CA1044854A - Flame retardant mixtures of chloroethyl phosphonate monomers and high boilers and polymers containing them - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention provides a flame retardant mixture containing between about one weight per cent and about 75 weight per cent of a monomer compound having the structure:

and between about 99 weight per cent and about 45 weight per cent of a high boiling phosphonate comprising predominantly a compound having the structure:

Description

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This invention relates to phosphorùs-containing flame retardants and to polymer compositions containing these retardants.
~ nited States Patent No. 3,027,349 describes a mixed phosphite-phosphonate polymeric material produced by isomerizing tris(2-chloroethyl) phosphite at tcmperatures greater than 180C. e~g. 180-300C. These materials can be used as flame retardants. These materials have a phosphite structure in the molecule.
We have now discovered flame retardant mixtures which have excellent properties. The flame retardant mixtures comprise 1 to 75 weight per cent of a compound having the structure:

.~ O
,;~ (ClCH2CH20)2 PCH2CH2Cl . . .
and 99 to 25 weight per cent of a high boiling phosphonate comprising predominantly a compound having the structure:

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''~ ClCH2CH201 OCH2CH2P(OCH2CH2Cl)2 CH2cH2cl Polymers, particularly rigid and flexible urethane foams, generally contain 2 to 30 weight per cent of the flame retardant mixture.
-` The flame retardant mixtures are produced by the thermal isomeri-zation of tris(2-chloroethyl)phosphite (TECP). The isomerization is carried out by slow addition of the phosphite to a product heel at a temperature below 180 C. (normally about 175C.). The major constituent of the product ~` is about 65 per cent, by Vapor Phase Chromatography CVPC), bis(2-chloroethyl)2-'~ chloroethyl phosphonate having the structure:

1l (ClCH2CH20)2 PCH2CH2Cl ,. ~ .

.~,, 10~4854 The remainder is high boiling phosphonate which comprises predomlnantly a compound having-the structure:

O O
ClCH2CH20PC~2CH2P(CH2CH2C )2 ~H2CH2Cl Evidence for this structure includes the presence of a ma~or peak in the VPC analysis with a retention time consistent with a structure in the dimer molecular weight range and the absence of significant amounts of titratable P (III) phosphorus in the product. This contrasts with the material described in U.S. Patent 3,027,349 which contains a si~nificant amount of phosphite which is titratable by the standard I2 method. The high boiling phosphonate may also contain small amounts of trimer and higher phosphonates similar to the above structure.
This mixture about 65 weight per cent monomeric phosphonate and, after stripping out low boiling by-products at a pressure of 15 - 25 mm Hg at about 150C., can be used directly as a flame retardant mixture.
This mixture can also be sub~ected to fractional distillation to separate monomer product from high boiling phosphonate, leaving a high boiling phosphonate containing 1-2 weight per cent of residual monomer. ~hese fractions can be blended to produce flame retardant mixtures in accordance with this invention containing varying proportions of monomer to high boiling phosphonates.
In order to produce the flame retardant mixtures of the present invention, the 65% monomer - 35Z high boiling phosphonate mixtures can be used as such or mixtures can be prepared by suitable blending of the monomer and the high boiling phosphonate to produce the desired mixture in accordance with the invention. Intermediate mixtures can be prepared by stripping off only part of the monomer. These mixture will contain from 1 to 75 weight per cent monomer, preferably from 2 to 65 weight per cent, and from 99 to 25, preferably from 98 to 35 weight per cent, high boiling phosphonate.
The invention will now be described with reference to preferred embodiments, making reference to the accompanying drawings in which:

-2-Figure 1 presents a curve showing the correlatlon between the per cent monomer in the flame retardant mixture and the burning rate for an unaged flexl-ble foam composition;
Fig. 2 presents the same correlation as in Fig. 1 fbr aged ~lexlble foam compositions;
Fig. 3 presents the correlation between the per cent flame retardants in flexible foam and the Limiting Oxygen Index (LOI) found and predicted, Flexible fire-retardant ~rethane foams were formulated as follows:
Table I
~ edients Parts by Welght T~luene diisocyanatea 42.2 Polyether triolb ~ 100.0 Water 3.2 Sllicone SurfactantC 1.0 Amine Catalystd 0.3 Stannous Octoate 0.3 Foaming Agente 3.0 Flame Retardant Agent 10.0 (a) Allled Chemical, Nacconate 80; (b) Union Carbide LG-56;
- (c) Union Carbide Y-6634; ~d) Houdry Dabco 33-LV; (e) DuPont R-ll (trade marks) The flame retardant agent was formulated from the monomeric and hlgh ; bolling phosphonate fractions described above to prepare flame retardants with the desired mDnomer content. These flame retardants were formulated in flexlbleurethane foams as indlcated abo~e, and tested in ASTM D-1692-68.

test (T~ble II). The samples with < 90% monomer content . gave essentially equivalent results and were clearly superior to the 90% monomer material (Table II and Figure 1).

