Patent Application
20140221529
The invention relates to flame retardant compositions, which comprise a mixture of a salt of phosphinic acid and 6H-dibenz[c,e][1,2]oxaphosphorin-6-oxide in a polyfunctional epoxide compound.
Flame retardants are added to polymeric materials (synthetic or natural) to enhance the flame retardant properties of the polymers. Depending on their composition, flame retardants may act in the solid, liquid or gas phase either chemically, e.g. as a spumescent by liberation of nitrogen, and/or physically, e.g. by producing a foam coverage. Flame retardants interfere during a particular stage of the combustion process, e.g. during heating, decomposition, ignition or flame spread.
There is still a need for flame retardant compositions with improved properties that can be used in different polymer substrates. A particular need is seen in suitable flame retardant compositions for the manufacture of glass-fibre reinforced epoxy prepregs, laminates, and printed circuit boards, as well as printed wiring boards derived thereof.
Increased standards with regard to safety and environmental requirements result in stricter regulations. Particularly known halogen containing flame retardants no longer match all necessary requirements. Therefore, halogen free flame retardants are preferred, particularly in view of their better performance in terms of smoke density associated with fire. Improved thermal stability and decreased delamination tendency are further benefits of halogen free flame retardant compositions.
WO 00/02869 discloses polyphosphate salts of a 1,3,5-triazine compound and its use for flame retardant compositions.
U.S. Pat. No. 5,084,546 discloses flame retardant epoxy resin compositions, wherein hydroxyalkyl phosphine oxides are present as active components.
Published PCT/EP 2008/053474 discloses flame retardant epoxy resin compositions, wherein 6H-dibenz[c,e][1,2]oxaphosphorin-6-oxide is present as an active component.
It has surprisingly been found that polymers with excellent flame retardant properties are prepared in the event that combinations of a salt of phosphinic acid and 6H-dibenz[c,e][1,2]-oxaphosphorin-6-oxide are added to a polyfunctional epoxide compound.
Moreover, the quality of the laminates, such as the laminate surface smoothness or laminate integrity, is strongly increased and their delamination tendency significantly decreased as compared to laminates containing only one of the mentioned flame retardant components.
The invention relates to a composition, which comprises
The compositions according to the invention attain the desirable V-0 rating, according to UL-94 (Underwriter's Laboratories Subject 94) and other excellent ratings in related test methods especially in glass fibre reinforced compositions where conventional flame retardants tend to fail.
The compositions according to the invention are characterized by their excellent thermal and mechanical characteristics. In the context of the description of the invention, mechanical stability is defined as the ability of a laminate to withstand delamination upon heating or mechanical stress. Thermal stability is defined as the degree of resistance against foaming upon heating. For a more precise differentiation in thermal stability of flame retardant compositions, physico-chemical methods, such as thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC), can be used.
The flame retardant epoxy resin compositions of the present invention are especially useful for the manufacture of prepregs and laminates thereof and are used for the preparation of printed circuit boards and printed wiring boards, or as structural segments in transportation vehicles (trains, planes, ships, automotives, etc.) and in construction applications (dry walls, floorings, beams, etc.).
A preferred embodiment of the invention relates to a composition, which comprises
a) 0.05-30.0 wt.-% of the phosphinic acids (I) or (II);
b) 0.10-40.0 wt.-% of 6H-dibenz[c,e][1,2]oxaphosphorin-6-oxide;
c) 60.0-95.0 wt.-% of a polyfunctional epoxide compound; and
d) 0.10-40.0 wt.-% of a hardener compound.
The compositions, as defined above, comprise the following components:
Component a)
The term salt of phosphinic acid comprises within its scope preferably a metal salt, for example an alkali metal or alkaline earth metal salt, e.g. the sodium, potassium, magnesium or calcium salt or the iron(II), iron(III), zinc or boron salt.
According to a preferred embodiment, the composition comprises the aluminium salt of phosphinic acid (aluminium hypophosphite).
