GB2253399A - Stabilized polymer composition - Google Patents

Abstract

A stabilized copolymer composition comprises an alternating copolymer of carbon monoxide and at least one ethylenically unsaturated compound, and at least a stabilizing quantity of a diarylamine, of which at least ono of the aryl groups carries an alkoxy substituent, e.g. 3-methoxydiphenylamine or 4,4'-dimethoxydiphenylamine. Preferred polymers are a copolymer of ethylene and carbon monoxide or a terpolymer of ethylene, propylene and carbon monoxide. The stabilizers improve both the melt-stability and long-life stability of the polymers.

Description

STABILIZED POLYMER COMPOSITIONS.

The present invention relates to stabilized polymer compositions, and more in particular to such stabilized compositions based on copolymers of carbon monoxide and at least one ethylenically unsaturated compound.

The general class of polymers of carbon monoxide and one or more ethylenically unsaturated compounds has been known for some years. U.S. Patent Specification No. 2,495,286, describes the production of such polymers of relatively low carbon monoxide content in the presence of free radical catalysts such as benzoyl peroxide. British Patent 1,081,304 discloses such polymers of higher carbon monoxide content produced in the presence of alkylphosphine complexes of palladium as catalyst.

More recently, the class of linear alternating polymers of carbon monoxide and olefinically unsaturated compound, now known as polyketones, has become of greater interest, in part because of improved methods of production. Such methods are shown by European Patent Applications Nos. 0 181 014 and 0 121 965. The disclosed processes employ, inter alia, a compound of a Group VIII metal such as palladium, an anion of a non-hydrohalogenic acid having a pKa below 2 and a bidentate ligand of phosphorus.

Whilst these polymers have attractive physical and mechanical properties such as yield stress, tensile strength, impact strength and flexural modulus, their processing or melt stability and long-life or end-use stability leave room for improvement.

Applicants have found that a very large number of commercial thermostabilizers that perform well in polyamides, polyolefins, polyacrylates, polystyrenes and various other commodity thermoplastics and engineering thermoplastics fail to achieve adequate thermostabilization of said linear alternating copolymers of carbon monoxide and an olefinically unsaturated compound.

Moreover when compounds were available which did raise the thermostability of said alternating copolymers, the improvement was generally observed to occur with only one of the thermostability aspects, i.e. only with the melt-stability or only with the long-life stability. With a number of such thermostabilizers it was however observed that next to an improvement of one of the hereinbefore mentioned stability aspects, the presence of such a stabilizer was found to be detrimental for the other thermostability aspect. It is therefore surprising to find that the use of a selected class of diarylamines as thermostabilizer for the hereinbefore mentioned alternating copolymers had a beneficial influence on both mentioned stability aspects.

The present invention provides therefore stabilized copolymers compositions comprising an alternating copolymer of carbon monoxide and at least one ethylenically unsaturated compound, and at least a stabilizing quantity of a diphenylamine of which at least one of the phenyl groups carries at least an alkoxy substituent.

The alkoxy substituents of which at least one is present in the diphenylamines as described hereinbefore are preferably low molecular weight alkoxy groups such as for example Cl6 alkoxy groups, and more preferably methoxy groups. The alkoxy substituents may occupy any position on the phenyl ring, however phenyl groups having the alkoxy substituent in the 3 or 4 position are preferred. In addition to compositions containing diphenylamines wherein only one of the phenyl groups carries an alkoxy substituent, compositions containing diphenylamines wherein both phenyl groups are alkoxy substituted, are also part of the present invention. With the latter class of amines, it is preferred that both phenyl groups carry the same alkoxy substituent and moreover in the same position on the ring, such as for example 4,4'-dimethoxydiphenylamine.

In addition to the hereinbefore mentioned alkoxy substituents, the phenyl groups of the diphenylamines may conveniently also carry other substituents such as for example lower alkyl groups, such as C14 alkyl groups.

In the context of the present invention the term "stabilizing quantity" refers to a quantity of a compound as mentioned hereinbefore which is sufficient to have a positive effect on both the melt-stability as well as on the long-life stability. Such quantities will comprise a minor part of the ultimate composition and will generally be in the range of from 0.03 to 5.0 %m (mass) on polymer.

The polymers from which the compositions of the invention are produced are linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated compound. Suitable ethylenically unsaturated compounds have up to 20 carbon atoms inclusive, preferably up to 10 carbon atoms inclusive and include wholly aliphatic hydrocarbons such as ethylene and other a-olefins including propylene, butene-l, octene-l and dodecene-l; arylaliphatic compounds containing an aryl substituent on an otherwise aliphatic molecule, particularly an aryl substituent on a carbon atom of the ethylenic unsaturation, such as styrene, p-methylstyrene, m-methylstyrene and p-ethylstyrene; as well as unsaturated compounds containing hetero atoms such as 0, N, P and halogen, and exemplified by compounds such as methyl acrylate, methyl methacrylate, vinyl acetate, undecanoic acid, 6-chlorohexene-l, N-vinylpyrrolidone and the diethylester of vinyl-phosphonic acid. Preferred polymers are copolymers of carbon monoxide and ethylene or terpolymers of carbon monoxide, ethylene and an aliphatic a-olefin of 3 or more carbon atoms, particularly propylene.

The physical properties of the polymer will be determined in part by the molecular weight and by whether the polymer is a copolymer or a terpolymer. Typical melting points are from 175 OC to 300 OC, more typically from about 210 OC to 280 OC.

The additive can be added to the copolymer by conventional methods suitable for producing an intimate mixture of the copolymer and the additive, without unduly degrading the copolymer or the additive. Such methods include dry blending of the additive and the copolymer in the finely divided form followed by hot pressing, coextrusion of the copolymer and the additive to thereby produce a stabilized composition as an extrudate, or by intimately mixing in a mixer or blender employing high shear.

