HK1095850A - Flame retardant epoxy prepregs, laminates, and printed wiring boards of enhanced thermal stability - Google Patents
Flame retardant epoxy prepregs, laminates, and printed wiring boards of enhanced thermal stability Download PDFInfo
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- HK1095850A HK1095850A HK07103280.6A HK07103280A HK1095850A HK 1095850 A HK1095850 A HK 1095850A HK 07103280 A HK07103280 A HK 07103280A HK 1095850 A HK1095850 A HK 1095850A
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Description
Background
Epoxy resins that partially react (are promoted) with reactive organophosphorus compounds are known to have reduced flammability compared to base resins. Heretofore, Alumina Trihydrate (ATH) has been used as a filler in certain advanced epoxy resins to improve the properties of laminates and printed wiring boards produced from such resins.
While the flame retardant resins so formulated are satisfactory in many respects, there is a need for new formulated epoxy resins that have been partially reacted with reactive organophosphorus compounds that have greater thermal stability than the corresponding resins that have been blended with alumina trihydrate, particularly if improved thermal stability can be achieved without significant loss of flame retardancy and without significant cost increase. The present invention is believed to satisfy these needs.
As is known in the art, epoxy resins can be modified by reaction with a variety of different types of compounds containing active hydrogen atoms. The present invention relates only to epoxy resins which have been partially reacted with reactive organophosphorus compounds. Such active organophosphorus compounds contain active hydrogen atoms, which are: (i) directly to phosphorus in a dialkyl phosphonate, diaryl phosphonate, dialkyl phosphite, diaryl phosphite, or diaryl phosphine; (ii) to an oxygen atom directly attached to phosphorus (e.g., phosphinic acid, dialkyl phosphate, or diaryl phosphate); or (iii) in a substituent (such as a hydroxyl group) attached to the aromatic ring and thus activated, and the aromatic ring is bonded to phosphorus. Thus, for convenience, the term "phosphorus-promoted epoxy resin" is used to denote a curable epoxy resin composition formed by partially reacting an epoxy resin with a co-reactive (co-reactive) organophosphorus compound containing an active hydrogen atom directly attached to phosphorus or located in a substituent attached to an aromatic ring, and the hydrogen atom in the substituent is activated by the aromatic ring. Similarly, the term "plurality of phosphorus-promoted epoxy resins" refers to more than one such phosphorus-promoted epoxy resin.
Disclosure of Invention
According to the invention, boehmite (alumina monohydrate), when used with typical epoxy resins promoted with phosphorus, makes it possible to improve the thermal stability and to increase the ignition time of laminates formed from prepregs made with such reinforced resins. Such laminates have particularly high thermal stability and exhibit a similar longer light-off time as compared to the corresponding resins in which alumina trihydrate is used.
One of the embodiments of the present invention is an epoxy-containing formulation (also referred to as an "a-stage formulation") from which phosphorus-promoted epoxy resins can be formed, and into which boehmite can be introduced before, during, and/or after an appropriate stage in forming the remainder of the formulation. Another embodiment is a phosphorus promoted epoxy resin into which boehmite is introduced at an appropriate stage before, during, and/or after the formation of the remainder of the resin formulation. Another embodiment is a method of forming a prepreg, wherein (i) boehmite is introduced into a formulation useful for forming an epoxy resin promoted with phosphorus before, during, and/or after the remainder of the formulation has been present; (ii) (ii) applying the formulation formed in (i) to a suitable substrate to form a coated substrate or an impregnated substrate; and (iii) heating the at least one clad substrate or impregnated substrate formed in (ii) to produce a prepreg. Another embodiment is an improvement to producing a laminate from a plurality of prepregs in the form of a sheet or mat (mat) of fibrous substrates coated or impregnated with a formulation of an epoxy resin promoted with phosphorus. The improvement comprises increasing the thermal stability of the laminate by introducing a thermal stability-increasing amount of boehmite into the formulation before, during, and/or after the remainder of the formulation is formed.
The above and other embodiments of the invention will become more apparent from the ensuing description and claims.
