GB2053235A

GB2053235A - Flame retardant polyacrylonitrile

Info

Publication number: GB2053235A
Application number: GB8019624A
Authority: GB
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1979-06-19
Filing date: 1980-06-16
Publication date: 1981-02-04
Also published as: FR2459263A1; IT8048992A0; DE3022061A1; WO1980002844A1; GB2053235B

Abstract

Fire-proof compositions based on polyacrylonitriles, preferably in fibrilar form, and containing: (a) at least one organic compound, non-halogenated and not forming fibre, having in its molecule at least six atoms of carbon, not containing phosphore and not copolymerising with the polyacrylonitrile, (b) an oligomer halogenated polyphosphonate or (c) a bis-(2-oxo-1,3,2-dioxaphosphorinanyl) oxide, a bis-(2-thiono-1,3,2-dioxaphosphorinanyl) oxide, and/or a (2-oxo-1,3,2-dioxaphosphorinanyl)-(2'-thiono-1',3',2'-dioxaphosphorina nyl) oxide, or a mixture of compounds (a), (b) and (c).

Description

SPECIFICATION Flame retardant polyacrylonitrile This invention relates to flame retardant polyacrylonitrile, particularly in the form of textile fibres.

It is known to flameproof polyacrylonitrile by the incorporation of flame retardant additives including chloroalkyl polyphosphonates and bis-phosphoranyl oxides. These additives must however be used in large quantities in order to attain acceptable levels of flame retardancy, and the properties of the polyacrylonitrile may be adversely affected thereby.

It has now been found that the addition of organic halogen compounds to polyacrylonitrile containing oligomeric polyphosphonates and/or certain bisphosphoranyl oxides gives improved flame retardancy and allows the proportion of flame-retardant additives to be considerably reduced.

Accordingly, the present invention provides flame retardant polyacrylonitrile containing a) at least one phosphorus-free halogencontaining organic compound containing at least 6 carbon atoms, which is not copolymerised with the acrylonitrile, and is not itself a fibre-forming polymer, and either or both of b) a halogencontaining oligomeric polyphosphonate and c) a bis - (2 - oxo - 1,3,2 - - dioxaphosphorinanyl) oxide, a bis - (2 -thiono - 1,3,2 -dioxaphosphorinanyl) oxide or a 2 - oxo -1, 3, 2 - dioxaphosphorinanyl - 2' -thiono - 1,3,2 - dioxaphosphorinanyl oxide.

The term "polyacrylonitrile" is used herein to mean not only the homopolymer of acrylonitrile, but also copolymers of acrylonitrile with up to 50% by weight of other comonomers. Examples of such comonomers include unsaturated alcohols e.g. allyl alcohol, methylallyl alcohol, a - hydroxy - methacrylonitrile and allyloxyethanol; ethers e.g. vinyl methyl ether, allyl or vinyl ethers of aminoalcohols and allyl glycidyl ether; halides e.g. vinyl chloride, vinylidene chloride and ally chloride; amines e.g.

vinylpyridines, vinylquinolines, vinylpiperazine, vinylimidazole, 2-amino-4-vinylsulphonylanisole and and allyldimethylamine; amides e.g. acrylamide, N-substituted acrylamides, sulphonic acid group containing acrylic acid amines and allyl amides such as N-allyl nicotinamide; aldehydes e.g. methacrolein; ketones e.g. vinyl methyl ketone and a acetoxystyrene; acids e.g. acrylic, methacrylic and itaconic acids; acrylate esters e.g. methyl acrylate, methyl methacrylate, N-dimethylaminoethyl methacrylate, methyl a-acetaminoacrylate, methoxyethyl acrylate, methyl a-chloroacrylate and 3 chloro - 2 - butenylmethacrylate; vinyl esters e.g.

vinyl acetate and vinyl chloroacetate; allyl esters e.g.

nicotinic and isonicotinic allyl esters; and lactones e.g. diketene, a - methylene - p - propiolactone and a - methylene - y - butyrolactone.

Preferred copolymers are those capable of fibre formation. Such copolymers are well known, and are generally referred to as "polyacrylonitrile" when they contain at least 85% of acrylonitrile and as "modacrylics" when they contain 50-85% of acrylonitrile. The preferred copolymers are those derived from halogen-free comonomers; and preferably contain at least 85% acrylonitrile.

The halogen-containing organic component a) is present as an additive to the polymer and is not copolymerised with the acrylonitrile. As the compound must not evaporate readily from the PAN fibres during processing or afterwards, it should preferably have a molecular weight of at least 250.

Although the compound may be an oligomer or low polymer, it should not be a high polymer capable of fibre formation. Preferably the ratio of carbon atoms to halogen atoms in a) is between 6:1 and 1:1. The term "halogen" includes fluorine, chlorine, bromine and iodine, of which chlorine and bromine are preferred.

