CA1166795A - Flame retardant polymeric compounds - Google Patents

Abstract

A b s t r a c t There are described certain polymeric compositions which are rendered flame retarding, provide an incandescent char-forming crust, are not dropping and do not produce or emit toxic fumes; this is achieved by the addition, per 100 parts by weight of polymer, of 5-40 parts by weight of the reaction product between an acid of phosphorus and at least one hydroxyalkyl derivative of a-t least one compound selected from the group isocyanuric acid, melamine and urea, and, in a modified embodiment, in addition to the above indicated reaction product, of 5-30 parts by weight of a polymer of an ammonium poly-phosphate of formula (NH4PO3)n9 wherein n" is greater than 20.
In a further modified embodiment there is added amine phosphate, such as the ortho- or pyrophosphate of melamine, in an amount of 1 - 10 parts by weight.
The above mentioned reaction product comprises in its molecule the formula N-(R)n1 -O-P

wherein R is at least one linear or branched alkylene-derivative, n' is comprised between 1 and 6, and P is tri- or pentavalent.

Description

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~he present invention concern~ self e~tinguishing polymeric compo~i~ions wh~ch, upon contacting a ~lame provide a~ ~ char-forming c~st and do not produce flame~ nor toxic ~umes; more particularl~
it concern tho preparation o~ a ~ynthetic orga~ic compound which contai~ pho~phoru~ and nitrogen and which, added to ~thetic polymer~ ~uch ~3 pol~propy-lene9 pol~eth~lene, copolymers a~d acrylonitrile-butadiene-styrene ble~d polymers~ polye~ters, pol~-amide~, polycarbonates, or mixture~ o~ such polymersmutuall~ added a~d/or with ela~tomer~ and/or with con~entional ~illers a~d additive~ la polymerlc compo~ition~ which when co~tacting a flame, ~rovide a charformi~g ~ crust, are ~ ~an~
do not produoe ~lame~ nor toxlc fumes~

Several proce~æe~ for making fireproo~ or uninflammable polymers are know~ i~ the art; su¢h proce~es are generally ba~ed upon the use of metallic compounds, particularly antimony ones~ in combination with thermall~ unstable h~lo~enated compou~d3~ such as ~or example chlorinaked paraf~i~

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waxes and/or bromided organic compound~a The art has propo~ed~ to act a~ flame-retardant and flame barrier ~everal phosphorus containing com-pound~, for example as disclosed in the United State~Patent No. 4,010,137, the disclo~ure of which i~
herein referred toO

The combinations "metallic compound + halogenated compound" ~ield ~atisf~ing results a~ far AS regard8 the flame-retardant properties conferred thereby to the polymers, but the~ are ~ubject to serious draw-backs: corrosive phenomena in the machine~ and installations in which the treatment of the materials i~ performed, and intense emission of toxic fumes and gase~ when a fire occur~. Further, acceptable flame retardanc~ levels are obtained by making use of high concentration of such combi~ation~ only.

It has now been surpri~i~gl~ ~ound that it i3 possible to render thermoplastic pol~mer~ of the t~pe referred to above flame-reta~da~t~ by the addition of a particular organic compound which doe~
not at the same time give rise to the above indicated dr~wback~. -~he present invention concerns flame retardant pol~-` meric compounds which upo~ contac~ with a ~lame, ,~ esc~
provide an ~n~e~e~ char-~orming cru~t~ which 30 are ~an9d do not produce flames nor toxic fumes~ such pol~meric compounds being characterized b;sr comprising, per 100 parts b~ weight of a thermo-plastic pol~mer, from 5 to 40 par-ts by weight of a reaction product having a chemical ~tructure of the 3. ~l t~ t; 7 ~a~

t~pe.

(R)nl P

in which R is an alkylene derivative~ n' is comprised between 1 and 6, the said reaction product including more than one nitroge~ atoms interbonded with one another throu~h one or morè carbon atoms;
according to a particular embodime~t~ to ~aid reaction product there may be associated fro~ 5 to 30 parts b~ weight of a pol~mer con~isting of an ammonium polyphosphate, and9 i~ a further modified embodiment, amine phosphate.