According to an alternative embodiment, the term salt comprises non-metallic salts, e.g. the acid addition salts obtainable by reaction of phosphinic acid with ammonia or amines, e.g. the (C1-C4alkyl)4N+, (C1-C4alkyl)3NH+, (C2-C4alkylOH)4N+, (C2-C4alkylOH)3NH+, (C2-C4alkylOH)2N(CH3)2+, (C2-C4alkylOH)2NHCH3+, (C6H5)4N+, (C6H5)3NH+, (C6H5CH3)4N+, (C6H5CH3)3NH+ or the NH4+ salt.
Among the acid addition salts the ammonium, (C1-C4alkyl)1-4ammonium or (2-hydroxyethyl)1-4ammonium, e.g. tetramethylammonium, tetraethylammonium or the 2-hydroxyethyltrimethylammoniurn salt are particularly preferred.
The term phosphinic acid comprises within its scope derivatives of phosphinic acid, H2P(═O)OH, wherein one or two hydrogen atoms, which are directly attached to the phosphorus atom, have been substituted by organic substituents, particularly C1-C6alkyl, aryl, e.g. phenyl, aryl-C1-C4alkyl, e.g. benzyl or 1- or 2-phenethyl, or (C1-C4alkyl)1-3aryl.
Suitable phosphinic acids are represented by the structural formulae
in which
R1 and R2 represent hydrogen or a linear or branched C1-C8alkyl radical, or a phenyl radical; and
R3 represents a linear or branched C1-C10alkylene, arylene, alkylarylene, or arylalkylene radical;
The term phosphinic acid comprises within its scope the tautomeric form HP(OH)2, wherein the hydrogen atom which is directly attached to the phosphorus atom is substituted by an organic substituent, particularly C1-C6alkyl, aryl, e.g. phenyl, aryl-C1-C4alkyl, e.g. benzyl or 1- or 2-phenethyl, or (C1-C4alkyl)1-3aryl.
According to a particularly preferred embodiment, the salt of a phosphinic acid (I) is represented by the formula
in which
R1 and R2 represent hydrogen or a linear or branched C1-C8alkyl radical, or a phenyl radical,
M represents (C1-C4alkyl)4N, (C1-C4alkyl)3NH, (C2-C4alkylOH)4N, (C2-C4alkylOH)3NH, (C2-C4alkylOH)2N(CH3)2, (C2-C4alkylOH)2NHCH3, (C6H5)4N, (C6H5)3NH, (C6H5CH3)4N, (C6H5CH3)3NH, NH4, an alkali metal or earth alkali metal ion, or an aluminium, zinc, iron or boron ion;
m is a numeral from 1-3 and indicates the number of positive charges on M; and
n is a numeral from 1-3 and indicates the number of phosphinic acid anions corresponding to Mm+.
A highly preferred embodiment relates to a composition, wherein the salt of a phosphinic acid (I) is represented by the formula
Component b)
The oxaphosphorinoxide (II) is represented by the following structural formula:
which can be named as 6H-dibenz[c,e][1,2]oxaphosphorin-6-oxide, 3,4:5,6-dibenzo-2H-1,2-oxaphosphorin-2-oxide or 9,10-dihydro-9-oxa-10-phosphorylphenanthrene-10-oxide, abbreviated as DOPO(C.A. RN 35948-25-5). Such compound is commercially available from Sanko Co, Ltd. under the trade name Sanko-HCA.
Two different structural formulae may be assigned to DOPO and its hydrolysis product:
Suitable derivatives of oxaphosphorinoxide are 9,10-dihydro-9-oxa-10-phosphorylphenanthrene-10-oxide (DOPO), salts of DOPO, such as the zinc salts
A particularly preferred embodiment of the invention relates to a composition, which comprises
According to a preferred embodiment, the weight ratio of components a):b) is in the range from 10.0:1.0 to 1.0:10.0, preferably 5.0:1.0 to 1.0:5.0.
