US3505285A - Stabilised polyamides containing a copper salt and a phosphine - Google Patents

Description

United States Patent US. Cl. 26045.75 4 Claims ABSTRACT OF THE DISCLOSURE A thermally stabilised polyamide comprising a high' molecular weight polyamide and as a stabilising agent a combination of copper salt and a phosphine and optionally an inorganic or organic salt of hydriodic acid.

This invention relates to stabilised polyamides using copper compounds as stabilisers.

Mouldings of polyamdes obtained by polymerising diamines with dicarboxylic acids or from aminocarboxylic acids or their lactarns; for example filaments, bristles or films, are deteriorated by the action of air and oxygen, particularly at elevated temperatures, to such an extent that their relative viscosity decreases whilst their strength and elasticity deteriorate. At the same time, the polyamide becomes progressively browner in colour.

It is known that polyamides can be protected against deterioration by the action of air and oxygen at elevated temperatures by the addition of stabilisers. The following compounds, for example, have already been used as stabilisers: manganese salts of inorganic or organic acids; copper salts of inorganic or organic acids; derivatives of the oxyacids of phosphorus; aromatic amines and phenols. Combinations of these groups of compounds with one another or with compounds Whch, on their own, have no stabilising action, such as alkali metal halides, alkaline earth metal halides, iodine and arylsulphonic acids, have also been used to advantage.

The known stabilisers, however, have the disadvantage either that their stabilising action is too weak, as is the case, for example, with manganese salts, phosphorus compounds and phenols, or the disadvantage that they cause discolouration, particularly when they are added to the polyamide-forming starting mixture before polymerisation, as is the case for example with copper salts, or that they are sensitive to light and, over a period of time, discolour the polyamide, as is the case for example with aromatic amines and phenols.

It has now been found that polyamides can be stabilised without the aforementioned disadvantages by using, as the stabiliser, a combination of (a) a salt of monovalent or bivalent copper with an inorganic or organic acid, and (b) aphosphine.

A further object of this invention is to combine the stabilising mixture consisting of a copper salt and a phosphine with an inorganic or organic salt of hydriodic acid.

The more difficulty volatile compounds from the triaryl-, trialkylor tri-(aryl-alkyD-phosphine series are preferably used in accordance with the invention as the phosphines. Examples of such phosphine are triphenyl phosphine, tris-(dimethylaminophenyl)-phosphine, tritolyl phosphine, phenyldimethyl phosphine, dimethylarninophenyl-dimethyl phosphine, naphthyl diethyl phosphine, tributyl phosphine, tripentyl phosphine, trioctyl phosphine,

3,505,285 Patented Apr. 7, 1970 ICC tris-(hydroxy-ethyl)-phosphine and tricyclopentyl-phosphine.

Preferred copper salts are the cupric and cuprous salts of hydrohalic acids and hydrocyanic acid, and the copper salts of aliphatic carboxylic acids.

Examples of suitable copper salts are cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cupric chloride, cupric acetate and cupric stearate.

The copper salts are preferably added in such a quantity that the polyamide contains 0.0001 to 0.1% by weight, most preferably 0.001 to 0.02% by weight, of copper. The phosphorus compounds are preferably added in such a quantity that the polyamide contains 0.001 to 0.1% by weight, most preferably 0.001 to 0.05% by weight, of phosphorus.

Example of suitable inorganic or organic salts of hydriodic acids are:

(1) Ammonium iodide, sodium iodide, potassium iodide, calcium iodide, magnesium iodide, zinc iodide or cadmium iodide.

(2) Hydriodides of primary amines, such as hexadecylamine hydriodide; hexamethylene diamine dihydriodide and cyclohexylamine hydriodide.

(3) Hydriodides of secondary amines, such as N-ethylbenzylamine hydriodide; piperidine hydriodide and N- methyloctadecylamine hydriodide.

(4) Hydriodides of tertiary amines, such as N,N- dimethylbenzene-amine hydriodide; N,N,N-triethanolaminehydriodide; pyridine hydriodide; trioctadecylaminehydriodide and N,N-dimethyldodecylamine hydriodide.

(5) Iodides of quaternary ammonium compounds, such as N-benzyl-N,N,N-trimethylammonium iodide; N-ethyl- N-benzyl-N,N-diethylammonium iodide; N-dodecyl-N,N, N-triethyl-ammonium iodide and N,N,N,N',N,N-hexamethyl-N,N-ethylene-bis-ammonium iodide.

(6) Hydriodides of aminocarboxylic acid esters and amides, such as N,N-dimethyl-6-aminocaproic acidmorpholide hydriodide; N,N dimethyl 6 aminocaproic acid dodecylamide hydriodide; N-methyl-N-cyclohexyl-6- aminocaproic acid ethyl ester hydriodide and N,N-dimethyl-1l-aminoundec-anic acid anilaide hydriodide.