According to the above said modified form the pol~mer of ammonium polyphosphate is mixed with a~ ami~e phosphate (ortho- or melamine pyrophosphate) in an amount o~ 1-10 part~ by weight of amine phosphate per hundred parts by weight o~ the thermopla3tic pol~-mer.

~he ammoniu~ polypho~phate polymer advantageou~l~con~i~ts of an ammonium polyphosphate having a chemical ~tructure of the t~pe (~H4P03)n,l, wherein n" i~ greater than 20.

~n the following of the pre~ent di~closure, -the above defined reaction product i8 indicated a~ component ~, while the ammonium pol~phosphate polymer iB indica-ted a~ component Bo ~he prese~t invention co~cerns also a process for producing the reaction product formin~ the component A) con~ist~l the proces~ bei~g characterized in that , ' .
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said reaction product is preliminarily obtained by reacting an acid of ~hosphorus with an hydroxyalk~l derivative~

The acid of phosphorus can be a phosphorou3 acid of formula ~3P03, i. e~ phosphoric acid~ the propertie~
and compo~i~ion of which ma~ vary according to its P04 contant, which can vary betweèn 50 and 120 % by weight, and preferably from 80 and 115 %.
According to a particular embodiment of the invention the pol~eric compositio~ is characterized by the fact that, in the component A), the alkylene derivative is a hydroxyaIkyl derivative of an iso-cy~nuric acid, of a melamine or o~ a~ urea.

In some particularly preferred, though not limitative embodiments of the invention:

a) the isocya~uric acid hydroxyalkyl derivative is preferably the tris(2-hydroxyethyl)isocyanurate having a nitrogen content from 15 to 17 % b~
weight, and a melting point be-tween 132 C and 138 C;
b) the hydroxyalkyl derivative of the melamine i5 a methylol deri~ative, such as the trimethylol- or the hexamethylolmelamine;

c) the h~droxyalk~l derivative of the urea i~ also a methylol derivative9 in particular NN' dimethylol urea.

The reaction product between the acid of pho~phorus 7 ~

and the or the several hydrox~alkyl derivative(s) of the isocy~nuric acid and/or of the melamine and/or of the urea is preferably obtained by introducing -the reagents into a reactor provided with a stirrer, of the two-walled t~pe heated by circulati~g warm oil, ~na provided with a degassing vacuum system. The te~perature may vary from 140 C -to 260 C duriug the entire reaction time~ which in turn may vary between

2 and 7 hours~
~he molar ratio between the acid ~f the phosphorus Qnd the or the several hydroxyalkyl derivative(s) of the isocyanuric acid and/or of the melamine and/or of the urea is compri~ed between 4:1 and 0~1:4.
It is also possible to use s~nthesis method~ such as the esterification of the hydroxyalkyl derivatives which phosphorus halides or b~ mean~ of trans-esterification reactio~s between phosphoric esters and hydroxyalkyl derivatives.

~he reaction products forming said component A) and the ammonium polypho~phate pol~mer forming sQid component B) 7 a~d al~o 7 i~ the de~cribed modified embodiment7 the amine phosphate can be added to an~
type of thermoplastic pol~mer, particularly pol~mers and copolymers (either statistioal or block polg~ers) e. g. of ole~ines, of pol~olefines, of vin~l monomers~
of esters and of amides~ and mi~tures of said poly-mers with elastomers; the same ~ubstance~ and com-pounds can also be utilized for the production of varnishes, coatings and fibers~

The respective flame retardant composition~ are . .
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prepared by utilizing kno~m techniques, that is by mixing the polymer to be rendered flame retardant, the reactio~ products of type ~) and al~o, in the second embodiment, the ammonium pol~pho~phate and, in the modified embodiment, amine phosphate in a Banbury type mixer, or two-screw extruder, operating at the plasticization temperature of the polymer. ~he batch or mixture thus obtained is then compression molded at the most suitable temperature for providing the desired articles of manufacture.