Detailed Description
Epoxy resins for production promoted with phosphorus and their uses, including their use in forming prepregs, laminates, and copper clad laminates such as electrical laminate wiring boards, are well known in the art. See, for example, U.S. patents 5,036,135, 5,364,893, 5,376,453, 5,587,243, 5,759,690, 5,817,736, 6,291,626B1, 6,291,627B1, 6,296,940B1, 6,353,080B1, 6,403,220B1, 6,403,690B1, 6,486,242B1, and WO 01/42359a1, published in english on 6/14/2001. The entire disclosures of all of the above documents are incorporated herein by reference.
A variety of organophosphorus compounds can be used to form the phosphorus-promoted epoxy resin. As mentioned above, these organophosphorus compounds contain the following active hydrogen atoms: (i) phosphorus directly attached to a dialkyl phosphonate, diaryl phosphonate, dialkyl phosphite, diaryl phosphite, or diaryl phosphine; (ii) to an oxygen atom directly attached to phosphorus (e.g., phosphinic acid, dialkyl phosphate, or diaryl phosphate); or (iii) in a substituent (such as a hydroxyl group) attached to the aromatic ring and thereby activated, and the aromatic ring is bonded to phosphorus. Non-limiting examples of such organophosphorus compounds include diphenylphosphine, xylylphosphine, bis (3, 5-dimethylphenyl) phosphine, bis (2, 5-diethylphenyl) phosphine, dinaphthylphosphine, bis (biphenyl) phosphine, phenyltolylphosphine, naphthylphenylphosphine, 4-hydroxyphenyldiphenylphosphine, 4-hydroxyphenyldimethylphosphine, 2-hydroxy-1-naphthyldiethylphosphine, dimethyl phosphite, diethyl phosphite, dipropyl phosphite, dibutyl phosphite, diphenyl phosphite, dioctyl phosphite, diphenyl phosphinic acid, dibenzylphosphinic acid, dimethylphosphinic acid, dimethylphosphine oxide, diheptylphosphinic acid, dipropylphosphinic acid, phenyltolylphosphinic acid, methoxyphenyl phosphinic acid, methylheptylphosphinic acid, ethoxyphenylphosphinic acid, phenylxylylphosphinic acid, Diphenylphosphinobenzoic acid, dioctylphosphinic acid, hydroxyphenylphenylphosphinic acid, dioctylphosphite, 6H-dibenzo [ c, e ] [1, 2] oxaphosphorin-6-oxide, hydroxyphenyl (phosphinyl) benzoic acid, hydroxyphenyldimethylphosphonate, hydroxyphenyldiethylphosphonate, hydroxyphenyl-dipropylphosphonate, dihydroxyphenyldimethylphosphonate, dihydroxyphenyldiethylphosphonate, dihydroxyphenyldipropylphosphonate, bis (hydroxyphenyl) phenylphosphonate, bis (hydroxyphenyl) methylphosphonate, bis (hydroxyphenyl) ethylphosphonate, 2- (6-epoxy-6H-dibenzo [ c, e ] [1, 2] oxaphosphorin-6-yl-) -1, 4-benzenediol, and 2- (6-epoxy-6H-methylbenzo [ c, e ] [1, 2] oxaphosphin-6-yl) -1, 4-benzenediol.
A typical process for forming prepregs and laminates for printed wiring boards includes the following operations:
A) the epoxy-containing formulation is applied to or impregnated into the substrate by roll coating, dip coating, spray coating, other known techniques, and/or combinations thereof. The substrate is an inorganic or organic reinforcing agent in the form of a fiber, wool (fabric), fabric, or textile material, such as typically a woven or non-woven fibrous mat (fiber mat) containing, for example, glass fibers or paper.
B) The impregnated substrate is subjected to a "B-stage" by heating and selectively partially curing the epoxy resin formulation at a temperature sufficient to drive off the solvent in the epoxy resin formulation so that the impregnated substrate is dry to the touch and can be easily handled. The "B-staging" step is typically carried out at a temperature of from 90 ℃ to 210 ℃ for a period of from 1 minute to 15 minutes. The impregnated substrate resulting from the B-staging is referred to as a "prepreg". The temperature is most typically 100 ℃ for composite materials and 130 ℃ to 200 ℃ for electronic laminates.