Component c)
In a polyfunctional epoxide compound at least two epoxy groups of the partial formula
are present, which are attached directly to carbon, oxygen, nitrogen or sulphur atoms, and wherein q represents zero, R1 and R3 both represent hydrogen and R2 represents hydrogen or methyl; or wherein q represents zero or 1, R1 and R3 together form the —CH2—CH2— or —CH2—CH2—CH2— groups and R2 represents hydrogen.
Examples of polyfunctional epoxide compounds are:
Epoxy compounds having a radical of the formula A, in which R1 and R3 together are —CH2—CH2— and n is 0 are bis(2,3-epoxycyclopentyl)ether, 2,3-epoxycyclopentyl glycidyl ether or 1,2-bis(2,3-epoxycyclopentyloxy) ethane. An example of an epoxy resin having a radical of the formula A in which R1 and R3 together are —CH2—CH2— and n is 1 is (3,4-epoxy-6-methylcyclohexyl)methyl 3′,4′-epoxy-6′-methylcyclohexanecarboxylate.
Polyfunctional epoxide compounds are known. Many of them are commercially available from Huntsman Advanced Materials (brand name Araldite®). Examples of suitable polyfunctional epoxides are:
If desired, a mixture of epoxy compounds of different structure can also be employed.
Suitable polyfunctional epoxide compounds preferably comprise at least two groups of the formula
Particular preference as component c) is given to the following compounds of types and/or mixtures thereof:
Wherein X1, X2 and X3 are cyclohexylene, phenylene or naphthylene which can be unsubstituted or substituted and X1 is additionally an unsubstituted or substituted radical of the partial formula
and X2 is additionally an unsubstituted or substituted radical of the partial formula
Suitable substituents for the abovementioned radicals are —O—, —S—, —C(═O)—, —C(═O)—O—, —S(═O)═, —S(O2)—, —C(CF3)2—, alkyl, alkylene, aryl, arylene, alkoxy, aryloxy or halogen. Identical or different substituents may be present two or more times, whereas the substituents themselves may likewise be further substituted.
An example of a suitable alkyl radical is a C1-C18alkyl radical, such as methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl, and their branched isomers.
Possible alkylene and alkoxy radicals can be derived formally from the above-mentioned alkyl radicals by removing a further hydrogen atom or, respectively, by adding an oxygen atom.
Examples of suitable aryl radicals are those having 6-20 carbon atoms, such as phenylene, biphenylene or naphthylene.
Possible arylene and aryloxy radicals can be derived formally from the abovementioned aryl radicals by removing a further hydrogen atom or, respectively, by adding an oxygen atom.
Preference is given to radicals of the following formulae:
In which
Y1 is a direct bond or the groups —O—, —S— or —C(═O)O—;
Y2 is a direct bond or the groups —SO2—, —CO—, —S—, —SO—, CH2—, —C(CH3)2— or —C(CF3)2—;
And n is 1-10.
The aromatic rings are unsubstituted or substituted one or more times by alkyl, aryl, alkoxy, aryloxy or halogen, as described in more detail above.
Particular preference is given to the following compounds:
Component d)
According to a preferred embodiment, a hardener component is present in the composition. Suitable hardener compound is any of the known hardeners for epoxy resins. The amine and anhydride hardeners are particularly preferred, such as polyamines, e.g. ethylenediamine, diethylenetriamine, triethylenetriamine, hexamethylenediamine, methanediamine, N-aminoethyl piperazine, diaminodiphenylmethane [DDM], isophoronediamine [IPD], diaminodiphenylsulphone [DDS], 4,4′-methylenedianiline [MDA], or m-phenylenediamine [MPDA]), polyamides, alkyl/alkenyl imidazoles, dicyandiamide [DICY], 1,6-hexamethylene-bis-cyanoguanidine, or acid anhydrides, e.g. dodecenylsuccinic acid anhydride, hexahydrophthalic acid anhydride, tetrahydrophthalic acid anhydride, phthalic acid anhydride, pyromellitic acid anhydride), and derivatives thereof.
A preferred embodiment of the invention relates to a composition, which comprises as cornponent d1) a hardener compound that contains at least two amino groups, such as dicyanodiamide.
