CA1162794A - Process for stabilizing by encapsulation red phosphorus to be used as flame retardant of polymeric materials and product so obtained - Google Patents
Process for stabilizing by encapsulation red phosphorus to be used as flame retardant of polymeric materials and product so obtainedInfo
- Publication number
- CA1162794A CA1162794A CA000387399A CA387399A CA1162794A CA 1162794 A CA1162794 A CA 1162794A CA 000387399 A CA000387399 A CA 000387399A CA 387399 A CA387399 A CA 387399A CA 1162794 A CA1162794 A CA 1162794A
- Authority
- CA
- Canada
- Prior art keywords
- red phosphorus
- phosphorus powder
- melamine
- melamine resin
- encapsulated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/003—Phosphorus
- C01B25/006—Stabilisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/10—Encapsulated ingredients
Abstract
ABSTRACT OF THE DISCLOSURE:
The invention relates to a process for stabilizing red phosphorus powder, in its various allotropic forms, by encapsulating -the particles of said powder in a melamine resin for its safe use as a flame retardant of polymeric materials, which comprises the steps of: (a) preparing an aqueous solution of a melamine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, triethanolamine, and an aliphatic monohydroxyl alcohol having up to 5 carbon atoms, in the respective percent by weight ratios: 25.27% to 21.62%, 36.04% to' 30.85% 29.87% to 25.57% and 8.82% to 21.96%, and adjusting the pH thereof with the mineral acid, (b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein; (c) heating said hydrodispersion, under stirring at 80° to 100°C to encapsulate individual particles of the red phosphorus powder by precipitating onto said indivi-dual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin; and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80° to 130°C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric materials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 to 30% by weight of the red phosphorus powder.
The invention relates to a process for stabilizing red phosphorus powder, in its various allotropic forms, by encapsulating -the particles of said powder in a melamine resin for its safe use as a flame retardant of polymeric materials, which comprises the steps of: (a) preparing an aqueous solution of a melamine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, triethanolamine, and an aliphatic monohydroxyl alcohol having up to 5 carbon atoms, in the respective percent by weight ratios: 25.27% to 21.62%, 36.04% to' 30.85% 29.87% to 25.57% and 8.82% to 21.96%, and adjusting the pH thereof with the mineral acid, (b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein; (c) heating said hydrodispersion, under stirring at 80° to 100°C to encapsulate individual particles of the red phosphorus powder by precipitating onto said indivi-dual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin; and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80° to 130°C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric materials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 to 30% by weight of the red phosphorus powder.
Description
~L~7~4 "Process for stabilizing by encapsulation red phosphor~s .
to be used a.s flame retardant of polymeric materials and product so obtained"
The presen-t invention relates to a process for s-tabiliz-ing phosphorus, in particular red phosphorus in powder -the term "red phosphorus" being intended to designate red phosphorus in any of its allotropic forms - by encap-sulation thereof in a mélaminic resin, and to the corres-ponding product, suited to be used as flame retardant ofpolymeric materials.
3ackground of the invention ... ...
The use of red phosphorus as flame reta.rdant of polymer-ic materials is widely described, also in patent liter-ature, according to which red phosphorus in powder is em-ployed in percentages depending on the nature of -the po-lymeric material., generally in admixture with coadjuvant substances.
It is also known that red phosphorus, in the.open air, reacts with oxygen and water vapour, so evolving, besides oxygenated acids, also phosphine, which is known to be very toxic, what results in a serious drawback for the above-mentioned use of red phosphorus, both,and chiefly, during the incorporation of same into the polymeric ma-terials, as the relevant operative conditions, particul-a.rly the molding step, magnify the aforesaid undesired phenomenon to such extent as to prevent said technical use of red phosphorus, and during the s-torage and hand-ling which precede such incorporation.
Many processes have been described in the past, which a.imed at stabilizing red phosphorus in powder against iZ7~
phosphine Eorming by mixing or e~capsulation of this powder with various materials, such as, for example, potassium silicate, silver ni-trate, aluminium hydroxide, copper sulphate with copper ch~orIde, condensates of bisphenol A with cyanuric chloride, magnesium or aluminium salts of ethylenediamine-tetra-acetic acid, chlorinated waxes, liquid chlorina-ted paraffins, melamine, melaminic resins, phenol-formaldehyde resins, epoxy resins, poly-acrylonitrile etc.; -the known processes, however, exhibit the drawback of providing an insufficent stabiliz.a-tion -to phosphine forming.
S MARY OF THE INVENTION
It is an object of the present invention to provide a process for obtaining red phosphorus stabilized by encapsulation with a continuous and compact layer, such as to prevent the aforesaid phenomena and drawbacks, thus allowing a technical use free from any adverse -technologi-cal and environmental effects.
It is another object of the presen-t invention to carry out the aforesaid encapsulation process in an aqueous dispersion, without usiny organic solvents, in order to avoid the additional costs and process difficulties con-nected therewith.
These and still other objects, that will more clearly appear to a technician skilled in the art, are achieved, according to this invention, with a process for stabilizingred phosphorus powder, in its various allotropic forms, by encapsulating the particles of said powder in a melamine resin for its safe use as a flame retardant of polymeric materials, which comprises the steps of:
(a) preparing an aqueous solution of a melamine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, trie-thanolamine, and an aliphatic monohydroxyl alcohol. having up to 5 carbon atoms, in the respective percent by weight ratios.:
25.27% to 21.62~, 36.04% to30.85%, 29.87% -to 25.57% and
to be used a.s flame retardant of polymeric materials and product so obtained"
The presen-t invention relates to a process for s-tabiliz-ing phosphorus, in particular red phosphorus in powder -the term "red phosphorus" being intended to designate red phosphorus in any of its allotropic forms - by encap-sulation thereof in a mélaminic resin, and to the corres-ponding product, suited to be used as flame retardant ofpolymeric materials.
3ackground of the invention ... ...
The use of red phosphorus as flame reta.rdant of polymer-ic materials is widely described, also in patent liter-ature, according to which red phosphorus in powder is em-ployed in percentages depending on the nature of -the po-lymeric material., generally in admixture with coadjuvant substances.
It is also known that red phosphorus, in the.open air, reacts with oxygen and water vapour, so evolving, besides oxygenated acids, also phosphine, which is known to be very toxic, what results in a serious drawback for the above-mentioned use of red phosphorus, both,and chiefly, during the incorporation of same into the polymeric ma-terials, as the relevant operative conditions, particul-a.rly the molding step, magnify the aforesaid undesired phenomenon to such extent as to prevent said technical use of red phosphorus, and during the s-torage and hand-ling which precede such incorporation.
Many processes have been described in the past, which a.imed at stabilizing red phosphorus in powder against iZ7~
phosphine Eorming by mixing or e~capsulation of this powder with various materials, such as, for example, potassium silicate, silver ni-trate, aluminium hydroxide, copper sulphate with copper ch~orIde, condensates of bisphenol A with cyanuric chloride, magnesium or aluminium salts of ethylenediamine-tetra-acetic acid, chlorinated waxes, liquid chlorina-ted paraffins, melamine, melaminic resins, phenol-formaldehyde resins, epoxy resins, poly-acrylonitrile etc.; -the known processes, however, exhibit the drawback of providing an insufficent stabiliz.a-tion -to phosphine forming.