C) If an electronic laminate is desired, one or more prepregs are stacked or laminated with one or more conductive materials, such as copper foil, in alternating layers (laid up).
D) The laminate is compressed under conditions of elevated temperature, pressure and time sufficient to cure the resin and form a laminate. The temperature of the lamination step is typically from 100 ℃ to 230 ℃, most often from 165 ℃ to 190 ℃. The lamination step may also be carried out in two or more stages, for example a first stage at 100 ℃ to 150 ℃ and a second stage at 165 ℃ to 190 ℃. The pressure is usually 50N/cm2To 500N/cm2. The lamination step is typically carried out for 1 minute to 200 minutes, most often 45 minutes to 90 minutes. The lamination step may optionally be carried out at a higher temperature for a shorter time (e.g. in a continuous lamination process) or at a lower temperature for a longer time (e.g. in a low energy compression process).
E) Alternatively, the resulting laminate, such as a copper clad laminate, may be post-treated by heating at elevated temperature and ambient pressure for a certain period of time. The temperature of the work-up is generally from 120 ℃ to 250 ℃. The work-up is usually carried out for 30 minutes to 12 hours.
F) Conductive printed circuits are typically applied to copper clad laminates.
It will be appreciated that the addition of boehmite to the formulation used in step a) above may be carried out before, during, and/or after the remainder of the formulation has been formed. Thus, for example, boehmite can be added to and dispersed in a solvent prior to the introduction of any other components. Alternatively, the boehmite can be added to and dispersed in the solvent after one or more other components of the formulation are added. At least during or after the addition of boehmite, subjecting the resulting mixture to high speed, high shear mixing such that the solid particles are dispersed and suspended in the liquid phase. Preferably, this mixing takes place after the appropriate surfactant has been introduced into the liquid phase, as this will help to form a mixture in which the solids are well dispersed and properly suspended in the fluid. In this regard, and without wishing to be bound by theory, it is hypothesized that the solids resulting from the addition of boehmite to the liquid phase at some appropriate stage still at least partially comprise boehmite. However, the present invention does not require that boehmite be retained in the formulation as boehmite. The solids obtained are within the scope of the invention, whatever the way they are present in the formulation, provided only that the prepregs and laminates ultimately produced from the formulation have an increased thermal stability due to the presence of these solids in the formulation used.
The boehmite additive is typically added to the liquid phase in finely divided particulate powder form so that it can be more easily suspended or dispersed in the fluid formulation. However, if the amount of shear from the mixer used is high enough to break up larger particles, boehmite having a larger particle size may be used as an additive. Typically, the boehmite additive has an average particle size of 0.1 to 120 microns, and typically 50% by weight of the particles have a particle size of at least 50 microns. Boehmite having an average particle size of 0.1 to 60 μm is preferable. More preferably boehmite having an average particle size of 0.1 to 30 μm. Boehmite having an average particle size of 0.1 to 10 microns is most preferred, particularly when 100% by weight of the particles have a particle size of up to 10 microns, 90% by weight of the particles have a particle size of up to 3.3 microns, 50% by weight of the particles have a particle size of up to 1.3 microns, and 10% by weight of the particles have a particle size of up to 0.6 microns.
The amount of boehmite used to produce the formulations of the invention may vary depending on, for example, the amount of thermal stability improvement desired. In general, any amount of boehmite that improves thermal stability can be used, and this amount can be readily determined in any known case by conducting some preliminary experiments using several different dosage levels and recording the thermal decomposition temperature of the cured composition. Typically, this amount is in the range of 5 to 100phr (excluding any other components). More desirably, the amount by weight is generally in the range of 10 to 50 parts per 100 parts of epoxy resin (phr) (excluding any other components). Preferably, this amount is in the range of 30 to 50 phr.