The invention furthermore relates to a process for the production of an epoxy resin composition having flame retardant properties which comprises mixing at least one polyfunctional epoxide according to the definition of component c), effective amounts of at least one salt of a phosphinic acid (I) or (II) and of 6H-Dibenz[c,e][1,2]oxaphosphorin-6-oxide (III) or a derivative thereof, a hardener d1), optionally in the presence of a suitable accelerator such as methyl imidazole, and optionally additional flame retardants such as inorganic flame retardants or melamine polyphosphate.
The process is carried out in a known manner by analogous methods, such as the ones described in U.S. Pat. No. 5,084,546.
Additional Components
According to an alternative embodiment, components a), b), c) and the optional component d) are present in a polymer substrate. The term polymer substrate comprises within its scope thermoplastic polymers or thermosets. A list of suitable synthetic polymers is given below:
The carbonate source may be a carbonyl halide, a carbonate ester or a haloformate. Suitable carbonate halides are phosgene or carbonylbromide. Suitable carbonate esters are dialkylcarbonates, such as dimethyl- or diethylcarbonate, diphenyl carbonate, phenyl-alkylphenylcarbonate, such as phenyl-tolylcarbonate, dialkylcarbonates, such as dimethyl- or diethylcarbonate, di-(halophenyl)carbonates, such as di-(chlorophenyl)carbonate, di-(bromophenyl)carbonate, di-(trichlorophenyl)carbonate or di-(trichlorophenyl)carbonate, di-(alkylphenyl)carbonates, such as di-tolylcarbonate, naphthylcarbonate, dichloronaphthylcarbonate and others.
The polymer substrate mentioned above, which comprises polycarbonates or polycarbonate blends, is a polycarbonate-copolymer, wherein isophthalate/terephthalate-resorcinol segments are present. Such polycarbonates are commercially available, e.g. Lexan® SLX (General Electrics Co. USA). Other polymeric substrates of component b) may additionally contain in the form as admixtures or as copolymers a wide variety of synthetic polymers including polyolefins, polystyrenes, polyesters, polyethers, polyamides, poly(meth)acrylates, thermoplastic polyurethanes, polysulphones, polyacetals and PVC, including suitable compatibilizing agents. For example, the polymer substrate may additionally contain thermoplastic polymers selected from the group of resins consisting of polyolefins, thermoplastic polyurethanes, styrene polymers and copolymers thereof. Specific embodiments include polypropylene (PP), polyethylene (PE), polyamide (PA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), glycol-modified polycyclohexylenemethylene terephthalate (PCTG), polysuiphone (PSU), polymethylmethacrylate (PMMA), thermoplastic polyurethane (TPU), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylic ester (ASA), acrylonitrileethylene-propylene-styrene (AES), styrene-maleic anhydride (SMA) or high impact polystyrene (HIPS).
The instant invention further pertains to a composition, which comprises, in addition to the components a), b), c) and the optional component d), as defined above, further additives selected from the group consisting of so-called anti-dripping agents, polymer stabilizers and additional flame retardants, such as phosphorus containing flame retardants, nitrogen containing flame retardants, halogenated flame-retardants and inorganic flame retardants.
According to a preferred embodiment the invention relates to a composition, which additionally comprises further additives selected from the group consisting of polymer stabilizers and additional flame retardants.
According to another embodiment, the invention relates to a composition which additionally comprises as additional component so-called anti-dripping agents.
These anti-dripping agents reduce the melt flow of the thermoplastic polymer and inhibit the formation of drops at high temperatures. Various references, such as U.S. Pat. No. 4,263,201, describe the addition of anti-dripping agents to flame retardant compositions.
Suitable additives that inhibit the formation of drops at high temperatures include glass fibers, polytetrafluoroethylene (PTFE), high temperature elastomers, carbon fibers, glass spheres and the like.
The addition of polysiloxanes of different structures as anti-dripping agents has been proposed in various references; cf. U.S. Pat. No. 6,660,787, 6,727,302 or 6,730,720.