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Samples of the foams used in Examples 1 - 7 were subjected to thermal aging at 250F. far 24 hours prior to testing in the ASTM D-1692-68 te~t (Table III). Foam with 65% monomer content flame retardant exhibited better flame retardancy than foam with 90%
monomer content flame retardant. Samples with <65% monomer content flame retardant had similar flame retardancy, all significantly better than foams for~ulated with flame retardant containing greater amounts of monomer.
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Fig. 1 is based upon the data set forth in Table II
and presents a curve showing the relationship between the weight per cent monomer in the flame retardant mixture of monomer and high boiling phosphona.te and the inches burned of the unaged flexible foam. From the curve, it will be noted that good ~lame retardancy is obta.ined with a flame reta.rdant mixture containing as much a.s 75 weight per cent mon~mer.
Fig. 2 is based upon the data set forth in Table III
and presents a curve showing a similar (to Fig. 1) relationship for the flexible foam a~ter aglng. It will be noted from the curve tha.t good fla.me retardancy is obtained with a ~lame re-ta.rdant mixture containing as much as 40 weight per cent mono-mer. At different loadings or with different ~ormulations the maximum monomer content that will afford good flame reta.rdancy will be expected to vary to some extent.

Flexible urethane foams were prepa.red~using a.
~ormulation similar to the formulation in Table I, aga.in using 10 parts by weight o~ ~lame retarda.nt. The flame ~ 20 retardants used were the 65~ monomer content phospho~a.te .` product of TCEP rearrangement and the 2~ monomer content phosphonate produced by removing monomer from the 65 monomer material. Foams conta.ining the 2~ monomeric phosphonate had significa.ntly better flame reta.rdancy after heat aging, as measured by Limiting Oxygen Index ; Test, ASTM-D-2863 and by the ASTM D-1692-68 test.

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_ 9 _ 4t~54 Flexible uretha.ne ~oams were prepared uslng a formulation similar to tha.t given in Table I, except that the flame retardant level was varied from 0 to 15 parts by weight. The flame retarda.nt was aga.in the 65~ monomeric phosphona.te product o~ TCEP re-arrangement. Flame reta.rdancy was measured by the LOI Test ASTM D-2863 be~ore and a.fter hea.t aging at 240F. for 24 hours and the weight loss ~n hea.t aging was measured (Ta.ble V). The loss of ~lame re-tardancy wa.s clearly less than predicted based on the weight loss (Ta.ble V a.nd Figure 3).

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~0~54 Fig 3 is based upon the data set forth in Table V
and presents curves showin~ the relationship between the LOI
and weight per cent of 65% monomer flame retardant mixture initially in flexible urethane. Curve A shows the LOI
actua.lly found for the flexible foam after aging. Curve B
shows the LOI predicted (B) for a f~am ha.ving the net amount of flame reta.rdant remaining after aging as compared with the LOI usually experienced with a foam c~ntaining that (net) amount of fla.me retardant in ~resh foam, corrected by the loss in flame retardancy experienced with this foam with no ~lame retardant after aging. It will be apparent from c~mparing the curves that a greater amount of flame retarda.ncy wa5 ex-: perienced than could be expected or predicted.

EXAMPLES 2~-29 -. 15 Rigid polyurethane foams containing the 65% mono-meric phosphona.te flame retarda.nt mentioned above exhibit . surprisingly better flame retardancy than foams formulated with corresponding amounts`of the simila.r material tris (2-chloroethyl) phosphate, as measured b~ weight loss following corner ignition of 2" x 8.5" x l/2" sa.mples.
The samples a.re placed at a 45 a.ngle rela.tive to the ignition source, an Anderson-Forrester micro burner (Table VI).