(7) Iodides of carbamylamrnonium compounds, such as N- (N-dodecylcarbamylpentyl) N,N,N trimethylammonium iodide and N-(N'-3,4-dichlorophenylcarbamylpentyl) -N,N,N-trimethylammonium iodide.

The inorganic or organic salts of hydriodic acid are preferably added in such quantity that the polyamide contains 0.001 to 5% by weight, most preferably 0.01 to 1.0% by weight, of iodine.

The combinations according to the invention of copper salts and phosphorus compounds can be either mixtures of the components, or stable, crystallised addition compounds of phosphines and substances correspond ing to the formula CuX, in which X represents chlorine, bromine, iodine or cyanogen. Example of these addition compounds which can be obtained from the components, optionally at elevated temperature, are CuC1 2 triphenyl phosphine, CuBr 2 triphenyl phosphine, CuI tri-nbutylphosphine, CuI .tri-n-pentylphosphine, Cul X 2 triphenyl phosphine and CuCNXtriphenyl phosphine.

The stabiliser combinations according to the invention may be added to the polyamide-forming starting mixture before polymerisation, after which polymerisation may be carried out either continuously or in batches, as known per se, Without there being any discolouration of the polyamide melt.

It is also possible, however, to mix the stabilisers according to the invention with the polyamide melt, either during or after polymerisation, in which case known mixing units, such as extruders or kneaders, may be used.

In addition to the stabilisers according to the invention, the polyamides may also contain the usual additives such as pigments, dyes, light stabilisers, fillers such as glass fibres, lubricants, mould-release agents and crystallisation activators.

The polyamides stabilised in accordance with the invention against, in particular, damage by oxidation at elevated temperatures, are eminently suitable for the production of industrial silk for fishing nets, drive belts, conveyor belts, tyre cord and mouldings exposed to thermal stressing in the presence of air or oxygen.

Broadly speaking, the advantages set out below can be obtained by using copper compounds in combination with phosphines, optionally together with inorganic or organic salts of hydriodic acid. These advantages can be explained by the chemical resistance of the phosphines to hydrolysing or decomposing agents, and by the fact that secondary reactions involving the products of hydrolysis or decomposition are avoided.

No discoloured products are formed in cases where addition precedes polymerisation and where screw extruders are used for mixing. The use of screw extruders is not accompanied by the formation of partly crosslinked products (as is the case, for example, when aliphatic or aromatic esters of phosphoric or phosphorous acid are used, cf. comparison Example 4), or by corrosion (as in the case, for example, when halides of phosphoric or phosphorous acids are used). In addition, there is no additional chain-terminating effect where addition precedes polymerisation (as is the case, for example, with phosphoric or phosphorous acids or hydrolysable derivatives thereof).

The following examples illustrate more specifically the invention.

EXAMPLE 1 A mixture of 1.1 kg. of caprolactam, 35 g. of aminocaproic acid and 0.79 g. of CuCI 2 triphenyl phosphine (corresponding to 0.008% by weight of copper and 0.008% by weight of phosphorus in the end product), is polycondensed in the usual way in an auto clave at a temperature of 270 C. The resulting polyamide is then spun into a filament, chapped into granular form, freed from monomeric components by boiling with water and then dried. The resulting product is completely colourless and has a relative viscosity of 3.12 (measured on a 1% by Weight solution in m-cresol). In order to test the stability of the product to atmospheric oxidation, it is stored at 150 C. in a drying cabinet to which air has free access. After 144 hours, its relative viscosity is 3.46, after 500 hours it is 3.16 and after 1000 hours it is 2.96.

In the case of a comparison product of identical rela tive viscosity in which no stabiliser was present, the relative viscosity dropped under the same conditions to 2.61 after 144 hours, to 2.36 after 500 hours and to 2.21 after 1000 hours. In addition, the comparison product became much darker brown in colour considerably more quickly.

EXAMPLE 2 As in Example 1, a polyamide with a relative viscosity of 3.18 is prepared from 0.30 g. of Cu(II)Cl 2I-l O (corresponding to 0.011% by weight of copper in the end product) and 0.52 g. of tripheuyl phosphine (corresponding to 0.006% by weight of phosphorus in the end product). The product is completely colourless. After it has been stored at 150 C. in a drying cabinet to which air has free access, its relative viscosity is 3.48 after 144 hours, 3.09 after 500 hours and 2.94 after 1000 hours. A polyamide prepared under identical conditions, except that only 0.30 g. of Cu(II)Cl 2H O are added, is greenish in colour.