Stabilizers are preferably halogen-free and selected from nitroxyl stabilizers, nitrone stabilizers, amine oxide stabilizers, benzofuranone stabilizers, phosphite and phosphonite stabilizers, quinone methide stabilizers and monoacrylate esters of 2,2′-alkylidenebisphenol stabilizers.
According to a preferred embodiment of the invention, the composition comprises an additional flame retardant component, such as phosphorus or nitrogen containing flame retardants or inorganic flame retardants. Such additional flame retardants are known components, items of commerce or can be obtained by known methods.
Representative phosphorus containing flame retardants, in addition to the ones defined above with regard to components a) and b), are for example:
Tetraphenyl resorcinol diphosphite (Fyrolflex® RDP, Akzo Nobel), tetrakis(hydroxymethyl)phosphonium sulphide, triphenyl phosphate, diethyl-N,N-bis(2-hydroxyethyl)-aminomethyl phosphonate, hydroxyalkyl esters of phosphorus acids, ammonium polyphosphate (APP) or (Hostaflam® AP750), resorcinol diphosphate oligomer (RDP), phosphazene flame retardants and ethylenediamine diphosphate (EDAP).
Nitrogen containing flame retardants are, for example, isocyanurate flame retardants, such as polyisocyanurate, esters of isocyanuric acid or isocyanurates. Representative examples are hydroxyalkyl isocyanurates, such as tris-(2-hydroxyethyl)isocyanurate, tris(hydroxymethyl)isocyanurate, tris(3-hydroxy-n-proyl)isocyanurate or triglycidyl isocyanurate.
Nitrogen containing flam retardants include melamine-based flame retardants. Representative examples are: melamine cyanurate, melamine borate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, melamine ammonium polyphosphate, melamine ammonium pyrophosphate, dimelamine phosphate, dimelamine pyrophosphate.
Further examples are: benzoguanamine, tris(hydroxyethyl) isocyanurate, allantoin, glycoluril, urea cyanurate, ammonium polyphosphate, a condensation product of melamine from the series melem, melam, melon and/or a higher condensed compound or a reaction product of melamine with phosphoric acid or a mixture thereof.
Representative inorganic flame retardants include, for example, aluminium trihydroxide (ATH), boehmite (AlOOH), magnesium dihydroxide (MDH), zinc borates, CaCO3, organically modified layered silicates, organically modified layered double hydroxides, and mixtures thereof.
Representative Organohalogen flame-retardants are, for example:
Polybrominated diphenyl oxide (DE-60F, Great Lakes Corp.), decabromodiphenyl oxide (DBDPO; Saytex® 102E), tris[3-bromo-2,2-bis(bromomethyl)propyl]phosphate (PB 370®, FMC Corp.), tris(2,3-dibromopropyl)phosphate, tris(2,3-dichloropropyl)phosphate, chlorendic acid, tetrachlorophthalic acid, tetrabromophthalic acid, poly-β-chloroethyl triphosphonate mixture, tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (PE68), brominated epoxy resin, ethylene-bis(tetrabromophthalimide) (Saytex® BT-93), bis(hexachlorocyclopentadieno)cyclooctane (Declorane Plus®), chlorinated paraffins, octabromodiphenyl ether, hexachlorocyclopentadiene derivatives, 1,2-bis(tribromophenoxy)ethane (FF680), tetrabromobisphenol A (Saytex® RB100), ethylene bis-(dibromonorbornanedicarboximide) (Saytex® BN-451), bis-(hexachlorocycloentadeno)cyclooctane, PTFE, tris(2,3-dibromopropyl) isocyanurate, and ethylene-bis-tetrabromophthalimide.
The halogenated flame retardants mentioned above are routinely combined with an inorganic oxide synergist. Most common for this use are zinc or antimony oxides, e.g. Sb2O3 or Sb2O5. Boron compounds are suitable, too.