S MARY OF THE INVENTION
It is an object of the present invention to provide a process for obtaining red phosphorus stabilized by encapsulation with a continuous and compact layer, such as to prevent the aforesaid phenomena and drawbacks, thus allowing a technical use free from any adverse -technologi-cal and environmental effects.
It is another object of the presen-t invention to carry out the aforesaid encapsulation process in an aqueous dispersion, without usiny organic solvents, in order to avoid the additional costs and process difficulties con-nected therewith.
These and still other objects, that will more clearly appear to a technician skilled in the art, are achieved, according to this invention, with a process for stabilizingred phosphorus powder, in its various allotropic forms, by encapsulating the particles of said powder in a melamine resin for its safe use as a flame retardant of polymeric materials, which comprises the steps of:
(a) preparing an aqueous solution of a melamine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, trie-thanolamine, and an aliphatic monohydroxyl alcohol. having up to 5 carbon atoms, in the respective percent by weight ratios.:
25.27% to 21.62~, 36.04% to30.85%, 29.87% -to 25.57% and
2 -; ~
'7~1~
8.82% to 21.96~, and adjustiny the pH thereof with the mineral acid:
(b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein;
(c) heating said hydrodispersion, under stirring, at 80 to 100C to encapsulate individual particles of the red phosphorus powder by precipitating onto said individual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin;
and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80 to 130C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric ma-terials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 to 30~ by weight of the red phosphorus powder.
The percentage of resin useful to stabilize red phosphorus in powder may vary over a wide range, from 0.1 to 30%, preferably from 1 to 5~, in respect of encap-sulated phosphorus.
The most advantageous particle size of red phosphorus is below 40 microns, bu* it is not critical, a particle size even above 100 microns being suitable too.
The melaminic resin utilized according to this inven-tion is a condensate or syrup prepared from melamine, form~ldehyde, a monohydroxyl alcohol and triethanolamine cationized with a mineral acid and thoroughly soluble in water prior to cross-linking, wherein alcohol is the component that chemically modifies the condensate (as revealed by infrared spectroscopic analysis), by differentiating it from the known cationized melaminic , .
, z~
resins such as, for example, the ones described in U.S.
pa-ten.t 3,721,651 of March 20, 1973, and which imparts. a low ~i.scosity to said con.densate, what is particularly useful for practising the process object of this invention.
In said condensate, the cationizing mineral acid is preferably hydrochloric acid, while the monohydroxyl alcohol, selected from amongst the aliphatic alcohols having a number of carbon atoms lower than 5, is preferably me-thanol.
The melamine resin and the process for encapsula-ting red _ -~ - 3a ~
-7~
phosphorus in powder with the resin itself 9 according to the presen-t invention are also substantially different from what is disclosed and formsthe object of German pub lished patent application No. 2~45~35 (Germ. April 20~
5 197~) ~ as regards both the components and their respec-tive composition ratios in the cited resin (particularly the for maldehyde/melamine molar composition ratios)and the various steps of the encapsulation process (carried out in the abs-ence of organic solvents), which are determinant for the 10 high stability characteristics of encapsulated red phos-phorus in powder to phosphine forming.
Description of the preferred embodiment A preferred, although not unique,embodiment of.the present invention consists in preparing a hydrodispersion of red 15 phosphorus in powder having a. particle size below 40 microns, in an aqueous solution of a melamine condensate containing 25~27~o melamine, 36~04~ formaldehyde, 8~82% methanol and 29~87% triethanolamine, cationized with hydrochloric acid, in heating said dispersion, under stirring, at about 100C, 20 so obtaining the encapsulation of the red phosphorus in-dividual particles, due to slow precipitation thereonto,-in a continuous and compact layer, of said condensa.te in the form of a partially cross-linked insoluble melaminic .. resin, the cross-linking thereof completes during a succes-25 sive dehydration step by drying in an inert gas fiow, or preferably under vacuum, a.t about 100C unti~ formaldehyde does no longer form, so obtaining a powder of encapsulated red phosphorus.
More particular, the abovesaid preferred embodiment of 30 the invention comprises the following steps :
a) preparing -the melamine condensate : in a first step, ~ .
me'thanol, triethanolamine, formaldehyde (the last subs-tance in an aqueous solution a.t approximate 45% calcul-ated on dry basis) are reacted for about 2 hours at ap-prox. 85C in per centratios, referred to the dry subs-tance, respectively of 8.82~, 29087% and 36.04%, the re-maining 25.275~ being the melamine which is to be added in a second step, at the end of the a.foresaid reaction, in order to cause the melamine condensate to form by.
hea.ting the aforesaid composition at about 90C for ap-prox. 6 hours - the starting pH value of 9. 5 - 9.8 being adjusted to the value of 7.5 - 7.8 - til:L a viscosity of 420-470 centipoises at 20c is attained, whereupon, af-ter having adjusted the pEI to a value of 7-7 . 6, it is 'diluted with wa-ter, so obtaining a solution'at about 38%
of dry substance and with a viscosity of 40-50 centi-poises at 20C, pH a.djustments~are effected by means of hydrochloric'acid in an aqueous solution at 18%, thus ca.tionizing the melamine condensate. . --b) Encapsula.ting red phosphorus powder~
a hydrodispersion of micronized red phosphorus powder having a density of 1. 38 -1 . 58 is additioned with a desir-ed amount of'the aqueous solution at 38% of cationized melamine condensate, prepared as per point a.); the so ob-tained phosphorus dispersion in the melamine condensate solution is heated, under stirring, for about 1 hour at approx. 100C, keeping substantially unaltered-- by means of a condenser - the reaction mixture volume:
under such condi-tions the melamine condensate precipitat-es slowly and uniformly (evolving formaldehyde) in the 30 form of a resin partially cross-linked, at first in the ' liquid-viscous, then in the solid state7 around the red phosphorus particles 9 SO encapsulating them. Cross-link-ing is then completed during dehydration by dryi~g of the-product, preferably in a thin layer, a.t about 100C
and in an inert ga.s flow or preferably under vacuum, 5 -till formaldehyde does no longerevolve~At the end a red phosphorus powder is obtained, which is free-flowing, stabilized to phosphine forming and ea.sily dispersible intO the polymeric ma.terials, for example by means of pro-cesses ba.sed on plastic mass melting, or by incorporation into hydrodispersions a~a aqueous polymaric emulsions, which are then utilized in film-forming processes (for .
example paints, glues, etc.), by incorporation into elas-tomers, by dispersion into polymeric product solutions, by dispersion into pre-polymeric liquid systems with one or more componen-ts and the like.
- A variant of the process object of the present invention - consists in adding to the red phosphorus powder hydrodis-persion, already encapsulated with cationized and partial-.
ly cross-linked melaminic resin, be~ore subjecting said dispersion to dehydration with simultaneous completion of-~
the resin cross-linking, a.vehicle, preferably a.water--soluble vehicle, in which, at the end of the process after dehydration, the stabilized red pshosphorus powder remains dispersed, so obtaining a solid composition,that e.g. can be flaked, or a.liquid composition, both compos-itions having a high red phosphorus content, for example of 70~, and being more advantageously or easily employ-able, under safe conditions, as anti-flame agents in the successive processes of additivation to the polymeric ma-terials. Said vehicle, to be selected from amongst -the ones which are consistent with the polymeric material to be used, may be for example -caprolactam or a paraffin wax - in such case the final composition is solid and in the form of flakes - or a. polyol or a paraffin oi.l, pre-ferably a chlorinated one - in such case the final com-5 position is liquid.