The preferred boehmite additive (Martoxal BN-2) for use in the practice of the invention is available from
Albemarle Corporation. It has the following standard specifications:
Na2o is less than or equal to 0.10 in total
CaO ≤0.03
Fe2O3 ≤0.03
SiO2 ≤0.06
Weight loss on combustion (%) of 17. + -.2
Specific surface area (BET), m2/g 15±5
Bulk Density (kg/m)3) 700±100
Particle diameter d50(μm) 1±0.2
Particle diameter d100(μm) 10±2
Any epoxy resin promoted with phosphorus suitable for forming prepregs for the production of laminates, in particular laminates for printed wiring boards and composites, may be used in the formulation. Such epoxy resins are preferably preformed, but may be formed in situ by using a phosphorus-free epoxy resin and a phosphorus-containing compound co-reactive therewith. It is also possible to use a mixture of a preformed phosphorus-promoted epoxy resin, a phosphorus-free epoxy resin, and a phosphorus-containing compound co-reactive with the phosphorus-free epoxy resin. For example, the documents cited above and incorporated herein describe many different phosphorus-promoted epoxy resins that can be used in the practice of the present invention.
An example of one type of phosphorus-promoted epoxy resin that can be used in the formulation is the resin formed in U.S. Pat. No. 5,376,453, mentioned above and incorporated herein. This type is formed from (i) aromatic and/or heterocyclic polyepoxide resins, free of phosphorus, optionally mixed with aliphatic epoxy resins; (ii) epoxy-containing phosphorus compounds such as alkyl or aryl glycidyl phosphonates or phosphates. Curing agents for use with this type of in situ generated phosphorus-promoted epoxy resin are aromatic polyamine curing agents, such as by trimerization of a 4: 1 mixture of toluene-2, 4-diisocyanate and toluene-2, 6-diisocyanate, followed by hydrolysis to produce NH2Those prepared with a value of 8.7% of product.
Another non-limiting example of the type of phosphorus-promoted epoxy resin that may be used in the formulation is the resin formed in U.S. patent 6,291,626, mentioned above and incorporated herein. This type is formed by reacting a linear epoxy resin having two terminal glycidyl groups with a phosphorus-containing dihydric phenol or naphthol such as 2- (6-epoxy-6H-dibenzo [ c, e ] [1, 2] oxaphosphorin-6-yl) -1, 4-benzenediol.
Another non-limiting example of the type of phosphorus-promoted epoxy resin that may be used in the formulation is the resin formed in U.S. patent 6,291,627, mentioned above and incorporated herein. This type is formed by reacting a phosphorus-containing compound having an active hydrogen-containing atom directly bonded to a phosphorus atom, such as 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, with a di-or polyfunctional epoxy resin by an addition reaction between the active hydrogen atom and an epoxide group.
Another non-limiting example of the type of phosphorus-promoted epoxy resin that can be used in the formulation is the resin formed in U.S. patent 6,353,080 mentioned above and incorporated herein. This type is formed from specific amounts of (i), (ii), (iii), and (iv), (i) an epoxy resin, (ii) a phosphonate ester such as an ester of methylphosphonic acid with a glycol or polyol, (iii) a nitrogen-containing crosslinking agent having at least two amine functionalities, and (iv) a lewis acid such as boric acid. Preferred catalysts for use in this system are benzyldimethylamine, tris (dimethylaminomethyl) phenol, or 2-phenylimidazole.
Yet another non-limiting example of the type of phosphorus-promoted epoxy resin that may be used in the formulation is the resin formed in U.S. Pat. No. 6,403,220 mentioned above and incorporated herein. This type is formed from a curable epoxy resin and tris (ortho hydroxyphenyl) phosphine in which, optionally, one or more of the phenyl groups may be substituted by alkyl groups, so that these components may be partially pre-reacted and the pre-reaction product introduced into the formulation, or the reactants themselves introduced into the formulation, to form the resin in situ.
Another non-limiting example of the type of phosphorus-promoted epoxy resin that may be used in the formulation is the resin formed in U.S. patent 6,486,242, mentioned above and incorporated herein. This type is formed from a novolak epoxy resin, a novolak resin, and a phosphorus compound such as 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or tris (4-aminophenyl) phosphine oxide, which is reactive with the epoxy resin or the novolak resin.
Other suitable phosphorus-promoted epoxy resins or components forming the same will now be apparent to those skilled in the art.