The flame retarding properties of the polymeric compositions o~ the present invention are d~termined by compressing the granular product into sheet having a thickness of 3 mm, by means of a ~mall press and operating for 7 minutes with a pressure of 40 Kg/cm at a suitable temperature which mag var~ from polymer to pol~mer. On the thus prepared sheets the flame retarding level is determined either b~ measuring (according to the ~S~M D-2863 ~pecification) the "oxYgen index", which indicates the minimal percentage ~ 2 in a mixture 02/N2, which is required for the sample to burn continuousl~, or al~o by making use of the U~-94 ("Underwriters ~aboratorie~" - Y.S.h.) specification~, which provide for an evaluation of the flame retarding property ra~ing of the elastic materials, and rel~ on more or les~ severe testing condition~7 whereby to classif~ the sampl~ within a range or echelon o~ different flame retarding levels.

In the te~ts indicated hereinbelow in ~able I use ha~
bee~ ma~e of the "Vertical Burning Test" permitting to clas~ify the material at decreasing levels V-O, 7~

V-1 a~d V-2.

Each test is made on a group of 5 samples having a thickness of 1~8 inch, which are sustained in vertical position, and which are primed by flame at their lower end; two ignition attempts, each of 10 seconds, are made.

~he three flame retarding levels V-0, V-1 and V-2 are defined as follows:

V-O = ~o sample burns for more than 10 seconds, after each application of a flame, nor do they show an~ dropping of ignited particles.
~urther, the total combustion time is no longer than 10 seconds for any attempt effected on the group of 5 samples.

V-1 = At this level, combustion times up to 30 seconds are admitted for each individual test and up to 250 seconds for 10 attempts made on the group of 5 samples~
At this level7 too, no sample shows a~ drop-ing of ignited particles.
V-2 = ~t this level, the admitted combustion times are the same as for level Y-17 but the dropping of ignited partlcle~ is admitted.

~he several aspects of the invention are illustratea by the following ~xamples which, however~ should not have any limitative effect nor should they be construed limitativel~.

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~xamples 1 to 6 relate to the use of component A
only, while Examples 7 to 12 relate to the use of component B associated to component A.

Example 1 In a 2.500 cc. reactor, 70 gr. of phosphoric acid (~3P04 - ~5 %) are reacted with 250 gr. of tris(2-h~droxyeth~l)isoc~anurate, under stirring at a temperature of 150 C for 1,5 hours. ~hereafter a vacuum of 300 mm Eg is applied and the temperature is raised to 250 C for a period of 4 hours.

During this latter period the reaction H20 is removed and substantial cross-linking is created in the compound between the various molecules of the phosphoric ester which has been formed-in the ~irst stage of the reaction. The product is then discharged from the cooled reactor and milled into a powder of granules having a diameter of less than 80 microns~

~xample 2 800 gr. of phosphoric acîd (H~P03 = 85 %) are reacted with 200 grams of tris(2-h~droxymethyl)isocyanurate and 100 grams of tri~methylolderi~ati~e of melamineO
~he reaction is conducted in accordance with ~xample 1 and ~rom the reactor a product is di~charged which upon cooling and milling in powder ~orm has proper-ties substantiall~ equivalent ~o that of the product of Example 1.

~xam~le 3 350 gr. of phosphoric acid (~P04 = 100 %) are reacted with 200 gr. of tris(2-hydroxyethyl)iso-cyanurate and with 300 gr. of N,N'dimethylolethylen-urea. ~he reactio~ proceeds as described in Example 1, and the respective product also is comp~ able with those of Examples 1 and 2.

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600 gr. of phosphoric acid (~3P04 = 115 %) are reacted with 150 gr. of trishydro~yethyl isocyanurate, 150 gr. of trimethylol-derivative of melamine and 50 gr. of N,N' dimethylolurea.
~he reaction is made to proceed i~ accordance with Example 1 and a produkt is obtained having characteristics similar to those of the products of the preceeding ~xamples~

~xample 5 Proceeding i~ the same way a~d under the same conditions as in Example 1, 620 gr. of phosphoric acid (~3P03 - 90 %) are reacted with 280 gr~ of N,~'-dimethylolurea and with 280 gr. of hexamethylol-~elamine: a product is discharged which i~ firstly cooled and then ground into a powder formed of granules of diameter less than 70 microns.