EXAMPLE 3 2 kg. of polycaprolactam with a relative viscosity of 3.15 are fused by means of a conventional screw extruder EXAMPLE 4 As in Example 3, a polyamide with a relative viscosity of 3.01 is prepared from 0.35 g. of Cu(II)-acetate H O (corresponding to 0.006% by weight of copper) and 0.44 g. of diphenyl ethyl phosphine (corresponding to 0.003% phosphorus). The product is completely colourless. After it has been stored at C in a drying cabinet to which air has free access, its relative viscosity is 3.24 after 144 hours, 3.05 after 500 hours and 2.92 after 1000 hours. A polyamide prepared under identical conditions, except that only 0.35 g. to Cu(-II)-acetate were added, is slightly greyish-green in colour.

Comparison tests demonstrating the technical advance of the combination of copper compounds with phosphines over combinations with other phosphines, are set out in the following:

(a) A mixture of 1.1 kg. of caprolactam, 35 g. of aminocaproic acid and 0.91 g. of Cu(I)-Cl 2 tripheuyl phosphite (corresponding to 0.008% by weight of copper and 0.009% by weight of phosphorus in the end product) is polycondensed in the usual way in an autoclave at a temperature of 270 C. The resulting polyamide is then spun into a filament, chopped into granular form, freed from monomeric components by boiling with water and then dried. The resulting product is deep blue-grey in colour.

(b) As in comparison example (a), a deep blue-grey coloured polyamide is obtained from 0.50 g. of Cu(I)-I- triisopropyl phosphite (corresponding to 0.008% by weight of copper and 0.004% by weight of phosphorus in the end product).

(c) As in comparison example (a), a deep-blue-grey coloured polyamide is obtained from 0.32 g. of Ou(II)- Cl .2H O (corresponding to 0.012% by weight of copper in the end product) and 1.24 g. of trinonylphenyl phos phite (corresponding to 0.006% by weight of phosphorus in the end product).

((1) 2 kg. of colourless polycaprolactam with a relative viscosity of 3.15 are fused by means of a conventional screw extruder in which they are homogeneously mixed with 1.44 g. of Cu(I)Cl-triphenyl phosphite (corresponding to 0.011% by weight of copper and 0.0055% by weight of phosphorus). The product is then spun into a filament, chopped into granular form and dried. It is reddish-brown in colour and has a relative viscosity of 3.38.

Triphenyl phosphine on its own does not have any stabilising effect on polyamides. This is demonstrated by the following comparison test:

2 kg. of polycaprolactam with a relative viscosity of 3.11 are fused by means of a conventional screw extruder in which they are mixed with 10 g. of triphenyl phosphine (corresponding to 0.059% by weight of phosphorus). The polyamide is then spun into a filament, chopped into granular form and dried. It is colourless and has a relative viscosity of 3.02. After it has been stored at 150 C. in a drying cabinet to which air has free access, its relative viscosity drops to 2.65 after 144 hours, to 2.48 after 500 hours and to 2.24 after 1000 hours.

EXAMPLE 5 1 kg. of a conventionally prepared colourless polycaprolactam with a relative viscosity of 3.12 (measured on a 1% by weight solution in m-cresol), is fused by means of a conventional screw extruder in which it is homogeneously mixed "with various stabilisers. The stabilised polycaprolactam is spun itno a filament of approx. 3 mm. diameter, chopped into granular form and dried. The granulate is then stored at 150 C. in a drying cabinet to which air has free access, and its relative viscosity measured after 144, 500 and 1000 hours.

ondary amine, a hydroiodide of a tertiary amine, an iodide of a quaternary ammonium compound, a hydroiodide of an amino carboxylic acid ester, 21 hydroiodide of an amino carboxylic acid amide, and an iodide of a carbamyl ammonium compound, said copper salt being present in such 5 The test results are Set out In Table a quantity that the polyamide contains 0.0001 to 0.1% by EXAMPLE 6 Weight of copper, said phosphme being present in such A mixture of 1.0 kg. of caprolactam, 35 g. of amino- 3 l g tlfiat i g il z to 9 caprorc acid and the stabllisers set out 1n Table II, 18 poly- Welg t P osp orus sa t o y acld belng condensed in the usual Way in an autoclave at a tempera 10 present in such a quantity that the polyamlde contalns ture of 270 C. The colour of the resulting polyamides 1s O-OOI t y Welght of lodlneshown in Table II. 3. The thermally stabilised polyamide of claim 2,