Theprocess object of the present invention and the corres-pondingproduct will be better comprehended on the ba.sis ofthe following examples, which are given for merely il-lusirative but not limitative purposes.
Example 1 .
640 g of an a.queous solution containing 45i~o of formalde-hyde (9.6 moles), 70.5 g (2~2 moles) of me-thanol, 238~78 g (1~6 moles) of trie-thanolamine were introduced into a con-15 ven-tional rea.ctor, known in the art, equipped with elec-trical heating, a reflux condenser with a vacuum inta.ke and a magnetic stirrer, after having started both stirrer and condenser. The mixture so obtained, having a pH = 9~8 was brought to 85C and maintained at such tempera.ture for 20 2 hours, After cooling to 50C, 201~8 g ~1~6 moles).of~
melamine were added (the mixture now consisted for 36.04%:..
of formaldehyde, for 8~82% of methanol, for 29~87% of triethanolamine and for 25~27% of melamine?. The pH was adjusted to a.value of 7~6 by addition of 48 mi of hydro-25 chloric acid at 18% in an aqueous solution, and the mix-ture temperature-was raised to 90C and kept such for 6 hours, so obtaining a melamine condensate solution having a viscosity of 450 centipoises at 20Co At the end of this heating period said condensa.te solution was s-tabiliz-ed by àddition of 390 ml of wa.ter and by a.djusting the pHto a value of 7.5by adding 80 ml hyd~ochloric acid at 18~o in an aqueous solution, finally obtaining a solution of cationi~ed melamine condensate at 38.3% of dry substance having a viscosity of 40 centipoises at 20C. The above--cited pH adjustments represent the cationizing steps of the melamine condensate.
27.6 ml of the a.bove-obtained solution of cationized me-lamine condensate were drawn andl~jintroduced in-to a reactor (equipped with a mechanical stirrer, a condenser and a heating jacket) along with 300 g of red phosphorus powder, having a particle size below 40 microns, in the form of an a.queous dispersion having a density of 1.38. At the conclusion of this operation the components were homogen-ized by stirring, thus obtaining a red phosphorus powder suspension in a. cationized melamine solu-tion condensa.te, which wa.s heated at 100C for 1 hour. During such heating time the condensate got insoluble (with formaldehyde evol-ution)and slowly and uniformly precipitated, in the form of.a partially cross-linked melaminic resin, a.t first in the liquid-viscous state then turning-lnto the solid ~
state, onto the particles' surfaces of the red phosphorus powder, which were thus encapsulated by a very adherent, continuous and compact layer of said resin; finallyg a water dispersion of red phosphorus encapsulated by me-laminic resin, having a slurry-like consistence was ob-tained. Said.dispersion was spread to form a thin layer 25 of 2-3 mm thickness in a -tray and wa.s put into an oven at 90C under va.cuum, at a residual pressure of approx.
30 mm ~g, till formaldehyde evolution was no longer observ ed. During such drying,bo~h dehydra.tion of said ~ispersion and completion of melaminic resin cross-linking occurred, and at the end a friable layer, easily convertible into a - , , -free-flowing product, of red phosphorus in powder encap-sulated with 4~0 of melaminic resin wa.s obtained; such powder proved to be stable to phosphine forming and was easily dispersible into the polymeric materials as self--extinguishing product.Said enca.psulated phosphorus powder . was exposed three mon~hs to the air and during such time the pra.ctical absence of phosphine (less than 0O3 ppm~
was checked by means of a detector apparatus of the type equipped with a little suction pump and a detecting phial, having a minimum sensitivi-ty to phosphine of 0.1 ppm (Dr~ger ~Iulti Ga.s Detector Mod. 21/31 ) ~
The melaminic resin obtained as explained hereinbefore wa.s subjected to infrared spectroscopic analysis; said analysls revealed an absorption band at 2810 cm 1 cor-responding to symmetrical stretching ~ OCH3 and a greatintensification of -the band at 1080 cm corresponding to ethereal stretching ~ COC, what clearly points out that .such resin was methylated due to the chemical action of methyl alcohol in the above-described reactions. -:
Example 2 Using the same apparatuses~ modalitiesland substa~nces~as in example 1, a red phosphorus powder encapsulated with . melaminic resin was prepared, with the only exception that the per cent composition of the starting components of the melaminic condensate were as follows : 34.66~ of for-maldehyde, 12~34% Of methanol, 28~72% of triethanolamine and 24 ~ 287~o of melamine.
Such condénsate exhibited a viscosity (after stabiliz--: ;.
ation) of 33 centipoises at 20C~ The encapsulated red phosphorus powder so obta1ned was endowed with properties .
... . .. . .
-~L~6Z~
like those of example 1.
- Example 3 Using the same apparatuses, modalities and substances a.s in example 1, a. red phosphorus powder encapsulated with melaminic resin was prepared, with the only variant that the per cent composition of the starting components of the melamine condensate were as follows : 30.85% of formalde-hyde, 21.9.~% of methano~, 25.57% of triethanolamine and 21.62% of melamine.
Said condensatè exhibi-ted a viscosity (after stabilization) of 23 centipoises at 20C. The encapsulated red phosphorus powder so obtained was endowed with properties like the ones of example 1.
~xample 4 - 15 Using the same apparatuses, modalities and substances as --in example 1,.with the only ~ariant of including in the melamine condensate composition 148 g of butanol instead .
of methanol, a-red phosphorus powder encapsulated wi-th melaminic resin was preparedj which exhibited substantial-ly the same characteristics as the one obtained in ex-ample 1, in particular as regards the stability to phos-phine forming.
Example 5 Using the same appa.ratuses, modalities and substances as - 25 described in example 1, a powder of red phosphorus encap-sulated with melaminic resin was prepared, with the ~a-.riants of using orthophosphoric acid in an aqueous sol-ution at 80% as cationizing mineral acid, and of effecting . dehydration~by drying in a nitrogen stream at 1~0C.
~he encapsulated red phosphorus powder had the sa~e char-: acteristics as the one obtained in example 1.
79~
Example 6 .-Using the same appara-tuses, modalities and substances as described in example 1, a composition consisting of ~ -caprolactam incorporating~ in a. dispersed manner, 70% of red phosphorus powder encapsulated with melaminic resin was prepared9 the variant brought to the process consist-ing in adding 128 g of-caprolactam to the hydrodispersion of red phosphorus powder at the end of the encapsulation wi-th the partially cross-linked melaminic resin, and in going on heating the reactor containing the mixture of-the aforesaid components for 2 hours at 100C, always keeping the reactor stirrer running and creating a vacuum ih the reactor. During such time-period the mixture de-hydrated and the resin completed its cross-linking, fin-ally providing a homogeneous dispersion of an encapsul- -.
a.ted red phosphorus powder in molten ~ -caprolactam.
Said moltén productwas poured in thin layer into trays- ~ ;
where it solidified hy cooling, whereupon the product was reduced to flakes which proved to be stable to phosphine~
forming and could be easily incorporated into polyamides ~
during hot extrusion thereof in extruder, in order to im- ;
part the desired self-extinguishing properties to them.
Example 7 -. ~ .