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TABLE VIl Examples 25 26 27 28 29 Flame Retardant2 _ A A B B
PBW flame retardant 0 5 10 5 10 ~ Wt. loss (45 angle test) 78 21 12 76 30 1450 angle ~lame retardancy tests ~or rigid polyuretha.ne foams 2A - 65% monomeric content phosphonate mentioned above B - tris (2-chloroethyl) phosphate . EXAMPLES 30-43 Samples of flexible polyurethane foa.m formulated with the 65% monomeric phosphonate mentioned above, like-wise exhibit better flame retardancy and retention than similar foams formulated with the similar flame retar-. dent tris (2-chloroethyl) phospha.te (~able VII.).

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1~)44~4 In the foregoing Exa~ples 25 throu~h 43, the tris ~2-chloroethyl~ phosphate used has ~ structure similar to that of the bis (2-chloroethyl~ 2-chloroethyl phosphonate.
Thus, both could ~e expected to behave similarly as flame retardants. Surprisingly, the phosphonate ~as found to be more effective.

The 65% monomeric phosp~onate is an effective flame retardant in a broad range of plastic resins as measured by the Limiting Oxygen Index ASTM D-2863 (Table VIII).

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; , , ,. ' ' ' ~5)448~4 The flame retardant mixtures of this invention are effective at flame retardant c~ncentrations in polymers, including, by way of non-limiting examples, rigid poly-urethanes and flexibl.e polyurethanes, polyethylene, tere-phthalate, polycarboxyamide, polyacrylonitrile, acetate ra.yon, polystyrene and other styrene polymers (e.g., ABS).
They will a.lso be effective in combinations with polymeric materials such as cotton, cellulose, paper and silk; cel-lulose esters and ethers such as cellulose aceta.te butyra.te and ethyl cellulose; polyvinyl chloride; polymethyl meth-acryla.te a.nd other acrylates; nylons; polyolefins such as polyethylene and polypropylene; phenol-aldehyde resins;
alkyd resins, urea. resins, epoxy resins; linear and cross-linked polyester, and ma.leic anhydride heteropolymers.
; 15 Flame retardant concentrations can vary dependent upon the polymer used. In genera.l, they will be 2 to 30 per cent, preferably 4 to 16 per cent, based upon the weight of the t.otal composition.
The flame reta.rdant mixtures can be incorpora.ted into the polymer during the polymerization step or by a.dmixing with the p~lymer prior to or during milling, extrusion, spinning, foaming, pressing or other conventional opera.tions for forming or applying the polymeric end-product.
The physical form of the flame reta.rda.nted composition can va.ry widely. While rigid and flexible polyuretha.ne foams ;~ are of ma.jor interest, fibers, films, coa.tings, sheets, rods, boards, and the like ca.n be used.

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Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be res~rted to, without departing from the spirit and scope of this invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

--l8--

Claims (14)

WHAT IS CLAIMED IS:

1. A flame retardant mixture containing between about one weight per cent and about 75 weight per cent of a monomer compound having the structure:

and between about 99 weight per cent and about 25 weight per cent of a high boiling phosphonate comprising predominantly a compound having the structure:

2. The flame retardant mixture of Claim 1, wherein the amount of said monomer is between about 2 weight per cent and about 65 weight per cent and the amount of said high boiling phosphonate is between about 98 weight per cent and about 35 weight per cent.

3. The flame retardant mixture of Claim 1, wherein the amount of said monomer is about 65 weight per cent and the amount of said high boiling phosphonate is about 35 weight per cent.

4. The flame retardant mixture of Claim 1, wherein the amount of said monomer is about 2 weight per cent and the amount of said high boiling phosphonate is about 98 weight per cent.

5. A polymer composition containing a flame re-tardant amount of the flame retardant mixture of Claim 1.

6. The polymer composition of Claim 5, wherein the flame retardant mixture is that defined in Claim 2.

7. The polymer composition of Claim 5, wherein the amount of said monomer in said flame retardant mixture is about 65 weight per cent, and the amount of said high boiling phosphonate is about 35 weight per cent.

8. The polymer composition of Claim 5, wherein the amount of said monomer in said flame retardant mixture is about 2 weight per cent, and the amount of said high boiling phosphonate is about 98 weight per cent.

9. The polymer composition of Claim 5, wherein the polymer is rigid urethane foam.

10. The polymer composition of Claim 7, wherein the polymer is rigid urethane foam.

11. The polymer composition of Claim 8, wherein the polymer is rigid urethane foam.

12. The polymer composition of Claim 5, wherein the polymer is flexible urethane foam.

13. The polymer composition of claim 7, wherein the polymer is flexible urethane foam.

14. The polymer composition of Claim 8, wherein the polymer is flexible urethane foam.