The above-mentioned additional flame retardants are advantageously contained in the composition of the invention in an amount from about 0.5% to about 60.0% by weight of the organic polymer substrate; for instance about 1.0% to about 40.0%; for example about 5.0% to about 35.0% by weight of the polymer or based on the total weight of the composition.
According to a further embodiment, the composition according to the invention may additionally contain one or more conventional additives, such as the ones selected from pigments, dyes, plasticizers, antioxidants, thixotropic agents, levelling assistants, basic co-stabilizers, metal passivation agents, metal oxides, organophosphorus compounds, further light stabilizers and mixtures thereof, especially pigments, phenolic antioxidants, calcium stearate, zinc stearate, UV absorbers of the 2-hydroxy-benzophenone, 2-(2′-hydroxyphenyl)benzotriazole and/or 2-(2-hydroxyphenyl)-1,3,5-triazine groups.
The incorporation of the components defined above into the polymer component is carried out by known methods such as dry blending in the form of a powder, or wet mixing in the form of solutions, dispersions or suspensions for example in an inert solvent, water or oil. The components a), b) and c) and optional further additives may be incorporated, for example, before or after molding or also by applying the dissolved or dispersed additive or additive mixture to the polymer material, with or without subsequent evaporation of the solvent or the suspension/dispersion agent. They may be added directly into the processing apparatus (e.g. extruders, internal mixers, etc.), e.g. as a dry mixture or powder, or as a solution or dispersion or suspension or melt.
The addition of the additive components to the polymer substrate can be carried out in customary mixing machines in which the polymer is melted and mixed with the additives. Suitable machines are known to those skilled in the art. They are predominantly mixers, kneaders and extruders.
The process is preferably carried out in an extruder by introducing the additive during processing.
Particularly preferred processing machines are single-screw extruders, contra-rotating and co-rotating twin-screw extruders, planetary-gear extruders, ring extruders or co-kneaders. It is also possible to use processing machines provided with at least one gas removal cornpartment to which a vacuum can be applied.
Suitable extruders and kneaders are described, for example, in Handbuch der Kunststoffextrusion, Vol. 1 Grundlagen, Editors F. Hensen, W. Knappe, H. Potente, 1989, pp. 3-7, ISBN:3-446-14339-4 (Vol. 2 Extrusionsanlagen 1986, ISBN 3-446-14329-7).
For example, the screw length is 1-60 screw diameters, preferably 35-48 screw diameters. The rotational speed of the screw is preferably 10-600 rotations per minute (rpm), preferably 25-300 rpm.
The maximum throughput is dependent on the screw diameter, the rotational speed and the driving force. The process of the present invention can also be carried out at a level lower than maximum throughput by varying the parameters mentioned or employing weighing machines delivering dosage amounts.
If a plurality of components is added, these can be premixed or added individually.
The additive components a), b) and c) and optional further additives can also be sprayed onto the polymer substrate. The additive mixture dilutes other additives, for example the conventional additives indicated above, or their melts so that they can be sprayed also together with these additives onto the polymer substrate. Addition by spraying during the deactivation of the polymerisation catalysts is particularly advantageous. In this case, the steam evolved may be used for deactivation of the catalyst. In the case of spherically polymerised polyolefins it may, for example, be advantageous to apply the additives of the invention, optionally together with other additives, by spraying.
The additive components a), b) and c) and optional further additives can also be added to the polymer in the form of a master batch (‘concentrate”) which contains the components in a concentration of, for example, about 1.0% to about 40.0% and preferably 2.0% to about 20.0% by weight incorporated in a polymer. The polymer is not necessarily of identical structure than the polymer where the additives are added finally. In such operations, the polymer can be used in the form of powder, granules, solutions, and suspensions or in the form of lattices. The incorporation can take place prior to or during the shaping operation.
The components a) and b) are admixed to the polyfunctional epoxide compound c) in concentrations of 0.05-30.0 wt. %, preferably 0.1-20.0 wt. % for component a) and 0.5-40.0 wt. %, preferably 1.0-25 wt. % for component b).
The preferred ratio of components a):b) is in the range 10:1-1:10, preferably 5:1-1:5.