'7 Exam~le 6 Proceeding in the same way and under same conditions as in ~xample 1~ 800 grO of phosphoric acid (H3P04 = 85 ~) are reacted with 300 gr. of tri-methylolderivative of melamine, A product having characteristics comparable to those of Example 2 is obtained.
~he powders obtained in the preceedin~ Examples are mixed with the thermoplastic polymers in a Banbury type mixer at the most suitable temperature for ob-taining a granular product, such temperature varying from one polymer to other polymer~

The results, indicated in the following ~able as not limitative examples, are of basic value and importance for different thermoplastic polymers.

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TABLE I

Parts by weight ____ d ive Exa ple 30 Thermoplastic polymer 80 75 70 80 72 75 Oxygen index 28,5 28 30 26,5 29 29,5 UL 94 (1/?'') te~t V-0 V-0 V-0 V-0 V-0 V-0 , .
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~ . , 7~3 Ex~m~le 7 50 gr. of phosphoric acid (~3P04 = 85 %) are reacted with 250 gr. of tri~(2 h~droxyethyl) isocyanurate, in a 2.500 cc. reactor, under stirring at a temperature of 150 C, for 1,5 hours. Thereafter a vacuum of 300 mm Hg is applied a~d the temperature is raised to 250 C for a period of 4 hour~
During this latter time period the reaction H20 is removed and substantial cro~s linking is promoted i~
the compound between the various molecules of the phosphoric ester, which has been formed in the first stage of the reaction.
~he product is discharged from the cooled reactor and ground into a powaer the granules of which have a diameter o~ less than 80 microns.

~xample 8 200 gr. of phosphoric acid (H3P03 = 85 ~i) ~re reacted with 250 gram~ of tri~(2 hydrox~methyl) isocyanurate.
~he reaction is allowed to proceed according to Example 7 and a product is extracted which after being cooled and ground in powder-like condition ha~
characteristic substantiall~ equivalent to those o~
the product of Example 7 Exam~le 9 150 grO of phosphoric acid (H3P04 = 100 %) are reacted with 200 gr. of ~ris(2 hydro~ethyl~ iso~
cyanurate and with 300 gr. o~ N,N' dimethylol-.
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~ - 13 -eth~lenurea. ~he reaction is allowed to proceed a3 described in Example 7, and the respective product obtained is also comparab]e to those of Examples 7 and 8.

~xample 10 80 gr~ of phosphoric acid (H3POL~ = 115 %) are reacted 1~ with 150 gr. tris hisroxyethylisocya~urate, with 150 ~r. of trimethylol derivate of melamine and 50 gr. of N,N' dimeth~lolurea. ~he reaction is allowed to proceed according to Example 7 and a product is ob-tained having characteristics similar to those o~ the products of the prece0ding Eæamples.

xam~le 11 Proceeding in the same wa~ and under the same conditions as in Example 7~ 120 gr. of phosphoric acid (E3P03 = 90 %) are reacted with 280 gr. of N,N' dimeth~loleth~lurea and with 280 gr~ of hexa-methylolmelami~e. ~he extracted product after cooling is then ground into a powder formed of granules of diameter less than 70 mi~rons~

xample 12 Proceeding in the same way and under the sa~e conditions a~ in Example 7, 80 gr. of phosphoric acid (~3P04 = 85 %) are reacted with 300 gr. of tri-meth~lolderivative of melamine~

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A product having characteristics comparable to those of Example 8 is obtained.

The powders obtained from preceeding ~xamples 7 to 12 are mixed with the tnermoplast,ic pol~mers and with ammonium polyphosphate, and~ in the described modified embodiment in mixture with the phosphate of amine, in a ~an~ury t~pe mixer at the temperature which is most suitable for obtaining a granular product, said temperature varying from one polymer to the other.