Other components that are desirably incorporated into the formulation are one or more surfactants, wetting agents, or dispersing agents, one or more curing agents, and one or more accelerators for the curing agent.
Suitable surfactants, wetting agents or dispersants are those agents which achieve optimum wetting of the additive such that the surface of the individual particles is covered with resin. These are typically available from suppliers such as BYK Chemie and Avecia Addities. The choice of a particular type of surfactant, wetting agent or dispersant depends on the desired properties of the resin and the laminate or printed wiring board.
Although the amount of surfactant may vary, typically, it is added to the formulation in an amount of 1% to 4%, preferably 1.0% to 2% by weight of the inactive additive.
Non-limiting examples of suitable curing agents that can be used include meta-phenylene diamine, diaminodiphenyl sulfone, diaminodiphenylmethane, diaminophenyltriazine, dicyandiamide, and sulfonamides. Among these, dicyandiamide is a preferred curing agent. The amount of curing agent incorporated into the formulation is a function of the Epoxy Equivalent Weight (EEW) of the resin, the functionality of the curing agent, and the molecular weight of the curing agent. The equation typically used to calculate the appropriate amount of curing agent to use is as follows:
accelerators that may be used in the production of the formulation include, for example, 2-phenylimidazole, benzyldimethylamine, N-methylimidazole, and 2-ethyl-4-methylimidazole. Generally, a weight ratio of 4 to 15 parts of curing agent per part of accelerator may be used, with a preferred weight ratio of 15: 1.
Typically, the solvent used for the phosphorus-promoted epoxy resin is a ketone, such as acetone. However, any other suitable type of solvent commonly used to form these formulations may be used. Examples of such other solvents include Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), 2-methoxyethanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, toluene, N-dimethylformamide.
If desired, reactive phosphorus-free flame retardants such as organophosphates, phosphites, phosphonates, or phosphoramidates, and metal salts thereof, which contain no substituents reactive with epoxide groups, may be included in the formulation. Other optional components that may be included in the formulation include ammonium phosphate, melamine cyanurate, melamine pyrophosphate, melamine polyphosphate.
The following examples are illustrative only and are not intended to limit the full scope of the invention to the specific means and materials used therein. In these examples, the phosphorus-promoted epoxy resin used is an epoxy novolac resin that has been patented that has interacted with a co-reactive organophosphorus compound. These resins are considered to be representative examples of present-day epoxy resins promoted with phosphorus.
Example 1
4-and 8-layer laminates from phosphorus-promoted epoxy and boehmite (50phr)
A solution of 8g of Dicyandiamide (DICY) and 0.52g of 2-methylimidazole (2-MI) in 72g of N, N-Dimethylformamide (DMF) was prepared. The solution was combined with a 320g solution of phosphorus-promoted epoxy resin (260g resin; EEW ═ 330) and 2.6g LP W20037 dispersant (BYK Chemie) in a 1L disposable beaker. To this mixture, 130g (50phr) of boehmite (BN-2; Martinswerk GmbH) and 50g of acetone were added and the resulting mixture was stirred with a Silverson L4RT laboratory stirrer at 6000rpm for 30 minutes. The well-dispersed mixture was applied to 13 pieces of 12 "x 12" woven glass cloth (manufactured by bgfinders under the trade name 7628) with a paint brush. Each sheet was hung in a well ventilated 170 ℃ oven for 3.5 minutes, cooled and trimmed to 10 ". Each sheet was determined to contain 50% of the resin mixture. Four 10 "x 10" pieces were stacked on top of each other and stapled together. Eight 10 "x 10" pieces were stacked on top of each other and stapled together. The 4-layer laminate was placed on a DuPont Tedlar double layer sheet of release film and covered with a double layer sheet of the same film. The stack is then placed between two metal plates. The stack of 8 layers was placed on a double layer sheet of DuPont Tedlar release film and covered with a double layer sheet with the same film. The laminate was then placed on a metal plate, covered with a 4-layer laminate. A third metal plate was used to cover the top of the 8-layer stack. The entire "book" was then heated at 170 ℃ for 60 minutes in a Carver compressor at 21,000 psi. The pressure was removed and the laminate was taken out and the UL-94 tape was cut using a wet saw. UL-94 ratings of V-0 were obtained from both laminates. Table 1 summarizes the data from these tests, where the values are the duration of combustion after the first and second ignitions.