. Using the same apparatus a~d modalities as in-example 1, : 25 but employing, instea.d of ~ -caprolactam, the same amount o~ a polyol-polyether (obtained from ethylene ox-ide and propylene oxide with a hydroxylinumber of 56 and a.viscosity of 550 centipoises), a liquid composition consisting for 709 of red phosphorus powder encapsula.ted 30 with melaminic ~eisin, according to example 1, dispersed in said polyol was prepared~ In this case, at the end ' ., i of the dehydration step and cross-linking completion step of the melaminic resin, a liquid composi-tion ~as ob- ~
tained, which proved stable to phosphine forming and al-ready ready to be ea.sily incorporated into the compos-itions intended for the production of polyurethane resins al.so of the foamed type, in order to impart self-exting-uishing properties to them.
Example 8 In a conventional horizontal drum mixer known in the art, 25 kg of a homogeneous mixture consisting for 88% of poly-amide 6-6 in cylindrical 3x3 mm granules for general uses,and for 12% of the composition of red phosphorus dis-persed in -caprolactam obtained in example 6 were pre-pared. Said mixture was put into a single-screw ex-truder equipped with an electrical heating device, in which the.
mixture was homogenized in the molten state and came out -~
from the extruder head in the form of strands which, af-ter cooling in water and passing through a cutter, were reduced to cylindrical 3x3 mm granules from whichj~by`in-- .
jection molding, specimens `of 152.4 mm length, 12.7 mm~
width~- and 1.6 mm thickness were obta.ined, which were sub jected to the self-extinguishing test according to the ~
vertical flame method U~-94 (Underwriter ~aboratory Bul-letin 94) by vertically pla.cing the specimens being test-ed on a Bunsen flame for 10 seconds and then for further ~10 seconds after combusti~n extinguishing. The polyamide material additivated as explained hereinbefore may be classified, according to said U~-94 method, as a self-ex-- tinguishing substance of V-0 degree. During all the afore-said mixing , extruding and molding operations, the phos-p`ine forming, determined by means of the detector des-. , .
scribed in example 1, was always below 0.3 ppm.
- Example 9 25 kg of high density polyethylene (density = 0.955 ~
ml) in sperica granules (diameter = about 3 mm)g homo-geneously wetted with 120 ml of vaseline oil (density =
0.877) were introduced into the mixer of example 8;
then 2 kg of the encapsula.ted red phosphorus powder of example 1 with 4~ of melaminic resin were added and the whole was mixed for 30 minutes. At the end of such mix-ing, polyethylene granules homogeneously coated with en-capsulated red phosphorus powder were obta.ined, which were fed to an electrically hea.ted single-screw extruder having a hea.d temperature of about 200C, so obtaining strands which, after cooling in wa-ter and passing .15 through a cutter, were reduced to cylindrical 3x3 mm granules, from which, by injection molding, specimens were obtained havinga-length of 152.4 mm, a width of 12.7 mm and a thickness of 1.6 mm. After having been ;
` subjected to the UL-94 self-extinguishing~test descr1b-~
: 20 ed in example 8, they were classified of degree V~
the extinguishing time ranging from 6 to 10 seconds.
During all the above-mentioned mixing, ex-truding and molding operations, the phosphine formingg checked by . means of the detector described in example 1, was al-ways below 0O3 ppm.
Example 10 ~or comparative purposes, in order to prove the subs-tantial importance of methyl alcohol for the ch.~racter-istics of the melamine condensate9 of which it is a component, and the consequent influence o~ such char-a.cteristics on the encapsulation process object of the 7~
present invention, a cationized mel amine condensate was prepared (using the same apparatuses and modalities of ex-ample 1) by reacting 39053% of formaldehyde, 32.77~0 of tri-ethanolamine and 27.70% of melamine~ Said condensate,of 5 the same type as the one described in the already cited U.S.patent 3,721,651,ezhibited,after stabilization,a vis cosity of 260 cps at 20C,substa-ntially higher than the one of the corresponding condensate of example 1; during the successive red phosphorvs powder encapsulation step 10 (always according to example 1) it was noticed that the encapsulation process'occurred by insolubilization of the melalnine condensate directly in -the solid state, without passing through the liquid-viscous phase.
Furthermore, the infrared spectroscopic analysis oE'-the melaminic resin so obtained, did not show the absorption --band'~) OCH3 that was observed in the corresponding resin of example 1. From the foregoing, -particularly from ex-amples 1 and 10, it is evident that there is a correlation between the participation o`f -the alcohol in ~the~ compositlon-20 of the melamine condensate and the characteristics of the latter, such characteristics being, in their turn, advant-ageous for purposes of 'obtaining àn excellent encapsul-ation of the red phosphorus powder, according -to the pro-' cess of the present invention.
of course, modifications and variations, all falling with-in the scope of the inventive principle, may be brought to the invention as described hereinbefore, and the pro-cess and product details may be replaced by other tech-30 nically equivalent elements.
'7~1~
8.82% to 21.96~, and adjustiny the pH thereof with the mineral acid:
(b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein;
(c) heating said hydrodispersion, under stirring, at 80 to 100C to encapsulate individual particles of the red phosphorus powder by precipitating onto said individual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin;
and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80 to 130C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric ma-terials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 to 30~ by weight of the red phosphorus powder.
The percentage of resin useful to stabilize red phosphorus in powder may vary over a wide range, from 0.1 to 30%, preferably from 1 to 5~, in respect of encap-sulated phosphorus.
The most advantageous particle size of red phosphorus is below 40 microns, bu* it is not critical, a particle size even above 100 microns being suitable too.
The melaminic resin utilized according to this inven-tion is a condensate or syrup prepared from melamine, form~ldehyde, a monohydroxyl alcohol and triethanolamine cationized with a mineral acid and thoroughly soluble in water prior to cross-linking, wherein alcohol is the component that chemically modifies the condensate (as revealed by infrared spectroscopic analysis), by differentiating it from the known cationized melaminic , .
, z~
resins such as, for example, the ones described in U.S.
pa-ten.t 3,721,651 of March 20, 1973, and which imparts. a low ~i.scosity to said con.densate, what is particularly useful for practising the process object of this invention.
In said condensate, the cationizing mineral acid is preferably hydrochloric acid, while the monohydroxyl alcohol, selected from amongst the aliphatic alcohols having a number of carbon atoms lower than 5, is preferably me-thanol.
The melamine resin and the process for encapsula-ting red _ -~ - 3a ~
-7~
phosphorus in powder with the resin itself 9 according to the presen-t invention are also substantially different from what is disclosed and formsthe object of German pub lished patent application No. 2~45~35 (Germ. April 20~
5 197~) ~ as regards both the components and their respec-tive composition ratios in the cited resin (particularly the for maldehyde/melamine molar composition ratios)and the various steps of the encapsulation process (carried out in the abs-ence of organic solvents), which are determinant for the 10 high stability characteristics of encapsulated red phos-phorus in powder to phosphine forming.
Description of the preferred embodiment A preferred, although not unique,embodiment of.the present invention consists in preparing a hydrodispersion of red 15 phosphorus in powder having a. particle size below 40 microns, in an aqueous solution of a melamine condensate containing 25~27~o melamine, 36~04~ formaldehyde, 8~82% methanol and 29~87% triethanolamine, cationized with hydrochloric acid, in heating said dispersion, under stirring, at about 100C, 20 so obtaining the encapsulation of the red phosphorus in-dividual particles, due to slow precipitation thereonto,-in a continuous and compact layer, of said condensa.te in the form of a partially cross-linked insoluble melaminic .. resin, the cross-linking thereof completes during a succes-25 sive dehydration step by drying in an inert gas fiow, or preferably under vacuum, a.t about 100C unti~ formaldehyde does no longer form, so obtaining a powder of encapsulated red phosphorus.