The polymer composition may incorporate, in addition to said polymer and thermostabilizer, other compounds which do not detract from the stabilized character of the composition.

Examples of such compounds are plasticizers, mould release agents, antioxidants, U.V. stabilizers, pigments, dyes and reinforcements such as inorganic and organic fibrous materials, which may be added by blending or other conventional methods, together with or separate from the thermostabilizers.

The thermostabilized compositions may be processed by injection moulding, pressure forming or other conventional methods.

They are characterised by properties of flexibility and strength in addition to thermostability and are useful in a variety of applications, particularly where exposure to elevated temperature is likely to be encountered.

The invention will be further illustrated by the following example.

Example The following compounds were tested as stabilizer.

A: 3 -methoxydiphenylamine, ex Aldrich.

B: 4, 4'-dimethoxydiphenylamine, ex Alfa.

C: 2,4 -dinitrodiphenylamine, ex Aldrich.

D: 2,2'-dipyridylamine, ex Janssen.

Stabilizers A and B are compounds of the invention, while compounds C-D were included for comparison. The experiments were conducted with a CO/ethylene/propylene copolymer (I), having a limiting viscosity number (LVN) of 1.86 dl/g, a melting temperature of 221 OC and containing 0.5 %m of 1,3,5-trimethyl2,4,6-tris(3,5-ditertiarybutyl-4-hydroxybenzyl)benzene (Irganox 1330, Trade Mark), or with a similar copolymer (11), having a LVN-l.80 dl/g, a melting temperature of 222 OC and containing a mixture of two hindered phenols, i.e. 0.2 %m of 3,5-ditertiarybutyl-4-hydroxyphenylpropionic acid, n-octadecyl ester (Irganox 1076, Trade Mark) and 0.3 m of 1,3,5-trimethyl 2,4,6-tris(3,5-ditertiarybutyl-4-hydroxybenzyl)benzene (Irganox 1330, Trade Mark).

The compostions for testing were prepared by dry blending the relevant stabilizer, in an amount corresponding with 0.05, 0.2 or 0.8 %m on composition, with the powdered copolymer, followed by homogenizing the blend in a Berstorff 25x23 D twinscrew extruder having a temperature setting of 220, 230, 230, 230 and 240 OC, a screw speed of 170 RPM and a pressure of 2 bar. The extruder strands, which had a diameter of 1.5 mm, were used as starting material for determining the melt viscosity characteristics, as well for the oven ageing tests.For the latter a large number of samples of extruder strand were placed in a forced air circulation oven at 120 and 140 OC. At regular intervals 4 samples were taken from the oven and allowed to condition at ambient temperature (23 OC), before being bent to a 180-degree angle over a 1.0 mm cylindrical mandrel. The appearance of cracks was recorded as brittleness, and the time in hours to reach this, as a measure for the thermostability.

The melt stability was determined by subjecting said extrudate to a rheological evaluation using a parallel plate Rheometrics apparatus at 275 OC, a frequency of 1 radial/sec and a strain rate of 20 %. Measured were the viscosity increase over the first 10 minutes (dn/dt) and the cross over time (COT) being the time required for the loss factor to reach a value 1, (a longer time being an indication of a higher thermostability).

The results of the melt stability testing and of the oven ageing experiments are given in Table I and II respectively, which tables also include data obtained with the copolymer not containing one of the compounds A-D.

From the data provided it can be seen that of the stabilizers tested, the alkoxy-substituted diphenylamines are indeed the only compounds which have a positive effect on both the melt-stability and the long-life stability of the alternating copolymers.

Table I Melt stability Stabilizer COT (min) dn/dt (Pa.s/min) Type / conc. % 0 0.05 0.2 0.8 0 0.05 0.2 0.8 A 18 19 19 20 390 380 380 340 B 16 16 16 16 390** 390 375 320 C 21* 10 7 - 330* 620 1100 D 15 * 15 15 12 390** 420 370 415 * Copolymer I ** Copolymer II Table II Oven ageing (h) Stabilizer 120 C 140 C Type / conc. % 0 0.05 0.2 0.8 0 0.05 0.2 0.8 A 670 590 800 920 135* 150 180 180 B 880** 880 880 > 880 265 ** 320 320 280 C 670* 710 710 - 130* 130 130 D 880** 680 740 680 265** 260 230 210 * Copolymer I ** Copolymer II

Claims (10)

1. CLAIMS 1. A stabilized polymer composition comprising an alternating copolymer of carbon monoxide and at least one ethylenically unsaturated compound, and at least a stabilizing quantity of a diphenylamine of which at least one of the phenyl groups carries an alkoxy substituent.
2. 2. A composition as claimed in claim 1, wherein the alkoxy substituent is a C1-6 alkoxy group.
3. 3. A composition as claimed in claim 2, wherein the C16 alkoxy group is a methoxy group.
4. 4. A composition as claimed in any one of claims 1-3, wherein the alkoxy substituent occupies the 3 or 4 position on the phenyl rings.
5. 5. A composition as claimed in any one of the claims 1-4, wherein both phenyl groups are alkoxy-substituted.
6. 6. A composition as claimed in claim 5, wherein both alkoxysubstituted phenyl groups are the same.
7. 7. A composition as claimed in any one of claims 1-6, wherein the amount of stabilizer is in the range of from 0.03 to 5.0 %m on polymer.
8. 8. A composition as claimed in any one of claims 1-7, wherein the polymer is a copolymer of ethylene and carbon monoxide.
9. 9. A composition as claimed in any one of claims 1-7, wherein the polymer is a terpolymer of ethylene, propylene and carbon monoxide.
10. 10. A composition as claimed in claim 1, substantially as described in the example.