TABLE 1
| 8-layer | 8-layer (repeat) | 4-layer | ||||
| 1stIgnition | 2ndIgnition | 1stIgnition | 2ndIgnition | 1stIgnition | 2ndIgnition | |
| 1 | 2.97 | 0.77 | 4.74 | 7.59 | 8.64 | 3.87 |
| 2 | 2.13 | 0.90 | 0.91 | 1.53 | 4.78 | 3.83 |
| 3 | 0.97 | 2.77 | 2.57 | 6.79 | 4.67 | 3.18 |
| 4 | 1.29 | 1.59 | 0.81 | 1.34 | 6.22 | 1.31 |
| 5 | 2.96 | 23.27 | 1.29 | 3.84 | 4.85 | 4.61 |
| Total time of day | 10.32 | 29.3 | 10.32 | 21.09 | 29.16 | 16.80 |
| Rating | V-1 (rerun) | V-0(31.41) | V-0(45.96) | |||
Example 2
Laminates were prepared from epoxy resins promoted with phosphorus and boehmite (30phr)
The method of example 1 is repeated except that the formulation contains 320g of the phosphorus promoted epoxy resin solution, 8g of DICY, 0.52g of 2-MI, 79.4g of DMF, 2.6g of LPW 20037 dispersant, 78g of boehmite, and 14g of acetone. A UL-94V-0 rating was obtained from both laminates. The data from these tests are summarized in table 2. As described above, the values given are the duration of combustion in seconds after the first and second ignitions.
TABLE 2
| 1stIgnition (second) | 2ndIgnition (second) | 1stIgnition (second) | 2ndIgnition (second) | |
| 1 | 1.23 | 4.53 | 4.45 | 5.49 |
| 2 | 0.73 | 7.03 | 8.05 | 1.91 |
| 3 | 1.64 | 1.80 | 4.03 | 4.81 |
| 4 | 2.38 | 4.17 | 4.14 | 0.97 |
| 5 | 2.27 | 6.05 | 4.18 | 1.91 |
| Total time of day | 8.25 | 23.58 | 24.85 | 15.09 |
| Rating | V-0(31.83 seconds) | (39.94 seconds) |
Example 3
Laminates were prepared from epoxy resins promoted with phosphorus and boehmite (10phr)
The method of example 1 is again repeated except that the formulation contains 320g of the phosphorus promoted epoxy resin solution, 8g of DICY, 0.52g of 2-MI, 79.4g of DMF, 2.6g of LPW 20037 dispersant, 26g of boehmite, and 19g of acetone. The 4-layer laminate was rated UL-94V-0 and the 8-layer laminate was rated V-1. Table 3 summarizes the results of these UL-94 tests.
TABLE 3
| 8-layer | 4-layer | |||
| 1stIgnition (second) | 2ndIgnition (second) | 1stIgnition (second) | 2ndIgnition (second) | |
| 1 | 2.25 | 8.07 | 2.82 | 0.88 |
| 2 | 4.29 | 6.93 | 2.60 | 0.89 |
| 3 | 2.65 | 9.47 | 2.03 | 0.89 |
| 4 | 2.67 | 8.13 | 4.03 | 3.32 |
| 5 | 5.73 | 11.15 | 3.08 | 7.60 |
| Total time of day | 17.59 | 43.75 | 14.56 | 13.58 |
| Rating | V-1(61.34 seconds) | V-0(28.14 seconds) | ||
Comparative example A
Preparation of laminates from epoxy resins promoted with phosphorus
The procedure of example 1 was repeated, except that the formulation contained only 350g of a solution of phosphorus-promoted epoxy resin, 8.75g of DICY, 0.57g of 2-MI, and 78.8g of DMF. UL-94V-0 ratings were obtained from 8-ply 4-ply laminates. The results of these UL-94 tests are summarized in Table 4.