More particular, the abovesaid preferred embodiment of 30 the invention comprises the following steps :
a) preparing -the melamine condensate : in a first step, ~ .
me'thanol, triethanolamine, formaldehyde (the last subs-tance in an aqueous solution a.t approximate 45% calcul-ated on dry basis) are reacted for about 2 hours at ap-prox. 85C in per centratios, referred to the dry subs-tance, respectively of 8.82~, 29087% and 36.04%, the re-maining 25.275~ being the melamine which is to be added in a second step, at the end of the a.foresaid reaction, in order to cause the melamine condensate to form by.
hea.ting the aforesaid composition at about 90C for ap-prox. 6 hours - the starting pH value of 9. 5 - 9.8 being adjusted to the value of 7.5 - 7.8 - til:L a viscosity of 420-470 centipoises at 20c is attained, whereupon, af-ter having adjusted the pEI to a value of 7-7 . 6, it is 'diluted with wa-ter, so obtaining a solution'at about 38%
of dry substance and with a viscosity of 40-50 centi-poises at 20C, pH a.djustments~are effected by means of hydrochloric'acid in an aqueous solution at 18%, thus ca.tionizing the melamine condensate. . --b) Encapsula.ting red phosphorus powder~
a hydrodispersion of micronized red phosphorus powder having a density of 1. 38 -1 . 58 is additioned with a desir-ed amount of'the aqueous solution at 38% of cationized melamine condensate, prepared as per point a.); the so ob-tained phosphorus dispersion in the melamine condensate solution is heated, under stirring, for about 1 hour at approx. 100C, keeping substantially unaltered-- by means of a condenser - the reaction mixture volume:
under such condi-tions the melamine condensate precipitat-es slowly and uniformly (evolving formaldehyde) in the 30 form of a resin partially cross-linked, at first in the ' liquid-viscous, then in the solid state7 around the red phosphorus particles 9 SO encapsulating them. Cross-link-ing is then completed during dehydration by dryi~g of the-product, preferably in a thin layer, a.t about 100C
and in an inert ga.s flow or preferably under vacuum, 5 -till formaldehyde does no longerevolve~At the end a red phosphorus powder is obtained, which is free-flowing, stabilized to phosphine forming and ea.sily dispersible intO the polymeric ma.terials, for example by means of pro-cesses ba.sed on plastic mass melting, or by incorporation into hydrodispersions a~a aqueous polymaric emulsions, which are then utilized in film-forming processes (for .
example paints, glues, etc.), by incorporation into elas-tomers, by dispersion into polymeric product solutions, by dispersion into pre-polymeric liquid systems with one or more componen-ts and the like.
- A variant of the process object of the present invention - consists in adding to the red phosphorus powder hydrodis-persion, already encapsulated with cationized and partial-.
ly cross-linked melaminic resin, be~ore subjecting said dispersion to dehydration with simultaneous completion of-~
the resin cross-linking, a.vehicle, preferably a.water--soluble vehicle, in which, at the end of the process after dehydration, the stabilized red pshosphorus powder remains dispersed, so obtaining a solid composition,that e.g. can be flaked, or a.liquid composition, both compos-itions having a high red phosphorus content, for example of 70~, and being more advantageously or easily employ-able, under safe conditions, as anti-flame agents in the successive processes of additivation to the polymeric ma-terials. Said vehicle, to be selected from amongst -the ones which are consistent with the polymeric material to be used, may be for example -caprolactam or a paraffin wax - in such case the final composition is solid and in the form of flakes - or a. polyol or a paraffin oi.l, pre-ferably a chlorinated one - in such case the final com-5 position is liquid.
Theprocess object of the present invention and the corres-pondingproduct will be better comprehended on the ba.sis ofthe following examples, which are given for merely il-lusirative but not limitative purposes.
Example 1 .
640 g of an a.queous solution containing 45i~o of formalde-hyde (9.6 moles), 70.5 g (2~2 moles) of me-thanol, 238~78 g (1~6 moles) of trie-thanolamine were introduced into a con-15 ven-tional rea.ctor, known in the art, equipped with elec-trical heating, a reflux condenser with a vacuum inta.ke and a magnetic stirrer, after having started both stirrer and condenser. The mixture so obtained, having a pH = 9~8 was brought to 85C and maintained at such tempera.ture for 20 2 hours, After cooling to 50C, 201~8 g ~1~6 moles).of~
melamine were added (the mixture now consisted for 36.04%:..
of formaldehyde, for 8~82% of methanol, for 29~87% of triethanolamine and for 25~27% of melamine?. The pH was adjusted to a.value of 7~6 by addition of 48 mi of hydro-25 chloric acid at 18% in an aqueous solution, and the mix-ture temperature-was raised to 90C and kept such for 6 hours, so obtaining a melamine condensate solution having a viscosity of 450 centipoises at 20Co At the end of this heating period said condensa.te solution was s-tabiliz-ed by àddition of 390 ml of wa.ter and by a.djusting the pHto a value of 7.5by adding 80 ml hyd~ochloric acid at 18~o in an aqueous solution, finally obtaining a solution of cationi~ed melamine condensate at 38.3% of dry substance having a viscosity of 40 centipoises at 20C. The above--cited pH adjustments represent the cationizing steps of the melamine condensate.
27.6 ml of the a.bove-obtained solution of cationized me-lamine condensate were drawn andl~jintroduced in-to a reactor (equipped with a mechanical stirrer, a condenser and a heating jacket) along with 300 g of red phosphorus powder, having a particle size below 40 microns, in the form of an a.queous dispersion having a density of 1.38. At the conclusion of this operation the components were homogen-ized by stirring, thus obtaining a red phosphorus powder suspension in a. cationized melamine solu-tion condensa.te, which wa.s heated at 100C for 1 hour. During such heating time the condensate got insoluble (with formaldehyde evol-ution)and slowly and uniformly precipitated, in the form of.a partially cross-linked melaminic resin, a.t first in the liquid-viscous state then turning-lnto the solid ~
state, onto the particles' surfaces of the red phosphorus powder, which were thus encapsulated by a very adherent, continuous and compact layer of said resin; finallyg a water dispersion of red phosphorus encapsulated by me-laminic resin, having a slurry-like consistence was ob-tained. Said.dispersion was spread to form a thin layer 25 of 2-3 mm thickness in a -tray and wa.s put into an oven at 90C under va.cuum, at a residual pressure of approx.
30 mm ~g, till formaldehyde evolution was no longer observ ed. During such drying,bo~h dehydra.tion of said ~ispersion and completion of melaminic resin cross-linking occurred, and at the end a friable layer, easily convertible into a - , , -free-flowing product, of red phosphorus in powder encap-sulated with 4~0 of melaminic resin wa.s obtained; such powder proved to be stable to phosphine forming and was easily dispersible into the polymeric materials as self--extinguishing product.Said enca.psulated phosphorus powder . was exposed three mon~hs to the air and during such time the pra.ctical absence of phosphine (less than 0O3 ppm~
was checked by means of a detector apparatus of the type equipped with a little suction pump and a detecting phial, having a minimum sensitivi-ty to phosphine of 0.1 ppm (Dr~ger ~Iulti Ga.s Detector Mod. 21/31 ) ~
The melaminic resin obtained as explained hereinbefore wa.s subjected to infrared spectroscopic analysis; said analysls revealed an absorption band at 2810 cm 1 cor-responding to symmetrical stretching ~ OCH3 and a greatintensification of -the band at 1080 cm corresponding to ethereal stretching ~ COC, what clearly points out that .such resin was methylated due to the chemical action of methyl alcohol in the above-described reactions. -:
Example 2 Using the same apparatuses~ modalitiesland substa~nces~as in example 1, a red phosphorus powder encapsulated with . melaminic resin was prepared, with the only exception that the per cent composition of the starting components of the melaminic condensate were as follows : 34.66~ of for-maldehyde, 12~34% Of methanol, 28~72% of triethanolamine and 24 ~ 287~o of melamine.