A further embodiment of the invention relates to a process for imparting flame retardancy to a hardened polyfunctional epoxide substrate, which process comprises adding a) a salt of a phosphinic acid (I) or (II), as defined above, and b) 6H-Dibenz[c,e][1,2]oxaphosphorin-6-oxide (III) and a hardener compound to the polyfunctional epoxide compound.
The following examples illustrate the invention but are not meant to limit the scope thereof in any manner:
Components and Reagents Used:
o-Cresol NOVOLAC epoxy resin: Araldite® ECN 1280, Huntsman Advanced Materials, Basel, Switzerland;
Hardener: Dicyanodiamide (DICY), accelerator: methylimidazole, both from Aldrich, Germany;
Solvents: Methoxy-2-propanol and dimethylformamide, Merck Eurolab, Germany;
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO): Ukanol®GKF, Schill & Seilacher AG, Germany;
Al-hypophosphite (Al-phosphinate): Anana Drug & Chemicals India;
Melamine polyphosphate: Melapur® 200, Ciba AG Basel Switzerland;
Glass cloth: Type 7628, P-D Intergals Technologies AG, Germany.
Test Methods to Assess Flame Retardancv
UL 94 test for “Flammability of Plastic Materials for Parts in Devices and Appliances”, 5th edition, Oct. 29, 1996. Ratings according to the UL 94 V test are compiled in the following table (time periods are indicated for one specimen):
A resin formulation is prepared using different amounts of Araldite® ECN 1280 resin. 9.2 parts of DICY (solution in solvent mixture of DMF and methoxy-2-propanol), 0.3 parts of methylimidazole accelerator and 60 parts methoxy-2-propanol are added to the resin composition, followed by the above-mentioned flame retardants.
After complete mixing of the above mixture in a glass jar at 90° C. and continuous stirring for a period of 30 min, flame retardant components, Al-hypophosphite or Al-hypophosphite and DOPO or Al-hypophosphite, DOPO and MELAPUR 200 are added and mixed thoroughly with the above mentioned mixture until a homogeneous composition is obtained.
The composition is coated onto a piece of glass cloth and heated to 170° C. for about 1-3 min in a forced draft oven. The time in the forced draft oven is varied slightly from sample to sample in order to control resin flow of the final laminate. The fibre material, now in the shape of a non-tacky prepreg, is cut into 7 strips (˜180×180 mm) which are stacked upon each other in a distance holder, to assure the manufacture of laminates with uniform thickness of 1.5 mm. The strips are covered with two Teflon® plates of 1 mm thickness on the upper and the lower side of the prepreg stack. The stack is placed on a hot press, and the stacked prepregs are subjected to elevated temperature and pressure according to the following general schedule:
The resulting laminate is then removed from the press, cooled to ambient temperature, and separated from the distance holder and Teflon® plates. The laminate is cut into pieces of ˜150×150 mm by cutting off the edges with varying amounts of resin, weighed, its thickness measured, and its percent resin content determined. The laminate is cut into five strips (125×13.0 mm) which are conditioned for 24 h at 23° C. and 50% relative humidity and subsequently tested in the previously mentioned UL-94 flammability test. The data obtained in this test are presented in the Table.
The data presented in the Table demonstrate that the claimed resin compositions exhibit improved flame retardant properties as compared with resin compositions containing a single flame retardant component. Resin compositions containing only 9,10-dihydroxo-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and melamine polyphosphate (Melapur® 200) retain their flame retardant performance (UL94 V-0 rating) as compared with resin compositions containing DOPO alone at the same total loading. Up to 50% of DOPO can be replaced e.g. by Melapur® 200 retaining the desired UL94 V-0 classification. Best performance in terms of shortest total burning times exhibit claimed resin compositions containing all three flame retardant components in a synergistic combination. Furthermore, the claimed flame retardant epoxy resin compositions result in laminates with excellent surface characteristics and reduced delamination tendency.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08172973.3 | Dec 2008 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13141097 | Aug 2011 | US |
| Child | 14249895 | US |