TABLE I Relative viscosity Percent Percent Percent Colour after- I in the Cu in P in the of the polythe polypolypoly- After 144 500 1,000 No. Iodide g amide Cu-eompound amide amide amide mixing hours hours hours 0. 38 011(1) Cl-1 triphenyl 0. 64 0. 011 0. 0055 Colour- 2. 98 4. 09 3. 84 3. 60

phosphine. less. 0.17 Cu(I)-I-2 triphenyl 1.26 0.011 0. 011 do.. 3. 12 4.17 3.89 3.66

phosphine. 0. do 1. 26 0. 011 0. 011 do 3. 08 3. 71 3. 55 3. 0.76 Cu(I)CN- triphenyl 1.20 0.11 0.011 do 3.03 4.40 4.21 3.75

phosphine. 0.38 C11(I)Br-1 triphenyl 0.54 0.0085 0.004 d0 3.06 4.04 3.70 3.35

phosphine. 6 N,N-dimethyl-dodecylamine l. 0. 056 Cu(I)-I-2 triphenyl 1. 26 0. 011 0. 011 do 3. 10 3. 92 3. 56 3. 20

hydroiodide. phosphine. 7 N,N-dimethyl-benzylamine 1. 16 0. 056 do 1. 26 0. 011 0. 011 do 3. 05 3. 86 3. 3. 16

hydro-iodide. 8 N-dodecyl-N,N,N-trimethyl- 0. 63 0. 022 do 1. 26 0. 011 0. 011 do. 3. 05 3. 64 3. 25 2. 97

ammonium iodide. 9 "do 1. 57 0. 056 .do 1. 26 0. 011 0. 011 do 3. 05 3. 81 3. 48 3. 12 10 N-ethyl-N-benzyl-N,N- 1.28 0.056 .....(10 1.26 0.011 0.011 do 3.06 3.82 3.55 3,38

dimethylammom'nm iodide. 11 N,N-dimethyl-6-amino- 2. 01 0. 056 do 1. 26 0. 011 0. 011 do. 3. 05 3. 86 3. 72 3. 25

caproic acid dodecyl amide hydro-iodide. 12 N-(N-3,4diehlorophenyl 0. 79 0 022 dO 1 26 0. 011 0. 011 do. 3. 08 3. 65 3. 29 3. 06

carbamyl-pentyl)N,N,N- trimethyl-ammonium 13 d0 1. 26 0.011 0.011 do 3.12 3.43 3.12 2.00 14 -410-.- 3. O0 2. 73 2. 36 2. 21

TABLE II Percent I Percent Cu Percent P Colour Test in the in t e in the of the No. Iodide G. polyamlde 011-compound G. polyamide polyamide polyamide 1 KI 5.0 07 38 Cu(I)C1-1tripheny1phosphine. 0.64 0. 011 0.0055 colourless. 2 KI 2. 0 0.17 Cu(I)I-2 triphenyl phosphine 1.26 0.011 0.011 Do. 3 KI..- 1.0 0.10 do 1.26 0. 011 0. 011 Do. 10.0 0.76 Cu(I)CN-2 triphenylphosp 1.10 0.011 0.011 Do. KI 5. 0 0.38 Cu(I)Br-1 triphenyl phosphine. 0. 54 0.0085 0.004 Do. ,N-dimethyLdodecylamine- 1. 50 0. 056 Cu(I)I-2 triphenyl phosphine 1. 26 0. 011 0. 011 D0.

hydroiodide. 7 N-dodecyl-N,N,N-trimethy1 1.57 0.056 d0 1.26 0.011 0011 Do,

ammonium hydroiodide. g N,N41imethyl-fi-amino-caproie 2.01 0.056 .d0 1.26 0.011 0,011 Do.

acid dodecylaminehydroiodide. 9 KI 5.0 0.38 Cu( I) 01521120 triphenyl 0. 27 0.011 0,0 5 Do,

phosphine. 0. 42 10 KI 5.0 0- 8 C11( z-2Hz0 0.27 0.011 Greenish.

What we claim is:

1. A thermally stabilised polyamide comprising a high molecular weight polyamide and as stabilising agents admixed therewith (a) a copper salt selected from the group consisting of a chloride, bromide, iodide, cyanide, and a salt of an aliphatic carboxylic acid of monovalent and bivalent copper, and (b) a tertiary phosphine, said copper salt being present in such a quantity that the polyamide contains 0.0001 to 0.1% by weight of copper, said phosphine being present in such a quantity that the polyamide contains 0.001 to 0.1% by weight of phosphorus.

2. A thermally stabilised polyamide comprising a high molecular weight polyamide and as stabilising agents admixed therewith (a) a copper salt selected from the group consisting of a chloride, bromide, iodide, cyanide, and a salt of an aliphatic carboxylic acid of monovalent and bivalent copper, (b) a phosphine, and (c) a salt of hydroiodic acid selected from the group consisting of ammonium iodide, sodium iodide, potassium iodide, calcium iodide, magnesium iodide, zinc iodide, cadmium iodide, 21 hydroiodide of a primary amine, a hydroiodide of a sec- 5 wherein said salt of hydriodic acid is potassium iodide.

4. The thermally stabilised polyamide of claim 2, wherin said salt of hydriodic acid is N,N-dimethyldodecy1- amine hydroiodide.

References Cited UNITED STATES PATENTS DONALD E. CZAJA, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R.