The results are indicated as examples in the ~ollow-ing Table II, in which pol~propvlene is used as polymer, (but comparable results are obtained with other thermoplastic polymers)O

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~ABLE II

.. . . . . . .
Parts b~ weight _ . . .i . . . __ _ . _ .
Compo~ent A of ~xample 7 15 ~ol~phosphate NH4 15 ... _ ......... . . . _ . .
Component A of E~ample 8 10 Polyphosphate NH4 15 Orthophosphate of melamine 15 .
Component A of Example 9 15 Polyphosphate ~H4 10 Pyropho~phate of melamine 10 .. _ _ . . . . _ . _ Component A of Example 10 20 Polyphosphate N~4 10 _ _ . . _ _ ~ _ .. . . _ _ . . _ Component A of Example 11 18 Pol~phosphate NH4 12 Component ~ of Example 12 20 Polyphosphate NH4 15 _ _ . . . _ _ ~hermoplastic pol~Mer Polypropylene Melt index 10 70 70 65 - 7 7 65 O.x~gen index 33,5 32 30 28,5 29 29,5 UL 94 (1/9ll) test V~O V-O V-O V-O V~O V-O

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Flame retardant polymeric compositions which upon contracting a flame , provide an intumescent char-forming crust, which are non-dripping and promote neither flame nor toxic fumes, comprising in 100 parts in weight of a thermoplastic polymer, from 5 to 40 parts in weight of a reaction product between an acid of phosphorus and hydroxyalkyl derivative of isocyanuric acid, said reaction product having a chemical structure of the type N - (R)n1 - O - P
in which R is an alkylene derivative, and n' is between 1 and 6, said reaction product including a plurality of nitrogen atoms interbonded through one or more carbon atoms.

2. Flame retardant polymeric compositions which upon contacting a flame, are non-dripping and promote neither flame nor toxic fumes, comprising, in 100 parts in weight of a thermoplastic polymer:

(a) from 5 to 40 parts in weight of a reaction product between an acid of phosphorus and a hydroxyalkyl derivative of isocyanuric acid, said reaction product having a chemical structure of the type N - (R)n1 - O - P
in which R is an alkylenderivative, and n' is between 1 and 6, said reaction product including a plurality of nitrogen atoms interbonded through one or more carbon atoms: and (b) from 5 to 30 parts in weight of an ammonium polyphosphate.

3. Polymeric compositions according to claim 1 or claim 2 wherein the reaction product, the nitrogen atoms and the carbon atoms are interbonded in an heterocyclic structure.

4. Polymeric composition according to claim 1 or claim 2 wherein the hydroxyalkyl derivative of the isocyanuric acid is the tris (2 hydroxyethyl) isocyanurate.

S. Polymeric compositions according to claim 1 or claim 2 wherein the hydroxyalkyl derivative of the isocyanuric acid has the formula wherein R', R" and R"' are the same or different and linear or branched alkylenic radicals containing from 1 to 6 carbon atoms.

6. Polymeric compositions according to claim 1 or claim 2 wherein the molar ratio between the acid of phosphorus and the hydroxyalkyl derivative of isocyanuric acid is between 4 : 1 and 0.1 : 4.

7. Polymeric compositions according to claim 2, wherein the ammonium polyphosphate has a chemical structure of the type (NH4PO3)n" wherein n" is greater than 20.

8. Polymeric compositions according to claim 1 or claim 2, wherein the acid of phosphorus is selected from the group consisting of H3PO3 and H3 PO4.

9. Flame retardant polymeric compositions which upon contacting a flame, provide an intumescent char-forming crust, which are non-dripping and promote neither flame nor toxic fumes, comprising in 100 parts in weight of a thermoplastic polymer, from 4 to 40 parts in weight of a reaction product between an acid of phosphorus and a hydroxalkyl derivative of isocyanuric acid, said reaction product having a chemical structure of the type N - (R)n1 - O - P
in which R is an alkylene derivative, and n' is between 1 and 6, said reaction product including a plurality of nitrogen atoms interbonded through one or more carbon atoms, wherein P is trivalent phosphorus.

10. Process for producing flame retardant polymeric compositions which upon contacting the flame, provide an intumescent char-forming crust, which is non-dripping and promote neither flame nor toxic fumes, the process comprising the step of reacting an acid of phos-phorus with a hydroxyalkyl derivative of isocyanuric acid to pro-vide a reaction product from 5 to 40 parts in weight in 100 parts in weight of a thermoplastic polymer, said reaction product having a chemical structure of the type N - (R)n1 - O - P
in which R is an alkylene derivative, and n' is between 1 and 6, and wherein said reaction product includes a plurality of nitrogen atoms interbonded through one or more carbon atoms.