Examples of suitable compounds a) are halogenated phtalic acid derivatives e.g. tetrabromophthalic anhydride, tetrabromophthalimide and tetrab romophthalic esters, bicyclo L2, 2, 1] heptane derivatives, e.g. 5, 6 - dibromo - 2,3 - dicarboxylic acid N ethyl imide-bicyclo L2, 2, 1j heptane of formula

terephthalic acid esters e.g. bis - (2, 3 - dibromopropyl)terephthalate; halogenated carbonates e.g. 2, 2 - bis - (bromomethyl) - 3 - bromopropyl carbonate ortribromophenyl carbonate; halogenated isocyanurates e.g. tris - (dibromopropyl) isocyanurate of formula

halogenated diphenyl oxides e.g. decabromodiphenyl oxide; polymeric bromo compounds e.g. poly(tribromostyrene) or brominated polyphenylene ether; halogenated aromatic hydrocarbons e.g. hexabromobenzene, pentabromotoluene, tetrabromoxylene, pentabromoethylbenzene and hexakis - (bromomethyl) - benzene; halogenated aliphatic hydrocarbons e.g. hexabromocyclododecane, di(bromomethyl)dibromocyclohexane, decachloropentacyclodecane or chlorinated paraffins; halogenated optionally diethoxylated bisphenols e.g. tetrabromobisphenol-A, tetrabromobisphenol - A - diethoxylate and halogenated alkyl aryl ethers.

Preferably, however, component a) is a halogenated alkyl aryl ether of formula I

in which Hal is Cl or Br mis 0, 1 or2 and B is hydrogen, C1-4alkyl, Hal ora group

in whicn n is 0, 1 or 2 and A is a direct bond, a straight or branched chain C14

alkylene group, - CH - 0 -, - S -, or Such halogenated alkyl aryl esters are known, and are described for example in German Offenlegungsschrift 2 731 817.

A particularly preferred compound of formula I is 2,2 - bis -[4 - (2', 3' - dibromopropoxy) -3,5 - dib romophenylu - propane of formula 1a

The preferred oligomeric polyphosphonates of component b) are compounds of formula II

in which each R1 is independently hydrogen or Cl-4 alkyl, each R2 is independently C1-4 alkyl, or R1 and R2 together with the carbon atom to which they are attached form a cyclohexylidene group, D is a group

where Rg is hydrogen, C1-4 alkyl, -CH2CI or -CH2Br, p is a number from 2 to 100, which may bean average number and need not be integral, Yis-OH, -OR4 or

where R1 and R2 are as defined above and each R4 is independently C1 4alkyl, and Z is hydrogen, -R4, -P(OR4)2 or

where R4 is as defined above.

Such oligomeric polyphosphonates are known and are described for example in Belgian Patent No.

659 335 and in US Patents 3 760 037 and 3 836 507.

Preferred compounds of formula II are those in which R1 and R2 are methyl and D is

more preferably those in which Y is -OH and Z is hydrogen.

The preferred compounds of component c) are those of formula Ill

in which each X is independently oxygen or sulphur, each R is independently hydrogen, C1~4alkyl, -CH2CI, -CH2Br or phenyl, each R is independently hydrogen, C1~4alkyl, -CH2CI or-CH2Br, or Ri and Rii togetherwith the carbon atom to which they are attached form a cyclohexylidene, cyclohexenylidene or 3,4 - dibromocyclohexylidene ring, each R'ii and each R, independently are hydrogen orC1 4alkyl and each RY is independently hydrogen or methyl, provided that at least one of the substituents R', R'i, Riii, Riv and Rv isotherthan hydrogen, and that when on each phosphorus-containing ring, R and R are both -CH2Cl or CH2Br, or form a ring together with the carbon atom to which they are attached, then Riii, Rv and Rv on that ring are all hydrogen. Such bisphosphoranyl oxides are known and are disclosed forexampleiin British Patents 1 510381 and 1 510 382.

Preferred compounds of formula Ill are symmetrical, that is, the two phosphornus-contatning rings carrythe same substituents. PreferablyX = S. Particularly preferred compounds are those of formulae Illa- Illf below:

It is found that optimum flame-retardant properties are obtained when the ratio of halogen to phosphorus in the polymer lies within certain limits. In calculating this ratio, not only the added halogen in component a) is taken into account, but also the halogen in component b), the halogen, if any, in component c) (for example, in the compound Ille above) and also the halogen, if any, in any comonomer of acrylonitrile which is present in the polymer.The atomic ratio of halogen to phosphorus in the polymer is preferably between 5:2 and 25:1, more preferably between 3:1 and 20:1, most preferably between 5:1 and 15:1. The total halogen content of the polymer is preferably 1-16%, more preferably 3-15%, still more preferably 4-12% and most preferably 7 to 12% by weight calculated on the total weight of polymer.

