties measured are shown in Tables XVm and XIX below.



This Example shows that modified 2-ethyl-4-fflethyl imidazole solutioa from Example 23 acts as a lateait/blodced catalyst At temperature lower &an the unblocking temperatuFe, the modified 2-eth)d-4-metih>d imidazole solution from Example 23, shows no catalytic activity or a much lower catalytic activity than 2-ethyl-4-metbyl imidazole. When the tmipecature readies the unblocking temperature, the catalytic activity of the modified 2-eOryi-A-mcHhyi imidazole solution firom Example 23 ino-eases. Furthermore, the modified 2-eQiyl-4-meth3d imidazole solution from Example 23 shows almost tiie same catalytic efBdency than 2-ethyl-4>methyl imidazole at a temperature higho: tiian the unblocking temperature.
Example 25
A modified phenol novolac soliition was prepared in a glass bottle, equipped with a magnetic stirrer. 21.51 Grams of XZ-92535 phenol novolac resin soliition (50 percent solids in DOWANOL PMA) ware wdghed in the glass bottle. The phenol novolac resin was modified witii a stodiiometric amount of di-tert-butyl dicarbonate in order to cap all phenol groiq)s. 28.15 Grams of di-tat-butyi dicarbonate solution (80 percent solids in toluene) and 0.38 g of dimetbyl aminopyridine (solid) were incorporated into the solution in

5 portions over a paiod of Ih, at 20oC while stiiring. Foaming happened daring the incorporation of di-tat-butyl dicarbonate. After all di-tert-butyl dicariwnate has been incorporated into the botde, the solxrtion was stirred for 18h at 20°C. No foaming was noticed after this period of time. The solution was transparent, with a low viscosity.
The Cannon-Fenske viscosity of XZ-92535 was II66.1 cSt; and the Cannon-Fenske viscosity of the modified XZ-92535 was 29.1 cSt
This Example shows that capping the phenol groups of the phenol novolac resin with tert-butyi caibonate group drastically reduces thee solution viscosity, probably because of less hydrogen bonding effect
Example 26
A modified brominated epoxy Tesin solution was prepared in a glass bottle, equipped with a magnetic stirrer. 139.3 Grams of D.E.R. 560 brominated epoxy resin solution (70 poceot solids in DOWANOL PMA) was weired in fee glass bottle, 10.6 Grams of di-tert-butyl dicarbonate solution (80 percent solids in toluene) and 0.143 g of dimeth)4 aminc^jyridine (solid) were incorporated into the solution in portions over a period of 15 minutes, at ZS^C under stirring. Foaming happened during the incorporation of di-tert-butyl dicarbonate. After all of the di-tot-butyl dicarbonate was incorporated into the solution, Ihe solution was stirred for 48 h at 25°C. No foaming was noticed after this period of time. The solution was transparent, with a low viscosity.
The Cannon-Fenske viscosity of D.E.R. 560 brominated epoxy resin solution was 262.3 cSt; and the Caimon-Fenske viscosity of the modified D.E.R. 560 brominated epoxy resin solution was 198.0 cSt
This Example shows that capping Ihe secondary hydroxy! groups of ihe brominated epoxy resin solution with tert-butyl caibonate groups reduces the solution viscosity, probably because of less hydrogen bonding effect
Exaipplg?7
To perform the modification in this Example, a 12 L round bottomed flask with a 5-neck fitted lid and equipped with a condenser, mechanical stirrer, N2 inlet, addition funnel and thermocoiiple was used. An 80 percent solids solution of D.E.R. 592 (10 kfe dark brown solution) was charged into the flask followed by the addition of acetone (589 g)

to reduce the solution viscosity. Di-tert-butyli dicarbonate (168.7 g, colorless liquid) was thai added to the reactor and the solution was heated to 40°C. Dimethyl amioopyridine (0.48 g, white oystalline solid) was dissolved in acetone and added drop wise to the solution. The addition proceeded over a 30-minute time period to reduce the amount of foaming in the reactor. After the addition was complete, the solution was stirred for an additional 3 hours. At the beginning of this time period, the solution was dark brown in color and filled with bubbles. At completion, no bubbles remained.
Examples 28A-28D
In these Examples, the formulations, as described in the table below, were prqrared; and the properties measured are shown in Tables XX and XXI below.




A modified hight molecular weight epoxy resin solution was prepared in a 11 glass reactor, equipped with a mechamcal stirrer, and a heating jacket; and fitted with a N2 inlet and an addition fiunnell. 316.6 Grams of D.E.R. 669E solution [40 percent NV in DOWANOLPMA] were charged into the reactor and the temperature was controlled between 25°C and 30oC. 118.8 Grams of di-tert-butyi dicaibonate solution [80 percent NV in toluene] and 5.32 g of dimethyl aminopyridine solution [10 percent N.V. in MEK] were added drop-wise to the solution over a period of 2 hours. Foaming occurred during the incorporation of di-tert-butyl dicaibonate and dimethyi aminopyridine. After all of the di-tert-butyl dicaibonate and dimethyl aminopyridine were incorporated into the solution, the solution was stirred for an extra 2 hours at 2S°C. The solution was transparent The theoretical epoxy equivalent weight was 4179 (based on sohds).
The modified D.E.R. 669E solution was then used as an epoxy-functional foaming agent additive in electrical laminates formulations.
The Cannon-Fenske viscosity at IS^C of D.E.R. 669E sohation [40 percent N.V.] was 1542 cSt; and the Cannon-Fenske viscosity at 25°C of the modified D.E,R. 669E solution [40.4 percent N.V.] was 743 cSt
hi this Exan^Ie, the formxilation, as desoibed in the table below, was prepared and the properties measured are shown in Table XXHI below.