TABLE 4
| 1stIgnition (second) | 2ndIgnition (second) | 1stIgnition (second) | 2ndIgnition (second) | |
| 1 | 4.94 | 3.93 | 2.36 | 1.12 |
| 2 | 6.03 | 9.01 | 6.49 | 1.99 |
| 3 | 1.03 | 4.22 | 5.44 | 2.23 |
| 4 | 2.69 | 3.29 | 3.94 | 0.99 |
| 5 | 6.49 | 5.31 | 4.23 | 2.25 |
| Total time of day | 21.21 | 25.76 | 22.46 | 8.58 |
| Rating | V-0(46.97 seconds) | V-0(31.04 second) |
Comparative example B
4-layer and 8-layer laminates were prepared from epoxy resin promoted with phosphorus and alumina trihydrate (50phr)
A1L disposable beaker was charged with a solution containing 320g of phosphorus-promoted epoxy resin solution, 8g of dicyandiamide ("DICY"), 0.52g of 2-methylimidazole ("2-MI"), and 72g of N, N-dimethylformamide ("DMF"). To this solution was added 2.6g of LPW 20037 dispersant (BYK Chemie), 130g of alumina trihydrate (TS-601; MartinswerkGmbH.) and 50g of acetone. The mixture was stirred with a Silverson L4RT laboratory stirrer at 5500-6000rpm for 30 minutes. The well-dispersed mixture was applied to 12 pieces of 12 "x 12" BGF Industries 7628 woven fiberglass cloth with a paint brush. Each block was hung in a well ventilated 170 ℃ oven for 3.5 minutes, cooled and trimmed to 10 ". Each tablet was determined to contain 50% of the resin mixture. Four 10 "x 10" pieces were stacked on top of each other and stapled together. Eight 10 "x 10" pieces were stacked on top of each other and stapled together. The 4-layer laminate was placed on a two-layer sheet of DuPont Tedlar release film and covered with a two-layer sheet with the same film. The stack is then placed between two metal plates. The 8-layer laminate was placed on a double-layer film of DuPont Tedlar release film and covered with a double-layer film of the same film. The laminate was then placed on a metal plate, covered with a 4-layer laminate. The top of the 8-layer stack was covered with a third metal plate. The entire "book" was then heated in a Carver compressor at 21,000psi for 60 minutes at 170 ℃. The pressure was removed and the laminate was taken out and the UL-94 tape was cut using a wet saw. UL-94 ratings of V-0 were obtained from both laminates. Table 5 summarizes the results of these UL-94 tests.
TABLE 5
| 8-layer | 4-layer | |||
| 1stIgnition (second) | 2ndIgnition (second) | 1stIgnition (second) | 2ndIgnition (second) | |
| 1 | 0.77 | 3.01 | 0.89 | 3.70 |
| 2 | 0.76 | 1.17 | 1.09 | 4.82 |
| 3 | 0.73 | 0.91 | 0.76 | 2.50 |
| 4 | 0.87 | 0.83 | 1.63 | 4.92 |
| 5 | 0.79 | 0.93 | 1.17 | 3.69 |
| Total time of day | 3.92 | 6.85 | 5.54 | 19.63 |
| Rating | V-0(10.14 seconds) | V-0(25.17 seconds) | ||
Example 4
Comparative experiments were performed to determine the thermal stability of several different laminates. In these experiments, laminates prepared from (i), (ii), (iii) were compared, (i) the additive-free base resin of comparative example A, (ii) the same additive-free base resin that had been mixed with 50phr of alumina trihydrate (TS-601), and (iii) the same additive-free base resin that had been blended with 50phr of boehmite (Martoxal BN-2). The results of the thermal stability measurements are summarized in table 6.
TABLE 6
| Laminated board | Temperature required for 5% weight loss (. degree.C.) |
| Base resin (comparative example A) | 372 |
| Base resin + TS-601 (comparative example B) | 358 |
| Base resin + boehmite | 391 |
It can be seen that the use of boehmite according to the invention results in a significant increase in thermal stability, as opposed to the addition of alumina trihydrate reducing the thermal stability of the composition.