When the polymer contains component a) and component b) only, the weight ratio of component a) to component b) is chosen to give the preferred halogen phosphorus ratio given above, and is preferablyfrom 1 :9to 19:1, more preferably from 1:1 to 9:1. When components a) and c) are present, the weight ratio of a)to c) is preferably 1:1 to 19:1, more preferably 7:1 to 19:1. If all three components a), b) and c) are present, then the weight ratio of a) to the sum of components b) and c) is preferably 1 :9to 9:1, more preferably 1:1 to 9:1, and the weight ratio of componentc)to component b) is preferably 1:19 to 1:1.

Preferably, the polymer contains either a) + b) or a) + b) + c); more preferably a) + b).

The invention also provides a process for the production of flame-retardant polyacrylonitrile fibres, The invention also provides a process for the production of flame-retardant polyacrylonitrile fibres, comprising the steps of making a solution or dispersion of component a)togetherwith component b) and/or component c) in a solution of polyacrylonitrile, and spinning fibres from the resulting polymer solution. PAN fibres may be spun from solution either by wet- or dry spinning processes. In wet spinning, PAN dissolved in a suitable solvent is spun into a precipitating bath, pulled through a wash bath and wound onto spools or further treated. Suitable solvents are for example dimethyl formamide, dimethyl acetamide, ethylene carbonate, dimethylsulphoxide or salt solutions of zinc chloride or sodium thiocyanate.

In the dry spinning process, the PAN solution is heated and extruded into a heated spinning shaft in which the evaporation of the solvent (usually dimethylformamide) is assisted by a current of hot air, nitrogen or steam.

The total weight of additives a) plus b) and/or c) in the PAN solution is preferably 5-30% more preferably 10-20% by weight based on the total composition. The invention further provides a composition comprising a mixture of components a) and b), a) and c) or a), b) and c), which may be added in one operation to the PAN solution before spinning. The mixture may also contain 2080% preferably 40-60% wt. of PAN, as a so-called master-batch composition.

The following Examples, in which all parts are by weight and all temperatures in degrees Centigrade, illustrate the invention.

Examples 1- 11 Table 1 gives examples of composition according to the invention, formed by mixing together the individual components.

Table 1 Parts by weight

Example Compound A Compound B Compound C1 Compound C2 No.

1 1 1 - 2 4 1 - 3 5 4 1 4 8 1 1 T 5 1 1 - 1 6 19 - 1 1 7 17 - 1 8 15 - - 1 9 13 - - 1 10 11 - 0.5 0.5 11 9 - 1 Compound A is the compound of formula la above Compound B is

where n = approx. 23 (average value) Compound C1 is the compound of formula Illa above Compound C2 is the compound of formula Illc above.

Example 12 100 Parts of a PAN powder (Leacryl 16 Type C, Montefibre) and 21.95 parts of the composition of Example 2 above are sprinkled into 400 parts dimethyl formamide and the mixture stirred for 60 minutes at 90-100"C. The solution is cooled to 50-60 and spun through a glass spinneret (40 holes of 140 ,um diameter) into a precipitation bath of a 50% dimethyl formamide/water mixture at 24 . The resulting fibres are stretched with a draw ratio of 1:6 in a hot (95 ) water bath, dried on a roller at 160 and knitted into a fabric of approx. 150 g/m2weight. The fabric is washed once at 60 in a domestic washing machine and finally tested for flame retardancy by the limiting oxygen index (LOI) test of Fenimore and Martin (Modern Plastics, November 1966) and by the vertical test according to DIN 53 906. Good results are obtained.

Examples 13-22 The compositions of Examples 1 and 3-11 are used in place of that of Example 2 in the process of Exam ple 12. PAN fabrics having good flame retardant properties are obtained.

Claims

1. Flame retardant polyacrylonitrile containing a) at least one phosphorus-free halogen-containing organic compound containing at least 6 carbon atoms, which is not copolymerised with the acrylonitrile, and is not itself a fibre-forming polymer, and either or both of b) a halogen-containing oligomeric polyphosphate and c) a bis - (2 - oxo - 1,3,2 - - dioxaphosphorinanyl ) oxide a bis - (2 -thiono - 1,3,2 - dioxaphos phorinanyl) oxide our a 2 - oxo - 1,3,2 - dioxaphosphorinanyl - 2' - thiono -1,3,2 - dioxaphosphorinanyl oxide.