Such condénsate exhibited a viscosity (after stabiliz--: ;.
ation) of 33 centipoises at 20C~ The encapsulated red phosphorus powder so obta1ned was endowed with properties .
... . .. . .
-~L~6Z~
like those of example 1.
- Example 3 Using the same apparatuses, modalities and substances a.s in example 1, a. red phosphorus powder encapsulated with melaminic resin was prepared, with the only variant that the per cent composition of the starting components of the melamine condensate were as follows : 30.85% of formalde-hyde, 21.9.~% of methano~, 25.57% of triethanolamine and 21.62% of melamine.
Said condensatè exhibi-ted a viscosity (after stabilization) of 23 centipoises at 20C. The encapsulated red phosphorus powder so obtained was endowed with properties like the ones of example 1.
~xample 4 - 15 Using the same apparatuses, modalities and substances as --in example 1,.with the only ~ariant of including in the melamine condensate composition 148 g of butanol instead .
of methanol, a-red phosphorus powder encapsulated wi-th melaminic resin was preparedj which exhibited substantial-ly the same characteristics as the one obtained in ex-ample 1, in particular as regards the stability to phos-phine forming.
Example 5 Using the same appa.ratuses, modalities and substances as - 25 described in example 1, a powder of red phosphorus encap-sulated with melaminic resin was prepared, with the ~a-.riants of using orthophosphoric acid in an aqueous sol-ution at 80% as cationizing mineral acid, and of effecting . dehydration~by drying in a nitrogen stream at 1~0C.
~he encapsulated red phosphorus powder had the sa~e char-: acteristics as the one obtained in example 1.
79~
Example 6 .-Using the same appara-tuses, modalities and substances as described in example 1, a composition consisting of ~ -caprolactam incorporating~ in a. dispersed manner, 70% of red phosphorus powder encapsulated with melaminic resin was prepared9 the variant brought to the process consist-ing in adding 128 g of-caprolactam to the hydrodispersion of red phosphorus powder at the end of the encapsulation wi-th the partially cross-linked melaminic resin, and in going on heating the reactor containing the mixture of-the aforesaid components for 2 hours at 100C, always keeping the reactor stirrer running and creating a vacuum ih the reactor. During such time-period the mixture de-hydrated and the resin completed its cross-linking, fin-ally providing a homogeneous dispersion of an encapsul- -.
a.ted red phosphorus powder in molten ~ -caprolactam.
Said moltén productwas poured in thin layer into trays- ~ ;
where it solidified hy cooling, whereupon the product was reduced to flakes which proved to be stable to phosphine~
forming and could be easily incorporated into polyamides ~
during hot extrusion thereof in extruder, in order to im- ;
part the desired self-extinguishing properties to them.
Example 7 -. ~ .
. Using the same apparatus a~d modalities as in-example 1, : 25 but employing, instea.d of ~ -caprolactam, the same amount o~ a polyol-polyether (obtained from ethylene ox-ide and propylene oxide with a hydroxylinumber of 56 and a.viscosity of 550 centipoises), a liquid composition consisting for 709 of red phosphorus powder encapsula.ted 30 with melaminic ~eisin, according to example 1, dispersed in said polyol was prepared~ In this case, at the end ' ., i of the dehydration step and cross-linking completion step of the melaminic resin, a liquid composi-tion ~as ob- ~
tained, which proved stable to phosphine forming and al-ready ready to be ea.sily incorporated into the compos-itions intended for the production of polyurethane resins al.so of the foamed type, in order to impart self-exting-uishing properties to them.
Example 8 In a conventional horizontal drum mixer known in the art, 25 kg of a homogeneous mixture consisting for 88% of poly-amide 6-6 in cylindrical 3x3 mm granules for general uses,and for 12% of the composition of red phosphorus dis-persed in -caprolactam obtained in example 6 were pre-pared. Said mixture was put into a single-screw ex-truder equipped with an electrical heating device, in which the.
mixture was homogenized in the molten state and came out -~
from the extruder head in the form of strands which, af-ter cooling in water and passing through a cutter, were reduced to cylindrical 3x3 mm granules from whichj~by`in-- .
jection molding, specimens `of 152.4 mm length, 12.7 mm~
width~- and 1.6 mm thickness were obta.ined, which were sub jected to the self-extinguishing test according to the ~
vertical flame method U~-94 (Underwriter ~aboratory Bul-letin 94) by vertically pla.cing the specimens being test-ed on a Bunsen flame for 10 seconds and then for further ~10 seconds after combusti~n extinguishing. The polyamide material additivated as explained hereinbefore may be classified, according to said U~-94 method, as a self-ex-- tinguishing substance of V-0 degree. During all the afore-said mixing , extruding and molding operations, the phos-p`ine forming, determined by means of the detector des-. , .
scribed in example 1, was always below 0.3 ppm.
- Example 9 25 kg of high density polyethylene (density = 0.955 ~
ml) in sperica granules (diameter = about 3 mm)g homo-geneously wetted with 120 ml of vaseline oil (density =
0.877) were introduced into the mixer of example 8;
then 2 kg of the encapsula.ted red phosphorus powder of example 1 with 4~ of melaminic resin were added and the whole was mixed for 30 minutes. At the end of such mix-ing, polyethylene granules homogeneously coated with en-capsulated red phosphorus powder were obta.ined, which were fed to an electrically hea.ted single-screw extruder having a hea.d temperature of about 200C, so obtaining strands which, after cooling in wa-ter and passing .15 through a cutter, were reduced to cylindrical 3x3 mm granules, from which, by injection molding, specimens were obtained havinga-length of 152.4 mm, a width of 12.7 mm and a thickness of 1.6 mm. After having been ;
` subjected to the UL-94 self-extinguishing~test descr1b-~
: 20 ed in example 8, they were classified of degree V~
the extinguishing time ranging from 6 to 10 seconds.
During all the above-mentioned mixing, ex-truding and molding operations, the phosphine formingg checked by . means of the detector described in example 1, was al-ways below 0O3 ppm.
Example 10 ~or comparative purposes, in order to prove the subs-tantial importance of methyl alcohol for the ch.~racter-istics of the melamine condensate9 of which it is a component, and the consequent influence o~ such char-a.cteristics on the encapsulation process object of the 7~
present invention, a cationized mel amine condensate was prepared (using the same apparatuses and modalities of ex-ample 1) by reacting 39053% of formaldehyde, 32.77~0 of tri-ethanolamine and 27.70% of melamine~ Said condensate,of 5 the same type as the one described in the already cited U.S.patent 3,721,651,ezhibited,after stabilization,a vis cosity of 260 cps at 20C,substa-ntially higher than the one of the corresponding condensate of example 1; during the successive red phosphorvs powder encapsulation step 10 (always according to example 1) it was noticed that the encapsulation process'occurred by insolubilization of the melalnine condensate directly in -the solid state, without passing through the liquid-viscous phase.