The dielectric constant Dk of the nanoporous laminate of the Example 31 was reduced by 7.5 percent compared to the non-porous Comparative Example XV wilh the same matrix c(nnposition, except the nanoporous additive. The loss &ctor Df was also reduced by 18 percent Despite the nanoporous stmcture, the water uptake and the solder resistance remained unchanged. The strain energy release rate Gic of the nanoporous laminate of the Example 31 was increased by over 32 percent compared to the non-porotis Comparative Example XV with the same matrix composition, except the nanoporous additive. The fan-shaped epoxy fracture regions of the Example 31 (see Figure 1) indicate ductile deformation of the epoxy resin rich regions. Although not wishing to be bound by any theory, the nanovoids can act as energy disposers for cracks by increasing the radius at the crack front line, if the pores size is adequate. Despite the higher toughness, the glass transition temperature remained unchanged. Sub-micron size domains or cavities are noticed in the epoxy at highter magnification. The average pores diameter appears to be about 100 nm, ranging from less than 30 nm to less than 200 nm. Because of the distortion of the sample, precise analysis of the pores size was not performed on the SEM picture.


WE CLAIM:
1. A process for making a nanoporous substrate comprising the steps of:
(a) grafting onto a backbone of a reactive organic resin, a thermolabile functionality by reacting hydrogen active groups of the reactive organic resin with a compound containing thermolabile group and capable of being grafted onto the reactive organic resin;
(b) preparing a composition by blending the reactive organic resin containing thermolabile groups grafted thereto from step (a) with at least a curing agent; and
(c) thermally degrading, at a temperature of up to about 220°C, the thermolabile groups grafted on the organic resin such as to produce a nanoporous substrate.

2. The process as claimed in claim 1, wherein the substrate is a laminate.
3. The process as claimed in claim 1, wherein the organic resin is selected from the group consisting of epoxy resins, phonetic resins, polyimide resins, polyamide resins, polyester resins, polyether resins, bismaleimide trialing resins, cyanine ester resins, vinyl ester resins, hydrocarbon resins, and mixture of thereof.
4. The process as claimed in claim 1, wherein the organic resin is an epoxy resin.
5. The process as claimed in claim 1, wherein the organic resin is a brominates epoxy resin.

6. The process as claimed in claim 1, wherein the organic resin is a phosphorus-containing epoxy resin.
7. The process as claimed in claim 1, wherein the organic resin is an epoxy resin with an epoxy equivalent weight higher than 500.
8. The process as claimed in claim 1, wherein the hydrogen active group is selected from the group consisting of amines, phenols, thiols, hydroxyls, alcohols, amides, lactams, carbamates, pyrroles, mercaptans, imidazoles, guanidine and mixtures thereof.
9. The process as claimed in claim 1, wherein the compound containing the thermolabile group is selected from the group consisting of dicarbonates, derivatives of dicarbonates, carbazates, derivatives of carbazates, and mixtures thereof.
10. The process as claimed in claim 1, wherein the compound containing the thermolabile group is tert-butyl dicarbonate.
11. The process as claimed in claim 1, wherein the thermolabile group is a carbonate.
12. The process as claimed in claim 1, wherein the thermolabile group is tert-butyl carbonate.

13. The process as claimed in claim 1, wherein the thermolabile group is present in the composition in an amount such that the weight percent of thermolabile groups in the varnish is between 0.01 weight percent and 10 weight percent, based on solids.
14. The process as claimed in claim 1, including a solvent.
15. The process as claimed in claim 14, wherein the solvent is a ketone, an acetate of glycol ethers or mixtures thereof.
16. The process as claimed in claim 14, wherein the solvent is present in an amount of from 10 parts to 60 parts.
17. The process as claimed in claim 1, including a catalyst for the reaction between the organic resin and the compound containing the thermolabile group.
18. The process as claimed in claim 17, wherein the catalyst is dimethyl aminopyridyne.
19. The process as claimed in claim 1, wherein the reaction between the organic resin and the compound containing the thermolabile group is done at a temperature of from 15°C to 45°C.
20. The process as claimed in claim 1, wherein it comprises adding a thermoplastic compound to the varnish to lower the dielectric constants.

21. The process as claimed in claim 20, wherein the thermoplastic compound is polyphenylene ether, polyphenylene oxide, or allylated polyphenylene ether.


Documents:

3296-chenp-2005 abstract.pdf

3296-chenp-2005 claims.pdf

3296-chenp-2005 correspondence-others.pdf

3296-chenp-2005 correspondence-po.pdf

3296-chenp-2005 description(complete).pdf

3296-chenp-2005 drawings.pdf

3296-chenp-2005 form-1.pdf

3296-chenp-2005 form-18.pdf

3296-chenp-2005 form-26.pdf

3296-chenp-2005 form-3.pdf

3296-chenp-2005 form-5.pdf

3296-chenp-2005 others.pdf


Patent Number 236308
Indian Patent Application Number 3296/CHENP/2005
PG Journal Number 44/2009
Publication Date 30-Oct-2009
Grant Date 20-Oct-2009
Date of Filing 06-Dec-2005
Name of Patentee DOW GLOBAL TECHNOLOGIES INC.
Applicant Address Washington Street, 1790 Building, Midland, MI 48674
Inventors:
# Inventor's Name Inventor's Address
1 MARESIN, Catherine 15, Route de Vienne, F-69007 Lyon
2 MERCIER, Regis 17, Rue Joannes Gazague, 69540 Irigny
PCT International Classification Number C08J9/00
PCT International Application Number PCT/US2004/015772
PCT International Filing date 2004-05-20
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/456,127 2003-06-06 U.S.A.