Compounds described herein as chemical names or formulas, whether in the singular or plural, are considered to exist prior to coming into contact with another substance described by chemical name or chemical type (e.g., another component, a solvent). It is not important what, if any, chemical changes have occurred in the resulting mixture or solution, as such changes are the natural result of bringing the specified substances together under the conditions called for by this disclosure.
In addition, even though the claims may refer to substances in the present disclosure, such reference is to the substance being present in the disclosure immediately prior to first contacting, blending, or mixing with one or more other substances.
Unless it may be explicitly stated otherwise, if and as used herein, the article "a" or "an" is not intended to be limiting, nor should it be taken as limiting the specification or claims to a single component of the indicated article. Rather, unless the context clearly dictates otherwise, if and as used herein the article "a" or "an" is intended to cover one or more of such elements.
All documents referred to herein are fully incorporated by reference as if fully set forth in this document.
The invention also includes all modifications commensurate with the spirit and scope of the claims.
Claims (18)
1. A substantially halogen-free, phosphorus-promoted epoxy resin formulation suitable for coating or impregnating a substrate, wherein a thermal stability-enhancing amount of finely divided boehmite has been added to the formulation and a solid has been dispersed in the formulation.
2. The formulation of claim 1, wherein the amount is from 10 to 50phr, excluding other components of the formulation.
3. The formulation of claim 1, wherein the amount is from 30 to 50phr, excluding other components of the formulation.
4. A composition suitable for forming prepregs comprising an inorganic or organic reinforcing agent in the form of a fibre, a fleece, a fabric or a textile material impregnated and/or coated with a formulation according to any of claims 1 to 3.
5. The composition of claim 4, wherein the reinforcing agent is in the form of a fabric or textile material.
6. The composition of claim 4, wherein the composition is in the form of a woven or non-woven fibrous mat comprising glass fibers.
7. A prepreg formed from the composition of claim 4.
8. A prepreg formed from the composition of claim 5.
9. A prepreg formed from the composition of claim 6.
10. A composite formed from the composition of claim 5.
11. A printed wiring board formed from the composition of claim 6.
12. A laminate formed from the composition of claim 4.
13. A method of forming a prepreg having increased thermal stability, the method comprising:
A) applying and/or impregnating an inorganic or organic reinforcing agent in the form of a fiber, fleece, fabric, or textile material with a promoted epoxy-containing formulation that includes a solvent and to which has been added a thermal stability-enhancing amount of boehmite before, during, and/or after formation of the formulation and in which the solids have been dispersed and/or suspended, thereby forming a coated or impregnated sheet substrate; and
B) heating the substrate formed in A) at a temperature sufficient to drive off solvent from the formulation and optionally partially cure the epoxy formulation such that a prepreg is formed from the impregnated substrate that can be conveniently processed.
14. A method of forming a laminate having increased thermal stability, the method comprising:
A) applying and/or impregnating an inorganic or organic reinforcing agent in the form of a woven or non-woven fibrous mat, fleece, fabric, or textile material with a promoted epoxy-containing formulation that includes a solvent and to which has been added a thermal stability-enhancing amount of boehmite prior to, during, and/or after formation of the formulation and in which the solids have been dispersed and/or suspended, thereby forming a coated or impregnated sheet substrate; and
B) heating the substrate formed in A) at a temperature sufficient to drive off solvent from the formulation and optionally partially cure the epoxy formulation such that a sheet prepreg is formed from the impregnated substrate that can be easily handled;
C) forming a laminate including a plurality of the sheet prepregs formed in B); and
D) compressing the laminate formed in C) under conditions of elevated temperature, pressure and time sufficient to cure the resin and form a laminate.
15. The method of claim 14, wherein the laminate further comprises one or more sheets of conductive material to form an electronic laminate.
16. The method of claim 14, wherein a conductive printed wire is applied to the laminate.
17. The method of any of claims 13-16, wherein the amount that increases thermal stability is from 10 to 50phr, excluding other components in the formulation.
18. The method of any one of claims 13-16, wherein the amount that increases thermal stability is from 30 to 50phr, excluding other components in the formulation.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/678,019 | 2003-10-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK1095850A true HK1095850A (en) | 2007-05-18 |
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