Furthermore, the infrared spectroscopic analysis oE'-the melaminic resin so obtained, did not show the absorption --band'~) OCH3 that was observed in the corresponding resin of example 1. From the foregoing, -particularly from ex-amples 1 and 10, it is evident that there is a correlation between the participation o`f -the alcohol in ~the~ compositlon-20 of the melamine condensate and the characteristics of the latter, such characteristics being, in their turn, advant-ageous for purposes of 'obtaining àn excellent encapsul-ation of the red phosphorus powder, according -to the pro-' cess of the present invention.
of course, modifications and variations, all falling with-in the scope of the inventive principle, may be brought to the invention as described hereinbefore, and the pro-cess and product details may be replaced by other tech-30 nically equivalent elements.
Claims (18)
1. A process for stabilizing red phosphorus powder, in its various allotropic forms, by encapsulating the particles of said powder in a melamine resin for its safe use as a flame retardant of polymeric materials, which comprises the steps of:
(a) preparing an aqueous solution of a mela-mine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, triethanolamine, and an aliphatic monohydroxyl alcohol having up to 5 carbon atoms, in the respective percent by weight ratios: 25.27% to 21.62%, 36.04% to 30.85%, 29.87% to 25.57% and 8.82% -to 21.96% and adjusting the pH thereof with -the mineral acid:
(b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein;
(c) heating said hydrodispersion, under stirring, at 80° to 100°C to encapsulate individual particles of the red phosphorus powder by precipitating onto said individual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin, and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80° to 130°C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric materials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 -to 30% by weight of the red phosphorus powder.
(a) preparing an aqueous solution of a mela-mine condensate cationized with a mineral acid by reacting in an aqueous medium melamine, formaldehyde, triethanolamine, and an aliphatic monohydroxyl alcohol having up to 5 carbon atoms, in the respective percent by weight ratios: 25.27% to 21.62%, 36.04% to 30.85%, 29.87% to 25.57% and 8.82% -to 21.96% and adjusting the pH thereof with -the mineral acid:
(b) forming a hydrodispersion of the solution formed in step (a) by dispersing red phosphorus powder directly therein;
(c) heating said hydrodispersion, under stirring, at 80° to 100°C to encapsulate individual particles of the red phosphorus powder by precipitating onto said individual particles of red phosphorus powder, said melamine condensate to form a continuous and compact layer of an insoluble, partially cross-linked melamine resin, and (d) subsequently drying the insoluble, partially cross-linked layer of melamine resin in an inert gas stream at 80° to 130°C to obtain a cross-linked melamine resin-encapsulated red phosphorus powder suitable for easy and safe dispersion in polymeric materials, said layer of melamine resin which encapsulates said red phosphorus powder amounting to 0.1 -to 30% by weight of the red phosphorus powder.
2. A process according to claim 1, step (a), wherein said aqueous solution of melamine condensate is obtained by first reacting, for about 2 hours at approx. 85°C and at a pH of 9.5 - 9.8, the formaldehyde, the aliphatic monohydroxyl alcohol, and the triethanolamine, the melamine being added in a second step at the end of the aforesaid reaction, in order to cause the melamine condensate to form by heating of the aforesaid composi-tion at approx. 90°C for about 6 hours at a pH of 7.5 -7.8 till attaining a viscosity of 420-470 centipoises at 20°C, then in a third step adjusting the pH with a mineral acid to a value of 7 - 7.6, and diluting with water until obtaining a solution with about 38% of dry substance and with a viscosity of 40 - 50 centipoises at 20°C.
3. A process according to claim 1, step (a), wherein said hydrodispersion of the red phosphorus powder in the aqueous solution of the melamine condensate is obtained by mixing said aqueous solution with a red phosphorus powder hydrodispersion having a density of 1.38 - 1.58.
4. A process according to claim 1, step (a), wherein said mineral acid is hydrochloric acid and said aliphatic monohydroxyl alcohol is methanol.
5. A process according to claim 1, step (a), wherein the red phosphorus powder has a particle size of less than 100 microns.
6. A process according to claim 1, step (c), wherein said heating of said hydrodispersion lasts about 1 hour, maintaining unchanged the volume of the reacting mixture.
16 .
16 .
7. A process according to claim 1, wherein step (d) is carried out under vacuum at 100°C.
8. A process according to claim 1, wherein following step (b) the red phosphorus powder encapsulated with melamine resin is dispersed at a concentration of higher than 50% by weight in a water-soluble vehicle to obtain the encapsulated red phosphorus powder in a liquid form or in flakes.
9. A process according to claim 8, wherein the water soluble vehicle in which the red phosphorus powder encapsulated with melamine resin is dispersed, is .epsilon.-caprolactam and the encapsulated red phosphorus powder is obtained as flakes.
10. A process according to claim 8, wherein the water-soluble vehicle in which the red phosphorus powder encapsulated with melamine resin is dispersed, is a polyol or a paraffin oil and the encapsulated red phos-phorus powder is obtained as a liquid.
11. Red phosphorus powder stabilized by encapsulation in a continuous and compact layer of melamine resin whenever obtained by the process defined in claim 1.
12. Red phosphorus powder as defined in claim 11, encapsulated in a melamine resin, suited to be used as safe flame retardant for polymeric materials, which comprises particles of red phosphorus having a means diameter of less than 40 microns encapsulated in a con-tinuous and compact layer of a modified melamine resin, which resin is a poly-condensation product of 25.25-24.28%
melamine, 36.04 - 34.66% formaldehyde, 29.87 - 28.72%
triethanolamine, and 8.82 - 12.34% methanol.
melamine, 36.04 - 34.66% formaldehyde, 29.87 - 28.72%
triethanolamine, and 8.82 - 12.34% methanol.
13. A solid flame-retardant composition for poly-amides, which comprises encapsulated red phosphorus powder stabilized according to the process defined in claim 1, and an .epsilon.-caprolactam.solid vehicle
14. A liquid flame-retardant composition for poly-urethanes, which comprises encapsulated red phosphorus powder stabilized according to the process defined in claim l,and a polyol liquid vehicle.
15. A self-extinguishing polymeric composition which includes 0.5% to 20% by weight of the red phosphorus powder encapsulated with melamine resin according to the process defined in claim 1.
16. A self-extinguishing polymeric composition which includes 3% to 15% by weigh-t of the red phosphorus powder encapsulated with melamine resin according to -the process defined in claim 1.