2. Flame retardant polyacrylonitrile as claimed in Claim 1 in which component a) has a molecular weight of at least 250.

3. Flame retardant polyacrylonitrile as claimed in Claim 2 in which component a) is a halogenated alkyl aryl ether of formula I

in which Hat is Cl or Br mis 0,1 or 2 and B is hydrogen, C14alkyl, Hal or a group

in which n is 0,1 or 2 and A is a direct bond, a straight or branched chain C14

alkylene group, - CH - 0 -, - S -, or - S02.

4. Flame retardant polyacrylonitrile as claimed in Claim 3 in which component a) is the compound of formula 1,

5. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims in which component b) is a compound of formula II

in which each R1 is independently hydrogen or C14 alkyl, each R2 is independently Ct~4alkyl, or R1 and R2 together with the carbon atom to which they are attached form a cyclohexylidene group, D is a group

or #CH2#3 where R3 is hydrogen, C1-4alkyl, -CH2Cl or-CH2Br, P is a numberfrom 2to 100, which may be an average number and need not be integral, Y is -OH, -OR4 or

where R, and R2 are as defined above and each R4 is independently C1-4alkyl, and Z is hydrogen, -R4, -P(OR4)2 or

where R4 is as defined above.

6. Flame retardant polyacrylonitrile as claimed in Claim 5 in which component b) is a compound of formula II in which R, and R2 are methyl, D is

7. Flame retardant polyacrylonitrile as claimed in Claim 6 in which component b) is a compound of formula II in which Y is -OH and Z is hydrogen.

8. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims in which component c) is a compound of formula III

in which each X is independently oxygen or sulphur, each R is independently hydrogen, C1-4alkyl, -CH2CI, -CH2Br or phenyl, each R'i is independently hydrogen, C1-4alkyl, -CH2CI or-CH2Br, or Ri and Rii together with the carbon atom to which they are attached form a cyclohexylidene, cyclohexenylidene or 3,4 - dibromocyclohexylidene ring, each Riii and each Rv independently are hydrogen or C1~4alkyl and each Fl'V is independently hydrogen or methyl, provided that at least one of the substituents d, Fl", Rii, RlV and Rv is otherthan hydrogen, and that when on each phosphorus-containing ring, Ri and Rii are both WH2CI or CH2Br, or form a ring together with the carbon atom to which they are attached, then R Riv and Rv on that ring are all hydrogen.

9. Flame retardant polyacrylonitrile as claimed in Claim 8 in which component c) is a symmetrical compound of formula Ill in which X is sulphur.

10. Flame retardant polyacrylonitrile as claimed in Claim 9 in which component c) is selected from compounds of formulae Illa to Illf

11. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims in which the atomic ratio of halogen to phosphorus in the polymer lies between 5:2 and 25:1.

12. Flame retardant polyacrylonitrile as claimed in Claim 11 in which the atomic ratio of halogen to phosphorus in the polymer lies between 5:1 and 15:1.

13. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims in which the total halogen content of the polymer is from 1 -16% by weight.

14. Flame retardant polyacrylonitrile as claimed in Claim 13 in which the total halogen content of the polymer is from 7 to 12% by weight.

15. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims containing all three components a), b) and c).

16. Flame retardant polyacrylonitrile as claimed in Claim 16 in which the weight ratio of component a)to the sum of components b) and c) lies between 1:9 and 9:1 and the weight ratio of component c) to component b) lies between 1:19 and 1 :1.

17. Flame retardant polyacrylonitrile as claimed in any one of Claims 1 to 7 and 11 to 14 containing components a) and b) but not c).

18. Flame retardant polyacrylonitrile as claimed in Claim 17 in which the weight ratio of component a)to component b) lies between 1:9 and 19:1.

19. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims, in which the polyacrylonitrile is derived from halogen-free comonomers and contains at least 85% acrylonitrile.

20. Flame retardant polyacrylonitrile as claimed in any one of the preceding claims, in the form of textile fibres.

21. Flame retardant polyacrylonitrile fibres as described in any one of Examples 12-22.

22. A process for the production of flame retardant polyacrylonitrile fibres, comprising the steps of making a solution or dispersion of component a) together with component b) and/or component c) (ail as stated in Claim 1) in a solution of polyacrylonitrile, and spinning fibres from the resulting polymer solution.

23. A composition for flameproofing polyac rylonitrile comprising a mixture of components a) and b); a) and c) or a), b) and c) (all as stated in Claim 1).

24. A composition as claimed in Claim 23 con tain ing 20-80%. by weight polyacrylonitrile.

25. A composition as claimed in Claim 23 comprising a mixture of the compound of formula lo, stated in Claim 4, and the compound of formula

where n = approx. 23.

26. Acomposition forflameproofing polyacrylonitrile as described in any one of Examples 1-11.