17. The self-extinguishing polymeric composition defined in claim 16, in which the polymer is a polyamide.
18. The self-extinguishing polymeric composition defined in claim 16, in which the polymer is a polyolefin.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT26064-A/80 | 1980-11-19 | ||
| IT26064/80A IT1134333B (en) | 1980-11-19 | 1980-11-19 | PROCESS TO STABILIZE THE RED PHOSPHORUS BY ENCAPSULATION FOR USE AS A FLAME RETARDANT OF POLYMERIC MATERIALS AND PRODUCT SO OBTAINED |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162794A true CA1162794A (en) | 1984-02-28 |
Family
ID=11218551
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000387399A Expired CA1162794A (en) | 1980-11-19 | 1981-10-06 | Process for stabilizing by encapsulation red phosphorus to be used as flame retardant of polymeric materials and product so obtained |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4440880A (en) |
| EP (1) | EP0052217B1 (en) |
| JP (1) | JPS57113832A (en) |
| CA (1) | CA1162794A (en) |
| DE (1) | DE3173462D1 (en) |
| ES (1) | ES506447A0 (en) |
| IT (1) | IT1134333B (en) |
| PT (1) | PT74005B (en) |
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|---|---|---|---|---|
| IT1137409B (en) * | 1981-03-05 | 1986-09-10 | Saffa Spa | SELF-EXTINGUISHING PAPER MATERIALS |
| CA1196437A (en) * | 1981-12-19 | 1985-11-05 | Kazushi Hirobe | Flame resistant resin composition |
| IT1157253B (en) * | 1982-02-09 | 1987-02-11 | Saffa Spa | PROCEDURE FOR MAKING SELF-EXTINGUISHING, THROUGH RED PHOSPHORUS, SYNTHETIC THERMOPLASTIC MATERIALS AND PRODUCTS SO OBTAINED |
| IT1165453B (en) * | 1983-07-04 | 1987-04-22 | Consiglio Nazionale Ricerche | PROCESS FOR THE PREPARATION OF THERMOPLASTIC BODIES SELF-EXTINGUISHING FORMATS BASED ON POLYCAPROLACTAM |
| IT1200424B (en) * | 1985-03-19 | 1989-01-18 | Saffa Spa | RED PHOSPHORUS STABILIZED FOR USE AS A FLAME RETARDANT, ESPECIALLY FOR POLYMER-BASED COMPOSITIONS |
| IT1186738B (en) * | 1985-06-27 | 1987-12-16 | V A M P Srl | RED PHOSPHORUS STABILIZED AND VEHICULATED AS POLYMER FLAME RETARDANT |
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| US20070134411A1 (en) * | 2005-12-14 | 2007-06-14 | General Electric Company | Method for making compositions containing microcapsules and compositions made thereof |
| KR100730835B1 (en) * | 2006-02-22 | 2007-06-20 | 엘에스전선 주식회사 | Composition for production flame retardant insulating material including micro capsulated flame retardant supplement |
| KR101824268B1 (en) | 2009-12-16 | 2018-01-31 | 바스프 에스이 | Flame retardant |
| US8691896B2 (en) * | 2010-02-05 | 2014-04-08 | Basf Se | Halogen-free, phosphorus-containing flame-retardant polymer foams |
| MX2012008979A (en) | 2010-02-05 | 2012-08-23 | Basf Se | Flame retardant. |
| US20110196052A1 (en) * | 2010-02-05 | 2011-08-11 | Basf Se | Flame retardants |
| JP2013518956A (en) | 2010-02-05 | 2013-05-23 | ビーエーエスエフ ソシエタス・ヨーロピア | Non-halogen, phosphorus-containing flame retardant polymer foam |
| WO2013017417A1 (en) | 2011-07-29 | 2013-02-07 | Basf Se | Polymer flame retardant |
| PL2574614T3 (en) | 2011-09-30 | 2019-10-31 | Basf Se | Flame-retardant polymer foams with halogen-free flame-retardant agents containing phosphorous on a sugar basis |
| CN102775814B (en) * | 2012-08-10 | 2014-03-19 | 四川省精细化工研究设计院 | Method for preparing micro-encapsulation red phosphorus |
| CN106103820A (en) * | 2014-03-11 | 2016-11-09 | 智能聚合物有限公司 | The flame retardant fibre element molded body prepared according to direct dissolution method |
| CN111635571B (en) * | 2020-06-03 | 2023-03-03 | 杭州联通管业有限公司 | Flame-retardant polyethylene communication pipe and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1694539C3 (en) * | 1967-06-06 | 1973-10-18 | Knapsack Ag, 5033 Huerth-Knapsack | Process for the production of self-extinguishing copolymers from styrene and acrylonitrile |
| US3657027A (en) * | 1969-04-09 | 1972-04-18 | Us Army | Injection moldable flammable composition and devices made therefrom |
| GB1305187A (en) * | 1969-05-22 | 1973-01-31 | ||
| US3806488A (en) * | 1971-09-14 | 1974-04-23 | Allied Chem | Stabilized flame resistant polyamides |
| US4010137A (en) * | 1973-07-24 | 1977-03-01 | Phillips Petroleum Company | Phosphorus-containing flame retardant for synthetic resins |
| US3968060A (en) * | 1973-08-22 | 1976-07-06 | Champion International Corporation | Encapsulated flame retardant system |
| US4105735A (en) * | 1974-02-22 | 1978-08-08 | Hoechst Aktiengesellschaft | Process for flameproofing plastics |
| US4182839A (en) * | 1974-07-31 | 1980-01-08 | Manufacture De Produits Chimiques Protex Societe Anonyme | Process for the preparation of cationically modified formaldehyde resins of prolonged stability |
| US4208317A (en) * | 1975-06-10 | 1980-06-17 | Rhone-Poulenc Industries | Flameproofed plastic compositions |
| GB1576879A (en) * | 1976-09-20 | 1980-10-15 | Hitachi Ltd | Flame-retardant epoxy resin compositions |
| FR2367100A1 (en) * | 1976-10-11 | 1978-05-05 | Rhone Poulenc Ind | FIRE-RETARDANT POLYAMIDE-BASED COMPOSITIONS |
| DE2646835C2 (en) * | 1976-10-16 | 1984-11-15 | Bayer Ag, 5090 Leverkusen | Micro-encapsulated red phosphorus as a fire retardant for polyamide molding compounds |
| CA1097152A (en) * | 1976-12-09 | 1981-03-10 | Horst Staendeke | Stabilized red phosphorus and process for making it |
| DE2705042A1 (en) * | 1977-02-08 | 1978-08-10 | Hoechst Ag | STABILIZED RED PHOSPHORUS AND THE METHOD OF MANUFACTURING IT |
| DE2655739C2 (en) * | 1976-12-09 | 1978-12-14 | Hoechst Ag, 6000 Frankfurt | Stabilized red phosphorus and process for its manufacture |
-
1980
- 1980-11-19 IT IT26064/80A patent/IT1134333B/en active
-
1981
- 1981-10-06 CA CA000387399A patent/CA1162794A/en not_active Expired
- 1981-10-07 EP EP81107981A patent/EP0052217B1/en not_active Expired
- 1981-10-07 DE DE8181107981T patent/DE3173462D1/en not_active Expired
- 1981-10-22 US US06/314,049 patent/US4440880A/en not_active Expired - Fee Related
- 1981-10-22 ES ES506447A patent/ES506447A0/en active Granted
- 1981-11-18 PT PT74005A patent/PT74005B/en unknown
- 1981-11-19 JP JP56184536A patent/JPS57113832A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| US4440880A (en) | 1984-04-03 |
| PT74005A (en) | 1981-12-01 |
| ES8205713A1 (en) | 1982-08-16 |
| IT8026064A0 (en) | 1980-11-19 |
| EP0052217B1 (en) | 1986-01-08 |
| EP0052217A1 (en) | 1982-05-26 |
| ES506447A0 (en) | 1982-08-16 |
| DE3173462D1 (en) | 1986-02-20 |
| IT1134333B (en) | 1986-08-13 |
| JPS57113832A (en) | 1982-07-15 |
| PT74005B (en) | 1983-03-31 |
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